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High 'R' Value and Low 'U' windows?!

Posted by earthaven (My Page) on
Sun, Dec 17, 06 at 19:12

Hi window people --

The house we're building is in the LEED for Homes Pilot Program. "LEED" stands for Leadership in Energy and Environmental Design. In our area (North East) we need to have a U value of atleast I'm finding it difficult to find this on all the websites. The Pella windows we've chosen have an "R" value of 4 (which is a U of 0.25) but they are VERY expensive. We have primarily casement style windows, with awnings up high, and a few sliding glass doors... and a couple rounds...

Can somebody recommend a good quality window to fit our needs? We would like wood inside, and cladding out is fine! You can see plans for our house on our blog...

Thanks in advance,

Here is a link that might be useful: scroll down for house plans here

Follow-Up Postings:

RE: High 'R' Value and Low 'U' windows?!

Good morning Lisa,

If you need windows with U value in the .25 range then you are looking at expensive windows - there is no way to avoid it.

At that energy efficiency level you may be looking primarily at triple pane with LowE coating on two panes plus either argon or krypton fill.

I would suggest visiting the NFRC web site for a listing of many windows and styles as well as their U value measurements.

One last thought - drop the idea of R value when dealing with windows and stick strictly with U value. R value when associated to window performance often means a center-of-glass reading which is the warmest spot on the window. U value SHOULD relate to the entire window assembly - and it does on the NFRC site.

Good luck!

RE: High 'R' Value and Low 'U' windows?!


We're trying to be as energy efficient as possible (tho not in the LEED program range) and found that double hung, aluminum clad exterior/wood interior windows had a higher U value than all wood windows. (Perhaps because metal is a better conductor of cold/heat? I dunno.)

We decided on Eagle brand double hung, low E, Argon filled, alum clad exterior, wood interior with a U value in the 35 range. I am still second guessing our decision to go with clad vs. all wood, but we wanted aluminum for the durability (we are in northern NY on a lake and get a lot of wind, snow and weather). They are ordered and will arrive and be installed the second week of January, so I can comment on product quality then.

Congrats on your very cool and highly personalized home.


RE: High 'R' Value and Low 'U' windows?!

Thanks for the replies. Oberon I'll check out that site, and sandyponder, good luck with your windows! I think we're going with the Pella clad/wood windows, the Designer series for most of the house -- at .25, and the architect series on the Western facing front side, which are .31. I think we got a really good price, considering we have almost 100 windows! How crazy is that? Well, I hope we don't need to use much electricity for lighting during the day!!!

Happy 2007 all....

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