Basement Insulation 1 - Introduction

Basement Insulation and Air Duct

Heat naturally flows from a warmer area to a cooler one. It does this in only three ways: conduction, where heat is transferred directly from mass to mass; convection, the movement of heated air from one space to another (hot air rises, heavier cool air sinks); and radiation, which simply means that any warm body gives off heat toward a cooler one. The function of insulation is to minimize the radiation and convection transfer of heat with a minimum of solid conduction so that homes stay warm in cool weather and cool in warm weather.

In this section we review the merits and uses of various types of well-known insulation and inform you on how best to evaluate R-values. R stands for 'resistance to heat flow.' The greater the R-value, the greater the insulating power. R-value requirements depend on factors such as local climate and the surface you are insulating (walls, ceiling, floor, etc.) and will be regulated by your local building code.

Contact the office of your city or county building inspector for the requirements in your area. Each region of the country has different requirements for adequate amounts of insulation.

In many areas (see our Energy Efficient Homes), local utility companies will offer helpful suggestions on how to reduce your energy bills. Many will arrange to have an expert come to your home to point out areas that need to be insulated or weatherized. Often there is no charge for this service, and it may even lead to low or no-interest loan programs for which you may be eligible. State or federal tax credits may also apply.


Safe-use practices are important when you work with any type of insulation.

Dust masks and goggles are necessary for work with all types of insulation or when sawing wood.

Fully cover your body with long sleeves, a hood, long pants, and gloves. Insulating materials are skin irritants.

Always use the correct tool for the job.

Be sure power tools are properly grounded.

Watch power cord placement so that it does not interfere with the tool's operation.

A hard hat should be worn, since roofing nails may be sticking through the sheathing.

If you are not allergic to tetanus shots, be sure yours is current. There are usually exposed, rusty nails in an old attic.

Keep the insulation clear (3-inches) from objects that transfer heat to reduce fire hazards and install sheet metal baffles around recessed light fixtures, chimneys, and flues.

In older homes with possible frayed wires, do not allow the aluminum vapor barrier of batt insulation to contact the wire since it could short circuit

Working in attics or other hot areas can cause loss of body salt by excessive sweating. Consider taking salt tablets.

When working outside on a roof, wear shoes or boots with rubber soles, stay clear of power lines, secure extension ladders with safety hooks that clamp over the ridge, and delay your work until the roof is free from the dampness of rain, frost, snow or dew.

When working high on the outside of the house, rent scaffolding to provide a balanced, level working surface.

Do not step through the attic floor joists onto the ceiling of the room below. It will give way.

Some types of insulation are flammable. Check with your local building department and fire department for special application precautions or restrictions.

Useful Terms


A pliable material, usually forced into a gap or crack with a gun or pressurized can, hardens into an effective seal against air and moisture infiltration.


Blown-in or loose, consists of rock wool, glass fiber, vermiculite, and/or perlite. Use it for floors, walls, and hard-to-reach places. This type of insulation is poured between joists or blown-in with special equipment. It is best suited for use in irregular-shaped areas and is the best option for blowing into existing finished walls.


Blankets or batts are widely used as insulation for walls, floors, ceilings, roofs, and attics. Fitted and stapled easily between studs, joists, and beams, I feel it is best suited for the do-it-yourselfer.


A waffle-like strip of plastic designed to allow air circulation to carry away moisture that could build up under insulation.


Extruded polystyrene, isocyanurate board, and fiberglass board. These rigid panels are used on unfinished walls, in new construction, on basement and masonry walls, or exterior surfaces. The panels are glued or cut to friction fit between studs, joists, or furring strips and must be covered with drywall or paneling for fire safety. They offer a high insulating value for relatively thin material but are highly flammable, and some chemically-based sprays or foams may discharge poisonous fumes over a period of time. Be sure to use a closed-cell, waterproof rigid panel in exterior applications or in high moisture areas.


Strips of wood used to level out a surface prior to finishing.


Thin wedges of wood used to bring furring strips level with each other when used on an uneven wall.

Silicate Compound

Made of glass and sand. It does not burn, release toxic fumes nor attract vermin. It comes in lightweight easy-to-handle bags and should be used in the same manner as loose-fill or cellulose.

Vapor Barrier

The most common is a 6-ml. sheet of plastic attached over the insulation to eliminate moisture infiltration and deterioration of insulation.

Working in your attic is hot and tiring. Try to work early in the morning before it gets too hot. Carry a spray container of cold water to spray on yourself and your fogged-up goggles.