Insulation: Can it last as long as your home?

Roger Diez | Improvement Center Columnist | December 19, 2014

A properly insulated home can provide comfort year-round for your family. It can also reduce your heating and cooling costs significantly. Newly-constructed homes make use of modern insulation. Older homes can often benefit from the addition of insulation. Some types of insulation lend themselves to installation in existing closed spaces, while others are more suitable for room additions or renovations that involve opening walls.

Insulation basics

The effectiveness of insulation is measured in R-Value. The higher the R-Value, the more effective the insulation in preventing heat transfer. The R-Value of insulation for your home depends on where you live. The U.S. Government has published a map of the United States with recommended R-Values for eight different climate zones. Recommended attic insulation ranges from R30 to R60 for an uninsulated attic, depending on the zone; R25 to R49 for an attic with 3-4" of existing insulation. R5 to R6 is recommended for walls and R13 to R49 for floor insulation. The Energy Star chart breaks this down by zone.

Insulation materials

The three most commonly used insulation materials are the following:

  • Fiberglass -- manufactured in rolls, batts, or blankets; also as loose fill that is sprayed into an attic
  • Cellulose -- loose fill made from recycled newspaper or other recycled paper, treated with borates to make it fire-retardant; also sprayed
  • Polyurethane foam -- open cell low-density and closed cell, sprayed or injected into spaces to be insulated

Other types include foam board and reflective insulation, but these are much less frequently used. If kept dry, undamaged, and away from UV rays, all of these insulating materials have a lifespan of 100 years or more, effectively the life of the house.

life span of insulation

Pros and cons

Each type of insulating material has its pros and cons. Here is a breakdown of these:

  • Fiberglass loose fill -- Pro: inexpensive, easy to install. Con: subject to moisture damage, low R-Value per inch (2.2 - 4.0), requires special equipment for installation
  • Fiberglass batts, rolls, or blankets -- Pro: easy to install, slightly more expensive, good R-Value per inch (3.7). Con: can only be installed in open-framed walls, hard to install in irregular spaces and subject to moisture damage.
  • Cellulose -- Pro: good R-Value per inch (3.6 - 4.0), inexpensive, easy to install. Con: requires special installation equipment, subject to moisture damage, settles over time.
  • Low density polyurethane foam -- Pro: Inexpensive, good R-Value per inch (3.6) can be injected into closed spaces. Con: requires special installation equipment, is toxic during installation requiring respirator for installer.
  • High density polyurethane foam -- Pro: Excellent R-Value per inch (5.8) can be injected into closed spaces, impervious to water damage. Con: expensive, requires respirator during installation due to toxic fumes.

Cost of insulation

The cost to insulate your home varies according to the R-Value required, material costs, and labor costs. Here are some ball-park figures:

  • Blown in fiberglass or cellulose: material cost $0.50 to $0.75 per square foot, installation $2.50 to $3.25 per square foot. Total cost $3.00 to $4.00 per square foot.
  • Fiberglass batt, roll, or blanket: material cost $0.50 to $0.70 per square foot, installation $0.40 to $0.50 per square foot. Total cost $0.90 to $1.50 per square foot
  • Polyurethane foam: material cost ranges from a low of about $0.70 per square foot for open cell foam up to $2.95 per square foot for closed cell foam. DIY kits are readily available, but add another $1.00 to $3.00 per square foot for professional installation.

Costs may be mitigated by energy-saving tax credits provided by federal, state, or local governments.

So if you are living in an older home that may have inadequate insulation, or if you are adding a room or renovating an old home, adding insulation is something you should consider regardless of how many good years your current insulation might still have.

Photo credit to Kevin Irby