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Passive solar heating can lead to aggressive savings

It won't be long before winter hits us again, and I promised myself last year that we'd do what we could to our home to make it more comfortable this year. It stayed cold indoors all last winter, and we hated it. You and others I read often talk about passive solar heating and how this is a great way to keep your home warm in winter without spending a lot of money on your heating bills. Can you please explain what this means?

I will. It's probably the oldest and the easiest way to stay warm in your home during even the coldest winters, but it does call for some remodeling or new strategies to take advantage of all the features this strategy offers.

If you're planning to build a new house, I strongly recommend that you work with your builder to incorporate passive solar design, but even if you just want your current home to be more comfortable, there are some things you can do.

The word "passive" says it all. Your home will keep you comfortable without needing mechanical, energy-using products like heaters or fans. And the passive home strategy also can be adapted to keep a home comfortable in hot weather as well.

The general strategy is based on the laws of physics that tell us that heat moves from hot to cold until there is no temperature difference between the two areas. In cold weather, you can use this principle to have the sun's warmth stored in your home during the day and then released in the colder evening. What makes this different from just a natural occurrence is that you do things in and to your home that facilitate the process.

An important part of the passive solar process is the concept of thermal mass - the use of materials within the home to store heat.

Examples include concrete, stones, masonry, bricks and tiles, all materials that are often found below or behind the surface of walls and floors in a home. There also are absorber materials that can be used in passive homes - exposed masonry walls, partitions or even large containers of water that are struck by sunlight and then absorb the heat from the sun.

Another component of a good solar home is some type of solar collector and large windows, especially located on the south side of the home with unobstructed exposure to the sun. The sun gets into the home through these windows and is able to reach the thermal mass or absorbers inside.

Once the heat is absorbed during the day, the next issue is how to get it to circulate through the home. Though some homes have mechanical systems like fans or blowers that help circulate heat released throughout the home, many homes are truly passive and just rely on the natural heat transfer modes of conduction, convection and radiation.

Finally, to help keep the process operating, passive systems usually include various types of sun controls. For example, blinds and outdoor awnings can be regulated to open when the sun is desired (usually between 9 a.m. and 3 p.m. in winter) and closed at other times to help keep the heat from flowing outdoors. Good roof overhangs will allow the lower winter sun to get indoors while keeping out much of the higher summer sun that can overheat the home.

As I mentioned, there are passive cooling strategies that primarily involve blocking the sun during the day in hot weather and opening up the home for nighttime breezes and cooler outdoor temperatures. One of the biggest advantages of both heating and cooling strategies is they don't use electricity- or gas-driven mechanical equipment to provide indoor comfort, greatly lowering your energy use.