Friday, March 10, 2006

Keeping Warm This Winter

Dec 05/Jan 06 Grassroots Press Column:

Natural gas prices are substantially higher this winter than last year. This is likely to be a major hardship for many consumers – especially in colder areas – and will probably be a bigger problem than high gasoline prices. (Until gasoline prices go up again, which they eventually will.) Not surprisingly, many Americans are looking for alternatives to natural gas.
Wood heaters are the quick and dirty alternative. Wood heat is least obnoxious in the country, where houses are far apart and the smoke gets diluted. If too many people in urban areas start to heat with wood, the air will become unbreatheable. Solar heat is really the only sustainable choice.

Here’s how to keep your house as warm as possible, using the natural heat from the sun:
The largest potential heat loss is from air leaks. Leaks can be sealed with judicious application of caulk and weatherstripping. The best time to check for air leaks is on a cold, windy day, when drafts will be most obvious.

Windows can also lose a lot of heat. Replace old, ill-fitting windows with modern double-pane windows. These might seem expensive, but they’ll last a lifetime, and will pay for themselves by preventing unnecessary heat loss.

South-facing windows will allow sunlight (heat) in during the day, which is a good thing during the winter, but unfortunately they will let the heat right back out at night. In a well-insulated house, windows – even double-pane windows – will be the greatest source of heat loss at night, so it’s important to cover them at night with heavy curtains or foam inserts.
To make optimal winter use of your windows, try this simple plan: Cover the north and east windows with heavy curtains or foam inserts, 24/7. During the day, leave the south windows uncovered. Uncovering the west windows in the afternoon should let in some of the warm afternoon sun. Many houses aren’t oriented exactly along a north-south axis, so you might need to modify this prescription to fit your situation.

The trick is to heat your house as much as possible during the day, using free solar energy. This is no problem for people who are gone all day. People who are home during the day might find indoor temperatures uncomfortably warm, depending on the number of south-facing windows. But bear in mind that what you’re doing is soaking the contents of your house with heat. The contents of your house serve as thermal mass -- a heat reservoir. The more heat stored by the thermal mass during the day, the more heat will be released at night, when you need it.
When the sun is no longer shining into the windows, close them off with curtains or foam inserts, to prevent nighttime heat loss.

Here’s another way to look at it: a house is like a battery. You charge it up with heat during the day, and then it slowly discharges its stored heat all night until you charge it up again the next day. Uncovered windows "short-circuit" the stored heat into the cold night air, which is why it’s important to cover them at night.

Doing all this rigmarole might seem extreme – it’s certainly not the standard American way of doing things -- but it's really not all that big a deal. Ideally, you might get away with not having to use any additional heat during the evening hours, and minimal heat at night. This can cut your heating bill substantially.

The next step beyond optimal use of your windows is to build a solar heat collector or collectors onto the south wall of your house. This will greatly increase the amount of solar heat entering your house.

The concept is simple: paint a south-facing surface black. Build a wooden framework around the black surface, and cover with some transparent material (plastic, fiberglass, or glass) to collect the hot air. What you’ve got is a sandwich – black surface on one side, transparent membrane on the other side, and an air space in the middle. The trick is to get the hot air into your house. Ideally, a solar heater would have an opening into the house at the bottom to let in cold air, and another opening at the top so the hot air can flow into the house. With most houses, the easiest way to handle the air flow is to use existing windows. Every house is different, so I can't give more than the basic concept here, but solar heaters are cheap and simple.

A solar collector is a three-part sandwich: transparent membrane, air space, black surface. The sun shines through the transparent material onto the black surface (which can be the wall of your house painted black). This heats up the air in the air space. Since hot air rises (just like a hot air balloon), an automatic convection cycle gets started -- hot air gets forced out of the top vent into the house, and cold air from the floor gets sucked into the heater where it is quickly converted into hot air. The operation is absolutely silent. Not a whisper. Within a few hours, such a heater can turn a stone-cold room into a dry sauna.

We are fortunate to have such abundant winter sunlight in the Southwest. It costs nothing, and is pollution-free. It’s an elegant way to avoid paying outrageous natural gas prices. Like the El Paso Solar Energy Association says, "The answer comes up every morning."

(When building a solar heater, Gordon Solberg recommends listening to the Rolling Stones’ "Paint It Black.")