Fix the coldest room in the house
Garage & Bonus Room Insulation in Grand Rapids, MI
Sealing and insulating the floor, kneewalls and ceiling of the room over your garage.
- Free on-site estimates across Grand Rapids and Kent County
- Every area itemized with foam type, thickness and R-value
- Leaks, damp framing and old wiring pointed out before we insulate
The Room Over the Garage
Garage & Bonus Room Insulation fixes the classic cold room of the suburbs: the bedroom or bonus room built over an attached garage. Much of the Grand Rapids area was built from the 1970s on; the median home in Kentwood dates to 1983 and in Walker to 1984 (ACS via Point2), and many of those houses have a room over a two- or three-car garage. The floor of that room sits over unheated space, its sides are kneewalls with attic behind them, and the ceiling is often a short slope. Each of those surfaces can leak.
Why batts often fail here
Builders usually put fiberglass batts in the garage ceiling. Batts that sag, have gaps or do not touch the subfloor leave a layer of cold air under the room, and the open ends of the floor joists let attic air flow right through. The result is a cold floor in winter and a hot room in summer.
How we fix it
The most reliable fix is spray foam against the underside of the bonus room floor, from the garage, which seals and insulates in one step. Where the drywall should stay, we can dense-pack the joist bays through small holes instead. We also block and seal the joist ends where they open to the attic, and seal and insulate the kneewalls and sloped ceiling from the attic side.
Insulating the garage itself
If you use the garage as a workshop or keep it warm in winter, the walls and ceiling can be foamed or insulated too. Closed-cell foam on the garage door side walls and ceiling also cuts noise. Garages need fire-rated coverings over foam in many cases; your building department has the final word, and we plan for it.
Rooms over porches and cantilevers
The same problem shows up over porches and in floors that hang past the foundation. We treat them the same way: seal and insulate the floor from below.
Rebates
DTE lists $25 for at least 100 square feet of kneewall insulation and $50 for 100 square feet of floor insulation in homes it heats, and a $250 bonus when one of those is added to attic insulation installed between September 15 and December 15, 2026.
Summer heat too
The same leaks that make a bonus room cold in January make it the hottest room in July, when Grand Rapids highs average around 83 degrees. Sealing and insulating fixes both seasons.
Call (616) 219-1886 or book a visit and we will find out why that room stays cold. Get a free estimate
What This Covers
Garage and bonus room work.
Garage ceiling foam
Foam against the floor above, sprayed from the garage.
Joist-end blocking
Closing floor cavities where they open to the attic.
Kneewalls and slopes
Sealing and insulating the sides and ceiling of the room.
Heated garage walls
Foam or batts for a garage used as a shop.
Garage & Bonus Room Cost Ranges
| Job | Range and source |
|---|---|
| Open-cell spray foam, installed | $1.50 to $3.50 per sq ft (HomeGuide) |
| Closed-cell spray foam, installed | $3.00 to $5.00 per sq ft (HomeGuide) |
| Air sealing | $350 to $3,000 (HomeGuide) |
| Blown-in, per sq ft | $1.00 to $2.80 (HomeGuide); $1.65 to $3.80 (Fixr) |
| Typical spray foam minimum | $1,000 to $2,000+ (HomeGuide) |
These general national ranges come from HomeGuide (2025-2026) and Fixr (2025) and are not bonus-room specific. Room size, access from the garage, drywall and kneewall layout decide the cost. We measure and give you a written estimate, and the number on it is the price.
How It Works
1. Find the leaks
We check the garage ceiling, joist ends, kneewalls and slope.
2. Quote
Each surface is listed with material, thickness and price.
3. Seal and insulate
Joist ends blocked, floor foamed or filled, kneewalls sealed.
4. Close up
Holes patched, coverings replaced and the garage cleaned.
Garage & Bonus Room Insulation Questions
Why is my room over the garage so cold?
Usually because the floor batts have gaps and the joist cavities open to the attic, so cold air flows under the room. Sealing and insulating the floor fixes it.
Do you have to remove the garage ceiling?
Not always. Foam needs open framing, but dense-pack can go in through small holes if the drywall stays.
Should I insulate my garage door?
If the garage is heated, an insulated door helps. We insulate walls and ceilings; doors are a separate trade.
Is the garage ceiling a fire separation?
Yes. Ceilings under living space need the right drywall, and foam needs proper covering. We keep that intact.
Garage & Bonus Room Insulation Service Areas
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Get a Garage & Bonus Room Insulation Estimate
Free bonus room estimates in Grand Rapids and Kent County.