Basements are usually cool year-round—comfortably so in summer, a bit chilly in winter. Basements are often partially insulated by the ground around them, so your existing heating system should provide the moderate amount of heat needed for comfortable temperatures. It's always a good idea, though, to make your basement even more energy-efficient by wrapping walls in insulation with R-10 to R-19 values.
Your current cooling system probably does a sufficient job of keeping the basement comfortable during the hottest summer days. If you're having difficulty keeping a walk-out basement cool in summer, consult a heating and cooling contractor to determine whether you need a more powerful cooling system. You also could consider supplementing the current system with a window air-conditioner.
Many basements in homes cooled and heated by forced air already have the ductwork necessary to distribute the warmed or cooled air. If not, a technician can install ductwork relatively simply and inexpensively because a furnace is usually located on the lower level. Still, your basement may need a supplemental heat source. If you have a walk-out basement with large, unshaded, south-facing windows, you may need supplemental cooling as well.
If modifying or expanding the main heating and cooling system in your home is impractical, you still have options. In fact, some of the products listed may prove more efficient, especially if you won't be using your new space constantly.
Beyond traditional heating systems, you can consider other options, such as fireplaces, to make your basement a warm, dry, and more welcoming place. A fireplace not only makes a room more inviting, but when chosen wisely, can make it warmer during cold seasons.
Wood-Burning Fireplaces Most wood-burning fireplaces suck more hot air out of a room than they produce, so these fireplaces are valued more for their ambience. Airtight, wood-burning stoves—some that allow you to see the fire—can be a great way to heat your space, especially if you have a good source of wood to burn. They require lighting, stoking, ash cleaning, and the carrying in and out of messy fuel, though, so they're not for everyone.
Direct-Vent Gas FireplacesThese allow you to see the flames and be warmed by their radiant heat. Some include a fan to distribute warmed air, making them efficient as well as decorative. Regardless of the style you choose, you'll find these fireplaces in a variety of looks, sizes, heat-output levels, and prices. Plan to connect a direct-vent gas fireplace to existing gas lines; LP-fired models are also available. These units offer a combination of aesthetics, efficiency, safety, and ease of installation. They're vented to the outdoors with a short length of two-in-one pipe that carries out combustion byproducts and draws in fresh air for combustion. The pipe can make two right-angle turns without losing efficiency. You can choose a fireplace that's freestanding or ready for framing; its function may be decorative or to provide heat. A major advantage of having a gas fireplace in your home is that if your power fails, it can provide some heat (and some provide quite a lot—check the BTU output ratings of the units you're considering).
Ventless Gas Fireplaces (also called vent-free)Gas fireplaces exhaust combustion byproducts directly into the room. They're slightly more efficient than direct-vent units and are even easier to install, but they deplete the room's oxygen supply, produce fumes that can be a health hazard, and are more risky for basement spaces. Some states have banned their use. Most of today's ventless gas fireplaces are required to include an oxygen-depletion sensor (ODS), a safety feature that warns if oxygen levels in the room are becoming low. For health reasons, you're much better off with a direct-vent appliance.
If you plan to finish your basement floor with stone or tile, consider installing a radiant heating system first. These systems not only warm the floor, but increase the overall temperature of the room, often eliminating the need for additional heaters. You can install a radiant heating system yourself—they are available at most home centers—or you can hire a flooring professional to install the system for you.
For rooms where you plan to use other finish flooring materials, such as carpeting, consider installing a wood subfloor with sleepers (floor joists that rest directly on the concrete slab). Use sleepers to protect a floor from condensation or as an alternative to a liquid leveler if you don't want to fix cracks, tilts, or imperfections. You can also install sleepers if you want to insulate the floor. You must install a wood subfloor if your finished floor has to be nailed down.