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Finished Basements

Pour a concrete floor connecting a house's foundation walls and what do you have? A basement. So simple. That's why an unfinished basement is the least expensive living area to build in a house.

But an unfinished basement really isn't a living area, is it? Mainly, it's storage, doubling as the involuntary destination for rambunctious kids on a rainy day.

Which is a shame, really, because well-constructed basements have many characteristics that make them ideal for everyday uses. Basements are quiet, naturally cool and -- because they are separate from the primary living area -- inherently private. Also, the main plumbing, heating and air conditioning equipment is usually located there already, making connections, additions and alterations to these systems relatively easy when the changes support basement upgrades.

The key areas to consider when building a finished basement are insulation, floors, heating and air conditioning, walls and ceilings, and lighting. Be sure to ask for ENERGY STAR® when purchasing products for any of these areas. ENERGY STAR qualified products meet strict energy efficiency guidelines set by the U.S. Environmental Protection Agency (EPA) and U.S. Department of Energy (DOE). ENERGY STAR also provides guidance on insulation levels.

Keep It Cozy

Insulation separates the perpetually cool foundation walls from the mild interior, creating a much more comfortable living area at low cost. Evenly heating and cooling the basement then becomes easier -- and cheaper. According to DOE, typical annual energy savings achieved by properly insulating a 1,500-square-foot basement range from $250/year in Washington, D.C. and St. Louis, to $400/year in Minneapolis.

The best basement insulation is generally some type of rigid polystyrene glued directly against the foundation wall. Insulation joints should be sealed with mastic and mesh tape so the warm, moist basement air will not come into contact with the cool basement wall, which can lead to mold.

For new homes, rigid insulation glued to the outside foundation usually works best. Make sure your builder leaves a 6-inch gap between the top of the outside insulation and any wood construction. Otherwise, termites can use the insulation as a pathway into your home.

Conventional fiberglass batt insulation is a good choice only if the builder guarantees walls will not leak or sweat. Do not use batt insulation that has any type of vapor barrier or vinyl or aluminum surface. The Building Science Consortium has found this common construction to be unsuitable for basements.

Poorly installed insulation will compound moisture problems. Wet insulation dries more slowly than uninsulated surfaces, which can increase the potential for mold and damage materials. Also, damp insulation won't insulate as well as dry.

To find out more, download DOE's excellent fact sheet on insulating basement walls (pdf). This fact sheet also contains some general guidelines for constructing foundations that prevent moisture problems.

One of the most important things you can do to control moisture in basements is to look outdoors. Often, good outside drainage and maintenance are enough to keep water out of a well-built basement. Make sure the yard is graded so that rainwater flows away from the foundation, gutters are clear and downspouts work properly.

[IMAGE: Built-in bookshelves can be a beautiful touch to a finished basement]

Firm and Dry Footing

There are many flooring options, but the most comfortable involve a subfloor installed above the concrete floor. The subfloor keeps the finished floor away from direct contact with the cool concrete. This not only softens and warms the finished floor, but also keeps it dry and, if it gets wet from spills or plumbing mishaps, allows it to dry out. You can apply almost any type of finished floor on top of the subfloor: bamboo, wood, carpet, linoleum or tile. Before installing your flooring, caulk all cracks in the floor to minimize moisture problems.Avoid installing carpet directly on basement concrete, since wet carpet is a perfect home for mold. But if you are on a tight budget and the floor doesn't have inherent dampness problems, use carpet without an attached underpadding. A separate rubber based underpadding resists humidity more effectively and will dry more easily if flooding occurs.

You can also leave the floor unfinished, which is a great option for rooms where the hard, cool feel of concrete isn't an issue, such as exercise rooms, laundry rooms and workshops. Moisture and flooding aren't as big a problem with concrete, and cleanup and maintenance are easy.

You can warm up any concrete floor by putting radiant floor heating in the slab. Radiant floor heating uses hot water coils (or heat-generating electrical wires) buried beneath the floor. This "heat for your feet" is comfortable and efficient and, because it doesn't blow hot air, keeps dust down as well.

You can also decorate the concrete if you want to give the finish some style. With a little forethought, both a radiant floor heating system and the decorative concrete can be integrated into the basement slab when it is poured. In homes with walkout basements, you can "bring the outside in" by choosing the same decorative concrete pattern for both the basement floor and the patio.

Don't Go Hot and Cold

Humidity is a concern in many basements, but don't let that dampen your enthusiasm. Once air leaks are sealed, high humidity can be controlled easily with proper planning and good HVAC design.

Hot air from the furnace will often control humidity in the winter. Make it more efficient by positioning the hot air ducts at floor level. As long as your air conditioner takes some return air from the basement, the unit should control humidity during the summer as well. But if the air conditioner alone doesn't do it, install a portable ENERGY STAR qualified dehumidifier.

On mild spring and fall days, a dehumidifier often provides enough heat to take the chill out while it dehumidifies. Combining dehumidification and heating this way will actually reduce your energy use, which means you'll pay less on your energy bills.

Comfort and moisture issues shouldn't be problems if your contractor uses best practices for the heating and air conditioning system. PATH has developed a “Tech Set” for HVAC, which provides builders and homeowners direction in selecting innovative technologies and best practices..

If your contractor's recommendations are consistent with the Tech Set practices, you should be in good shape.

[IMAGE: Basements are perfect for wine cellars]

Walls and Ceilings

When your contractor frames the walls, the studs shouldn't touch the foundation wall because they can absorb moisture from the wall. Rather, they should be set against the rigid foam insulation that covers the wall.

Before the finishing interior wall is installed, your contractor should provide wiring for electrical outlets and switches. If the contractor uses drywall, check that it is secured with drywall screws rather then nails to keep nail heads from showing (commonly called "nail pop").

If there's a little wiggle room in your budget, consider installing the new paperless drywall material. It's highly mold-resistant, which makes it ideal for basements. Acoustic tiles are a good choice for basement ceilings. You'll be able to access plumbing and electrical wiring without having to demolish parts of the ceiling, and the individual panels can be easily replaced if water upstairs leaks through.

If you plan a home theater or a music room, acoustic panels work well for both walls and ceilings. Install acoustic batts between wall studs and ceiling joists, cover them with acoustic panels and add two layers of drywall with offset joints.

Let the Light Shine

Lighting -- and that includes natural, outside light, or "daylighting" -- makes all the difference between a cozy lair and a sterile space.

Daylighting is best built into the basement from the beginning since it is very expensive to add or increase the size of windows. If your basement isn't a walkout, window wells may be the best way to provide daylighting. These are often located high in the basement walls, which is great for comfort, since natural light sources usually produce less glare the higher they are.

Another proven but less conventional way to add daylighting is tubular skylights, also called solar tubes. Tubular skylights have a roof-mounted light collector, like a small skylight, that guides sunlight to a lens in the basement that spreads light evenly throughout the room. Some tubular skylights have integrated electrical lights so the fixture can provide light both day and night; some even regulate the amount of sunlight entering the room.

Plan electrical lighting in advance so fixtures and wiring for electrical outlets and switches can be placed appropriately.

The four commonly used types of electrical lighting are incandescent, compact fluorescent, fluorescent and halogen.

Once your basement is done, step back and look at what you've created. It's much more than an unorganized storage space ideal for hide-and-seek. After all that work, you have a comfortable, efficient, well-lit basement. Feels good, doesn't it?

Now send the kids upstairs so you can enjoy it in peace.


Radon is a colorless gas and known carcinogen that can seep into a home from the soil and rock below. Because it comes from the ground, radon levels are usually highest in basements. Health authorities like the Centers for Disease Control, the Surgeon General, the American Lung Association and the American Medical Association all agree that you should act as soon as possible to reduce the radon level if it is 4 pCi/L (picocuries per liter) or more.

A map from the EPA at shows expected ranges of radon levels throughout the country. Test the lowest level in your home if you have any reason to believe there are high levels of radon in your area. Radon detectors can be purchased at almost any hardware or grocery store. If readings are at or above 4 pCi/L, contact a local radon remediation contractor. (Look under "radon" in the Yellow Pages.) Generally, some type of venting is added to reduce radon to safe levels.

This article, Upgrading Below Grade, written by PATH originally appeared in the Fall 2005 Her Home.

Content updated on 11/18/2005

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