I have a 30 year old split level that was never ventilated in the
attic. The #1 recommendation seems to be inserting styrofoam true
vents into the eaves (over the insulation) along with a ridge vent.
It is my understanding that ideally, this will keep the attic
temperature roughly at par with the outside temperature. Better for
the attic, shingles, etc? Presumably this will allow my house to cool
off a little better in the summer?
My main question - will allowing for greater ventilation in the attic
have any effect on the cost of heating my house?
Location - east coast of Canada.
Or, to be more complete; if the barrier between the living space and the
attic is so poorly insulated and sealed that ventilating the attic has a
effect on your heating bills, then you're already loosing so much heat
through the top of the house that you need to add insulation there anyway.
Ridge vents are good but easier is a square roof vent. Do you mean you
have no vents at all? Does attic wood look dark and moldy ? You will
increase heat loss is you don`t have very good insulation. What is
your attic insulation, what are your winter temp lows. The attic
should be vented to keep it near outside temps to avoid condensation.
email@example.com (m Ransley) wrote in message
There is no venting at all. The previous owner told me that there was
venting in the eaves, but if there is there are no holes in the soffit
to allow air through. A friend who is a contractor looked over the
attic, and told me that there was no problems - no sign of mold or
previous condensation problems. I'm just looking to give it a long
life and bring it up to more modern standards. It could also use a
little more insulation, but I want to put in the true vents first.
Winter gets pretty cold here - east coast of Canada.
firstname.lastname@example.org (HA HA Budys Here) wrote in message
Following that logic, it doesn't matter if it's 10 degrees outside or
50 degrees, the cost of heating or cooling a house will always be the
same, because the house is insulated.
There's no question that proper attic ventilation will reduce cooling
bills. One big difference is the hot air is gone when the sun goes
down, not trapped there for hours to slowly cool overnight.
For the OP, you do realize that you need soffit vents in addition to
the stryfoam chutes, right?
Dave: IIRC the recommended CMHC (Canadian Mortgage and Housing Corp) venting
for wood frame construction is 0.3 percent of the area.
In other words if say your house is 25 feet by 40 (1000 square feet) you
need a 'Minimum of 3 square feet of venting. The guide also says "Venting
must be distributed so as to ensure cross ventilation". It does not say you
must have ridge vents. Over some 30+ years, to this house, we have added
additional ceiling insulation and also additional venting along the soffits
(bottom of the eaves). All extra to the original vents in the two gable
ends. Anyone who adds insulation is always warned, be sure not block any
It occurs to me that you must have an excellent vapour barrier, on the warm
side of your ceiling insulation, now. Other wise, every bit of warmed and
therefore moist house air that escapes up to the attic can condense up
there and you can get mould, rot and possibly wet ceiling insulation. We
have seen posting on this type of group about attic condensation problems.
In one case someone said they had 'toadstools' growing up there on soaking
wet roof rafters! Very expensive!
Email me if you want to discuss some more. We are in eastern Canada also.
Terry in Torbay Newfoundland. Not as cold as many places in North America
but cold enough and on a cold stormy winter night; "Me son she can blow some
PS. Page 104; Canadian Wood Frame House Construction, "For both pitched and
flat roofs it is important to provide adequate ventilation of the roof space
above the insulation. Even where air and vapour barriers are used some
moisture will leak (up) around pipes and other openings (e.g. light
fixtures) and through the vapour barrier itself. If that water vapour is
allowed to accumulate in attic spaces and/or under flat roofs it is likely
to condense in cold weather in sufficient quantities to cause damage.
................. etc. etc. .............................. the most
practical way to remove the vapour is by ventilation.
BTW we were very careful with that ventilation aspect when building our
first house, with a partially vaulted ceiling, 43 years ago. That house is
still in good shape with its fourth owner. One of the intermediate owners
blocked off some of the crawl space vents I had carefully installed in that
first house and fairly quickly had moisture and damp problems! Its amazing
how people don't understand the concept of warm moist air condensing in the
cold; one only has to breathe out on a cold day to see the moisture in one's
breath alone. Anyone know the typical amount of moisture each of us breathes
out while we sleep. I think it's like a pint or a litre per night, or
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