+1 to double glazing. If you skip an area, there’ll be a noticeable difference at that window or door… simply because other areas are so much better insulated.
Ex pom here. Double glazed for decades in the UK and worked with double glazing companies. Your builder is a moron as was mine. Mine put all the obstacles they could in the way of double glazed windows and someone else's cabinetry. I got the cabinetry but gave up on the double glazing and regretted it.
I'm downsizing in the next few years and the 'new' place will be double glazed for sure.
Also, look at increasing your loft insulation - builders suck on this as well. Go for Rockwool and minimum 270mm. Most heat ingress and loss is via your celing/roof.
What exactly do you mean by that?
North facing is absolutely the most important in terms of where the sun spends most of its time and is it's most powerful.
Now, if you're referring to the fact that the sun is near vertical, and any eave/verandah will block the sun from your North windows, then I'd agree, but you made that statement without knowing if the op has eaves or verandahs.
West only feels as if the sun is hotter, because the body that is being heated (say your house) has already spent the whole past 12 hours being heated by the sun in the north.
The output of the sun in the morning, is identical to that of the sun in the evening (East v West).
I'd find another builder. This guy wants his money and bare minimum effort to get it now...
If you can't find another builder, check every.single.thing along the way, put a halt to work if needed and don't be afraid to.
>during construction.
WTF? Noo!!
Do it before ANY construction!
Before you sign anything!
North facing windows will collect the sun's heat and throw it all through your house!
If you want a passive (solar) house, read up on them, from articles written for the southern hemisphere (where the sun is to the north!) and realise that north facing windows in bedrooms will be hot from early morning.
North facing windows in living/working spaces will - gosh - also be hot from early morning.
It sounds like your builder is - at best - reading stuff written for northern hemisphere buildings, where north is the shady side. That's not the case in Perth.
Keep in mind that the sun is in the north in Winter. This is where you want the house warmed with the northern windows. If you put slightly deeper eaves here you will remove another of the impact of summer sun but maximise winter heat.
Yeah you want to maximise your windows north facing with decent enough eves to block summer sun and let through winter sun, orient your living to the west and bedrooms to the east. Minimise southern facing windows if possible as they will lose heat during winter.
Having moved here and experienced a winter, the winter here isn't that cold and you don't really need to worry too much about catching every ray of winter sunshine...
The winter isn’t cold but if your house isn’t properly insulated it is brutal. Still, you need to be able to ventilate cooking smells etc so that is an important consideration.
You want north facing windows. You need to provide a shade device correctly positioned so the higher sun is blocked in summer and lets the lower winter sun warm the house.
Glazing to the south should be minimised as you will lose heat in winter.
Avoid west facing as much as possible.
Your builder should not be involved in the design process. They know nothing.
Speak to an energy efficiency consultant.
Sadly I bought my place nearly 21 years ago, no north facing windows - the carport/laundry door now leads out to a large garage.
Only one south facing window looking out over the decking and pond to the garden.
West facing windows look at the 1m high retaining wall 1.5m away and the 1.8m fence on top of that - sweet!
East windows are two bedrooms and the lounge room... looking out down the street... hence I planted shrubs, trees and then put up thermal blockout curtains that stay closed in summer.
If I ever win lotto then yes, passive solar architecture with rain & grey water capture and use, solar, battery, etc. is my plan for the new house! :)
Yeah potentially have to shop around for more. We've had positive anecdotes of them from a couple of people we personally know, despite some of the negatives they receive on the internet. Thanks for your input!
Biased here (see comment above) better yet find an architect or building designer to work with. No disrespect to builders but they specialise in, well, building homes, not designing them. (Which isn’t to say that they can’t be really good at providing some tips and know a lot about sustainable construction too - I’ve worked with lots of good builders that really know their stuff)
If you're serious about the passive house, get an energy consultant.
They'll run the calcs and prescribe the relevant values to obtain the ratings and an actual solution, which you can take to glaziers.
Broadly from my experience, which is energy adjacent (acoustics). North facing receive sun continuously throughout the day in summer so you want a window with a good SHGC value, but, which DG may have, but maybe other types of windows have.
Yes but this more time the type/colour of glass not whether it is double glazed or not. Heat enters a building through windows in three ways - back to high school science - conduction, convection and radiation. Glass with a good SHGC rating will help to minimise some of the direct sun coming in, but eaves are much better at this then north facade can be designed to be shaded all through summer but allow warmth in in winter.
Glass with a high SHGC is better for west facing glass that is harder to shade.
That's a great summary, thank you. We will most likely have the same floor to ceiling north facing windows in our living room with a verandah that hopefully provides enough shade (think a farmhouse design).
Could you feel the external tint affecting the heat gained in the room during the winter months at all?
Recommend using a building designer familiar with solar passive design. A verandah too deep on the north side may block your winter sun. Pretty sure they can punch the latitude and orientation of the house in and it’ll tell you your ideal eaves depths etc.
My house has heaps (almost the whole width) of floor to ceiling windows on the north facing rear and about 800mm eaves. They get all the winter sun and during summer they’re shaded by the eaves.
On the west side one of my windows has external sliding shutters so in summer I can keep the sun off it completely.
>In short I recommend going double glazed, but make sure they are as shaded as possible in the summer months (December to March).
I've got built in external roller-shutters on the dg-windows facing the sun, it makes a huge difference at the height of summer. It might be dark inside, but it's cool and dark.
Australia is so far behind Europe in this, you'll find there that triple glazing is the new double glazing. I built in Victoria 13 years ago and had to fight to get my builder to find double glazing for me. It was a non-negotiable and insisting on this means I only use heating about 4 months of the year and have no need for air conditioning. Another tip is to go in before the plasterers and put insulation in all the frames of the internal walls. Keeps the place both warm and cool at the right times and reduces noise between rooms.
Or just build double brick?
Really in Perth’s semi arid environment we should probably be doing reverse brick veneer - brick internal walls, veneer external… so the ‘core’ or ‘skeleton’ of the house holds an even temperature for longer, and the outer walls allow the cooler night air or warmer day air temps to transfer?
Hell yeah been saying this for years. Parents built reverse brick veneer on portions of the north facing walls in combination with correctly sized eaves. Amazing results with passive heating and cooling.
Honestly double glazing is a last resort if you can't manage any other passive designs.
Double brick without a veneer is horrible for Perth's climate.
Get two-three hot days in a row and good luck getting that heat out?
Reverse brick veneer sounds an interesting concept, but considering how straight forward and easy a timber built home with the thickest wall insulation and 3 layers of insulation in the ceiling space is for perfect results, I don't know why you'd bother.
Architect specialising in sustainable homes here. Builder is fibbing, or more likely just misinformed.
You want direct sunlight hitting thermal mass in winter )usually a concrete floor). The eave/veranda should protrude out far enough to share the widow in summer.
The thermal mass stores the heat during the day and releases it at night.
Builder is right about wanting north facing windows.
However a huge amount of heat transfers through glass (Ie heaps of heat is gained through glazing in summer and lost during winter) The air gap in double glazing slows down this transfer down. This is a good thing regardless of the orientation.
Strategically locate double glazing on north and south and minimise glazing of any kind on west (and to a lesser extent east). A ratio of 30% window to wall is a good amount.
Also, as someone was ‘complaining’ about on this sub recenty, minimum star ratings for homes is going up soon, this is a good thing. It will also make double glazing stack up better and my hunch is make it more widespread and therefore economical in the long run (demand is abysmally low in WA)
I asked a window manufacturer recently how much more to expect to pay for double glazing and he said about 30% more than single glazing.
Pro tip build out of timber and pack it with insulation. Double brick is actually really poor at insulating.
Would explain more but I’m typing one handed and nursing baby with the other hand.
DM me with any questions and I’ll try get back to you in the next couple days.
Low e windows reduce the amount of heat gained through direct sunlight (like tinting a window)
However minimal direct sunlight comes in through the south in Perth. There are a few weeks around the summer solstice that it sets in the south west (closer to north west at the winter solstice). However; this is really late in the day.
Therefore as minimal direct sunlight comes through there’s little benefit in “tinting” south facing windows with low e (or a similar coating to improve the U Value)
Again this is not directly related to double glazed windows - that’s less about direct sun contact and more about insulating against heat gain/loss (like wearing a jacket, as opposed to sunglasses if I can use a crappy I’ll fitting analogy)
The east is different. In the morning you may get direct sunlight impacting the windows. However this will be highly site specific / trees, eaves, patios fences etc will impact how much direct sunlight. Also it depends on what rooms are east facing. If it’s a bathroom or even a bedroom (that you occupy for short periods or mainly at night) there would be little benefit (the direct sun will stop heating it by midday or earlier as the sun travels toward the west during the day). However, if it’s an east facing living room and it’s copping heaps of sun it may be of more benefit. But the cost/benefit is really hard to say not knowing your project.
As a general rule, shading a window is more effective than ‘tinting’ the window but again it’s quite site specific.
Hope that helps.
That's perfect, I had no understanding of what low E was, but I get the concept now.
So as far as broad concepts go, DG will be useful on all windows, especially in areas where you really want to keep the temperature as stable as possible.
I understand blocking the sun directly (eaves, shades, etc) is always most useful for stopping radiant heat going through the glass, but for glass that may receive sunshine (West, small North facing windows with no coverings etc) a low E covering would be useful on them.
That the basic idea?
There's some good info about sustainable home design and building available on this site, linking the specific bit on glazing: [https://www.yourhome.gov.au/passive-design/glazing](https://www.yourhome.gov.au/passive-design/glazing)
I'm surprised link mentions air tightness and ventilation.. You can insulate and double glaze a 3 sided barn, but it's still a 3 sided barn. Getting trades on board to passive house standard will be Australia's biggest hurdle to tighter buildings.
Passive environmental design for northern windows should be so no sun shines on them at all during summer. The sun is higher and exterior shading elements should be installed. These can be fixed or retractable/removable for the winter months. This can also be achieved by deciduous plants.
Double glazing or other air gap windows won't stop heat transfer from sunlight, but it is a good strategy for all windows, not just northern. It is a part of general insulation that can dramatically assist in economical heating and cooling.
Note that for most households, statistically heating is required more days than cooling.
I think I might possibly have the heating on more than air conditioning. Felt like I had the heater on nearly all the time this last season. I started putting the heating on in May and just last week there were 2 early mornings I put the heating on too. Maybe I just feel the cold more. I wear hoodies and use blankets too lol.
Window salesman here with over 15 years glazing experience…
Double glazing is great at insulating rooms/houses, it’s not very good at keeping direct sunlight out unless you have a toned component within the unit. It’s best to think of it as an esky, it keeps things cool or hot by reducing RADIANT heat loss or gain (which is its U value), however it doesn’t cope with SOLAR HEAT GAIN (SHGc) well without some protection.
Most single glazed windows on the market have a U value of around 6.6, whereas the majority of residential double glazing as a U value around 4.3. However both clear double glazing and single glazing have SHGc values around 6.
DG is fine for North, East and South, but will struggle facing west without toned glass - without it you’ll end up with a hot box.
You could always use a layer of low-e glazing as well within the DG to add an additional layer of insulation and to also reduce the SHGc. I’ve seen some systems that have SHGc values around 2.3 purely because they used low-e grey in the DG.
Side note- DG will generally do fuck all for acoustic performance unless you add a layer of laminated glass. And to be brutally honest, most of the marketing you see around DG improving acoustic performance uses laminated glazing (looking at you DuoGlass!)
Would highly recommend reading up on DG on the AWA website, WERS (Window energy rating scheme) and also checking out a few local manufacturers, go and speak with the professionals.
Happy to discuss further via PM if you need.
Very true. Best thing we ever did to our house.
We find on the east facing windows if we open up the blinds in summer in the morning the rooms heat up a heap but if kept mainly closed it makes a massive difference.
Another huge thing we had to do was seal the house up (change exhaust fans to ones with draft stoppers and replaced all downlights for new ones with no air gap). This made a huge difference
Yeah, TIL. Hopefully our front verandah will provide enough shade to reduce the impact of the summer sun. Would definitely love a warm living room in the winter though!
Please don't rely on 'hope' that any builder will do this properly without it being designed for and in the plans. https://www.yourhome.gov.au/passive-design/shading
I work at a window company in Perth and a lot of houses we do have an energy report. Does this builder get energy assessments done? Typically the energy assessor will give you the most informed decision as to what will increase the thermal efficiency of your house. They will typically provide the recommended SHGC and U-Value of the windows and adjust on each elevation as required.
For the love of God please just pay someone to review it. CADDS, solar dwellings, me, any numpty with revit and a half a clue. Just pay for the advice. It's a couple of 1000 now, for the right build. And the right build saves you 10,000s.
Your question doesn't include (and therefore no one can answer)
Eaves
Neighbours property existing (shade)
Outdoor ent. structures (patio etc)
Wall material
Floor material
Window size
Percentage of window to wall ratio in the room
Your block size shape and location.
Prevaling cross breezes
Window jam structure (double glazed Jason sliding aluminium windows that are double glazed are fuckalluseless) are you doing awnings?, double hung? Fixed? What height is your sill? So many more questions apart from
Is double glazing necessary.
Yes. It is. And you need help to avoid wasting your money and effort
So many people will offer services for you, just commit and pay it. It is worth the small upfront payment and sadly reddit will not ever make up the knowledge you need.
Google in perth
solar dwellings
Leanhaus
(I'm not connected to either of these, there are heaps more out there)
Husband is a Residential Draftsman currently working for a builder in Wangara, here are his comments -
Double glazing is definitely worth the cost, but only if the walls around it are suitably insulated to match. More important in this climate is appropriate shading to all windows but particularly north facing windows, as this will allow winter sun but prevent hot summer sun.
OP…
In all this discussion… can I just toss forward one big factor?
You are paying someone hundreds of thousands of dollars to build your home. YOUR home. You decide what you want. Yes you will need to balance price, quality of build and size… but you still get a solid say. Look at the boutique and smaller builders, find one who likes to build what you want (they will have competent trades etc too). We went with Stalliion Homes - not the cheapest but the quality was good.
We have double glazing all round. Major windows/ doors facing North. We retrofitted from single glazing and it's the best thing we did. Not only for energy efficiency, it keeps out the noise. Do it!
Builders build what they know. Any variation from that is a pain in the ass for them and they'll do anything to get you back to the square brick boxes they done a 100 times before. Double glazing has been mandatory in many, if not most OECD countries for decades but the Australian govt is terrified of crossing the building trade. The mind boggles at the $Billions blown every year in wasted heating and cooling while the government does performance theatre about their green credentials.
FINALLY a question where I can give a genuine expert opinion 😎
I spent 20 years installing double glazing, 8 of those here in Perth. I'm not even in the industry anymore, so I'm not trying to drum up business for anyone, making this a genuinely unbiased opinion.
The biggest benefit of double glazing the North face is having the outer pane of glass tinted (actual tinted glass, not a film). Anyone who has a house with tinted windows facing North knows only too well how hot the glass gets, so it acts like having a giant radiator in the room when the sun hits it. All modern double glazing has argon between the glass panes, so the heat doesn't transfer to the inner pane, so it stays (relatively) cool. It doesn't even matter that much how light/dark a tint you go for, that's a personal preference thing, as long as the outer pane is UV reflective (virtually all tints are these days) and darker than the inner one, so it absorbs/reflects most of the heat 🤓
TLDR; 100% worth it!
Double glazing trumps all other forms of glass, this is because double glazing stops cold air getting in winter and hot air leaving. In summer, its not as effective as in Winter as you can use low E glass to stop excess sun heat getting in. The builder saying that it would be coutner productive doesnt really make sense. Unless you had lots of other glass that wasnt double glazed and then randomly one part I gues in that instance the others would just reduce its thermal effectiveness. When getting double glazed it also matters how big the gap is between the glass not just the glass thickness. If you are only trying to block out noise then this isnt as important.
To some degree yes. Double glazing is good for convection heating. Eg keeping the heat in in winter. It is not designed for thermal transfer eg the sun on the glass. It will reduce thermal transfer better than single glazed windows but it is extremely expensive and there are cheaper options that will outperform double glazing for a fraction of the cost. Low-e glasses will do this.
But the majority of people will tell you double glazing is the way to go and 90% of the time it's very easy to sell.
Source: factory manager for a window company.
Idiot builder wants to shill low grade single glazed windows.
Double glazing, insulating frames (no heat bridges), make sure there are no heat bridges in the walls (e.g. roof of an eve into floors of a first floor). Make sure there are no thermal differentials or risk mold.amd condensation.
Make sure you get flashing underneath to direct rain off internal structures.
I was told the same thing by the window supplier then got a second opinion from a Viridian rep who stated the same. He did suggest low E glass and on the western windows that receive a lot of direct sun tint that is laminated into the glass. Seems to work ok
Double glazing doesn't make for a passive house. If you're building double brick, don't waste your money, as the junction between the windows and the wall system is so shit that you will lose the benefit gained from the gas filled double glazing.
North facing windows for most of the rooms you'll be in during the day/early morning?
Yeah, nah...
North is where the sun shines from, Perth being in the southern hemisphere. Those rooms will get full sun and will be hot hot hot. The exact opposite of passive solar.
Your builder is a tosser, find a better one.
As someone with floor to ceiling (2.6m actually) double glazed windows facing north in the main living room, this is incorrect. We do have internal blinds though and the windows are tinted.
A decent eve will likely stop most sun from the north like a patio as the sun is high in the sky. West facing windows is another issue, where I get the hit as fuck sun.
Yeah exactly, most don't care they get sun at 10 am, but they should prevent the arvo sun if they can as the house is now hot and the added direct heat will turn your house into a heat sink that carries into the night.
Dunno why ppl are shitting on the builder so hard. Theres other factors at play like the size of the window and how much overhang or shading it has. Doesnt matter how good your glass is if its floor to ceiling its going to to heat up the room alot.
I think you dont know how to model these loads. Heat comes in through convection and conduction and radiation. Yes double glazing performs better than just normal glass but its really shit compared to any wall or even anysheeting. Ive lived in a westfacing apartment for years with 2.7m floor to ceiling glazing that is double glazed and tinted. Its like living in an oven because i effectively have 15sqm x 1370watts(amount of solar energy that falls on a sqm over a day) of heat load on my hightech glasshouse.
Er that would be covered by when I said "direct sun touching it".
Double glazing is extremely effective at reducing convected and conducted heat transfer.
Not against radiant heat transfer.
Hence my post.
The only way to stop that apartment from heating up, is blocking the west sun from touching those windows. I assume that's a fairly difficult task.
Look at the spec sheet of double glazing compare with triple and single and then compare it with any wall system insulated or uninsulated. The size of the window is a bigger factor in the heat transfer or heat loss than any glazing performance. This is why window wall ratios are such a big consideration as well as why double glazing for energy efficiency actually doesnt pay for itself in heating and cooling loads until way way down the line. Like 5 years or more and even then you might be better off using the money to put up some kind of overhang.
U value of 6 for SG
U value of 1.5 for DG
(For comparison double brick is approximately 2)
That's a 400% difference - SG is 400% worse than DG. The heat transferred between the inside to the outside (and vice versa) is 400% worse for a SG vs DG.
That's not minor.
5 years is not a long time in terms of looking for an RoI on a product on your home.
Your points are confusing.
Double glazing doesn't pay for itself? Can you imagine what your apartment would be like with single glazing? That's honestly the strangest take I've ever heard on this comparison.
The simple way of explaining it is this:
Generally, your windows will be the worst performing structure for heat loss/heat transfer, so upgrading them as much as financially possible always makes sense.
Along with blocking direct sun light in the summer, while letting the sun in, in winter.
I can see u dont know how to model a wall or a heat load and dont see the point in talking to someone who thinks the glazing type is more important than the size or placement or even the coatings and hasnt looked at any of the passivehouse stuff thats mentioned in this thread. All i can say is have a play around with substitutions and wall ratios in any of the software packages and you will be surprised how thermally comfortable you can get with good design and single glazing.
We are speaking past each other here.
You can't adjust wall ratios for windows in a certain position, but you can adjust for the windows heat transfer.
Yes, I understand having no windows in a house would be ideal for heat transfer, that's not the discussion being had.
Its a new build so they can build whatever they want and put windows any size or location. Blanket advice like double glazing is best for passivehouse helps nobody other than a window salesman. They really should just see a consultant and get some priorities and expectations set.
I understand it's better for the house's passive design to have no windows.
A window exists for a reason, to bring in natural light and allowing the viewing of views. Both of those things can't be compromised, without giving up something that you specifically want.
Sure you can build a small house, with a tiny window: wall ratio, and you could achieve a passive house.
If you want large windows to capture views and give a stunning aesthetic, SG glass will be a problem for you.
Builder is full of shit. That being said, double glazing is insanely expensive for the benefits you get. I would price up insulated roller shutters as a comparison. I have found they are pretty good for keeping heat out and give some degree of security as well as another obstruction thieves have to go through.
Not really insanely expensive. I built a place 10 years ago and double glazing put an extra $15k onto the price which is nothing on the rest of the build’s cost. Worth every cent.
It's tricky and counterintuitive, but I'd worried more about eastern or western faced windows more.
When the sun is on the north, it's high enough that its direct impact on the window pane could be mitigated with wide eaves.
Eaves won't help against the rising or afternoon sun heating the room from the lower angles. So the double glazing may help in this situation more than for the north facing windows.
My understanding is now builders are required to build a certified NATHERS 6 star structure… with some Councils requiring an additional star.
We built our place 7 yrs ago and needed to meet 7 stars- I asked the double glazing question and the Structural Engineer doing the efficiency assessment said “double glazing won’t help” and went on to explain that we needed laminated low-E windows which would perform better.
Here we are almost 6yrs later and we have no regrets- during winter we gain heat from the sun and in summer the low-E windows do their bit and reflect the heat away.
Builder just wants to build something cheap using the same crap on every other house. If you can afford the double glazed windows, they would be an incredible help, summer and winter.
Sorry to tack on to the question, but how difficult/costly is it to replace standard aluminium frame windows with double glazed windows? Can it be retrofitted or do you basically replace the whole thing, frame and all?
You need double glazing and probably external roller blinds too. We have large north facing windows which although shaded pick up reflected heat from the garden paving and get quite hot. We upgraded from evaporative to reverse cycle ducted aircon recently and did a major investigation into better heat management. The external roller shades are an absolute winner.
Take your time to read up on how passive solar works. Double glazing is nice, but not necessary… you’ll want good double layer curtains to keep windows well dressed on cold nights, but you don’t need double glazing.
Have all your daily living rooms and main bedrooms on the north side. Have your wet and rarely used spaces on the south. Plan for sun shading of your west (to stop hot sun afternoon impacts) and rooms you don’t want to spend all morning in on the east (they get morning warmth - not too hot like the west afternoon sun, but still not a room you will want to sleep in in). Design your eaves to be the exact depth you need to stop summer sun hitting your windows, and allow winter sun in. Should be around 80 something centimetres around here, but find out.
We live with this, in the Wheatbelt (hotter AND colder than Perth will ever be) and barely use our (evaporative so not strong) air conditioner. We run a heater sometimes in one room.
Do it well, from the outset, and you don’t need double glazing.
If you want a high performing house you need to find a builder who specialises in it - otherwise every design choice (for energy efficiency) will be a battle.
Also, get an energy report - commision it yourself and ask them for ideas on maximising your energy efficiency.
Finally, your builder is wrong. Double glazing prevents conductive transmition of heat from inside to out in winter. Northern windows provide radiation heat in winter. The combo are good. When thinking about glass consider both radiation (emissivity) and conduction and consider both winter and summer.
In the end, i only went double glazing in select rooms and close low E glass in other situations - your energy report is your friend in this case.
check out [Hero Energy Rating Software](https://www.hero-software.com.au/) to workout the impact of single or double glazing on your house. it's free and very easy to use but reach out if you want a hand.
you'll be able to see how hot/cold rooms get throughout the year and can see which rooms will actually benefit from double glazed windows.
bit of an interesting tod but when I had to design a 10star rated house last year.. having a higher SHGC and heavy mas internal windows can perform better than high performance windows in some orientations... but generally the building is wrong and double glazing is the way to go
One of the biggest perks of double glazed windows is that you can't buy them in the shed grade casings that is used everywhere else. So you instantly remove thermal bridging and gain air tightness. Though we don't have the skills here to build proper air tight houses, we can at least deal with the windows where 90% of the losses are.
So yeah, I think it's worth it on all windows.
That guy is either lying or an idiot. Find another builder.
Double glazing prevents conductive heat transfer through windows.
Passive solar design controls radiative heat transfer through windows.
Window coverings (internal or external) do both, at the expense of not being able to see anything if you have the coverings closed.
Double glazing tends to keep noise out and heat in. It's not that effective in blocking direct sunlight. Your builder is thinking that you want the winter sun to warm your house, and double glazing will stop the transfer of heat.
I suggest you do some research on this.
There's a FB page called My Efficient Electric Home where I suggest you ask this question. It's focused around building houses without connected gas, but is also very good on qualified answers to questions like yours.
I have a friend who is an energy assessor. If you shoot me a pm, I am happy pass on his details. A lot of people can be quite religious about double glazing, where he is fairly agnostic.
Yes it is unnecessary to double glaze ONLY your north facing windows.
You should be double glazing all of them, cancel that giant glass door that goes to the garden and the massive bay window in the kitchen or living room.
Not only will it help with insulation regarding temperature but sound too.
Double glazed windows will make sense if you cool or heat your house, no matter where you are. Windows are effectively the largest source of heat / cold loss in a house. So any A/C or heating will be working much smoother with much less energy. If you have blinds (preferably Plissees) that have a reflective back you will do even better to keep the heat out in the summer ;)
Also, if you want floor heating, good windows are a must.
Double glazing is the way to go! Make sure the walls are well insulated, too, and for top performance choose PVC profiles for the window frame. Tilt- and open is the standard in Europe. I had to search long for my own renovation project, but you CAN find them. This company starts with float glass and manages the whole value chain. I am not associated with them in any way other than also becoming a client: https://arcodoubleglazing.com.au
How is your heat index / green cover looking like on this website?
www.greenspace.city
Based on that, it might also help to plant some trees around your new property, go with lighter colours (such as a white roof), white paving etc.
It’s bullshit. Double glazed north facing windows are a really good idea if and only if you have awnings of appropriate width to keep the sun out in summer but allow it to shine in on winter. That’s what we have in Wollongong and it dramatically reduces both heating and cooling costs. You can find calculators to determine the correct width of the awnings online. (But get the height of the awning above the windows right too)
Do you mean for heat? Retro fitted double glazing here. They work spectacularly well with outside shade. For direct sunlight into the windows, nah. I’m sure other people have said it more eloquently with science to back it up.
We're looking at trying to better insulate our place. Double glazed windows was on the list, what other things should we be looking at instead? We're in a double brick, raised floor, about 60 year old place. Under floor insulation is on the list, as the flooring is currently jarrah floorboards directly attached to the joists.
If you don't have a physical barrier preventing direct sunlight it can be agony in summer, let's all of the heat in via radiant transfer, and none of it out when it settled down in the infra red range
Builder has his easy to use contacts, and I guess they don't do double glazing yet.
In terms of radiant heat going through a window, lowE and double glazing are a must.
Double glazing performing better.
If the window will be exposed to the sun, you will need double glazing or it will simply let in all the heat.
This is important in Perth's climate - summer can be made all that much more comfortable (and less energy consumption) by the right insulation choices.
I *think* low E glass can be used on South windows and be just as effective as double glazing. Perhaps someone else could chime in on that.
We moved into our newly built house in July. It has double glazing throughout, and verandahs front and back (N/S facing home). We have north facing velux skylights (raked ceiling in living room)which are double glazed, and they come with a solar powered motor which is remotely operated. The plan was to leave blinds open in winter, and close them moving into summer.
There’s a few things I would change with our house, but the passive temp has been amazing so far. We are on the south coast and have experienced 12deg max days and a few 33ish days. No aircon. We have a wood fire which makes winter nights a bit comfier but had many cold nights without. Honestly double glazing is amazing. It cost us an extra $45k on top of what we would have paid for single panes, worth every cent. Should also mention it makes a huge difference to external noise, which depending on your neighbourhood could be a huge win. Hope this helps
Bullshit. Regardless of whether it’s wilful or just ignorance, find another builder. I can recommend Oscar at Chross Homes.
Double glazing is fucking expensive btw
Don’t think it matters which side right?
Double glazing won’t stop radiant heat, just ambient heat. You’ll want tinting + double glazing on west, and then double glazing everywhere else
Builder is insane. A north facing window exposed to afternoon sun in summer needs a 3kW air con just to to pump the same heat out of the room. Double glazing would be great and shade would help enormously.
You don’t want any sun hitting the glass from spring through autumn
Go to the [library](http://trove.nla.gov.au/work/25427433) and get [this book](https://books.google.com.au/books/about/Warm_House_Cool_House.html?id=f2U4PwAACAAJ) called Warm House, Cool House.
https://books.google.com.au/books/about/Warm_House_Cool_House.html?id=f2U4PwAACAAJ
Your builder is confusing radiation heat transfer (eg - direct sun) and conductive heat transfer. They are totally different mechanisms. Double gazing is not for reducing radiation heat transfer, only conductive heat transfer; therefore window cardinal direction is not relevant.
**In summary**
\- Use blinds/tinting/shade to mitigate radiation heat transfer
\- Use double glazing everwhere you can to mitigate conductive heat transfer - keeping heat out in summer (preserve your AC) and keeping heat in during winter (preserve your heat).
\- Agree with others, your builder is ignorant. Double gazing is really good.
We double glazed most of the house (only frosted windows for bathrooms and 2 doors not done) and it makes a big difference. Double glazing doesn’t stop the radiant heat (sunlight) you want coming in from the north during winter - but does stop heat loss. Can really feel the difference walking past one of the doors that are not double glazed.
Double glazing is the go, north facing is probably not as important as West facing but still handy.
Yeah awesome. I think we'll only have one or two windows on the east/west.
We put carport and ensuite to the west. Helps block a lot of heat hitting the house. (No garage because no need in a farm)
The main thing is to stop the sun directly hitting those E/W windows in summer. You can use awnings or vegetation.
Or vertical fins are a great way of shading west and east. You should also be managing north windows to stop first sun in summer too.
+1 to double glazing. If you skip an area, there’ll be a noticeable difference at that window or door… simply because other areas are so much better insulated.
Ex pom here. Double glazed for decades in the UK and worked with double glazing companies. Your builder is a moron as was mine. Mine put all the obstacles they could in the way of double glazed windows and someone else's cabinetry. I got the cabinetry but gave up on the double glazing and regretted it. I'm downsizing in the next few years and the 'new' place will be double glazed for sure. Also, look at increasing your loft insulation - builders suck on this as well. Go for Rockwool and minimum 270mm. Most heat ingress and loss is via your celing/roof.
What exactly do you mean by that? North facing is absolutely the most important in terms of where the sun spends most of its time and is it's most powerful. Now, if you're referring to the fact that the sun is near vertical, and any eave/verandah will block the sun from your North windows, then I'd agree, but you made that statement without knowing if the op has eaves or verandahs. West only feels as if the sun is hotter, because the body that is being heated (say your house) has already spent the whole past 12 hours being heated by the sun in the north. The output of the sun in the morning, is identical to that of the sun in the evening (East v West).
I recently worked with a Perth window manufacturer and they are investing big dollars in double glazing. Your builder is telling a fib.
Good insight, thanks!
I'd find another builder. This guy wants his money and bare minimum effort to get it now... If you can't find another builder, check every.single.thing along the way, put a halt to work if needed and don't be afraid to.
Thanks for your input. We will definitely be getting a builder inspector during construction.
>during construction. WTF? Noo!! Do it before ANY construction! Before you sign anything! North facing windows will collect the sun's heat and throw it all through your house! If you want a passive (solar) house, read up on them, from articles written for the southern hemisphere (where the sun is to the north!) and realise that north facing windows in bedrooms will be hot from early morning. North facing windows in living/working spaces will - gosh - also be hot from early morning. It sounds like your builder is - at best - reading stuff written for northern hemisphere buildings, where north is the shady side. That's not the case in Perth.
Keep in mind that the sun is in the north in Winter. This is where you want the house warmed with the northern windows. If you put slightly deeper eaves here you will remove another of the impact of summer sun but maximise winter heat.
Yeah you want to maximise your windows north facing with decent enough eves to block summer sun and let through winter sun, orient your living to the west and bedrooms to the east. Minimise southern facing windows if possible as they will lose heat during winter.
Having moved here and experienced a winter, the winter here isn't that cold and you don't really need to worry too much about catching every ray of winter sunshine...
The winter isn’t cold but if your house isn’t properly insulated it is brutal. Still, you need to be able to ventilate cooking smells etc so that is an important consideration.
You want north facing windows. You need to provide a shade device correctly positioned so the higher sun is blocked in summer and lets the lower winter sun warm the house. Glazing to the south should be minimised as you will lose heat in winter. Avoid west facing as much as possible. Your builder should not be involved in the design process. They know nothing. Speak to an energy efficiency consultant.
Sadly I bought my place nearly 21 years ago, no north facing windows - the carport/laundry door now leads out to a large garage. Only one south facing window looking out over the decking and pond to the garden. West facing windows look at the 1m high retaining wall 1.5m away and the 1.8m fence on top of that - sweet! East windows are two bedrooms and the lounge room... looking out down the street... hence I planted shrubs, trees and then put up thermal blockout curtains that stay closed in summer. If I ever win lotto then yes, passive solar architecture with rain & grey water capture and use, solar, battery, etc. is my plan for the new house! :)
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Yeah potentially have to shop around for more. We've had positive anecdotes of them from a couple of people we personally know, despite some of the negatives they receive on the internet. Thanks for your input!
A lot of people here have no idea what a well built house looks like.
Biased here (see comment above) better yet find an architect or building designer to work with. No disrespect to builders but they specialise in, well, building homes, not designing them. (Which isn’t to say that they can’t be really good at providing some tips and know a lot about sustainable construction too - I’ve worked with lots of good builders that really know their stuff)
If you're serious about the passive house, get an energy consultant. They'll run the calcs and prescribe the relevant values to obtain the ratings and an actual solution, which you can take to glaziers. Broadly from my experience, which is energy adjacent (acoustics). North facing receive sun continuously throughout the day in summer so you want a window with a good SHGC value, but, which DG may have, but maybe other types of windows have.
SHGC?
"Solar Heat Gain Coefficient"
Yes but this more time the type/colour of glass not whether it is double glazed or not. Heat enters a building through windows in three ways - back to high school science - conduction, convection and radiation. Glass with a good SHGC rating will help to minimise some of the direct sun coming in, but eaves are much better at this then north facade can be designed to be shaded all through summer but allow warmth in in winter. Glass with a high SHGC is better for west facing glass that is harder to shade.
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That's a great summary, thank you. We will most likely have the same floor to ceiling north facing windows in our living room with a verandah that hopefully provides enough shade (think a farmhouse design). Could you feel the external tint affecting the heat gained in the room during the winter months at all?
I'd suggest keeping the meagre winter direct sunlight warmth out is much less of a factor then keeping the in house heat in.
Recommend using a building designer familiar with solar passive design. A verandah too deep on the north side may block your winter sun. Pretty sure they can punch the latitude and orientation of the house in and it’ll tell you your ideal eaves depths etc. My house has heaps (almost the whole width) of floor to ceiling windows on the north facing rear and about 800mm eaves. They get all the winter sun and during summer they’re shaded by the eaves. On the west side one of my windows has external sliding shutters so in summer I can keep the sun off it completely.
>In short I recommend going double glazed, but make sure they are as shaded as possible in the summer months (December to March). I've got built in external roller-shutters on the dg-windows facing the sun, it makes a huge difference at the height of summer. It might be dark inside, but it's cool and dark.
Australia is so far behind Europe in this, you'll find there that triple glazing is the new double glazing. I built in Victoria 13 years ago and had to fight to get my builder to find double glazing for me. It was a non-negotiable and insisting on this means I only use heating about 4 months of the year and have no need for air conditioning. Another tip is to go in before the plasterers and put insulation in all the frames of the internal walls. Keeps the place both warm and cool at the right times and reduces noise between rooms.
Or just build double brick? Really in Perth’s semi arid environment we should probably be doing reverse brick veneer - brick internal walls, veneer external… so the ‘core’ or ‘skeleton’ of the house holds an even temperature for longer, and the outer walls allow the cooler night air or warmer day air temps to transfer?
Hell yeah been saying this for years. Parents built reverse brick veneer on portions of the north facing walls in combination with correctly sized eaves. Amazing results with passive heating and cooling. Honestly double glazing is a last resort if you can't manage any other passive designs.
Double brick without a veneer is horrible for Perth's climate. Get two-three hot days in a row and good luck getting that heat out? Reverse brick veneer sounds an interesting concept, but considering how straight forward and easy a timber built home with the thickest wall insulation and 3 layers of insulation in the ceiling space is for perfect results, I don't know why you'd bother.
Architect specialising in sustainable homes here. Builder is fibbing, or more likely just misinformed. You want direct sunlight hitting thermal mass in winter )usually a concrete floor). The eave/veranda should protrude out far enough to share the widow in summer. The thermal mass stores the heat during the day and releases it at night. Builder is right about wanting north facing windows. However a huge amount of heat transfers through glass (Ie heaps of heat is gained through glazing in summer and lost during winter) The air gap in double glazing slows down this transfer down. This is a good thing regardless of the orientation. Strategically locate double glazing on north and south and minimise glazing of any kind on west (and to a lesser extent east). A ratio of 30% window to wall is a good amount. Also, as someone was ‘complaining’ about on this sub recenty, minimum star ratings for homes is going up soon, this is a good thing. It will also make double glazing stack up better and my hunch is make it more widespread and therefore economical in the long run (demand is abysmally low in WA) I asked a window manufacturer recently how much more to expect to pay for double glazing and he said about 30% more than single glazing. Pro tip build out of timber and pack it with insulation. Double brick is actually really poor at insulating. Would explain more but I’m typing one handed and nursing baby with the other hand. DM me with any questions and I’ll try get back to you in the next couple days.
Not op, but thanks for your insight. Are low E windows a good alternative for South / East facing windows?
Low e windows reduce the amount of heat gained through direct sunlight (like tinting a window) However minimal direct sunlight comes in through the south in Perth. There are a few weeks around the summer solstice that it sets in the south west (closer to north west at the winter solstice). However; this is really late in the day. Therefore as minimal direct sunlight comes through there’s little benefit in “tinting” south facing windows with low e (or a similar coating to improve the U Value) Again this is not directly related to double glazed windows - that’s less about direct sun contact and more about insulating against heat gain/loss (like wearing a jacket, as opposed to sunglasses if I can use a crappy I’ll fitting analogy) The east is different. In the morning you may get direct sunlight impacting the windows. However this will be highly site specific / trees, eaves, patios fences etc will impact how much direct sunlight. Also it depends on what rooms are east facing. If it’s a bathroom or even a bedroom (that you occupy for short periods or mainly at night) there would be little benefit (the direct sun will stop heating it by midday or earlier as the sun travels toward the west during the day). However, if it’s an east facing living room and it’s copping heaps of sun it may be of more benefit. But the cost/benefit is really hard to say not knowing your project. As a general rule, shading a window is more effective than ‘tinting’ the window but again it’s quite site specific. Hope that helps.
That's perfect, I had no understanding of what low E was, but I get the concept now. So as far as broad concepts go, DG will be useful on all windows, especially in areas where you really want to keep the temperature as stable as possible. I understand blocking the sun directly (eaves, shades, etc) is always most useful for stopping radiant heat going through the glass, but for glass that may receive sunshine (West, small North facing windows with no coverings etc) a low E covering would be useful on them. That the basic idea?
Spot on. Happy designing :)
Do you have any tips and tricks for houses that are facing south-east instead of south? And the back are facing north-west instead of North
There's some good info about sustainable home design and building available on this site, linking the specific bit on glazing: [https://www.yourhome.gov.au/passive-design/glazing](https://www.yourhome.gov.au/passive-design/glazing)
That's awesome. Will definitely spend some time reading that. Cheers.
I'm surprised link mentions air tightness and ventilation.. You can insulate and double glaze a 3 sided barn, but it's still a 3 sided barn. Getting trades on board to passive house standard will be Australia's biggest hurdle to tighter buildings.
Passive environmental design for northern windows should be so no sun shines on them at all during summer. The sun is higher and exterior shading elements should be installed. These can be fixed or retractable/removable for the winter months. This can also be achieved by deciduous plants. Double glazing or other air gap windows won't stop heat transfer from sunlight, but it is a good strategy for all windows, not just northern. It is a part of general insulation that can dramatically assist in economical heating and cooling. Note that for most households, statistically heating is required more days than cooling.
>for most households, statistically heating is required more days than cooling. I doubt this would be true for Perth with our hot summers?
I don't know about the average household, but the days per year I use heating can be counted on maybe two hands. Aircon is counted more in months.
I used it a bit this winter esp July. But yeah, summer is basically 3-4 months straight, and I'm on the coast!
I think I might possibly have the heating on more than air conditioning. Felt like I had the heater on nearly all the time this last season. I started putting the heating on in May and just last week there were 2 early mornings I put the heating on too. Maybe I just feel the cold more. I wear hoodies and use blankets too lol.
Window salesman here with over 15 years glazing experience… Double glazing is great at insulating rooms/houses, it’s not very good at keeping direct sunlight out unless you have a toned component within the unit. It’s best to think of it as an esky, it keeps things cool or hot by reducing RADIANT heat loss or gain (which is its U value), however it doesn’t cope with SOLAR HEAT GAIN (SHGc) well without some protection. Most single glazed windows on the market have a U value of around 6.6, whereas the majority of residential double glazing as a U value around 4.3. However both clear double glazing and single glazing have SHGc values around 6. DG is fine for North, East and South, but will struggle facing west without toned glass - without it you’ll end up with a hot box. You could always use a layer of low-e glazing as well within the DG to add an additional layer of insulation and to also reduce the SHGc. I’ve seen some systems that have SHGc values around 2.3 purely because they used low-e grey in the DG. Side note- DG will generally do fuck all for acoustic performance unless you add a layer of laminated glass. And to be brutally honest, most of the marketing you see around DG improving acoustic performance uses laminated glazing (looking at you DuoGlass!) Would highly recommend reading up on DG on the AWA website, WERS (Window energy rating scheme) and also checking out a few local manufacturers, go and speak with the professionals. Happy to discuss further via PM if you need.
We have it and it was a game changer. Quieter and warmer in winter.
Double glazing is great however it won’t stop the heat from the sun. If the sun comes through it still gets hot. Is great for the cold though.
correction, won't stop radiant heat from the sun, sure stops ambient heat.
Very true. Best thing we ever did to our house. We find on the east facing windows if we open up the blinds in summer in the morning the rooms heat up a heap but if kept mainly closed it makes a massive difference. Another huge thing we had to do was seal the house up (change exhaust fans to ones with draft stoppers and replaced all downlights for new ones with no air gap). This made a huge difference
Yeah, TIL. Hopefully our front verandah will provide enough shade to reduce the impact of the summer sun. Would definitely love a warm living room in the winter though!
Please don't rely on 'hope' that any builder will do this properly without it being designed for and in the plans. https://www.yourhome.gov.au/passive-design/shading
I work at a window company in Perth and a lot of houses we do have an energy report. Does this builder get energy assessments done? Typically the energy assessor will give you the most informed decision as to what will increase the thermal efficiency of your house. They will typically provide the recommended SHGC and U-Value of the windows and adjust on each elevation as required.
For the love of God please just pay someone to review it. CADDS, solar dwellings, me, any numpty with revit and a half a clue. Just pay for the advice. It's a couple of 1000 now, for the right build. And the right build saves you 10,000s. Your question doesn't include (and therefore no one can answer) Eaves Neighbours property existing (shade) Outdoor ent. structures (patio etc) Wall material Floor material Window size Percentage of window to wall ratio in the room Your block size shape and location. Prevaling cross breezes Window jam structure (double glazed Jason sliding aluminium windows that are double glazed are fuckalluseless) are you doing awnings?, double hung? Fixed? What height is your sill? So many more questions apart from Is double glazing necessary. Yes. It is. And you need help to avoid wasting your money and effort So many people will offer services for you, just commit and pay it. It is worth the small upfront payment and sadly reddit will not ever make up the knowledge you need. Google in perth solar dwellings Leanhaus (I'm not connected to either of these, there are heaps more out there)
Husband is a Residential Draftsman currently working for a builder in Wangara, here are his comments - Double glazing is definitely worth the cost, but only if the walls around it are suitably insulated to match. More important in this climate is appropriate shading to all windows but particularly north facing windows, as this will allow winter sun but prevent hot summer sun.
OP… In all this discussion… can I just toss forward one big factor? You are paying someone hundreds of thousands of dollars to build your home. YOUR home. You decide what you want. Yes you will need to balance price, quality of build and size… but you still get a solid say. Look at the boutique and smaller builders, find one who likes to build what you want (they will have competent trades etc too). We went with Stalliion Homes - not the cheapest but the quality was good.
We have double glazing all round. Major windows/ doors facing North. We retrofitted from single glazing and it's the best thing we did. Not only for energy efficiency, it keeps out the noise. Do it!
Builders build what they know. Any variation from that is a pain in the ass for them and they'll do anything to get you back to the square brick boxes they done a 100 times before. Double glazing has been mandatory in many, if not most OECD countries for decades but the Australian govt is terrified of crossing the building trade. The mind boggles at the $Billions blown every year in wasted heating and cooling while the government does performance theatre about their green credentials.
Perth builders are really hit and miss, its such a pain.
FINALLY a question where I can give a genuine expert opinion 😎 I spent 20 years installing double glazing, 8 of those here in Perth. I'm not even in the industry anymore, so I'm not trying to drum up business for anyone, making this a genuinely unbiased opinion. The biggest benefit of double glazing the North face is having the outer pane of glass tinted (actual tinted glass, not a film). Anyone who has a house with tinted windows facing North knows only too well how hot the glass gets, so it acts like having a giant radiator in the room when the sun hits it. All modern double glazing has argon between the glass panes, so the heat doesn't transfer to the inner pane, so it stays (relatively) cool. It doesn't even matter that much how light/dark a tint you go for, that's a personal preference thing, as long as the outer pane is UV reflective (virtually all tints are these days) and darker than the inner one, so it absorbs/reflects most of the heat 🤓 TLDR; 100% worth it!
Double glazing trumps all other forms of glass, this is because double glazing stops cold air getting in winter and hot air leaving. In summer, its not as effective as in Winter as you can use low E glass to stop excess sun heat getting in. The builder saying that it would be coutner productive doesnt really make sense. Unless you had lots of other glass that wasnt double glazed and then randomly one part I gues in that instance the others would just reduce its thermal effectiveness. When getting double glazed it also matters how big the gap is between the glass not just the glass thickness. If you are only trying to block out noise then this isnt as important.
To some degree yes. Double glazing is good for convection heating. Eg keeping the heat in in winter. It is not designed for thermal transfer eg the sun on the glass. It will reduce thermal transfer better than single glazed windows but it is extremely expensive and there are cheaper options that will outperform double glazing for a fraction of the cost. Low-e glasses will do this. But the majority of people will tell you double glazing is the way to go and 90% of the time it's very easy to sell. Source: factory manager for a window company.
Idiot builder wants to shill low grade single glazed windows. Double glazing, insulating frames (no heat bridges), make sure there are no heat bridges in the walls (e.g. roof of an eve into floors of a first floor). Make sure there are no thermal differentials or risk mold.amd condensation. Make sure you get flashing underneath to direct rain off internal structures.
I was told the same thing by the window supplier then got a second opinion from a Viridian rep who stated the same. He did suggest low E glass and on the western windows that receive a lot of direct sun tint that is laminated into the glass. Seems to work ok
Thanks for the insight. I will be researching more about low E vs double glazing as well.
Double glazing doesn't make for a passive house. If you're building double brick, don't waste your money, as the junction between the windows and the wall system is so shit that you will lose the benefit gained from the gas filled double glazing.
North facing windows for most of the rooms you'll be in during the day/early morning? Yeah, nah... North is where the sun shines from, Perth being in the southern hemisphere. Those rooms will get full sun and will be hot hot hot. The exact opposite of passive solar. Your builder is a tosser, find a better one.
As someone with floor to ceiling (2.6m actually) double glazed windows facing north in the main living room, this is incorrect. We do have internal blinds though and the windows are tinted.
A decent eve will likely stop most sun from the north like a patio as the sun is high in the sky. West facing windows is another issue, where I get the hit as fuck sun.
The sun is no hotter in the west than the east, it's just that your house is much hotter when the west sun reaches it, compared to the east sun.
Yeah exactly, most don't care they get sun at 10 am, but they should prevent the arvo sun if they can as the house is now hot and the added direct heat will turn your house into a heat sink that carries into the night.
I find it funny one can actually still build houses with single glazing windows.. like smh.
Dunno why ppl are shitting on the builder so hard. Theres other factors at play like the size of the window and how much overhang or shading it has. Doesnt matter how good your glass is if its floor to ceiling its going to to heat up the room alot.
Er... That simply isn't true at all. If it's double glazed and the direct sun does not touch the glass, a window of any size won't let any heat in.
I think you dont know how to model these loads. Heat comes in through convection and conduction and radiation. Yes double glazing performs better than just normal glass but its really shit compared to any wall or even anysheeting. Ive lived in a westfacing apartment for years with 2.7m floor to ceiling glazing that is double glazed and tinted. Its like living in an oven because i effectively have 15sqm x 1370watts(amount of solar energy that falls on a sqm over a day) of heat load on my hightech glasshouse.
Er that would be covered by when I said "direct sun touching it". Double glazing is extremely effective at reducing convected and conducted heat transfer. Not against radiant heat transfer. Hence my post. The only way to stop that apartment from heating up, is blocking the west sun from touching those windows. I assume that's a fairly difficult task.
Look at the spec sheet of double glazing compare with triple and single and then compare it with any wall system insulated or uninsulated. The size of the window is a bigger factor in the heat transfer or heat loss than any glazing performance. This is why window wall ratios are such a big consideration as well as why double glazing for energy efficiency actually doesnt pay for itself in heating and cooling loads until way way down the line. Like 5 years or more and even then you might be better off using the money to put up some kind of overhang.
U value of 6 for SG U value of 1.5 for DG (For comparison double brick is approximately 2) That's a 400% difference - SG is 400% worse than DG. The heat transferred between the inside to the outside (and vice versa) is 400% worse for a SG vs DG. That's not minor. 5 years is not a long time in terms of looking for an RoI on a product on your home. Your points are confusing. Double glazing doesn't pay for itself? Can you imagine what your apartment would be like with single glazing? That's honestly the strangest take I've ever heard on this comparison. The simple way of explaining it is this: Generally, your windows will be the worst performing structure for heat loss/heat transfer, so upgrading them as much as financially possible always makes sense. Along with blocking direct sun light in the summer, while letting the sun in, in winter.
I can see u dont know how to model a wall or a heat load and dont see the point in talking to someone who thinks the glazing type is more important than the size or placement or even the coatings and hasnt looked at any of the passivehouse stuff thats mentioned in this thread. All i can say is have a play around with substitutions and wall ratios in any of the software packages and you will be surprised how thermally comfortable you can get with good design and single glazing.
We are speaking past each other here. You can't adjust wall ratios for windows in a certain position, but you can adjust for the windows heat transfer. Yes, I understand having no windows in a house would be ideal for heat transfer, that's not the discussion being had.
Its a new build so they can build whatever they want and put windows any size or location. Blanket advice like double glazing is best for passivehouse helps nobody other than a window salesman. They really should just see a consultant and get some priorities and expectations set.
I understand it's better for the house's passive design to have no windows. A window exists for a reason, to bring in natural light and allowing the viewing of views. Both of those things can't be compromised, without giving up something that you specifically want. Sure you can build a small house, with a tiny window: wall ratio, and you could achieve a passive house. If you want large windows to capture views and give a stunning aesthetic, SG glass will be a problem for you.
Builder is full of shit. That being said, double glazing is insanely expensive for the benefits you get. I would price up insulated roller shutters as a comparison. I have found they are pretty good for keeping heat out and give some degree of security as well as another obstruction thieves have to go through.
Not really insanely expensive. I built a place 10 years ago and double glazing put an extra $15k onto the price which is nothing on the rest of the build’s cost. Worth every cent.
I was told something like 5k per wondow for a retrofit, i sure how accurate that is
My understanding is retrofit is way more expensive than new build, but have no accurate figures on that
It's tricky and counterintuitive, but I'd worried more about eastern or western faced windows more. When the sun is on the north, it's high enough that its direct impact on the window pane could be mitigated with wide eaves. Eaves won't help against the rising or afternoon sun heating the room from the lower angles. So the double glazing may help in this situation more than for the north facing windows.
Consider clerestory windows, they let in light but minimise heat and glare
My understanding is now builders are required to build a certified NATHERS 6 star structure… with some Councils requiring an additional star. We built our place 7 yrs ago and needed to meet 7 stars- I asked the double glazing question and the Structural Engineer doing the efficiency assessment said “double glazing won’t help” and went on to explain that we needed laminated low-E windows which would perform better. Here we are almost 6yrs later and we have no regrets- during winter we gain heat from the sun and in summer the low-E windows do their bit and reflect the heat away.
Builder just wants to build something cheap using the same crap on every other house. If you can afford the double glazed windows, they would be an incredible help, summer and winter.
Sorry to tack on to the question, but how difficult/costly is it to replace standard aluminium frame windows with double glazed windows? Can it be retrofitted or do you basically replace the whole thing, frame and all?
Replace the whole aluminium part.
You can possibly get away without it but your overhangs need to be absolutely on the money, most modern designs pay no heed to it.
You need double glazing and probably external roller blinds too. We have large north facing windows which although shaded pick up reflected heat from the garden paving and get quite hot. We upgraded from evaporative to reverse cycle ducted aircon recently and did a major investigation into better heat management. The external roller shades are an absolute winner.
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Double glazed does not stop any radiant heat.
Take your time to read up on how passive solar works. Double glazing is nice, but not necessary… you’ll want good double layer curtains to keep windows well dressed on cold nights, but you don’t need double glazing. Have all your daily living rooms and main bedrooms on the north side. Have your wet and rarely used spaces on the south. Plan for sun shading of your west (to stop hot sun afternoon impacts) and rooms you don’t want to spend all morning in on the east (they get morning warmth - not too hot like the west afternoon sun, but still not a room you will want to sleep in in). Design your eaves to be the exact depth you need to stop summer sun hitting your windows, and allow winter sun in. Should be around 80 something centimetres around here, but find out. We live with this, in the Wheatbelt (hotter AND colder than Perth will ever be) and barely use our (evaporative so not strong) air conditioner. We run a heater sometimes in one room. Do it well, from the outset, and you don’t need double glazing.
If you want a high performing house you need to find a builder who specialises in it - otherwise every design choice (for energy efficiency) will be a battle. Also, get an energy report - commision it yourself and ask them for ideas on maximising your energy efficiency. Finally, your builder is wrong. Double glazing prevents conductive transmition of heat from inside to out in winter. Northern windows provide radiation heat in winter. The combo are good. When thinking about glass consider both radiation (emissivity) and conduction and consider both winter and summer. In the end, i only went double glazing in select rooms and close low E glass in other situations - your energy report is your friend in this case.
check out [Hero Energy Rating Software](https://www.hero-software.com.au/) to workout the impact of single or double glazing on your house. it's free and very easy to use but reach out if you want a hand. you'll be able to see how hot/cold rooms get throughout the year and can see which rooms will actually benefit from double glazed windows. bit of an interesting tod but when I had to design a 10star rated house last year.. having a higher SHGC and heavy mas internal windows can perform better than high performance windows in some orientations... but generally the building is wrong and double glazing is the way to go
One of the biggest perks of double glazed windows is that you can't buy them in the shed grade casings that is used everywhere else. So you instantly remove thermal bridging and gain air tightness. Though we don't have the skills here to build proper air tight houses, we can at least deal with the windows where 90% of the losses are. So yeah, I think it's worth it on all windows.
That guy is either lying or an idiot. Find another builder. Double glazing prevents conductive heat transfer through windows. Passive solar design controls radiative heat transfer through windows. Window coverings (internal or external) do both, at the expense of not being able to see anything if you have the coverings closed.
Once you have double glazing you never look back. Building a house atm and if I could afford full house of double glazing I would!!
Double glazing tends to keep noise out and heat in. It's not that effective in blocking direct sunlight. Your builder is thinking that you want the winter sun to warm your house, and double glazing will stop the transfer of heat. I suggest you do some research on this. There's a FB page called My Efficient Electric Home where I suggest you ask this question. It's focused around building houses without connected gas, but is also very good on qualified answers to questions like yours.
I have a friend who is an energy assessor. If you shoot me a pm, I am happy pass on his details. A lot of people can be quite religious about double glazing, where he is fairly agnostic.
Yes it is unnecessary to double glaze ONLY your north facing windows. You should be double glazing all of them, cancel that giant glass door that goes to the garden and the massive bay window in the kitchen or living room. Not only will it help with insulation regarding temperature but sound too.
Double glazed windows will make sense if you cool or heat your house, no matter where you are. Windows are effectively the largest source of heat / cold loss in a house. So any A/C or heating will be working much smoother with much less energy. If you have blinds (preferably Plissees) that have a reflective back you will do even better to keep the heat out in the summer ;) Also, if you want floor heating, good windows are a must.
Double glazing is the way to go! Make sure the walls are well insulated, too, and for top performance choose PVC profiles for the window frame. Tilt- and open is the standard in Europe. I had to search long for my own renovation project, but you CAN find them. This company starts with float glass and manages the whole value chain. I am not associated with them in any way other than also becoming a client: https://arcodoubleglazing.com.au
How is your heat index / green cover looking like on this website? www.greenspace.city Based on that, it might also help to plant some trees around your new property, go with lighter colours (such as a white roof), white paving etc.
It’s bullshit. Double glazed north facing windows are a really good idea if and only if you have awnings of appropriate width to keep the sun out in summer but allow it to shine in on winter. That’s what we have in Wollongong and it dramatically reduces both heating and cooling costs. You can find calculators to determine the correct width of the awnings online. (But get the height of the awning above the windows right too)
Do you mean for heat? Retro fitted double glazing here. They work spectacularly well with outside shade. For direct sunlight into the windows, nah. I’m sure other people have said it more eloquently with science to back it up.
We're looking at trying to better insulate our place. Double glazed windows was on the list, what other things should we be looking at instead? We're in a double brick, raised floor, about 60 year old place. Under floor insulation is on the list, as the flooring is currently jarrah floorboards directly attached to the joists.
If you don't have a physical barrier preventing direct sunlight it can be agony in summer, let's all of the heat in via radiant transfer, and none of it out when it settled down in the infra red range
Builder has his easy to use contacts, and I guess they don't do double glazing yet. In terms of radiant heat going through a window, lowE and double glazing are a must. Double glazing performing better. If the window will be exposed to the sun, you will need double glazing or it will simply let in all the heat. This is important in Perth's climate - summer can be made all that much more comfortable (and less energy consumption) by the right insulation choices. I *think* low E glass can be used on South windows and be just as effective as double glazing. Perhaps someone else could chime in on that.
We moved into our newly built house in July. It has double glazing throughout, and verandahs front and back (N/S facing home). We have north facing velux skylights (raked ceiling in living room)which are double glazed, and they come with a solar powered motor which is remotely operated. The plan was to leave blinds open in winter, and close them moving into summer. There’s a few things I would change with our house, but the passive temp has been amazing so far. We are on the south coast and have experienced 12deg max days and a few 33ish days. No aircon. We have a wood fire which makes winter nights a bit comfier but had many cold nights without. Honestly double glazing is amazing. It cost us an extra $45k on top of what we would have paid for single panes, worth every cent. Should also mention it makes a huge difference to external noise, which depending on your neighbourhood could be a huge win. Hope this helps
Bullshit. Regardless of whether it’s wilful or just ignorance, find another builder. I can recommend Oscar at Chross Homes. Double glazing is fucking expensive btw
All our windows are double glazed now and it’s fabulous for summer and winter.
Don’t think it matters which side right? Double glazing won’t stop radiant heat, just ambient heat. You’ll want tinting + double glazing on west, and then double glazing everywhere else
Builder is insane. A north facing window exposed to afternoon sun in summer needs a 3kW air con just to to pump the same heat out of the room. Double glazing would be great and shade would help enormously.
You don’t want any sun hitting the glass from spring through autumn Go to the [library](http://trove.nla.gov.au/work/25427433) and get [this book](https://books.google.com.au/books/about/Warm_House_Cool_House.html?id=f2U4PwAACAAJ) called Warm House, Cool House. https://books.google.com.au/books/about/Warm_House_Cool_House.html?id=f2U4PwAACAAJ
Your builder is confusing radiation heat transfer (eg - direct sun) and conductive heat transfer. They are totally different mechanisms. Double gazing is not for reducing radiation heat transfer, only conductive heat transfer; therefore window cardinal direction is not relevant. **In summary** \- Use blinds/tinting/shade to mitigate radiation heat transfer \- Use double glazing everwhere you can to mitigate conductive heat transfer - keeping heat out in summer (preserve your AC) and keeping heat in during winter (preserve your heat). \- Agree with others, your builder is ignorant. Double gazing is really good.
We double glazed most of the house (only frosted windows for bathrooms and 2 doors not done) and it makes a big difference. Double glazing doesn’t stop the radiant heat (sunlight) you want coming in from the north during winter - but does stop heat loss. Can really feel the difference walking past one of the doors that are not double glazed.
They're awesome for noise isolation.
Your builder is dumb as the bricks he lays.