Passive Solar Heating for Survival

As we all know, being able to maintain our body’s temperature is the number one priority for survival. To do this, we count on a combination of shelter, clothing and the ability to produce heat, mostly through fire. But there are other ways of producing heat; specifically by using the power of the sun. While most of us look to the sun to provide electrical power, few bother going beyond that, especially to the area of solar heating.

I realize that it seems a bit strange to be talking about heating in the summertime, when we really don’t have a need for it. But the summertime has always been the time when mankind has planted crops, tended flocks and cut firewood, so that they would be ready to survive the next winter. For us today, it’s the time to do outdoor projects, which can’t be done when the snow is falling.

Solar heating is not a new concept, although interest in passive solar heating has only existed in our country for about 50 years. Nevertheless, greenhouses, the original passive solar structures, have been around for almost two millennium.

Typically, solar homes are something rather esoteric, built only by environmentalists who want to lower their carbon footprint and be one with nature. But that doesn’t in any way reduce their utility or efficiency. As survivalists, passive solar homes offer us something we can’t get anywhere else, free heating for our homes.

Most passive solar homes are specially designed and built to be solar, which tends to make the rest of us think that we can’t utilize passive solar for our homes. But the reality is, if you have south-facing window, you already have some passive solar capability; all you need to do is increase it.

Sunlight coming through your windows and striking the floor generates heat. How much heat it generates depends on the amount of sunlight, whether you have tinted or otherwise coated windows and the color of your floor. Dark floors are the best, as they absorb the most light, converting it to heat.

In a true passive solar home, the floor is made of dark-colored stone or is attached to a thick concrete slab. This is referred to as the “thermal mass” and acts as a huge battery for heat. During the day, the sun striking the floor creates heat, warming that thermal mass. At night, when the ambient temperatures in the home is lower than that of the thermal mass, that heat is radiated into the home.

The hard part in turning a normal home into a passive solar home is in creating this thermal mass. If your home is built on a cement slab, you have some thermal mass, but not much. However, even without the thermal mass, you can still gain something from passive solar. If the sunlight manages to warm your home during the day, the home’s insulation should keep most of that heat inside at night.

So what can we do to generate more heat from the sun? There are two things. First of all, the more window area you have, the more sunlight can get into your home. So adding more windows or replacing windows with larger ones, will increase the amount of solar heat you are producing.

Skylights are another way of increasing the amount of sunlight that gets into your home. This is actually better in the south, where the sunlight is more directly overhead, than it is in the north. Properly installed, facing south, the sun from skylights can strike the floor of your home, adding to the heat generation from the sun.

There is a bit of a tradeoff here. Windows are notoriously inefficient as insulation. So adding more window area means that you are lowering the insulation value of the home. In order to counter that, you’ll want double or triple pane windows, as well as thick curtains to cover the windows at night.

The next thing you can do to increase the solar heating ability of your home is to replace floor coverings with ones that are dark. The darker the better. If you can’t afford to change all your carpets or other floor covering, then buy some dark colored rugs and place them where the sunlight will hit them. That will do the same thing.

But probably the best thing you can do, to add passive solar heating to your home, is to build a sunroom on the south side of your house. A sun room is by definition a passive solar structure. So adding a sunroom to your home greatly increases your ability to heat with solar. Just make sure that the sunroom is connected to the home with a wide open space, allowing air to flow back and forth between the sunroom and the rest of the house.

Be sure to build your sunroom with a large thermal mass under the floor as well. While making that all out of concrete is expensive, you can save money by creating a bed or rock and then pouring the concrete between and over the rock. That will bond the two together, making the rock into part of the thermal mass.

That sunroom can also serve as an indoor greenhouse, allowing you to grow miniatrue fruit trees and other produce on a year-round basis. Even if it isn’t big enough to feel your family entirely, it can be a help.

While a sunroom and these other improvements may not fully heat your home, they will help. Every little bit you can add to your home’s passive solar heating, is one little bit less wood you will have to chop and haul to heat your home, when an emergency comes. It seems to me that that’s worth the effort.

So, take a look around your home and see what you can do to increase its passive solar capability. In the mean time, keep your powder dry and your survival gear close at hand.