Impact of Crawlspace Encapsulation on Cellar Performance

Living in the Carolinas we do not have basements, but almost exclusively crawlspaces. This is mainly due to the clay soils. When I built my new cellar, I used closed cell icynene foam, including under the floor in the crawlspace. It had performed really well with temperature fluctuations never more than 1.5 degrees and humidity 3-5% over the year. However cooler condensation fluctuated significantly over the seasons. Last year we had the crawlspace encapsulated due to moisture and mold issues. Typical crawlspaces are either just exposed earth or are covered with gravel and plastic sheeting as ours was. As is typical, the space has vents in the foundation to allow air flow, and in theory help keep humidity down. The vents were sealed as part of the encapsulation so that the only air transmission is between the crawlspace and the inside of the house. It was not long after that my cellar temperature and humidity flat-lined at 55 degrees and 70% humidity. Not a drop of condensation from the cooling unit. A huge bonus that I am attributing to having done this not inexpensive encapsulation. Anyone else experience this?

What was involved with encapsulating your crawl space?

  1. Clean out the crawlspace, removing any debris and the plastic sheeting that was on top of the floor gravel.
  2. Remove all bat insulation from between the floor joists under the floor.
  3. Mold remediation if needed. In our case it was not bad but needed to be done. Mostly on floor joists and some bloom on cinder block foundation and piers.
  4. Install foam insulation along full perimeter of the foundation including sealing the foundation vents.
  5. Seal all utility penetrations with expanding foam.
  6. Install high density padding on top of the gravel.
  7. Install and seal the encapsulating thick mil poly sheeting over padding and up the foundation walls and support piers.
  8. Wire and install de-humidifier(s) and pipe condensate discharges to the outside. We needed 2 due to crawlspace size.
  9. Install alarming puck water sensors at low areas in case of water intrusion.
  10. Make and install insulated crawlspace access door plug to keep space sealed.
  11. Install humidity and temperature sensors with remote monitor inside the house.

Kind of involved but so glad we did it.

I’m having a hard time envisioning your crawl space Kelly. Gotta pic?

I’m no expert, but could closing the vents cause a build up of radon?

I will take some pics tomorrow and post. Radon is not an issue where we are but because the space is now completely encapsulated, no radon could penetrate from the ground even if it was.

BTW, since the crawlspace is completely sealed from the outside and insulated around the inside of the foundation instead of under the floor, we no longer have cold areas in the house in winter and the temperature is much more even throughout. The crawlspace now stays within 2 - 2.5 degrees of the inside of the house. So the outside of the wine cellar sees the same temps on all sides with no fluctuation of humidity beyond what the house sees.

What’s the height of the space? Do you have to get on hands and knees to navigate?

I am confused here. Is this a passive or active cellar?

We have pretty good head space in ours. Ranging from bent over walking to mostly hands and knees though not belly crawl.

Active cellar on the first floor. Crawlspace goes under the cellar.

Here is a picture of the encapsulated crawlspace. Notice the foundation walls are insulated with aluminum faced foam board and the white liner is sealed along it and the piers. Under the encapsulating liner is a dense rubber mat that sits on the gravel covering the dirt. You can see one of the de-humidifiers sitting on a pad. Also note that there is no insulation between the floor joists. My cellar sits a good ways back so not visible in this picture but if you got under it you would see the joists filled with sprayed closed cell icynene foam.

  1. Doesn’t seem like it should be necessary for the purpose of cellar performance.

  2. It’s a plus for mold/rot prevention. Though those probably aren’t issues worth the expense for most situations that don’t have extreme moisture and have adequate ventilation. SoCal is pretty dry so people don’t opt for it as much as other regions.

  3. A risk is damage due to service and repairs that need to be done in the crawlspace. So the on grade barrier has to be sturdier than it’s simple climate control requires.

  4. if your FAU is in the crawspace area, you need to be sure that sealing the vents has not deprived it of necessary combustion air

  5. You also have to be sure that your HVAC handles the altered volume. The area within the encapsulated crawlspace becomes incorporated into the load.

EDIT: I see now that you are in the Carolinas, so indeed probably have more risk of crawspace moisture

Crawlspace moisture is a very big issue in the Carolinas. As noted this was done with absolutely no consideration for cellar performance but it became an added benefit. The heavy pad under the liner keeps the risk of barrier damage down. We have two air handling (electric heat pump)/gas furnace units located there. Both have concentric intake and exhaust lines to the outside. Our electric bill dropped about 10% after installation. The gas furnaces are for auxiliary heat for when it gets really cold and the HPs become inefficient. Gas expense in minimal.

I now understand. Presumably the space will be used for case-lot long term storage. Getting stuff in and out would be a pain in the ass, so I assume you won’t be crawling down there to pull a bottle for dinner!

When I was growing up, we had one of those under my parents’ house, but it would have been useless for this purpose. All the trolls, goblins, and ax-murderers who lived down there would have consumed every bottle

My in-laws live in Laurens and encapsulated their crawl space. They do not have a cellar but did notice a move even temperature in the house when it was complete.

The problem with encapsulation is that the moisture issue is still there, just outside of the barrier. A foundation drain is still needed and is frequently not installed, or at least not properly. I have talked to a lot of single family builders in the Greenville area who only do slabs because of the issues with crawl spaces in this area.

Yes, you still need to address the source of any water intrusion and keep water moving away from the foundation. Not to get too far off the wine cellar topic but one of our biggest issues were undersized gutters and clogged drains. The home battle never ends.