New construction windows
jw54
| Posted in General Questions on
I am ready to order windows for a new house in Zone 5a. The south facing windows were going to be Harvey Tribute double hung with 3x ThermaLock glass, u value-.17, shgc .24 a $159 add-on. However, they now offer Sungain glass u- value- .29, shgc .48 a $39 add-on. Should I go for the lower u-value or the higher shgc ? The double hung windows are in bedrooms and average 100 UI. Does the extra sungain offset the lower u value in windows this big factoring in the cost difference ? I can always use the savings difference on energy blinds.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
My gut says you are in a heating dominated climate zone. Get the better U value window.
If you want real answer the only way to get one is to build a computer models of your house with your weather and run the numbers. BEopt is the program if you are willing to invest the 20-40 hours to learn the program.
https://beopt.nrel.gov/home
Walt
"Does the extra sungain offset the lower u value in windows?" in a word, no. The sun will be shining through your windows in January for a few hours a day; the rest of the time you will be losing heat.