Roof top
ventilation,
which is
technically
attic
ventilation,
is a
highly
important
element
of
roofing.
Proper
ventilation
will
increase
the
longevity
of your
roof.
Poor
ventilation
will
vastly
shorten
the life
of the
materials.
We see
this
scenario
daily,
roof
systems
failing
far
short of
the
material
life
expectancy.
Had a
very
small
investment
been
made
when the
roof was
installed,
adding
proper
ventilation,
the roof
would
have
lasted
much
longer.
Proper
attic
ventilation
will
extend
the life
of a
roof
along
with
reducing
problems
as it
helps
balance,
or
minimize
the
temperature
differential
between
the air
in the
attic
and the
air
outside.
Simply
stated;
Proper
ventilation
will
remove
moisture
and heat
from the
attic.
Details
of
problems
from
poor
ventilation
Trapped
moisture
and heat
can
raise
energy
costs by
putting
a load
on your
AC. It
can also
cause
damage
to
the roof
system
and
structural
components.
Not to
mention,
personal
items
stored
inside
the
attic
where
temperatures
can
easily
reach
150° F
(65° C).
Trapped
moisture
(more of
a
concern
in humid
regions)
causes
condensation.
Condensation
that
forms
inside
an attic
can come
from use
of tubs,
showers,
washing
machines,
clothes
dryers
dish
washers,
etc. In
extreme
cases
condensation
can be
bad
enough
to be
mistaken
for a
leaking
roof.
Other
Condensation
Concerns
Deck
Deflection
the deck
of the
roof can
warp,
deteriorate,
become
spongy (soft)and
very
dangerous
to walk
on. The
adhesives
used in
the
plywood
can
deteriorate
or Dry
Rot.
This can
happen
happen
over the
course
of
several
years,
extreme
cases
can
develop
this
problem
in as
little
as two
years.
This
occurs
because
one side
of
plywood
decking
/
sheeting
needs be
able to
"breathe"
by being
exposed
to
circulating
air....no
circulation
combined
with
condensation...wood
cannot
"breathe"
Rust;
In humid
regions
water
vapor
condenses
first
metal
inside
the
attic;
nails,
plumbing
straps,
straps
holding
duct
work
etc. Any
uncoated
metal
will
rust
over
time,
this
could
cause
the
metal to
deteriorate
to the
point of
failure.
Rusted
straps
on duct
work
could
break
allowing
it to
fall on
ceiling
joists,
or worse
yet,
through
a
suspended
ceiling
or
drywall.
Mold,
Mildew,
Fungi;
While
the
health
concern
regarding
mold has
yet to
be
medically
proven,
mold,
mildew
and
fungi
WILL
cause
dry rot.
Dry rot
does not
not
remain
in a
localized
area, it
will
spread
and
damage
any
lumber
that is
effected.
Material
Deterioration
Roofing
materials
are
exposed
to
extreme
elements
on the
outside.
Manufacturers
of the
materials
have
accounted
for the
elements
and
constructed
the
materials
accordingly.
Extreme
elements
from
under
the
materials,
the
attic,
will not
only
break
the
materials
down
prematurely,
but
could
also
void the
warranty
from the
manufacturer
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Optimum
Ventilation
Proper
ventilation
of a
roof is
obviously
crucial.
There
are a
numerous
types of
attic
vents on
the
market,
some
better
than
others.
What is
important
is the
components
of the
ventilation
system.
Without
the
proper
components,
the best
vents on
the
market
will be
ineffective.
Following
is a
break
down,
simplified,
explaining
the
workings
and
components
of
proper
ventilation.
Optimum
ventilation
systems
consist
of two
types of
vents.
-
Intake
vents,
located
at
the
underside
edge
of
the
roof,
known
as
the
eaves.
These
vents
allow
fresh
air
to
flow
in
the
attic.
-
Exhaust
vents
located
near
the
ridge
(top
crest)
or
directly
on
the
ridge
line
of
the
roof,
depending
on
the
vent
type.
These
allow
the
air
to
leave
the
attic.
Both
Intake
and
Exhaust
vents
MUST
be in
place,
and
unobstructed
in order
for the
system
to work.
Properly
implemented,
the
system
uses the
natural
forces
of wind
pressure
and
thermal
effect,
referred
to as
the
"Stack
Effect"
to
circulate
and
exhaust
the air
in the
attic.
The rule
of thumb
is that
properly
vented
attic
air
should
never be
more
than 15
degrees
hotter
than the
outside
air. A
temperature
difference
of
greater
than 15
degrees
is an
indication
of
additional
heat
sources,
and/or
an
indication
of poor
attic
ventilation.
As
illustrated
in the
drawing
above,
the
desired
circulation
of the
air is
along
the
bottom
of the
sheeting.
Therefore
the
optimum
system
will
draw air
into the
attic
from the
eaves of
the roof
through
soffit
vents.
Circulate
the air,
removing
condensation
and hot
air up
the
entire
length
of the
sheeting,
and out
through
the top,
or ridge
of the
roof.
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Vent
Types
There
are many
different
types of
roof
vents on
the
market
today.
Following
is a
brief
example
and
explanation
on
different
type
vents.
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