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: 5923

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

Latest Activity

Brett Little posted events
8 hours ago
Ben Thompson replied to Stuart Perkin's discussion TrueFlow in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi Stephen. Do you still have a Trueflow that you would sell? Ben Thompson,…"
yesterday
Ben Thompson replied to Landon's discussion WANTED: Blower door complete set Retrotec or Minneapolis in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi Landon. I have a Minneapolis blower door set-up that I would like to sell. It's in…"
yesterday
Ben Thompson added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Wanted: TrueFlow plate

Seeking an Energy Conservatory TrueFlow plate (grid) in good condition. Ben Thompson.…See More
yesterday
Scott Partlo replied to Jerry Needham's discussion Closed cell on roof deck to prevent mold.
"You say that 2" of closed cell foam is applied OVER the roof deck.  Where exactly was the…"
yesterday
ayazfudugo1 replied to Tom Smith's discussion Are Energy Efficient Windows worth the investment?
"For both new and existing homes, Energy efficient windows are an important consideration Heat…"
yesterday
Profile IconTodd Williams and Haley Keegan joined Diane Chojnowski's group
Thumbnail

Hall of Shame

In this group, members share an array of images from the field, showing the kinds of issues…See More
Friday
Todd Williams liked Diane Chojnowski's group Hall of Shame
Friday
Home Energy Magazine posted a blog post
Thursday
Leona Zoey posted a blog post

Landlords Are Your Friends

While it may be easy to forget given their apparent position of power over you, landlords usually…See More
Thursday
Haley Keegan joined Building Performance Institute's group
Thumbnail

Building Performance Institute (BPI)

BPI is the nation's premier standards development, quality assurance and credentialing organization…See More
Thursday
Donald Hester replied to Jerry Needham's discussion Closed cell on roof deck to prevent mold.
"For the roof shingle issue that is an unfortunate issue with many home inspectors that have been…"
Thursday
Profile IconJason Green, Dennis Smith, Alex Ortega and 2 more joined Home Energy Pros Forum
Thursday
tedkidd replied to Quinn Korzeniecki's discussion BPI CEO Larry Zarker's Review of "The Home Comfort Book" in Healthy Indoors Magazine in the group Building Performance Institute (BPI)
"...free chapters of book available here - http://bit.ly/HPchapterlist"
Thursday
tedkidd liked Quinn Korzeniecki's discussion BPI CEO Larry Zarker's Review of "The Home Comfort Book" in Healthy Indoors Magazine
Thursday
William Collins's video was featured

Foam Kits vs. Spray Sealants Gun

How does the Foam Kit stack up to the Spray Sealants Gun when it comes to simplicity? When you integrate the Spray Sealants Gun to a 16lb Canister, you creat...
Thursday
Scott Becnel added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Brand new DucTester at a discount

Brand new DucTester at a discountI have a brand new 300 DucTester system from Retrotec for sale at…See More
Wednesday
Scott Becnel joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
Wednesday
Lucyna de Barbaro liked Home Energy Magazine's blog post AeroBarrier: The Silver Bullet to Zero Energy Affordability, by Paul Springer
Wednesday

Photos

  • Add Photos
  • View All

© 2018   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service