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Install Insulation

Make your home warmer in winter, cooler in summer while saving money with proper insulation. We'll show you how to insulate several areas around the home: walls, attics, basements and crawlspaces.

How To Install Insulation.

Tools & Materials

All Applications

Walls

Attic

  • Rented Insulation Blowing Machine (Blown-In Insulation)

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Before Installing Insulation

Seal Gaps and Cracks Before Adding Insulation.

We'll give you general instructions for insulating several areas of your home, but always follow the insulation manufacturer's instructions. Here are some things you need to do before you begin:

  1. Check your local building code for R-value recommendations and any vapor barrier requirements that apply to your area.
  2. Seal gaps that allow unconditioned air into the space you're insulating. Pay attention to areas where plumbing, ductwork or wiring enters the space. See Do-It-Yourself Foam Insulation and How to Caulk. In crawlspaces and basements, make sure there are no cracks in the foundation.
  3. Measure between joists (if insulating a floor or attic) or studs (if insulating unfinished walls) to find the correct width of insulation. If you're insulating framed walls, make sure the insulation is the correct thickness for your wall studs.
  4. Use our Roll Insulation Calculator to estimate how much roll or batt insulation you need.
Good to Know

Insulation is available in faced (with a vapor retarder) and unfaced rolls and pre-cut batts. Blown-in and foam board insulation is also available. The R-value of the product indicates how well it insulates.  See our Insulation Buying Guide for more information on determining the type and R-value you need for different applications.

Caution

The paper side of faced insulation is flammable and must not be left exposed. Cover it with a finishing material, such as drywall. Watch our video How to Hang Drywall for step-by-step instructions.

Insulating Your Home

Insulating Stud Walls

Step 1

Installing Batt Insulation in a Wall.

Gently tuck the insulation into the cavities between wall studs. Pay special attention to the corners and edges. The insulation should fit snugly in the cavity and leave no gaps.

Good to Know

Make sure the vapor retarder on faced insulation is facing the conditioned, interior space unless building codes specify otherwise.

Step 2

Cut the insulation to fit as necessary. Leave the pieces about an inch larger than the cavity to fill the space completely.

Step 3

Staple the flanges of faced insulation to the interior faces of wall studs or the stud edges. When stapling, avoid stretching the facing too tightly and over-compressing the insulation or creating gaps or puckers.

If installing unfaced insulation in unfinished walls — such as in an interior wall — allow friction to hold the insulation in place.

Good to Know

Stapling on the inside of studs is preferred by many drywallers because it leaves the edges of the framing members easier to locate. However, your local building codes may require you to overlap the flanges and staple them to the edges of the framing members.

Step 4

Use a screwdriver or putty knife to push small pieces of unfaced insulation into gaps, such as those around windows and doors. To avoid bowing window or door frames, don't overfill around these areas with insulation or expanding foam.

Insulating an Attic with Blown-In Insulation

Step 1

Plan ahead. This is a two-person job; you will need one person in the attic and one feeding the blowing machine from outside. The best time to install insulation is in the early morning hours before the attic heats up.

Good to Know

Blown-in insulation is specified by R-value, but is not labeled like rolls and batts. Use our Blown-In Insulation R-Value calculator to estimate the R-value of the insulation by depth.

Step 2

Install Rafter Vents to Prevent Blocking Airflow from Soffit Vents.

Use plywood to make a temporary walkway by resting a sheet across the ceiling joists. You may also need temporary lighting. Install the rafter vents between ceiling joists and adjacent to the soffit vents. The rafter vents prevent insulation from blocking airflow through the soffit vents.

Step 3

Use the metal flashing to create barriers that keeps insulation at least 3 inches away from heat-generating objects such as metal chimneys and heater flues and fixtures such as recessed lights and exhaust fans that are not designed for direct contact with insulation.

Step 4

Mark the desired depth of insulation in several locations so you know when you have installed enough.

Step 5

Fill the Space Between Ceiling Joists with Blown-In Insulation.

Set up the blowing machine according to the manufacturer's instructions. Blow the insulation into the attic beginning at the far wall and working towards the center. Hold the hose parallel to the floor. Always blow in the direction the joists run.

Good to Know

Keep the hose close to the floor where insulation must go under obstructions like cross bracing and wiring. Insulation must be blown on both sides of these kinds of obstructions. If an obstruction has caused a low spot to occur, fill in the area.

Step 6

Blow In Insulation Until You Reach the Correct Depth.

Continue blowing insulation until the attic floor is covered to the correct depth. Where possible, back away to avoid packing the insulation. Avoid working yourself into a corner. Be sure to get insulation to the top of the walls and low places. Don't cover the soffit vents.

Good to Know

Add weatherstripping to your attic access hatch or stairs if needed. If the attic access isn't insulated, you can add batts, foam board or an insulated cover.

Insulating an Attic with Roll or Batt Insulation

Step 1

Plan ahead. The best time to install insulation is in the early morning hours before the attic heats up.

Step 2

Install Rafter Vents to Prevent Blocking Airflow from Soffit Vents.

Use plywood to make a temporary walkway by resting a sheet across the ceiling joists. You may also need temporary lighting. Install the rafter vents between ceiling joists and adjacent to the soffit vents. The rafter vents prevent insulation from blocking airflow through the soffit vents.

Step 3

Add More Insulation to Insulated Attics to Improve Energy Efficiency.

Unroll the insulation. Cut it to length at the end of each run. If you need to begin a new roll, butt the end tightly against the end of the previous roll. Don't work yourself into a corner.

In uninsulated attics, place insulation into the cavities between ceiling joists. The insulation should fit snugly in the cavity and leave no gaps. Make sure the vapor retarder on faced insulation is facing the conditioned, interior space, unless building codes specify otherwise. Codes in some areas may not call for an interior vapor retarder.

In an attic already insulated with roll or batt insulation, you can add additional insulation to improve energy efficiency. Use an unfaced product to prevent trapping moisture within the insulation. If the cavities between joists are already filled, run insulation perpendicular to the ceiling joists to the desired thickness. If the existing insulation doesn't reach the top of the ceiling joists, add new insulation to fill the cavities and run additional insulation perpendicular to the joists to the desired thickness.

Caution

Keep insulation at least three inches from heat-generating objects such as metal chimneys and heater flues and fixtures such as recessed lights and exhaust fans not designed for direct contact with insulation. You may want to install metal barriers to maintain the 3-inch distance.

Step 4

Run the insulation to cover the tops of the exterior walls, but don't cover the soffit vents.

Step 5

Tuck small pieces of unfaced insulation into any small spaces and gaps as needed.

Good to Know

Add weatherstripping to your attic access hatch or stairs if needed. If the attic access isn't insulated, you can add batts, foam board or an insulated cover.

Insulating an Unconditioned / Vented Crawlspace

Step 1

Spread plastic sheeting over the crawl space floor to block ground moisture from entering the crawlspace. Check the insulation manufacturer's instructions for the necessary thickness of plastic. Overlap seams by about 12 inches and run the plastic up the walls at least 6 inches. Tape the plastic to the walls and seal seams with tape or hold them in place with lumber or rocks.

Good to Know

An unconditioned or vented crawlspace has ventilation to allow outside air to circulate though the space.

Step 2

Cut and install small pieces of insulation to fit against the header / band joists (those at the end of the floor joists) above the walls of the foundation. They should fit snugly between the ends of the floor joists.

Good to Know

Check the manufacturer's instructions on whether to use faced or unfaced insulation in an unconditioned / vented crawlspace.

Step 3

Install Installation Between Floor Joists.

Start at one edge of the crawl space and install insulation between the floor joists. If using faced insulation, keep the paper vapor retarder facing up and against the subfloor. The insulation should fit snugly against the subfloor and between the joists. Make sure each run contacts the insulation you installed at the header / band joists.

Step 4

Cut insulation as needed to fit any narrow spaces between floor joists.

Good to Know

You can use a broom handle to stuff the insulation into hard-to-reach places.

Step 5

Secure the insulation against the subfloor with wire supports. Space the supports at least 6 inches from each end of the insulation and 12 to 16 inches apart. The supports should bow up gently against the insulation without compressing it.

Insulating a Conditioned / Unvented Crawlspace

Step 1

Spread plastic sheeting over the crawl space floor to block ground moisture from entering the crawlspace. Check the insulation manufacturer's instructions for the necessary thickness of plastic. Overlap seams by about 12 inches and run the plastic up the walls at least 6 inches. Tape the plastic to the walls and seal seams with tape or hold them in place with lumber.

Good to Know

A conditioned or unvented crawlspace is sealed against the outside air and heated and cooled much like a room in your home.

Step 2

Cut and install small pieces of insulation to fit against the header / band joists (those at the end of the floor joists) above the walls of the foundation. They should fit snugly between the ends of the floor joists.

Good to Know

Check the manufacturer's instructions on whether to use faced or unfaced insulation in a conditioned / unvented crawlspace.

Step 3

Cut insulation to cover the walls at the end of the floor joists. The insulation should be long enough to hang from the sill above the wall — butting against the insulation you installed in Step 2 above — and extend two feet onto the crawlspace floor.

Step 4

Use furring strips to hold the insulation against the edge of the sill and secure with nails.

Step 5

Cut insulation to run from the top of the stringer joists (the joists that run parallel to the floor joists) and extend two feet onto the floor.

Step 6

Butt the top end of the insulation against the subfloor and nail or staple it to the stringer joists.

Good to Know

The insulation should lay on top of the plastic film on the crawlspace floor.

Step 7

Place 2 x 4s to anchor the insulation on the floor as tightly as possible against the walls.

Insulating Basement Walls

Step 1

In a basement with framed walls, see Insulating Stud Walls above. Alternatively, you can use foam boards rather than insulation rolls or batts.

In a basement with unframed walls, install faced insulation in horizontal runs starting at the sill above the wall. Position a furring strip over the flange of the top run and drive nails through the furring strip and flange, into the sill.

Good to Know

Some manufacturers don't recommend using insulation with a vapor retarder on walls that are below grade. Check the instructions and your local code for guidance.

Step 2

Tightly butt the next row of insulation against the first, overlapping the flanges of the facing. Secure the second run of insulation to the first by stapling them together through the flanges. Alternatively, you can attach furring strips along the walls and staple the flanges of the insulation to the furring strips.

Step 3

Continue adding insulation down to the floor. Apply 3-inch vinyl patch tape over the seams and stapled edges.

Step 4

Cut and install small pieces of insulation to fit snugly against the header / band joists (those at the end of the floor joists).

Working with Insulation

  • Wear long sleeves and long pants. Check the insulation instructions for recommended safety gear such as eye protection, gloves and dust masks. If you're working in a crawlspace or attic, you may want to wear kneepads for comfort.
  • Open insulation packages carefully and only as you need them. Insulation expands quickly when you open the packaging.
  • Don't double insulation over or compress it. Folding and compressing the material changes the R-value.
  • Once you've filled a space with roll or batt insulation, fluff it to its full expansion by pulling it forward to fill the cavity.
  • Cut insulation on the unfaced side, against a safe backstop, such as an unfinished floor or other smooth, flat surface. Don't cut near wiring.
  • You may need to split or cut the insulation to fit carefully around obstacles such as bracing, ducts, electrical boxes, wiring and pipes.
  • If you live in an area where frozen pipes are a concern, make sure the insulation protects the pipes from cold air.
  • Where necessary, make sure duct work is insulated to help your heating and cooling system operate more efficiently.