MA 1.0—Introduction
A manufactured home is defined as a structure, transportable in one or more sections, built on a permanent chassis, designed to be used as a dwelling with or without a permanent foundation when connected to the required utilities, and includes the plumbing, heating, air-conditioning, electrical systems contained therein (source: Part 3280, Manufactured Home Construction and Safety Standards, Oct. 1994). For purposes of this specification, the definition of manufactured homes will also include older homes manufactured in factories and hauled over the road to the home site, and regulated by U.S. Department of Housing and Urban Development, or HUD. Please refer to the current Program Information sheet (PI 320F) for manufactured and existing mobile home incentives.
Air and duct sealing on existing mobile homes with non-permanent foundations is only permitted if trade ally is a Participating Contractor in the Existing Mobile Homes program. Contact the Existing Mobile Homes program at 1.866.365.3526 option 5 for more information.
A functioning UL-listed carbon monoxide detector shall be installed according to manufacturer’s specifications whenever combustion appliances are present in the manufactured home, existing mobile home, garage or other attached space.
MA 1.1—Verifying R-Values
If the existing R-value of the roof and floor cannot be verified, a default R-value may be used unless an actual value can be observed during weatherization work.
Illustration MA 1.1
MA 1.2—Blowing Underfloor Insulation
Preparation
Existing Homes recommends sealing ducts before installing underfloor insulation. Belly board or belly wrap shall be repaired to prevent insulation from falling from floor cavity. Repair materials shall be stitch-stapled to the belly board, or otherwise permanently affixed. Plumbing leaks shall be repaired and decayed wood flooring shall be replaced.
Illustration MA 1.2
Materials
Materials used to patch the belly board shall be breathable, durable and capable of supporting the insulation. Expanding foam or other sealants shall be used to seal accessible floor penetrations.
Installation
Underfloor cavities shall be insulated either by drilling small holes in the belly board or by drilling through the rim joists perpendicular to the floor joists. If holes are drilled through the belly board, they shall be patched. Holes drilled in the rim joists shall be patched with wooden plugs.
The entire floor cavity shall be packed with insulation in order to achieve an R-25 minimum, or the highest R-value practical.
MA 1.3—Ventilation
Crawlspaces shall be ventilated by openings in exterior foundation walls. Such openings shall have a net area of not less than 1 sq. ft. for each 150 sq. ft. of underfloor area. Where moisture is not considered excessive due to climate and ground water conditions, Existing Homes may allow operable louvers and may allow the required net area of the vent opening to be reduced to 1/300 or less (minimum 1/1500), if the underfloor ground surface area is covered with an approved ground cover.
Illustration MA 1.3
Openings shall be located as close to corners as practical and shall provide cross ventilation. The required area of such openings shall be distributed equally along the length of at least two opposite sides. Vents shall be covered with corrosion-resistant wire mesh, with mesh openings of no greater than ¼" in dimension. Existing vent openings covered with wire mesh do not need to be modified.
Contractors may approve mechanical ventilation when passive ventilation methods are not practical. If crawlspace ventilation cannot be accomplished in accordance with these requirements, underfloor insulation shall not be installed.
MA 1.5—Ground Covers
If an existing ground cover does not meet Existing Homes specifications, it shall be repaired or a new ground cover shall be installed. New ground covers shall be a minimum of 6-mil black polyethylene. All joints shall be lapped at least 12 inches. The cover shall be continuous throughout the crawlspace and there shall be no rips, tears or gaps. Refer to UN 1.4 for complete ground cover specifications.
MA 1.6—Installing Batt-Type Insulation in Underfloors
Refer to the Underfloor section of this manual for underfloor specifications. Once the belly board is removed, the techniques used to insulate a manufactured home underfloor are the same as with site-built homes.
Note: Existing Homes does not provide incentives for the cost of removing or replacing an existing belly board. State or local code may require belly boards on manufactured homes.
MA 1.7—Replacement Windows
Window requirements for manufactured homes are the same as for site-built homes (see Section WI).
MA 1.8—Duct Insulation, Duct Sealing and Air Sealing
Ducts shall be sealed according to PTCS specifications for manufactured homes. Duct runs that extend beyond the last heat register away from the heat source and terminate with folding the duct metal shall be sealed just behind the last register. Sealing the duct run can be accomplished using duct board or metal plugs cut to fit tightly and must be sealed with mastic. Rigid foam is acceptable if it is UL-181 listed.
All other duct sealing, duct insulation and air sealing shall comply with appropriate sections in this manual for detailed specifications.
Air and duct sealing on existing mobile homes with nonpermanent foundations is only permitted if trade ally is a Participating Contractor in the Existing Mobile Homes program. Contact the Existing Homes program at 1.866.365.3526 option 5 for more information.
Illustration MA 1.8
MA 1.9—Maximum Air Tightness
See the MV section.
MA 1.10—Mechanical Ventilation
Mechanical ventilation shall comply with Section MV in this manual when air sealing is installed in an existing mobile home.