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Frequently Asked Questions (FAQ's)
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What is the real story about roof ventilation?
Proper ventilation in roof structures is most easily
demonstrated by an attic space that has vent holes along the eave, in the gable
ends, and with newer designs, along the ridge of the roof. As a responsible
roofing contractor we recommend adequate ventilation with your roofing system.
Local building authorities have not enforced ventilation
codes even though it has been required by the Uniform Building Code (UBC) all
along. Outside our high altitude region ventilation is considered a vital part
of the structure. In the higher elevations of the Sierras it has not had
much importance until the past few years.
The primary purpose of ventilation has been to dissipate
humidity and resultant condensation. Fortunately, we are in such a dry climate
so excess humidity and condensation have not posed much of a problem. Up until
the past several years few occasions have been found where the lack of
proper ventilation has resulted is problems. Properly installed shake and
metal roofing have been successfully.
Ventilation has become the buzz word over the last ten years
because of the new generation composition shingles. Composition shingles
(as differentiated from 'asphalt' shingles of old) require ventilation for an
entirely different reason than before. Composition now shingles require
ventilation because they need to expand and contract with their plywood
substrate uniformly. This is achieved with "flow-through"
ventilation. Flow-through is provided when cool ambient (outside) air flows in
under the plywood deck at the eaves (bottom) and flows unimpeded up to the top
of the attic space, then is vented out of a continuous ridge. This bathes
the underside of the plywood with outdoor air and allows the shingles and
plywood deck to expand and contract at the same rate.
Absent this ventilation under composition shingles, the
plywood and shingles expand and contract at different rates. The results
can be catastrophic. Shingles will be the first to give as the new
generation shingles (lacking the flexible asphalt in earlier shingles) will
crack. This has become widely known in the industry in the past decade.
This is why virtually EVERY shingle manufacturer requires adequate ventilation
under their roofing for proper installation. Inadequate ventilation can
invalidate shingle manufacturers' warranties.
How do I ventilate my roof?
Since so few roof structures in the area are not properly
ventilated, we recommend the structure be examined for ventilation.
If your home has an attic space, retrofitting a ventilation system is a very
affordable and worthwhile enhancement.
If your home has a vaulted ceiling and no existing
ventilation system, retrofitting of a ventilation system is a very costly
endeavor, often half to two-thirds again the cost of re-roofing. Existing
structures without ventilation have worked fine with metal and wood shake and
wood shingle roofing for over a century here. Although ventilation is good
to have, the consensus is to forego retrofitting a ventilation into the roof if
you use metal or wood roofing on these structures.
If you are considering composition shingles, it is highly
advisable to have a retrofitted vent system. In fact, the shingle
manufacturers consider this to be part of their installation requirements,
necessary for the proper function of the new generation shingles.
Since every design of roof is different, each must be
reviewed individually. Ask Tahoe Roofing Company to conduct a survey of
your roof and provide recommendations.
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