The bonus room is the most reliably uncomfortable room in a modern house, and it is the same story on the newer builds around Diamond Valley as it is anywhere else in Alberta — except that here the room is usually facing the wind. Bonus room spray foam insulation in Diamond Valley is a job with five surfaces to get right, and the floor is the one people forget.
Five surfaces, not four
A normal upstairs bedroom has two or three exterior surfaces. A bonus room over a garage has, in effect, five: two end walls, two sloped or knee-wall sides, and a floor that sits on top of an unheated garage. It is the only habitable room in the house with cold space directly beneath it as well as beside and above it.
That is the whole reason it behaves differently. The heating system was sized and ducted as though it were a bedroom, and it has roughly twice the exposure of one.
The floor over the garage
The floor is a joist assembly with a heated room above and an unheated garage below. In most builds it received batt between the joists and nothing else. Batt without an air seal does not address the real mechanism, which is garage air moving up into the floor cavity and travelling sideways into the room — including out under the baseboards at the edges.
Worse, the perimeter of that floor assembly commonly sits over the garage wall top plate and is open to the wall cavity, or on a cantilevered section it overhangs outside the garage wall entirely, which puts part of the floor directly over outdoor air. That cantilever is where it is coldest and it is almost never sealed.
Closed-cell applied from the garage side to the underside of the subfloor adheres to it, seals the joist bays, closes the perimeter and the cantilever, and does it in one operation. A thermal barrier over the foam is required in the garage, which for most builds means the drywall ceiling that was there anyway.
Knee walls and the triangles behind them
The sloped sides of a bonus room are knee walls with a small attic triangle behind each one. Those triangles connect to the main attic, so they are at outdoor temperature. A knee wall with batt in it and nothing on the attic side has insulation with open air on one face, which means air can flow through and around it.
The fix is to seal and insulate the knee wall as a true exterior wall, close the floor cavity at its base — the joists under the knee wall run from the cold triangle straight into the heated room, which is another path nobody blocks — and treat the sloped section above as an unvented roof assembly against the deck.
The west wind and the gable end
On an exposed site the bonus room is high on the building and typically has a gable end facing the weather. Wind pressure on that gable drives air into every unsealed joint in the assembly, and a chinook brings the pressure and a temperature swing at the same time. A room with five exposed surfaces and a wind load is why the complaint is seasonal rather than constant.
Say which problem you have
Cold in winter and hot in summer are both common in this room and they do not always have the same cause. Cold is usually the floor and the knee wall base. Hot is usually solar gain through the gable glazing plus a sloped ceiling with inadequate depth. Both benefit from the air sealing, but the priority order differs, so tell us which one is actually driving the call.
The crew on your job
Bonus room spray foam insulation Diamond Valley is quoted, scheduled and sprayed by us. Our own installers are on the job, and the number you are given is the number we stand behind.
Bonus Room Spray Foam Insulation Diamond Valley: Common Questions
Why is the bonus room always the worst room? Because it has cold space on five sides including below it, while being heated as though it were an ordinary bedroom.
Should the garage ceiling be insulated or the room floor? They are the same assembly. It is sprayed from the garage side onto the underside of the floor.
What about the slanted walls? Those are knee walls with cold attic behind them, and the floor joists running beneath them are an open path into the room. Both need attention.
How much does bonus room spray foam insulation cost in Diamond Valley? Priced per board foot across the surfaces included, so the scope decides it. A floor-only job is a much smaller number than floor, knee walls and slopes together.
How do I choose a contractor for a bonus room in Diamond Valley? Ask them to list the five surfaces and say what they will do at the base of the knee walls. That answer separates people who have solved this room from people who have insulated one.
Size the assembly with the R-value calculator, then get a free Diamond Valley quote. More on Bonus Room Spray Foam Insulation Alberta province-wide.