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air ventilation systems to control odors

Peg Member Posts: 2
edited May 2021 in Indoor-Air Quality
We moved into our 60 year old house in Nov. and I immediately noticed an odor that smelled like burned wood that had gotten wet (that's the only way I can describe it!) It is worse around the outside walls of the house, I thought it was smoke coming in from neighborhood fireplaces but have since eliminated that source. The weather here has finally warmed up enough to open the windows so I did a good airing out, but the odor returned within 2 hours. I brought in a business who combats bad air in homes and his proposal is to install a huge fan in the crawlspace as well as add air vents to the outside walls around the house. He believes that the odors are a build up of fumes from carpet, flooring, ect. and having a too tight energy efficient house. Out highly efficient boiler was installed 7 years ago and we have a very heavy layer of insulation throughout the crawlspace and attic which seemed to have covered the original venting to the outside so I can see the logic in his solution. BUT, at a $ price tag. Can you give me some insight?


  • Jamie Hall
    Jamie Hall Member Posts: 21,560
    He could well be correct. The generally accepted range of air changes per hour from the outside to preserve indoor air quality is around 2 to 4 complete changes. In a more or less typical 2400 square foot house, that would be around 1500 cfm.

    It is not that uncommon for an overambitious insulating and air sealing program to reduce the ventilation to below that -- sometimes well below that -- and in such cases the only solution is to provide a fan or blower to provide the flow, and an intake of sufficient area to allow the air in. Ducting may be required to get adequate distribution of the air in the structure.

    This does, of course, lose heat -- so if that is a concern, a heat recovery ventilator should be part of the package, which also costs money and requires ducting.

    I might add that this is not solely an odour problem. It is also a health problem, and can be a rather serious health problem. In some areas of the country a radioactive gas called radon is present naturally in the soil, which (not to scare you, but...) can be more or less the equivalent in terms of health of two to three packs of unfiltered cigarettes a day. In the shorter term, many modern materials -- plastics, artificial fibre fabrics and rugs, and some insulation materials -- also produce an interesting (in the clinical sense...) array of airborurne compounds. Not to mention airbourne virus and the like.

    There is much to be said for fresh air...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 19,958
    It would sure be nice to find out the source of the smell and deal with the cause not the symptom
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Peg
    Peg Member Posts: 2
    Thank you to both of you. I spent the winter trying to track down the smell. I thought fresh paint and removal of very old wallpaper would help, and installed new windows when I was still thinking it was coming from outside. We removed the radiator covers,( hot water heat), and cleaned them all as well as (carefully) cleaned around the fins down to getting the accumulated dirt off the pipes and from behind. I also wondered if it could be coming from the covers themselves which had been painted over several times, thinking that the hot paint was releasing fumes. I had a boiler person come to see what he could tell us and naturally, he couldn't detect the smell. (neither could my husband but that is a different saga...) I had thought it was the heat pipes because the smell was strongest around them, but it could be that there are openings from the crawlspace for the pipes. Yes, and there are health issues, congested chests, sneezing and runny noses. I really needed to get to the bottom of this and it seems that the person who proposed the changes seems to understand the problem so it appears that we need to bite the bullet.
    EBEBRATT-Ed Member Posts: 13,844
    I would suggest venting the crawl space and using an energy recovery ventilator which will recover some of the lost heat as @Jamie Hall mentioned

    You may want to call in an industrial hygienist to check this out
  • neilc
    neilc Member Posts: 2,258
    maybe the house had a fire some time ago ?

    if you called the FD maybe they would remember the address ?
    known to beat dead horses
  • Zman
    Zman Member Posts: 7,472

    I would suggest venting the crawl space and using an energy recovery ventilator which will recover some of the lost heat as @Jamie Hall mentioned

    You may want to call in an industrial hygienist to check this out

    A reputable (not affiliated with a remediation contractor) industrial hygenist is a great resource. They would likely do mold cultures, test for radon, measure humidity, and test for VOCs. I am generally distrusting of mold remediation contractors, pay someone independent for an honest unbiased opinion.
    Does your crawlspace floor have a vapor barrier or is there exposed dirt?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 19,958
    A radon test is always a good idea, most realtors insist on them for buyers.
    A blower door test would indicate how tight the home is and show areas where outside air is leaking in. An Infrared camera could also show wet spots, try it after a rain.
    If it is making you sick I would also find a hygienist to analyze what is in the air

    I can feel it coming in the air tonight (oh lord) And I’ve been waiting for this moment for all my life (oh lord)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream