Building Sciences - Spray Foam Insulation

To Spray or Not to Spray (Insulation that is)

Foam insulation after it has expanded

Spray Foam insulation is a great alternative to traditional batt insulation for your home renovation project or addition. On one hand the batts are readily available at you home improvement stores and are easy to install. But batts can’t get in to all the cracks that are a potential for the leakage of air movement.


Types of Spray Foam Insulation.

There are two types of spray foam insulation:

1. Low Density (Open Cell) – This type of insulation has a thermal resistance of R-3.5 to R-4.0 per inch. Once open cell insulation cures, it is soft and flexible, like memory foam pillows. This type of insulation uses water to create the reaction similar to bubbles in a bath the insulation grows with water. Low density insulation can be sprayed in a cavity on one pass because the insulation expands ten times.

2. Medium Density (Closed Cell) - This type of insulation has a thermal resistance of R-6.0 to R-6.5 per inch. When closed cell insulation cures, it is hard and rigid. This type of insulation uses a chemical component to cause the reaction which is why it gets hard when it cures. This type of insulation needs a couple of passes to allow time for each layer to cure before applying another layer.


Most people will tell you that spray foam insulation is way more expensive than other forms of insulation. The answer is yes and no, it all depends on how you look at it. On the one hand, batts are cheaper and you can install them easily. On the other hand, batts do not cover all the crevices in the wall so your HVAC equipment will have to work harder to keep the space at the your comfort level. The more work, the higher the cost of operating the equipment and the reduced life of the equipment.

Some Benefits of Spray Foam Insulation.

·         Because spray foam expands, it reaches into all the cracks improving the building envelope. You could apply the spray foam insulation in your home improvement project without having to remove the entirety of you wall surfaces.

·         With the more common batts, if you compress the insulation, you reduce the thermal rating.

·         Spray foam insulation has better long term insulation versus batts.

·         It is a bit more difficult for pests to maneuver within the cavities.

Not A DIY Project.

Spray Foam insulation can greatly reduce the drafts in the house and improve the energy efficiency of your home improvement or addition project, but you really need to get a professional installer. One reason is that when the spray is applied is quickly expands to fill the cavity. If too much spray is used the foam will come out of the cavity and you will have to do more work to cut the excess foam. This is a little easier with low density (open cell) insulation vs medium density (closed cell) insulation, but the cleanup is messy. Professional installers have been trained on how to apply the insulation, so it is best that they take care of the application.

Foam insulation at an area difficult to properly insulate with traditional batts

All insulation types have their advantages and disadvantages. Regardless of the type of insulation you decide to use for your next home improvement, remodel or new construction, you will always need to insulate. Check out our other posts for more information.

Check out this video of foam insulation being installed.