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How to Insulate with Spray Foam

How to Insulate with Spray Foam

Spray foam insulation isn’t new, but its popularity is growing. Whether you are building a new building or upgrading the energy efficiency of an existing home, spray foam insulation is a great option for protecting your home from hot and cold weather. Spray foam is easy to install and does a great job of sealing even the tiniest cracks that let outside air in.

What Is Spray Foam?

Spray foam insulation is a mix of two chemicals that are sprayed on walls and other surfaces that need to be protected from heat transfer. The chemicals react and expand in a foam many times bigger than the initial spray. This expansion fills the space where the foam is sprayed and covers any cracks or small holes. The foam dries and hardens into a firm block that provides protection from drafts and heat transfer.
Foam insulation is better at sealing small or oddly shaped spaces than any other kind of insulation. Since it expands after spraying, the foam will force its way into these little spaces and block airflow. Other insulation types won’t do this, and can even settle and pull away from the tops of insulated spaces.

Spraying Foam

To install spray foam, you spray a thin coat over the surface to be insulated. It will stick to the surface and expand on its own. When spraying foam, the most important thing is to get an even coating. If the coating is lumpy or uneven, the thermal protection is also uneven. You won’t get the best insulating power unless the coat is all the same thickness.

spray foam insulation

Dress for Success

When you are spraying foam, make sure to wear a full set of protective gear.

  • Goggles and a respirator are the most important – you don’t want to get foam in your eye or breathe the fumes. Those are both sure-fire ways to visit the emergency room.
  • Wear gloves and keep all of your exposed skin covered as well. The foam is caustic before it’s dried and will cause burns.
  • You should also wear coveralls or at least old clothes when spraying foam insulation. It will stick to your clothing and won’t wash out, so whatever you wear will have foam puffballs stuck to it forever.

Insulating Floors with Spray Foam

Spray foam insulation is a great way to deal with cold floors in rooms over uninsulated spaces like pier-and-beam homes or rooms over garages. Adding foam insulation under the floor keeps cold air from seeping up into your home and keeps the floor nice and toasty.

To insulate floors with spray foam, start by clearing out all the junk from the crawlspace or the garage. Use plastic sheeting to cover any walls or immovable objects that you don’t want covered in foam. Once everything is prepped, you can enter the crawlspace and start spraying.

When you spray, try to get an even coating of foam over every bit of the bottom of the floor, including in corners and little odd spaces. Make sure you spray around any pipes, wires, or cables that come up through the floor as well. The little holes around these things are the worst places for air infiltration that need to be sealed.

The hardest part about insulating floors is access – you need to get under the house and spray the foam up on the bottom of the floor. A project like this will really show you why the area is called a “crawl” space. You might want to add knee and elbow pads for getting in and out of the work area. Make sure you have a good work light source and take your time installing the foam.

Insulating Ceilings with Spray Foam

One of the biggest areas of heat loss (or gain, in the summer) is from the ceiling to the attic. Adding insulation to the ceiling is a great way to stop this heat loss. Modern building codes require insulation in ceilings, but there is usually room for improvement from spray foam.

Ceilings are full of holes for light fixtures, vents, and other items. Every one of these holes is a route for heat to escape. Spray foam is the best choice for sealing these holes. While other kinds of insulation can come up to the edge of fixtures or vents, they don’t really address the actual holes. Spray foam does address the holes, by swelling up and filling them.

Ceilings are usually easier to insulate floors because you can stand up and walk around in the attic. While you are up there, make sure to step on ceiling joists only. You can’t walk on a drywall ceiling, and bad things will happen if you try.

When you get to the attic, installing spray foam for the ceiling starts the same way as for the floor – by moving things out of the way and covering things you can’t move. There should be less to cover with a ceiling application because you are spraying down, not up.

Once everything is covered, start spraying. Keep the coating even and get every bit of the ceiling, especially around lights and vents. The foam will fill all the voids and cracks and seal your ceiling against drafts.

Insulating Walls with Spray Foam

For new construction, walls are easy to insulate with spray foam. It goes in after running wires and plumbing, but before the drywall (or other interior wall material) is put in place. You spray foam in the cavities between the studs and let it expand to fill the gaps. This is much easier than using other types of insulation because there is no measuring, cutting, or attaching insulation.

You just spray and go.

Walls in existing homes can be tougher to insulate than floors or ceilings because they are hard to get into. If you are doing a complete renovation that involves removing the drywall, the process is the same is for new construction – you spray foam in the cavities between studs.

If gutting the inside of your house doesn’t appeal to you, spray foam actually offers a better option. You can fill existing wall cavities with spray foam insulation by making some small holes in the drywall. How small? About half an inch.

The process starts just like every other spray foam installation, with cleaning up and covering things up with plastic sheeting. Once that’s done, you drill two holes in each stud cavity, one at the top and one in the middle. Using two holes assures that you will get full coverage inside the wall. Check the insulation manufacturer’s directions for the exact hole size and placement.

When the holes are ready, you spray in special slow-expanding foam. This foam insulation takes longer to expand so that you don’t accidentally overfill the hole. After all the walls are full, you come back with spackle and seal the holes up. The final step is painting over the holes, and you’re done. This is so much easier than removing drywall or cutting big holes in the siding to blow in insulation.

Insulating Attics with Spray Foam

Attic insulation is a little more complicated than adding spray foam insulation to other areas of your house. In most homes, the insulation on top of the ceiling marks the barrier between insulated and uninsulated spaces. The barrier to airflow is at this level, and the attic is designed with venting to allow airflow.

When you add spray foam to the attic ceiling – the bottom of the roof – the attic becomes a temperature-controlled space and needs to be sealed from the outside. The process of spraying the insulation is the same, but you must make sure to seal everything, including soffit vents.

Air vents from the house to the attic, such as bathroom or stove exhaust fans, have to be extended so the air vents outside the house. You need to seal up everything that could let air from outside to the attic.

The benefit of all this is that your attic will no longer be subject to the extremes of temperature that open attics get. Any heating or air conditioning equipment in the attic has a much easier time maintaining comfortable temperatures in a sealed space than in a vented attic.

Insulating Metal Buildings with Spray Foam

Metal buildings benefit greatly from spray foam, and they are one of the easiest types of building to insulate. Standard metal buildings are just boxes that keep the rain out. They are cold in the winter and sweltering in the summer. The good news is that the large expanses of flat wall are super easy to insulate – just cover the electric outlets and light fixtures and start spraying.

Final Thoughts

Spray foam insulation is a terrific product that can really increase the energy efficiency of your house. It’s easy to install in all parts of your house, no matter if it’s new or existing construction.
If you are looking for ways to improve your home’s energy efficiency, check out spray foam insulation.