Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

Basement Humidity

ZmanZman Member Posts: 5,736
I am doing some long range consulting for some friends with a home on Cape Cod.

The home has 2.5 floors plus a basement. It was constructed in the late 70's. The wall and roof insulation are typical of that period. R-11 walls and r-30 roof. Overall it is safe to say that the air infiltration rate is very high.
The basement is partially finished (about 40%) with r-11 wall insulation. The remainder of the basement has bare concrete walls. There is seal coating on the outside of the foundation but no french drain. The soil is typical cape cod sand/gravel. There are no gutters on the roofs.

The complaint is a musty humid smell coming from the basement, particularly in the summer.
They have run a dehumidifier in the past and complained that it ran non stop and increased the utility bills. Never solving the problem

I will be visiting in a about a month and have been asked to look into the problem.
I would love some input on how to narrow down the problem. If I had an unlimited budget, I know I could solve the problem with gutters,HRV's, insulation and sealant. The budget is pretty limited so the solution needs to be focused.

So far I plan to send them 2 data loggers that record temp and humidity. I was going to have one deployed in the basement and one outdoors. When I arrive I will have a months worth of Data to look at. I could also bring my Flir camera and see what it tells me.

My theory at the moment is that the house has a significant natural convective current that is drawing outside air into the home through the rim joists in the basement and releasing it through the leaky roof assembly. In the summer, the air is warm and humid. When this warm humid air hits the cold concrete walls, it condenses.

Anyone?

Thanks in advance,

Carl



"If you can't explain it simply, you don't understand it well enough"
Albert Einstein

Comments

  • Bob Bona_4Bob Bona_4 Member Posts: 2,083
    Carl, what's the water table like?
  • BobCBobC Member Posts: 5,101
    I own a 95 year old house that is about as tight as a screen door. People have looked at it to quote on air sealing and thrown up their hands. I'm just happy I can afford the heating bills.

    The house was built on an old sand pit so the soils are similar. Opening a couple of basement windows might help a lot if you can be reasonably someone won't try to crawl in that open window. One thing I did a number of years ago was to install a 100cfm muffin fan in a south facing cellar window that exhausts air 24/7 and that has dropped the humidity in the cellar significantly.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Rich_49Rich_49 Member Posts: 2,540
    What kind of A/C are they utilizing Carl ? Bob's question also comes to my mind .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • John Mills_5John Mills_5 Member Posts: 935
    Whole house dehumidifier? Can be ducted into a forced air system or stand alone. Can run outside air into most for dehumidified ventilation.
  • Paul48Paul48 Member Posts: 4,492
    I also live in a house that's pushing 100 yrs old. I agree with BobC, open some windows and get some air moving. That alone will go along way to lessen the problem.
  • RobGRobG Member Posts: 1,850
    One way or another they're going to have to get gutters and downspouts that are day lighted as far away from the home as possible and they should fix any grading issues around the home at the same time. It will definitely help.
    kcoppChrisJ
  • ZmanZman Member Posts: 5,736
    Thanks for the responses. Good stuff.
    The house has baseboard heat so no ducts to work with.
    I don't think ground water is an issue, the lack of gutters is playing a part. There is likely no vapor barrier under the slab, so wicking is a possibility although no standing water.
    I hate to just dehumidify given the constant supply of humid air.
    I have considered and HRV. Smart controls on either option is a must.
    I hope I can see condensation with the flir and that the data tells me more.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • FranklinDFranklinD Member Posts: 399
    I have a 100 year old home that is also as tight as a screen door, to quote from above. I regularly would see 80-85% in the summer months.

    Best thing I did was grind all the old paint off of the block walls and re coat with 2 coats of generic Dry-Lock type paint. Since doing that, the humidity levels dropped 15% on their own. It must just keep moisture from wicking through the concrete. Brightened it up, too.

    I also air-sealed all the window frames and built new storms (with gaskets) for them, which I keep on year round. There is one window in the NE corner that I leave cracked with a small fan when the humidity outside is lower than inside.

    Otherwise, yes, I run a dehumidifier and it will run nonstop if I set it at 35%. I keep it at 45% and after 3-4 hours it will start to maintain a 30 minute cycle. Expensive, but I feel it's necessary.

    If they have a dryer in their basement, it will suck in humid air from the house or outside every time they run it too...I'm a little surprised that in this day and age of tight buildings, there aren't any 'sealed' dryers using outside air. Maybe there are some and I just haven't looked ;-)
    Ford Master Technician, "Tinkerer of Terror"
    Police & Fire Equipment Lead Mechanic, NW WI
    Lover of Old Homes & Gravity Hot Water Systems
  • BobCBobC Member Posts: 5,101
    Coating walls with a dry lock type of paint sounds like a good idea.

    I want to expand on the muffin fan I use to keep moving air out of the basement. The windows are original to the house and have 3 panes (about 7 x 12" each). I replaced one pane with a piece of lucite that I drilled a 4"hole in for the muffin fan. In the fall I unplug the fan cover it with plastic to seal it.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
    vaporvac
  • Rich_49Rich_49 Member Posts: 2,540
    Grasping at straws .

    Opening windows allows more moist air in . Running fans pulls more moist air in through every conceivable crack , gap or imperfection .
    It's kinda like people thinking attic fans (whole house ventilators) keep their attics cooler lessening the A/C load . The fan actually draws already conditioned air through the attic and new moist air in through all those imperfections .
    50% RH is very comfortable for everyone running dehumidifiers , lower than that really dries the air out .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
    Bob Bona_4Canucker
  • ZmanZman Member Posts: 5,736
    @kcopp
    Thanks for the link. He has tons of great articles.
    The factor I need to get my head around is how much of the water is coming through the walls and floor? Hopefully between the IR camera and moisture meter I can figure that out. I also wonder if there is a way (special light) that would help see the effervescence normally seen when water in coming through concrete rather than condensing on it.
    @Rich
    I do think that dehumidification will be part of the plan but not the whole plan. I think air sealing needs to come first. If I am giving the basement an unlimited flow of 70% air, A dehumidifier set at 50% does not make much sense. An HRV is also still on my mind.
    Thanks for all the feedback,
    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Rich_49BobbyBoy
  • Larry (from OSHA)Larry (from OSHA) Member Posts: 688
    Might want to consider radon testing and if needed mitigation. We had a system put in last year and basement humidity went down noticeably. In fact, whole house humidity went way down over winter which had pros and cons. Windows no longer had any condensation but levels were actually too low. My house is a little tighter than a screen door but there is room for improvement for sure.

    Larry
    Bob Bona_4kcopp
  • ZmanZman Member Posts: 5,736
    Larry,
    You make a good point. I will try to determine if there is crushed rock under the slab or just dirt. With rock, it may be possible to deal with the problem as you suggest before it enters the envelope.
    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Bob Bona_4BobbyBoy
  • Bob Bona_4Bob Bona_4 Member Posts: 2,083
    I'm thinking air sealing is a must but how to control moisture mitigation around the slab/wall junction, and through the aggregate itself? I can see a tight envelope with a swamp for a cellar. Drylock has work for me on walls, mostly.
  • Steve MinnichSteve Minnich Member Posts: 2,538
    I had a similar issue in my home. Part of it is/was over a ventilated crawlspace.

    No more.

    My solution was to encapsulate the crawlspace completely with closed cell spray insulation, pour 4" of concrete, new drain tile around the interior foundation walls, foundation cracks repaired and wall drain board added, a newly relocated sump pit and pump.

    It's been a year now and all the issues like hardwood cupping, high humidity, mold, etc. have been resolved.

    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
    https://heatinghelp.com/find-a-contractor/detail/minnich-hydronic-consulting-and-design
    Bob Bona_4
  • JUGHNEJUGHNE Member Posts: 6,791
    edited August 2015
    There was a simple test to determine the dryness of concrete.
    It was square (1' x 1' or more) of good clear vapor barrier plastic solidly taped at the edges to the concrete floor. Got to have a good smooth surface and good edge seal. Moisture would be visible after some time, (days?). Don't know if it would work on walls.
    They could put several of these around the outside perimeter and some towards the center of floor. This might tell you something. Pretty economical test.

    Question to Larry, do you have central AC?
    kcopp
  • Larry (from OSHA)Larry (from OSHA) Member Posts: 688
    Jughne, Yes we have central air. No vents in basement.

    Zman, even with just dirt under slab, the radon fan will supposedly create enough negative pressure to eliminate the stack effect through the concrete floor. Apparently a single suction point will draw from the entire slab footprint.
    Bob Bona_4
  • Bob Bona_4Bob Bona_4 Member Posts: 2,083
    My previous house I wouldn't wish on my worst enemy. Water table 16" or less. Dirt crawl/partial stone wall cellar. Dug crawl down to actual crawl depth ("footings" wouldn't allow me any deeper). 10k in Neutocrete. Not much improvement. Drylocked parged stone walls. Dug/diamond grinded a sump, dug down cellar 4" and poured slab. Still musty. Never. Again.
  • Paul48Paul48 Member Posts: 4,492
    Please allow me to grasp at some more straws......Because I Am The Great And Powerful Oz !!! No....It's just my opinion.

    Keeping the basement closed up, just allows the humidity level in the basement to build and maintain a high level. The humidity level outdoors may be 50-60%, but you maintain a lovely 85% by keeping things closed tightly. You can open it up, get some air moving and dry things out, or forever be locked into conditioning the space. If they want to use the space, heavily, that may be the only option.
    I am 1/4 mile from the beach. If you dig 6 ft down in my yard, you hit seashells. Until 3 yrs ago, we put up and took down one of those Intex pools , every year. I put just under 10000 gallons on the lawn, rapidly, and it would alway be gone ten minutes later.
  • Bob Bona_4Bob Bona_4 Member Posts: 2,083
    I think the key thing is controlled ventilation rather than letting whatever into the basement in hopes it will improve conditions.
    Rich_49
  • BobCBobC Member Posts: 5,101
    edited August 2015
    @paul48 I'm about 1/8 mile from the beach and if you dig down a foot it's all sand till you reach the great wall. When I put that muffin fan in the window pane the cellar became noticeably drier than it was when it was buttoned up. The fan draws 12 watts, real easy on the electric bill.

    Using outside air to reduce humidity in cellars may be an old wives tale but it's worked for folks around Boston for decades, in fact opening cellar windows was Peter Hotton's favorite cure for damp basements - he wrote the Globe handyman column for 50 years until his death this last May.

    If your climate is like it is around here it's the cheapest way out.

    EDIT: I want to add the fan is exhausting air from the cellar so that would probably help get rid of the musty smell in addition to lessening the humidity down there.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • FranklinDFranklinD Member Posts: 399
    I guess I should've mentioned that in my particular situation, my foundation is 5 feet deep in goopy clay and sand. I am approximately 1800 feet from the shore of Lake Superior, and about 20 feet higher than the shoreline, I think.

    The ground here always seems to be wet 2 feet down, even in the driest summers...sump pits always seem to contain water no matter what. Dry wells are a miserable failure.

    The first year in this house was plagued by a nasty musty smell emanating from the basement. Someone had, at some point, glued down shag carpet and paneled the walls. No insulation or vapor barrier, no outside waterproofing (at least beyond what they used in 1914). We got 9" of rain in 12 hours in June 2012, and we were lucky in our neighborhood. We had only a few small trickles from the corners of the foundation. Many other's had sewage shooting out of floor drains, all that good stuff.

    That was the point at which I gutted the basement and found mold covering all the walls under the panelling, the carpet was sodden, it was GROSS. a year of weekends on and off later, and it's much more pleasant. The dry lock made a massive difference, as did running 2 dehumidifiers nonstop for a month to dry out the floor joists above. My last step will be an epoxy coating on the basement floor, once I work up the energy to grind off the red paint that was under the carpet.

    Now in the summer, I average 50% RH with the dehumidifier running a 30 minute on, 30-40 minute off cycle, and about 25% all winter (it gets very dry and cold here). Before the dehumidifier could never keep up...so it had to have helped. And no one is afraid of the basement anymore!
    Ford Master Technician, "Tinkerer of Terror"
    Police & Fire Equipment Lead Mechanic, NW WI
    Lover of Old Homes & Gravity Hot Water Systems
  • JUGHNEJUGHNE Member Posts: 6,791
    Larry, the reason for the question about AC is do you think the negative drawn under the slab would pull the drier AC air down thru the concrete and help dry out the slab?

    The air being exhausted by the radon fan must come in somewhere but with the AC it is conditioned and pulled thru the slab.

    And in the wintertime that air introduced by the radon exhaust fan would be pulling in outside cold dry air which would dry out the house even more??

    Just a WAG theory, what do you think?
  • Larry (from OSHA)Larry (from OSHA) Member Posts: 688
    Well, I'm pretty sure that conditioned air is heading down the steps to the basement and in the wintertime, outside infiltration is turning the house into a winter desert. In my case, the radon system is most likely taking a lot of air from the floor edge where the draintile meets the walls. There should be an airtight seal there but there isn't. Still took the radon levels from about 20 to less than 1, so that's good. Just like anything else, any time you change something, there will be an unexpected reaction. Working on infiltration is on my list of projects.

    I hope all this banter gives Carl something helpful to deal with his friends situation.
  • JUGHNEJUGHNE Member Posts: 6,791
    edited August 2015
    I believe that this Wall was intended to be a "banter board". Because of this posting I'm now considering adding the radon exhaust fan to my sump pit. Have the complete drain tile set up and vapor barrier under basement slab. But have high humidity in entire house mostly year around. Basement always smells like a basement even with AC. (have supplies and returns in bsmt). But only need AC 4 weeks per season. Larry, thanks for the idea. :)
  • ChrisJChrisJ Member Posts: 10,857
    I have a basement with 50% dirt floor as well as multiple crawlspaces connected that all have dirt floors and everything is stone foundation. Without a 50pint per day dehumidifier the RH was around 80%. With it runing 24\7 from the spring to fall I can maintain 40%. It costs around $40 a month, but it keeps the areas fairly dry and I can use the space. The other downside is it ends up around 80F down there. The dehumidifier is piped into a LittleGiant condensate pump which pumps the water outside away from the house.

    I also have gutters and lead the water away from the house. Of course, the ground outside is pitched away from the house and the water table is fairly low.

    During the winter, the RH drops down to around 30% all on it's own so the dehumidifier just stops running. Not sure if this is due to the ground drying up, or if it's because everything is so drafty or both.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • JUGHNEJUGHNE Member Posts: 6,791
    Would it be safe to say that in the winter time your boiler is venting the basement with combustion air drawn in thru wherever it comes? Also of course winter air is usually drier.

    Out here newer all electric homes usually have high humidity in the winter because lack of the chimney in the house.
  • ZmanZman Member Posts: 5,736
    Thanks again for the great feedback.
    I will absolutely share the data and the final resolution.
    At this point I think the info I get from that data loggers, IR cam and plastic sheet test will get me pointed in the right direction.
    It is amazing how many of you have had similar problems and how the construction industry keeps making the same mistakes.
    As a friend of mine likes to say, "it's like a dog that won't stop crapping on the rug..."
    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    SWEIBobbyBoy
  • ChrisJChrisJ Member Posts: 10,857
    Zman said:

    Thanks again for the great feedback.
    I will absolutely share the data and the final resolution.
    At this point I think the info I get from that data loggers, IR cam and plastic sheet test will get me pointed in the right direction.
    It is amazing how many of you have had similar problems and how the construction industry keeps making the same mistakes.
    As a friend of mine likes to say, "it's like a dog that won't stop crapping on the rug..."
    Carl

    I'll cut the guys that built my house some slack. I don't think they knew much about that in the 1860s. :p
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    Canucker
  • Bob Bona_4Bob Bona_4 Member Posts: 2,083
    The hacks that "built" the additions on my old house in the 80s certainly should have known better :)
    ChrisJCanuckerSWEIZman
  • JUGHNEJUGHNE Member Posts: 6,791
    And there is more FWIW.
    We have a high school boy's locker room in the basement of the gym. No AC in building. It would burn your eyes just to enter the room. They would never wash their practice football uniform, must be a throwback to primal Neanderthal aroma defense from the enemy. Dirty sock odor on steroids!

    So for a major remodel a Honeywell DR90 was installed, 6" fresh air duct added that is always open. This beast can do up to 90pints/day, has good air filter, moves 220 CFM and draws 6.3 amps @ 120 VAC. Duct work was installed to hit all the areas.

    It really worked, got good compliments from alumni who said the place smelled bad 30 years ago. Visiting teams have noticed and may lean towards the same system.

    May be over kill for a house but worked so well that the board did the same thing for the girls locker room next year....(we know that girls never smell :| ) It does add heat to the area as any dehum unit does.
Sign In or Register to comment.

Welcome

It looks like you're new here. If you want to get involved, click one of these buttons!