Q: 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?
A: 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 your comfortable without needing mechanical, energy-using
products like heaters or fans. And the passive home strategy can also
be adapted to work well in keeping 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 are also 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
the heat that is 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 also 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 that they don't use electricity- or
gas-driven mechanical equipment to provide indoor comfort, greatly
lowering your energy use.
Even if you don't want to build a sunspace off of
your living room or put a masonry wall near your fireplace or have new
skylights put in your bedroom, you can still take advantage of the
general passive principles by regulating how the sun gets indoors by
using inside blinds, shades and drapes as well as outdoor shading
devices.