Can we intersperse low e/high SHGC windows with standard low e on SE wall?
We are remodeling our home ~90 miles north of Seattle in Zone 4C and would like to incorporate some low E + high solar gain windows on the southeast face. Our contractor and the window salesman are discouraging it but also don’t have experience with these windows.
We are replacing older double pane windows that let in the solar heat and felt great on sunny winter days, but we did experience days in the summer when the room with those big windows was sweltering and uncomfortable. From some basic web searches, it seems like those windows probably had a SHGC around .8 while the high SHGC/low E windows we can order are around 0.5. Wouldl that be a noticeable difference in terms of summer comfort? We will also have larger overhangs than before, but they will only be 2 feet, and won’t provide total shading for any of the windows on sunny summer days.
We thought perhaps we could selectively install some high SHGC /low E windows and use the standard low E windows elsewhere in the same room along the southeast wall. That way, we can enjoy the feeling of the sun in winter by sitting near those windows, but not overpower the rooms in summer. We will have an efficient hydronic radiant floor for heat, but any added solar gain would be great.
Does this seem like a reasonable solution?
Thanks for any insights!
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Replies
Beth,
If you want a detailed analysis, you'll need to hire an energy consultant to do some energy modeling.
Generally, the pleasant effects of sunlight streaming through glass into a sunny room on a winter day aren't dependent on the SHGC of the window you are nearest to. The pleasant effects have to do with the elevated temperature in the room and the brightness.
Note that if you mix and match windows with different types of glazing, the view through the windows will be slightly different. Some people report that the view through one window looks gray beside a window with a different type of glazing. Will you be the type of person who notices -- and is irritated by -- these differences? That's hard to predict.
The visual aesthetic of the slightly different tint of different low-E coatings usually dictates keeping all the windows on a particular side of the house the same type of glazing. Mixing glazing types in a room will often look just fine if all the windows on a given wall are the same, say high SGHC windows on the SE side, lower SGHC windows on the SW side.
SW facing windows would still want to have a more moderate SGHC unless shaded.
In your climate/location high SGHC glazing on all SE facing windows should be fine. In other parts of the country that would overheat the place quickly on the summer mornings, but where you are mornings usually still pretty cool outdoors even in summer usually in the 50s F at dawn and almost never over 70F before mid-morning. See:
https://weatherspark.com/y/991/Average-Weather-in-Bellingham-Washington-United-States-Year-Round
SGHC 0.5 windows won't give you quite as fast a heat-up ramp as the clear glass windows but they also won't be as lossy, and the house won't cool off as much overnight as before (unless you open some windows), and won't have nearly the same draft of cool air falling down the face of the window on winter AMs. It's low direct gain, but less wind-chill/draft. But they will be daily net heat gainers (even on cloudy days) in the winter, offsetting heating energy use, unlike the older windows which are net heat losers.
Thanks so much for your replies! I would definitely be bothered by different window tints so I really appreciate you bringing that to my attention.
I understand the PNW primarily requires heating and that high solar gain windows are always a good idea for energy savings here, but this pdf from efficientwindows.org indicates that high solar gain windows are predicted to provide "worst" comfort in summer in Seattle.
http://www.efficientwindows.org/factsheets/Washington.pdf
Seattle does get 5 degrees warmer on average than Bellingham, but we just had a hot summer and I assume more hot summers are in the future. That said, we lived through it with our clear windows and no AC although it wasn't optimal. Unfortunately I don't know anyone with high SGHC windows here to talk to about their experience with it.
Does it come down to energy efficiency vs comfort? In our case, we'll have warmboard and aren't as concerned with solar heat capture, but we like the brightness and heat of those old windows.
Our house more SSE than SE so we get a bit more time in the sun, but it also sounds like the .5 would provide noticeably less heat ramp up than we experienced before. Does anyone have experience in this region with high SGHC windows?? Thanks!
What did you end up choosing, and how did it go?