Help - Rafter Baffle Installation


  #1  
Old 01-18-23, 12:27 PM
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Help - Rafter Baffle Installation

Insulation company installing baffles and insulation in my garage loft. When it was quoted I was told the baffle would go from the knee wail to the collar tie. I assumed it would be a continuous piece(s). They are here today installing but they are putting a short piece of baffle at the knee wall and a short piece at the top at the collar tie with nothing in the between then laying in a piece of batt insulation. (see photo)
The installer said that is how he has always done it yet when quoted it was implied a continuous piece. I sent the phot (without markup) to the estimator and she said "that is exactly the way it should be done". I then said you mentioned it was continuous and she said nope.
Is this normal baffle insulation practice?

 

Last edited by FairwayFatty; 01-18-23 at 12:28 PM. Reason: photo not appearing
  #2  
Old 01-18-23, 12:30 PM
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Yes it's normal.
 
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Old 01-19-23, 05:03 AM
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My garage bonus room would have the exact situation when, or if, I ever finish.

But like mine I'm going to assume that in other areas of the room there are other rafter bays that go from the soffit to the ridge vent which would be the path for air flow. Not really sure why they would even put the sections of baffle in there.
 
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Old 01-19-23, 09:39 PM
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The purpose of the baffles is to allow the maximum amount of insulation in each bay while preventing that fluffy stuff from expanding upward and limiting airflow or contacting the bottom of the roof deck. The baffles should deliver the incoming air to just above the insulation level in the upper space.



Then there is the question of 'how much insulation is required in that space. If those are 2x6 rafters then you only have 5.5" of space so they would be using R-19 or R-13 fiberglass. R-13 would not be a maximum fill and R-19 would be too thick ultimately fluffing up and blocking the airflow.

In that section of the roof, very common on capes, the baffles should be continuous and the insulation should properly fill the remaining space.

I don't have your city codes but doesn't look like they are installing enough insulation.

Bud
 
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Old 01-20-23, 04:58 AM
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I agree with Bud9051. Without a baffle under the insulation, there is no way to prevent an expanding or moving batt from blocking the flow of air between the rafters from the soffit to the ridge. Even during the batt install, there is no way to see if the the batt is contacting the underside of the roof sheathing. Normal does not mean correct. I would insist on continuous baffles where insulation could come in contact with underside of roof sheathing, even if you have to pay.
 
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Old 01-20-23, 05:33 AM
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I stand corrected, I thought we were looking at the ceiling at first glance!
 
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Old 01-20-23, 08:28 AM
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I thought we were looking at the ceiling at first glance!
​​​​​​​That is the ceiling isnt it?
 
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Old 01-20-23, 09:28 AM
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No, those are the rafters. Look at the window for reference.

Regardless, I think the rafters are probably 2x12 (on left side of photo they look deep) so I doubt the insulation reaches the roof deck. Probably plenty of air space even without the baffles. Not something I'd quibble over with the contractor.
 
 

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