Superinsulation is the most effective weapon we have against wintertime heat losses. R-values of 60 or more in the roof and 40 in exterior walls can slow the movement of heat to a crawl, keeping energy costs far below what they’d be in a conventionally built house.
Yet Harry Seidel puts his finger on a potential problem. During the summer, any heat generated inside the house will have just as much trouble getting out of the house.
In a Q&A post at GreenBuildingAdvisor, Seidel wonders about the impact of running a Therma-Stor dehumidifier in a basement utility room of a superinsulated house in New Hampshire. The dehumidifier solves one problem but may create another.
“My question is in regard to the potential for the slab assembly in the house mentioned above to absorb and mitigate the heat generated?” he writes. “Given the sub-slab insulation [R-19], will this cause the basement to heat up? I could be wrong, but was told that 1 pint of water removed equates to 1,000 BTU of heat.”
“In N.H. and much of [New England] we have relatively high humidity in the summer months (trust me, it’s a problem) and a fresh-air delivery system (Renewaire ERV), although able to reduce moisture somewhat, achieves this by simply exchanging ambient exterior air for interior air,” he adds. “In our summers this will be useless and the house’s design is tight enough that moisture will prevail. It will build up and be a menace.”
Among the options he’s considering is the elimination of insulation below the utility-room slab to create a more effective heat sink for the dehumidifier.
Is there another approach that would be more effective? Or is Seidel anticipating more trouble than he’ll actually…