U value of window frame and glass

J

johnnyg

Registered User
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Hi,

I've been given the following U value figures for the window and glass as one unit:

PVC Low e soft soft coat: 1.6
PVC Pilkington K-Glass:1.9

Laminated wood windows with soft coating: 1.5

Are these good u values?

Has anyone any experience with laminated wooden windows? they work out 30% more expensive than PVC

Also is there such a thing as u Values for doors?

Thanks
 
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johnnyg said:
Are these good u values?

Also is there such a thing as u Values for doors?

Thanks
Click to expand...

Not particulary. You'd want to be looking at a 1.2 overall window u-value to get good performance.

There are u-values for anything. I've seen several companies quote 1.4 for their doors which isn't particularly good imho. However, you can go for a passive house door which will set you back about 5K and look like something that should be on a bank vault.

Depends on how you are building also. If you are putting in wall vents or trickle vents in windows as your ventilation solution for example then I wouldn't be getting too hung up on window and door u-values.
 
whats your wall construction???

you choice of window or door should be pro rata with your construction u values.....
 
sydthebeat said:
whats your wall construction???

you choice of window or door should be pro rata with your construction u values.....
Click to expand...

This one always confuses me. Lets say you build a wall to current building regs i.e. 0.27 u-value. The VERY best windows will come in around 0.6 u-value which is considerably worse than the wall u-value. Yet people would say that you would pair that wall with a regular pvc type offering like any estate house e.g. u-value 1.5 - 2.0

It seems to be that once the wall u-value hits 0.2 and lower that people decide that the window spec becomes important. I've been absolutely guilty of this.
 
Hi Sydthebeat,


Its Standard block construction with 150mm cavities filled with ecobead platinum bead insulation. The u value is supposed to be 0.2.

I will be going for wall vents not sure if trickle valves are better? This area is still open for change..
 
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sas said:
This one always confuses me. Lets say you build a wall to current building regs i.e. 0.27 u-value. The VERY best windows will come in around 0.6 u-value which is considerably worse than the wall u-value. Yet people would say that you would pair that wall with a regular pvc type offering like any estate house e.g. u-value 1.5 - 2.0

It seems to be that once the wall u-value hits 0.2 and lower that people decide that the window spec becomes important. I've been absolutely guilty of this.
Click to expand...

Sas..

The regulations state the minimum u value for walls is 0.27, but the min u value for windows or doors is 2.2.....

The truth is that standard block cavity wall construction with partial fill insulation board barely meets the regs on paper, but in practise im convinved they come nowhere near the minimum regs. Thats why i would advise clients to install windows or doors pro rata to their wall construction. ICF, SIPS and Poroton etc are readily testable and generally give the declared u value. Block walls arent.

Johnnyg, you should think about not installing passive ventilation but incorporating a HRV system if possible. This would increase the airtightness of your construction and subsequently increasing your energy efficieny and decreasing your fuel costs.
 
The size and orientation of windows is also a factor to be considered. Small windows facing north and larger windows facing south will add to the heat gain from sunlight.
 
Ted hit the nail on the head. Interesting reading [broken link removed].
(before anybody says anything, yes, it may be a biased article as it is published on pilkington website who would obvioulsy have some vested interest in pushing things there way)
 
Hello,
I read your mails regarding U-value of window frame and glass.
At the moment I am calculating the thermal (cooling + heating) for different building types in different locations in the world (Germany, Spain, UAE , & Thailand).
In UAE (Abu Dhabi), the standard glazing U-value for houses is 3.28 W/m^2K , I did not fine the U-value for the frame, it is power coated aluminum frame, what is the u-value of such material??
Is there any source of reference available in the Internet that I can get typical u-values for different location in the world??

Thanks,

Nada
 
nadarikabi.. the u value for a powder coated aluminium frame depends if the frame is thermally broken or not....

generally aluminium frame not thermally broken = 1.9 - 2.2
aluminium frame thermally broken = 1.0
 
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