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from Natural Life magazine,
July/August 2009
Building Your Sustainable Home
Applying the principles of Leadership in Energy and
Environmental Design (LEED) to your new home
by Hugh Perry
Part Six: Indoor Environmental Air Quality
There is an important balance between indoor air quality and the previously
covered LEED category Energy and Atmosphere. Such a balance results in a healthy
home that is environmentally friendly and less expensive to manage. The
following headings give an overview of how the construction industry is
approaching indoor air quality.
Manufactured Contaminants
Contaminates that migrate into your home undetected are a
major concern. Carbon monoxide from adjoining garages is a major source of
polluted indoor air. Therefore, contractors are being advised to keep the garage
under negative pressure by installing exhaust fans that are triggered by motion
detectors, open able doors or carbon monoxide detectors. Such a fan should draw
from close to the floor, as this gas is heavier than air.
There are recommendations that all penetrations into occupied
space be sealed and additional sensors be placed on every floor of the house. Of
course, a better way to deal with this health hazard is to have a detached
garage, or no vehicle at all.
If wood burning appliances are installed, the chimney is to
have a back-draft pressure differential test performed to expose leaks in the
flue installation. This test will also help prevent potential energy leaks where
conditioned air would otherwise escape when wood burning equipment is not in
use.
The workshop is another source of contaminates that should be exhausted
separately. The commercial sector regards the common photocopy space to be a
source of contaminates and should be exhausted directly outside with the space
being kept at negative pressure so odors do not migrate to office space areas.
This would be a consideration on a smaller scale for the home office.
As I mentioned in the article on Energy, it is important to
use low-emitting materials through out the home, including adhesives, composite
woods, finishes and cabinets.
Natural Contaminants
In some locations, radon gas can seep into basements and LEED encourages its
avoidance by “resistant construction techniques” such as ventilation through the
gravel below the concrete floor.
Another consideration is good return air from each room when the door is
closed. This ensures complete ventilation throughout the home. LEED recommends
that there be one thermostat per floor for forced air systems and individual
room thermostats for hot water systems.
The recommendations for outside air on continuous operating systems vary on
the size of the home and number of occupants, with the minimum of one complete
air change every two to four hours. Presently, Heat Recovery Ventilators (HRVs)
operate on controls from washrooms or on humidity control, which in winter is
seldom activated. Considering the average work schedule and washroom uses, the
average house sees at least one air change per day. Symptoms of tiredness are
good indicators that more oxygen is needed.
Moisture content is an important consideration for many reasons besides mold
growth. The ideal level for comfort is thirty-five percent moisture, which is
difficult to achieve in areas with cold winters. In summer, sixty percent is
considered the maximum desirable level. Humidity holds heat and, therefore, the
higher the percentage in winter the less heat we need for comfort and conversely
in summer.
In terms of filtering the air circulating within the house, a minimum
efficiency rating value (MERV) of 13 is recommended for air filters.
Contaminant Control
During construction, good indoor environmental air quality practice requires
the prevention of dust – particularly drywall dust – from entering ductwork.
This is accomplished by tightly sealing all openings and wrapping air handling
equipment. Operation of such equipment should be avoided until all painting,
millwork and floor finishes are complete.
Before moving into the building, flush the space by operating the furnace and
exhaust fans for at least forty-eight hours with all the windows open
(additional fans may be required). This is intended to remove the build-up of
off-gassing materials.
For people with allergies to plants, LEED aims to prevent natural pollutants
being transported into buildings by people and pets. So landscape professionals
should be advised to avoid the use of seed producing plants at entrances. In
addition, hose bibs should be at entrances for cleaning away pollen and leaves
when necessary.
Those wanting to leave natural pollutants at the door could also consider
permanent mats for approximately a meter at entrances, or a vestibule complete
with adequate shoe storage and a bench to encourage shoe removal. Related to
this is ensuring that there is a central vacuum system and that it is vented
directly to the exterior.
Innovative Design
There is one more important category in LEED, which is referred to as
Innovative Design. It becomes both the first step in the process and the last.
To take advantage of the guidelines that the Green Building Council provides
requires conscientious planning in the design stage, monitoring during
construction and training for the occupants.
There are also points allotted in both commercial and residential programs
for Awareness and Education to the public. Owners are encouraged to promote
their building as examples of good construction practices.
This completes our overview of changes being made in the construction
industry that will lead home builders and buyers closer to sustainability. I
hope that this series will be used as an aid to new home buyers in understanding
LEED. I also want to encourage prospective custom home owners to get involved
with the design team as knowledgeable partners and to provide insight as to the
sustainable possibilities for renovations.
Learn More
U.S. Green Building Council
Canada Green Building Council
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