Garage Conversion

This is a homeowner forum question, not news, but it's worth understanding if you're thinking about turning a garage into living space. A contractor described a project converting a 23x23-foot garage into a heated and cooled room using a minisplit (a compact, ductless heat pump for heating and cooling). The garage walls are basic: 2x4 studs, exterior siding board with no housewrap or extra sheathing, and only thin fiberglass insulation inside, rated around R-11 (a low insulation value for walls). The building inspector said the room could count as a conversion of previously conditioned space, since an old propane heater was once installed there.

The clients want to keep costs down, so they are resisting the contractor's suggestion to add new sheathing, housewrap, and siding, or to upgrade the wall insulation with rigid foam. The contractor asked other builders whether just replacing the interior drywall and paneling, without touching the wall's insulation or exterior layers, would be an acceptable shortcut. Plans for the rest of the space included foam insulation and plywood over the concrete floor, and blown-in cellulose insulation in the attic rated at R-49 (a high insulation value, common in attics).

For a homeowner, the takeaway is that garage conversions often reveal weak spots in walls that were never built for full-time heating and cooling, and cutting corners on wall insulation and air sealing can leave a converted room less comfortable and more expensive to heat and cool than the rest of the house.