KNOW HOW

Warming Up a Bedroom for Baby Above the Garage

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By Jeanne Huber
Special to The Washington Post
Thursday, September 15, 2005

Q We are turning a room above the garage into a nursery for our new baby. It's cold in there in the winter, even though it has a working radiator. What can we do to the room, or even the garage, to warm up the nursery?

A The quick answer is to roll out a thick carpet and plug in a portable heater with a thermostat and a shielded heating element. Consider an oil-filled type that resembles a small radiator.

The long answer is, of course, more complicated. Spare rooms over garages are notoriously difficult to heat in the winter and to cool in the summer. It's the number one complaint to Energy Services Group, a company in Wilmington, Del., that advises builders and homeowners in the Washington area about energy issues. Several factors work together to cause the problem.

First, an over-the-garage room tends to need more in the way of heating and cooling because most of its exterior walls are exposed to the outside. Rooms in the rest of the house usually share more walls with adjoining rooms.

Second, when a room is built over a garage, the whole idea is to take advantage of otherwise wasted space. The original plan almost always focuses on the space needed on the first floor for parking and maybe a workshop or storage. Over that goes a peaked roof. The room over the garage fits in between, with what's known as "knee walls" running where the space to stand up or at least tuck in a bed or storage space runs out at the base of the sloped roof. The space behind the knee walls, which is often left accessible for storage, may be the source of your problem.

To make your room easier to heat and cool, all six sides -- the walls, floor and ceiling -- need insulation, except in the rare circumstance when the garage space underneath is kept heated or cooled. Whoever finished your room may have neglected insulation altogether. But it's probably more likely that the crew tried to do the right thing and stuffed fiberglass batts into the ceiling, between wall studs and perhaps even between floor joists under the room. And yet your room may still be difficult to heat and cool, because even many seasoned builders don't realize that fiberglass batts aren't effective unless they are in a sealed cavity. Otherwise, cold air can flow through the insulation and undermine its purpose. In your case, outdoor-temperature air is probably flowing into the insulation from the garage or from the areas behind the knee walls. To fix the problem, treat space behind the knee walls as part of your room. As a bonus, you'll get storage space that doesn't freeze or overheat.

If you don't have access doors in the knee walls, use an electronic stud finder or thump with a fist along the drywall and note where the sound changes. Use a utility knife to carefully cut out enough of the drywall between two studs to give you a way into the hidden space beyond. Once there, you probably will be able to see what, if any, insulation is in the room's ceiling or floor. If there is no insulation between the floor joists, you will need to open up the garage ceiling and insulate the space from that side. But if you see insulation only where the room is over the garage, you can fill the gaps from the knee wall area. Either way, you also need to enclose the insulation by reinstalling drywall on the garage ceiling and attaching plywood or insulated sheathing to the floor of the knee wall area.

Also insulate the roof of the knee wall area and any uninsulated sections of the garage's end walls. Use fiberglass batts between rafters or studs, and then enclose the wall by nailing or gluing on insulated sheathing. (To maintain an air gap between the insulation and the back of the roof sheathing, stuff special baffles made for this purpose between the rafters before you install the batts.) Finally, caulk all seams in both the knee wall area and the garage ceiling to ensure a good seal. Dominion, an energy company that supplies electricity to parts of Virginia and North Carolina, provides clear drawings and instructions at its Web site, http://www.dom.com/ . (Type "solving comfort problems" into the search box.) Even with these improvements, your room may still be more difficult to heat and cool than the rest of your house. Perhaps the thermostat reads the temperature in an easier-to-heat room, or the person who calculated the heating needs for the room forgot to factor in the heat lost in pipes along the way. A plumber may be able to advise you whether it makes sense to put the garage radiator on a separate piping system, with its own thermostat.

If that's prohibitively expensive, you're back to where we started, except that your monthly electric bill shouldn't be so high. Find a nice, thick carpet, insulated window covers and a booster heater. Area rugs are better than wall-to-wall carpeting for children's rooms because you can send them out for a more thorough cleaning.

By the Way

If you're planning to use this space as a bedroom, be sure to install a carbon monoxide detector and avoid warming cars in the garage, even when the big garage door is open. Cold car engines generate considerable carbon monoxide, and wind blowing in through a big garage door can pressurize the space, forcing garage air into the rest of the house.


© 2005 The Washington Post Company

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