Should I vent a suspended floor over an uninsulated slab?
Justine Wysong| Posted inEnergy Efficiency and Durabilityon
I live in zone 7. We are building an addition to our house in our barn. We have put 2″ of rigid insulation in between the floor joist, seal with spray foam and fiil space under joist with cellulose. Our friend told us we should place a vent under the sub floor to prevent condensation. I’m concerned that putting in a vent will create a draft under the floor. Do we need a vent?
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Replies
Justine: It sounds like you have a crawl space under your floor. I believe the consensus is to condition that space (heat it) and lay a true vapor barrier on the ground. That vapor barrier needs to be sealed against the wall with something like Tremco acoustical sealant and some kind of means to mechanically attach it, if possible (lath nailing it down, for ex). Maybe I am not interpreting what you have correctly. If it is a crawl space, search here for that term and you should get your answer. I could be wrong, so check that.
Justine,
Did you install the floor joists directly on the existing slab? Or is there enough room for a person to crawl between the existing slab and the new floor joists?