Air Sealing: Materials & Methods for sealing common leaks (Part 1)

In our prior article on Air Sealing, we covered the benefits, the concerns, and how to find the leaks inside your house. In this first part of this article, we will mainly be dealing with the tools, materials and methods required to air seal your house. In the second part of this article, we will be dealing with tips & tricks on how to seal up the air leaks inside your house & some common ones outside.

Tools & Materials

The basic tools needed simply consist of a ladder, caulking gun, hammer, phillips screwdriver, regular screwdriver, 5 in 1 tool, and a sharp utility knife. The materials required vary on what you need to patch. Some of the popular materials required are; Caulking, Expanding Foam, Weather-Stripping, and Backing Material.


Caulking is applied wherever two different materials or parts of the house meet. While there are many different types available, you will want a caulking that is paintable, mildew resistant, elastic, and flexible. These are generally known as siliconized latex caulking. The cheaper “painters” caulking is occasionally acceptable for some interior areas. We do not recommend that you use pure silicone or solvent based caulking.

  • Clean the surface of paint build-up, dirt, and deteriorated caulk with a screwdriver, putty knife, or wire brush. All surfaces should be completely clean and dry before application.
  • If the joint to be caulked is larger than 3/16” of an inch, a backer will need to be installed first. (Described below)
  • Cut the tip of the caulk nozzle at a 45-degree angle. It is best to cut the hole a little smaller than you think you will need. Insert cartridge into a drip less caulking gun.
  •  While holding the caulking gun at a 45-degree angle, slowly squeeze the trigger and push or pull the gun and cartridge evenly along the joint.
    • Most professionals will state that you need to push the gun, but if you take your time you can get just as good results by pulling
    • The bead of caulk should be just wide enough to adhere to both sides of the crack or joint & completely fill it. Apply the caulk in a continuous neat bead.
    • Lightly moisten your finger or tool you are using and tool the whole joint in one pass. If you are going across tile, you should wipe it on one direction the first time & come back the other way.

Expanding Foam

Expanding foam is commonly used to fill large cracks, holes and openings around pipe and wire penetrations.  They are designed to expand and fill the openings providing a good, tight seal. There are three common types of expanding foam readily available; Regular foam, Low-Expanding foam & a Fire-Block foam. You should read and follow all the manufacturer’s directions. These materials are highly flammable when they are being installed and not something you want to get on or inside you.

  • Unless you have a foam spray nozzle – figure out all the area’s you need to hit with each type.
  • Clean the areas being filled of anything that might interfere with the foam. I will occasionally blow the holes out with compressed air. All surfaces should be completely clean and dry before application.
  • Eliminate any sources of ignition & put on all the applicable safety gear. (Safety Glasses, Gloves)
  • Shake can as directed & fill the voids as directed on the can
  • Clean up – please refer to the directions (One trick we use is after the foam has dried trim it using a hacksaw blade)


If you have leaks that are coming in around an operable door or window, you will need to correct that with the proper weather-stripping. If you have a leak at the bottom of the door, you may need to adjust or replace the door sweep.  Do not waste your money with the self-sticking foam, it generally is not the correct type of too use and will not last long.

Backing Material

Depending on the area’s that need to be filled, you will need more than caulking. If the joint exceeds a ¼ of an inch, you will need some sort of backing material installed like a foam-backing rod or expanding spray foam. In some cases, you may need to use foam board, drywall, wood, or some other sort of material to block the air. Cotton or fiberglass insulation which used to be popular as a blocking material around doors & windows does not do a good job preventing airflow – it makes a great filter though. We strongly recommend against using this material as there are better options available.

Air Sealing & Insulation Series:

Other Related & Upcoming Articles


  • Amelia

    Heard about this site from my friend. He pointed me here and told me I’d find what I need. He was right! I got all the questions I had, answered. Didn’t even take long to find it. Love the fact that you made it so easy for people like me. More power

  • Franking70

    FYI- Clean up – please refer to the directions (One trick we use is after the foam has dried trim it using a hacksaw blade) Do not do this if you are using closed cell foam – as you are then creating open cells allowing air leakage.

    • SLS Construction

      Thanks for commenting & always a good point on refering to the directions. Onto the hacksaw trick, while you are technically correct about creating some open cells that is only on the surface area where it has been cut. If installed properly you are not allowing for any air leakage and any other system will also create some if it requires trimming