I bet most of you are familiar with the claims of the window industry marketing a Low-E coating as a Cure-All for any house, any climate and any window, no matter what direction it faces.
You have likely seen the heat lamp test that make people think that their products have some serious insulating properties.
While I am not doubting on the effectiveness of Low E coating for cooling-dominating climates (installed on the windows that the Sun shines through) I have real doubts on how effective it is for cold climates.
There is a claim that a HUGE portion of the heat that escapes through a window does so in the form of radiant heat and Low E coating reduces it.
I am sure Low E is very effective for reducing radiant heat loss. I am very skeptical on the size of the portion of the escaping heat being radiant.
And then I am also thinking that all the rejected solar gain in the winter must be greater than the amount of heat we trapped inside. (just because Sun's surface is about 10 000F vs 68F for the surface of the objects inside a home)
I bet many of us would benefit from reputable data on the portion of the heat that escapes through a window in the form of radiation.
Opinions, thoughts and facts appreciated.
Low E helps in summer when the sun is at a different angle. The UV rays reflect differently then the winter, when the sun is lower. Heat is better reflected in summer versus winter due to the angle of the sun during the seasons. The solar gain in winter comes from the sun's angle allowing more UV/Heat in this way as well, since it is not reflected by the Low E as easily. As far as Low E helping during cold months, the radiant heat form interior lighting gets a slight gain in heat by reflecting heat from the windows into the home. Not in dangerous amounts, just enough to help a little in comparison to non Low E coated windows. Interesting stuff. There is a lot of information, sometimes too much for the consumer. It is always best to do research from homeowner testimonials as well. Great post by the way
So much of this depends on the size and orientation of the window. North-facing picture windows are more common than one would suspect, and with our high altitude dark nights, you can really feel the "suck" from the night sky.
New Mexico has adapted the IECC to be more "passive solar friendly."
http://www.emnrd.state.nm.us/ECMD/FORMS/SolarWorksheet.xlt makes it relatively simple for a building official sign off on a design.