I have a couple of questions regarding attic ventilation and ice dam
prevention:

My house is a cape cod style, which presents a challenge. In the upper
attic there is plenty of loose insulation, but it is right up against
the roofing at the edges. I know I need to pull this back and put those
foam air channels in. BUT, what about the area between my attic floor
and the bottom edge of the roof (10-12 feet, probably)? I am not sure
yet whether there is any chance for air to travel this path. I have no
access to this area other than by tearing out walls or the roof. Gah!

I am looking at installing a powered gable vent. I have a continuous
ridge vent now. If I can establish air flow from the soffits to the
attic, it would seem that I should block the ridge vent so that the
powered gable vent pulls air up under the roof? Also - the powered
gable vents I saw at Menards/Lowes/Home Depot are thermostat
controlled. They go off at the set temperature. These thermometers only
go down to 50 or 60 degrees F. That seems too warm to me - in the
winter it would seem that I would want the fan to go off at a much
lower temp. Am I missing something here?

Thanks for any advice!

Matt

SailFan wrote:
I have a couple of questions regarding attic ventilation and ice dam
prevention:

My house is a cape cod style, which presents a challenge. In the upper
attic there is plenty of loose insulation, but it is right up against
the roofing at the edges. I know I need to pull this back and put those
foam air channels in. BUT, what about the area between my attic floor
and the bottom edge of the roof (10-12 feet, probably)? I am not sure
yet whether there is any chance for air to travel this path. I have no
access to this area other than by tearing out walls or the roof. Gah!

I am looking at installing a powered gable vent. I have a continuous
ridge vent now. If I can establish air flow from the soffits to the
attic, it would seem that I should block the ridge vent so that the
powered gable vent pulls air up under the roof? Also - the powered
gable vents I saw at Menards/Lowes/Home Depot are thermostat
controlled. They go off at the set temperature. These thermometers only
go down to 50 or 60 degrees F. That seems too warm to me - in the
winter it would seem that I would want the fan to go off at a much
lower temp. Am I missing something here?

Thanks for any advice!

Matt


Had a similar situation. Actually there are 2 winter
problems: warm roof causing ice dams and lack of
ventilation, causing condensation on rafters/roof deck
and resulting in mold growth.

I put a gable vent fan in and a louvered intake at
the opposite gable. Thermostat is bypassed in winter
and the fan runs under manual control from a speed
control ("dimmer" for motors). If I set it so the
fan is barely spinning, that's enough to keep the
roof cold AND prevent condensation.

In your case, give it a try without blocking the ridge
vents; it may work just as well.

Jim

" am looking at installing a powered gable vent. I have a continuous
ridge vent now. If I can establish air flow from the soffits to the
attic, it would seem that I should block the ridge vent so that the
powered gable vent pulls air up under the roof?"

If you have a ridge vent and decent soffit vents, that is widely
recognized as one of the best solutions, so why fool around with a
powered gable vent?

SailFan wrote:
I have a couple of questions regarding attic ventilation and ice dam
prevention:

My house is a cape cod style, which presents a challenge. In the upper
attic there is plenty of loose insulation, but it is right up against
the roofing at the edges. I know I need to pull this back and put
those foam air channels in. BUT, what about the area between my attic
floor and the bottom edge of the roof (10-12 feet, probably)? I am
not sure yet whether there is any chance for air to travel this path.
I have no access to this area other than by tearing out walls or the
roof. Gah!

I can't figure out what you are talking about.

/\
/ \
/ a \
/___\
/ | | \
/ | b | c \
_______
| |
| |
| |

I am sure many of you will not be able to see the ASCI art as I do but
maybe you can figure out what I am trying to do.

What areas are you talking about being a problem? A,B or C??

I am looking at installing a powered gable vent. I have a continuous
ridge vent now. If I can establish air flow from the soffits to the
attic, it would seem that I should block the ridge vent so that the
powered gable vent pulls air up under the roof? Also - the powered
gable vents I saw at Menards/Lowes/Home Depot are thermostat
controlled. They go off at the set temperature. These thermometers
only go down to 50 or 60 degrees F. That seems too warm to me - in the
winter it would seem that I would want the fan to go off at a much
lower temp. Am I missing something here?

Thanks for any advice!

Matt

--
Joseph Meehan

Dia duit

The overall concept is simple:
1. contain heat below, from transmission through walls and ceiling.
Seal off these cavities from above. Vapor barrier at inner surface.
2. allow moisture entering insulation, and entering attic via leaks,
means of escape. Simple enough through exterior walls. In attic, by
means of venting attic, like with vents in soffit and ridge- sounds
like you're short the soffit vents, which should admit air over all
insulation. Basic physics will cause airflow to occur. This airflow, if
vents are of adequate size for situation, will keep roof skin from
melting snow.

Powered gable vent is for summer cooling, and shouldn't be necessary if
you effect soffit venting to match the ridge vent.

HTH,
J

In the ascii drawing above the area that concerns me is "C". I can take
care of "A", but I am anticipating trouble getting airflow from eaves
up into the attic through "C". It is all area I can't easily inspect.

Matt

SailFan wrote:
In the ascii drawing above the area that concerns me is "C". I can
take care of "A", but I am anticipating trouble getting airflow from
eaves up into the attic through "C". It is all area I can't easily
inspect.

Matt

I thought that might be what you were talking about. Sorry I don't have
any answers. The only home I have had with this situation was when I was a
kid (1950's) and we did have access to those areas, we even used them for
storage, but I don't know what we did about ventilation. A had a gable vent
at each end and B was a bedroom for me and my brother. I am going to guess
C was vented from B, but I really don't remember.

Personally I would not put powered vents in. I would look for non
powered vents as low as possible in the gables and let the ridge vents pull
the air.

--
Joseph Meehan

Dia duit

Thanks, Joseph!

Looks like I need to do some exploratory work this weekend and see what
I can discover about "C". I'm hoping the proper air space was
incorporated into the construction, but not counting on it.

Looking at my soffits: The soffit is wood (rough-sawn cedar). I'd like
to get a continuous vent in the whole length of the eave. Right now
there are maybe 6 vents along a 60 foot length of eave.

Wish me luck...

Matt

SailFan wrote:
Thanks, Joseph!

Looks like I need to do some exploratory work this weekend and see
what I can discover about "C". I'm hoping the proper air space was
incorporated into the construction, but not counting on it.

Looking at my soffits: The soffit is wood (rough-sawn cedar). I'd like
to get a continuous vent in the whole length of the eave. Right now
there are maybe 6 vents along a 60 foot length of eave.

Wish me luck...

Matt


I can say that many contractors are very creative about finding answer
to problems like this. You may want to check with a roofing contractor,
pick an older guy who has had lot of experience.

--
Joseph Meehan

Dia duit

Hi, Matt. I'm working on the same problem... but I'm sorry I have
access to "C". I'm laying down insulation on the ceiling joists( my
house was severely under insulated). Last year, I had severe ice
damming it even leaked INSIDE one of my window frames. I hate to
think about what this did to my inside walls and behind the aluminum
siding. This year I've decided to eliminate this problem. Here are
two sugestions in addition to the ones mentioned. Try a roof rake. It
comes in many styles but the one I bought this year (and haven't tried
yet) is a flat piec of aluminum about 20" wide with small rollers to
lift it off of the shingles. I don't know if this will fit your home
but i installed small vents on each side of the wall. I don't have
safettes so I don't have a choice. I have to vent from somewhere. I
tried to place the vents so that they are in alignment and hopefully
will cross ventilate. Kinda like peak vents but farther down the wall.

phil