Sealed vs Vented Crawl Space: Case Study
This study by: Advanced Energy is thee authoritative word on the matter in the Southeast.
It is the only study done so far in the Southeast where they took 12 homes sealed some and left vented others in a similar environment and came up with energy saving results. I have sealed well over 1000+ crawl spaces personally and will give you a quick summation of their findings.
Sealed Crawl Spaces with:
-R19 insulated band joists
-With regulated inflow of air supply lead to a 15.7% reduction in energy usage.
They hooked up a meter that has a Data Logger similar to THIS ONE. The Data logger meter reader was only reading the Heat Pumps energy usage.
A 15.3% savings (found on pg 8 lower left of the study) was found when simply 100% sealing the crawl space floor and:
-Leaving fiberglass insulation in the crawl ceiling (Between the joists)
-continuing plastic up the wall to 3 inches from top per CODE to allow for NC termite inspections.
-Sealing off foundation vents
As for the use of dehumidifiers to be used in the process they found that, using the standard regulated inflow of air through an air supply feed that, relative humidity in the worst warmer months still stays within 55%-60% RH (relative humidity) range which is desirable.
Vented crawlspaces would climb to above 60% and past 80%RH + and 19%+ Moisture content in the beams which leads to mold growth.
These were new homes with NEW insulation under the floors and sealing new insulation is fine on new construction. But the difference in putting insulation batting on the entire floor as apposed to Insulating just the walls is:
-Both methods of insulation have a similar price, that’s why builders chose insulating the walls. Its cleaner and neater without fiberglass dust involved.
-Insulated walls don’t fall down like insulation batting does.
-If this is an existing home your vented crawl is already filled with mold and camel crickets and there poop and mice and there fecal and snakes …etc. Simply sealing the floor and sealing all that mess in isn’t the best for quality air quality.
-Walled insulation gained 15.7% as Insulation on the crawl ceiling gained 15.3%.
The 10 page study for a crawlspace tech like myself is an interesting read … I couldn’t imagine a civilian suffering through it … so I hope this helps. Please comment below if you read the study and comment on the accuracy of my analysis. THANK YOU.
Why does ceiling your crawl save energy? Take a look at this video on The Stack Effect. It show cases Spray Foam but the underlying theme is sealing your home air tight as possible is the best for energy efficiency. Similar to you driving in your car with the windows down as apposed to closing them more and more for more efficiency.
Click here for a Sealed Crawl Before and After with pictures and video