Here in the Pacific Northwest, our temperatures can get pretty frigid in the winter, so keeping the heat in and cold out is important. Insulation is a crucial part of the building process that keeps you and your family comfortable inside your home—and because it’s hidden underneath finished walls, it’s not something you want to risk having to redo.  

When it comes to selecting the right kind of insulation, you have a range of materials you can choose from, from natural fibers to fiberglass. The problem with using only one of these traditional types of insulation is that they’re not perfect—gaps at the corners and edges of walls can still let outside air in, which makes it harder to control your home’s airflow. Spray foam is a great option developed to fill those gaps and create an air barrier that makes your insulation more effective. And just like the name suggests, it's applied using a spray nozzle, allowing you to cover an area quickly and efficiently.

We tried spray foam out for ourselves and invited our friend Michael McCarthy of DAP Products to walk us through the benefits and best practices of working with spray foam insulation. Here’s a recap of what we learned from Michael:

Where can you use DAP Two-Component Spray Foam?

There are many ways you can use two-component spray foam, but the most common is for insulating smaller jobs or hard-to-reach spaces. (For larger jobs, you’re likely better off consulting an insulation professional who has the equipment to efficiently do the job.) If you’re using spray foam to entirely fill stud bays or insulate something like our skylight wells, you’ll want to apply the spray foam in multiple layers. Each layer should be applied no more than an inch thick at a time, allowing time for the product to expand and cool before applying the next layer. 

What problem does spray foam solve?

When you use only traditional insulation materials in your walls without sealing up the cracks, you’re likely to have airflow (which is why you’ll sometimes find dust and debris when you remove old wall insulation). DAP’s Two-Component Spray Foam product is a closed-cell foam that expands on application to create a highly effective air barrier—which is great for getting into those small nooks and crannies to block airflow. By adding that extra air barrier, your insulation will perform better, and you’ll have more control over the airflow through your house. This is sometimes referred to as the “flash and batt” method.

Spray foam is also great for insulating the more unique surfaces in your home’s design; for instance, brick or metal walls or oddly shaped places where you can’t fit traditional insulation.

Where should you avoid applying spray foam?

Don’t apply spray foam in high heat areas or near open flames (applying over wiring and plumbing in your walls is OK). Avoid really tight spots where you’re filling the whole area up, keeping in mind that the foam expands as it dries, so overfilling can cause problems.

How do the two components work?

The “A” and “B” chemicals work together to cure and expand the foam. You can’t achieve your goal with just one component—both products need to flow continuously to expand and cure correctly. Once you start, if possible, it’s important to continue with the job until it’s complete, as the foam will clog up the spray nozzle if it stops flowing for too long. If you need to stop and restart, simply remove the nozzle, clean the end of the hose, and attach a new nozzle.

Is there any prep work involved?

The chemicals in the two canisters need to be at the proper temperature (at least 70 degrees F) to flow properly. DAP recommends storing the product indoors where it can maintain a warm temperature. We used a temperature gun to measure the outside of the canisters to give us an idea of the temperature inside.

It’s also important to shake the product up before using—up and down or side to side. Shaking ensures the chemicals inside the canisters are properly mixed.

What are common mistakes to avoid?

Don’t pull the trigger too hard when you start—ease into it as you move the spray gun across the wall. You’ll get a better sense of the responsiveness of the trigger and have more control of where the product is going. Pulling too hard at first can result in too much foam in one place or in places you don’t want it.

How do you know if you’re applying correctly?

The most important thing to look for is the consistency of the product when it leaves the nozzle. If it’s too watery or too fluffy, it could be that the nozzle is plugged up and the two components aren’t mixing correctly. To troubleshoot, take the nozzle off, clean the end of the hose thoroughly, spray a test batch without the nozzle to ensure the chemicals are dispensing correctly, and then attach a new nozzle and continue spraying.

Anything else you should have on hand during application?

If you’re spraying several different areas that are far apart (like our skylight wells), you’ll want to make sure you have enough nozzle tips to allow you time to stop and start accordingly. Additionally, if you’re spraying hard-to-reach areas that are up high, you’ll want to purchase a longer hose to allow for more space between you and the canisters. 

Once opened, the product has about 30 days of shelf life before it expires. If you find yourself with extra product, be sure to keep extra nozzles and hoses on hand if you plan to use the product on a different project within that 30-day window—especially if storage conditions are cold.

Recent updates to spray foam

Washington State recently enacted legislation to reduce the emission of VOCs (volatile organic compounds). All DAP Two-Component Spray Foam products manufactured after January 1, 2021, comply with new regulations.

Insulating with spray foam may sound a little daunting, but with the right product and a good understanding of the process, it’s more accessible to a homeowner than you might think (and it’s pretty fun, too). We hope this interview gives you the confidence to tackle your next insulation project—and in the meantime, be sure to check out how to improve your home’s air quality and energy efficiency for more insulation tips.