Basement ceiling insulation is a great way to improve your home's energy efficiency and lower your bills. However, there are some situations where it is not advisable. Here's an overview of the pros and cons of this approach as well as the different types of basement ceiling insulation available.
Do you know how lucky you are? If you’re reading this article, you probably own a home with a basement. Not all houses have basements. While they are common in the northeastern and Midwestern parts of the United States, they are fairly rare in the south and along the coasts. There are many reasons for this. In the swampy south, as well as near the ocean, the vast amounts of water in the ground make basements impractical. They are also expensive to build, which is why many structures built after World War II, when mass-produced, “cookie-cutter” architecture was born, don’t include them.
The fact is, in colder climates, basements serve an important purpose. In addition to housing furnaces, basements shelter pipes from the extreme cold, which prevents them from freezing and bursting. As functional as basements are today, they were even more so the further back in history you go. They were originally built as places to store food, wine, water, root vegetables and other consumables before refrigerators were invented. From there, basements evolved into laundry rooms and a place to store excess possessions of all kinds.
Today, basements are often used as an extension of a home’s living space. Some homeowners have even turned them into “finished basements,” which are areas made to be just as inviting and habitable as the rest of house. However, like most things, basements have both pros and cons. There’s a good reason they were once used as refrigerators: they’re cold. This coldness poses challenges for people wanting to hang out in them without spending an arm and a leg on heating. It also causes problems for homeowners who don’t use their basements as living space. The reason? Thermodynamics.
The laws of thermodynamics recognize that heat “chases” cold, and that it does so at a speed that is proportional to the difference between the hot and cold temperatures. In other words, the colder it is in your basement, the faster heat will leak into it from the floors above. And, if it’s even colder outside, the heat will continue to press outward. Meanwhile, your heating bill will go through the roof.
Is insulation the answer? It depends. If you do use your basement as a living space – a home theater, a playroom, or a guest bedroom, for example – the answer is no. Ceiling insulation helps stop heat from leaking into the basement from the floors above, which means it makes the basement colder – significantly so. If you plan to use your basement as a haven for humans, your best bet is to insulate the walls and the floor. This will allow warmth to continue traveling down from upstairs, and help stop it from escaping to the outdoors.
If, on the other hand, no one spends much time in your basement, there is a good chance insulating its ceiling is a wise investment. But first, there are a few more questions you should ask. Is your house located in a dry climate? Does your basement appear to be free of significant moisture? If you can check those two boxes as well, it is even more likely you should proceed. However, as tempting as it may be to stop reading here and head straight to your local home improvement store for a roll of batting, the U.S. Department of Energy’s Building America program recommends having an energy audit done on your whole home first. This checkup should be performed by a contractor certified in building science. After thoroughly testing the energy performance of your entire house, the contractor will provide a prioritized list of recommendations to improve efficiency. With this list in hand, you can confidently begin your project.
Where to Find a Certified Energy Auditor
There are several resources you can use to find contractors qualified to perform a whole-house energy audit. The U.S. Department of Energy and the Environmental Protection Agency jointly sponsor the national Home Performance with ENERGY STAR program. To find a contractor certified by this program, visit www.energystar.gov. Click “Home Performance with ENERGY STAR,” then “locations,” and select your state. You can also find qualified contractors in your area through the Building Performance Institute at www.bpi.org, and the Residential Energy Services Network at www.resnet.us.
Ready – Set – Insulate!
Now that you’ve been given the go-ahead, it’s time to choose your insulating material. A quick google search for “basement ceiling insulation” reveals as many opinions on the best type of insulation for the project as there are aisles in Home Depot. (More, actually, but you get my drift.) One of the most popular is fiberglass batting. It’s the least expensive, and – unlike rigid insulation types like foam board – it’s flexible, allowing it to be placed around fixtures. This is key, as basement ceilings are often home to various pipes and ducts. Sprayed foam is also good for insulating around these types of irregularities, but it’s more expensive and harder to remove when you need access to fixtures. In any case, you have many choices.
Blanket (or Batt and Roll)
Blanket insulation may be made of fiberglass, mineral wool, other natural fibers, or plastic fibers. It generally comes in rolls, like fabric, and is usually made in widths that match standard stud and joist spacing. This type of insulation is recommended for unfinished ceilings, and has the advantages of being easy to install and flexible. Blanket insulation is generally the least expensive type, though its price varies based on the material from which it’s made. For example, mineral wool is more expensive than fiberglass.
Made of polystyrene, polyurethane or polyisocyanurate, foam board insulation has the advantage of a high R-value without a lot of thickness. It also has a couple of disadvantages. It’s highly combustible, and must therefore be covered by at least a half inch of drywall (gypsum covering) as a precaution in case of fire. Foam board, if not installed correctly, can also cause electrical problems by blocking thermal short circuits.
Loose-Fill and Blown-In
This material, which can be made of cellulose, mineral wool, or fiberglass, is ideal for hard to reach places. It must be installed using special equipment, so doing it yourself is a challenge. At the same time, it is especially well-suited to areas where existing fixtures create obstructions and irregularities, which is often the case with basement ceilings.
This shiny type of insulation can be made of foil-coated kraft paper, plastic film, polyethylene bubbles, or cardboard. It can be used on unfinished ceilings, and the non-bubble types are made to match the standard space between joists and studs. The bubble type is designed to be used in odd-sized or irregularly shaped spaces. One advantages of reflective insulation is that it is easy to install yourself. However, it is not recommended for use in cold climates, and may cause moisture problems. Reflective insulation is most commonly used in attics rather than basements.
Sprayed Foam and Foamed-in-Place
This type of foam insulation, which may be made of plastic resin or polyurethane, is ideal for adding insulation to finished areas and around irregularities and obstructions. Small quantities can be sprayed, while larger amounts must be pressure-sprayed.
Before you make your final selection, be sure it has the right R-value. An insulation material’s R-value is a measure of its heat-blocking power, and generally relates to its thickness (the higher the R-value, the thicker the material). R-values also depend on material type and density, so be sure to look for a number rather than just eyeballing it. For unfinished basement ceilings in North America, an R-value of 12 or higher is recommended.
In addition to the insulation itself, you may need to install a fire-rated covering and/or a vapor barrier. Fire-rated coverings are required for insulation types that release toxic gas when ignited. A vapor barrier, or vapor-retardant covering, protects your insulation from the moisture for which basements are so well-known. This, in turn, protects your ceiling and joists from mold, mildew and rot. A vapor barrier is usually a membrane or coating applied to the insulation. While rigid foam insulation tends to be fairly vapor-resistant on its own, blanket insulation usually needs an added vapor barrier.
Finally, if you plan to install your basement ceiling insulation yourself, we recommend hiring a professional to inspect the space before you begin – to make sure you’re not overlooking any potential safety hazards. Examples of things a professional should look for include knob-and-tube wiring, which can overheat when covered by insulation, and sufficient ventilation. Also be sure all ducts and pipes in the basement are properly insulated to protect against heat loss as well as freezing (and potentially bursting). Remember: the more successful your basement ceiling insulation is at retaining heat within the floors above your basement, the colder your basement is going to be!
The Other Reason to Insulate Your Basement Ceiling
While insulating your basement ceiling is not recommended if you’re going to be living in your basement, practicing with your band or watching action movies with the volume turned up is a whole other story. Besides lowering energy bills and keeping ground-level floors warm, a prime reason people insulate their basement ceilings is to soundproof them.
For soundproofing, rather than R-value, you will want to look at insulation materials’ STC (sound transmission class) ratings. Forty (40) or above will give you the best results. A layer of fiberglass batting followed by two layers of 5/8-inch drywall does a great job. There’s no need to spend the extra money for mineral wool – fiberglass works just fine. Use Green Glue between the drywall layers to create a small space. This is a job you can do yourself, if you have or can rent a drywall lift, and have sufficient muscle, or a helper, to hoist the drywall sheets onto the lift.