Closed Crawl Spaces

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Closed Crawl Spaces Sealed Attics
Applied Building Science Team Shaun Hassel Bruce
Davis
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Understanding the Problems and Solutions
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Session Overview

• Definitions
• Group Activity
• Facilitated Discussion
• Selected AE Research and Case Studies
• Resources are at www.crawlspaces.org

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Overview

• If someone is going to build a house on a crawl
  space, why would they want to close it? Why
  wouldnt they want to close it?
• If someone is going to construct a house, why
  would they want to seal the attic? Why wouldnt
  they want to seal the attic?
• If they do decide to utilize one of these
  approaches, how should they do so?

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What is a Closed Crawl Space?

• NC Code Definition
• A foundation without wall vents that uses air
  sealed walls, ground and foundation moisture
  control, and mechanical drying potential to
  control crawl space moisture. Insulation may be
  located at the floor level or at the exterior
  walls.
• Why call it Closed?
• Unvented vs. Sealed vs. Conditioned vs. Closed

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What is a Sealed Attic?

• 2006 ICC Residential Code
• Unvented conditioned attic assemblies are
  permitted under the following conditions
• 1. No interior vapor retarders are installed on
  the ceiling side (attic floor) of the unvented
  attic assembly.
• 2. An air-impermeable insulation is applied in
  direct contact to the underside/interior of the
  structural roof deck.
• 3. In warm humid locations with asphalt roofing
  shingles A 1-perm or less vapor retarder is
  placed to the exterior of the structural roof
  deck that is, just above the roof structural
  sheathing.
• 4. In Zones 3 through 5 (all of NC), sufficient
  insulation is installed to maintain the monthly
  average temperature of the condensing surface
  above 45F (7C). The condensing surface is
  defined as either the structural roof deck or the
  interior surface of an air-impermeable insulation
  applied in direct contact with the
  underside/interior of the structural roof deck.
  For calculation purposes, an interior temperature
  of 68F (20C) is assumed. The exterior
  temperature is assumed to be the monthly average
  outside temperature.

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Group Activity
Break into four groups, each representing an
approach vented crawls, vented attics, closed
crawls, sealed attics.

• Provide
• Reasons to utilize your approach
• Obstacles to overcome

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Crawl Space Owners

• Insulation
• Plumbing
• Electrical Mechanical
• Gutters
• Landscaping
• Information Services

• Builder
• Owner
• Installer
• Code Official
• Pest control
• Grading/Drainage
• Foundation

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Attic Owners

• Insulation
• Plumbing
• Electrical Mechanical
• Gutters
• Information Services

• Builder
• Owner
• Installer
• Code Official
• Framer
• Roofer
• Drywaller

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The Crawl Space Ventilation Myth
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2004 Crawl Space Characterization Study
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2004 Characterization Study

• 67 of crawl spaces had WMC gt 19
• 22 had wood rot NOT caused by plumbing leaks
• 24 had wood rot caused by plumbing leaks
• Typical 6 x 12 hole to the house
• Stack pressure and HVAC driving forces
• Very high bioaerosol levels Crawl spaces are
  MADD!

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The Princeville Project

• NETL, 2001-05
• Bill Warren, Cyrus Dastur
• Technology Assessment
• Characterization Study
• Field Demonstration
• Hygrothermal Modeling

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Princeville, NC Field Study Site
Princeville, NC Field Study Site
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Phase II June 2003-June 2004
Closed Sealed liner R-19 Floor
Closed Sealed liner R-13 Wall
Wall vented R-19 Floor
Wall vented R-19 Floor
Closed Sealed liner R-19 Floor
Closed Sealed liner R-13 Wall
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Closed Crawl Space Supply Air Duct
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Phase II Crawl Space Dew Points
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Phase II Crawl Space Relative Humidity
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Phase II Average Wood Moisture Content
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Seasonal Energy Use and Savings
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Princeville Study Conclusions

• CCS provides improved moisture control
• CCS delivers significant energy savings with
  either floor or wall insulation
• CCS is feasible to install and maintain
• Performance was achieved with designs that
  isolate the crawl space from the living space

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Healthy Homes, Healthy Lives

• What is the connection between housing, health,
  and the construction process?
• High Performance Homes (20)
• Closed crawl
• Enhanced air filtration
• Tight envelope
• Properly installed insulation
• Minimal duct leakage with outside air ventilation
• Versus Code Built Homes (16)

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Doing the right thing wrong
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Key Design and Installation Issues

• Combustion safety
• Fire safety
• Radon control
• Mold control

• Moisture control
• Pest control
• Drying
• Insulation

• Performance verification
• Worker Safety

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Download AEs Introduction toClosed Crawl Spaces
at

• www.crawlspaces.org

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The Spray Foam House

• A typical production house in the Southwestern
  United States slab, stucco, ceramic tile
  shingles, 1700 sq. ft, gas heat with A/C
• Spray foam blown in the unvented attic and walls
• EFL house with right sized HVAC unit with minimal
  duct leakage (lt 3) and fresh air ventilation
• Sensors throughout the attic, exterior walls, and
  living space

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YTD Hourly Mean Attic Space Conditions
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YTD Difference Between Attic and T-Stat
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One Week Hourly Temperature Average Attic vs
Thermostat
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YTD Daily Wood Moisture Readings for Bedroom vs.
Roof Locations
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24-Hour Hourly Mean NE Roof Deck Profile
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Sealed Attic Case Study

• An unvented attic in the Southeastern United
  States
• Built on a closed crawl space
• Utilized fiberglass insulation in combination
  with manual air sealing techniques caulk guns
  cans of spray foam

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There is No Silver Bullet
Successful implementation requires
Process
Training
Design
Product