Soffit Vents

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Old 12-01-04, 09:07 PM
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Soffit Vents

I recently purchased a war-time bungalow and have found that there are no soffit vents installed. The loft is quite warm during the summer and I was thinking that the addition of soffit vents would help. (Probably need additional air return and ductwork too but for a different forum) I currently have gable vents on either side of the house as well as two square vents installed directly into the roof on the backside and one on the front. Any idea if this is enough ventilation?

I was thinking to try to install the soffit vents myself if they are needed. I can get in behind the kneewall (I think that is what it is called) and will need the baffles to keep the blown insulation back. I can't get to the soffit area due to the pitch of the roof. What is the best way to install the soffit ventilation?

Any other suggestions?
 
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Old 12-02-04, 11:19 AM
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Bungalows

All great questions!
Installing soffit vents is performed from the outside. There are many different kinds. I prefer the 2" continuous strips. Cut out a 2" strip of soffit from one side of the house to the other and slip them in from the outside. A few staples or finish nails and your done.

Then, you will need to get into the crawl space behind the kneewalls to ensure the insulation is pulled back from where the roof meets the wall to allow air flow.

Thats the easy part....the tough part is you also need a path for venting on the underside of the roof deck where the vaulted/sloped ceiling portion of the upper room is, (above the kneewall). Baffels that install between the rafters are made for this application, however I don't know how your going to get them in there without removing the ceiling (from the interior), or the roofing and sheathing (from the exterior).

For the ventilation to be effective is must have a clear path from the soffit to the gable vents. If you don't do the vaulted portion...it's all for nothing.
 
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Old 12-02-04, 12:08 PM
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Thanks, will take a look at how i can get the baffles installed above the knewall.

When you say cut a 2" strip from the soffits, would that be in the viny siding soffits, or removing the siding and cutting into the wood that is above the vinyl soffit. If it is in the vinyl, or not ,what is the best method to cut into the wood that would be blocking the air flow. Circular saw, recip saw, jig saw... Other saw?
 
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Old 12-02-04, 01:48 PM
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Soffit

Didn't know there was vinyl..this actually makes it easier

The vinyl soffit should already be slotted for venting. If not you will need to replace the vinyl soffit with one that is vented/slotted. This will look better than trying to cut holes in it. If you don't want to replace the vinyl soffit they do make round approx. 2" vents that you could match to the size of the hole saw and bore all the way through the vinyl and wood then intall the vent in the hole. However there will be A-LOT of them, so the slotted vinyl will not look like an afterthought.

While the vinyl is down you can use a 2" or 3" hole saw and a cordless drill to cut a series of holes in the existing wood soffit that is beneath the vinyl to allow air to pass through.

Here is where the math comes in. Check with you local code enforcement person to find out the required venting in your area. It should be either 1 to 300 or 1 to 150. Thats 1 square foot of venting for every 300 square feet of space, or 1 to 150. Measure the outsde walls (one front, and one side) and multiply together to come up with sq. footage and then divide by 300 or 150 whichever applies. Half of that number is the intake quantity (or # of holes you must drill), and half is exhaust quantity or size of you gable vents.

The gable vents should be sufficent for the exhaust (1/2 base times height= area of a triangle) if not you can add ridge vents in the center of the span to make up the difference.

Woops, I just noticed your in Canada,... Sorry, all the above must be converted to metric
 
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Old 12-02-04, 02:20 PM
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That's alright I am a transplanted American and have no idea how things work in Metric. Besides we are just over the river from Detroit so everything is in both.

Thanks for the help. This site is a wealth of knowledge and knowledgeable people.
Thanks again
 
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