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Moved to a new house – evidence of moisture problems. What are my options?

Ulfhednar | Posted in Mechanicals on

Hey folks (hope I posted this to the correct area)!

I recently moved to a 1970s ranch style home in northeastern Wisconsin (by the big lake). Our summer and shoulder seasons are quite humid, and of course we have the infamous cold winters. The house has electric baseboard heat and a recently installed ERV system. The place was used as a vacation home with occupants only around in the summer months. Some of the baseboard thermostats were busted and running too hot. For A/C, it has a few sleeve/wall air conditioners.

As for moisture problems.. it’s December and I’m still getting condensation on many of the windows. The sills are a bit rough & stained looking, as this has probably been going on (and neglected) for some time. The kitchen & bathroom cabinets smell musty and some of the shelves are bowed. I dropped a standalone Dehu in the (sealed) crawlsplace, and it read 76% !

Now, from what I understand, ERVs can move some moisture – but it’s only as useful as the outside humidity it’s exchanging with. Since our shoulder seasons are humid, it’s not going to do that great of a job. In this environment, I imagine it’s only benefit is bringing in fresh air.

So now that you have some background, that brings me to my question. In a house battling high moisture with a sealed crawlspace and no ductwork (other than the ERV)… what are my options? Natural gas is not available in this area, so most people use propane or electric. I am also open to discussion on the method of heating. I like that electric can be zoned per room – but I know it’s an expensive source of energy.

Thanks in advance!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Sean,
    The first step is to identify the source of the moisture, and to do your best to reduce moisture entry at the source. The chief suspect is the crawl space.

    Is there polyethylene on the crawl space floor? More information here: Building an Unvented Crawl Space.

  2. Ulfhednar | | #2

    The crawlspace is poured concrete with what I believe is a spray foam on the walls & floor. The sump well has always been dry after a hard rain, despite poor gutter systems around the house. I was hoping it was due to the strong grade that is around the house - but part of me also worries that the drain tiles aren't working and the moisture is just going into the concrete. Not really sure about that.

    I attached a pic of what the crawlspace looks like.

    Edit: I should also note that there is nothing on the floor joists. Perhaps the concrete and insulation on the floors/walls is sufficient?

    Thanks!

  3. BAGH | | #3

    Diagnostics first. Figure out where the moisture is coming from. Moisture moves from wet to dry. It wants to even out in a volume and condense against cold surfaces at its dew point. Where is that 76% coming from in the crawl? If the air outside air is dry, the moisture might be coming from inside. Have you done a blower door and duct test to see how tight or leaky the house is? Is water, snow, melt puddling against the house and leaking into the crawl?

    Try putting a large plastic sheet down on the floor of the crawl to see if moisture accumulates underneath. Maybe they left out the vapor barrier (because who could see if they saved money on vapor barrier once the (concrete?) is poured).

    Diagnostics will tell us the problem so we don't waste money doing random stuff.

  4. GBA Editor
    Martin Holladay | | #4

    Sean,
    Don is right. Test the concrete floor by taping down a square of polyethylene. After 24 hours, see if there is any visible moisture under the polyethylene.

  5. GBA Editor
    Martin Holladay | | #5

    Sean,
    Once you have figured out where all of the moisture is coming from, and you've taken steps to reduce the rate at which moisture is entering your home (or perhaps, once you've taken steps to stop generating moisture inside your thermal envelope), you'll want to keep everything stable indoors.

    The most important thing to do to keep things stable (again, assuming you've addressed your moisture sources) is to heat the home during the winter and cool the home during the summer.

    If you are installing a ventilation system to reduce your indoor humidity levels, an ERV isn't necessarily a good choice. During the winter, and HRV (or an ordinary bathroom exhaust fan) will do a better job of lowering indoor humidity than an ERV.

    During the summer, an ERV may make sense -- but only if you are operating an air conditioner. In most climates, operating an ERV during the summer will add moisture to your home -- but an ERV will be less bad than an HRV. (Again, we're talking about summer conditions, not winter conditions.)

    For more information on ERVs, see HRV or ERV?

  6. Dana1 | | #6

    ERVs aren't the best choice for a NE-WI climate since they're more easily frost-damaged than HRVs, but the moisture exchange rate isn't high enough to make a huge difference when the outdoor air is arctic-dry as it is much of the winter in that area. With a high enough ventilation rate it should be able to purge a lot of moisture.

    That climate is not very humid in absolute terms. The outdoor dew point averages in say Green Bay are only north of 60F during July & August, not during the shoulder seasons. So even an ERV should be able to dehumidify the place quite well, given a reasonable ventilation rate.

    Low performance windows will always have higher condensation potential than high-performance windows- what do you have?

    What is the temperature in the crawlspace? It's important to know the temperature to which the humidity is relative. An RH of 76% isn't a big deal if it's 45F down there, but it is if it's 65F. Are the crawlspace walls insulated?

  7. davidmeiland | | #7

    What do you know about how the crawl space was encapsulated? Was the slab done at the same time as the foamed walls, or is the slab older or even original? I would suspect no vapor barrier under the slab until proven otherwise. If someone came in and foamed the walls to try to combat a moisture problem before the house was sold, but the slab has no VB and that was not addressed, then they haven't done you any favors.

    Covering part of the slab as a test is a good idea, but you can often just chip out a little piece and see what's underneath--those slabs are often fairly thin and have cracks to exploit. You could also just roll out 6-mil poly over the entire thing and see if that drops the humidity significantly, both in the crawl and in the living space. There appears to be almost nothing in your way. Cut the poly around the water heater and support posts, and overlap the pieces. Don't worry about some minor gaps, and don't worry about the edges, just get the slab 99% covered. Use a thermo-hygrometer with a dewpoint reading and see if the dewpoint drops significantly if you cover the slab. It might take a little while, because if moisture levels are high it's stored in the wood and concrete materials and not just in the air.

    The age of the house also suggests the possibility that there is no foundation drainage, or it has failed. Do you have well-draining soil, or possibly clay?

    You could also air-seal the floor from inside the crawl space. Very easy to do in such an open space and without fiberglass. Any evidence that there was even fiberglass in the joist bays?

    The question was asked above about the windows. Do you have aluminum windows with insulated glass and marginal weatherstripping? That's very common around here in a house of that age and type. Condensation is very hard to prevent, because the aluminum is very cold and the operable sash leak cold air in around the edges, making things even colder. Staining of the woodwork suggests it has been going on for a while.

    Not sure what to say about heating fuel. Propane and electric are the choices here too, and propane seems cheap at the moment, but electric is even cheaper for us. What are the rates you pay?

    edit to add, what's that big pipe going down through the crawl space floor?

  8. Ulfhednar | | #8

    To answer the window question, they're older dual-pane in a wood encasement. From what I've seen so far, the operable windows get far more condensation than the fixed windows. I just took pics and attached them; the windows pictured are part of the same series, directly next to each other. On the other side of that same room are some newer looking dual-pane windows (thicker gap) in a bay window.... I have never seen condensation or signs of it on these windows. Unfortunately, 90% of the windows in the house are like the ones pictured. This is occurring in bedrooms, living areas, etc.

    As for the crawlspace, I can certainly do the sheet test on the floor. It's always pretty warm down there - close to living space temps. Mind you, I've only been in the house for < 2 months. Unfortunately, the sellers inherited the property and there didn't seem to be much info to extract from them... so I know nothing about the build timeline. I don't know what that pipe is coming from the ground, but it's capped. So aside from the possibility of missing a vapor barrier, does the lack of water in the sump basin raise any flags? The basin has a lot of rocks in it and I can only see one inlet. There must be some kind of drain system because I can see a perforated drain pipe running along the foundation on the inside, where there is a hole in the ground where the water main enters. I'll take more pics tomorrow of the crawlspace.

    The ERV is currently running at 40% time. I don't know if this matters from a design standpoint, but the indoor intake and exhaust registers are very close to each other (opposing end of a hallway) - which are in the far end of the house.. so not very central.

    Edit: I also attached an image of the backside of the house where there isn't a gutter run. I was hoping there was a trench drain installed there, but it looks like the runoff has just channeled a groove. It's hard to see in the pic, but there is a slight sloping grade away from the house and then just outside of the frame is a dramatic drop. The water pools up here during a moderate-heavy rain, and then slowly drains into the soil. As you can see, it's generally a wet and sunless area. Much of the surrounding environment is mossy with moss on trees, rocks, etc. And plenty of mushrooms all over. This region tends to have a relatively thin layer of soil on dolomite bedrock, and there are a lot of small boulders and bluffs around.

    Thanks for all of your responses, much appreciated!

  9. GBA Editor
    Martin Holladay | | #9

    Sean,
    You should continue your investigations. Lack of gutters and bad grading can certainly direct rain water toward your foundation, which may be making your crawl space damp. We can't diagnose this over the Internet -- you're going to have to keep investigating until you find the source of the moisture.

  10. Ulfhednar | | #10

    Will do. I was just looking to stir up some ideas from people more experienced than myself. It looks like there are a number of things I can try and remedies to put into action. Thanks for your help!

  11. GBA Editor
    Martin Holladay | | #11

    Sean,
    Here is a link to an article on wet basements. Some (but not all) of the advice in this article also applies to crawl spaces: Fixing a Wet Basement.

  12. Dana1 | | #12

    1970s vintage wood sashed clear glass double panes ran about U0.6-ish. A tight low-E exterior storm window will boost that performace by quite a bit, dropping the U-factor into the low 3s, which will reduce the condensation potential by quite a bit. For a house heated with electric baseboards the "payback" of low-E storms will be under 5 years, more than a decade sooner than a code-min replacement window of comparable performance, and faster than cheaper clear-glass storm windows. The Larson low-E storms sold through box stores are pretty good if you go with something better than the bottom-of-the-line series, but there are others. When shopping for a storm window, try to get specifications on air tightness, and don't settle for clear glass.

    If it's 75%RH @ 65F upstairs it's a problem. If it's only in the crawl space it could be a symptom of low air exchange volumes with the upper levels, but you almost certainly have a bulk-water moisture issue somewhere. It could be wet soil under the slab from the apparent surface drainage problem (that can be fixed), a high water table, or even a chronic plumbing leak.

  13. wjrobinson | | #13

    1-Looking at the pic for the crawlspace, it looks darn good, looks dry, the joists look perfect. Of course I would rather see all in person.

    I would make sure upstairs living area is at the right moisture levels, use bath fans, reduce plants if have lots of plants you water, use outside exhausting stove fans.

    The musty smell, someplace is moist... look for plumbing issues, venting issues, gutter issues, etc... get some contractors to come by... "free estimates" which it would be nice if you hired one that made sense with his findings...

    The windows idea of Dana's is good... improve your windows, replace or add storms to fixed units only IMO... IF replacing get triple pane possibly...

    My own home has old 1980's windows... they rarely have moisture but depends on number of people and heat and showers and cooking and outside weather, etc... I live with some staining... By the way... I now use water based poly standard Minwax products in the blue can and love the product. On table tops, no water marks, handles being wet like a champ! I will be using it as I redo my window sill areas. Start with gloss, then switch to satin, sand between coats, 3 coats is nice, 6 on table tops finished with 1200 sanding sponge with the grain. Yes last coat is sanded.

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