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(Reprinted
from SE Homebuilder & Remodeler Magazine)
BY GEOFFREY EHRMAN
Attic vents have evolved from a variety of products with limited venting
capability to ridge ventilation systems offering optimal performance.
Ridge ventilation completely and continuously bathes an attic with fresh
air. It is also highly effective in cutting energy costs and prolonging
roof life.
In the 1950’s and 1960’s, typical ventilation products included
gable vents, roof pots and wind-powered turbines which only work when
the wind moves in a certain direction. Attic fans, powered by electricity,
also came along during this period.
Some of these products look like smoke stacks; others resemble tin pots
sitting on the roof. Not only are they unattractive, but even their primary
purpose – getting heat out of the attic – is ineffective. The
devices only ventilate the defined area where they were installed, versus
properly venting the entire attic area.
In the 1970’s, as homeowners became energy minded, the timing for
introducing ridge ventilation was ideal. Ridge vents require no electricity
to run, only the natural flow of air. Since they are highly effective,
a home’s heating and cooling costs are lowered.
Early ridge vents were manufactured from galvanized metal or aluminum.
Still available today, they detract from the roof’s appearance as
they are still visible above the ridge line. Another drawback is that
they are prone to bending and denting during installation and severe weather.
The end of the 1970’s were more prosperous time which triggered a
surge in new home construction. Increasing numbers of homebuyers specified
more expensive architectural shingles, slate and cedar shingles, or flat
ceramic or concrete tile. A home’s appearance, or its "curb
appeal," became a key factor in marketing new and existing houses.
As a result, under-the-shingle ridge vent systems have become increasingly
popular since they maintain an attractive roof line. Its three-dimensional
nylon matrix allows air to vent through while keeping rain, snow, dust
and insects out [1]. A ridge vent is typically
packaged on a roll for ease and speed in handling and installation.
Installed along the length of the ridge line and under ridge cap shingles,
a ridge vent system properly ventilates the entire attic. Fresh air enters
the attic through soffit vents located beneath the eaves of the roof.
The air moves through the attic and exhausts out through the ridge vent.
This new generation of ridge ventilation is installed by rolling it out
over a slot cut in the ridge. It’s fastened beneath the ridge cap
shingles with 2-1/2 inch nails provided. No maintenance or cleaning is
necessary after installation which can be done in about a half-day by
a one-man crew.
A ridge ventilation system also can be installed on a flat ceramic tile
or flat concrete tile roof. The same installation procedure is followed
as with a shingled roof, but with these exceptions:
- Measure the width
of the cap.
- Subtract one inch
from that measurement. Use a ridge vent with a width that is closest
to the above calculation.
- Allow at least
a one-half inch over-hang for each cap over the ridge vent.
There are many benefits
to a proper ridge ventilation system. Prolonged roof life heads the list.
An improperly vented attic traps heat that can climb to temperatures as
high as 140 degrees. The roof deck then becomes so hot that shingles curl,
become brittle and can blow off exposing the deck to the elements. A ridge
vent system exhausts damaging heat by constantly drawing fresh air to
the attic, thus cooling down the roof deck.
Trapped heat can cause the roof deck as well as trusses and rafters to
warp and eventually rot and fail. Its impact also can be felt on cooling
and heating costs. Without proper ventilation, heat during warm months
will radiate down into the home’s living space, driving cooling costs
up.
In cooler weather, moisture from daily household activities rises to the
attic. Without proper ventilation, moisture will settle on rafters and
trusses causing them to warp or sag and eventually fall victim to dry
rot. Condensing on insulation, unvented moisture can reduce R-values by
one-third allowing heat to escape in the winter and air conditioning to
escape during the warmer times of the year.
Proper ridge ventilation will also effectively handle similar moisture
conditions created by humidity.
When the cold winds and storms of winter blow, a ridge vent system helps
reduce one of Old Man Winter’s biggest threats to roofing. By maintaining
a constant temperature along the entire roof deck, ridge ventilation prevents
ice damming.
When snow melts, it runs down a roof to the gutters where it can refreeze.
By constantly circulating fresh air along the roof deck, ridge ventilation
greatly reduces the differences in roof temperature at the ridge and the
eaves.
Damage caused by ice damming is not limited to the roof. Walls and structural
elements also are affected, compounding the potential overall repair costs.
Regardless of the season, an under-the-shingle ridge vent system gives
the home added protection and prolonged roof life. Homeowners also can
rest easier knowing that a proper ridge ventilation system validates shingle
manufacturer warranties. For the contractor, it makes installation quicker
and easier while creating an additional profit center that virtually eliminates
call backs.
[1] Roll Vent®
and Rapid Ridge® products are the only ridge vents that offer this
patented design.
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