Hi, this is Robert Naini, your Spray Foam Advisor. Today I want to talk about builders.
Specifically, when you start talking to a new builder or prospective client, someone that doesn’t work with you, someone that doesn’t use spray foam, there needs to be a conversation about how spray foam changes the way buildings work.
If they have already started the process, if the building is already designed using fiberglass or cellulose insulation, what needs to be reviewed to make the transition to spray foam?
This is really a great question to consider as you are talking to builders because you are going to come across builders who already have designs in the planning stages and structures currently under construction.
These buildings already have HVAC calculations done based on a traditional building envelope and when you introduce spray foam to that structure, you are fundamentally changing the way the building envelope works, right.
You are changing the thermal dynamics from an insulation perspective, the air flow dynamics, and possibly the vapor retarder characteristics of the building.
This is going to impact the heat flow, the moisture flow, and the overall temperature dynamics of the structure.
So, the Manual J calculations for these structures, the sizing and design of their mechanical systems, should be verified based on the new building envelope.
The Manual J calculation takes into account lots of different components:
- The orientation of the building
- The percentage of area that is windows, also called glazing
- The amount of duct leakage
- Where are the ducts are located?
- Natural Air Changes per Hour
All these variables are going to be incorporated into the Manual J calculation that the HVAC contractor or mechanical engineer does.
What they really need to know is that when spray foam is introduced into a building enclosure to create an unvented attic, the air tightness goes down, the structure gets tighter and there is less air leakage – this should be reflected in the manual J calculation.
The duct leakage is reduced to zero, because the ducts are inside condition space and the duct losses are maintained inside the building envelope – this should be reflected in the manual J calculation.
When these benefits come together the size of the mechanical system is typically smaller when using spray foam compared to a traditional design using fiberglass. This has been Robert Naini with Spray Foam Advisor, thanks for checking this out and catch me on some more videos.
