|
KEEPING
THE HEAT IN…OR OUT!…SOME
THOUGHTS ON BUILDING INSULATION
By Thomas A.
Hirsch
At this time of year, with the “dog days of summer” weighing
heavily upon us, insulating our homes is not given much thought.
For those of us currently absorbed in the building process or in
the building trades, this component of our work is vital given the fact
that the insulation becomes the living and breathing (or suffocating, as
the case may be) “flesh” of the house.
Human
beings have devised many ways to insulate buildings over the years.
Some work better than others do.
When considering the green and sustainable aspects of insulation,
we are required to take a deeper look.
Let’s review the more common, and not so common, possibilities.
Typically,
building materials are chosen based on cost, availability and perhaps some
technical attributes.
Insulation is no exception.
Making a decision solely on R-value (unit measure of thermal
resistance) and cost ignores some important considerations regarding human
health and the environmental ramifications of our choices. As we build our
homes, we seldom consider the damage to the environment caused by the
manufacture and disposal of synthetic insulation materials.
Nor do we think of the health risks for those installing these
materials or the long-term impact on indoor air quality and our own
health.
The
cost of insulation is a small part of a total construction budget, so
choosing a safer and more effective material usually make sense in spite
of higher initial costs.
Some of the benefits of careful insulation choices are: fewer
contributions to global warming, less pollution from the generation of
electricity, less contamination of ground water and a much improved indoor
air environment in your home.
Fiberglass
is probably the most common residential insulation product used today.
Even though it can be made from recycled glass, the fibers are
easily embedded in the lungs and may be carcinogenic.
Phenol formaldehyde and asphalt adhesives (used in the paper
backing of fiberglass batts) are known toxic petrochemicals and suspected
carcinogens.
Mineral wool or slag wool is more common in older buildings and is
becoming popular again, but has the same problems as fiberglass.
Cotton
and wool insulation properly installed are good choices. Be sure non-toxic
fire retardants have been used.
Silicate foam or Air Krete is cementious foam insulation made of
magnesium oxide extracted from seawater plus calcium and silicate.
It is one of the least toxic insulating materials on the market,
though still a bit costly.
Higher initial costs are off set by higher R-values and tight
fitting draft prevention.
There
are several rigid and sprayed in foam insulations composed of a number of
questionable petrochemicals.
Avoid these if at all possible.
Read the Material Safety Data Sheets (MSDS) and the available
research and you’ll see what I mean.
Another
good choice is cellulose, which is made predominantly of recycled
newsprint.
It has an excellent R-value, low cost and low embodied energy used
in production.
Be sure to check that non-toxic fire retardants are used and make
sure that installations are as dust-free as possible, once contained.
There
are several natural building systems incorporating straw bales,
straw-clay, wood-chip-clay, cob (load-bearing heavy clay and straw walls),
rammed earth, adobe and even cordwood, all having years and even centuries
of proven integrity.
Many of these buildings around the world have been continuously
inhabited for centuries.
Some of these techniques are gaining in popularity among
sustainable and green building circles.
An upcoming article will be devoted to the virtues of these
systems.
Looking
at any of the above insulating materials in isolation is presenting only a
narrow and somewhat distorted view of how a building really works.
Knowledge of building science, or building biology, helps one to
understand how these materials work in a synergistic way with the rest of
the building.
Thermal performance of a building is not just solely dependant upon
the
R-value of building materials. Other factors related to construction type,
natural and artificial climate control systems as well as specific
qualities of materials like hygroscopicity, diffusion/ breathability and
thermal mass (ability of a material to absorb and retain heat.) all
contribute to this performance.
In terms of temperature and moisture (in the form of water vapor),
what is occurring within the exterior wall cavity is critical for the
longevity of the building and the well being of its occupants.
Our next installment will address breathing walls verses airtight
building methods.
This is a key factor in creating a healthy house.
Until then, happy housing!
REFERENCES:
The
Natural House Book: Creating a Healthy, Harmonious and Ecologically Sound
Home Environment.
David Pearson.
Fireside, 1989
Prescriptions
for a Healthy House.
Baker, Elliott and Banta.
InWord Press, 1998
Architectural
Resource Guide : Architects, Designers and Planners for Social
Responsibility.
David Kibbey (self published, 510-273-2428) 1998
Institute for
Baubiologie and Ecology, Clearwater, Fl. 727-461-4371
Correspondence
Courses, seminars, consultations and on going comprehensive work on the
interrelationship between the built environment, human health and
planetary ecology.
Harmony
Home Construction, LLC.
8122 Barney Road
Traverse City,
Michigan 49684
Ph: 1-877-45-GREEN Fx: 231-932-9193
info@harmonyhomeconstruction.com
|
