A Rated Windows vs B Rated Windows

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Is A strictly better than B no matter what?

I've read somewhere that A rated windows use solar energy to increase heat inside the house however if the house doesn't get much sun is it pointless to get A rated windows?

The issue I see with that is that B rated windows lose 6 kWh/m2/per year whereas A rated windows gain 2 kWh/m2/per year. If you dont get good sun does that mean A rated windows wont perform at 2 kWh/m2/per year and you may still end up losing energy?

Thanks
 
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The issue I see with that is that B rated windows lose 6 kWh/m2/per year whereas A rated windows gain 2 kWh/m2/per year.

So, does that work out a 50p or 80p extra per year in fuel bills?

Work that out, and then work out the difference in cost of the two types to see which one costs more over their lifespan ... which is 10 years for a DG unit

I would love to meet someone who could honestly say "You know, this single A-rated window in my lounge is much warmer and costs me much less in gas bills than the B-rated window I had previously". I think it just ain't going to happen

All these KW/h values look good on paper, but have little impact in the real world
 
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forget about bfrc ratings, they are so misleading. They take into account solar gain (the amount of sunlight that travels through the panes) which depends on so many variables. Stick to the overall u value of the window, which is constant.
 
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Thanks

What I dont get is that I thought DG was supposed to prevent heat going out but most of the B rated windows have a minus energy index.

The A's have positive numbers which implies you gain however if I got A would they function at 100% if I dont get much sun
 
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What you need to understand is that you could have 2 windows, one of them 1000mm wide x 1000mm high. this window is an A rated window. You could also have another window 900mm wide x 900mm high that is identical, this one is a B rated window. Why? because the glass is the most energy efficient part of the window, the more glass in the total surface area the more efficient the overall window will be.

It's not just A rated windows that use solar energy to increase heat inside the house, any windows will do this.

There is no "secret ingredient" or "magic formula" for an A rated window. My company uses soft coat planitherm low e, with warm edged spacer bar. This can achieve an "A" rating in double glazing. We tend to do a lot of triple glazing these days, which will give an A rated window in any style. So you have 2 windows, both A rated, but the dual coated low e triple glazed one is vastly more energy efficient than the double glazed one.

The U value of the Double glazed A rated window is 1.4w/M2K.


The U value of the Triple glazed A rated window is 1.0w/M2K.

This is why i don't rate BFRC's WER ratings, they are misleading and already outdated.
 
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Thanks but you lost me in your example. The u value of the triple one is lower therefore better than the double glazed isnt it?
 
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So if the A rated is 1.5 and B is 1.4 you reckon B is better even though the Energy Index is better for the A?
 
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you also need to keep in mind they are talking about the maximum in the perfect situation rather than saving over the area off all windows in all situations
so if they say quote a 3% saving "possible" the actual average will probably be nearer 1%
then you have the other factors like the window is only one source off heat loss if its say 7% off the total loss then the saving will be diluted by 14 as the windows are only 1/14 off the heat loss equation
so 3% saving is now 0.07%

also remember most off the "heat gain" is in the summer when you don't need it
 
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This is another area of confusion. One sales guy said that double glazing should reflect some sunlight to prevent it being like an oven. Is that true?

On a slightly different note, The Bullet, how would you rate Anglian Windows compared to yourself? I assume you're a local DG firm.
 

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