Crawl Space Encapsulation Real-World Energy Savings
This is for a very small segment of the population who will nerd out over this sort of thing, but I’m sharing my findings for anyone else considering crawl space encapsulation as a way to make their home more efficient.
Don’t need the story? Go straight to the data
Shortly after moving into our first home, my wife and I weren’t prepared for just how cold our floors would be (we’d been living in apartments for the previous decade and a half). And we were wasting a lot of energy trying to make the place comfortable — our slippers weren’t cutting it!
Insulating the crawl space seemed like a surefire way to make the place more cozy, but after seeing some triggering photos on the web of sagging, wet, moldy batting (the fluffy pink stuff), I started looking into encapsulation instead.
Our home is located in coastal NorCal. It’s a 1000 sq/ft ranch with a vented crawl space. Underneath the house was nothing but dirt and bare subfloor. The space was cramped — you’re army-crawling no matter where you go down there — and it could definitely stand to be upgraded!
Once we had dealt with the downstairs fur balls, I called up Clean Crawl Space Inc for an estimate, and they sent out a super nice fellow by the name of Dan to assess the place and come up with a plan:
- Seal 14 of the 16 crawl space vents
- Seal up any plumbing/electrical holes cut in the subfloor with spray foam
- Install Delta Drainage Matting over the ground and top it off with the CleanSpace Vapor Barrier to seal out any moisture trapped in the clay under the house
It sounded like a good plan to keep moisture out, but I was wary about how effective it would be at warming up the place.
But we went for it.
Wanting to confirm we were making a wise investment (and jumping at an opportunity to play scientist) I got to work taking measurements. Using an infrared thermometer I borrowed from work (thanks, COVID), I was able to take numerous surface temperature readings throughout the house before and after the work was done in the crawl space. Then, I compiled all the readings, along with boatloads of other data: local weather conditions, ambient indoor air temps, control data from nearby friends, as well as state averages, and put them into 1 chart for others thinking about doing similar work. And the results are in!
I tried my damnedest to account for all the variables I could. And here are my most interesting takeaways:
- Floor surface temperatures are now 1.16°F closer in line with ambient indoor air temps. That’s 38% closer to indoor air temps than before encapsulation.
- We used 31% less natural gas per day in March vs Feb (1.8m fewer BTUs month over month). However, due to a number of factors, reductions in energy use from Feb to March is a common trend in most households. So I’ve also checked the energy usage of some friends living across the Bay, plus the entire state’s average, and was able to calculate that we saved 23% more than the average household!
- Our March energy bill was $49 less than February’s (a 20% reduction)
Of course, there are a number of variables at play here that are hard to account for: hot water usage, our Nest thermostat’s algorithms, how many hours of sunshine we had each day, etc. But I think this gives a pretty thorough picture of what you could expect when doing similar work at your house. Just remember, this is passive insulation, so don’t go into it expecting to have radiant heating afterward and you’ll be a happy camper! It will even help keep your place cool in the summer (or so they tell me).
I suspect most of our gains can be attributed to the sealing of the vents and subfloor holes, but it’s my understanding that you can’t do those things without also installing a moisture barrier unless you’re planning on becoming a mold farmer.
The materials and techniques we opted for have a 25-year warranty. And all in the work was $5,800.
And there you have it!
We still wear our slippers, but it is noticeably warmer. If we wanted to take things to the next level, we would do spray foam insulation in-between all the floor joists, but considering that temps almost never get below 45ºF here, I don’t think we’ll go that far.
If you’ve made it this far, I’m impressed! I hope this was helpful/informative for you.
P.S. I don’t work for Clean Crawl Space, nor was I paid to write this. I’m just a first-time homeowner and neutral 3rd party sharing my experience with crawl space encapsulation.
If you’d like to see all the data I collected and/or check my math, the full spreadsheet is here:
- https://docs.google.com/spreadsheets/d/1VPbMUPv2OpebTJCJRmVsFsXzT6CaI_NAYDGfpRh5RQs/edit?usp=sharing
And for further reading on the science of crawl spaces and moisture control check out:
And finally, here’s the company that did all the work:
