Spray foam and ceiling prep
Hello GBA,
I need some advice on how to prepare my ceilings. I recently purchased a 1950s farm house in lower Alabama and am in the process of restoring it. The house had ceilitex tile on the ceilings which was throughout the house . Under the tile is boards that are butted up together. I’ve ripped all the tile out as well as the insulation on top of the boards and have already had spray foam insulation sprayed in the attic. My original thought was to stain the board ceilings and let that serve as my ceilings (they look great/very rustic). I’ve also had a new hvac installed and contractor took in consideration the ceilings and foam. My fear now is that I will have a hvac that is constantly running and dust issues bc there are some gaps in the board ceilings- some gaps as big as 1/2 an inch. I’m now thinking I might have to put something on the boards but don’t want to go the sheet rock route…rather bead board. Any help would be greatly appreciated.
Brent
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Replies
Brent. With open cell foam on the underside of the roof, you have to be careful about moisture accumulation in the attic. (See this article for more information: https://www.greenbuildingadvisor.com/blogs/dept/musings/open-cell-spray-foam-and-damp-roof-sheathing.)
Did you do any additional air sealing on your home, and did you create a conditioned attic space? Where is the HVAC unit and ducting located?
I hope you researched the Celotex tiles to confirm they did not contain asbestos.
As far as airs raking, it has new windows but no real air sealing. It is a brick home. The hvac has the heat pump outside with a closet handler inside. No asbestos in the tile.
Sealing not raking
Brent,
We need more information.
1. Is this a horizontal ceiling with a vented attic above it? Or is this a sloped ceiling?
2. If this is a horizontal ceiling with an attic above it, where was the spray foam installed? Was the spray foam installed on the attic floor (on the attic side of the board ceiling), or was the spray foam installed on the underside of the roof sheathing (creating an unvented conditioned attic)?
3. If the spray foam was installed on the attic floor (rather than along the sloped roof plane), it's important to know whether there are any ducts in your attic.
And my attic will be conditioned.
Brent,
That's a partial answer to my questions.
1. Does that mean that the spray foam was installed along the roof slope (on the underside of the roof sheathing)?
2. If so, can you tell us whether there is a horizontal ceiling that separates the attic from the floors below the attic? If so, what materials are used for this horizontal ceiling?
3. Finally, are there any ducts in your attic?
Horizontal ceiling, with foam on underneath of roof sheathing. The ducts are in the attic just above ceiling and below foam on the underside of the roof.
Brent,
Q. "My fear now is that I will have an HVAC [system] that is constantly running and dust issues because there are some gaps in the board ceilings -- some gaps as big as 1/2 an inch."
A. If you have installed spray foam on the interior side of your roof sheathing to create an unvented conditioned attic, then your attic is inside your home's thermal boundary. The gaps between your ceiling boards are irrelevant, as long as the air on one side of the ceiling boards is conditioned, and the air on the other side of the ceiling boards is also conditioned. The gaps between the ceiling boards don't connect in any way (I assume) with outdoor air. The ceiling is no different from a louvered closet door.
That said, your HVAC system may still run constantly, for a variety of reasons. Your house may still be leaky or poorly insulated. If that's true, the solution would be to (a) reduce air leakage by sealing cracks in your thermal envelope, and (b) improve the R-value of your home's insulation layers.
Finally, you haven't yet told us whether you used closed-cell spray foam or open-cell spray foam to insulate your roof sheathing. If you used open-cell spray foam, you may need to consider whether the open-cell spray foam will set you up for moisture problems. For more information on this issue, see High Humidity in Unvented Conditioned Attics.