How to build an energy-efficient home
By Mr Jody Hudson
There are just a few important things to know and to remember, when
building an energy-efficient home. These are; insulation, air intrusion,
thermal mass, and that windows and holes in the wall of the house lose
about the same amount of energy.
Insulation is a means of capturing dead air and causing it to slow the
exchange of hot energy toward a cold space. Most builders use fiberglass
insulation. Personally, I prefer to use blown cellulose insulation. In
America, we major the value of insulation, by giving it an R-factor. The
R-factor of insulation is a reference for the ability of the insulation
to slow heat transfer and to the R stands for resistance factor. The
R-factor is only part of the story. Insulation can have a high R factor,
but if air moves through it is almost useless. One of the things we do
recently, in home construction, is to use Tyvek, a thin, breathable
plastic membrane that stops the wind. In modern construction; we
customarily have from the outside killing in; siding, Tyvek, insulation,
and drywall. Customarily this results in what we call and R-30 wall.
In other countries they talk about a U-factor. The U stands for use
factor. And this use factor is merely a combination of an R factor, and
an ability to withstand air intrusion. Therefore, the use factor is
actually more useful than strictly the R factor. For instance, a
concrete wall, has a low R factor and a high U factor if the logs are
made to fit tightly together. A concrete home has a low resistance
factor, because concrete transmits thermal energy easily. To properly
insulate a concrete wall, one should insulate the outside of the wall.
And this brings us to thermal mass.Windows are a great energy waster.
Each pane of glass has a resistance factor of less than one. A
thermopane window has a resistance factor of about two or three
including the airspace. The more windows a home has the more expensive
it is to heat. Triple pane windows have a resistance factor of about
five. A drapery fully covering a window will increase the resistance
factor to about 20. Therefore drawn draperies will greatly increase
the insulating ability of a home.
Thermal mass is simply the amount of weight that reaches a certain
temperature and wants to stay at that temperature. For instance, I home
with a brick floor, and lots of books and heavy furniture, has a lots of
thermal mass. Once a home with lots of thermal mass reaches a
comfortable temperature it tends to stay that temperature for a long
time, even after they heat or air-conditioning stops. Offices tend to
have high thermal mass. It takes a lot of energy to change the
temperature of thermal mass. Thus, one should leave the thermostat at
the same temperature and not move it up and down. Turning down the
thermostat at night and turning it back up during the day wastes energy.
Copyright 2004 by Jody Hudson, WWW.Kate-Jody.com and
WWW.JodyHudson.com
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