Understanding When to Use Different Types of Insulation

by DoItYourself Staff

Loose-Fill Insulation

Comes compacted in bags and is poured or blown into walls and between joists of the attic floor.

Good for retrofitting insulation into previously uninsulated homes.

Each bag is labeled according to federal specifications for both mineral wool and cellulose. Left column lists the R-value, second column tells how many bags are needed to cover 1,000 square feet of attic floor area, the third column gives the minimum thickness after completing the job.

Some manufacturers have two columns on thickness for loose-fill and cellulose insulation. The second of these is labeled “settled density”. This is important since cellulose settles quickly.

Types include fiberglass rock wool and cellulose. Cellulose is made from waste paper that has been treated to be fire retardant. It is also less likely to cause skin irritation.

Roll Insulation

Comes in continuous rolls that vary in width and thickness.

Usually installed between open ceiling joists and wall studs.

Has a vapor barrier that should be installed with the vapor barrier toward the interior or heated area. Mend torn vapor barriers with tape.

Available in R-values of R-11, R-13, R-19 and R-25. Thicknesses range from 3-1/2” to 8”.

Encapsulated Insulation

Batt and roll insulation encapsulated for easier handling.

Encapsulation enables the insulation to breathe and prevents condensation build-up.

Easier to handle by reducing dust and other irritants associated with insulation installation.

The non-woven type tends to stay in place better than plastic-wrap insulation. This product must meet all building code requirements for flame spread resistance, as it is flammable.

Rigid Insulation

Can be used on the interior or exterior of the house, or on basement walls.

Usually comes in board form in a variety of sizes ranging from 8” squares to 4’ x 12’ sheets.

Some types are made of fiberboard and are popular because of their durability and low cost. Fiberboard repels water, while the asphalt coating eliminates the need for building paper.

Another type is made of extruded polystyrene. It is very resistant to moisture and is most highly recommended for below-ground use.

Molded polystyrene board is another type that dissipates water well.

Another type is polyisocyanurate sheathing that is available with aluminum foil or glass fiber mat facers. This type has the highest R-value per inch of thickness of all insulation products.

Foam Insulation

Comes in a liquid spray form that quickly foams and hardens.

May have a higher insulating value than blown-in materials, but is more expensive and still subject to shrinking.

For use only on closed, properly vented exterior wall cavities. It should be sealed from exposure to the interior with vapor- and fume-resistant paints.

Also suited for sealing cracks around windows, doors and constructions seams.

Best for professional installation

Foam Sealant

Installs similar to foam insulation, but comes in an aerosol can and is best for do-it-yourself use.

Best used for permanently sealing irregular gaps around the home, such as plumbing feed-thrus, electrical outlets, vents, etc.

After curing, it can be trimmed, sanded and painted.

When installing, only fill the area about 33 percent and the expanding foam will fill and seal the rest of the area.

Formulations include triple-expanding for general-purpose sealing and insulating; minimal-expanding for windows and door frames; and fast drying for multi-step projects such as filling a crack before painting.

Wear gloves and eye protection when applying.

Remove wet foam with acetone or acetone-based nail polish remover. Cured foam is difficult to remove from skin and clothes

Reflective Foil Insulation

One type is made of foil and poly to trap air between the sheets of foil, generally using bubble pack.

A second type expands when installed between stud spaces. The resistance to heat flow depends on the heat flow direction. This type of insulation is most effective in reducing downward heat flow.

Comes in long rolls of various widths.

May be used in conjunction with many different building materials and cut to fit any shape.

Typically installed between roof rafters, floor joists or wall studs.

When a single reflective surface is used alone and faces an open space such as an attic, then it is called a radiant barrier.

Pipe Insulation

For insulating water pipes from freezing in the winter. It also helps control heat loss when pipes carry hot water and controls condensation and dripping.

Available in preformed insulating tubes that fit over the pipe.

Another type comes in batt form, which can be wrapped around the pipe.

Adhesive-Backed Foam Tape

Installed by pressing into position and sticking permanently.

Requires no nails or tools.

One type, pressure-sensitive sponge rubber tape, is suited for larger problem areas.

Another type, pressure-sensitive vinyl foam or felt, is for average sealing.

Closed-cell PVC foam compresses to fill irregular gaps and can be used outdoors.

Open-cell foam is for inside use only.

High-density foam is extremely durable and long lasting.

V-Type Weather Strip

Once the door is closed, the open ends of the V shape close together, with one end of the V touching the door and the other adhered to the door.

Forms an airtight seal.

Spring-metal tension strips are more difficult to install than adhesive-backed tension strips made of vinyl, but are the best permanent type.

Caulking Cord

Temporarily fills large gaps around windows.

Consists of soft, rope-like strands of weather strip with the consistency of modeling clay.

Easily applied by hand and remains pliable so it can be removed when the weather warms.

Paintable and will not harden or dry out.

Vinyl Gasket Weather Strip

Weather stripping that cushions as it seals.

Can be used in places with warping or irregularities.

Door Jamb Weather Strip

Used to seal the sides and top of a door to shut out drafts and insects.

Available in a variety of forms, including roll-formed and extruded aluminum with vinyl bulbs or flaps.

Door Sweep

Seals the bottom of an exterior door, preventing drafts, water, noise, light and insects.

Usually made of aluminum extrusions with vinyl flaps.

Screws into the door.

Some types lift automatically when the door is raised.

Another type is an aluminum extrusion with a rain-drip flange to prevent the flow of water off a door from collecting on a threshold and flowing under a door.

Another type is an adhesive-backed plastic door sweep.