Fiberglass over a slab
rickmonserud42
| Posted in Energy Efficiency and Durability on
We are bumping out the garage and turning the exiting garage in to a family room. In the process we are framing on the slab to meet up with the floor in the house. We have put down a vapor barrier (6 mil plastic). The plans call for R19 Fiberglass in the cavities. My concern is condensation within the system (tile will be the finished floor.) also should this space be vented in some manner as well? This project is in Wisconsin so there is a great deal of temperature change. I feel that we should be putting down minimum 1” foam and air sealing all joints.
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Replies
Richard,
You are right to question the use of fiberglass insulation in this application. Instead of fiberglass, install XPS on top of the slab before you begin framing; I would aim for at least R-20, which means you need 4 inches of XPS. Install in multiple layers with staggered seams; the seams on the top layer should be sealed with Tyvek tape, red contractors' tape, or spray foam.