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-   -   "R" and "U" factors (http://www.diychatroom.com/f104/r-u-factors-151060/)

emscot 07-21-2012 03:01 PM

"R" and "U" factors
 
What are the "R" and "U" factors for the Atrium Reliamilt series 3500 windows sold be Lowes - and the same info for the American craftsman AC12 series sold by Home depot?

Just Bill 07-22-2012 07:35 AM

what you are asking does not seem to translate in my computer, just get symbols/letters. But in general, IMHO, the windows available from big box stores are not worth the time to install them.

There is little craftsmanship in AC windows. I was an Atrium dealer back in the 90's. Only did a few jobs before I found out they were not ready for prime time. Since they are available at big box, I assume nothing has changed.

oh'mike 07-22-2012 07:40 AM

The site program has got you--let us know what you are saying and a MOD will edit your post so that it makes sense---MOD

BigJim 07-22-2012 07:46 AM

I think the reason the post is garbled is he copied and pasted the same post from another site, I could be wrong about that though.

Windows on Wash 07-22-2012 09:52 AM

U-Factor is the inverse or R-Value

concretemasonry 07-22-2012 04:03 PM

Inverted or not, "U" and "R" values are just short term tests (a few hours) or even worse, based on calculations. They apply to the material properties of thee product (insulated glass, fiberglass, etc.) being tested and not for assemblies used in real construction where edges and framing members can reduce the value properties dramitically when it comes to real uses. They also do not account for other reductions in heat loss or gain, especially radiant loss at night through windows with no opaque or translucent materials or for the normal air infiltration factors common with all installed opening inserts.

Dick

As an example, window with an "R" value of 3.0 is about the same as an uninsulated 6" concrete wall with no drywall or foam. - Fortunately window areas are a small percentage

Windows on Wash 07-23-2012 04:54 AM

Quote:

Originally Posted by concretemasonry (Post 971824)
Inverted or not, "U" and "R" values are just short term tests (a few hours) or even worse, based on calculations. They apply to the material properties of thee product (insulated glass, fiberglass, etc.) being tested and not for assemblies used in real construction where edges and framing members can reduce the value properties dramitically when it comes to real uses. They also do not account for other reductions in heat loss or gain, especially radiant loss at night through windows with no opaque or translucent materials or for the normal air infiltration factors common with all installed opening inserts.

Dick

As an example, window with an "R" value of 3.0 is about the same as an uninsulated 6" concrete wall with no drywall or foam. - Fortunately window areas are a small percentage

+1

They are certainly tests that do not account for the full spectrum of real world simulations, but they are the best that is out there now and they can be used as a comparative benchmark for products.

Proper installation is critical as you mentioned above.

HomeSealed 07-23-2012 11:38 AM

+2. The U value, shgc, air infiltration, and design pressure ratings may not be 100% representative of how the windows will perform to a "T", but assuming proper installation they are the most comprehensive measure that we have. In addition, the U value is tested over an entire assembled window unit (glass, frame, weatherstripping, etc) and at a mild windspeed.
I would also agree with a previous poster the products in question are not well regarded, and do not have very good ratings comparatively, especially in the area of structural ratings. To answer the question, in standard form they both hit around .30 U-value +/- .01 or so, and that would equally R 3.3. I like to see a double pane unit closer to R4, and triple at R5 (.20 u value) or better. If you live in an extreme climate, you'll want to give extra emphasis in certain areas as well.


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