New Home Insulation Diagram

Spray Insulation & Air Sealing for New Homes

(Last Updated On: November 22, 2018)

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 EIFS I will do another post on that in the future. This is for stick built wood or metal framed houses.

We are also going to focus on spray insulation but I will discuss a few other products.

Must know – the value of insulation thermal properties is measured by R-Value. The higher R-Value the better.


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.

Spray Insulation

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 need less closed cell insulation than open cell to achieve equal R-Values.

Spray Insulation for new homes

Spray Insulation for new homes (this is in a house we did in NY)

Tips for saving money with spray insulation.

We know closed cell spray insulation is expensive but we like that air sealing and vapor retardant value. So one thing you can do to save money is to first put a 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 for how well air sealed they are and this is done with a blower door test.

Insulation and air sealing Blower Door Test

Blower Door Test being conducted on one of our houses.


A blower door test is a system for measuring air flow. Simply put it is done by putting a plastic cover over a door with a fan in it. The fan blows air into the house and a pressure monitor detects the rate the air escapes 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 affect 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

Please leave questions and comments below. If you want to speak with an architect about a specific project you can contact us directly. Learn more about our services as house architects and sustainable design architects.


New York Architects, Jorge Fontan

Author Jorge Fontan AIA

This post was written by Jorge Fontan, a Registered Architect and owner of Fontan Architecture.

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