Crawlspace encapsulation

[mellow]

Pics of where the dehumidifier is in my crawlspace:




Other side of crawlspace:

 

[EbS-P]

I am starting to understand why the unit has some bad reviews on amazon for not lasting that long if their units are doing the same thing as mine and cycling as much as mine does, it is no wonder they only last 3 years.

They are talked about as the premiere whole house /crawl space dehumidification manufacturer. I am considering an Oasis unit for my house

 

[shoot-straight]

Mine is sealed and sprayfoamed. I have A cheap DH from lowes. It does fine. Get the 3 year extra warranty, they will only last a few years but then you get a new one. My space runs between 50-60%.

 

[mellow]

Santa Fe is sending a new humidity control board, will see if that fixes the issue. They gave me some things to try and it didn't work, still acting like it is on a timer and turning on for about 5 minutes then off for 5 minutes. Yesterday it turned on 142 times, way to many times.

 

[EbS-P]

Getting quotes for mine. Will likely seal and insulate while all the ducts are ripped out. Not looking forward to it.

 

[mellow]

Just an update, the new humidity controller is doing the same thing as the one it replaced. Now that the humidity is dropping I just set it to power on during the day and shut off at night. Will take this up again in the spring, probably will install a digital hygrometer to turn it on and off and not worry about it anymore.

Incase you are curious about the manual hygrometer they use, it is dead simple but doesn't work right:

 

[hockeypuck]

I was talking to a friend that has been rehabbing his 250 year old farm house and his latest project was to use 2" thick pavers to place in his crawl space, over sand that was there. He then used mortar to seal the edges up against the foundation which consisted of granite block and field stone. Probably not at tight as plastic but he said he noticed the difference within a few days of completion. He had about 2 to 3 feet of head height.

 

[mirabelorion]

Hello. I have a 106 year old with a basement that is open to a crawlspace. I recently talked with a contractor about encapsulating the crawlspace, and they said they could do most of it, however, the crawlspace under some additions is too tight to install the encapsulation. They suggested encapsulating the accessible areas and sealing off the portions that can't be accessed. There are no existing vents that would allow the addition crawlspace to breathe, I'm afraid that closing off the crawlspace under the additions might cause more problems that not encapsulating at all.

I'm considering encapsulating the accessible areas, but not closing off the addition crawlspaces to help them breathe a little. Would this completely defeat the purpose of the encapsulation or would I still get some benefit?

 

[EbS-P]

What is your reasoning for wanting to encapsulate? Our house was built is 1968. The crawlspace is, for the area, quite dry and in decent shape. The original insulation was falling down. I got a quote for $14$ to encapsulate and add a dehumidifier. There is no way I could ever make that money back in energy savings.

So took out all the old insulation and added new. $700 and a weekend.

My point is unless you need to fix a problem encapsulation while I think almost always is the best solution it may not make financial sense.

 

[gthomas785]

I have the same situation in my house.
Crawlspaces have moisture. Moisture will rot the framing of your house so you should do something. Ventilating if you live in a dry area or running a dehumidifier would be the primary line of attack and that alone will solve the moisture issue. But then you are basically paying for energy to dry out the ground - equivalent to heating the outdoors. So: any moisture barriers you can add over the bare dirt will decrease the load on your dehumidifier, saving energy. If you can't get to some of the areas, then that's just what it is but don't seal those areas off. They need the moisture removed somehow either by ventilation or dehumidification.

In case you live in a humid area, I found a neat arduino project online that uses local indoor and outdoor sensors to decide whether to ventilate the crawlspace based on the dew point. Basically if the outdoor dew point is lower than in the crawlspace it turns on a fan.
I added a couple lines of code to mine that also turns on the dehumidifier when the fan is not running for a certain time.

ArDewpoint: Dew Point Based Ventilation Controller

ArDewpoint: Dew Point Based Ventilation Controller: Overview: This simple Arduino project, which I'm calling ArDewpoint, uses two sensors to compare the moisture content inside and outside of a structure. It triggers a relay to drive a fan if there is less moisture in the outside air, bringing...

www.instructables.com

 

[mellow]

Hello. I have a 106 year old with a basement that is open to a crawlspace. I recently talked with a contractor about encapsulating the crawlspace, and they said they could do most of it, however, the crawlspace under some additions is too tight to install the encapsulation. They suggested encapsulating the accessible areas and sealing off the portions that can't be accessed. There are no existing vents that would allow the addition crawlspace to breathe, I'm afraid that closing off the crawlspace under the additions might cause more problems that not encapsulating at all.

I'm considering encapsulating the accessible areas, but not closing off the addition crawlspaces to help them breathe a little. Would this completely defeat the purpose of the encapsulation or would I still get some benefit?

I would get a couple bids from encapsulation companies and see what they think, then take it from there.

 

[BigJ273]

So, just to circle back on this thread. Last year I sealed up the vents myself and installed 2 industrial strength dehumidifiers that I purchased and installed myself. I gotta say, I couldn’t be happier. My crawlspace has been dry as a bone. They don’t run nonstop, they turn on and off based on the humidity. It’s not FULLY encapsulated, but what I’m doing is working and I have not noticed any real difference in my electric bill. 2 dehus cost me about $1600 total. And I used foam board to seal the vents myself. Now, in the winter, when the air is drier, I turn them off and open the vents back up. I like the idea of it breathing some. It seems to be working great for me.

 

[mellow]

Not sure how you are not noticing an increase on your electric bill, my one dehumidifier costs about $16/month (90 kWh) to run and I have it on a timer so it only has power 12 hours a day (actual run time is based on humidity)

Before I started cutting down the time it was on I was up near $50/month in electric for 1.

 

[BigJ273]

Not sure how you are not noticing an increase on your electric bill, my one dehumidifier costs about $16/month (90 kWh) to run and I have it on a timer so it only has power 12 hours a day (actual run time is based on humidity)

Before I started cutting down the time it was on I was up near $50/month in electric for 1

I'm sure it's a little higher, but nothing that causes me any concern.

 

[stoveliker]

It's all relative. $15 on a $100 bill is noticeable. $15 on a $450 bill is not.

 

[EatenByLimestone]

Multiple sources say that the average house uses 800-900 kWh/mo. I can’t fathom that, but numbers be numbers.

 

[RustyShackleford]

Haven't read the whole thread, but ... neither quote involves putting rigid foam insulation on the foundation walls ?!? That's ridiculous.

 

[RustyShackleford]

Just an update, I cut my dehumidifier back to 50% and now I am at around .25 cents day in power use, what is interesting is it didn't cut back how many times is on, it just cut back how long it runs for.

Current Daily total: 152 times on at 5h 4m
Past Daily total: 123 times on at 10h 40m

My crawlspace dehumidifier (Honeywell DR65A3000) was short-cycling as well. Fortunately it has terminals so you can override the built-in dehumidistat and supply your own. And I just happened to have a mechanical dehumidistat lying around from an ill-advised** installation of fans on my foundation vents (or you can pick one up for $30 or so on Amazon). Works great now.

**Before I encapsulated my crawlspace, some guys installed a pair of vent fans in my foundation vents. An absolutely ridiculous thing to do here in the hot humid south. You're pulling air with 70-degree dew-point into an area that's cooler than that if you have your A/C running, which of course you do. It was literally raining in there. It's absurd.

 

[BigJ273]

My crawlspace dehumidifier (Honeywell DR65A3000) was short-cycling as well. Fortunately it has terminals so you can override the built-in dehumidistat and supply your own. And I just happened to have a mechanical dehumidistat lying around from an ill-advised** installation of fans on my foundation vents (or you can pick one up for $30 or so on Amazon). Works great now.

**Before I encapsulated my crawlspace, some guys installed a pair of vent fans in my foundation vents. An absolutely ridiculous thing to do here in the hot humid south. You're pulling air with 70-degree dew-point into an area that's cooler than that if you have your A/C running, which of course you do. It was literally raining in there. It's absurd.

Yea. Exact opposite of what u wanna do. In the summer u wanna keep the humid air out and condition it w a dehu I open my vents in the winter cause cool air is dry air. And I like the airflow.

 

[begreen]

Yea. Exact opposite of what u wanna do. In the summer u wanna keep the humid air out and condition it w a dehu I open my vents in the winter cause cool air is dry air. And I like the airflow.

We have the opposite conditions with dry summers. I open the space in the summer and close it off in the winter. This keeps the space at a relatively uniform 55-60º in the winter. It's nice to have warmer floors even when it's 20º outside.

 

[stoveliker]

We have the opposite conditions with dry summers. I open the space in the summer and close it off in the winter. This keeps the space at a relatively uniform 55-60º in the winter. It's nice to have warmer floors even when it's 20º outside.

It's interesting how climate differences can change the best solution.

I have (need) a minisplit on dehumidification mode in summer. Nice to have cool floors. It mostly replaces the conventional bucket dehumidifier that was noisy and warmed up the space. I still have the bucket thing on, but it now runs only on the most humid days (or the days that my kids don't close the door to the garage ...) The minisplit is not able to keep the relative humidity below 60% on the worst days.

(I also have a stove down there - it's nice to have toasty warm floors in winter too!!)

 

[RustyShackleford]

Mine is sealed and sprayfoamed. I have A cheap DH from lowes.

Yep, that's what I was using too, and it worked fine; my crawlspace guru suggested that it might be less efficient (higher electricity usage) and might not last that long (but it did). But some crazy man was selling a Honeywell DR65A3000 for $50, so ...

 

[mellow]

One thing I have noticed since doing the encapsulation is the increase of spider webs and spiders in the crawlspace, they are everywhere now. I need to get a new door to my crawlspace as that is my weak point, everything else should be sealed.

Thinking about either doing a couple foggers down there or taking a sprayer full of spider killer, with the dehumidifier off of course.

 

[EatenByLimestone]

When I build crawlspace doors I build a 4 sided frame to fit the opening size and then build a tight fitting door to fit inside the frame. The 4 sided frame allows you to seal around the frame to keep mice and such out easier.