Untitled Document

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New Definitions

Wall Vented Crawl Space – Section R408
A foundation that uses foundation wall vents as a primary means to control moisture. Insulation under the floor above

Closed Crawl Space – Section R409
A foundation without wall vents that uses air sealed walls, ground and moisture control, and mechanical drying potential

Conditioned Crawl Space – Section R409
A foundation without wall vents that encloses an intentionally heated/ cooled space. Insulation at the walls.

General Requirements all Crawl Spaces

R408.1.4- All drains and dryer vents should terminate outdoors and be separate from gutters and foundation drains
R408.3- If outside grade is higher than inside grade, the exterior should be dampproofed from the top of the footing to the finished grade per R406.1
R408.4- Building site graded to drain water away from crawl space foundation per R403.1
R408.8- Min. crawl space access is 18”x 24”
R408.9- Clean crawl space floor of all vegetation and organic material. Remove wood forms and construction materials prior to occupancy.
R408.6- Seal all penetrations through the subfloor with sealants – not rockwool or fiberglass.
R408.7- Seal all ductwork in the crawl space with mastic or other approved system

R408 renamed Wall Vented Crawl Spaces

Ground vapor retarders required w/ drainage
Vented crawls separated from basements, porches & garages
Floor and crawl duct sealing specified

R318 Foam Plastic Insulation

In attics (where entrance is only for service of utilities), foam plastic protection required:
   – 1 ½-inch particleboard
   – ¼-inch hardboard
   – 3/8-inch gypsum board
   – Corrosion-resistant steel having a base metal thickness of 0.016 inch
Within crawl spaces, foam plastic use is governed by R409.8.2

408.1.1 Vented Crawl SpacesMinimum Vent Area

Net area of ventilation openings not less than 1 square foot per 150 square feet of crawl space ground area
Exception: Vent area may be reduced to 1/1500 when the required openings are placed to provide cross-ventilation; operable louvers are prohibited.

R408.1.2 Foundation Vent Location

1 vent placed within 3 feet of each corner of the building
To prevent rainwater entry in a crawl space built on a sloped site, the uphill foundation walls may eliminate wall vent openings
Vent dams when the bottom of the foundation vent opening is less than 4” above the finished exterior grade

R408.1.3 Covering Material

To prevent rodent entry, foundation vents may be covered with any of these materials
     – Perforated sheet metal plates not less than .07”
     – Expanded sheet metal plates not less than .047”
     – Cast iron grills or grating
     – Extruded load-bearing brick vents
     – Hardware cloth .035” wire or heavier
     – Corrosion-resistant mesh at least 1/8” thick

R408.1.5 Space Separation

Wall vented crawl spaces should be separated from adjoining basements, porches and garages by a permanent solid wall with all utility penetrations sealed
Latched, weather stripped doors or access panels provide entry to the crawl space and adjoining spaces

R408.2 Ground Vapor Retarders

Required for all wall vented crawl spaces
Minimum 6-mil polyethylene or equivalent over exposed earth with the joints lapped more than 12”
It is acceptable to puncture the plastic at low spots for drainage
Earth shall be sloped to a low spot

R409.1- Air Sealing

R409.1- Seal holes through foundation walls for supply and return ducts to outdoor packaged HVAC equipment, if used.
R409.1.1- Use air sealing caulk, gaskets or sealants on the foundation wall and floor assemblies that separate the crawl space from the outside and other ventilated areas

R409.2.1- Polyethylene Ground Cover

R409.2.1- Install a minimum 6-mil polyethylene vapor retarder or equivalent over exposed earth in crawl space, with joints lapped more than 12”
Grade the crawl space floor so that it drains to 1 or more low spots
Install a drain to daylight or sump pump at each low spot-- separately from gutter or foundation drains

R409.2.2 Full Interior Liners

Ground vapor barrier can serve as full interior liner by sealing edges to the walls and beam columns
Stop top edge of wall liner 3” below top of foundationwall
Bring top edge of wall liner up interior columns or piers at least 4” above crawl space

R409.2.1.1 Inspection Gap at Top

Provide a clear and unobstructed 3” minimum inspection gap between the top of the wall liner and the bottom of the wood sill.
Ignore possible energy penalty posed by gap.

R409.2.3 - “Rat Slabs”

The ground vapor retarder may be protected against ripping and displacement by pouring an un-reinforced, minimum 2” thick, concrete surface directly over the vapor barrier.
Gravel not required
Floor should be graded to drain to one or more low spots

409.5 Closed Crawl Space Moisture Vapor Control Options

Permanent dehumidifier
–  with electric outlet in crawl space
–  minimum capacity of 15 pints/ day
–  drain conden-sate to daylight or interior pump
Supply air
–  1 cfm per 30 sq ft; backdraft damper required
–  No return air open to crawl space
–  Not considered a plenum air distribution system
House air
– 1 cfm per 50 sq ft; fan rated for continuous duty
Exhaust fan
– 1 cfm per 50 sq ft; fan rated for continuous duty
Conditioned space with insulated walls
–  Return air allowed
–  Foam plastic insulation on walls must be protected by
    approved thermal barrier

409.6 Crawl Spaces as HVAC Plenums

Must meet NC Mechanical Code
No plumbing cleanouts, gas lines, other prohibited components
Foam plastic insulation on walls must be protected by approved thermal barrier

409.7 Combustion Air in Sealed Crawl Spaces

Fuel burning appliances such as furnaces and water heaters shall obtain combustion air from outside

409.8.1 Closed Crawl Spaces, Foundation Wall Insulation

Where the floor above a closed crawl space is not insulated, thewalls shall be insulated. Wall insulation can be located on any combination of the exterior and interior surfaces and within the structural cavities or materials of the exterior crawl space walls.

Wall insulation systems require that the band joist area of the floor frame be insulated. Wallinsulation shall begin 3 inches below the top of the masonry foundation wall and shall extend down to 3 inches above the top of the footing or concrete floor, 3 inches above the interior ground surface or 24-inches below the outside finished ground level, whichever is less. No insulation shall be required on masonry walls of 9 inches height or less.

R409.8.1.1 Foam plastic termite inspection gap.
For outside wall Section R324 governs applications. When expanded polystyrene, extruded polystyrene, polyisocyanurate, or other foam plastic insulation is installed on the inside surface of the exterior foundation walls, provisions R409.8.1.1.1 – 2 below apply.

R409.8.1.1.1 Earth floored crawl spaces. Provide a clear and unobstructed 3-inch minimum termite inspection gap between the top of the foam plastic wall insulation and the bottom of the wood sill. Because Insulation ground contact is not allowed, provide a continuous 3-inch minimum clearance gap between the bottom edge of the foam plastic wall Insulation and the earth floor surface.
Refer to N1102.1.7 to determine maximum allowances for insulation gaps.

R409.8.1.1.2 Concrete floor surfaced crawl spaces.
Provide a clear and unobstructed 3-inch minimum termite inspection gap between the top of the foam plastic wall insulation and the bottom of the wood sill. Provide a continuous 3-inch minimum clearance gap between the bottom edge of the
foam plastic wall Insulation and the concrete floor surface. Refer to N1102.1.7 to determine maximum allowances for insulation gaps.

R409.8.1.2 Porous insulation materials. When fiberglass, rockwool, cellulose or other porous insulation materials are installed on the inside wall surface of a closed crawl space, provide a clear and unobstructed 3-inch minimum termite inspection gap
between the top of the porous wall insulation and the bottom of the wood sill. To reduce wicking potential, porous insulation ground contact is not allowed in earth floored or concrete surfaced crawl spaces. Provide a continuous 3-inch minimum wicking gap between the bottom edge of the porous wall Insulation and the earth or
concrete floor surface. Refer to N1102.1.7 to determine maximum allowances for insulation gaps.

R409.8.2 Foam Plastic Fire Safety

Foam plastic insulation may be installed inside crawl spaces
without a thermal cover barrier or ignition barrier when the insulation product has been tested in accordance with ASTM E 84 have a flame spread rating of not more than 25 and a smoke developed rating of not more than 450 section R318.3. foam plastic tested in accordance with section R318.3 shall be installed according to the limitations stated in the ICC Evaluation Service Evaluation Report (ICC-ES) for the product. Foam plastics that have not been tested to meet these ratings shall be protected against ignition by covering them with a thermal barrier.

Acceptable thermal barriers include but are not limited to ½-inch cement board, metal foil sheets, metal foil tape, steel or aluminum metal sheets or other approved materials installed in such a manner that the foam is not exposed per section R318.2.3.

Exception:
Foam plastic insulation located in closed crawl spaces used as conditioned spaces as defined in section R409.5.5 Conditioned Space or section R409.6 Plenums shall be protected against ignition by an approved thermal barrier.