Your thoughts on my window choice
RussMill
| Posted in Energy Efficiency and Durability on
Thoughts on window/glass choice. Climate Zone 4/5 on the line.
All are Casement with one Awning. (16) windows all together
Full Frame Center Glass
U .15 U.07
R 6.7 R 13.5
SHGC .22 SHGC .31
VT .33 VT .50
Please let me know what you think of this choice for general all round useage. We aren’t chasing passive solar heating and we aren’t building a Passive House, Goal is 1.0 ACH
Thanks
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Replies
Amy - I am going to guess those are Alpenglass Balanced-9. The U and R-values are great for your climate zone, but for me the problem becomes the VT. I am fine with .5, but .33 is too dark for me. If the .22 SHGC is for western facing windows, I would rather add some solar shades for use in the late afternoon and keep the VT higher. But that is just me, you really have to see for yourself and decide.
Amy,
I assume these are triple-glazed windows. My only comment is that you have chosen low-solar gain glazing -- which is typical these days. Some designers might want a higher solar heat gain coefficient for the south-facing windows. But your windows will be good, especially during the summer.
In reply to: USER 5574861: Sould I see this glass in person before sealing the deal?
YES Alpen, I left that out because of starting a "brand discussion".
Martin,
Yes they are low solar gain, I don't have a consultant or anyone really. I couldn't find anyone local and the ones I did contact wanted crazy amounts of money. I've read alot here and elsewhere and while we have good overhangs planned, 30" to be exact on the south side, 1 story house btw, I didn't want to be sorry by going higher on the solar gain. We've been building spec houses of good quality for 20+ years but, never a house like this. People in this area won't pay for the efficiency! This is our own home. You and GBA started my path to this Net Zero project!(I mean that) Fives years on the paper and now finally settling in to start building.
is it a good idea to prioritize cooling during summer over winter solar gain?
How big a difference can be between low solar gain glazing and high solar gain glazing + solar shades + probably a pergola?
Davor,
The decision about what SHGC to select for south-facing windows is tricky, and is best determined with software (for example, PHPP). In general:
1. Low-solar-gain triple glazing sometimes has a low VT, which means that the glazing looks a little gray. Some people don't like that.
2. Houses with very large areas of south-facing glazing need to worry about overheating, and should probably consider low-solar-gain glazing even for the south windows.
3. Houses with a more moderate area of south-facing glazing in Climate Zones 4 or 5 would probably benefit from high-solar-gain glazing on the south side, especially if there is a generous roof overhang.
4. In Climate Zones 1, 2, and 3, cooling concerns tend to trump heating concerns.
-- Martin Holladay
From the Jonathan Lawrence - AKA USER 5574861.
Amy,
See if you can find a window retailer where you can look at different options for SHGC and VT. I think you might find it useful, especially if you are a fan of natural sunlight or have nice views outside the windows.
Martin - Do people have to be logged in now to see names? I noticed on my desktop where I am logged in the names show up, but on my mobile devices which is not logged in, it is only users.
Jonathan,
You have correctly noticed that on some GBA pages, user names are displayed differently for readers who are logged onto the site as GBA Prime members than for readers who aren't logged it. In most cases, names are less likely to be displayed when a reader isn't logged in.
That said, many newly registered GBA readers are being assigned the screen name "N/A N/A," which is extremely confusing. This problem crops up on the site whether or not you happen to be logged in.
We are crossing our fingers, hoping the the technical team fixes this problem soon. Thanks for your patience.
-- Martin Holladay
Well, the best alpen can do is .42 so, I may be back to the drawing board if they're as dark as has been stated above.
I am open to any other mfg's but, you run into price point issues, quickly!
Amy,
Have you looked at Intus? They are fiberglass like Alpen and are very price competitive. They have SHGC just under .5 with VT at .7. I don't know if they make casements or awnings though. I added a couple of Marvin Tilt n Turns to my current house a fews years ago and I love them. I won't go back to DH or casements. The only downside with the windows I added is the VT is .43 and did not know at the time how dark they would look to me. To make things worse, they are on the north side of house.
Jonathan,
As far as I know, Intus frames are made from vinyl, not fiberglass.
-- Martin Holladay
Yes, my bad U-PVC vs fiberglass.
User-5574861 I have installed MANY Marvins the past 20 years, while a nice window, their air leakage, (to my knowledge) has never been gotten under control. That's what happens some around here, they build a well insulated house and throw Andersen 400 series in that whistle in the wind.
Martin- No Vinyl for me!
We have many different flavors of Marvin windows and doors in our home and they seem generally pretty decent. One thing that definitely made them better was that the Marvin tech spent the good part of a day here post construction adjusting all the seals (and cranks and child safety latches etc). I think that definitely made a difference when we ran our blower door test.
Amy's comment did make me remember a Marvin related question though.
When we finally got done with our ground floor stucco I did a thorough cleaning of the two sets of proximate Marvin double-hung windows. Noted these little styrofoam blocks in the corners. I pulled them out to clean (I think I saved them, maybe). Anyhow what I wondered was what they were doing and if they weren't a little air infiltration "cheat" at those corners. They were in when we did the last blower door test.
Just wanted to chime in on the visual transmittance question. I have Alpen windows and have posted my positive feelings for them before. I deliberately selected low SHGC windows for my own design based on the summer loads I would face and am happy I did so. I was initially startled by the VT value you posted so I dug out the original stickers from my windows and was surprised to see the casements are rated at .38 and the fixed are .44. I suspect the difference in VT is due to the casement windows having additional framing material present for a given rough opening. In any case, the glass-film-glass in all units are assembled with the same coating order and materials and pass the same amount of light per sq inch regardless of the frame.
The glass VT will be constant over the entire glass area, so the whole window value I think is a bit misleading. There is no difference looking through a casement, awning or fixed window. I suggest the "center of glass" VT if available would be a more useful way to judge how it looks, although industry standards may only allow for whole window ratings for comparison sake across glass-coating combinations. Be sure to consider the ultraviolet pass rate if you choose higher VT windows.
The visual effect is not that of tinted windows like you might see in commercial buildings. There is not the slightest sense of darkness or gloom if the windows are closed . Comparing the view through an open window will of course show the tint level present. A bonus effect of choosing the low SHGC and inherently lower VT has been a reduction of snow glare for the six months we have snow on the ground (or roofs) here in the SW mountains. As an aside, my spouse has a bit of SAD and formerly used a light box at our previous home. This has not been the case in the new house, although not living in the city probably helps too.
onslow,
I feel somewhat reassured.
Thanks
Amy,
Roger's first hand experience with Alpen is a pretty good endorsement.
The love of my TnT windows I mentioned above is not because the are Marvin, but because the are TnT. I find that style of window tighter, easier to clean (the few times I have done it), easier to open/close/lock and it provides better air flow because the opening is the entire length of the window and not dependent on the direction of the wind. I am pricing out windows for an entire house now and the same size TnT with triple pane is about half the cost of the double pane Marvin's I bought a few years ago.