ASHRAE Journal - May 2021 - 56

COLUMN BUILDING SCIENCES

Reduce Interior Water/ Moisture Availability
Pests tend to love water. Sound familiar? We already
talked about reducing exterior water. We also need to
reduce interior water/moisture availability. Too much
interior water/moisture results in interior mold, insects,
rodents and mites. During air-conditioning periods
interior humidity should be maintained at 60% or
less. During heating periods interior relative humidity
should be limited to 35% or less during the coldest parts
of the winter-unless the house is designed to be able
to withstand higher interior relative humidities during
cold periods.
Dust mites require relative humidities of 70% or
higher. Dust mites can colonize carpeting installed
on cold surfaces such as uninsulated basement ﬂoor
slabs. Cold slabs increase the relative humidities of
adjacent surfaces. Cold carpets are an ideal breeding
ground for dust mites. Interior humidity should be
controlled. Install dehumidiﬁers in basements. Use
dehumidiﬁers to address part-load humidity issues in
energy-efﬁcient houses. Dust mites can colonize furniture and clothing. Washing items in hot water (greater
than 130°F [54°C]), can kill dust mites and wash away
allergens.

Reduce Food Availability
Keep kitchen waste in covered containers. Don't leave
food out. Clean dishes. Don't pour grease down drains.

Control Dust
Dust contains asthma triggers. Over two-thirds of
dust in homes originates outdoors and is tracked in on
feet. House dust is known to contain many hazardous
materials. Dust should be stopped at the door. Remove
shoes and provide a place for shoes at the door. Provide a
welcome mat and keep the welcome mat clean. Vacuum
surfaces regularly. Vacuums with high-efﬁciency ﬁltration are recommended. Make the home easy to clean.
Don't clutter homes.

FIGURE 9 Externally insulated slab-on-grade foundation constructed using a
monolithic concrete slab/grade beam. In " heavy " termite infestation regions
borate-treated lumber framing and insulation should be used. The termite shield
needs to extend outward past the exterior edge of the exterior slab edge insulation and its associated protection layer a minimum of ¾ in. (19 mm) to impede
the ability of termites to bridge the shield. This also facilitates visual inspection of
the effectiveness of the termite shield. Additionally, a removable strip of insulation
and protection board providing an inspection gap is recommended.

Continuous Exterior Insulation
Cladding
Rodent Protection for
Continuous Rigid Insulation
Removable Strip of Insulation
and Protection Board
Cellular PVC Protection Board

Cavity Insulation
Gypsum Board
Termite Shield Set in Mastic (Also
Serves as Capillary Break)
Sill Gasket
Sealant, Adhesive or Gasket
4 in. Concrete Slab

For Pest Protection Provide
2 ft of Pea Gravel or
Crushed Stone 4 in. Thick

Ground Slopes Away From Wall at
5% (6 in. per 10 ft)
Rigid Insulation

4 in. Granular Capillary
Break and Drainage Pad
(No Fines)
Concrete
Grade Beam
Polyethylene Vapor Barrier Extended
Under Grade Beam Where it Also
Acts as a Capillary Break

professionals who spe- PHOTO 6 Plumbing and other services that
penetrate concrete slabs are sealed with a
cialize in integrated
stainless steel mesh " skirt " clamped to the
pest management
service penetration. The mesh is subseshould be used. Do not quently cast into the concrete.
inject pesticides into
wall and building cavities-except boric acid.
Inter-species chemical warfare should be
avoided wherever possible. You don't want
Dr. Strangelove* doing
the work. Done recklessly it can result in a
mad outcome-mutual assured destruction.

Bibliography

Don't Do Stupid Things
Don't do stupid things. Of course this is the most
difﬁcult strategy to implement. We tend to be inherently stupid. Don't use moth balls. Moth balls release
chemicals that are unhealthy. If pesticides are necessary,

Geiger, C., C. Cox. 2012. " Pest Prevention by Design:
Authoritative Guidelines for Designing Pests Out of Structures. "
San Francisco Department of the Environment. https://tinyurl.
com/9v6d554w
Lstiburek, J.W., T. Brennan. 2001. " Read This Before You Move
In. " Building Science Corporation. https://tinyurl.com/56pzb6uy

*A 1964 satirical ﬁlm by Stanley Kubrick. " Dr. Strangelove " was played by Peter Sellers. It is considered one of the greatest ﬁlms of all
time. One of the best lines in the ﬁlm was, " Gentlemen, you can't ﬁght in here. This is the War Room! "
56

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ASHRAE Journal - May 2021

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