Rafter bay ventilation

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#1

Originally Posted By: jonofrey
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When installing ventilation baffles in rafter bays, shouldn’t each bay have a baffle installed in it? I can’t see how adjacent bays can get any ventilation to the roof sheathing from a vent in another bay. Also, the baffles in this photo do not seem wide enough to me. Shouldn’t they extend the width of the rafter bay to properly vent the sheathing? Any comments?


Anybody have any reference to back up my instinct on this? Manufacturers specs?

http://www.nachi.org/bbsystem/usrimages/raftervent.jpg

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#2

Originally Posted By: jonofrey
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I guess I’ll answer my own question. The internet is a wonderful thing.


http://www.professionalroofing.net/article.aspx?A_ID=218

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#3

Originally Posted By: gbeaumont
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Hey John


you realy have to stop talking to yourself on message boards, people will think that you’ve lost it icon_lol.gif icon_lol.gif icon_lol.gif


Good link BTW

Gerry

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Gerry Beaumont
NACHI Education Committee
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#4

Originally Posted By: jonofrey
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I think I have lost it Gerry.

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Inspection Nirvana!


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#5

Originally Posted By: jonofrey
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I hope I’m not talking to myself on this one.


The builder told the client that's the way we do all of them. Sheetrock is going up.

My client is considering walking away from this deal. I have a call into the builder to discuss it with them. I guess we'll see but I don't hold out much hope that they'll do it right.

My client stands to lose about 3k for walking on the deal. Probably gives the builder more incentive to not do the job right. I suppose my client has enough evidence to show sub standard work but the builder already has his money.

What would you do if you were the client?

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#6

Originally Posted By: nlewis
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What would I do if I was the client?


I wouldn’t waste $3,000 due to some missing baffles, that’s for sure. If there is a sufficient amount of other roof/gable vents, the reduction in airflow could be minimal. I thought you were referring to a vaulted type of ceiling, then I would have more of a concern.

#7

Originally Posted By: Richard Stanley
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I can’t tell from the pic what this is exactly. Is there going to be a ceiling?or attic space? The site you referenced did say a baffle should be in each bay. I do not recall ever seeing baffles in every bay and I’ve seen alot of them. I think it is the overall ventilation that matters. I’m sure you know the parameters, 1 sq ft per 150 sq ft. If vent are in upper part of space, then 1-300 applies. Why are the batts on the underside of the decking?

#8

Originally Posted By: jonofrey
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Richard,


Thanks for responding. The batts are inserted into the rafter bays of a sloped ceiling. The baffles would provide an air space for the roof sheathing from soffit to attic. Without them, you have a moisture trap. It doesn't seem like a big deal but my guess is if it's left that way the the life of the sheathing and the shingles are drastically reduced. You can't just stuff insulation in the rafter bay and then seal it up with sheetrock. The sheathing won't get any ventilation.

The picture that I posted to me shows plain poor workmanship. I see this scenario all over in new homes. I think it's a way for insulators to cut corners. The damage doesn't appear until years later. Long after any crappy builder warranty has expired. I can't understand why the builder won't force the sub to do it right. Must be strictly price. How much can that foam baffle stuff cost anyway? Can't be much.

Neal, I guess you could call this a semi vaulted or vaulted ceiling. Customers call on the 3k. He had some other issues with shoddy workmanship so I think it's adding up for him in relation to what he is going to be willing to live with for a home.

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Inspection Nirvana!

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#9

Originally Posted By: jmyers
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John,


Not that I am a disagreeable person or anything but I absolutely would not take this house as it is, especially if it is new construction.

I would ask the builder to put it in writing that this is sufficient air flow for this attic space. If they are not willing to do that I would take the 3k loss now, rather than down the line. This is more important than just a little air. Major components of the house rely on that air flow, such as the shingles, the sheathing, the insulation and of course the wood lumber itself could fail prematurely. Given those facts you are not even taking into consideration the presence of warm, wet air which can create yet another problem....MOLD.

Since you are more familiar with your region than anyone else maybe you should be asking yourself would I purchase this house if I were the buyer. Is this something I would be willing to fix, since it could be done realtively inexpensively. How much would it cost to pay someone to fix it for me.

Don't be afraid to contact the builder and mention the MOLD word. Maybe he will start seeing this in the same light as you. icon_biggrin.gif

Joe Myers

#10

Originally Posted By: jonofrey
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Thank you Joe,


I appreciate the input.

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Inspection Nirvana!

We're NACHI. Get over it.

#11

Originally Posted By: ecrofutt
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Under the sheetrock fastened to the rafters scenario, I would not take it either. That scenario calls for each (pretty much sealed into a whole bunch of tiny attics) rafter bay to have it’s own ventilation.


However, in a "normal" (if there is such a thing) attic, you don't "have" to have baffles or vents in every rafter bay. You just need to meet the minimum free area for that size attic and MAKE SURE that there is at least as much intake, if not more, as there is exhaust.

Sounds like a case of lack of research on what was needed and wanted by:
The buyer,
The contractor,
The roofer.

Good Luck.

--
Erby Crofutt
B4U Close Home Inspections
Georgetown, Kentucky
www.b4uclose.com

#12

Originally Posted By: jonofrey
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Erby,


I am thankful for the input from seasoned Pro's such as yourself. I agree with your technical assessment of course.

The buyer depends on the builder to build a home within generally accepted construction standards. To me this scenario is sub standard.

No lack of preparation on the buyers part on this one. He did after all hire me to inspect it prior to insulation. This is the comment that I made in my report even though the insulation installation had not begun yet when I inspected the structure:

" Note to client: It is important that proper ventilation of air from soffit vents to upper passive roof vents is unobstructed. When insulation batts are installed into rafter bays on sloped ceiling, work with builder to insure that an adequate air gap exists between insulation batts and roof sheathing in each and every rafter bay."

The client tried to get the builder to install the baffles correctly base on my comment. Despite this, the builder went ahead and put the sheetrock up. I think it was a sh*tty thing to do.

I blame the builder and the sub on this one. The photo that I posted was actually taken by my client and sent to me after the pre-insulation inspection.

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Inspection Nirvana!

We're NACHI. Get over it.

#13

Originally Posted By: rking
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John,


Up here in my neck of the woods it is a common building practice in new construction (I have almost twenty years experience in it) to put Moore Vents or as you call them baffles in every other rafter cavity and sometimes every third depending upon the pitch of the roof.
BUT; It is quite clear in our building code that ANY roof whether flat or cathedral must have a minimum of a 2" inch air space between the insulation and the underside of the roof sheathing, and that the airflow must be continuous from eave to ridge.

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Muskoka Home Inspections
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#14

Originally Posted By: dleavitt
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Just another input that you probably thought of already is to ask the Local Building department ( inspector) on the specs for this issue and let him know about it. If it is wrong then the contractor can not get a final on the house.