Window Screens
I have windows that face southwest. They are not low E windows, I like the warmth they provide in the winter but detest the heat gain in the summer. Is there a screen that would be as good as (if not better than) replacing with a low e window?
So the question is, are there screens that are as good if not better than low-e coatings? Has there been any testing of the screens to support it?
For the kitchen, it opens to my deck and I was thinking of adding an awing that could be used in the summer but allow the sun in the winter.
I also have a friend that have windows facing the east. His are accessable from a deck, a removable screen would work for him.
My question boils down to is will a solar screen block as much radiant heat as a low-e coating or do we just need to use them in conjunction with a low-e coating. Both home are 15-20 year old and currently have the original windows.
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Replies
Robert,
First of all, I think you are confusing low-e windows with low-SHGC windows.
Low-e coatings are designed to lower the U-factor (raise the R-value) of a window. But there is no guarantee that a low-e window has a low solar heat gain coefficient (SHGC). Some low-e windows have a low SHGC, while others have a high SHGC. Both types of windows are useful, depending on the orientation and climate.
It sounds like you are interested in a low-SHGC window (at least during the summer). Unfortunately, I don't know of any screen to accomplish what you want -- to lower the SHGC of your window during the summer, while still being easily removable for the winter.
Here are your options:
1. An ordinary insect screen will lower the SHGC of your window. However, it also cuts down on transparency.
2. Awnings and exterior shading devices work well, at least until the sun gets very low in the sky in the late afternoon.
3. Interior blinds, shades, or curtains help a little, although not as much as exterior shading.
4. If you are willing to give up some of the desirable solar heat gain during the winter, you can install a window film that lowers the SHGC of your window. These films have mixed reviews -- some people like them, but others say they aren't very durable. The best-known manufacturer of windows films is 3M:
http://solutions.3m.com/wps/portal/3M/en_US/Window_Film/Solutions/Markets-Products/Residential/
I don't know if it's what you're considering but you certainly don't need to replace your windows or apply a permanent film to improve your heat gain problem. A regular insect screen makes a noticeable difference but there are specialized products which can perform even better than low-SHGC window films and are removable to boot. If you google solar control window screens you'll find a wide range of options including motorized systems etc. Awnings are excellent too.
Something like this might work for you?
http://www.ezsnapdirect.com/
I've seen a couple of good reviews, it depends on your window type though, and your exterior access to windows.
You could always go the expensive route and get some sweet european external roller shades.
It would probably be a DIY, but shade cloth might fit the bill: http://www.farmtek.com/farm/supplies/cat1;ft1_shade_houses_material;ft1_sunblocker_bulk_shade_cloth_1 It's used in greenhouses.
harlan.
For reducing solar gain (lower SHGC):
a) I agree with Mr. Morgan's suggestion: solar screens as one option. If the screen is motorized, make sure it can survive strong wind bursts.
b Solar Grates produce savings similar to solar screens but with differences. Screens are 80% closed and darken the room some while maintaining a view during the day. The night view is not as good. The view from the curb is changed. If the screen is motorized the screen will be less visible when retracted.
Solar Grates are designed for seasonal use. They are installed and remain in place without operator attention until removed in Fall. Grates are 80% open and allow a view. The view is curtailed at large angles. The view at night is maintained. The grates do not operate as a screen to block most light. Grates use selective reflectivity to absorb infrared while passing visible light. This keeps the room cool and bright. Grates are unnervingly robust. No rattles and maintenance of grates is nil after 10 seasons in the Chicago area.
For more details: http://hjcochran5.wix.com/solargrates101 .
The name of the game is to capture the infrared before it penetrates the window. For improving insulation value of windows I use acrylic inserts that create a dead air space without fogging and without affecting the view. You see them but you don't notice them.