Anyone ever hear of a window, or unit of insulated glass, as having different winter and summer U values? 

 

This wasn't on an NFRC sticker.  It was on a glass manufacturer's spec sheet. 

 

They listed it like this:

 

Winter - Air / Argon  0.35 / 0.31

Summer - Air / Argon 0.32 / 0.28

 

Our program requires a U value of 0.30 to receive an incentive rebate.  So obviously, homeowners and contractors want to average the summer and winter Argon fill U values to come up with an average of 0.295 and call it good.

 

I think it is just a piece of insulated glass that they want to have installed/retrofitted into their existing wood windows, and get an incentive for that. 

 

Views: 5152

Attachments:

Reply to This

Replies to This Discussion

The winter U-value is what is shown on the NFRC labels, and should be used for code compliance and incentive programs. It is calculated at -18C (about 0F) outside, and 21 C (about 70F), and a roughly 15 mph wind speed. The summer U-value is calculated with conditions where it is warm outside and hardly any wind. This means that the U-value will be a bit better, but it is not a representative condition for heat losss. The Solar Heat Gain Coefficient (SHGC) is more important during periods with solar gain. So think U-value for heating, and SHGC for cooling.

Christian
WIndows and Daylighting Group
Lawrence Berkeley National Laboratory
Adam:

Currently in communication with this gentleman:

Andre Anders, PhD
Leader, Plasma Applications Group
Lawrence Berkeley National Laboratory
1 Cyclotron Road, MS 53, Berkeley, California 94720, USA
Tel. 510-486-6745, Fax 510-486-4374

He's circulating the information among his associates and will be in touch following the holiday. Will probably find it's way Christian at LBNL, who has responded since last I checked in.

BTW, Christian's advice to use the winter number is probably not what you wanted to hear regarding the available incentive. If 0.30 U is a common cut off # for incentives, I would expect manufacturers to work to that figure, although in a manufacturing environment, such changes may be a challenge. Perhaps a bit of latitude from incentive providers is in order...who is going to notice a U difference of 0.01 ?

Thanks for surfacing this mystery.
Steve, Adam,

Andre forwarded your question to me, that is why I responded here. Many manufacturers have products that meet U=0.30, since that was the cut-off for the IRS tax credit.

If you are looking for even better windows, you can take a look at this website, where you can find listing of manufacturers that meet U=0.22 and less.
http://www.windowsvolumepurchase.org/

Christian
Thank you for the replies! Our program does require NFRC stickers, so this guy is going to be out of luck anyways.

But I was curious about the different winter and summer U values anyways. Thanks for the response and clairificaiton!

Adam

RSS

Forum Discussions

Solar panel leasing

Started by Luis Hernandez in General Forum. Last reply by Sean Lintow Sr on Sunday. 3 Replies

Factory built Net Zero

Started by Steven Lefler in General Forum. Last reply by Steven Lefler May 18. 3 Replies

What causes a temperature plane in a home

Started by Energy Wise Solutions in HVAC. Last reply by Jose Macho May 4. 7 Replies

Latest Activity

Horace Douglas Hunt, Jr. commented on Home Energy Magazine's video
Thumbnail

Legends of Home Performance: John Straube, Professor, University of Waterloo, Prin. RDH Building Science Inc

"Nice meet and greet video. Sorry to hear Victors reply about jobs and interest. Unfortunately, it…"
4 hours ago
Horace Douglas Hunt, Jr. liked Home Energy Magazine's blog post First-Ever Comprehensive National Standard Practice Manual is Updated Guidebook for Energy Efficiency Cost-Benefit Analysis
4 hours ago
Cameron C. Habel is now a member of Home Energy Pros
6 hours ago
robert jones posted a status
"I have energy auditing equipment for sale. I'm in the 518. 518-209-5912"
yesterday

Photos

Loading…
  • Add Photos
  • View All

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service