The bedroom over the garage runs cold because it is surrounded by cold on almost every side. An unheated garage sits under the floor, outside walls wrap around it, and an attic or roof sits close overhead. If the floor is thinly insulated or leaky, that room loses heat faster than the rest of the house can replace it.
Rooms built over attached garages are common in Spokane Valley, Liberty Lake, North Spokane and the newer neighborhoods of Post Falls and Hayden, especially in homes built from the 1970s through the 1990s. They make great guest rooms and bonus rooms, right up until the first week of real cold.
Why is the room over the garage colder than the rest of the house?
Most rooms in your home share walls, floors and ceilings with other heated rooms. Heat that leaves one room mostly ends up in the room next door. The room over the garage does not get that help.
Look at what surrounds it. Below the floor is a garage that sits near outdoor temperature for much of the winter, with a big door that opens to the cold every time someone drives in or out. Two or three of the room's walls are often exterior walls. Above it, there may be a low attic, a sloped ceiling or a short knee wall with attic space behind it.
In a Climate Zone 5 winter like ours, that matters. The National Weather Service puts normal heating degree days at Spokane Airport at 6,463 a year, which is a way of saying our homes spend a long stretch of the year working to stay warm. A room with cold on every side feels that strain first.
What is going on in the floor between the garage and the bedroom?
The floor is usually the biggest problem, and it is the one most people never think about. When these homes were built, the garage ceiling was often treated like any other ceiling: a layer of batts pushed up between the joists, then drywall. Over the years a few common problems show up.
- Batts that sag or fall away. Insulation stapled up into a floor cavity can drop away from the subfloor above it, leaving an air gap between the insulation and the floor you walk on.
- Gaps at the edges. Batts rarely fit tight around plumbing, wiring, ducts and blocking, and cold air finds every gap.
- Open ends at the band joist. Where the floor joists meet the outside wall, the cavities can be loosely filled or open to outside air, so cold air moves right through the floor.
- Less insulation than the floor needs. ENERGY STAR recommends R-30 for floors over unheated space in our climate zone. Many older garage ceilings fall well short of that.
The result is a floor that feels cold under bare feet, and a room where the warm air you send in keeps leaking its heat down into the garage.
Why does the room still feel cold when the thermostat looks fine?
Comfort depends on more than air temperature. Your body also trades heat with the surfaces around you. When the floor and walls are cold, you lose heat to them by radiation, the same way you feel a chill standing next to a cold window.
That is why a guest can be under a blanket in a room that reads close to normal and still say the room feels cold. The air may be fine near the middle of the room while the floor, the outside walls and the sloped ceiling are all pulling heat away from anyone sitting near them.
The thermostat usually sits in a hallway or main living area, so the furnace shuts off once the main floor is warm, whether or not that far bedroom has caught up.
Could the ductwork be part of the problem?
Often, yes. The room over the garage is usually at the end of a long duct run, and those ducts may pass through the garage ceiling, an attic or a knee wall space on the way. Air that travels through cold spaces cools off before it reaches the register.
Leaks make it worse. ENERGY STAR estimates that about 20 to 30 percent of the air moving through a typical duct system is lost to leaks, holes and poorly connected ducts. When the last room on the line gets weak, lukewarm airflow, it has a hard time keeping up even before you count the cold floor.
If you suspect a duct issue, such as a register that barely blows or a disconnected run, an HVAC contractor is the right call for the ducts themselves. Insulation and air sealing around the room help the heat that does arrive stay there.
What about the walls and ceiling of that room?
The floor gets the most attention, but the rest of the room counts too. Exterior walls in homes from this era may have thin, settled or patchy insulation. Rooms tucked under the roof often have sloped ceilings with limited space for insulation, and short knee walls with attic space right behind them.
Warm air rises, so heat in that room pushes up toward the ceiling and escapes through any gaps it finds: around recessed lights, an attic access panel, top plates and wiring holes. Those hidden openings are called attic bypasses, and sealing them is a different job from adding insulation. Both jobs matter in a room like this.
Why do Spokane and North Idaho homes notice this so much?
Our winters are long, and our cold snaps can sit on the region for days. In late fall and winter, valley temperature inversions often bring stretches of low cloud and little sun to the Spokane area, so a room that might warm up a bit on a bright afternoon gets no help at all.
The kind of homes we have plays a part too. Tri-levels and two-story homes with bonus rooms over attached garages went up across Spokane Valley, Liberty Lake, Mead and North Spokane, and in Post Falls, Hayden and Rathdrum. Many were built to the standards of their day, which asked for far less insulation than what ENERGY STAR recommends now. If your home is one of them, the room over the garage is a natural place to start looking.
What can you do before your Thanksgiving guests arrive?
A real fix takes planning, but a few simple steps can make the room more comfortable for this year's visitors.
- Keep the garage door closed. Every open-door minute lets cold air flood the space under the room.
- Open the register all the way and make sure no furniture, rug or bedding is blocking it.
- Leave the bedroom door open during the day so warmer air from the rest of the house can drift in, then close it at night.
- Put down a thick rug to take the edge off a cold floor.
- Add an extra layer to the bed and leave a note telling guests where the spare blankets are.
- Check the attic access if it is in or near that room. A loose panel with nothing on top lets warm air straight out.
These help for a holiday weekend, but the floor, walls and ceiling stay the same underneath.
How do you actually warm up a room over the garage?
The lasting fix starts with finding out where the heat is going. A room over a garage can lose heat through the floor, the outside walls, the ceiling and the gaps in between, and the right plan depends on which of those is worst in your home.
Depending on what an inspection finds, the work might include:
- The floor over the garage. Filling the floor cavities fully so insulation sits tight against the subfloor, with the edges and band joist area sealed. The method depends on whether the garage ceiling is open or finished with drywall, and spray foam is one option where it fits.
- The exterior walls. Premium Injection Wall Foam goes in from the outside through small access holes, behind a removed strip of siding or in the mortar joints on brick. The holes are plugged and patched, and your interior drywall stays in place.
- The attic or ceiling above. Air Sealing to close bypasses, then Blown-In Attic Insulation to bring the attic closer to the R-49 to R-60 ENERGY STAR recommends for our climate zone.
When several parts of the house need attention, the Ultimate Home Comfort approach looks at walls, attic and air sealing together so the whole house gets more even.
Quick answers about the cold room over the garage
Is it normal for the room over the garage to be the coldest room? Yes, it is very common, because that room has cold on more sides than any other room in the house. Common does not mean you have to live with it.
Will a space heater fix it? A space heater can warm the air for a night, but it does nothing about the cold floor and walls pulling heat away. The room cools off again as soon as it shuts off.
Should I just turn the thermostat up? Turning it up makes the rest of the house warmer than you want while the far room still lags. It also keeps the furnace running longer.
Is the problem my windows? Windows can play a part, especially older ones with worn seals. In most rooms over garages, though, the floor, outside walls and ceiling add up to far more surface than the windows.
Can the floor be insulated without tearing up the bedroom? Usually the work happens from the garage side or the outside, so the bedroom flooring stays where it is. An inspection tells you which approach fits your floor.
What happens at a free insulation inspection?
At a free in-home insulation inspection, we measure your walls and attic, take photos of what we find, and give you a written price. For a room over a garage, that means looking at the floor and garage ceiling, the outside walls and the attic or knee wall spaces around the room.
You see what we see, and you get a clear picture of where that room is losing heat. Financing is available through independent lending partners, subject to lender approval, if you want to spread out the cost.
Give your guests a warmer room this year
The room over the garage does not have to be the one nobody wants to sleep in. Once you know whether the floor, the walls or the ceiling is doing the most damage, you can fix the right thing first and stop guessing. Schedule a free insulation inspection with USA Insulation of Spokane-CDA, and we will show you exactly where that room is losing its heat.
