Figuring Out What You Need

The U.S. Department of Energy (DOE) has a list of recommended levels of insulation in ceilings, walls, floors, and foundations, broken down by zip code (see Resources) for more information. In general, you should put at least R-30 in your attic even in milder climates, and up to R-49 in the coldest parts of the United States. Floor insulation may not be necessary at all in the warmer states, but in most parts of the country R-19 is recommended. Wall insulation is recommended in all climates, but the amount can be limited by the space in the wall cavity. Using fiberglass or cellulose in a 2 x 4 wall will usually give you from R-11 to R-15. However, you can get R-19 to R-21 in a 2 x 6 wall cavity, and even more if you use rigid insulation beneath the siding.

It is almost always easier and more effective to install more insulation during initial construction than to add it later. Still, you can add insulation to most places in existing homes. Attics are typically the easiest to get to, but insulation can be blown into empty wall cavities, attached under floors, and added to basement or crawlspace walls. On the other hand, retrofit foundation insulation may be prohibitively expensive, and adding more insulation to partially insulated walls is usually difficult and impractical.

How Much Do You Have Now?
To decide how much insulation to add to your home, you need to know how much is already there (see Table 1). If you don't have an energy auditor inspect your home, you should look for insulation in several places.

Table 1: Identifying Old Insulation
Material	Description	R-Value per Inch
Fiberglass batts	Pink, yellow, or white, blanket-like	3.2
Loose-fill fiberglass	Pink, yellow, or white loose fibrous material	2.2
Loose-fill rockwool	Denser than fiberglass, "wooly"	2.9
Loose-fill cellulose	Shredded newspaper, gray "dusty"	3.5
Vermiculite	Gray or brown granules	2.2
Perlite	White or yellow granules	2.7
Misc. wood products	Sawdust, redwood bark, balsa wood, straw	1
Urea formaldehyde foam	Whitish gray or yellow, very britte foam	4
Asbesto	may be mixed with other materials - difficult to identify	1
Urea formaldehyde foam is no longer sold due to concerns about formaldehyde off-gassing. If you suspect you have asbestos, consult a hazardous material specialist before disturbing the insulation.

Attic
First, check the attic; take a few measurements with a ruler in different areas (away from the access hatch, where insulation is more likely to have been disturbed or compacted) and average them.

Garage and Crawlspaces
In unheated garages and basements and above crawlspaces, the structural framing (the joists of the floor above, or the wall framing studs) is often exposed, making it easy to examine the insulation. You may find batts, blankets, or rigid insulation there. An unvented crawlspace may also have insulation on the perimeter wall. If your house is relatively new, it may have insulation outside the basement or foundation wall. However, this insulation will not be visible because it will be covered by a protective layer of plastic, fiberglass, metal flashing, or rigid protection board. The builder or the original homeowner may be able to tell you if such exterior insulation was used.

Exterior Walls
Inspect exterior walls by removing the cover plate from an electrical outlet or switch on the inside of the wall, and shine a flashlight around the sides of the box. Often you can catch a glimpse of insulation in the gaps around the outlet box. A plastic crochet hook (don't use metal unless you first turn off the power to the outlet) is useful for pulling out a bit of the material for identification. Check outlets on a few different walls on each floor, and make a separate check in any parts of the house that were built at a different time. Rigid insulation is difficult to identify in finished walls. One way to look for it is to remove and then replace a small section of the exterior siding and sheathing.

Selecting a Type
The type of insulation you use will depend partly on the spaces that youplan to insulate. For example, since you cannot conveniently blowinsulation into an open overhead space, batts, blankets, or spray products are used between the oists of an unfinished basement ceiling. The only way to fill closed cavities in finished walls (without tearing them open) is with blown-in insulation. Table 2 provides a summary of the appropriate applications for the various types of insulation. See Comparing Insulation Materials for other considerations in choosing which type to use.

Table 2: Insulation Comparison Chart
Insulation Type	R-Value per inch	Density in lb/ft³	Where Applicable	Advantages
Loose-fill     Fiberglass         (dense pack)     Rock wool     Cellulose         (dense pack)	2.2-2.9 3.4-4.2 2.2-2.9 3.1-3.7 3.4-3.6	0.5-1 1.6-3 1.7 1.5-2 3-4	Anywhere that frame is covered on both sides, such as finished walls or cathedral ceilings. Unfinished attic floors and hard-to-reach places.	The only insulation that can be used in closed cavities. Easy to use for irregularly shaped areas and around obstructions. Dense-pack provides air sealing and insulation.
Batts    Fiberglass    Cotton	2.9-4.2 3-3.7		All unfinished walls, floors, and attics. Fitted between frame studs, joists, and beams	Do-it-yourself Suited for standard stud and joist spacing, if there are few obstructions
Sprayed Insulation    Polyurethane foam    Icynene foam     Wet-spray cellulose    Spray-in fiberglass	5.6-6.2 3.6-4.3 2.9-3.4 3.7-3.8		Unfinished walls, attics, and floors	Provides air sealing as well as insulation. Can provide complete coverage around obstructions.
Foam board    Expanded polystyrene    Extruded polystyrene    Polyisocyanurate    Polyurethane    Phenolic (closed cell)    Phenolic (open cell)	3.9-4.2 5 5.6-7 5.6-7 8.2 4.4		Basement masonry walls Exterior walls under construction Exterior walls when adding siding	High insulating value for relatively little thickness Covers wall framing, insulating studs as well as cavities.
Sources: DOE Insulation Fact Sheet, ASHRAE Handbook of Fundamentals; EREC, Loose-Fill Insulation, 1995; David Yarbrough, Tennessee Technical University

• Insulation 101: How It Works

• Type of Insulation

• Figuring Out What You Need

• Installing Insulation

• Doing it Yourself