Spray Insulation & Air Sealing for New Homes(Last Updated On: February 28, 2019)
Everyone knows insulation is important in a house, but air sealing is also important. Here we will be touching on both subjects and their relationships. Insulation and air sealing are essential for building Sustainable Homes and is a core principle of Passive House Design.
Insulation And Air Sealing
Spray Insulation types and why air sealing is important.
All the information in this post is targeted for what we call cavity insulation. This is where you put insulation between wood or metal studs, joists, or rafters. I will not be discussing Exterior insulation and Finish Systems (EIFS)– I will do another post on that in the future. This is for stick built wood or metal framed houses. We will focus on spray insulation, but I will discuss a few other products.
We all know insulation is important to reduce your energy usage in heating and cooling, but if you build a new home with a great deal of insulation that is also leaking air you are not getting a great value for all the insulation in the house. Spray insulation is a foam that is, sprayed in between your wood or metal studs, this foam expands and gets into all the cracks, holes, and joints around windows, doors, or anything else in your walls, floors, or roof. Anything going through your insulated surface be it a door, window, pipe, exterior lights, exhaust vents to name a few create week points to your air sealed house as well as cracks and construction flaws. The goal is to make sure the conditioned air inside your home does not escape through your walls. Cellulose insulation and batt insulation (batt is the stuff that looks and feels like cotton candy) do not stop air from leaking though your house.
Spray insulation expands and fills all these places where air can escape so what are the different types of spray insulation?
New Insulation Types
Insulation is becoming more important and we will continue to see new insulation types appearing on the market. Since becoming available spray insulation has grown in popularity. The value of insulation thermal properties is measured by R-Value. The higher the R-Value the better.
There are two kinds of spray foam insulation Closed Cell and Open Cell.
Open Cell Spray foam Insulation:
- Open cell spray insulation is more affordable than closed cell insulation.
- Open cell insulation has an R-value of typically R-3.5 or a little more per inch.
- Open cell provides air sealing keeping the outside air out and the inside air in.
- Open cell is not water or vapor resistant.
- Open cell has no structural value.
Closed Cell spray foam Insulation:
- Closed cell spray insulation is more expensive than open cell spray insulation.
- The R-value of a closed cell insulation is typically R-6 to R-6.5 per inch (that is a very good R value).
- Closed cell provides air sealing keeping the outside air out and the inside air in.
- Closed Cell insulation is also vapor resistant water resistant and will not allow vapors, humidity, water to pass through it.
- Closed Cell insulation is denser, heavier, and stronger. Closed cell is the only insulation that will actually add structural value to a wood or metal framed wall or roof. It adds rigidity and stability to the framing of the house increasing the entire overall structural value.
Economy is obviously an issue. Although closed cell is more expensive it does have several advantages as we see in the list above. Also, realize you will less closed cell insulation would be required than open cell insulation to achieve equal R-Values.
Tips for saving money with spray insulation.
Yes, closed cell spray insulation is expensive keep the benefits of air sealing and moisture control in mind. So one thing you can do to save money is to first put in place a minimum of 1 inch layer of closed cell insulation minimum 1 inch any less and it wont be doing anything. But do a 1 or 2 inch first layer and then you can go over it with the lower cost open cell insulation or even install Batt insulation over it.
How do you know your home is air sealed? Blower Door Test!
We often test the homes we build using the blower door test to check that they are air sealed. A blower door test is a system for measuring air flow. Simply put, a plastic cover is placed over a door with a fan in it. The fan blows air into the house and a pressure monitor detects the rate at which the air is escaping by the differential in the air pressure. This is a great way to know if your house is performing well in the air sealing department.
Our goal here is to make sure you understand that if you put a ton of insulation in your new home but the house itself leaks air you are not getting the full effect of the insulation. Be mindful of these issues as we are all trying not only to save a little money but pitch in anyway we can to help the environment. Higher quality insulation may bring a higher upfront cost but the long term savings are huge.
I hope this was helpful in helping you understand a little more about different types of insulation.
Thank You for reading our blog post on Spray Foam Insulation
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Author Jorge Fontan AIA
This post was written by Jorge Fontan, a Registered Architect and owner of Fontan Architecture.