Water storage in conditioned crawl space
We are about to build a conditioned crawl space (IFCs,sub-slab EPS, with venting to single storey living space) and land two high-performance modular units on the foundation. Our drought-impacted southern Oregon property (4C) has limitations on construction of open ponds, but we are looking at using military water bladders for storage of water catchment from barn and house roofs. The house will include blown cellulose in 2×6 framing with 2″ Agepan exterior insulation and Hardi-plank siding. We will blow the attic to R-60 and heat/cool with 2 mini-splits, each about 22,000 BTU.
I’m considering designing the crawl to accommodate three large water storage bladders, each holding about 8,000 gallons of rainfall or grey water for agricultural use. We likely will collect water in the winter and spring and use it all by summer’s end. I don’t plan to circulate the water for direct or indirect gain, but do you folks think that this sealed thermal mass will increase the demand on the heating system?
The military quality bladder tanks will be hard plumbed and should–with no exposure to UV, freezing, falling limbs or critters–have a life span of 20 or more years. What am I not thinking of ?
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Alan,
I don't think that the heat needed to bring the temperature of rainwater up to the ambient temperature of your crawl space will be enough to notice. The water will warm slowly.
If I were you, I would go to a lot of pains to provide good drainage in this crawl space. I would probably spec a slab floor with one or more large-diameter drains leading to daylight. Then I would install a layer of crushed stone on top of the slab, followed by your bladders. When these tanks begin to leak, as they eventually will, you need to be prepared.
Agreed that you should plan such that if they spring a leak, it's not a disaster. Keeping a crawlspace 100% critter free is hard, among other things.