It is possible to install spray foam insulation in an existing wall, but it is a more difficult process. First, you will need to remove the drywall or paneling from the wall and then use a stud finder to locate the studs. You will then need to cut the foam to fit around the studs and attach it with screws. Finally, you will need to reattach the drywall or paneling.

There are a few ways to install spray foam insulation in an existing wall. One way is to drill small holes in the wall and then insert the straws that come with the insulation material. Another way is to cut a hole in the wall big enough for you to fit inside and then insulation can be sprayed through from the inside. No matter which method you use, make sure that you read and follow the instructions carefully, as there are specific guidelines for each application. Also, be sure to wear all of the necessary safety gear, including a respirator, when working with this type of insulation material.