Poindexter versus damp subarctic crawlspace

[Poindexter]

This should be interesting, at least for some.

This will be, partly, a notebook or workbook for me to be keeping notes in.

The short version is the wife and I raised four kids in this five bedroom house. The kids are out, it is just us and the cat. We would like to sell and buy a smaller home on a bigger lot. We don't need five bedrooms.

Its 1200sqft lower level, 1200sqft upper level. The garage half of the ground level is on a poured pad, the rest of the lower level is over a crawlspace.

I worked the walls over top to bottom sealing up air leaks. I have a pretty tight envelope.

The wife and I pretty much live upstairs with the woodstove, so we started our pre-sale refit downstairs.

We scraped the popcorn off the ceiling. We took up the carpet. I replaced about 1/3 of the subfloor downstairs- PO used one of the bedrooms as a dog kennel.. No visible mold in the crawlspace. We sealed all the drywall with BIN primer. We painted. We put in new Marmoleum. We replaced a couple windows with new stuff from Northerm. The new windows are bigger. While the drywall had to be cut back for framing we took out the insulation in the stud spaces under the windows - it was all mildewy - sprayed the stud cavities with Concrobium, blah blah, sealed the vapor barrier back together with some incredibly expensive tape, just going nuts.

I am coming at this from the point of view that if the house doesn't sell I don't want to be re-doing any of this except maybe repainting the walls for at least 40 years.

I don't know how many dogs we have had, we still have a cat, there was a ferret for a little while, and kids by the busload. We tried to be the house our kids brought their friends to, mostly so we could keep an eye on who the kids were hanging out with. Parents of were always welcome. For a while there with all four kids home I was serving supper to 10 or 12 people 6 nights a week, but the kids turned out good.

What I am getting at is the carpet smelled pretty bad.

Now that the downstairs looks like something you might see on television, we got a faint musty odor, seasonally, when the dirt outdoors is wet.

user NateB pinted me at a very helpful video from Minnesota in the splinter thread I had going a bit ago.

Video here:

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I also poked around on engineering toolbox a bit to confirm my suspicions. BRB.

 

[Poindexter]

Again, my thanks to @NateB . The Cold Climate Housing Research Center in Fairbanks doesn't have anything on their website about crawlspaces. Appreciate the heads up. Minnesota, it is just like Alaska except they have wind and we have January.

Showed the first 3 minutes to the wife, she agrees the guy seems to know his stuff.

Right now I have single layer vapor barrier on dirt in the floor of the crawlspace, bare concrete for the walls, and closed cell taped into the rim joist cavities.

My concern is the guy in the video talks about putting a capillary barrier between the footer and the bare ground below as the biggest challenge. I am willing to pull my rim joist insulation and put some fin pipe on the hot water baseboard runs in the crawl space. I am willing to turn up the oil thermostat for the lower level. I am willing to excavate the foundation and put up exterior vapor barrier on the crawlspace walls.

I am willing to grade my lot, likely requiring a sump and pump outdoors near the street. Pump would only need to run in April and mid August to mid September, but I have a 10 foot utility easement between the house and curb. Looking for a transit and stadia to rent.

I cannot put a vapor barrier under the existing footer. I have no known way to measure how much of the water in my poured wall is mass movement from horizontally adjacent soil and how much is capillary movement from the ground below.

I don't want to give up a bedroom, but I could put a pellet burner in downstairs with a OAK pulling from the crawlspace.

There is some profanity involved here.

 

[Poindexter]

Do I have water coming onto my crawlspace? Intuitively, yes.

I poked around a bit at engineering toolbox dot com. Rather a lot actually.

Knowing my crawlspace is roughly 20 feet wide x 30 feet deep by 4 feet deep, I come up with a volume of 2400 cuft. This is inexact, but defensible.

I found a table somewhere on engineering toolbox I can't link to right now that gives the weight of one cuft of dry air as 0.08 pounds. I got 2400 of those, so 192 pounds of dry air in my crawlspace.

There is a handy table here:

https://www.engineeringtoolbox.com/water-vapor-air-d_854.html , the third one down.

I started at 47%RH, ended at 40% RH, temp was stable at +64dF, pressure was stable at 29.9 inches Hg. recovered 6.5 pints of condensate.

Looking at the table, if I had started at 50% RH and the temp had been stable at 60dF, recovering 0.3 pints of condensate should have been enough to drop the RH in my crawlspace from 47% to 40%, but I recovered 6.5 pints.

So I got water coming in, lots of it.

Time to watch some not entertaining video with the wife.

 

[sportbikerider78]

The biggest advice I have is nothing you haven't heard before, start outside. Make sure the grading is correct and all of the rainwater has a very easy escape route away from your home.

 

[lml999]

Is your crawl space insulated? If so, would your situation be better or worse if you insulated the crawl space ceiling and provided good ventilation for the crawl space itself, at least during the wet months?

How wet is the ground during the spring? As sportbikerider78 mentioned, you have to ensure that rainwater is traveling away from the house. But...if the ground underneath your house is moisture laden even without rain, you're fighting a different battle...

What is the experience of your neighbors?

 

[Highbeam]

All of this to reduce or eliminate a musty smell in a first level space above the crawl? How could this moisture or smell move into your first level space? How humid is that first level space?

Unless you have standing water under your crawlspace floor vapor barrier I suspect you actually just need to dehumidify the first floor living space where the smell is. Get that dehumidifier up into the living area.

Ventilated crawlspaces are not the same as basements.

 

[Poindexter]

The biggest advice I have is nothing you haven't heard before, start outside. Make sure the grading is correct and all of the rainwater has a very easy escape route away from your home.

Both good points.

I rerouted both down spouts years ago. One drains to the asphalt driveway to the street and away. The other exits 14 feet away from the house into a rain barrel. When the rain barrel overflows the gravity path is diagonally across my side lawn, under my neighbor's truck and then down his driveway to the street and away.

My grading, not so much. I don't own a stadia or transit, but learned how to use them at archaeology field school. My best guess, without the proper tool to measure, is the junction between the top of my foundation and bottom face of the rim joist is something like 2-4 inches above the upper lip of the curb at the street.

One option would be to run drain tile under my neighbor's driveway, I could drain three sides of the house to it and he is a pretty cool dude. Otherwise, the slope for what I can grade and still gravity drain over the curb onto the street is going to be something 1 to 2 inches of drop in 15 to feet. Or I could put in a cistern of some kind and pump it out a couple times annually.

 

[Poindexter]

Is your crawl space insulated?

No. The four foot vertical air cushion between the floor joists and floor of the crawl space provide some R value, but the poured walls the rim joists sit on are not insulated.

If so, would your situation be better or worse if you insulated the crawl space ceiling and provided good ventilation for the crawl space itself, at least during the wet months?

Possibly.

One problem is snow load. Under load I have enough weight up there that the floor joists on the lower level bow, arch up in the middle. Insensible to the naked eye, it is a slow process. We were wanting to put in hardwood flooring down there. In the one room a PO had used as a dog kennel, the one where I replaced the subflooring, I measured flatness real real careful after the new subfloor was in before freeze up, and happened to measure again, after freeze up, just to double check something or other. One eighth here, quarter inch there, three eighths a few places I got a big pile of NIB TG hickory in the garage still. Less flexing upstairs, I have checked flatness on the bare subfloor in the master bedroom three times now.

One other option is the ground freezing under the posts under the beams that span the crawlspace and that process making the subfloor bow up. Either way, it's moving.

What I am getting at is sealing the lower level from the crawlspace would be pretty easy, signing up to maintain an airtight seal is madness.

Another problem with that idea is water and sewer come vertically up into the crawlspace, buried I think eight feet and insulated pipe for both. If I don't keep some heat in the crawlspace my incoming water pipe might freeze.

How wet is the ground during the spring?

Pretty wet.

As sportbikerider78 mentioned, you have to ensure that rainwater is traveling away from the house. But...if the ground underneath your house is moisture laden even without rain, you're fighting a different battle...

Downspouting I covered, grading I covered. I need to get busy with a transit.

The other question, unasked, is how wet is my ground in the autumn rainy season, like now?

This seems like an average year to me for lawn fungus. These are both > 15 feet away from the house, didn't have to look too hard for them, have plenty of types and plenty of population.

What is the experience of your neighbors?

Macro scale, whole subdivision, out of 40 or so homes my lot is second or third highest elevation in the entire subdivision. My next door neighbor the the west has the highest lot in the neighborhood, his snow melt flows both ways in the curbing in front of his home, and across the street to the gutter on the other side, where it flows both ways down the curb/gutter over there too. I am just down hill from him, and everyone else I share a curb with is downhill from me. But my house seems to have built in a pre-existing pocket or hollow near the crest of the rise. Another 6" of poured 40 years ago would give me a lot more flexibility today.


Thanks for the questions.

 

[Poindexter]

All of this to reduce or eliminate a musty smell in a first level space above the crawl?

Yes. I can smell it, faintly when the crawl is at 47% RH. At 40% RH, I can't smell it at all. It is enough to bother my wife, even at 40% RH. I am the one that is pollen sensitive, she has the mold sensitivity.

How could this moisture or smell move into your first level space?

I think at this time it is a diffusion process. There is lots and lots of water vapor available in the poured concrete wall.

I just finished another test cycle on the dehumidifier actually a couple hours ago. I set it to maintain 40% RH in the crawl space, so intermittent / auto operation, but recovered 4.3 pints of condensate in 29 hours, about 1/4 kitchen measuring cup per hour.

When I started the dehumidifier the upstairs with the wood stove running was 84dF and 38% RH. Down stairs living space was 66dF and 47% RH, crawl was 64df and 47% RH.

I think water vapor is moving from wet - crawlspace wall - to dry - upper level heated by woodstove. And bringing some musty/ mildew smell with it.

How humid is that first level space?

I haven't seriously instrumented the lower level before, it has always been "livable". I only have one measurement recorded as above.

Unless you have standing water under your crawlspace floor vapor barrier I suspect you actually just need to dehumidify the first floor living space where the smell is. Get that dehumidifier up into the living area.

Two problems.

One. We just went bananas upgrading the lower living space level looking for highest possible resale value if we do sell, or best possible indoor air quality if we decide to not sell. We got a really nice trip to Europe tied up in that 600sqft.

Two, I found the mildew just a couple hours ago.

Wen I pulled the rigid foam out of one of the joist spaces on my lunch break, I found wadded fiberglass batt behind it. I found mildew in the batt. I concrobiumed the heck out of the clean appearing wood. I have sequestered the offending batt in a sealed plastic bag. When the wife gets home we will poke a wee hole in the plastic bag to see if that is the mildew smell she smells.

I suspect I will be pulling out all that hard foam and wadded batt, concrobium on all exposed wood in the crawlspace, likely twice, and then see where we are. I suspect we will end up excavating next summer to apply a vapor membrane to the outside of the foundation wall to limit horizontal water transport, and then external insulation up the outside to above the rim joist.

I do not see a way to get a capillary break between the footer and bare ground, or between the rim joist and foundation top. Or between the footer and bottom of foundation wall for that matter, so I will likely be stuck with capillary water movement from under the footer to the rim joist no matter what I do.

 

[Highbeam]

If it were me I would simply dry out the living space to the 40% and see how that smells. I don't think your crawlspace RH has anything to do with it.

 

[Poindexter]

I found all of these within 24 inches of the curb at the street in something like 90 seconds.



My ground is seasonally wet.

 

[Poindexter]

I have three of the rim joist cavities open now. Worst batt and worst joist space to date:

 

[OT_Ducati]

I have three of the rim joist cavities open now. Worst batt and worst joist space to date:

View attachment 229387 View attachment 229386

Looks like the rigid foam is trapping moisture.

 

[blades]

Pull all foam and fiberglass at rim hit all with bleach let dry re-install foam pieces using spray foam seal edges also foam board on top of concrete footing -again seal with spray foam That is about all you can do there. out side you already covered the remediation in a previous post. I would add an over flow drain to that water barrel going out to street as that overflow ain't helping

 

[OT_Ducati]

Did you watch the video you posted yet?
Doe's it tell about how the house has negative pressure in cold weather?
If you seal the home you need to put positive pressure in the home during the heating season.
That being said you Know now your pulling cold air into the home everywhere it can come in.
Then where it enters it condensates, Positive air pressure during the heating season will help stop the condensate.
Air exchanger with outside air.

 

[Poindexter]

Looks like the rigid foam is trapping moisture.

I agree.

And I smelled the cat urine smell I have been hearing about reading up on damp crawl spaces.

It took me about two hours to pull all the rigid foam, pull all the batts and bag all the batts. Somewhere along the way I started getting occasional whiffs of cat urine, but it always seemed like it was behind me.

When I was done and pulled my work shirt off - pee-eww. Whatever in there air that didn't have an odor dry, but when it landed on the back part of my workshirt damp with sweat, ooh lordy. Same airflow over the dry parts of the same shirt, no odor.

 

[Poindexter]

Pull all foam and fiberglass at rim hit all with bleach let dry re-install foam pieces using spray foam seal edges also foam board on top of concrete footing -again seal with spray foam That is about all you can do there. out side you already covered the remediation in a previous post.

I could do that to save a few bucks on my heating bill this winter, but i agree with overtime ducati that the rigid foam was acting as a vapor barrier and trapping moisture in the rim joist cavities. So I could put rigid foam back up and save a few bucks, - or I can leave it out and get my rim joist and associated cavities dry.

The current plan is to get the rim joist dry, excavate next spring and install exterior vapor barrier.

I would add an over flow drain to that water barrel going out to street as that overflow ain't helping

Our tentative plan at this time is to excavate the foundation next spring, install drain tile next to the footer, external vapor barrier and external insulation up to the top of the rim joist, gravity feed a cistern in the front yard with the drain tile, and pump the cistern out regularly.

While we still have the rented Tonkas on the lot I will drive my neighbors bananas grading the surface after the backfill is done.

A side item we can accomplish is to move our below ground fuel tank forward about four feet, we currently have the stand pipe in a side yard with the fill pipe in the back yard and no good way to get a dog and have fuel delivered if the dog is out. It is just another example of someone having gotten the job down without thinking through the consequences of the shortcut being taken.

 

[Poindexter]

Did you watch the video you posted yet?
Doe's it tell about how the house has negative pressure in cold weather?
If you seal the home you need to put positive pressure in the home during the heating season.
That being said you Know now your pulling cold air into the home everywhere it can come in.
Then where it enters it condensates, Positive air pressure during the heating season will help stop the condensate.
Air exchanger with outside air.

We have watched it a few times each, twice all the way through together.

The first 3:37, maybe 3:45, where he is telling you what he is going to tell you was enough to hook us. Minnesota Man, Pat Huelman might as well be talking about my house. It was kinda chilling, he understands my challenges very well.

Positive pressure would be at least partly effective. All I have installed for the Ventilation part of HVAC is a courtesy fan in each of the two bathrooms. That's it. I got hot water baseboard heat, a wood stove, a couple fans and opable windows.

We have looked at adding HRV to this house twice, we are going to start with the exterior vapor barrier and insulation on the foundation walls. And grading. Woot, I hope I can rent some diesel stuff. I have time to grow mullet before spring melt.

 

[Poindexter]

I have been spending some time on building science dot com. Unlike many online resources for damp crawlspaces, they are't trying to sell me anything.

I did excavate one exterior corner down to the footer. I have a one inch layer of spray foam on the outside of the foundation wall all the way down to the footer, tentatively identified as UFFI. I spent some time trying to figure out if it was open or closed cell polyurethane foam. Finally searched on 1978 spray foam insulation (year of build), I am pretty sure it's UFFI. R value about 4.7 per inch, but jack doodle for water barrier.

I have all winter to read up on that one. Leave it up and put vapor barrier over it, or bite the bullet and scrape it down to bare concrete.

Inside the crawl space the dehumidifier finally shut down. We haven't had any rain in several days, I have been maintaining 40%RH in the crawlspace with ambients in the low 60sdF for five days. I had a psychrometric table open on my phone when I went down there with my moisture meter. EMC (equillibrium moisture content) of wood at 65dF/ 40% RH should be 8-9 %. I found 8-9 percent near the dehumidifier, and son of a gun if the sill plate doesn't come in the same for me today, even in the historically damp corners. Yay!!

We have all the windows open now and a few fans running. Tonight we will likely seal up the house, light the wood stove and see what we smell.

I have two chores left to try to get knocked out before freeze up.

1) I am going to put a new layer of plastic on the floor of the crawlspace. The existing layer has peeled back from the foundation in a few spots and has some pinholes in a few spots. I am planning to leave the existing layer down, clean debris off the surface and lay the new right on the old rather than drag the old through the house and out.

2) Going for the red neck look this winter I am going to tack blue foam insulation to the outside of the house to cover my otherwise uninsulated rim joist cavity. I am thinking two layers of 1" thick foam with staggered joints. It will get snow covered pretty quick.

I do have a 4 sensor set on the way from amazon for temp/ humidity. This one:

https://www.amazon.com/dp/B01EI0MS3Y/?tag=hearthamazon-20

The reviews are kinda not bad, but I need data. I don't want my incoming water main to freeze, I also want to keep the crawl space, I dunno 5-10 degrees F above dew point. With temp and RH I can calculate dew point or look it up on a table.

I am thinking pretty hard about having some fin pipe added to the hot water baseboard runs in the crawlspace. I have never "needed" them before in the sense the water main hasn't frozen yet without fin pipe down there.

Also located the foundation / sill plate junction all around the outside perimeter. Doesn't look as bad as I feared, I think max my sill plate is maybe 12 inches above the top of the curb at the street.

 

[Poindexter]

And my DEEPEST sympathies for anyone taking this on in a more varied climate. Jeez-Louise, anything in roughly Illinois, Indiana, Ohio where it gets plenty cold in the winter AND sticky nasty hot and humid in the summer, conflicting needs, bigger challenge than I have. Good luck.

It does get hot and humid here in the summer - for about two weeks. I can pretty much coast my crawlspace through that and just set mine up for cold weather.

 

[Dantheman300z]

As you can see my location, I am having an interesting inward battle with myself over my crawlspace. I am enjoying someone else's battle being laid out and extensively thought through.

 

[Poindexter]

My preliminary survey is complete.

My fundamental problem is there is no capillary break under the footer, no capillary break between footer and foundation, and no capillary break between the top of the foundation and the sill plate. No matter what else I do, I am going to have some water moving from under the footer up into the sill plate by capillary action during the spring melt and during the autumn rains. And I got a layer of fiberglass batt in that area I cannot keep dry that already has black crud on it.

Stuff I can do is

1.replace (or cover) the UFFI on the exterior foundation with something vapor/water impermeable and take the exterior foundation R value back up to 4.7 or better.

2. Fix the gaps and holes in the existing vapor barrier on the crawlspace floor.

3. Run my new dehumidifier in the crawlspace semi-annually.

4. Install drain tile at the footer and drain it to a sump inside the utility easement, pump the sump out seasonally.

5. Re-grade my lot with the sill plate 4" above grade with 1 inch in 6 feet slope around the house out to 12 feet, 2" drop total and a reasonable prayer of still draining high volume surface runoff over the curb and out to the street.

Stuff I need to research over the winter:

Remove or cover UFFI?
Adhesive for plastic to concrete in wet environs (crawl floor)? So far it is temco black death acoustical sealant, or poured concrete.
Spray closed cell, plastic sheeting or hard foam sheets for exterior foundation vapor barrier?
Find a sub contractor to dig, back fill and grade
In what window can I apply fresh black death and run crawl fans to keep organic solvent vapors out of the house without adding water to the crawl? Likely late May and early to mid June.
How far up the exterior should I run exterior vapor barrier and insulation? relative to what?

 

[Poindexter]

@Dantheman300z , one thing about my crawl is the floor is kinda V shaped, with a deep center section. The incoming water main is up on the slope of the V, so the coldest air in the crawl will tend to drift downward away from the water main towards the deep part of the crawl floor. Given the other workmanship down there it might be an accident.

 

[Highbeam]

Poindexter motivated me to buy another accurate humidity meter (hygrometer?) and check out the home. We are well sealed above a crawlspace that never has standing water. My indoor humidity is high, 60%, and in the winter is often super low bottoming out the gauge at 16%. We have no mold, smells are subjective and really you get used to them but we smell nothing, the only thing I notice is that when I install doors in the winter that the gaps shrink in the summer.

Considering a dehumidifier to drop the summertime humidity to 40-45%. Dust mites, bugs, door gaps, smells, etc.

 

[Poindexter]

Found some grey/black slime growing in the condensate tank this morning. Rinsed that out with with some white vinegar and prefilled the tank with a pint of 50:50 vinegar/water poured in through the condensate path.

I haven't found a desirable adhesive for attaching plastic vapor barrier to poured concrete. I spent a bunch of time at Lowes-Depot reading labels on adhesives. The short version, my findings, only the most expensive glues are rated for plastic to concrete, and none of them are rated for damp environments.

I do have another local store still stocking tremco "black death" acoustic sealant. Seems like my best current bet, but will need to wait until spring so i can pull the worst of the vapor outgassed from that out of the crawlspace through a ventilation fan that doesn't exist yet without stinking up the house so bad.

Interim, I did crawl the perimeter where the floor vapor barrier meets the poured wall and pushed the plastic back onto the glue line.

Hygrometer set due Monday. I do have one contractor at my church who is willing to excavate foundations and grade lots as part of his landscaping business. I hope to speak to him tomorrow.

For now I am maintaining RH in the crawl at <40%, at 60-65dF, and pulling 50-60 pints out of the dehumidifier weekly. Dehumidifier should settle down once the ground freezes. I know I will be running the dehumidifier again from when the ground thaws until I can get vapor impermeable barrier on the exterior foundation wall.

After that I will still have capillary transport from under the footer into the sill plate. Planning to place drain tile at the exterior perimeter to minimize that as much as possible. Without lifting the house off the foundation to place a capillary break, that is all I can do to keep the sill plate dry.

My rim joist is dry, except for what gets carried through the sill plate. Planned interventions to keep the sill plate dry:

1. Grade lot so sill plate is 4" above grade with 2" in 12' slope away from house on all sides, gravity drain surface water to street.
2. Water impermeable barrier on exterior foundation wall to top of rim joist, with insulation.
3. Drain tile at footer, full circumference, gravity drain to sump adjacent to utility easement.
4. New vapor barrier on floor of crawlspace. I think I am going to put the vapor barrier as low as possible on the poured wall. I know there is water in that concrete. If I can get any of it out the side wall without carrying it through the sill plate first I think I would rather do that.
5. Dehumidifier remains on standby.
6. Possible seasonal ventilation fan. I am not opposed, but I think the number of days i can operate one without pumping net water into the crawlspace is probably very low.