Loads of different glass out there. Solar control (limits heat into the building) / Low E (Reduces heat loss from the building).
A good Low E soft coat on a typical 16mm 90% Argon filled will give a 1.2 - 1.3 centre point U value - generally .1 less with a Swiss style spacer system, and provides a SC of around 0.6
A solar control glass coating will achieve a similar, maybe higher U value but have a SC of between 0.17 to 0.6. (Not really a requirement on a domestic buildings)
I've leave it down to the specialists but I do have a liking for Pilkington Suncool 50/25 on commercial projects requiring a high degree of solar control.
Energy efficiency and solar protection are different properties, one would surely compromise the other.
Windows should only be considered as part of an overall strategy, I'd probably only concern myself with top performing windows if the rest of my building was super efficient.
You asked about energy efficient windows, I've told you about energy efficient windows.
When Molgrips has a question he doesn't want an answer. He just wants to tell the world he has a question. 🙂
Lol 🙂
Energy efficiency and solar protection are different properties, one would surely compromise the other.
Probably, but both are required (or disirable) properties, aren't they?
Windows should only be considered as part of an overall strategy, I'd probably only concern myself with top performing windows if the rest of my building was super efficient.
Isn't this simply because of the costs involved? If there was a cheap solution available, wouldn't it make sense to start thinking a little differently?
Desirable yes, I have seen both specs used on the same facades though never in the same unit (albeit in my limited experience).
Isn't this simply because of the costs involved? If there was a cheap solution available, wouldn't it make sense to start thinking a little differently?
Was a subjective comment but yes, I wouldn't go spunking a fortune on windows if my building was thermally flawed.
But if they were cheaper then of course I'd consider it 🙂
the frames are the weak link.
upvc frames are hollow plastic. they are not air tight like the glass units and condense internally. wood is a far better frame material but high maintainance. i reckon the ideal would be tripple glazed units housed in wooden frames. but get ready for the bill!
makes me laugh when i pull perfectly good wood windows out to replace with upvc. i think its crap.
But if they were cheaper then of course I'd consider it
Now you've gone all vague on me again. 😆
Cheaper than what? Cheaper than 3G with all the bells and whistles, I'm quite sure that can be done and greater savings potentially.
Good curtains do a fantastic job of keeping the cold out.
Even better make you own 'shutter' from some sort of Kingspan type insulation that fits into the reveals snugly. There is a full on eco-mentalist round the corner who has a similar set up but of course uses sheeps wool that naturally fell off the sheep etc.
Cheaper than what?
Cheaper than they currently are.
I'm not from a commercial background and don't know the specifics, although I am aware that thermally broken composites (for example) are pretty expensive!
Cheaper than they currently are.
You've got me there! 😀
If we follow traditional paths then any improvements in performance are going to push the price up. I recently saw some 3G glass at £360 per m², beautiful as it was.... 😯
There was another example, or it might have been the same one, where the huge glass frontage retro-fitted some shading to combat solar gains.
If we're looking at prices like that, and depending on performance, then I'm confident in saying yes, there is a cheaper alternative.
I'd even say there's room to lower the glazing spec and then add shutters to work to the strengths of both systems and add extra benefits too.
The future is dynamic. 😉
I'd even say there's room to lower the glazing spec and then add shutters to work to the strengths of both systems and add extra benefits too.
Unfortunately shutters appear to be ugly (exposed roller) and expensive, of not ugly and even more expensive (hidden roller). I'd love to have them fitting on at least all the downstairs windows but cost is prohibitive. We lived in Germany when I was (much) younger and I used to love closing the shutters.
Brise soleil can look pretty good on larger facades, although I'm not sure how this might translate to smaller residential buildings.
Normal french-style shutters aren't ugly, are they? People might think you are pretentious though.
the frames are the weak link.
I did wonder about this. I am tempted to squirt some expanding foam in them.
Unfortunately shutters appear to be ugly (exposed roller) and expensive, of not ugly and even more expensive (hidden roller). I'd love to have them fitting on at least all the downstairs windows but cost is prohibitive. We lived in Germany when I was (much) younger and I used to love closing the shutters.
I agree with the ugliness aspect with an external box and guides, but things have moved on a bit. A hidden roller box doesn't have to be any more expensive, I'd reckon that if you're considering upgrading your 2G, you could fit shutter instead for significantly less than the 2G would cost you and I'd suggest with greater benefits and gains. But retro fitting is a bit more complicated and could be considered when upgrading your 2G.
Costwise they're not as expensive as you think, if you know where to go. 😉
Brise soleil is, of course, an alternative as are other shading solutions and would probably work in the UK as the sun is high in the summer and low in the winter, but they don't really prevent heatloss, do they?
A question of preferences, innit?
People might think you are pretentious though.
Let 'em think that as your pocketing the saved cash. 😉
I've been thinking about a new porch on the front as the current one is just an alloy box. Guess this could be made wider to cover the window too so the box was hidden. Hmmm
Any tips in where would be best to go for better prices?
Hi Don,
A couple of links below to the major glass/coating manufacturers (just as examples)
Saint Gobain: [url= http://uk.saint-gobain-glass.com/upload/files/skn144_brochure_internet.pdf ]Coolite SKN 174[/url]
Guardian: [url= http://www.sunguardglass.co.uk/SunguardProducts/ProductsbySeries/SeriesSelector/Results/index.htm?id=11002011&coatingid=5350 ]Sunguard[/url]
Pilks Suncool already discussed up the page
All the major glass manufacturers offer various solar control coatings that also perform the same function as the low E coatings these days, but as with anything, they cost more than a bog standard low E coating. Probably overkill for most domestic house though.
Thanks for that slackman99, it's all very interesting and I'll have to toddle off to look for some prices. A brief read still doesn't convince me that these products are
[url= http://singletrackworld.com/forum/topic/talk-to-me-about-energy-efficient-windows/page/2#post-3750854 ]
[/url]is the best.
That's not having a pop btw.
For me it's a question of understanding a bit more, but the Saint-Gobain features [i]
[/i] which is perfect for the summer but less good in the winter."SGG COOL-LITE SKN 144 II can be
used to improve the energy efficiency
of buildings by considerably reducing
overheating and the need for costly
air conditioning."
And I guess that two of the things that jump out at me about the Guardian glass is a VT of 52% and W/m²K of 1,3.
My point being that while glass is good and there is plenty of technology and muchas advances etc, it shouldn't be considered the best and can be used with other products the complement each other.
As much as I believe what I'm doing is not a suitable solution for everyone, but it is a valid solution for many and should be considered.
nixie, you could do worse than dropping me an email.
Guardian u-value of 1.3 is with an air filled cavity. 1.0 with argon filled. Argon filled is standard in commercial glazing.
1.0 is as low as currently available with an argon filled double glazed unit (as far as i'm aware).
A 6T-16-6T SGG Coolite SKN174II will set you back in the region of £70/sqm plus energy surcharge.
Like for like, Guardian products are cheaper than Saint Gobain and Pilks. Glaverbel/AGC slightly cheaper again.
And which ones do you sell? 😉
I don't sell any. I buy. Used to work for a company owned by Saint Gobain, and still bought Guardian glass as the rates were/are better (for commercial projects)for an equivalent product.
That will explain why you see them as being the best solution. 😉
1.0 is as low as currently available with an argon filled double glazed unit (as far as i'm aware).
Can I make you aware of a double glazed test I've had done taking the value down to 0,81W/m²K, bog standard double glazing of 1,80W/m²K to start with. 😀
I've read through all of this thread in a weird kind of masochistic way.
My contribution; molgrips, get some super thick curtains.
Crikey's right, curtains will work.
[url= http://gentledescent.wordpress.com/2009/03/22/insulating-effect-of-curtains/ ]http://gentledescent.wordpress.com/2009/03/22/insulating-effect-of-curtains/[/url]
Thank you don simon. I always tell the wife and kids that there is little point having the heating on in the winter and having the curtains open. We do have big double glazed bay windows, but it is noticeably warmer when the curtains are closed.
In the summer, when I am on nights, keeping the curtains closed also helps to reduce the heat build up in the room until the late afternoon. I have a southwest facing house which gets roasted in the summer and wind chilled in the winter.
I cannot believe that my life has come to the point where I cannot find anything better to do than discuss curtains, windows and the heat/cold related efficiency thereof...
keeping the curtains closed also helps to reduce the heat build up in the room until the late afternoon.
You should really put them on the outside to maximise the benefit, if you want to go into the minute details, best left for when you have insomnia.
Might make them
a) difficult to draw,
b) a wee bit dirty,
c) add to the neighbours consternation... 😉
Can't have everything, eh? 😆
Don,
How have you taken a 1.8 centre pane dgu and turned it in to a 0.8 centre pane dgu?
An no, windows aren't the most energy efficient way to create an external part to your home. A highly insulated wall would keep more heat in in the winter, more heat out in the summer, but would be a little dark.
There aren't many buildings that don't have some form of glazing in them, so i'd hardly say that I was trying to say windows/glazing are most energy efficient simply because i'm in the industry.
On a side note, draughts take a hell of a lot of heat out of houses. If you have trickle vents on the windows (the small vents above the glass) then these usually lose a lot of heat. Sealing these up can often help keep heat in
My contribution; molgrips, get some super thick curtains.
You can't ahve been reading that closely, I already have thick curtains 🙂
On a side note, draughts take a hell of a lot of heat out of houses. If you have trickle vents on the windows (the small vents above the glass) then these usually lose a lot of heat. Sealing these up can often help keep heat in
Sealing trickle vents can cause a build up of damp and is not recommended.
Blinds installed within the DGU's might be a way of improving the thermal performance of windows, pricey though.
[url= http://kalablinds.files.wordpress.com/2012/03/4-bed-dwelling-jdpwindow.pdf ]Window 1,8W/m²K[/url]
[url= http://kalablinds.files.wordpress.com/2012/03/4-bed-dwelling-jdpwindow-with-blinds.pdf ]Window + 0,81W/m²K[/url]
😉
pricey though.
Not as pricey as you think.
You can't ahve been reading that closely, I already have thick curtains
Now who's not reading closely? 😆
*applauds don simons work and views*
Until you know the (woeful likely) U and psi values and airtightness of existing house (as built, not calculated) it is like whacking an XTR rear mech on a (likely) Halfords £99 special.
That appears to show that you've taken a 1.8 u value window, put it in a cavity with a blind and come up with a lower u-value. The read out doesn't really mean much to me as it doesn't show any of the properties of the window. It appears to be comparing a window unit with a window built into a highly insulated wall?
Interstitial blinds (blinds in the unit) don't improve thermal performance of the unit other than cutting out light (as would a normal much cheaper blind). They do however look swish.
I seem to have veered massively for the OP's original question though.
To sum up, unless you have an ultra well insulated and draught proofed home, changing from a B rated window to an A is unlikely to make any significant/noticeable difference.
Are new bulid houses that bad? We pay £30/mo in gas in the winter, I thought that was ok.
Ok so ideally i'd like to pay far less... I am always thinking about creative solutions to heating the home.
Anyone put solar hot water on a wall rather than a ceiling?
(as would a normal much cheaper blind)
Much cheaper? What are you basing your base price on? And I doubt you either get the same level of insulation nor the other benefits that shutters will give you.
That appears to show that you've taken a 1.8 u value window, put it in a cavity with a blind and come up with a lower u-value. The read out doesn't really mean much to me as it doesn't show any of the properties of the window. It appears to be comparing a window unit with a window built into a highly insulated wall?
Yup. Good aren't they. 😀
Base price of circa £200sqm for a Pelini interstital venitian blind, versus something from Homebase 🙂
Average u value for a window built into an insulated wall is always going to be better than a window calculated on it's own, but you haven't really improved the u value of the window, just included something in one calculation that you haven't in the other.
Base price of circa Base price of circa £200sqm for a Pelini interstital venitian blind, versus something from Homebase
£200sqm? That's mighty expensive and mighty sexy too, but still, mighty expensive. I assume the Homebase ones you're talking about you're bog standard venetian blinds, no? Because I've never seen insulated shutters on their shelves, the externally mounted ones that make burglars think twice.
EDIT: Don't seem to be able to find technical specs on the Pelini. 🙁
You buy 1 you get 1 free ..
Don,
Here you go[url= http://www.pelliniscreenline.net/ ]Pelini Website[/url]
and yes I was referring to a bog standard Homebase blind.
Still no technical info, I'm afraid.
They look like the blinds I mentioned earlier where the guy had a Grand Designs glass fronted house which for some reason got too hot when the sun shone.
They look quite sexy and seem quite appropriate on those glass fronted homes, what I don't see is what they offer over Homebase style blinds, except a bit of style. Will they reduce heat loss or just reduce solar gain? Will they reduce solar heat gain by much, I mean they are behind a pane of glass afterall? but I guess the gap is minimal, so not really an issue.
They don't look like they'll block that much light out either, a personal beef of mine. I hate getting up at sunrise and I think you get a higher quality siesta when the room is practically blacked out.
£200 per m² seems an awful lot just for style.
The other main problem I see is one of security, night time ventilation means that the window will have to be open and inviting to our less honest cousins. But again, I assume, the market that pays that sort of money will have their own security team at the house anyway. 😆
I think you mean Brise Soleil. It will reduce solar glare and allow solar gain during the winter months when the sun is low. I can quote the BRE for the calculation / ratio tables but don't go there its boring.
The 0.81 calculation is incorrect. It needs to be the reciprocal of 1 so 1/0.81 = 1.2 U value.
Solar and blinds = yes you can include it within the calculation. Never allowed for a blind or curtain on a U value calculation. That would be cheating.
Mention Grand Designs and I thought Brise Soleil
I have that type of internal DGU blind on my extension. At £1800 + VAT money well spent.
The 0.81 calculation is incorrect. It needs to be the reciprocal of 1 so 1/0.81 = 1.2 U value.
So the other calculation is wrong too and the 2G window is 1/1.8 = ??
I don't think so and not far off if you work with the k and r values, but feel free to take it up with the guys who tested it.
That would be cheating.
Why would it be cheating if it's a part of the fabric of a building? You could argue that the u-value is only valid when the blinds are down, in the same way that the u-value of a window is only valid when it is closed. 😉
I think logically the blind is very difficult to argue against on the practicalities. You use them when you need them, you don't use them when you don't need them. it's an extra layer of insulation and will reduce solar gain. They allow night time ventilation while keeping the property more secure with the windows open. They offer an extra layer of defence against buglaries and are hidden away when you don't. A range of colours mean that a smart architect can use them to enhance the look of a building, and some of the €million + homes I've seen them on, the architects have done a bloddy good job. nd when we have starting prices in the region of less than £100 delivered, they're not as expensive as you've been led to believe either. 😉
I think you mean Brise Soleil
Who means Brise Soleil? What and where?
Outside surface resistance - - 0.040
WINDOW 20.0 - 0.385
Inside surface resistance - - 0.130
Add together 0.04 / 0.385 / 0.130 = 0.555
1 / 0.555 = 1.8 U value.
Pointless argument on the second one. The thermal properites on a internal blind are so low it not worth adding to the overall calculation. A curtain sits out from the window and therefore cold air will bypass around the sides so how do you measure the gain. However both can be used to counter solar gain and figures / correction factors were previously available. (It's all done via building modelling these days)
I paid £1800 + VAT for my blinds in 2010.7m2 so around the £300m2 mark.
