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  1. #1
    Join Date
    Aug 2005
    Location
    Grafton, MA, but sometimes on another planet
    Posts
    568

    Default Ventilation Issue??

    All,
    I thought I'd solicit some opinions on options to address a basement moisture/ventilation issue. Background is house built circa 1800 with stone foundation and originally dirt floor. Somewhere along the line the floor got partially poured. Water leaks in through the foundation at various places and runs into a gutter along the base of the walls. Oddly, the space does not seem to accumulate mold and mildew. However, there is a lot of moisture in the air that moves into the living space. Of course if money was no object one could jack the house, put in new foundation, etc., but that is not going to happen. So what do folks think might work best for short money?

    Don
    I started out with nothing. I still have most of it left.

  2. #2
    Join Date
    Nov 2007
    Location
    Dallas,PA
    Posts
    1,054

    Default Re: Ventilation Issue??

    Don, probably need more info before making recommendations but.... in general, if you are trying to diminish the moisture laden air strictly with a ventilation approach, I would think that you have to isolate the basement from the living area with as functional an air barrier as possible and then ventilate the crap out of the basement. This would require the central heating plant be removed or isolated within the basement and insulating the mechanical lines that are in the basement as well.

    Can any corrective measures be taken with regard to the leaky foundation? How about pouring the remaining floor and including a vapor barrier. Is the area of floor that is poured able to be treated with a liquid applied vapor diffusion coating?

    I know exterior measures can be difficult and expensive but in the long run they are the best solution. Maybe you can convince them to excavate and install a water/vapor barrier like EPDM on the outside of the foundation. Can you install exterior perimeter drains and dump them to daylight? Maybe take it on a "phased" approach over a few years.
    "ALS IK KAN" - Stickley

  3. #3
    Join Date
    Aug 2005
    Location
    Grafton, MA, but sometimes on another planet
    Posts
    568

    Default Re: Ventilation Issue??

    A little more information...

    When I said the floor was partially poured, I mean that they really "can't" pour the rest of the floor because there is a huge chunk of granite(about 30% of the basement space) and other detritus covering the un-poured portion. Short of some serious blasting/jack-hammering it isn't going anywhere.
    I was thinking maybe somehow adding something like best effort to cover the exposed pile with plastic, apply "membrain" or similar to the ceiling/floor joists and putting in some kind of continuously operating mechanical ventilation system (HRV?) might help. I was also wondering about radon issues. I don't think anyone has ever tested the space.
    Trenching the exterior may not be possible as I suspect that there is a LOT of granite all around the foundation area. I'm open to all ideas. Maybe all I'll get are just partial solutions, but they may help. The current situation is that they get some serious moisture formation at all windows during both summer and winter. The windows are all new replacements installed about 5 years ago.

    Don
    I started out with nothing. I still have most of it left.

  4. #4
    Join Date
    Oct 2007
    Location
    Southern California
    Posts
    2,184

    Default Re: Ventilation Issue??

    Does the house have gutters? Is the water ducted away from the house?
    Does the ground around the house slope away from the house?
    Do the bathrooms have exhaust fans with humidistats?
    Are there any unvented gas appliances in the house?
    Is there room to put a radon/drain system on the floor, then pour a slab over it?
    HERS Rater • BPI Building Analyst • BPI Envelope Professional
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  5. #5
    Join Date
    Jul 2007
    Location
    Northern Jersey
    Posts
    1,283

    Default Re: Ventilation Issue??

    Quote Originally Posted by DonMirabito View Post
    A little more information...

    I was thinking maybe somehow adding something like best effort to cover the exposed pile with plastic, apply "membrain" or similar to the ceiling/floor joists and putting in some kind of continuously operating mechanical ventilation system (HRV?) might help. I was also wondering about radon issues. I don't think anyone has ever tested the space.
    I think your on the right track here.
    Tom

  6. #6
    Join Date
    Dec 2005
    Location
    Michigan
    Posts
    7,543

    Default Re: Ventilation Issue??

    Ventilation only works if you're in a dry climate. In my area, summers are very humid so it's counterproductive. I try to manage exterior water the best I can (gutters, etc) and supplement the air conditioner with dehumidifier(s). In your case, I would also channel the gutter at the base of the walls into a pit and pump it out so it doesn't sit and evaporate

    If the problem is severe, there are only big bucks solutions.

  7. #7
    Join Date
    Feb 2007
    Location
    Portland Maine
    Posts
    434

    Default Re: Ventilation Issue??

    Fairly quick and dirty method we often do is dimple drainage mat on the foundation walls, EPDM roofing membrane on the floor and some CC spray foam to glue it all together. You want to provide a sump or daylight drain, and grade all the trenches to the drainage. It's pretty effective for relatively short money. Attaching the dimple mat can be a challenge also depending on the foundation, but it's generally easier than trying to establish and air and vapor barrier at the ceiling level.
    Mike


    The Democrats are the party that says government will make you smarter, taller, richer, and remove the crabgrass on your lawn. Republicans are the party that says government doesn't work, and then they get elected and prove it. -P.J. O'Rourke

  8. #8
    Join Date
    Nov 2007
    Location
    Dallas,PA
    Posts
    1,054

    Default Re: Ventilation Issue??

    Don, MemBrain by CertainTeed is a selective vapor retarder. When the relative humidity is high, as will undoubdtedly be in the basement, the product actually adjusts its perm rating to allow the vapor to pass.

    I think the cc foam on the bottom of the floor assembly may be the best alternative to prevent passage of vapor to the living area. Don't forget to seal the door threshold and stops with suitable weatherstripping to prevent passage of moisture laden air. Also, you may have to coat the foam with a suitable flame spread rated covering. Then adding a mechanical ventilation system may at least dispense with some of the build-up of humidity in the basement.

    I am sure you are cognizant of the exterior grade and gutter issues as have been referenced.

    The chunk of granite in the basement may not be such a huge issue as it probably has a very low permeance and is not such a big contributor to the vapor load. It MAY be a big condenser though and perhaps a coat of foam on that as well will do double duty... stop condensation and help prevent vapor flow for whatever extent there may be through the stone.

    The only issue I have with covering the walls on the inside is the fact that the resultant high rate of humidity, (behind the barrier), may in fact start affecting the wood sill and any other organic material that may be contained within that chamber. You don't want to saturate the sill.
    "ALS IK KAN" - Stickley

  9. #9
    Join Date
    Aug 2006
    Location
    Leominster, MA
    Posts
    927

    Default Re: Ventilation Issue??

    A French Drain system would help with the drainage issues, as well as a vapor barrier on the cellar ceiling. There are fans made just for basement/crawl space ventilation also

    Re: French Drains, here's a link to an installation I did a while ago...

    http://www.renaissancerestorations.c...en/jhayden.htm


    J
    Last edited by Otis P. Driftwood; 04-13-2012 at 09:06 AM.
    Renaissance Restorations LLC
    www.renaissancerestorations.com

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