Using Spray Foam Insulation In Exterior Walls

  • 8-40 hours
  • Beginner
  • 200-2,000

Spray foam insulation is a very popular way of keeping the interior of homes warm during the coldest parts of the year. Spray foam is well known for its ease of use and installation within a variety of exterior walls surfaces. However, there are many things that homeowners still have to learn about spray foam insulation. These points are integral to the efficiency and can save you from wasting money by choosing the wrong materials of using them incorrectly.


There are three different types of spray foam insulation in three-pound, two-pound, and half-pound varieties. Three-pound foam is the thickest and will therefore provide the greatest insulation. Two-pound foam is usually the foam of choice for exterior walls and creates a primary barrier against the cold but will commonly be covered by other materials. Half-pound foam is used between sheets of sheathing which can be found in many roofs and exterior walls. Half-pound foam is also very common for insulating exterior walls.


The higher the density of the foam, the higher it will cost to buy. Half-pound spray foam is the cheapest option but it will not be as effective. You can get custom sheets of spray foam cut to size if you supply detailed measurements of your exterior walls. However, this service also comes at a slightly higher price. There are many different manufacturers of spray foam so shop around until you find the most competitive price.

Ease of Use

Spray foam is one of the easiest insulation materials to use. The softness of the foam allows you to cut precise measurements. You can also make small adjustments as you work if needed. The softness of the foam will also allow you to fix spray foam to the exterior wall securely using a number of common items that you can find laying in most garages or workshops. Using spray foam insulation in exterior walls is popular because it is easy to handle and simple to install. The spray foam should fit comfortably within the edges of any sheathing you already have on exterior walls.


You need to bear in mind that dense spray foam will trap moisture between the foam and wall sheathing. This can create slight damage to the structural integrity of the wall. The half-pound foam will soak up a little of the moisture which will eradicate this problem. However, it will also mean that you will have to change the spray foam more often in order to keep it effective. Using a denser foam will mean a complete re-installation of the spray foam as opposed to using it in a specific section.


You need to keep in mind that if you have spray foam insulation on exterior walls, the foam will expand a great deal over time. Therefore it's advisable to buy slightly less in the first stage than your measurements tell you. As well as saving you time and money with expensive re-work, always remember that purchasing too much foam will generate landfill waste. Monitor expansion at regular intervals if you choose to use spray foam insulation on your exterior walls.