MANUFACTURED HOMES

MA 1.0—Introduction

The definition of a Manufactured Home is “a structure, transportable in one or more sections” and “is built on a permanent chassis and 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 (HUD).

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.

MA 1.2—General Requirements for Insulating Roofs

Requirements for insulating ceilings and roofs in manufactured homes are the same as for site-built homes. See AT and AT 3.5 Sections for requirements.

Illustration MA 1.2

MA 1.3—Blowing Underfloor Insulation

MA 1.4—Preparation

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 1.4

MA 1.5—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.

MA 1.6—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 1.7—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 due to climate and ground water conditions is not considered excessive, Home Energy Solutions may allow operable louvers and may allow the required net area of vent opening to be reduced to 1/300 or less (minimum 1/1500), provided the underfloor ground surface area is covered with an approved ground cover.

Illustration MA 1.7

Openings shall be located as close to corners as practical and shall provide cross ventilation. The required area of such openings shall be approximately equally distributed 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 inch in dimension. Existing vent openings that are covered with wire mesh do not need to be modified.

Contractors may approve mechanical ventilation when passive ventilating methods are not practical. If crawlspace ventilation cannot be accomplished in accordance with these requirements, underfloor insulation shall not be installed.

MA 1.8—Ground Covers

If an existing ground cover does not meet Home Energy Solutions 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. There shall be no rips, tears or gaps.

MA 1.9—Installing Batt Insulation in Underfloors

Refer to the UNDERFLOORSsection 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: Home Energy Solutions 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 1.10—Replacement Windows

Window requirements for manufactured homes are the same as for site built homes. See Section WI.

MA 1.11—Duct Insulation and Sealing

Refer to Duct Insulation and Duct Sealing sections in Home Energy Solutions specifications.

Illustration MA 1.11

MA 1.12—Maximum Air Tightness

After house air sealing, air tightness shall be no less than 8 ACH50.

MA 1.13—Mechanical Ventilation

If the ACH is below the recommended level of 8 ACH50, a mechanical ventilation system shall be installed in all mobile homes.

MA 1.14—Non-Heat-Recovery Ventilation—Intermittent Operation

A bathroom exhaust fan is controlled by both a manual switch, crank timer or dehumidistat in the bathroom to provide spot ventilation AND a time clock to provide whole-house ventilation when called for by the timer. Outside-air inlets in all living areas and bedrooms, and undercut doors, grilles, transoms, or other approved means, provide fresh-air circulation through the house to the bath fan.

Exhaust ducts shall be smooth metal and terminate outside the house at the closest possible location. All connections shall be tight fitting and taped or sealed, and backdraft dampers shall be provided.

The minimum exhaust airflow rates shall comply with either the performance OR prescriptive paths listed below. Surface-mounted fans shall have a sone rating of 1.5 or less, or other rating as approved by the Contractor. Existing fans that meet the minimum airflow rates are exempt from the sone rating requirement.

Performance Path: The minimum measured airflow capacity shall be either 0.35 air-changes per hour (ACH) or those listed below:

Table MA 1.14A

To calculate the ACH for a fan with a MEASURED airflow of 45cfm, multiply by 60 to obtain the airflow per hour (45 X 60 = 2700 cfh) and divide by the volume of the heated space.

Prescriptive Path: Ventilation systems that do not meet the performance path shall provide 0.35 ACH based upon the rated fan flow minus 15 cfm or use the rated fan flows in the following table:

Table MA 1.14B

To calculate ACH based on the RATED airflow, subtract 15 cfm, multiply by 60, and divide by the volume of the heated space.

The fan shall have both automatic and manual controls. Automatic controls shall include a time clock or cycle timers with a minimum of 2 on-periods per day, a manual control switch to let the occupant turn the fan on or off, and be set to operate a minimum of 8 hours per day. The ventilation fan shall be wired to both the manual spot-ventilation switch in the bathroom and to a time clock.

Individual outside-air inlets, located to avoid drafts, shall provide a minimum of 4 sq. inches per bedroom and combined living area. The outside-air source shall be located at least 3 feet from exhaust vents and to minimize drawing outdoor pollutants and excessive outdoor noise inside during operation. The outside-air source shall limit excessive airflows during normal operation and have a weather protection hood and maximum ¼ screen-mesh, or as approved.

MA 1.15—Unbalanced Non-Heat-Recovery Ventilation—Continuous Operation

This system uses a continuously operating fan to exhaust air at a minimum rate of 25 cfm for the kitchen, and 20 cfm for each bathroom, with a maximum rate of 0.5 ACH. One fan exhausting from the kitchen and each bathroom shall also provide spot ventilation. An integrated spot and whole-house fan is acceptable if spot ventilation is also provided for the kitchen and for the bathrooms. The continuous ventilation fan(s) shall be wired to an existing circuit or to the electrical service panel.

The exhaust-air pickup in the kitchen shall not be over the kitchen range. If the exhaust flow from each kitchen and bathroom is not measured, the rated fan capacity shall exceed the required flow rate by a minimum of 15 cfm.

The outside-air inlet and source requirements shall be the same as in Section MA 12.1.

MA 1.16—Balanced Flow Non-Heat Recovery Ventilation—Continuous Operation

Balanced flow non-heat-recovery air exchange units shall:

• Have fans capable of providing the intake and exhaust airflow rates in Section MA 12.1 at 0-25 inches of water gauge as determined by HVI 916 (July 1993).
• Provide complete isolation of the intake and exhaust air.
• Have UL approval of all electrical components.
• Have outside-air inlets in all living areas and bedrooms, positioned to avoid drafts. Inlets must be installed according to the manufacturer’s instructions

MA 1.17—Air-to-Air Heat Exchangers

Air-to-air heat exchangers shall:

• Provide the ventilation rates in Section MA 12.1.
• Have a minimum sensible heat recovery efficiency of 65 percent at 117 cfm and 32F for homes larger than 1,300 sq. ft. and 55 percent at 64cfm and 32F for houses of 1,300 sq. ft. or less, as certified by the Home Ventilation Institute (HVI).
• Have a filter on the upstream side of the heat exchanger in both the intake and exhaust airstreams.
• Provide protection against ice buildup that does not disable the unit during freezing weather, and be installed according to manufacturer's instructions.

MA 1.18—Other Mechanical Ventilation Systems

Other mechanical ventilation systems may be used if approved by Home Energy Solutions.