Q–We’re considering remodeling our basement, which is now unfinished space. One of the concerns we have is heating and cooling the new space.
We have a forced-air heating and central air conditioning system that’s about 5 years old. Should we use this to take care of the basement? Or would that tax the current system? Should we consider a separate heating and cooling system?
The reason we are concerned is we don’t think we’ll be using the space much, except on weekends. So we don’t want to spend a lot of money heating or cooling the space when we’re not down there.
Any suggestions?
via e-mail
A–Heating and cooling your basement shouldn’t be a complicated matter but there are some steps you can take to make it energy-efficient space, says Mark Burger, a senior technology specialist with the U.S. Department of Energy’s Chicago Regional Support Office.
First, plan on using your current heating and cooling system, he says.
“Most systems are oversized for their homes, and there are probably at least a couple of duct openings already in the unfinished basement,” Burger adds. “So unless the finished space is going to be huge, you won’t have any problems with the existing system.”
Going to a separate system to heat and cool the basement would cost well over $1,000, and that would take years to recoup as far as energy savings, he noted.
Next, during the construction of the basement space, Burger suggests you consider insulating the walls with a 2-inch-thick polystyrene rigid board, which will give you an insulation value of R-10, or with 3 1/2 inches of insulation blanket, which will give you an insulation value of R-13. (Check with your local hardware or home improvement store on installing protective vapor barriers against moisture in the basement.)
The insulation will not only make the finished basement space feel more comfortable, but also will keep it warmer on the living levels above, Burger says.
“A lot of cold air infiltrates a home through the basement,” he says. “That makes the first floor feel less comfortable and also causes the heating system to work harder.”
The insulation will also prevent warm air from escaping from the basement.
If you have single-pane windows in the basement, consider upgrading to new dual-pane windows or have storm windows constructed for the outside of the existing windows, Burger says. That will also help keep the space warm and comfortable.
In addition, if you have a walk-out door in the basement, seal it with weatherstripping and a door sweep at the bottom. Also, seal doors between the finished space and unfinished areas of the basement.
After the basement is finished, Burger says, you can simply close the basement registers when space is not in use so the heated or cooled air is redirected to the upper living levels.
Because a good portion of most basements is below grade, cellars remain cool even during the warmest summer months. That’s an advantage for air conditioning, and it shouldn’t take very long for the space to feel comfortable when you want to use it. Try opening the registers an hour or so before you use the basement in the summer, Burger says.
On the other hand, it will take longer for the basement to warm up because of that natural coolness. So Burger suggests that you open the registers on Friday nights in cold weather so that the space is warm and comfy for the weekend.
“The more insulation you have down there, the faster it will warm up,” he says.
You may also want to experiment and leave the registers open constantly. Then compare this year’s gas and electric bills with last year’s. “You may notice only a slight increase in costs,” Burger says. “In other words, I don’t think you’ll see a whole lot of savings by shutting down the registers, especially if you insulate and seal the basement well.”
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