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Insulation / Venting Screened Porch Ceiling Question

Insulation / Venting Screened Porch Ceiling Question


  #1  
Old 07-17-18, 08:50 AM
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Insulation / Venting Screened Porch Ceiling Question

Hi all -

I've added to my 1886 Indiana home by putting a second-story bedroom on the back of the house with a new screened porch underneath it. The ceiling of the screened porch (conditioned second-story bedroom above it) has 2.5" of closed cell foam in it, blown in to stick to the flooring of the bedroom. I'm going to add R-19 batt insulation (unfaced) beneath the foam and then finish the ceiling with tongue-in-groove car siding to close up the insulated space and give the porch ceiling a nice finished look.

Two questions:

1. Is it the right call to add the R-19 unfaced beneath the closed cell foam?

2. I need to vent this space so moisture can escape, right? I'm thinking about 3" exterior vents on the ceiling of the porch, one at the end of each ceiling stud cavity.

Thanks!
 
  #2  
Old 07-17-18, 08:55 AM
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You could use perforated vinyl soffit for the ceiling of your screened porch.
 
  #3  
Old 07-17-18, 01:23 PM
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Thanks for the suggestion. I really like the look of the car siding, and I have no problem doing the small amount of extra work to put in the vents. My main question is whether or not I need to vent it, and I think the answer is yes, I do, one way or another, right?
 
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Old 07-17-18, 02:22 PM
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I'm not familiar with the term "car siding" but assume it is basically a T&G wood. Since T&G leaks a lot of air so I don't think added vents will be necessary. In any case, venting needs a vertical placement of low and high vents which I don't think you will have. Just don't install a plastic vapor barrier and the moisture will out just as it moved in. But the layer of rigid insulation should prevent any air getting in from finding a cold surface to deposit its moisture.

Bud
 
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Old 07-17-18, 07:43 PM
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Thanks for the detailed insight, Bud.
 
 

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