Do You Need to Add More Insulation to Your House? How to Prepare for the Cold

How do you decide whether your home needs more insulation? The answer can be as obvious as the drafts you feel around baseboards, cabinets, windows and doors, or the outside cracks and gaps around the chimney or at places where pipes or wires enter the house.

One quick check you can make in cold weather is to hold your hand against several spots on an interior wall and then compare its temperature with that of an exterior wall. If your home is adequately insulated, the exterior wall should feel only slightly cooler.

Manufacturers measure the ability of insulation to resist the flow of heat in terms of its ”R” (resistance) value. The higher the R value, the better a particular insulating material slows winter heat loss and summer heat gain.

Under federal law, every package of home insulation must display its R-value rating, and all stores that sell insulation are required to have on hand the manufacturer’s fact sheet, which identifies the type of insulation, its R value and the minimum area that the amount of insulation you buy will cover while still achieving the R value.

What types of insulation are available?

Insulation is made from a variety of materials and is sold in several forms:

Batts and blankets are the familiar fluffy strips that are fitted between rafters and joists. The only difference between them is that batts come in pre-cut lengths, and blankets come in continuous rolls. Both are lightweight and easy to install. However, they must be cut carefully to fit around obstructions.

Loose fill comes in bags and is used mainly for attics and in finished walls. Depending on the type of fill, it may be installed by a do-it-yourselfer or may have to be blown in by a professional. While relatively easy to install, it can settle and lose its R value if not properly installed.

Rigid insulation comes in slabs of boardstock in a variety of materials. It is most useful in new construction.

Insulating foam is pumped into a cavity or space, where it solidifies. It is most commonly used in the exterior walls of existing buildings and must be installed by a professional.

Reflective foil consists of one or more sheets of aluminum foil. While foil is the most effective insulator against radiant heat, its effectiveness can be greatly reduced by a puncture.

What is a vapor barrier?

You can buy batts, blankets and some rigid insulation with a vapor barrier on one side. These are foil coverings that protect the material from condensation, which can lower its R value.

If you are installing insulation with a vapor barrier, make sure the barrier is on the side of the insulation that will be heated.

When adding new insulation over an existing layer that has a vapor barrier, either use unfaced material or, if that’s not available, remove or thoroughly slash the vapor barrier of the new insulation.

How do I choose the kind of insulation to use?

Choosing the proper form of insulation involves an evaluation of the area to be insulated, the local climate, the R value needed and your budget.

One of your main decisions is whether to install it yourself or hire a professional.

Get at least three estimates, and compare more than prices. Each estimate should include the cost of materials and labor, the R value of insulation to be installed in each part of the house, types of material to be used, areas to be covered, thickness of insulation and, in the case of loose fill, the number of bags to be used.

What if I decide to do it myself?

First, determine the R value you will need. This varies according to the part of the house you’re insulating.

Decide what type of insulation to install, after considering how easy each type is to install and whether instructions are available.

Measure the area you’re going to insulate. Check the chart on insulation packages to figure out how much insulation you will need to get the recommended R value.

In shopping for the best value, you may use this formula: The price of the package, divided by the square feet of insulation needed for the R value you select, divided by the R-value number you select, equals the cost of one unit of R value.

All the numbers that you need to plug into this formula are either on the insulation package or can be provided by the retailer. Comparing the cost of one unit or R value for each product you are considering helps you determine which gives you the R value you want at the lowest cost.