Can You Convert Your Home to Passive Solar Heating?

In modern day America, most homes are heated with natural gas or electricity. Natural gas provides clean, inexpensive heat, which is distributed through the home by forced air. While electricity isn’t as cheap, it is distributed in a similar way. Either one will keep the family living in that home warm and comfortable.

These two forms of heating a home have something else in common; that is, if the power goes down, the home will be without heat. Considering how fragile the electrical grid is and that just about any disaster will cause power outages, that means that in the aftermath of any crisis, you can expect to be without heat in your home. You may be without heat for a few days, or you may be without heat for a prolonged period of time; it all depends on how much damage was done.

Considering that one of the major reasons we build homes is to protect ourselves from the weather, losing our capability to heat our homes negates a lot of the reason for having them. An alternate means of heating is needed, in order to survive any crisis.

For most, emergency heating plans require the use of wood. They’ll either heat their homes with a wood-burning stove or a fireplace. But that’s not the only option available. Some people may be able to heat their homes using solar power, simply by making some modifications to their home.

Granted, true solar homes are usually designed as such. However, that’s not to say that it’s impossible to convert a home to passive solar. Many homes can benefit from modifications to include at least some passive solar capacity. Depending upon the home, this may not even be hard to do. A lot depends upon having a south-facing wall which can be used.

Of course, most passive solar homes are designed as such from the outset. Because of that, most people think they can’t take advantage of solar heating. Yet, almost any home is capable of having at least some passive solar heating, with some modifications. The trick is in understanding how passive solar works and then looking at the home to see what can be done to make it more solar friendly.

A passive solar system consists of only five basic components. These are:

• Aperture or collector. This is a fancy name for the windows that the sunlight comes through. In the northern hemisphere, these windows have to be south-facing and can’t be covered by foliage. The closer to directly south that the windows face, the better, with 30 degrees off of south being the maximum possible angle.
• Absorber. The absorber is what the sunlight hits when it comes through the aperture, converting that light to heat. To be effective, the absorber must be a dark color and made of a material that will readily transfer the created heat into the thermal mass.
• Thermal mass. Once the absorber converts the light to heat, that heat needs to be stored somewhere. In a passive solar system, this is usually concrete or rock. The absorber is physically connected directly to the thermal mass, allowing it readily to transfer the heat.
• Distribution. A passive solar system absorbs heat during the day and releases it at night. This is accomplished by a combination of radiation and convection. The heat naturally radiates from the thermal mass to the surrounding air, warming it. Then, convection causes that warmed air to rise, heating other parts of the home. In some cases, ceiling fans may need to be used to assist with the convection process.
• Control. The control limits the ability of the sunlight to hit the absorber in the summertime, while allowing it to hit it during the winter. This is usually the roof overhang. In winter, the sun is lower on the horizon, allowing it to shine through the windows. In the summer, it is more directly overhead, where the control blocks it.

How Passive Solar Works

Before you can determine if you can modify your home for passive solar, you need to understand how it works. Basically, a passive solar heating system is nothing more than the sun shining through a south-facing window and heating up the carpeting on the floor. If you have a cat, it knows all about that warm spot on the carpet, created by the light of the sun.

In this case, the window is referred to as the aperture. It allows the light of the sun to pass through, collecting it for conversion to heat. The sunlight then strikes the floor covering, which absorbs it and converts it to heat. That is called the absorber. Ideally, the absorber will be black or at least a dark color, so that it can absorb the most possible heat. The absorber is connected to a thermal mass, which acts as a battery, storing that heat until it is needed. It then radiates the heat through the absorber into the home.

There is one other ingredient to a passive solar system, that’s the control. In most cases, the eaves of the home act as the control, preventing the light of the summer sun from entering through the windows and heating the home. In cases where the eaves can’t do that, a window shade or curtains are used.

How Different is this From Your Home?

There are probably a few differences between the passive solar system mentioned above and your home. First of all, you might not have enough windows. Most homes don’t have enough to effectively allow passive solar heating. However, windows can be added, assuming you have a south-facing wall that you can add them in.

The next difference is the lack of a good thermal mass. Most homes either have wood floors or a thin cement slab (4″ thick). To work as a thermal mass, that cement slab would need to be at least 8 inches thick, if not 12. The larger volume of cement is needed to store a larger amount of heat. Adding a thicker slab would mean taking out the existing one, excavating down below the floor level and pouring a new slab.

Finally, the other big difference is the absorber. It’s rare to find a home that has black floors. It’s even rarer to find a home that has black ceramic tile or stone floors. Lighter colored floors won’t work as good as black, as they won’t absorb as much of the sunlight.

Making the Conversion

While it’s possible to convert a normal home to passive solar, it’s not easy. Digging up a floor is a major project, which would be rather expensive. While replacing windows is not easy or cheap, adding the windows would probably be easier than adding the thermal mass.

However, there is an easier way to add passive solar to pretty much any home, that’s the addition of a sunroom. If your home is situated where you could add a sunroom behind your kitchen, opening up the wall so that the heat generated in the sunroom could get into your home, then you could add solar heating, fairly easily.

If you don’t have a south facing room which would work for converting to passive solar, you don’t have to give up. Another excellent option is to add a sun room or greenhouse room to your home on the south side. Both sun rooms and greenhouses are natural passive solar environments.

To make this effective, you’ll need to open the wall between the new addition and your existing home. So, if the best place to install it is off your kitchen, you’ll need to remove the wall between the kitchen and sun room. That may require some modifications to your kitchen, such as converting the kitchen counter to an island and removing the upper cabinets over it.

Of course, this wouldn’t be enough to fully heat your home through the coldest winter; but it would be an excellent source of heat, reducing the amount you need from other sources. It would also ensure that in a time of crisis, you would still have some heat in your home.