What glass type for passive solar sauna?
tkranda
| Posted in General Questions on
Hello All. I am thinking about building a solar sauna and although I think I have a general understanding of the key principles I do have a question about glass. Clear glass would let in the most energy, but privacy is an issue. So I am considering the textured glass option. Ripples, rain tracks, wavy glass, etc. It would remain essentially clear (not frosted of coated/covered with anything). So my question is there be significant energy loss: clear-but-textured glass compared to smooth clear glass? Hope someone out there has come upon and mastered this issue in the past. Thanks.
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Tom,
As I'm sure you know, a passive solar sauna only works on bright sunny afternoons. I love to take a sauna when the weather is cold and cloudy -- something that you can't do with a passive solar sauna. So keep that in mind.
Another point: if you have any Finnish or Russian ancestors, you probably know that a real sauna needs to be able to hit 200°F -- and that's going to be hard to do with a passive solar sauna.
I think it's fair to say that the glass with the highest SHGC (solar heat gain coefficient) is clear low-iron glass installed in a single-glazed fixed window. Other types of glass, including wavy glass or frosted glass, will have a lower SHGC.
Hi Martin, Thanks for the comments. I live in Phoenix Arizona. Cold and cloudy just doesn't happen here. It can be over 100 degrees F after midnight during the hot season. As it turns out 100 degrees, wet and no sunshine can actually be chilly. "It's a dry heat." Regarding the SHGC rating. I will ask but I am currently looking at out of the box "Glass Shower Door" panels. I doubt they have such a rating given their indoor purpose. But perhaps all glass must carry the rating. The panels come without any hardware (handles and frames) so perhaps I can incorporate them into the 10 foot west-facing front of the sauna. One panel acting as a door. With a glass panel incorporated into the roughly 4X10 foot roof. The Russians and perhaps the Finns are nuts. (Not really) but in the US, sauna heaters have an auto stop at 194 F for safety reasons. I will not have a heater of course but believe I can get above those temps certainly during the day. The planned sauna will have 6 foot high cinder block walls on the three none west-facing surfaces. The key will be to collect and hold enough heat till evening for late night hot tub-pool-sauna sessions. Thanks again for the input.
Any privacy glass will have a reduced SHGC. There are plenty of real window manufacturers who offer a wide variety of privacy glass with SHGC ratings. You could use their ratings to get an idea of the SHGC and guess that some non-rated glass will be similar, if you don't mind the uncertainty.