CABO One and Two Family Dwelling Code and Model Energy Code - 1995 editions and the federal Manufactured Home Construction and Safety Standards University of Illinois at Urbana-Champaign School of Architecture-Building Research Council Principal Authors:
  • Jeffrey Gordon
  • William B. Rose
  Graduate Research Assistants:
  • Ellen Colfax
  • Amy J. Isenburg
  • Troy Pavelka
  • Anthony Vivirito
  • Vince Webber
  December, 1997 This summary is based on a comprehensive comparison of the 1995 CABO One and Two Family Dwelling Code, the 1995 Model Energy Code, and the federal Manufactured Home Construction and Safety Standards (MCHSS). There are many similarities in these codes, along with minor differences of slight consequence, and some differences of notable consequence. On balance, the codes are comparable. The following tables are intended to summarize the notable differences between the codes that were identified in the comprehensive comparison. The bold text indicates the code with the more restrictive requirement. For the purposes of this report, a "more restrictive" requirement is one that is more limiting of design discretion; it does not imply a value judgment. GENERAL Subpart A of MHCSS, and Chapter 1 of CABO, cover the administration of the respective building codes. Because the codes relate to distinctly different modes of construction (factory-built vs. site-built), there is little basis for comparison in this subpart. The nature of the CABO code requires additional provisions relating to submission of plans, permits and posting, authority to enter, site inspections, and liability for code officials. Both codes provide provisions for:
  • Incorporation of referenced standards.
  • Use of alternate construction.
  • Waivers.
  • Civil and criminal penalties for code violation.
Planning Considerations Including Portions of Fire Safety The following table is intended to summarize the notable differences
Light and Ventilation
CABO
MHCSS
Does not allow kitchens to have artificial light in place of windows. Allows kitchens to have artificial light in place of windows.
Requires half of required glazing to be operable, except when a mechanical ventilation system capable of supplying 15 CFM is provided. Requires half of required glazing to be operable regardless of mechanical ventilation requirement.
Mechanical ventilation may be omitted in bathrooms with 1.5 sf of operable glazing. Requires all full bathrooms and separate toilet compartments to have mechanical ventilation.
Does not require kitchen ventilation to vent to the outdoors. Allows unvented range hoods. Requires kitchen ventilation capable of providing 100 CFM to the outdoors. Exhaust fan must be located within 10' of range or cook top.
 
Room Sizes and Ceiling Heights
CABO
MHCSS
Room sizes and heights:
  • Habitable rooms not less than 70 sf.
  • Minimum dimension in habitable room not less than 7'.
  • In habitable rooms, ceiling height not less than 7'-6" over 50% of room area. Remaining area 5', minimum. Beams, girders, and ducts may not project more than 6".
Room sizes and heights:
  • Habitable rooms not less than 50 sf.
  • Minimum dimension in rooms not less than 5'.
  • In habitable rooms, ceiling height not less than 7' over 50% of room area. Remaining area 5' minimum. Minimum height under duct and beams not less than 6'-4".
 
Glazing
CABO
MHCSS
Requires safety glass on glazed panels within 24" of the arc of a door in the closed position. Requires safety glass on glazed panels within 12" of a door.
Requires safety glass in any panel greater than 9 sf, whose bottom edge is less than 18" from the floor, and is within 36" of a walking surface. MHCSS does not address.
Exempts a mirror mounted or hung on a door. Requires safety glass in unbacked mirrored wardrobe doors.
Does not require shutters or other protective coverings for windows or doors in high wind zones. Requires walls, window and door surroundings be designed for placement of shutters or other protective coverings in high wind zones.
 
Exits, Doorways and Egress
CABO
MHCSS
Requires no less than one conforming exit, with no requirements on the location of the exit. Requires no less than two exterior exits, and limits the distance from any bedroom to the nearest exit to 35'.
Conforming exit doors no less than 3' wide and 6'-8" tall. Hallways no less than 3' wide. Conforming exit doors no less than 2'-4" wide and 6'-2" tall. Hallways no less than 2'-4" wide.
CABO does not address. Egress doors not to be located in a room with a lockable interior door. Includes several other provisions relating to required hardware for interior and exterior doors.
On windows designed for emergency egress, sill height no more than 44" high. CABO does not limit height of operating hardware, or require operating instructions posted on the window. On windows designed for emergency egress, sill height must be no more than 36" high, with operating hardware not more than 54" high. Operating instructions must be permanently posted on the window. Each bedroom must have an egress window or an exterior door.
 
Smoke Detectors
CABO
MHCSS
Requires 1 smoke detector in each bedroom. Requires 1 smoke detector in each bedroom area.
Requires smoke detectors to be interconnected, and to have a battery backup. MHCSS does not address.
 
Fire Resistance
CABO
MHCSS
Limits the use of foam plastic sheathing to 1/2" thick, and requires no less than 2" mineral wool insulation and 1/2" gypsum wallboard covering. Limits the use of foam plastic sheathing to 3/8" thick, and requires no less than 2" mineral wool insulation and 5/16" gypsum wallboard covering.
Limits the use of foam plastic interior trim. Does not limit the use of foam plastic interior trim.
Limits smoke density of interior finishes to 450. Does not address smoke density of interior finishes.
Limits flame spread classifications of walls and ceilings to 200. Does not address other configurations. Limits flame spread classifications of walls to 200 and ceilings to 75. Provides additional flame spread ratings for specific components of kitchen and bathrooms.
CABO does not address. Requires "limited combustible materials" adjacent to cooking ranges (maximum flame spread rating of 50), and doors and enclosures around furnaces and water heaters (maximum flame spread rating of 25).
Requires flame spread rating of 75 or less and smoke-developed rating of 450 or less for foam plastic thermal insulating materials. Requires additional spread ratings and smoke density factors for types of insulation materials other than foam plastic. Requires flame spread rating of 75 or less and smoke-developed rating of 450 or less for foam plastic thermal insulating materials.
The following list highlights some of the areas where the codes are comparable or slightly different: Lighting requirements for habitable rooms; Space requirements for toilet compartments; Safety glazing in exterior door, showers and bath enclosures; and Smoke detector labeling requirements.
Body and Frame Construction Requirements The following table is intended to summarize the notable differences
Structural Loads
CABO
MHCSS
Design live load for sleeping rooms is 30 psf. Design live load for entire unit is 40 psf.
No concentrated load requirement. Floors shall be able to support a one-inch diameter 200 pound concentrated load.
No additional wind resistance requirements for eaves and cornices. Eaves and cornices are designed to withstand wind loads. For any hurricane-prone location, MHCSS assigns a higher design wind speed than CABO.
The following list highlights some of the areas where the codes are comparable or slightly different: Structural design - floor systems; Fastening floor framing; Structural design - wall frame construction; Exterior coverings; Roof assemblies; and Windstorm protection - anchoring.
Thermal Protection The following table is intended to summarize the notable differences
U-factor
CABO
MHCSS
Complicated formulas for walls, roofs and floor system U-factor. Simple requirements by zones for overall U-factor. For single-section sized unit built to MEC requirements, the Uo is similar to the Uo for MHCSS, especially in Zone 1.
Requires accounting for "thermal bridging" in metal framing. MEC provides specific design tables and correction factors to be used in calculations for metal frame construction. Metal framing is not specifically called out. MHCSS does require adjustment of Uo for framing losses, including "thermal shorts," but does not provide specific adjustments. References 1989 ASHRAE Fundamentals.
 
Window Construction
CABO
MHCSS
Uses ASTM E283 to determine window airtightness, requiring 0.5 cfm per lineal foot of crack. Uses ASTM E283 (referenced in AAMA 1701.2-85 1.4.2.2) to determine window airtightness, requiring 0.5 cfm per square foot of window area. MHCSS thus requires tighter windows than CABO for normal sizes of windows. (ASTM 283-84 permits results reported using either square footage of window area or lineal feet of crack length).
 
Airtightness
CABO
MHCSS
Requires treatment against air leakage at utility penetrations. Recessed light fixtures must meet airtightness standards. No airtightness standards for recessed light fixtures; however, other electrical, mechanical, and plumbing penetrations must limit air infiltration.
 
Vapor Retarders
CABO
MHCSS
Requirements for vapor retarders use wet bulb temperatures. Ceiling vapor retarders are required in thermal zones 2 and 3. Walls require vapor retarders, permeable sheathing or cavity ventilation.
 
Attic Ventilation
CABO
MHCSS
Attic ventilation required. Requires attic ventilation except: 1) Single-section homes with metal roof having no sheathing and a tight ceiling. 2) Parallel membrane roof section of a closed cell type.
The following list highlights some of the areas where the codes are comparable or slightly different: Certification Requirements for window U-values; Limitation on envelope air infiltration; Heat loss/gain calculation; and, Minimum roof ventilation area in the roof cavities.
Plumbing Systems The following table is intended to summarize the notable differences
Temperature Control
CABO
MHCSS
Requires temperature control valves for showers and tub faucets. MHCSS does not address.
 
Horizontal Drains
CABO
MHCSS
Requires minimum slope of 1/4 unit per 12 unit fall. MHCSS allows 1/8 unit per 12 unit fall, when 1/4 unit fall is impractical due to structure, but requires a full size clean-out at the upper end of reduced-slope piping.
 
Sidewall Vent
CABO
MHCSS
Permits vents to extend through wall or building overhang and terminate downward. Does not allow sidewall venting - must use mechanical vents or terminate above roof.
The following list highlights some of the areas where the codes are comparable or slightly different: Requirements for water flushing devices; Faucets and diverters installation; Water outlets and supply connection; Requirements for solder firings; Water supply protection; Piping materials; Drainage systems; Venting and traps; and, Requirements for temperature and/or pressure relief valve.
Heating, Cooling, and Fuel Burning Systems The following table is intended to summarize the notable differences
Fireplaces, Fireplace Stoves and Fireplace Chimneys
CABO
MHCSS
CABO does not address. Fireplaces and stoves must be equipped with integral doors and labeled, "For use with solid fuel only."
Does not restrict fireplace or stove locations. Prohibits fireplaces and stoves in sleeping rooms.
Requires combustion air passageways to be a specified dimension, and the intake protected with 1/4" screen. MHCSS does not address.
Combustion air inlet may be within 24" of the firebox on or near the floor. Combustion air inlet must be connected directly into the firebox.
CABO does not specify spark arresters, and has no height requirements for factory-built chimneys. (Has height requirements for mansonry chimneys). Factory-built chimneys must be equipped with spark arresters, and extend 3' above the roof, and 2' above the highest elevation of the home within 10' of the chimney.
 
Clearances
CABO
MHCSS
CABO does not address. Provides requirements and dimension specifications to prevent, or warn against, storage of combustible materials around heat-producing appliances.
CABO does not address. Prohibits doors or drapes to be placed where they could swing inside listed clearances.
 
Controls
CABO
MHCSS
Requires gas and oil appliances to have a shut-off valve in the event of pilot or ignition failure. Requires shut-off feature through referenced standards (ANSI Z-21.47 and UL 307-b). Requires furnaces to be third-party listed to referenced standards.
Requires a temperature limit control to prevent outlet air from exceeding 250 degrees F in forced air furnaces. Requires temperature limit control through referenced standards (ANSI Z-21.47 and UL 307-b). Requires surface temperature of the furnace not to exceed 90 degrees F above room.
 
Duct Systems
CABO
MHCSS
Requires class 0 or class 1 ducts for those portions closer than 3' from the outer casing of the appliance. Limits duct linings or coverings to a flame spread of 25, and a smoke density rating of 50. Requires class 0 or class 1 ducts for those portions closer than 3' from the outer casing of the appliance, 2' in the case of return ducts.
CABO does not address. Requires pressure testing to determine airtightness.
CABO does not address. All rooms must be served by return air ducts, or be provided with "uncloseable openings" (grilles, etc).
CABO does not address. Floor registers or grilles must be able to resist structural failure in a 200 lb. concentrated load test.
 
Combustion Air and Venting
CABO
MHCSS
Allows combustion air supply to be entirely from the interior, exterior, or a combination of both, based on the airtightness of the home. Requires the complete separation of combustion air and interior air, by 1.) direct vent appliances, OR 2.) installatin in enclosures sealed from interior air.
Oil-fired appliances are required to have a draft regulator connected to the chimney. MHCSS does not address.
 
Air Conditioning
CABO
MHCSS
Piping must be insulated to prevent condensation. MHCSS does not address.
CABO does not address. On combination systems, requires dampers and controls to separate and prevent simultaneous operation of heating and cooling systems. Heat pumps must provide 60% of annual heating by compression.
AC systems to have EERs between 9.7 and 10.0. AC systems to have EER of not less than 7.2.
Heat pumps to have a coefficient of performance of 2.9 (47 degrees F) and 2.0 (17 degrees F). Heat pumps to have a coefficient of performance of 2.5 (47 degrees F) and 1.7 (17 degrees F).
 
Fuel and Gas Piping and Storage Systems
CABO
MHCSS
Gas piping systems are visually inspected, but are not required to be pressure tested. Requires pressure testing of gas piping systems to inspect for leakage.
Allows used materials in gas piping systems. Does not allow used materials in gas piping systems.
Each gas appliance requires a separate shut-off valve. Shut-off valves may serve more than one appliance under certain conditions.
Allows plastic piping and fittings in gas piping. Does not allow plastic components in gas piping.
Joints in concealed locations must be brazed. Does not allow joints in concealed locations, and prohibits tubing inside walls, floors, or in roofs.
CABO places less emphasis on some aspects of LP-gas systems. MHCSS places more emphasis on LP-gas systems, specifying connectors, safety devices, service pressure, construction of containers, and mountings.
CABO places more emphasis on fuel oil systems, specifying tank materials, types of pumps, and maximum pressure of fuel lines. MHCSS places less emphasis on some aspects of fuel oil systems.
CABO does not address. Fuel oil systems must contain an oil filter, and be tested for leakage prior to operation.
The following list highlights some of the areas where the codes are comparable or slightly different: Appliance accessibility for inspection; Requirement for duct material; R-values for duct insulation; Venting requirements for fuel burning appliances; Requirement for gas shut-off valves conformance; Identification of gas supply connections; Labeling; Supply and return air; Water heaters; and, Prohibition of gas piping as an electrical ground.
Electrical Systems While CABO contains a comprehensive electrical code (chapters 39-46), it also references and allows all methods and materials contained in the 1993 National Electrical Code (NEC). MHCSS contains a limited comprehensive electrical code, Subpart I, and references the 1993 NEC for most materials and methods. For this reason, CABO and MHCSS are generally equivalent based on their common references to the NEC. The following table is intended to summarize the notable differences.
CABO
MHCSS
Testing CABO does not address. MHCSS requires that the wiring in each home receive a dielectric strength test, a continuity test, an operational test and polarity checks.
Conductors Allows aluminum conductors and components under some conditions. Does not allow aluminum, aluminum alloy, or aluminum core conductors within the house or for general purpose circuits.
Service Size Typically requires 100-amp service and 60-amp service in some cases with smaller loads. A minimum of 40- or 50-amp service is permitted, but entrance service must be sized for calculated connected load which may require higher capacity.
Outdoor Receptacles Requires at least one outdoor receptacle at grade level in both the front and back of a home. Requires only one outdoor receptacle. Requires a second, dedicated outdoor receptacle near the water supply inlet under the home for the use of a heat tape.
Bathrooms CABO does not address. Prohibits receptacles within 30" of a shower or bathtub.
Hallways Requires at least one receptacle in hallways 10' or longer. Hallways exempted from receptacle requirements.
Bonding Requires bonding for electrical equipment and metal water piping system. Requires bonding for electrical equipment and other metallic parts that could become energized (e.g. non-electric devices such as ducts, metal framing, etc.).
Service Wiring The grounded circuit conductor (neutral) is connected to the grounding conductors (ground), a 3-wire system. The grounded circuit conductor (neutral) is isolated from the grounding conductors (ground), a 4-wire system.
Kitchen Receptacle Spacing Requires placement of receptacle at each countertop 12 inches or greater in length. Provides for a maximum of 4-feet spacing between countertop receptacles. Requires placement of a receptacle at each countertop 12 inches or greater in length. Requires receptacle above coutertop on each side of sink.
Bathroom Lighting CABO does not address. Lighting fixtures over bath tubs or shower stalls shall be of the gasketed and enclosed type.
Copyright 1997 Manufactured Housing Institute and the Board of Trustees of the University of Illinois. All rights reserved.
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