Every home or building should have some form of mechanical or passive
ventilation, whether inside the home, or in the attic. The question
remains: how much ventilation do you need?
The general rule is: ventilate only as required to solve or alleviate
a problem, rather that ventilating for it’s own sake. For example,
many older homes have survived without a bathroom fan or range hood. Some
other older homes have never had roof ventilation (roof vents) and have
never had any mold or mildew problems. The amount and type of ventilation
required depends on many factors, such as lifestyle, type of heating system,
building style, air tightness, and number of inhabitants.
The effective operation of a bathroom fan depends almost entirely on
the quality of the installation. We have often said that even an inexpensive
fan can be made to operate at maximum efficiency with a quality installation,
while an expensive fan cannot be made to operate at maximum efficiency
with a poor installation. We always recommend that homeowners examine
the features of a bathroom fan closely because you only need to install
a good fan once!
All our fans are installed in the following manner:
1] the fan housing’s holes and air leakage points are sealed with
2] the ductwork is rigid;
3] the joints are sealed and screwed;
4] the ductwork is routed, in the shortest run possible, to a roof
exhaust cap with damper;
5] the ductwork is insulated with “slip-on” insulation
sleeve, or sprayed with foam insulation;
6] the ceiling penetration is air sealed with one-part foam
7] for long runs of ductwork (over 3 LF) we use a “vibration
8] for some fans we will install in-line backdraft dampers to prevent
cold air “spillage”
For more info:
Kitchen range exhaust hoods
A well-operating kitchen range hood should exhaust un-wanted (ie.
Burnt?) food and cooking odours, excessive moisture and humidity
heat generated by cooking. The same rules for proper installation
range hoods as bath fans.
Much emphasis has been placed on the 300:1 attic ventilation rule.
That is, one square foot of ventilation for every three hundred
of attic. The merits of this “rule” are under some
intensive debate and discussion in the industry. For example,
how do you measure
effective attic ventilation? How important are the soffit vents?
We feel that attic ventilation should only be required in the
summer, when the sun’s radiant rays generate excessive heat
in the attic. Ventilation is required merely to exhaust this hot
that the colour of your shingles and the amount of shading will
be the prime determining factors of how much ventilation you will
how long the shingles will last.