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Community and Q&A

Spray-foam home — ventilation?

Mark Sokolowski | Posted in Green Building Techniques on

I hope you can help. I’m in a less-than-a-year-old, production-built, spray-foamed, tight, energy-efficient, 2-story home outside Orlando, Florida, 1,758 square feet, which developed “sewer”-type odors on the first floor.

The builders solution so far has been to install an inline “booster” fan to the fresh air intake on the AC system to meet ASHRAE 62.2. But now, understandably here in Florida, indoor humidity has risen dramatically.

Is my correct/best solution to install an ERV? I don’t want to just crank my AC down to remove the humidity, as that defeats the purpose of an energy-wise home. I need the builder to understand what the correct thing to do is.

Thanks for the help.

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  1. GBA Editor
    Martin Holladay | | #1

    The first step is to determine the source of the odor. It could be from your drain pipes (perhaps from a plumbing trap that has evaporated). It could be from your spray foam (in which case you should read this article: Spray Foam Jobs With Lingering Odor Problems). It could be from a dead animal that died inside a wall cavity.

    Until you have identified the source of the odor, it's impossible to give you any advice.

  2. Mark Sokolowski | | #2

    Thanks Martin-the odor has now been gone for a few weeks (but its what started this ventilation issue), so my main concern now is determining the correct ventilation for a spray foamed house here in FL with this humidity. This fan just forcing in untempered moist air just cant be right. Thanks.

  3. GBA Editor
    Martin Holladay | | #3

    There is no single answer to your question. For a full discussion of both side of this question, see How Much Fresh Air Does Your Home Need?

  4. Mark Sokolowski | | #4

    Thanks for the link & info Martin. I'm just trying to determine the best/right/smart thing to do in my situation. I know I need to get a handle on the influx of humid air into the house.

  5. GBA Editor
    Martin Holladay | | #5

    If your home is tight -- and many homes that have spray foam insulation are relatively tight -- you probably need a mechanical ventilation system. I'm not sure what your builder means by a booster fan; it sounds shady. Make sure you understand ventilation systems before proceeding, and make sure that the airflow of any installed ventilation system is measured (in other words, the system has to be commissioned).

    Here's more information on ventilation systems: Designing a Good Ventilation System.

  6. Mark Sokolowski | | #6

    I already had that article set to read, thanks Martin. This booster fan is the TD-150 Mixvent from Soler Palau, they installed it on the fresh air intake vent for the ac system to force more fresh air into the home. I didn't see anywhere on SP's website where this was a proper use of this item. The builder I'm sure is hoping this will do it as it's cheaper than an ERV, but clearly it's not. IMO they need to include an ERV as a part of the installed HVAC system up front, esp here in sweaty FL. Thanks again, Mark

  7. Steve Knapp CZ 3A Georgia | | #7

    You might want to contact David Butler at Optimal Building Systems, LLC. He could evaluate your design and possibly offer some strategies for improving the system.,
    520-439-9365 (home office).

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