Insulation 101

Why is insulation so important in a home? Proper insulation is the best way to maximize comfort and minimize energy bills. It’s not a cosmetic, beautiful update but a necessity for every home.
All insulation works the same way: by trapping tiny air pockets that slow the movement of heat out of a house during winter and into a house in summer. Its effectiveness at resisting this movement is called its R-value; the higher the value, the lower your energy bills. To achieve an R rated value insulation has to do its job and be installed correctly. If not done right, it can actually make things worse!

Mistakes that are seen in poor installations (in DIY and professionally installed)

Loose Batts

Often the problem is sloppy framing. If the studs are 16.5 inches on center and you’re using batts made for 16 inches, you’ll have a crack on each side that air can move through. In this case, it’s best to use cavity-filling foam or blown-in insulation.

Compressed Fiberglass Batts

Fiberglass insulation gets its R-value from the amount of air it traps between its fibers. If it’s jammed too tightly into a cavity, it can’t trap as much air and won’t be as effective.

Doubled Vapor Barriers in Attic

Laying a second layer of fiberglass batts in the attic is an easy way to boost R-values. However, if the new layer has a kraft-paper backing, it can trap moisture and turn the layers underneath into a soggy mess.

Types of Insulation Materials

Fiberglass batts,
This type of insulation is found in most houses in the U.S. They are inexpensive and quick to install. Like other batt-type insulation, fiberglass has a predictable R-value if not compressed but is difficult to fit around obstacles without leaving gaps. In most climates, it needs a vapor barrier. Some builders rely on batts with attached kraft-paper facing to do that job or some contractors recommend unfaced batts, covered in plastic with all the seams taped shut.

Cotton Batts– No-itch batts of recycled denim from jeans factories are treated with borates to resist fire and insects. R value of 3.7 (energy efficiency rating) Cost is average and used for attic space.
Blown Fiberglass – Fluffy bits of spun glass that are noncombustible and can’t decay. Blown in dry. Tends to settle. R-value declines by as much as 50 percent at temps below 0 degrees F. R Value of 4 least expensive. Best for attics.
Extruded Polystyrene (XPS)– Its closed-cell structure stops water and water vapor, resists compression, and holds its R-value over time. This must be protected from solvents and sunlight. Flammable and must be protected from fire with drywall or plaster. R value of 5 (energy efficiency rating) is average in cost. Best used for in ground foundation and masonry walls.
Cellulose – Made from pulverized newspapers and treated with boron to resist fire and pests. This can be blown into place dry or wet. An adhesive reduces its tendency to settle. Has a R value of 3.8 (energy efficiency rating) and Least expensive material
High-Density Polyurethane Spray Foam– The rigid, closed-cell structure makes it impermeable to water. Must be professionally applied. While not flammable, it must be protected with drywall or plaster to stop offgassing during a fire. R value of 7 (energy efficiency rating) and used for masonry basement walls.
Mineral Wool- Spun from blast-furnace slag, this inorganic insulation does not burn or support the growth of mold or mildew. Highly sound-absorbent. Blown into place wet, it’s trimmed flush with the studs after it dries; the trimmings are recycled. Used for New construction or reinsulating attics. R value of 4 9energy efficiency rating) and is very inexpensive.

Low-Density Polyurethane Spray Foam Blocks the movement of air (eliminating the need for a vapor barrier), absorbs sound like a sponge, and flexes with the seasonal movement of the framing. Must be professionally applied. Foam-low-density polyurethane spray foam is the insulation technology to beat. Consider its advantages: It forms a lock-tight bond with studs and sheathing that blocks all air movement, it flexes enough to accommodate seasonal wood movement, and it retards (but doesn’t halt) moisture passage. While spray foam is expensive, its installation costs are offset in the long run by lower heating and cooling costs.
Although not flammable, must be protected from fire with drywall or plaster. Used in new construction and attics or in crawl spaces that can be hard to install batts in. Has a R Value of 4 (energy efficiency rating) and most expensive material to install.
Foil-Faced Polyisocyanurate -Its closed-cell structure stops water vapor, and the foil-covered face acts as a radiant barrier. Not recommended for exterior, below-grade applications. Not flammable, but it must be protected with wallboard. R value of 7-8 (energy efficiency rating) and used for cathedral ceilings and finished basement walls. Runs about average for cost.

No matter what type of insulation you use proper installation is the key to have our home insulated properly. Knowing what kind of barrier is needed for your climate, how to measure and what product to use where all factor in. Do your homework, make sure you have the right materials and your installers know what they are doing!


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