Roof sheathing moisture-Don't just add vents

[KEVIN WOOD]

Now you are on THE RIGHT TRAK! Only thing missing is good filtration and stale air from the crawl space. Keep the floor sealed well and have ventilation added to the crawl space to keep nasties out and you are all set.

[An HI]

Originally Posted by rernst1

I don't think any energy auditor or person here that is in agreeable with the article that started this would argue that proper ventilation of the living space of a home is important. When air sealing a home there are guidelines to ventilating the living space. The auditor and the retrofit contractor should be educated in those areas and that's why hiring someone that has a certification from an organization like BPI is important. Yes you can air seal a home below the point where there will not be enough natural air changes and that's when you have to add something like a HRV. The contractors I know use a blower door while doing this type of work and if there is no budget for a HRV they stop air sealing prior to reaching that point. There is also a test out to ensure the work was done right.

The majority of the time we will find that attics and crawl spaces are under ventilated. I will agree to that statement. BUT the fact they are under ventilated is often due to poor construction practices in other areas. A home with a crawl space is going to allow moisture in to the home. It will also allow moisture into the attic. Stack effect will pull that moisture up into the attic. Especially if there is a direct chase way. Mean while the leaky ducts and poor air sealing are allowing that moisture and other contaminants in to the living space.

So how about this. You seal off the crawl space floor 100% with plastic. Now you have greatly reduced the source of your moisture in the crawl space, the living space, and the attic. Your crawl space now needs less or no vents because there is nothing to vent. You can have now 1 sqft vent for every 1500 sqft of crawl. If you like you can even insulate and seal all vents and add some connections to the house and have a conditioned crawl space which would benefit in energy savings. Also your ducts and water pipes are warm.

Now that moisture has been reduced in the house and the attic the ventilation we had in the attic before that was inadequate may now be sufficient. Now do air sealing and insulating in the attic to keep that warm and now less moist air in the home where people want it. The natural or mechanical air exchanges can occur still but the attic is now going to have less air exchanges with the crawl space and the interior. This means less moisture and reduced attic temps. The vents now can handle what they are getting and we have less condensation in the attic and also reduced underside roof temps which is a benefit for climates with ice damming.

I have seen it said in reviews of the history of attic venting guidelines development that attic venting was actually ventingn moisture from the crawlspace a lot of the time. So dry up the basement, vent interior moisture from our activities in kitchens & baths and then airseal at the uppermost ceiling. Then the little bit of attic venting that may be installed is probably all you need.

In snowy, northern climes, vents are sources of snow entry.

[James E. Braun, CMI]

If you have less venting in the crawlspace, then air can be drawn up by the more vented attic, and vice versa. But if both or vented correctly then none of this will happen.

[James E. Braun, CMI]

Originally Posted by An HI

What do you do when "code" ventilation does not solve an attic moisture problem and more ventilation actuallly increases attic moisture levels?

If attic ventilation is actually causing moisture problems, then the attic is being vented wrong. Just as Kevin is saying you need balance. Do not just focus on top venting as the author of the article that started this thread.
As Peter is saying making an attic anconditioned space would also work but will cost more money to do.

[James E. Braun, CMI]

Peter,
There is not much building codes in my area. What there are, is not really being enforced. If I got to justify if something is not done right, I just refer to the national codes as a building standard or the product manufacturer instructions. I have found it is hard for the builder to come back at you when you do that. I love it when a builder cannot back what he is doing by something that is already written, but he said that I did not know what I was talking about when something is pointed out; I have found a few home inspectors do this also which amazes me.

[KEVIN WOOD]

This is also the reason I will not do a report on site. On some occasions I will need to search into my vast library at home to find an answer. I try really hard to find anything that might be a questionable area within 24 hours of the inspection. I have had some say they need the report in less time but never the same day.
The 2006, 1997 OBC 2006 IBC and RBC is over 2672 pages alone and my other library info not including Home Computer and CD's has about 6 feet of book space all on IAQ and Home Inspection. And when asked by my clients why I do the report at home all I do is scroll through the Ontario Building Code on my computer.

[Jason Kaylor]

Originally Posted by prussell

Do you two Certified Master Inspectors know how to establish a thermal boundary?

By the way, I took my BPI Building Analyst certification in Phoenix as to have a better understanding of building envelopes in different climates.

And to ride a Harley in the middle of winter!!!

JJ

[Roy D. Cooke, Sr]

Originally Posted by kwood

This is also the reason I will not do a report on site. On some occasions I will need to search into my vast library at home to find an answer. I try really hard to find anything that might be a questionable area within 24 hours of the inspection. I have had some say they need the report in less time but never the same day.
The 2006, 1997 OBC 2006 IBC and RBC is over 2672 pages alone and my other library info not including Home Computer and CD's has about 6 feet of book space all on IAQ and Home Inspection. And when asked by my clients why I do the report at home all I do is scroll through the Ontario Building Code on my computer.

I Did all my reports on site those I have mentored also do all their reports on site .
I think all Homies In my area do reports on site .
I am not a code Inspector.
I am done when I get home no reports to write at Midnight or 24 hours later .
I see to many Homies asking Questions I feel are not part of our SOP .
I have called another homie for info and have others call me some times for Consulation while on site.... Roy

Yes I rode a Harley in the winter for 5 years with a side Car , A lot different then a solo machine

[Stephen W. Stanczyk]

Originally Posted by rcooke

Yes I rode a Harley in the winter for 5 years with a side Car , A lot different then a solo machine

Didn't you mean a side "Char"?

[KEVIN WOOD]

Opps! You better hope Char is not monitoring Roys threads. LOL

[Peter C. Russell]

Originally Posted by jkaylor

And to ride a Harley in the middle of winter!!!

JJ

You got me on that one!!!!!

[William J. Decker]

I wonder if anyone even a) put a moisture meter to the sheathing in that area and b) saw if there was a soffit ventilated bathroom or clothes dryer exhaust in that area and c) checked if the roof was leaking in that area.

Look for the simple answers before looking for the politcally correct solution.

Just my opinion.

[Brad Brinke]

Originally Posted by rernst1

To answer the question the attic fan exhausts air from the attic. The problem often is that the fan pulls more air than the vents allow in. This depressurizes the attic. If you have a manometer it would be able to check this out yourself. When the attic is depressurized and the attic vents can't produce enough make up air then the air gets pulled from inside the house. This air can be warm and moist. This is what the article is all about.

If said fan is running then it is most likely a hot day and the air in the home would be cold and dry, right?

[Robert Ernst]

Brad not totally true. Some of the attic fans will come on when the attic reaches 100 degrees. What about solar fans and turbine fans? These can be operating on days where there is still a need for heat. I'm going to assume that your talking about it being dry due to A/C. Here in this climate it is pretty dry during the summer but people use swamp coolers and thus the house is at a pretty high humidity. The best bet is to keep the air from migrating from one area to another.