Cheap Ways to Insulate a Building

Insulation is a low-cost way to save money and make your home more comfortable. Whether you want to keep out the frigid winds of winter or the searing sun of summer, insulation will protect you and your house from the elements. We don’t usually see insulation, but you would know if you were in a building without it. Wallboard and even plaster don’t keep out wind and weather nearly as well as insulation. But when you insulate your house, garage, outbuilding or other structure, you need to know what your choices are. Insulating your attic is the best way to start. It helps keep your heating costs down in winter and your cooling costs down in summer.

R-value refers to thermal resistance. The U.S. Department of Energy recommends unfinished attics have an R-value of 30 in hot climates, 38 in temperate climates and 49 in cold climates. The department's website has a map showing the R-values recommended in every part of the U.S. Before you buy insulation, you should know what the R-value of your home or building should be.

Spray foam insulation seals leaks and gaps inside existing walls. If your house has lots of air leaks, spraying liquid polyurethane into those gaps can be a cheap, quick and easy way to rid your house of air pockets. After the application, the foam hardens into a solid and can be painted to match surrounding walls.

You can use half-pound open cell foam or a more dense foam called two-pound closed cell foam. The two-pound will provide better insulation, but you don’t always need this much insulation.

Closed-cell spray foam has the highest R-value of any insulation, up to R-6 per inch. It takes up less space than fiberglass or blown-in insulation. It can also save up to $500 a year in energy costs.

Expect to spend $300-to-$600 for a DIY foam insulation kit to cover 200-square-feet. Professional installation is 44 cents-to-$1.50 per-board-foot.

Foam boards are rigid panels that can be used to insulate any part of the home, from the roof to the foundation. These boards are usually made of polystyrene or polyurethane and are sheathed by wood or steel studs.

Rigid foam insulation also has a high R-value. It is sold in sheets, usually 4-by-8-foot sheets, from one-half inch-to-2-inches thick. You can special-order thicker sheets. These sheets are lighter than plywood. Rigid foam insulation will not shift or blow out of place, and it’s water-and-pest-resistant.

Average rigid foam board insulation cost is from $3.95-to-$7.20 per-square-foot, professionally installed.

Cellulose, or blown-in, insulation is typically recycled paper and cardboard. It also has a high insulation value. It is blown into any space where insulation is needed. It should be loosely packed, while still filling all open spaces, to about 10 inches to achieve R-35 insulation. This is not a difficult DIY job and costs about $500 for the average 1,500-square-foot home.

One advantage of cellulose insulation is that it can be installed over existing insulation for additional protection from the elements.

Fiberglass batts are typically the cheapest insulation, but a loose corner or tear can diminish the insulation quality. Batting is packaged in rolls of standard thicknesses, usually 16 inches or 24 inches, and will fit between joists or studs which is great for new construction in attics or other areas with few obstructions. The cost for fiberglass insulation is about $145- to-$200 for a 500-square-foot area for DIY. Add about $150-to-$300 for labor if you hire it out.

Radiant barrier, or reflective insulation, is an economical form of insulation most effective in warm climates. Radiant barriers reflect radiant heat from your roof rather than absorb it. A highly reflective aluminum foil is applied to one or both sides of a number of substrate materials such as kraft paper, plastic films, cardboard, oriented strand board or air infiltration barrier material and can be combined with other insulation. A DIY project will cost $175-to-$325 for a 500-square-foot area. Add $500-to-$750 for professional installation.

Old blue jeans may have a new life in insulation. But don’t just stuff your old jeans into the walls. Such textiles require fireproofing and insect-proofing. UltraTouch denim insulation comes in rolled batts, like fiberglass insulation. These can be combined for best insulation quality. Home Depot sells a roll of 16-inch-by-48-inch denim batt for $11.20. It has an R-value of 6.7 and covers 5.3 square feet. Denim is also available in a loose fill insulation. Denim insulation costs anywhere from 20-percent more to three-times the cost of other insulators for the same R-value.