ASHRAE Journal - April 2020 - 25

TECHNICAL FEATURE

conditioned air circulates behind the insulation in
batt-insulated ﬁnished basements under winter stack
pressures in Canadian and northern U.S. houses
and buildings, increasing heating costs more or less
commensurately.
Typical batt and foam board-insulated ﬁnished basements may not only be wasting winter heating energy,
their insulation systems may also be hiding winter condensation and bringing damp envelope concrete and
cellulose microbial off-gassing and allergenic aerosols
and soil air contaminants into the living space where
they can only be addressed by costlier and less-efﬁcient
whole-house ventilation and ﬁltration systems.
This heat loss and potential air contamination warrants the attention of building code-setting bodies and
agencies promoting building energy conservation and
the beneﬁts of healthy and efﬁcient ﬁnished basements
in homes.
The solution described for the stack-induced airﬂow
problem and for foundation leakage damage mitigation has worked for the many installations built over
the last three decades. The solution has kept basements
odor-free and comfortable and the envelope materials
dry. And, it has conserved winter heating energy, provided an air barrier to soil gas entry, and solved foundation leakage and sewer backup problems. The solution
described is approved as a foundation drainage system
and, if used in a retroﬁt, solves foundation leakage problems without costly exterior excavation.
The cost to operate the blower continuously is about
$10 to $20 annually, and blowers are typically lasting
20 years or more under continuous operation. This
ventilation removes typical basement envelope and soil
gas air pollutants with a small amount of ventilation
air, something a standard heat recovery ventilator cannot do as completely with a much larger ﬂow rate. It is
energy-efﬁcient ventilation as the air exhausted from
the basement gives up a portion of its heat as it passes
through the insulation envelope, and the basement air
that replaces it comes from aboveground inﬁltration air
that has absorbed some of the house radiant heat loss.
Home builders should consider developing the tools and
skills necessary to seal and depressurize the envelope
adequately. This solution has been used in other applications including creating common wall air barriers
around smoking rooms and between contaminated and
occupied aboveground spaces.

Sprayed on foamed-in-place insulation over interior
foundation walls will prevent conditioned air from
traveling behind foundation insulation. However, it
is expensive, requires ﬁre-rated drywall over it, and
makes retroﬁtting electrical outlets and bathroom
vent pipe outlets difﬁcult. Further, unlike the solution
proposed in this article, it does not solve a foundation leakage problem without the need to dig outside
the foundation to seal cracks. Neither can it mitigate
sewer backups. Finally, if there is a ﬁre, post-ﬁre odor
cleanup is more difﬁcult. Hence, its use is mainly limited to sealing and insulating foundation walls above
the sill plate, and insulating envelopes where ﬂooding
has occurred.

References

1. 2005 ASHRAE Handbook-Fundamentals, 27.12.
2. 2009 ASHRAE Handbook-Fundamentals,
16.14.
3. California State University. 2014. Center
for Energy and Environmental Research and
Services split unit prototype code.

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ASHRAE Journal - April 2020

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