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Community and Q&A

Far from a green home but you folks are pros at controlling quality of indoor air and I could use your help

PeteA | Posted in General Questions on

Hi everyone I am having an air quality issue in my 1940’s single story home and I know that you folks are the experts at regulating humidity and overall air quality in these new super tight houses and I was hoping for some suggestions that may help me in my very low efficiency vintage home. 
I have a 800sq ft single story home in the new york city boroughs that seems to have unusually high humidity levels which really shows up in the winter time with water forming on the ceilings where it meets the outside walls and now this year mildew forming in those same areas.
When the house is sealed up for the winter, meaning windows down and heat is on that’s when it’s the worst but the house feels humid even in the summer. The house has vinyl siding over rigid foam over wood clapboard on the exterior walls and the walls are uninsulated with sheetrock on the insides. The heating system is gas, hot water with convectors. The Attic has a single layer of R-30 batt insulation which fills the whole wood joist above the sheetrock ceiling. The eaves have vents and the roof has a round thermostatically controlled fan that works. 
The foundation is poured concrete and does not have any standing water or visible leak issues. The basement is not insulated except for some insulation stuffed around the rim joists to make sure there no drafts coming in from those areas.
I am leaning towards biting the bullet and putting in an ERV/HRV on each level (basement and main floor) to try and swap out the stale damp hot air and also replace the dryer vent with a rigid pipe vent in case it’s also a contributor. I am only adding the detail of the dryer because I know if they are not running/ducted correctly they can be a contributor to this but the house has felt humid even before this dryer was here.
Can someone advise me of a plan I can start to evaluate what could be the cause of this lousy air quality and do you think ERV/HRV is something that may help here in the long run?

Thanks so much in advance, this is frustrating to say the least.

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  1. kyle_r | | #1

    I would get an energy audit done with a blower door test.

  2. Expert Member
    Akos | | #2

    Unless that 1940s house was somehow turned into a passive house, I have a feeling your fuel burner is venting into the house. I would check that first before doing anything.

    1. PeteA | | #5

      I will double check this but every year before the heating season starts I do inspect the chimney to make sure its clear since squirrels and birds do love to drop stuff in those rooftop holes to try to build their nests :) The boiler and the venting is all brand new and the humidity has been a concern of mine for long before this boiler was installed. The big change this year was the areas actually formed mildew along the areas that typically got damp/wet in the winter time.
      I will double check the boiler, the vent and the chimney though just to be certain.

  3. relztes | | #3

    The energy audit is probably a better idea, but you can learn a bit about your ventilation with a CO2 monitor like the aranet4. With 10-15 CFM per adult of fresh air, you will see about a 1000 ppm increase in CO2 over outdoor (i.e. 1400 ppm). (Actual numbers depend on food intake and activity level.) It ought to show any problems with poorly vented combustion, too.

    1. PeteA | | #6

      I do have the typical CO/smoke detectors for the carbon monoxide but I do not have anything for CO2. They seem pretty reasonable and easy to use so I will pick up one or two and place them around the house to get some trend samples

  4. walta100 | | #4

    Consider the possibility that there is zero insulation where you see the mold growing because that part of the ceiling is getting so cold that the surface is below the dew point making water condense out of the air.

    Do you have a CO detector installed?

    What is the indoor winter time humidity of the home?

    Consider getting a $30 Infrared Laser Thermometer and checking the temp of the ceiling in the winter.


    1. PeteA | | #7

      That is spot on as far as my initial issue. I bought the house in 1996 and one of the things I did right away was install r30 batts throughout the attic. The one thing I never realized up until I really looked into the condensation issues was that I did not force the insulation deep enough into the corners, so I was leaving about 4" of the sheetrock uninsulated around the whole perimeter of the ceiling throughout the house. I rectified this by pushing the insulation deeper into the corners and installing insulation baffles to allow air flow. I have a Fluke infrared camera which I will be using extensively this winter. I am really planning on doing something to circulate and freshen the air in the house this summer so I get some year round air movement through the house.

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