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Over the past two decades significant advances have been achieved in home
building technologies and materials. One important result of these improvements
is that today's homes are better sealed against air leakage than ever before.
While careful air sealing offers a number of important benefits to the home's
occupants, it can also cause indoor air quality problems if not combined with
proper ventilation. An R-2000 home effectively combines air sealing with continuous
ventilation, assuring the homeowner of lower energy bills and better air quality.
The principle objectives of air sealing are to minimize heat loss by reducing the
uncontrolled leakage of air into and out of the home, and to make the home more comfortable
by reducing drafts. A house can be well insulated but if it is not properly sealed against
air leakage, it will lose a significant portion of its heat (30% or more) during the heating
season through cracks and crevices in the building shell (outer walls, floor and roof.) In
addition, if warm, moist indoor air leaks into the building shell, it can cause condensation
damage to the insulation and structural components of the house. Such moisture can also
cause mold and mildew, which have both aesthetic and health concerns.
Ventilation is needed to provide a continuous supply of air inside the home and to vent
stale indoor air to the outdoors. Fresh air is also required for any combustion appliances
that are used in the home (oil or gas furnaces, gas stoves, fireplaces, etc.) A regular
exchange of household air is essential for ensuring good indoor air quality and a healthy,
comfortable living environment for the home's occupants.
Frequent air exchange ensures that pollutants commonly found in household air are removed
from the home. Indoor air pollutants are substances found in the air that present an irritant
or a health risk to the occupants. They range from colourless, odourless gases to cooking
odors and tobacco smoke. Every house has some measurable level of indoor air pollutants,
including R-2000 homes. A brief description of some common indoor air pollutants is provided below:
Radon
This is an odourless, colourless, radioactive gas generated from the decay of
radium, a naturally-occurring mineral in the earth's crust. It enters the home due to air leakage
from the ground or rock beneath the home, from well water or from construction products such as
concrete or masonry.
Formaldehyde
This is a strong-smelling, colourless gas which is often a component of glues used
for making plywood, particle board and textiles. It is also found in smoke. Common sources in the
home are the materials used for construction, but formaldehyde may also be present in furniture or
fabrics. Both phenol formaldehyde and urea formaldehyde are used in wood products adhesives. Phenol
formaldehyde products are water-resistant and release very little formaldehyde. Most plywood’s use
phenol formaldehyde. Wood products using phenol formaldehyde in their adhesives are approved for
outdoor use and can also be used indoors.
Urea formaldehyde products, on the other hand, are intended for indoor use only. When
exposed to water, urea formaldehyde wood products swell. These products emit more formaldehyde gas than
phenol formaldehyde products. It is therefore recommended that all surfaces of manufactured wood products
that do not meet low emission standards (E-1 European Standard, ANSI A208.1-1993 table B standard or HUD
standard CFR part 3280.308) be sealed with a low-toxicity sealant.
Carbon Monoxide
This is a colourless, odourless, tasteless gas released during combustion. It can be
generated in the home from any number of sources, including fireplaces, woodstoves, unvented gas
appliances and from attached garages.
Particulates
These are particles capable of being inhaled into the lungs. They are found in tobacco
and wood smoke, and dust, and can also be generated from unvented combustion appliances and some humidifiers.
There are basically two ways to improve the air quality in a house. Reduce or eliminate the source of the
air pollutants and reduce the effect of the pollutants by better ventilation. An R-2000 home can do both.
In an R-2000 home, construction and finishing materials can be selected that produce little or no air
pollutants. However, this is a relatively new area and only in recent years have researchers begun to
better understand the causes and effects of air pollutants in a house. The result of such research has
led to the development and manufacture of more environmentally-friendly products that can be selected for
use in your home. R- 2000 builders can discuss the options available to you before and during the construction
stage of a new house.
It is important to note that these pollutants, if present in moderate amounts, can be controlled through proper ventilation.
A regular exchange of household air can also reduce humidity and avoid excessive moisture problems. Too
much moisture in a house can cause health problems and other concerns, such as condensation on windows.
These can be minimized by effective ventilation.
In homes that are not properly sealed, ventilation occurs "accidentally" as a side-effect of uncontrolled air
leakage. However, such accidental ventilation is very inconsistent, and any value it offers in terms of air
quality is more than offset by the problems that can be caused by uncontrolled air leakage (e.g. heat loss,
drafts and condensation damage in the building shell.) A much more reliable approach is controlled ventilation.
The need for controlled ventilation is particularly evident in an R-2000 home. Careful sealing against air
leakage is one of the key factors that sets R-2000 homes apart from conventional houses. Combined with high
levels of insulation, a continuous air barrier (which is tested as part of the R-2000 certification process)
creates a virtually air-tight environment in which heat loss and energy costs are minimized.
To address the need for controlled ventilation, R-2000 homes are required to have a heat recovery ventilator
(HRV) - sometimes called a "fresh air machine" - that delivers a continuous supply of fresh air to the house.
This system also vents stale, humid indoor air, along with household pollutants, out of the home.
HRVs extract heat from the outgoing stale air and use it to preheat the incoming fresh air. The stale
air is then exhausted to the outdoors. As a result of this simple and proven process, significantly less
energy is required to heat the incoming air to room temperature.
Studies have confirmed that such mechanical ventilation systems keep levels of common air pollutants
consistently lower in R-2000 homes than in conventional houses. This is just one way in which R-2000
homes ensure a comfortable, healthy living environment and give their occupants maximum control over
that environment.
For further information on R-2000 homes and technology, please contact us!
(From ISBN: 0-662-61158-6 Cat. # M92-81/3-1994)
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