I tried posting about this in the HVAC forum a few weeks ago and got no responses, so I thought I would ask the greenhouse experts over here.

We are planning for a glass room/conservatory/sunroom in the inside corner of an "L" shaped house as part of a larger two-story addition and remodel. The HVAC forum has given us some great advice about how to heat and cool this room in our climate (zone 4/5, had over 100" of snow last winter, 66" so far this winter, summer temps peak at about 88 degrees).

Now one of the makers of these glass houses has a suggestion that I would like to run by this forum. Since one of the solid walls of this sunroom will be new build, he suggests that as a way of exhausting hot air build up during the summer we embed an exhaust fan high up in the new wall and exhaust the hot air out through the exterior second-story wall just above the roof of the one-story sunroom.

We are not planning a moist greenhouse, so the idea is just to run the exhaust fan during the warm weather season here when we are trying to remove the hot air that would build up when full sun is coming through the glass part of the roof.

I was given the names of two companies that make fans for this kind of purpose, Schaefer and Tamarack, but I assume there are others and would welcome suggestions. Greenhouses all seem to use exhaust fans so I'm hoping to get some tips.

The other question I have is about glazing. The windows experts at the US Forest Products Lab suggested that since we are so far north, we should consider not using low-E glass for any vertical windows that face south so that we can capture sun heat during our very long cold weather season and possibly also not use low-E for windows that face east. Western windows in summer are apparently the biggest problem for unwanted heat gain, but this sunroom won't have any and will be shaded by the two-story addition.

So the last question is about glazing for the roof, which will be partially glass. There seem to be many different kinds of coated glass and argon-filled glass for roofing. Many are colored, which I'm not sure is what my husband has in mind. What should we be specifying for the glass in the roof of this glass room?