I have a barn in southern Colorado Zone 6 that I will be insulating. The center section is higher so I will add floor joists and an OSB floor for use as a storage loft. In this section I would like to use fiberglass batts to save some money. My thought was to put tin or sheetrock on the bottom, the batts between the joists and OSB on top for decking.. With the Plastic vapor barrier down towards the warm shop air..
On the two sides I will have 2″ of spray foam sprayed on the bottom of the lid which is tin on top of OSB. I may or may not add a ceiling here later
Is fiberglass ok for that center section since it’s unventilated? Or do I need to go with spray foam? If so where does the spray foam go? Way up high underneath the lid or on the bottom side of the loft floor? Thanks
Replies
Where are the new floor joists going? same level as the bottom of the side right triangle trusses?
there are issues you can avoid that can come with a combination of vented and unvented roof assemblies.
Are you saying your plan is to spray the underside of the roof deck in the lower right triangle truss parts?
and then continue up the elevated walls with windows in the upper part? If so, it might make more sense to either insulate the bottom of the upper trusses (ceiling of your new loft space) or continue up the center part of the higher roof.
The barn will be used as a shop. The loft will be for storage. No hay or feed will be stored in the barn. The barn has a 12 x12 rollup on each end. I plan on taking out one of those and putting a smaller 12x8 in it's place. That will give me headroom to drop the floor of the loft down to the 12' level to match the height of the bottom of the trusses on each side. The loft floor will run about 25' at that level but when I reach the track for the other rollup door will have to jog up about 18" . At that point the floor will be above the track.
My plan is to have the walls and lid (it's tin on top of OSB) also sprayed with 2" of closed cell foam. For the loft area I would like to just insulate the floor not the sides and roof if possible. I could go fiberglass here and save some money but I think I would have to vent the loft to do so. The other option is to spray both the underside of the roof and sidewalls of the loft with foam.
Heat will be a woodstove for now and later add a propane heater- either forced air or radiant tube.
Thanks for the reply.
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If you are not going to spray foam up the walls and along the upper roof, you would want to fiberglass not only the floor, but the walls from your new floor up to where these walls meet the side roof, and run a vapor barrier on the inside of each (inside of the heated space, not the storage space) and provide for ventilation of your storage space to let the roof deck breathe.