Venting my Attic

[Hibbing]

I'm in the process of installing a ceiling in my garage. I think I need to somehow vent the attic as it will get really hot in the Summer. Are there "codes" that I have to follow and if so, what are they. I was thinking a "spinner" on the roof with a couple of gable vents. Is that enough for a 24 x 26 garage? My soffits are only about 6 inches wide so I'm not sure if I can put soffit vents in. Any advice would be appreciated. Thanks!

[walleyeseeker]

Spinners are proven to be the worst vents. There are specific requirements as to how much vent space is needed in the code. The best vent would be a continuous soffit vent coupled with a continuous ridge vent. You would need to put in wind blocking on top of your top plate to the roof and cut in air chutes to allow the air to move up the back side of your roof sheeting. Contact your local building official to get the exact requirements. Improperly done, you will ruin your roof in a short time.

[Roofer]

Don't use both roof and gable vents, it will ruin the system. Stick with what walleyeseeker said. You could cut in a few regular vents if the vented ridge doesn't fit what you like. Either way, you are right, it needs to be vented.

[sparcebag]

Actually a roof vent coupled with soffit is the best it creates flow. warm rises cooler enters soffit creates the flow or air current.I believe the both are required.If I remember correctly for every 1000 sq ft of area you'll need 150 sq inches of vent and I believe its combined roof & soffit.They do make circulal soffit vents 2" Drill holes & insert,there is also 2" wide strip soffit vents in varing lengths and cutable for custom legnths.Gable vent is acctable along with soffit vents.

Personally I'd go more venting than 150 sq in. to 1000sq ft.In your case each gable end at least 10x10 in. and in the soffit 4 2"x12"each side.It will get the heat & humidity out.

Call your local inspector to verify.

[Roofer]

I have to disagree. Vented ridge is the best air flow and gets the best warranty for the shingles as long as it is the correct baffled ridge vent.

Continuous soffit and chutes are also what is needed to get the best venting.

There are alot of variables and is actually down to a science, but I like to keep it simple with open soffits, chutes, and a ridge vent or 10"x10" holes with roof louvers every 8-10 feet, depending on the pitch. If the louvers are too close together, the air can start going in one vent and out the next, carrying very little moisture out. Especially if there isn't enough soffit venting.

[walleyeseeker]

I believe the code for ventin is 300 square inches for every 1000 square feet. This then is to be divided equally to the soffit and the ridge. I think that is where the 150 number keeps coming from. The industry has proven that the ridge vent is best when you can achieve the proper numbers, otherwise, you need to use vents. No system will work properly if you don't use both soffit and ridge type vents.

[sparcebag]

 Originally Posted By: Roofer

I have to disagree. Vented ridge is the best air flow and gets the best warranty for the shingles as long as it is the correct baffled ridge vent.

Continuous soffit and chutes are also what is needed to get the best venting.

There are alot of variables and is actually down to a science, but I like to keep it simple with open soffits, chutes, and a ridge vent or 10"x10" holes with roof louvers every 8-10 feet, depending on the pitch. If the louvers are too close together, the air can start going in one vent and out the next, carrying very little moisture out. Especially if there isn't enough soffit venting.

roofer when I said roof vent it covers all,But does'nt this guy want gabel vents?? I would suppose he doesnt want to mess with the roof.Thats my take anyway.

[Roofer]

Sorry sparcebag, I mis-understood you. Not sure what he wants.

[Hibbing]

I want to avoid venting my ridge. The shingles are only about 10 years old and I would hate to start cutting into them. I am looking at the most economical way of keeping the attic cool. Power vent or gable vent. Right now,I have no vents in the roof. Thanks for any advice.

Jeff

[Surface Tension]

Like said you must vent the soffit. A good roofer could have the ridge or roof vents in in on time and not damage your roof.

If you insist on the gable end vents go for it. If you find they aren't doing the job then add the roof vents later on.

[311Hemi]

Great thread....I just started the same exact project with a buddy at his house. No current vents but what you guys are saying matches what I have been told by the father-in-law, who is in this line of work.

I along with the roof and soffit vents (and the channel piece that goes by the top plate), I was told we should put up a vapor barrier of plastic on the ceiling and walls before sheet rocking it?

I was also told of high strength sheet rock that has fiberglass in it that is used for ceilings....any thoughts or experience on this?

[Hibbing]

311 You're getting ahead of me here! That was going to be my next question - is a vapor barrier necessary? I was told (advised) not to use sheetrock on the walls. OSB was recommended. Insulation? Blown in or fiberglass?

Rafters are on 24" centers. When I put up the ceiling, should I put framing in where the sheets butt up to each other?

Thanks for all the great advice!!

[Roofer]

I used OSB on the ceiling in my attached garage. I believe this is OK as long as you have a legal fire barrier(sheetrock) between the house and garage all the way up to the rafters.

You should have Poly on first. Your inspector may want to see that before you sheetrock or OSB. Make sure you have a building permit before you start.

I used 1/2" ceiling rock on the ceiling of my Pole shed. It is holding up just fine. It is lighter weight, but a little more expensive.

One other thing is to make sure you have enough lights and outlets before you cover everything up. I rewired my whole garage to 12-2 wire, which holds current better and safer for my air compressors.

I hope this helps. Seems to be alot of help here, so just ask.

[311Hemi]

What happens if you don't have a permit. Its not my house....so ultimately not my decision. But at least I can pass along the info.

[Roofer]

There were a bunch caught around here with no permit. There can be a large fine of up to $10,000. It is a MN statute that permits are required.

For a homeowner, they are normally cheaper, I have seen where they are actually free.

[311Hemi]

The rafters in the garage we are working on are 4' OC. We are running additional 2x6's to make the ceiling 24" OC. I am wondering if it's possible to span a 29" space on one of the ends of the garage (between the rafter and wall) with sheet rock and not have it droop over time?

[Roofer]

Just run some 2x4's adjacent to them and to the wall. This will give you some more nailing and peace of mind.