What can be done with a crawl space on an old house?

[gthomas785]

So here is some temp and RH data from my crawl space. By southern standards it in pretty good shape. But what I’m seeing is enough to concern me. I’m using a 15$ GoVee wireless temp and humidity sensor.
You might ask why does the RH drop every night at midnight? My leaky ductwork. By midnight the programmable ac has lowered the temp by a degree or two and isn’t running as often couple that with increasing RH outdoors. Now I have considered closing the vents off and adding a room dehumidifier. Thinking it would run 12 hours a day at .5 kw or so that’s 25$ a month for the summer. Seems like a cheap enough option. I’d add a vapor barrier. Logging the the temp and humidity can be helpful.
Evan

That's what my crawlspace humidity looks like with a dehumidifier running 24/7. Before the dehumidifier it would be pegged at 99% all summer long.

 

[Rob_Red]

Very interesting tell us about your current setup. How are you gathering this data? What’s the current configuration of the crawl space?

 

[BigJ273]

So here is some temp and RH data from my crawl space. By southern standards it in pretty good shape. But what I’m seeing is enough to concern me. I’m using a 15$ GoVee wireless temp and humidity sensor.
You might ask why does the RH drop every night at midnight? My leaky ductwork. By midnight the programmable ac has lowered the temp by a degree or two and isn’t running as often couple that with increasing RH outdoors. Now I have considered closing the vents off and adding a room dehumidifier. Thinking it would run 12 hours a day at .5 kw or so that’s 25$ a month for the summer. Seems like a cheap enough option. I’d add a vapor barrier. Logging the the temp and humidity can be helpful.
Evan

If you close the vents and add a dehumidifier, it would need to be a heavy duty one, made just for crawl spaces. And it would pretty much run non stop in the summer

 

[gthomas785]

Very interesting tell us about your current setup. How are you gathering this data? What’s the current configuration of the crawl space?

Are you asking me or @EbS-P ? I monitor the conditions in my crawlspace using a Ambient Weather wireless temp & humidity monitor, got them all over my house

Amazon.com

Maybe when I get home I'll post the data but I have to copy it from the SD card so we'll see.

About half of the crawlspace has a vapor barrier and the foundation walls insulated with spray foam. The rest is dirt with uninsulated foundation. Can't get back there. one of my projects for the fall is going to be trying to shove a plastic sheet in there and spread it out over the ground using a long pole.

My dehumidifier - Santa Fe Compact 70

https://www.sylvane.com/santa-fe-compact70-dehumidifier.html

 

[gthomas785]

Here's a pic from the last time I was down there

 

[Rob_Red]

Here's a pic from the last time I was down there
View attachment 280260

looks like mine! So do you plan to seal the plastic sheeting against the foundation walls? will just laying down a vaper barrier make a difference?

 

[gthomas785]

looks like mine! So do you plan to seal the plastic sheeting against the foundation walls? will just laying down a vaper barrier make a difference?

So obviously it's best to seal it at the foundation, and I'll do that wherever I can get my fat butt in far enough to do it. Even if it's not completely sealed though, every sqft of dirt that you cover up does make a difference.

 

[EbS-P]

If you close the vents and add a dehumidifier, it would need to be a heavy duty one, made just for crawl spaces. And it would pretty much run non stop in the summer

If I find a 70 pint house model on sale this summer/fall I will give it a go. I have had one for 10 years now in our 1000 sq foot basement that run a lot of hours.

I have looked at the Santa Fe and similar models. I haven’t been able to justify the cost. That was before I was tracking humidity.

Our crawl space is half the house. On the high side. The other half is daylight/ walk out/ drive in basement. It’s all beach sand and I just put gutters on the front and upsized the back. It’s all beach sand under there. Some plastic on a part of it. The bi metallic vents have not operated correctly in 30 years I’m guessing.
Part of me thinks if it has shown signs of mold or rot in almost 60 years I should just leave well enough alone.

I’m going to go open the vents and se what kind of difference that makes.

evan