COLUMN BUILDING SCIENCES
FIGURE 12 A hybrid approach for basement foundations can also be used in com-
bination with fiberglass or cellulose insulation.
FIGURE 13 Vented crawlspaces must keep air and vapor out of the crawlspace floor
framing. Only high-density closed-cell spray polyurethane foam should be used in
all IECC Climate Zones.
High-Density Closed-Cell
Spray Polyurethane Foam
HD Spray Foam
2×6 Advanced Frame Wall
Cellulose or Spray Fiberglass
Floor Sheathing
(Plywood or OSB
Any Type of
Flooring/Floor Finish
Sealant
Water Control Layer
Protection Board
Capillary Break
HD Spray Foam
2×4 Advanced Frame Wall
Cellulose Cavity Insulation
Concrete Foundation Wall
House Wrap Protection Layer
Bond Break
Capillary Break
Concrete Slab
Damp Proofing
Filter Fabric
Coarse Gravel
(No Fines)
Perforated
Drain Pipe
Capillary Break Over Footing
(Damp Proofing or Membrane)
Concrete Footing
FIGURE 14 A protection board such as fiber cement should be installed to prevent
animals from getting into the floor assembly.
Cladding
Air Gap
Wood-Based Sheathing
(Plywood or OSB)
Water Control Layer
Spray Polyurethane Foam
Acrylic Latex Paint
Gypsum Board
Sealant
High-Density Closed-Cell
Spray Polyurethane Foam
Protection Board
Polyethylene Vapor Barrier
Granular Capillary Break and
Drainage Pad (No Fines)
damper is open and the HVAC system blower is operating.
Foundations
Basement foundations are best insulated on the interior thereby avoiding issues with respect to insects such
as ants and termites, issues with respect to protecting
exterior insulation during the construction process, and
protecting exterior insulation above grade during the
life of the building.
Spray foam insulation can be directly applied to the
interior of concrete foundation walls (Figure 11). In IECC
Climate Zones 5 and higher high density closed cell
spray foam is recommended. A hybrid approach can also
be used in combination with fiberglass or cellulose insulation (Figure 12).
There are two common crawlspace foundation
approaches -the crawlspace is either "vented" and
"not conditioned" and connected to the "outside" or the
crawlspace is "not vented" and "conditioned" and connected to the "inside." Of the two approaches, the most
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FEBRUARY 2020
energy efficient is the not-vented conditioned approach.
However, not all sites are compatible with not-vented
conditioned crawlspaces such as areas with high water
tables, swamps and flooding concerns.
Vented crawlspaces must keep air and vapor out of the
crawlspace floor framing. Only high-density closed-cell
spray polyurethane foam should be used in all IECC
Climate Zones (Figure 13 and Figure 14). A protection board
such as fiber cement should be installed to prevent animals from getting into the floor assembly.
Conditioned crawlspaces should be constructed as
"mini" basements and completely connected to the
house (Figure 15). We looked at how to condition crawlspaces previously ("Crawlspaces: Either In or Out,"
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