Attic cross venting options

The garage insulation thread combined with my foray into the attic over my kids bedrooms to investigate a possible squirrel break-in (and the subsequent near death heat-stroke experience) made me think to ask....

In my "main" attic I have a ridge vent and push/pull type fans that come on at 100F or something. They vent out the horizontal ends of the attic so there is no roof to cut into. The rooms below stay cool.

The "other", small attic in this case has a pyramid roof with no ventilation but lots of insulating material in the house ceiling. The rooms are still several degrees hotter as a result. The attic itself is insanely hot. Like 150F hot. Like sweat soaked and dripping like I had a hose up my ass hot.

What is my best option for venting this type of roof? Can I put push/pull fans under the eves or do I need to cut holes in the roof? Any particular brands or tips/tricks for installing them? Are there reliable solar options that won't require me to run a 15a circuit all the way out there?

If it is a pyramid (hip) roof with no gable ends I would put some vents in the soffit(ovehang) and a thermostatically controlled fan in the roof. I did this to our house when we bought it. It has a gable roof but didn't have any attic venilation other than some small vents in the brick gable ends. I decided it was easier and would look better to put the fan, etc. than trying to put larger vents with fans in the block and brick gable ends.

Heat rises. You need soffit vents, plus enough venting at the peak to move a certain number of cfm. Lots od whirleybirds around here, but we use them to keep the attic cold in the winter to avoid ice dams on the eaves.

http://www.roofmaintenance.ca/vent_types.html

Mushroom type thermostatically controlled fan through the roof. Some are solar. They are easy to install.

That is all (assuming you have soffit vents).

SVreX wrote: Mushroom type thermostatically controlled fan through the roof. Some are solar. They are easy to install. That is all (assuming you have soffit vents).

I do. Is there an area calculation for the CFM required or... just go big?

There is a simple volume calculation chart on the box of every powered roof vent. You can buy them at Home Depot or Lowes. There are different sizes. Those charts work pretty well.

Soffit vents are required! You need to pull the air from there up to the roof ridge! A ridge vent and a fan can end up fighting each other if you don't have enough CFM flow from the soffit!

In reply to jimbbski:

I would normally agree with you, but he said that part of the house worked fine. No point in fixing what ain't broke.

There is no ridge vent on a hip roof. He didn't actually say if the hip section did not have soffit vents.

GPS: we forgot to answer your question about push/pulls at the eave. The answer is no, you're gonna have to cut through the roof. The eaves will not be large enough to put a push/pull in. It would have to be ducted, and like 4" dia (like a bathroom fan). You are gonna need a high velocity unit with more like 12-14" dia.

But like I said, it's really easy.

They make low profile passive vents that you see on a lot of houses down here that are as simple as cutting a hole in the roof from the outside and then sliding the edging underneath the surrounding roof shingles.

I did all the calculations and believed the literature on several powered vents and then found out they lied.

I will be installing several of the passive ones as soon as my ankle will let me walk on a roof without falling. I broke my ankle in February and while it looks OK and I feel it ought to be OK, it seems that any type of exertion (such as walking bent on a roof) either causes it to swell and hurt or just not work.

I'm going to use my stud finder (I've checked and it will work thru roofing shingles) to find the area between the studs, install a drywall screw in the middle with a string tied to it, and then cut it out and use the string to fish the cut out out. That way I only have to worry about the outside heat and none of the inside.

SVreX wrote: In reply to jimbbski: I would normally agree with you, but he said that part of the house worked fine. No point in fixing what ain't broke. There is no ridge vent on a hip roof. He didn't actually say if the hip section did not have soffit vents. GPS: we forgot to answer your question about push/pulls at the eave. The answer is no, you're gonna have to cut through the roof. The eaves will not be large enough to put a push/pull in. It would have to be ducted, and like 4" dia (like a bathroom fan). You are gonna need a high velocity unit with more like 12-14" dia. But like I said, it's really easy.

OK. So... before I head on out to the store - I plan to get 1 fan capable of exhausting 240 sq ft (plus sized by one for whatever they say it can do), and it is going to go toward the back of the house near the peak of the roof. I'm going to make sure the soffits have enough venting to allow the fan to work.

Drill + sawzall will make the hole just fine - any tips for sealing it back up again? It looks like most of these fans install with shielding that goes under the shingles immediately above it so water goes around the tube. I have a few spares in the basement in case I mangle one in the process but do I need tar too? Other type of sealer? I have all kinds of silicone caulk around that could be used under the shielding.

silicone + shingles doesnt mix well for long. the silicone soaks stuff out of the asphalt, turns brown, and falls off.

the most awesome stuff i've found so far is called flash mate, it is clear and smells very solvent-y and is sticky as all hell. it costs $7+ per tube where the "roofer's coice generic black goo in a tube" costs $2.xx, but it is well worth it.

No silicone. Use roofing sealant- it's like tar in a caulk gun.

Every unit you buy will have a detailed instruction sheet.

Here's a basic video:

Solar Roof Vent Install

Be careful. I had to look a bit on YouTube. There are an awful lot of videos of how to do it poorly.

The link I gave is not a bad install. I usually peel back the shingles and re-install, so I am less reliant on sealant and more reliant on nails and mechanical fasteners, but the video is well done. An electric powered unit is similar in installation.

I wouldn't put screws through the surface of the shingles like they do, but the sealant they use will work without leaking.

The trick he does with the sawzall cutting around the circle to cut the nails is not a trick I would recommend. That's a recipe for damaged roofing if you are not good with a sawzall. It's just as easy to do with manual tools like a flat bar and nail puller.

Good luck!