Attic ventilation problem

[sserrels]

My house is one half of a prefab duplex from the 80's. Last week I went into the attic and found mold covering the roof sheathing. It had not been there a few weeks earlier. The attic is supposed to be vented by soffit vents and ridge vent, but I found that the air is not flowing up from the soffit to the ridge like it should. The only moving air in the attic is the air blowing in from the ridge vent. The soffits are blocked by fiberglass batts and an additional layer of blown in insulation. So there's practically no ventilation.

Now here's the problem: the roof pitch is something like 2/12 and the rafters (except those at the soffit vent) run parallel to the ridge. The pitch is so shallow that I can't get any closer than maybe 10 feet away from the soffit vent from inside the attic. I can't clear out the insulation blocking the vents. Plus, if I did remove the insulation, the ceilings of the rooms below would be exposed and uninsulated for a couple of feet from the outside wall.

I'm considering buying an electric attic fan and just forgetting the soffit vent. Any ideas?

Shawn

[Speedy Jim]

Yes. Fan will be very effective. Get a variable speed control ("dimmer" for motors) while you're doing it. The fan will only need to run slowly in winter.

Purists will say to fix the venting problem, but clearly that's not practical here. Jim

[sserrels]

Excellent, thanks Jim. I should probably block the ridge vent if I go this route, right?

[Speedy Jim]

If that will be a lot of work, try it without blocking; may not matter.

[terry]

...................................................................................................................... Shawn: Congratulations on your very clear explanation of the problem.

It just proves what has frequently been considered and referred to, by some, as 'just a theory'. i.e. That it is important to ventilate the attic roof space.

We have even had those who have asked "Is it OK if their dryer vent ( i.e. hot air loaded with moisture) can vent into their attic". Strewth!

Many building standards not only mention percentages of vents in relation to the area to be ventilated they also importantly say something along the lines 'arranged to permit cross ventilation'.

Based on what you have described I think you are on the right track proposing an electric fan to exhaust damp air, both summer and winter as a practical solution. Cost of the fan and a bit of electricity minor compared to replacing a roof and more!

But as someone mentions you may be able to run fan slower at times to avoid negative pressure up there sucking warm air out of the house?

Anybody here have a number for how often the air up there should be exchanged?

[mm]

Use a tool, like a rake. I forget the name of the rake with an iron part at the end with tines perpendicular to the handle. That might work better than a leaf rake. Or make a tool from an old broom handle and 2x10" piece of plywood.

Don't remove it that far.

First scrape away the blown insulation. That might be the only problem**. For those vents that are still obstructed, move the batts back 2 to 6 inches. Even with a low pitch, an inch or two will likely be enough to let air from the soffit vents circulate through the attic. It doesn't have to be a big opening. An inch from the roof is plenty.

If the batts run perp to the edge of the roof, you may be able to stay where you are and pull them towards you an inch or two or whatever it takes. If this leaves some of the ceiling uncovered, you can push back some of the blown in.

**Because the guy who put down the batts was probably careful, since you didn't have mold from the 80's until a few weeks ago. But blown insulation is harder to control and I would guess can move even when no one is there. So I suspect the blown-in is the only problem.

I don't understand which direction thiis fan is going to blow, or why the ridge vent should be closed. Closing that will close everything, it seems, so you'll just be blwoing the air around inside, no?

[tbasc]

, Since there was no mold on the roof deck "a few weeks ago", The problem may well be lack of vapor retarder at the ceiling level. It's possible the cool deck has led to condensation and mold growth.

By force venting the attic space, you will be drawing in air from someplace, perhaps the house. TB

[soup]

there are things you can cram in between the rafters to open up a channel for air to flow. polystyrene. see if you can't get them in between the insulation and the deck

[Goedjn]

Depends on which way he goes. If if forces air INTO the attic, and lets the ridge vent deal with getting it out, that should be ok.

[trader4]

Yes, if it will work, it's worth a try. They sell these chute type widgets you are referring to at building supply/home centers. They get stapled to the underside of the roof sheathing, between the rafters. But in this case, he might be able to work them in by sliding them after using a rake or similar to try to clear the end of the channel.

If that doesn't work, then I'd probably consider gable end vents on both ends. That together with the ridge might be enough. I'd go with a power fan as the last solution, because it uses power and without air intake somewhere, it's going to either not work very well or suck air from the living space. If you get a fan, you obviously need one that goes on with humidity as well as temp.

[sserrels]

Yeah, I tried the rake. But, because the roof rafters and the ceiling joists run _parallel_ to the roof ridge, there's only about a 4 inch space between rafter and joist at the farthest point I can reach. And that's at least 3 or 4 feet away from the outside wall. (I hope you can picture this, I've never seen a house with rafters and joists run this way. Seems stupid.) So I can't really get in there with a rake.

I tried those Owens-Corning Raft-R-Mate polystyrene things, but they crushed, snagged on roof nails, and fell apart when I tried pushing them in.

The electric attic fan I'm considering is one of the type that goes through the roof near the ridge. The soffit vents aren't completely choked off, just not open enough to allow the ridge vent to work as it's supposed to, so I'm hoping that the fan would draw most of the air through the vents and not the house. I assumed the ridge vent should be blocked because otherwise the fan would only draw in air from the ridge and not move any other air in the attic.

Thanks for the help, folks,

Shawn

[Tom The Great]

imho:

Can you tackle this problem from the soffets? If you can pull down the softet cover, move the insulation back, and slide a rigid rafter baffle you might succeed.

As for a fan, you need to ensure there is an inlet for air, and will cost you money to operate.

Just a guess....

tom @

[mm]

Why do you not quote anything, OR, what route is this route?

[Walter R.]

Since you cannot clear the soffits from your attic, can you use a powerful leaf blower to blow through the screens of the soffit vents from the outside? This may dislodge the battens, which you can afterwards push back partially. It would certainly clear the blown-in insulation material from the soffit vents.

[soup]

gotta be something that can be crammed in there that is more sturdy than those flimsy poly things that will do the same thing. gotta think outside the box. maybe it'll come to me

[mm]

Attic fan is ambiguous. Do you mean a fan in the roof blowing out, or a fan in the floor of the attic blowing into the attic, or a fan within the attic. **

If you're talking about a roof fan, I've supported those in many of my posts. If you mean a whole-house fan, I don't know of any one here who has recommended that for a humid attic.

If you mean the third, let us know what you mean.

**I don't take hot showers, so I never have much humidity in my attic. But you can have a humidistat or a manual switch to turn it on when you want it in the winter. The attic fan vents at the ridge rail, which may or may not be close enough to the outside. Check yours.

If you can't move the insulation with a rake, how about a vacuum cleaner or a shop vac? Borrow extra extensions to the wand, don't use any end except the wand, and put some window screen over the wand so it only grabs the insualtion and holds it, but doesn't suck it in.

Also you can put a solid piece of cardboard or something over part of the wand opening to lower the suction, and make the hole smaller so that it will just hold things and won'pt suck them in.

If it does suck some in anyhow, if you've cleaned the vacuum before using it, you cnn just get the insulation out of the vacuum and use it again.

Or hire a midget or a child to go in there and do the work up close. I'm not kidding. AIUI, quite a few burglars have used children because they fit in places that other people don't. Use some temp pieces of wood over the joists so the person doesn't fall through the ceiling. He should wear an approriate mask so he doesn't breathe the fiberglass. You should too. I always do, even when I don't really disturb the fiberglass. You could vacuum the air first and get rid of most of what is NOW floating in the air. I've never actually checked if the stuff is in the air.

[hallerb]

might try a shop vac with small long wand, made from like 1 inch pvc pipe to suck the loose fill insulation from the vents.

have you tried accessing it from outside? might be able to vacuum from outside too, or blow topwards inside

if you install a fan with open ridge vents it wouldnt do much sucking air from nearby ridge vents.

if you choose fan have ridge vent removed from above, tar paper over the holes and replace shingles

i would try getting the soffit vents open

[Goedjn]

If you can get to the eaves, can you take the caps off the vent-holes, and shove a rolled up tube of tarpaper up through the insulation, and then stick the grates back on?

If you end up going with a fan, use duct work to force the air go to/from where you want it to.

[Phisherman]

[trader4]

If you read the thread, he can't do that because the slope/construction of the roof prevents him from getting anywhere near the area of the insulation/soffits.