Crawl space discussion, vented or conditioned space?

[gahrajmahal]

This is regarding my stepsons home addition currently in progress. Location, Cincinnati Ohio. Hot and humid in the summer, rainy and wet in the spring, can get zero in winter for a month at a time. I know, sounds great doesn’t it? Ha ha.

They are adding 16 ft. Of length to their 1920 bungalow style home with full basement. The addition has only a cement block crawl space (The additions foundation). The contractor ignored the opportunity to smooth the interior of the crawl space and add a vapor barrier and styrofoam insulation to the walls As was on the architects blueprint. Instead he dumped about a cubic yard of gravel plus broken cement from the patio demolition in there. The crawl space is now framed over with a two story addition, nicely done by a secondary contractor. The crawl space walls are to receive styrofoam insulation down to the debris level on the inside (the bank inspector says that’s ok) and then plastic will be spread over the bottom and run up the walls for a vapor barrier like the blueprint Instructs to do. There are two vents in the side/upper wall and an access window from the existing basement. Right now the blueprint has the toilet waste line and some hvac vents inside the crawl space. The prints show no insulation on the exposed floor joists.

researching online a vented crawl space is not typical anymore. Conditioned air from the basement would circulate into the unvented space.

Another thought would be to insulate the floor joists with batt insulation then nail foil backed foam under the floor joists taping the seams. You could then leave the crawl space vented.

Opinions about the best option for this crawl space would really be appreciated.
Thanks

 

[pattenp]

The best thing I ever did was to close up my crawl space added vapor barrier on ground and up walls and added a dehumidifier. I live in Virginia and have terrible humidity and duct work under house would sweat in summer from AC. Stays dry now and eliminated musty smell.

 

[slowtwitch73]

You could run a radon mitigation system... air tight barrier glued to the walls with fan pulling under the barrier. Deals with moisture, deals with ground gases and smells.

 

[Chris705]

I would recommend the conditioned crawl space and not vent it. I think your stepson will have less long term problems that way. A good heavy 10 mil vb would stand up nicel to occasional access. Maybe good to try to get some of the broken concrete out of there now before vb goes down. I run a dehumidifier all summer and never open the basement windows. The damp/musty basement smell never shows up & the house is about 90 years old.

 

[Sumboodie]

Unless the floor is insulated, that's going to be mighty cold in the winter. Any plumbing in that area?

 

[finn]

Styrofoam on the walls, spray foam the rim joists, and install a vapor barrier.

If he can afford it, spray foam on top of the vapor barrier, too.


Seal any vents.

 

[gahrajmahal]

Unless the floor is insulated, that's going to be mighty cold in the winter. Any plumbing in that area?

The current plan shows a single 4” pvc waste pipe about 10 ft. In length.

 

[d.mcfarland]

From my understanding of crawl spaces, they can be vented but are "recommended" to be sealed and conditioned and dehumidified.

 

[mike93lx]

The best thing I ever did was to close up my crawl space added vapor barrier on ground and up walls and added a dehumidifier. I live in Virginia and have terrible humidity and duct work under house would sweat in summer from AC. Stays dry now and eliminated musty smell.

This is exactly what I did, also in VA. Next step is to insulate the walls and remove the floor insulation.

This idea that houses "need to breathe", needs to die. Seal them up tight and control the air.

 

[larry4406]

I recommend the conditioned crawl space as well.

We are nearing the end of our kitchen extension/ renovation which is on a 16x8' conditioned crawl space:

• Poured 24x8" spread footings (over kill) with weep drains. These were keyed into the existing house foundation by cutting pockets into the wall and drilling and epoxied rebar. Inserted vertical rebar to reinforce the block walls
• Block walls, cells reinforced with rebar, cells filled, exterior parged smoothed, and then hot spray tar waterproofed and exterior draintile. Each bed course of mortar is tied into the house wall with drilled and epoxied rebar hairpin
• Poured 4" concrete slab over vapor barrier, over 4" gravel with draintile and sump crock with pump.
• Block interior walls are closed cell spray foam insulated which extends over the sill plate and the band board for complete air seal.
• HVAC supply register

Other than the low height, it is built just like a basement. My inspector was quite impressed!

 

[mejhaha]

I also vote for encapsulated space. I am also in Va and had standing water from ductwork condensation dripping onto the existing vapor barrier as well as mold.

I did a lot of research on this; some of the highlights were studies done by Oak Ridge lab and a huge study by Advanced Energy in North Carolina.

For mine it was:

- 12 mil vapor barrier on floor overlapped with seams taped, piers wrapped as well
- Closing and sealing the existing vents with XPS and closed cell spray foam
- Sealing all the penetrations in the walls (water spigots, wiring, old hole for dryer vent) as well as the floor/bottom plate (as in were all the wiring and plumbing goes through bottom plates)
- XPS on the walls leaving a 2” area at the top for “termite inspection,” as well as XPS in the band joist area with spray foam around the perimeter of each XPS block
- New well sealing crawl space door
- Dehumidifier

Got a quote for this - was ~30k in 2016, I can’t imagine what it would be now. I DIY’ed it and it was very simple - cost me about 5k.

Now the humidity never gets above 55% or temp above 65 degrees, and over the course of the year between this project and installing smart thermostats my HVAC bills decreased by about 10%.

 

[jrsavoie]

Never do a crawl space if you can do a basement.
If you're doing a crawl space, you have at least 4' of wall and the footing paid for already.

 

[Showkey]

I would open the crawl space to the basement …….so they share the same air circulation.

Typical crawl space that contractor seal after the fact ………too bad it was not done at the time for construction.

 

[Jackfre]

This has been an effective product for crawl space problems. Yes, do the sealing as noted above, but if there are issues going forward these crawl space ventilators work very well. They have a built in humidistat.

UnderAire™ Crawl Space Ventilation Fans : Dryer Boosting Fan : Tjernlund Products, Inc.

Tjernlund Products offers superior draft and ventilation solutions. We offer just some of the following products: Crawl space ventilation fans and dryer boosting fan.

www.tjernlund.com

 

[matt_i]

Definitely wire some lights in there, its bad enough to have to crawl up in there, then have no light.

Whatever you can do while the space is open from the top will be 10x easier than having to crawl thru there after the floor is decked. Would be great to protect the plastic sheeting somehow from the builders, maybe the 2nd layer goes in over that (?)

I've seen stupid small scuttle holes placed to access a crawlspace before, my take was the builder didn't want to have to deal with a header if they got it large enough, and wasn't their problem long-term. The idea to go full basement would be OK but I think the existing stem wall would have to remain intact and have a doorway (etc) cut thru it.

I had an old country house in TN with a musty smell, when I covered the floor with plastic wrap and put a dehumifier in there it changed everything for the better very quickly. I drained the constant-flow condensate out under the foundation and out thru PVC to a riser in the yard.

 

[gahrajmahal]

Thanks so much for all the detailed and first hand experience. I am trying very hard to stay out of this and let his general contractor handle this build. His loan is tied into the builder getting paid on a schedule once the bank inspects the work and receipts. My stepson, a wonderful man and dad wants to allow this build to happen without him and me getting roped into doing work on the project. That is what he is paying the builder for. But, as we all know builders and the professionals they hire come at all levels of quality.

I sent a link to this thread so he can read all the knowledge presented here.

Thanks again, much appreciated!

 

[gahrajmahal]

Wiring for lights is genius!

Is there a good online source for specific products for doing this job outside of hiring a specialist?

 

[larry4406]

Wiring for lights is genius!

Is there a good online source for specific products for doing this job outside of hiring a specialist?

I still need to do this in my crawl space before final inspection.

I’m going you use a caged or lense type fixture so the bulb can’t get broken. In my case (16x8’ crawl at ~30” tall) I think I can get by with one mounted on the wall common with the house foundation and mount it up near the top. Switch will be in basement adjacent old window which is the new access point.

 

[Mike1903]

Over here in PNW, most homes have crawlspaces and pretty much all of them are well vented. We got insulation installed in the joists and a vapor barrier to keep the moisture down. Otherwise, it is free air flow.

I am looking into getting a ratslab (2-4” of low strength cement rough screeded) to keep any creatures that dig in under the foundation.

 

[Uncle murph]

This is regarding my stepsons home addition currently in progress. Location, Cincinnati Ohio. Hot and humid in the summer, rainy and wet in the spring, can get zero in winter for a month at a time. I know, sounds great doesn’t it? Ha ha.

They are adding 16 ft. Of length to their 1920 bungalow style home with full basement. The addition has only a cement block crawl space (The additions foundation). The contractor ignored the opportunity to smooth the interior of the crawl space and add a vapor barrier and styrofoam insulation to the walls As was on the architects blueprint. Instead he dumped about a cubic yard of gravel plus broken cement from the patio demolition in there. The crawl space is now framed over with a two story addition, nicely done by a secondary contractor. The crawl space walls are to receive styrofoam insulation down to the debris level on the inside (the bank inspector says that’s ok) and then plastic will be spread over the bottom and run up the walls for a vapor barrier like the blueprint Instructs to do. There are two vents in the side/upper wall and an access window from the existing basement. Right now the blueprint has the toilet waste line and some hvac vents inside the crawl space. The prints show no insulation on the exposed floor joists.

researching online a vented crawl space is not typical anymore. Conditioned air from the basement would circulate into the unvented space.

Another thought would be to insulate the floor joists with batt insulation then nail foil backed foam under the floor joists taping the seams. You could then leave the crawl space vented.

Opinions about the best option for this crawl space would really be appreciated.
Thanks

Shame on the swine contractor but definitely go with the conditioned space,vents are better than nothing but controlling the temp and humidity will yield a much more livable space above.

 

[jrsavoie]

I would demand they clean the **** out of the crawl or withhold payment. If that's still possible. Or take them to court if that's possible.
How tall are the crawlspace walls?
Is he 4 foot to the bottom of the footing.

Off topic. But something I have seen often Is a stem wall sticking out of the ground 3' or more and then down 42" or more to the top of the footing with an unexcavated crawl space. All they are lacking is a couple feet of wall, a floor and an egress for a nice basement.
The floor can always be poured later.

 

[vavet]

We did a conditioned crawl on our new home construction in 2015. It was the first one our builder ever did, I think. One thing they didn’t think of was termite inspections. There are systems that run through the walls prior to closing them up that can serve as a monitor, but I didn’t know to ask about it and the builder apparently didn’t know or didn’t care. I now use the in ground termite stations placed every 15 feet around the foundation perimeter and have to inspect them every 3 months, replace the bait with poison if I find activity, etc.. It was so much easier when I just paid a pest control company $300/ year to do an annual treatment (for other pests) and termite inspection of the foundation.

 

[Jackfre]

Also, assuming you have to crawl into the CS, put a trapeze bar across the bottom of the floor joists. I used 3/4” black pipe and a couple two hole pipe straps screwed to the bottom of the joist. It is so much easier to pull yourself up and in rather than trying to do the crawl over the foundation. I have lights in my crawl space. No way I will ever go into a crawl space without seeing what is in there.

 

[mike93lx]

We did a conditioned crawl on our new home construction in 2015. It was the first one our builder ever did, I think. One thing they didn’t think of was termite inspections. There are systems that run through the walls prior to closing them up that can serve as a monitor, but I didn’t know to ask about it and the builder apparently didn’t know or didn’t care. I now use the in ground termite stations placed every 15 feet around the foundation perimeter and have to inspect them every 3 months, replace the bait with poison if I find activity, etc.. It was so much easier when I just paid a pest control company $300/ year to do an annual treatment (for other pests) and termite inspection of the foundation.

They were supposed to leave the sill exposed for inspections. It's required in VA and likely elsewhere

 

[CraigStu]

For lighting I'd get an LED unit.

https://www.lowes.com/pd/Utilitech-Strip-4-ft-Shop-Light/1003093616

Hang it like this w/ chain or screw it right to the bottom of a couple of the joists. No bulbs to break.

 

[mike93lx]

For lighting I'd get an LED unit.

https://www.lowes.com/pd/Utilitech-Strip-4-ft-Shop-Light/1003093616

Hang it like this w/ chain or screw it right to the bottom of a couple of the joists. No bulbs to break.

Unless you have a 6+ ft crawl, that doesn't feel like a good option at all. A set of string lights would be way better, although I just bring my Dewalt or Milwaukee cordless light when I need to do work in my crawl

 

[gahrajmahal]

I have a few 4’ LED shop lights I’ve volunteered if he wants them.

 

[paredown]

Wiring for lights is genius!

Is there a good online source for specific products for doing this job outside of hiring a specialist?

I went primitive with mine. Lowes sells a crimp-on style standard lamp socket. I bought a bunch and crimped them on to cheap-ish extension cords, and used standard light bulbs with non-shatter coating. Nailed them up in a loop (the sockets have a nailing tab), and left the plug end close to the outlet by my hatch, so I can plug them in as needed.

Not all of them worked--I probably could have been a little more careful with the crimps, but enough of them work so I can get around down there and see what I'm doing.

 

[dougf]

BLUF: I just had a house built, we closed September 2021 and had the option for an unfinished basement for another 20k added to the price, but being cheap I said no (kicking myself hard now) and ended up with a crawl space I could stand up in. 11 months later and we are paying 26k for Foundation Recovery Systems to do their thing due to moisture and mold.

If I could go back in time I would 1000000% get the unfinished basement. We started smelling musty/moldy smells coming up from the vents, went into the crawl space and noticed standing water on the dirt. Called them out and 80% humidity down there, standing water, and wood measured as high as 30% so we had to do something. Getting drainage, 20 mil liner, supports wrapped, sides sealed with foam and insulated, triple sump pump, and large dehumidifier.

Absolutely close those vents and do a vapor barrier and dehumidifier. Keep the space conditioned.

 

[gahrajmahal]

BLUF: I just had a house built, we closed September 2021 and had the option for an unfinished basement for another 20k added to the price, but being cheap I said no (kicking myself hard now) and ended up with a crawl space I could stand up in. 11 months later and we are paying 26k for Foundation Recovery Systems to do their thing due to moisture and mold.

If I could go back in time I would 1000000% get the unfinished basement. We started smelling musty/moldy smells coming up from the vents, went into the crawl space and noticed standing water on the dirt. Called them out and 80% humidity down there, standing water, and wood measured as high as 30% so we had to do something. Getting drainage, 20 mil liner, supports wrapped, sides sealed with foam and insulated, triple sump pump, and large dehumidifier.

Absolutely close those vents and do a vapor barrier and dehumidifier. Keep the space conditioned.

Thanks for that. I’ll make sure we get it done right.

 

[GarageHommie]

I had a wet crawlspace for 20 years and finally got around to encapsulating it last summer. I called several "pros", but decided to take on the job myself. I was not comfortable with a perimeter drain as I, like so many here in the south, have very shallow footings. So, I hired a subcontractor that agreed to dig a 20–30-inch-deep x 20-inch-wide L-shaped drainage system clear of perimeter walls and piers.

Here is where the DIY kicks in. I lined the open ditch with the best filter fabric from Lowe's and installed the 4" corrugated pipe on a bed of #4 river rock. I used a Little Giant sump pump kit at the lowest point.

Next, I built a ramp into my crawlspace and placed 4 cubic yards of smooth #4 river rock in the ditch with a little dump wagon.

After a one-week break and my encapsulation material arriving, the second most labor-intensive phase began. I didn't want a low-vapor-permeable liner. I wanted a non-vapor-permeable liner. So after Googling for a few hours, I found that material: vinyl PVC, otherwise known as pond liner material.
I now have a dry crawl space and that’s without the use of a dehumidifier.

 

[Snapped-off]

My house had a full basement. At some point an addition was built. Under the addition is just a crawl space. It's open to the basement via 2 access windows, but completely closed off from the outside.

Inside has what I thought was vapor barrier, but the backside is blue with the same design most pool linings have. Didn't notice any issues this year. Everything seemed nice and dry. There's no insulation. Heat bill was cheap.