1st own house - crawl space woes

[primergy]

Looking for some options & advice on redoing crawlspace insulation.
Please excuse m English when it comes to technical terms, it's not my first language.

This is our first home, just got done with a bathroom reno including rotten joists, on to the next big ticket item - Crawl space insulation & cleanup!

Issues:
Odd span between joists - They measure ~32-33in on center. A bit sloppy, not all have the exact same spacing.
Fiberglass in there does not appear to be too old but half the bats are down / hanging. Batts in place are still moist )We are breaking records for days w/o precipitation right now.)
I'm a tall guy and there is not much room to work for me...
Edit: Just realized, the opening to the crawlspace is small & sunk into the ground, how can I get foam boards for the open listed below in there, wide enough?!

House: 70s Rambler, 1300Sqf (+ tandem garage on foundation).
Climate: PNW, between Seattle and Bellingham, WA - WET, mild, WET
Soil: Glacial Till, great drainage, elevated.

The initial thought was to seal gaps & put Roxul, or similar in, then we realized the wide span, needing ~29in wide insulation.
Right now I'm leaning towards fiberglass, or Roxul, covered with a 2in foil faced foam board, sealed with tape?!
Sprayfoam, even if I do it myself seems to be very(!) expensive for the material alone?!
I'm also leaning towards not doing this myself. Maybe if I was 1 foot shorter...
I'd like to derive an option that works for the house and the wallet, please chip in your 2 cent. TIA, Primergy

 

[Moto]

About the moisture, do you have a plastic vapor barrier on the floor? Any open vents?

 

[Scott H in Wheaton]

About the moisture, do you have a plastic vapor barrier on the floor? Any open vents?

excellent start

if there are no vents, put some in. Air flow will help reduce the moisture and stabilize the temperature.

Cover the dirt floor with heavy plastic, seal the seams and edges with tape. Run the plastic up the side wall to secure it.

33" span between joists is HUGE. Most floors will have 16" centered joists. Maybe add a joist for extra support and then use can use standard size insulation batts. Vapor barrier should go up against the floor above. Batts are secured with a stiff wire that spans from joist to joist and is simply pushed up into place, locking the ends into the side of the joists.

 

[JimNC]

There is a trend, at least in the southeast, to incorporate the crawl space into the living space. Basically seal up the crawl space with heavy plastic, insulate the crawl space walls, clean out all other insulation and then open a duct and cold air return in the crawl space.

I may have described this poorly, and can't even tell you what they call this so you can search for more, but one of the more learned members will likely chime in.

Jim

 

[zeeway]

What JimNC described is called crawl space encapsulation. We had it done on our previous house. And before you ask, yes, we had a specialty contractor perform the work. Since we had water showing up in the crawl space after heavy rains, they dug a french drain trench around the crawl space perimeter about 12 inches by 12 inches in cross section. They put a bed of gravel, then a 4 inch diameter perforated corrugated black plastic pipe enclosed in a fabric sleeve. The trench was then filled with gravel. The pipes connected to a sump pump.

All the exterior vents were closed off with foam insulation. The foundation walls were also insulated with rigid foam insulation, leaving about 6 inches exposed at the top for future termite inspections. The dirt floor of the crawl pace was then covered with a very thick plastic sheeting, perhaps 30 mil, that had plastic ridges on the underside. The seams were taped. There was also a dehumidifier installed, with the drain attached to the sump pump.

While paying $10k was painful, it solved a nasty moisture problem, which was turning into a potential mold issue. Instead of a nasty issue, it became a plus when we sold the house.

 

[gungatim]

I have a crawl space that is wet and rotted the floor on my hunting house. I did a bunch of research and basically what I learned is, you need to treat it like an attic or roof. it needs lots of ventilation, moisture comes from the ground as well as the air, and will condense on the floor or insulation.

encapsulation seemed like the best way to go but it is very expensive. at a minimum, make sure the bottom of the floor and insulation is sealed, but keep in mind any drafts or leaks within the floor itself will allow moisture to collect and condense inside the vapor barrier so it can be a catch 22.

make sure you have adequate ventilation so there is not a temperature differential between the air space in the crawl area and the outside. if it can equalize the temp, the moisture level will also equalize and not trap the moisture.

at least that was the consensus on all the builder sites I was researching on...my crawl space had zero venting save for the access for the well pump and tank (poorly made plywood cover).

 

[yeldogt]

If you have a dirt floor .. I'm not sure from your explanation --- this needs to be addressed. Nothing will work until the floor is covered.

Similar to attics ... the idea that a basement or crawl space needs to be ventilated to the outside is incorrect .. especially if you live in an area with any moisture.

You have to remove the moisture source and condition the space as part of the house -- depending on the rest of the structure -- a dehumidifier is sometimes required.

As mentioned above -- many specialized contractors do this kind of work.

 

[stm317]

Here in my part of the Midwest, they no longer vent crawlspaces. They've found that the vents tend to let more moisture in than they prevent. Full encapsulation is the way to go if you can do it. The idea is to seal up any vents/holes to the outside, lay down a very thick plastic that runs up the walls, and use spray foam to insulate the walls and rim joist. In some cases, they even add HVAC vents to condition the crawl just like the rest of the house.

I'd try pretty hard to add a joist in between existing joists if it were my house. That would give you spacing a lot closer to 16 on center. If you fully encapsulate, or just insulate the outer walls of the crawl, then there should be no need to have insulation between the joists, so the fact that you'd then have a bit less than 16 on center wouldn't be a problem.

 

[JRC3]

This is our first home, just got done with a bathroom reno including rotten joists, on to the next big ticket item - Crawl space insulation & cleanup!

Moisture causes two problems, the first is a fungus that rots wood. The second is termites. Being in WA you're probably lucky enough not to have termites, but I'd check.

The most obvious sign is the presence of mud tubes on the foundation. They can be a little smaller than a pencil or much larger. They can even build them straight up out of the dirt like a skyscraper till they find a span of wood.

Products like BoraCare and Timbor will treat both fungus and termites. Keeping humidity below 55% should also stop fungus or mold.

 

[finn]

I had a similar problem on a property I bought.

I ended up digging down to the footing level outside the foundation and installing drain tile over a gravel bed, running to daylight.

The original floor joists were rotted, and new joists were installed with incorrect spacing, so I gutted the house, cut the floor just inside the bottom wall sill, removed all the "new" as well as rotted floor joists, dug the crawl deeper, added drain tile inside the footings (run to daylight), reinstalled the "new" floor joists at proper spacing, sealed the foundation vents, added thick visquine to the sand floor, insulated the foundation walls with 2"rigid foam, had the rim joists spray foamed, and installed new subfloor and flooring.

It wasn't a weekend project, to say the least, but there are no more soaking wet fiberglass bats in the crawl, the floors are solid and level, and the house is dry and liveable

 

[Falcon67]

About the moisture, do you have a plastic vapor barrier on the floor? Any open vents?

Having owned more than one with a crawl space, this is the first thing - vapor barrier, vents and if necessary you remove the "skirting" around the house, dig a ditch and put in skirting with the ends below ground. Our last house did not have vapor barrier or craw space insulation - it was too close to the ground - but the perimeter skirting was at least 12" into the ground to keep water out from under the house.

 

[matt_i]

I had an old house in TN which had moisture in the crawlspace. I put in a garden variety dehumidifier and cut the plug out of the tank to allow continuous drain thru a hose, which I ran outside to a grated PVC "pot" in the yard.

next I screwed treated 1x2s to the block walls with tapcon screws. I placed the plastic on the floor, lapping it generously. Heavy stuff. The tails which ran up the walls were sandwiched into another 1x2 which was screwed to the first, creating sort of a clamp.

This made a huge difference in the house, it went from a musty-ish smell to zero smell in 2 days' time. Everyone who had been there before noted it immediately.

I had to pay for the electricity, but it was worthwhile. Ultimately I moved and sold it but I feel like that surely helped. Along the path, there appeared to be commercial dehumifidication units which cost more $ but had potentially longer lives. I just went with the garden variety from the box store, with the idea I could replace it if/when it died.

 

[risc]

It's a very regional thing. In the PNW, it's typical to put down a vapor barrier. Most use foam covers for the vents in the winter and open it up in the summer. It's split about 50/50 on insulating the floor if you have forced air; argument for insulation is reduced heating cost, argument against is keeping it drier down there and our temperate climate and cheap natural gas means it's pretty easy to keep the house warm.

33" span is scary, did your inspector say anything about that?

 

[primergy]

Thanks for all the replies & sorry for the delayed response from my end.

- Yes, I should have been clearer. The ground is bone dry and covered with a barrier. Sure is a cheap, translucent one as I can stretch it with little effort. It will be replaced in the process with more attention paid to detail.
- There are a number of vents, unobstructed on the outside but the curtains of hanging insulation sure do not help.
- I think a full encapsulation is cost prohibitive. We have other projects surrounding the house as well. Time is also a factor if I was to start this by myself to save $$$.
- The ~33in span is scary but the floors feel solid. House is ~25ft wide and also runs a huge girder down the middle. They used 4x10 beams and thick 1 1/8in subfloor panels. No comment from the inspector on the construction (guy was very thorough and detailed).

I'll add some pictures this weekend!

Edit:
We will have two companies coming out to prep a quote on different options. Not saying it will go that route but it will tell me what solutions they prefer and what it costs.

 

[firebirdparts]

Have you considered removing the insulation and putting back nothing? With that mild climate, I am not sure you actually are insulating anything. I am just asking. Also, you need to think about why you have joists on 33" centers. that's double what they should be. You need joists, and you don't need insulation. It's very curious.

 

[mrrooG8]

I'll never own a house with crawl space again. My previous house had one. Always fighting some stupid issue. High water table in our area *****. I installed plastic on the floor which was dirt and installed insulation under the floors. The floor was always so cold. When we first bought the house we had to treat for minor termites. Then when we sold the house we had a pipe slowly break. Didn't know it till we listed the house and people complained about a smell. We always thought we smelled a funk at times. A cast pipe under the kitchen drain had been leaking. I finally get the urge to go investigate and find standing water and The most god awe full smell. What a nightmare when you are trying to sell a house. Couple grand later and ServePro to the rescue and its was fixed. They had to dig down 6" and add new dirt and 3" of lime to get rid of damage. Lucky no mold had formed yet. I'd run a dehum all the time and make sure to keep vents open in the summer months no matter what. Never again will I deal with a crawl space.

 

[gungatim]

since you do have vents, one option is a power vent that fits in and replaces the regular vent, the fan will move air continuously. I looked into those and they're not bad price wise but I would have had to remove a concrete block to use it.

 

[Jackfre]

These work really well

http://www.tjernlund.com/crawl_space_ventilation.htm

 

[yeldogt]

venting only works when no humidity is present -- also .. using a power vent will depressurize the house .. not a good idea.

people with cold floors in the winter -- and a vented crawl space ...... how can it not be cold ... vented crawl spaces are outside ?

Close them up -- dry them out and make them part of the house. A conditioned crawl space does not need insulation on the floor unless it has radiant heat.

 

[finn]

The problem with vented crawl spaces in the summer is that it will get up to the 80s or 90s outside, with high humidity.

Meanwhile, the temperature in the crawl, benieth the house, is closer to the sixties.

The cool crawl space can't hold the moisture content of the hot, humid outside air, so you get condensation.

Seal the vents and that problem goes away.

Also, the bats under the floor hold on to the condensed water vapor. Mine were almost dripping when I removed and trashed them.

 

[JRC3]

Close them up -- dry them out and make them part of the house. A conditioned crawl space does not need insulation on the floor...

Yep. Just like a basement. And heat goes up.

 

[primergy]

Some research later, the span seems somewhat normal in the area / neighborhood. Afterall, they used 4x10 lumber and the thickest subfloor available.

I'll take closing off the crawlspace into consideration and will request quotes for that as well. Rather skeptical if I want to afford it.

 

[primergy]

The problem with vented crawl spaces in the summer is that it will get up to the 80s or 90s outside, with high humidity.

Meanwhile, the temperature in the crawl, benieth the house, is closer to the sixties.

The cool crawl space can't hold the moisture content of the hot, humid outside air, so you get condensation.

Seal the vents and that problem goes away.

Also, the bats under the floor hold on to the condensed water vapor. Mine were almost dripping when I removed and trashed them.

Makes sense. (We rarely see days in the 90s and humidity in the summer up here is normally ~60%.)

 

[ard]

Some research later, the span seems somewhat normal in the area / neighborhood. Afterall, they used 4x10 lumber and the thickest subfloor available.
.

My guess is that the sub-floor is 2x6 to 2x10 tongue and grove doug fir?

One thought:

Floor insulation, especially in somewhat mild climates, is not very cost effective. You might do well with a two step approach.... control the moisture, and make sure that is well under control for a year/season. THEN determine if floor insulation is called for.

If the heated spaces above are well sealed, air infiltration (and hot air loss) are controlled, and your ceiling and walls are well insulated (R whatever in walls and ceiling) then turn to the floors. But if ceiling and walls are not well done, dont waste the $$ on the underfloor.

My 2 cents

 

[primergy]

My guess is that the sub-floor is 2x6 to 2x10 tongue and grove doug fir?

One thought:

Floor insulation, especially in somewhat mild climates, is not very cost effective. You might do well with a two step approach.... control the moisture, and make sure that is well under control for a year/season. THEN determine if floor insulation is called for.

If the heated spaces above are well sealed, air infiltration (and hot air loss) are controlled, and your ceiling and walls are well insulated (R whatever in walls and ceiling) then turn to the floors. But if ceiling and walls are not well done, dont waste the $$ on the underfloor.

My 2 cents

4x8 Plywood, tongue & groove - 1.125in thick is what we found during the bathroom reno. The pattern continued in the adjacent rooms and can also be seen from below.
My 230lbs can jump around and the books stay in the shelves.

I'm not opposed to the idea to let it sit w/o insulation until next year & see what happens. It speaks to my workload & will, my wallet and seems pragmatic.

One more tidbit after some more research:
The house only has vents on two sides and about 1/3 less than what is standard today. Ugh. At least they are in the direction of predominant wind/airflow.
It does not seem to get better.
I'll be back with pictures this weekend and the opinions and quotes from the companies coming out next Tue.

Thanks again to all!

 

[acer66]

The problem with vented crawl spaces in the summer is that it will get up to the 80s or 90s outside, with high humidity.

Meanwhile, the temperature in the crawl, benieth the house, is closer to the sixties.

The cool crawl space can't hold the moisture content of the hot, humid outside air, so you get condensation.

Seal the vents and that problem goes away.

Also, the bats under the floor hold on to the condensed water vapor. Mine were almost dripping when I removed and trashed them.

This, the building inspector had me put in vents but I will seal them up once I am done with inspections.

 

[lakeroadster]

Radon gas an issue in your area? It is here.

We sealed all the vents except for one and installed a pvc pipe "chimney" that runs from the crawl space up and out the roof.

No plastic on the crawl space dirt or cinder blocks.

Also spray foamed all gaps around plumbing entry and exit down to crawl space.

Seems to work fine based on radon testing.

 

[yeldogt]

Radon gas an issue in your area? It is here.

We sealed all the vents except for one and installed a pvc pipe "chimney" that runs from the crawl space up and out the roof.

No plastic on the crawl space dirt or cinder blocks.

Also spray foamed all gaps around plumbing entry and exit down to crawl space.

Seems to work fine based on radon testing.

SO --- the floor is still dirt? If the is the case -- you are creating negative pressure in the house?

When you seal up the crawl -- placing plastic or a rat slab w/polly to isolate the ground -- the radon is removed prior to entering the house. In a very tight house a proper fresh air system will pressurizes the house -- this can sometimes be enough to make a passive radon system work. The fan is designed to be under the sealed crawl space -- it creates negative pressure under the slab and "*****" the radon from under the slab.

Fan size determined by system design -- a great system can use a fan with as little as 18w .. some use 150w .. and they run 24/7.

 

[lakeroadster]

Radon gas an issue in your area? It is here.

We sealed all the vents except for one and installed a pvc pipe "chimney" that runs from the crawl space up and out the roof.

No plastic on the crawl space dirt or cinder blocks.

Also spray foamed all gaps around plumbing entry and exit down to crawl space.

Seems to work fine based on radon testing.

SO --- the floor is still dirt? If the is the case -- you are creating negative pressure in the house?

How kemosabe?

The pvc pipe goes from the crawl space up through the home in a wall and out the roof. It acts as a chimney and pulls air from the crawl space. The crawl space has one open vent window.

So how does that create negative pressure in the house?

 

[finn]

The Radon exhaust tube should start beneath the sealed vapor barrier.

Just venting the crawl space, even with an open wall vent, reduces the air pressure in the entire crawl space, which actually increases radon gas flow from the unsealed earthen floor into the crawl space.

Flow is a function of delta p.

 

[primergy]

Thanks for that tidbit, I have heard about it years back but never remembered / saw it on checklists when considering properties / buying this one!
I had to look it up.
A Radon test has been performed in our neighborhood a few years back. No significant levels have been found.

 

[lakeroadster]

That's great primergy. one less thing to have to deal with.

The Radon exhaust tube should start beneath the sealed vapor barrier.

Just venting the crawl space, even with an open wall vent, reduces the air pressure in the entire crawl space, which actually increases radon gas flow from the unsealed earthen floor into the crawl space.

Flow is a function of delta p.

Theory is great. Actual results are better.

There is no vapor barrier.

The radon test verifies one isn't needed.

 

[yeldogt]

That's great primergy. one less thing to have to deal with.



Theory is great. Actual results are better.

There is no vapor barrier.

The radon test verifies one isn't needed.

Who installed the system -- no way it's proper. Go online and look at the systems. The radon test just says there is no radon around the test spot -- how close was it to the fan?

What's the CFM of the fan.

Who did the testing -- how many points?

No way it's working -- any other basement ?

 

[lakeroadster]

Geeze... does everything have to be a ******* match here? WTF is the matter with folks nowadays?

 

[850xpeps]

Crawl space encapsulation seems like a new thing for most of you but this is how we build up north. The drain tile or pipe in the sock that is perforated is buried in clean rock around the exterior of the foundation even with the underside of footing. Then a sump is dug in. Crawl space with a pump and the wheeping tile is plumb into it using the same pipe but without perforations. The crawl space floor is poly using 10mil and seals and taped to vapour barrier of the foundation walls after they are insulated as well. Should solve problems with moisture. If your insulating your floor joists your asking for moisture issues because you vapour barrier should then be between the subfloor and joists. Not on the cold side of the insulation.

 

[Jazz1]

Stegawrap is the poly I used in my crawl space. Its very durable and the poly fixed humidity problem in house. Went from 60% to 35% in winter so windows no longer sweat.

 

[yeldogt]

Geeze... does everything have to be a ******* match here? WTF is the matter with folks nowadays?

Would not want people to think that's a good system -- simple venting of crawl is not an effective way to eliminate radon ... sorry.

In some part of the county Radon is a big problem -- My place in PA being one.

Also -- we can't have open dirt anywhere within a dwelling because of radon risk.

Polly is cheap an effective.

 

[lakeroadster]

Would not want people to think that's a good system -- simple venting of crawl is not an effective way to eliminate radon ... sorry.

In some part of the county Radon is a big problem -- My place in PA being one.

Also -- we can't have open dirt anywhere within a dwelling because of radon risk.

Polly is cheap an effective.

Opinions vary about what is a good system...

The Radon Test proves what is a "good system".

 

[Bretny]

What JimNC described is called crawl space encapsulation. We had it done on our previous house. And before you ask, yes, we had a specialty contractor perform the work. Since we had water showing up in the crawl space after heavy rains, they dug a french drain trench around the crawl space perimeter about 12 inches by 12 inches in cross section. They put a bed of gravel, then a 4 inch diameter perforated corrugated black plastic pipe enclosed in a fabric sleeve. The trench was then filled with gravel. The pipes connected to a sump pump.

All the exterior vents were closed off with foam insulation. The foundation walls were also insulated with rigid foam insulation, leaving about 6 inches exposed at the top for future termite inspections. The dirt floor of the crawl pace was then covered with a very thick plastic sheeting, perhaps 30 mil, that had plastic ridges on the underside. The seams were taped. There was also a dehumidifier installed, with the drain attached to the sump pump.

While paying $10k was painful, it solved a nasty moisture problem, which was turning into a potential mold issue. Instead of a nasty issue, it became a plus when we sold the house.

They installed a sump pump and dehumidifier...sounds like they just masked the problem with those two things. A proper drain would idealy be gravety and it would keep the crawl space dry with out a dehumidifier.

 

[JRC3]

They installed a sump pump and dehumidifier...sounds like they just masked the problem with those two things. A proper drain would idealy be gravety and it would keep the crawl space dry with out a dehumidifier.

Sure, if you're lucky enough to have the property topography around your house for the drain to see daylight.