| | | Windows are wonderful - they let the sun in to keep us warm - they open to give us fresh air from the great outdoors - they give us views and keep us in touch with the great outdoors. Windows are also bad - they compromise our privacy and security - they break - nobody wants to clean them - they are usually the largest component of thermal loss. | FREE TIP!!
Down & Dirty do-it-yourself
insulating
shutters! | Windows are basic to my approach to solar home design, but consider this:
Builders today are making fine efforts to minimize thermal loss in wall construction - thicker walls, more insulation, building wrap, vapor barriers. Today's better exterior frame walls will calculate out about R24, BUT
Then perhaps 20% of the exterior walls are replaced with windows/sliding glass doors, double-glazed rated about R2. Fine-tuning the R-decimals is usually pointless. Face the facts - the thermal loss thru the windows is about 12 times greater than an equal area of solid exterior wall. | To do the numbers, use U-values, the reciprocal of R-values; thus
using a 50' x 8' wall = 400 SqFt
Walls 80% = 320 SqFt * U1/24 thus U=.04 * 320 = 13.33
Windows 20% = 80 SqFt *U1/2 thus U=.5 * 80 = 40
the number for total loss is 53.33
so the windows losing that expensive conditioned air are responsible for
(53.33 / 40 =) 75% of the thermal loss in this wall! Of course if you have only single-glazed windows in the same wall, it's twice as bad. And it gets much worse still if your windows are old and have leaky seals and weatherstripping. So one needs to DO SOMETHING about that - we're talking about paying the heating or cooling bills vs. all the other things you might want or need, like FOOD! Or even worse for most people in this world, it could well be a matter of being unable to pay the gas or electric bill, thus having no heat or cooling at all! | | Shutters are our defense against most of the above, but have their own drawbacks. In solar homes, our primary concern is thermal loss, and we can deal best with that by using shutters and/or well-designed window coverings. | | I will be adding more to this page as time goes on, but since it's winter now and the snow is flying and the heaters are screaming, I want to first give you a quick, cost-effective way of dealing with thermal loss from your windows. | | We've all seen plenty of windows covered with plastic film in an effort to reduce the drafts and thermal loss. Yes, that helps, but not much and not for long. Here's the Down & Dirty way to get past the inital problem: Cut plain white styrofoam panels to press-fit inside the header/jamb/sill of your windows. | | Right now I'm in northern Arizona at 6,500' elevation - pretty cold (like Flagstaff). Our home is being rebuilt - now half frame-house and half old mobile-home with single windows and very tired weatherstripping. It's hard to be comfortable in here when it gets cold. Worse, the heating is electric baseboards, and we can't afford to crank up the thermostat. Helluva note for a solar home designer, huh? |  | | Foam Shutters - Last week I went to the lumberyard and bought 2 sheets of 1" styrofoam (R4) at $7.49 per. Less than 2 hours later it was screwed over the wood window casing, and by time I'd finished, I was starting to sweat a little! Here's the numbers on that one:
about 60 SqFt of windows went from -R1 to
that R1 + R1 for a new airspace + R4 = R6.
Thus the window thermal loss went to 1/6 of original.
The styrofoam will pay for itself on the next bill. This is as "down & dirty" as it gets - fixed in place - but notice the light comes thru! | 
| | Most window openings are jambs allowing a press-fit. I don't see much harm in drilling a couple of 1" fingerholes in the styrofoam to make them easily removable. Normally it's best to use at least 1-1/2" - stronger and better R-value. Styrofoam is easy to cut with a serrated kitchen knife. If you heat the knife, it will melt thru the styrofoam like butter, seal the edges and avoid the little white pellets all over the house. You can get fancy (and increase the costs) by making a frame, weatherstripping, hinges, paneling, wallpaper, etc. You can probably find all sorts of commercial insulating shutters. We're just talking here about fast and cost-effective - I wouldn't know how to beat plain styrofoam for that! | | Draperies can help, heavy, line, foam-backed, etc. One thing to watch with draperies is convection - the up/down airflow across the windows will defeat most of their insulating usefulness. Most of that can be stopped with a box cornice. | | This page will get much updating, but this might get you thinking.... and acting! |
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