Window advice – Zone 3
Coopsdaddy
| Posted in Energy Efficiency and Durability on
Well we are looking at Marvin all Ultrex, Andersen 200, Softlight Elements and Sunrise Vanguard.
We are in Zone 3 on a heavily wooded lot, 4 small window on the west, 2 covered by porch, 15 on the north northwest, 4 on the south and 2 sliding doors, one 6 footer on the south with a 8 ft covered porch and a 12 ft sliding door on the east covered by a 12ft deep screened porch.
What should we look for in U-factor and SHGC?
Thanks.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
I suggest that you start by reading this article: All About Glazing Options.
Great article but didn't really answer my ? For my zone and condition,I the most concerened with the two sliding patio doors.
You might like to review this article at BuildingScience.com. The table on page 10 may be helpful:
http://buildingscience.com/documents/bareports/ba-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones/view
I am in Zone 4 and I found Intus windows to be a bargain once I included the cost of finishing the interior (if you want anything but white). For a nearly equivalent price, the Intus U-factor is significantly lower, as is the airtightness. Custom sizes are no more expensive, and you can have huge sizes—eliminating the cost of clerestory windows to achieve an 8' head height for example. I also found the details available online are clear and complete, unlike almost any other manufacturer. And the window package options can be minutely tailored for each window.
Their lift & slide sliding doors are massive and also nearly airtight, but they do slide easily. For these you may have to pay a premium.
In Zone 3, their dual-glazed model will likely serve your needs.
I don't have any special qualifications to give window advice, but since you are soliciting it, here is my philosophy:
Regarding U-values, lower is always better. The real question is how much you should be willing to pay to get a lower U-value. The answer to that depends on how much you are spending on the remainder of the building envelope. If your insulation levels and air-tightness are at code minimum levels, then don't pay extra for better U-value. If your whole wall R-values are in the 20s then look for windows with U-values in the 0.15-0.25 range. If your R-values are in the 30s, look for U-values < 0.20. If you are building to passive house levels, then getting U-values down to the 0.10 ballpark is probably worth it. (If you are building to passive house levels, you probably have a consultant and software that can give you way better answers than I can.)
Regarding SHGC, I wouldn't choose windows based on a few hundredths difference. In zone 3, pick windows based on U-value and other criteria like looks and price. Then, if the window manufacturer offers multiple SHGC options, pick the lowest SHGC. In colder climate zones, there is value to high SHGC for some window orientations.
Quinton,
You've gotten good advice from David and Reid. The reason we can't tell you the precise U-factor and SHGC to aim for is that your window specs depend on your goals and your budget.
Most builders in Climate Zone 3 choose double-glazed windows, not triple-glazed windows.
If your windows are covered by a wide porch, the SHGC of the glass probably doesn't matter. Windows that are exposed to the sun (especially those on the east and west facades) need a low SHGC.
In all cases, a low U-factor is better than a high U-factor.
I vote for the Marvins.
have narrowed it down,we have been looking at anderson 200,marvin all ultrex,softlight imperial and elements and sunrise vanguard.
We like the marvin and sunrise for the cleaner thinner look but seems the sunrise is what we are leaning towards.We have 3 casements,20 shunts,a 12 ft slider and either a 6 ft or 8 ft slider.The sunrise 12 ft comes in 4 ft sections so I think a 8 ft door would look better as it's pretty close to the 12 ft door.The bid number are close enough to not matter between marvin and sunrise,both white on white