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Agirlandheraframe
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# Posted: 24 Aug 2024 10:03am
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Hello all.
I will preface this by asking please be kind, I’ve never done construction before and somehow got it in my head I could build a tiny house.
I have a mold issue between my insulation and exterior roof sheathing inside.
My framing is 2x6, my original intention was to have exposed beams and roof deck, I used t1-11 as a cheap barn board look facing down into the interior, with the intention of doing a non vented roof with the rigid insulation on the exterior of the roof deck. Winter came too fast and I needed the roof buttoned up so I switched to putting the rigid foam inside.
I adjusted the exterior sheathing to accommodate a soffit at the bottom and ridge vent at the top. While installing the insulation inside a construction friend came and said I needed to spray foam closed the gaps at the bottom and top, and without thinking I did it. So I essentially closed my ventilation with spray foam like an idiot ?????
I also have a 2x6 horizontal support that runs the entire length of the house at 4ft and 8ft high, furthering the lack of ventilation. Trapped moisture and warm/cold air is basically circulating within this 4 and 8 ft areas with no where to escape.
My question is, if I were to remove everything back down to the framing and exposed t1-11 can I properly close the gaps I made for the venting and then have a non vented roof with the insulation on the exterior? Properly vented on the exterior of course. And if I did that would I then need gable vents or something else for added ventilation?
Or if I were to fix this venting situation that I currently have, where the insulation is inside, is there a way I can properly vent the insulated area inside with these horizontal beams where they are? A way to maneuver air around them, maybe by adding a 2x2 to each beam to allow more space between insulation and this horizontal cross beam?
Attached below is a photo from early construction where you can see the horizontal cross beams
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ICC
Member
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# Posted: 24 Aug 2024 09:01pm
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Knowing the location or climate zone would help in choosing a solution. This link has a map down the page a ways and info. https://www.energy.gov/energysaver/insulation
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ICC
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# Posted: 24 Aug 2024 09:08pm - Edited by: ICC
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Note that for insulation and ventilation of an a-frame the long sloping walls are treated as being roofs, not walls.
The original idea of rigid sheets of foam on the exterior was a very good idea. The r-value of the foam to prevent interior condensation would depend on the climate zone.
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Brettny
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# Posted: 25 Aug 2024 12:58am
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How much insulation do you have? In all reality no matter where you live trying to fit enough insulation in a 2x6 ceiling isnt enough.
Did any of the framing structure get wet durring your build? If so I would spray everything with white vinegar and leave windows open for a few weeks.
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Agirlandheraframe
Member
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# Posted: 25 Aug 2024 02:08am
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I’m located in Vermont, looks like a zone 6
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ICC
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# Posted: 25 Aug 2024 03:27am - Edited by: ICC
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A-frames are sort of an oddity when it comes to whether or not the sloped walls are walls or roofs. A-frames are hardly ever mentioned in the code books. FWIW, I interpret them to be more like roofs when it comes to insulation.
The idea is to have enough r-value of exterior foam to keep the interior surface of the sheathing above the dew point temperature (when it is cold outside and the interior is being heated. Table R806.5 in the IRC lists climate zone 6 as needing R-25 exterior foam. That is 5" of typical XPS rigid foam.
Would this be used in the coldest of Vermont weather? You didn't state if this was a full time residence or a recreational part time property. If not to ne used in the coldest weather the R-value could be scaled back I suppose. How much? I don't know off hand.
One can also use foam on the outside with some other insulation inside. Usually 2/3 of total R-value outside, 2/3 inside, IIRC. The interior (batts?) help to keep the inside surface of the sheathing warm, and reducing the needed exterior foam R-value.
That is some general insulation info. What to do with your A-frame is up for some brainstorming. Removing sprayed in foam is a daunting task, IMO. I might remove the exterior roofing and apply sheets of XPS foam. Then overlay that with a layer of OSB or plywood sheathing, secured with long screws through and into the 2x6 rafters. Then the metal or shingles. Inside I might leave some or all the interior foam and cover it with drywall, t&g boards, sheet panels, or whatever suits your aesthetics.
???
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ICC
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# Posted: 25 Aug 2024 03:40am
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2x6 framing does not provide sufficient space to insulate and vent using only the interior side. Perhaps sufficient foam thickness could be infilled from the inside by using a complete spray in filling of all the rafter nays? That may not ne enough depending on the per inch R-value of open cell vs closed cell. An additional inch or so of XPS applied inside and then covered with panelling or boards could be done? Then the existing roofing need not be touched.
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