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Healthy Home
Heating
By Thomas
Hirsch
As
the temperature drops and we begin to spend more time indoors, we have
creature comfort needs to maintain a reasonable temperature.
The “Sick Building Syndrome” takes a strong foothold this time
of year. How we choose to
heat our homes determines both our comfort as well as the level of indoor
air quality. Let’s review a
few of the more common home heating options from the perspective of health
and sustainability.
Do
you remember Physics 101? Knowledge
of the three modes of heat transfer—convection, conduction and
radiation—will help you understand why certain heating systems are more
desirable than others. Convection
is heat transfer through fluids, in our case the fluid is the air in our
homes. Hot air rises. Air
currents are a natural result of this phenomenon.
Conduction is heat transfer through solids.
When we put our hand on a hot cup of tea or cuddle up with a loved
one, we experience conduction. Radiant
heat is the energy that comes from the vibrations of atoms.
It is a form of electromagnetic radiation called infrared.
This is the warmth we feel from the sun, a blazing fire or
old-fashioned radiators.
The
most commonly used system right now is a forced-air furnace.
There is a heat source, usually the combustion of gas or oil,
sometimes wood or coal, or even an electric coil; and a blower fan forcing
the warmed air through a distribution system of metal ductwork. While this system is often the least expensive heating option
to install, it scores the lowest on the green building/healthy home
checklist. The forced air is
heat transfer by convection. The
blower fan moves a large volume of air to get the heat distributed.
The on and off cycling of forced-air systems and the nature of
convection heat results in uneven heating throughout the home.
Metal ductwork accumulates dust and other toxins that circulate
into the air. Maintaining a
highly efficient air filter is a must for better air quality.
In low humidity situations, which is often the case in wintertime,
static electricity build up is a by-product of forced air through metal
ductwork. Indoor air pollutants like dust, dust mites, animal dander,
mold and VOC’s from synthetic building materials and cleaning supplies,
become airborne when there is static electricity buildup. Furnaces must have sealed combustion to avoid the entry of
combustion by-products into the air stream.
Radiant
heating systems are much more comfortable and have lower operating costs,
though often higher installation costs.
Old fashioned radiators, baseboard and in-floor radiant heat are
some examples of these systems. An
independent ventilation system like an air heat exchanger or heat recovery
ventilator (HRV) should be considered to introduce a continuous supply of
fresh filtered air.
Electric
heat is attractive because it appears clean and quiet.
However, electric heat systems will fry dust and create elevated
electromagnetic fields. They
are also much costlier to operate.
Heat
pumps, or geothermal systems, are not as efficient when temperatures are
below 30 degrees. They also
rely on electricity and freon, which is an atmospheric ozone depletor. The theory behind extracting heat from groundwater or the
earth is good, however, the technological requirements have a cost.
Because
of an abundance of firewood in our area of the state, woodstoves are a
popular form of radiant heat. Wood
stoves can by messy to operate. Most
of the heat escapes up the smokestack and more than 200 toxic by-products
of combustion can be introduced into the home air.
A well-maintained chimney and an airtight stove are important.
A
better way of heating with wood is a masonry heater.
Because of the large masonry thermal mass and the downdraft
contra-flow flue system, the fire burns hot enough of burn off many
combustion gasses and is so much cleaner.
Most of the heat is stored in the masonry mass and then radiated
into the home instead of up and out the chimney.
With so much retained heat, only one or two short, hot fires a day
are necessary, so they use very little fuel.
Initial installation costs, however, are much higher than for a
woodstove, but comparable to a masonry fireplace.
Passive
solar heating is one of the simplest and cheapest forms of radiant heat.
Heat from the sun passes through window openings and is stored in
building materials with high thermal mass capacity like concrete, brick,
stone and water. This stored
heat is then re-radiated into the space.
Because this system is weather dependent, an auxiliary heating
source is needed during extended cloudy weather.
Design elements need to be incorporated into the architecture to
fully utilize this misunderstood and underused resource.
Next month we will elaborate on passive solar design elements in
greater detail.
Choosing
a new heating system or retrofitting an existing one is much like
addressing the other components in our buildings.
There are choices, compromises and challenges that require some
thought and research. Wherever
you find yourself this winter, I hope you have a warm and healthy home and
heart.
Harmony
Home Construction, LLC.
8122 Barney Road
Traverse City,
Michigan 49684
Ph: 1-877-45-GREEN Fx: 231-932-9193
info@harmonyhomeconstruction.com
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