Question

We are considering spray foam insulation. How can we supply fresh air in a tightly sealed home?

Asked by Rahul Baijal
Sugar Land, TX

My wife and I are considering using whole house Icynene for our new home in Houston, but are concerned about the HVAC requirements with such a tightly insulated home. Our builder has not used Icynene, but their HVAC subcontractor has. My primary concern is how to achieve appropriate fresh air in a tightly sealed home and appropriate moisture control. The more I read, the more confused I get. I have read options from an ERV to a whole house dehumidifier (but is this necessary if the sizing is appropriate?) to simply fresh-air intake. The "green builders" and others I have spoken to recommended a filter on the fresh-air intake and definitely a 95% variable furnace. Are there any considerations for whole-house ventilation that I should keep in mind? What are my options? How do they differ functionally and financially?

Answer

Jason Kliwinski

Answered by Jason Kliwinski

Lambertville, NJ

The Green Living and Building Center

November 19, 2010

I have used spray foam insulation on most of my residential projects.

  • The filter on the fresh-air intake and 95% efficiency variable furnace are good suggestions for efficiency and good IAQ but have little effect on providing actual fresh air to the house.
  • Tightly sealed homes require mechanical ventilation.
  • It is a bit of an oxymoron and will use energy, but far less than building a leaking home and trying to heat and cool that.

In my spray foam constructed homes, at a minimum, I require a simple mechanical exhaust fan be installed and run on a timer to ensure a minimum number of air changes in the home.

If you are installing a central air system in the house, that is good, but you still need an exhaust fan that will move the air out of the house. You cannot rely nor do you want to rely on leaky windows or opening doors for the air exchange to take place.

 

For more information:

Read Andy Ault's Q&A "Do you recommend bio-based soy foam insulation?"

Tagged In: home air quality, spray foam, air exchange system

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