I am working, doing audits, with a contractor who tends to make basements, crawlspaces into conditioned space. Especially when all or most of the duct work is in the crawlspace. He does this by covering the floor, side walls and piers with heavy plastic. He then uses rigid foam insulation on the walls, foams the joints and above and seals the vents and access hatches. Then we duct seal and re-insulate.
Has anyone been doing this for a while? Any unentended consquences?
Well, there are so many factors to review with your local code enforcement:
1. 3" gap at top of insulation from foundation wall
2. insulation offset from ground
3. appropriateness of foam board insulation in crawlspace (Thermax, for example, seems to be appropriate across NC, but other states require any foam board to be covered for flame spread, etc.)
4. method of conditioning the space. dehum, hvac, return air from home.
Most of the experts (EPA, DOE, Advanced Energy) recommend conditioning an encapsulated crawlspace using 1CFM per 50 sq ft of crawlspace area from existing ductwork if available. We find that is more cost effective than buying and running a dehumidifer. Of course, sometimes ductwork isn't available and you have no choicebut to install a dehumidifier. In any case, most local codes require conditioning the space. The subject is addressed on our web site. wwww.yourcrawlspace.com
As always, check your state code. If you're using HVAC air, you may be required to insulate the walls of your crawl space. That could lead to higher initial costs than just getting the dehumidifier.
While insulated and conditioned with HVAC air is the ideal, it's not always the best solution. Tapping into an existing supply line to condition the crawl is robbing air from the living space, and can put more stress and wear on an existing unit. Also, in some situations it's undesirable to create that slightly positive pressure in the crawl helping lift air into the living space.
In cold climates using the HVAC system to condition the crawl space is in most cases the best way to provide the comfort factor the homeowners expect from a new system. Leaving the crawl space unconditioned leaves the floors cold that can lead to higher setting on the thermostat, uncomfortble seating for the kids on the floor, and generaly less comfort in the home. We always size off the heat/gain calculations to handle the extra load.
I'm curious if anyone has data on conditioned crawlspaces in mild climate zones, like California. It seems all of the responses listed are from areas with more temperature/humidity extremes.
To my knowledge no, though I do have to laugh at "mild climate" & California as that state falls under 7 different climate zones & recall dealing with roads closed due to snow in June.
Like almost everything it depends on where your mechanicals are, location and other factors - got a specific location in mind?
While we are at it - what does Title 24 call for - as I recall they had some info or reqs in there
Should have qualified our location. Climate Zone 2, Santa Rosa where we had 1580 HDD in 2011 and have 1453 HDD to date.
So given "our mild climate zone," does anyone have data that supports the additional expense for a conditioned crawlspaces?
TWO-PART WEBINAR SERIES: California Crawl Spaces: Integrated Solutions for Healthy Homes & Deep Energy Reductions: http://thousandhomechallenge.com/thc-webinars-retrofitting-ca-crawl...
Great and surprising information.
sounds awesome! probably helps keep down radon as well
Actually the one study I know of pulled the plug on a house in Flagstaff due to Radon levels increasing because it lost the dilution ability of a vented crawl. With that said depending on your area it still can be worth doing & just making sure you install radon control measures via a rat slab or something similar
I have a conditioned crawl space. I think it is well worthwhile. You can read more about why I like it here: http://www.greenspirationhome.com/?p=1033