Soffit Venting

Tom67

I'm going to be replacing my shingles soon and am replacing 4 can vents with a ridge vent. The house has a 24" overhang with vented soffit ( there are 22 vented sections 10" wide x 24" evenly spaced around the house, but there are only 4 or 5 proper vents in the attic. My question is, are there enough proper vents ( attic chutes, whatever you want to call them) to properly vent the attic. The attic area is about 28'x46'. Any help would be appreciated. Thanks

Ed the Roofer

The reason for the proper vents, (baffle vents, insulation chutes, etc...), is to allow a passage for free flowing air to travel upwards from the soffit vent to the ridge vent to get exhausted.

They are needed if the insulation is packed too tightly to the underside of the roof deck sheathing.

So, to answer your question, you would have to state whether or not the insulation is blocking the path from the soffit vents. If it is, then it does not matter if 100 % of your soffits are vented, (which would be the better way anyways), because the airflow will be restricted anyways.

Ed

Tom67

No the proper vents that are there are not restricted at all. The air coming in the vented areas of the soffit is able to reach the proper vents by traveling along the tails of the trusses, I was just wondering if those few proper vents were sufficient enough . They're pretty small vents by the way, only about 3"x8".

theroofinggod

Sounds Fine

Ed the Roofer

What about the areas that do not have the insulation baffle vents installed. Is the air free flowing from the soffit vents into the attic area?

Ed

Tom67

Yes, the air can flow unrestricted from all the vented soffit areas to the proper vents. My question is if the proper vents that are there are allowing enough air into the attic. Or should I add some more proper vents. I guess I can just put some more in to be on the safe side, kind of a pain in the butt though.

reveivl

If all you're doing is changing the old shingles for new ones, and not changing anything else, and you don't have a problem with moisture now, why would you have one after? If the ridge vent is equal to or greater than the net free area of the old can vents, then you've improved the situation.

I've seen houses with no venting whatsoever that had no moisture problems, and I've seen the opposite too.

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Tom67

You're supposed to have equal or greater soffit venting than ridge venting. I will now have more ridge venting and don't want to be sucking warm moist air out of the interior of the house into the attic because there isn't enough air coming in the soffit vents.

Ed the Roofer

Tom, you are exactly correct about that.

You know more than most of the unqualified contractors now.

Ed

Tom67

Thanks, I'm just a dumb bricklayer, but I try to educate myself as best I can about things. I was just up in the attic trying to install some more proper vents, virtually impossible with a 4/12 pitch. I guess I'll have to take the fascia cover off and install them from the outside. Any other ideas would be appreciated.

MJW

The only problem with the old soffit vents is that most of the time they are plugged up with dust.

I don't think you will pull moisture through the vapor barrier from the inside of the house. Might be thinking a little too far into it. The roof venting can only let out as much as is brought in. It's the same as opening a window on one side of your house.

Replace the shingles and put in a ridge vent. It is a good idea.