[Title 24 CFR 3280.509]
[Code of Federal Regulations (annual edition) - May 1, 2001 Edition]
[Title 24 - HOUSING AND URBAN DEVELOPMENT]
[Chapter Xx - OFFICE OF ASSISTANT SECRETARY FOR HOUSING--FEDERAL HOUSING]
[Part 3280 - MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS]
[Subpart F - Thermal Protection]
[Sec. 3280.509 - Criteria in absence of specific data.]
[From the U.S. Government Printing Office]


24HOUSING AND URBAN DEVELOPMENT52001-05-012001-05-01false3280.509Sec. 3280.509HOUSING AND URBAN DEVELOPMENTOFFICE OF ASSISTANT SECRETARY FOR HOUSING--FEDERAL HOUSINGMANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDSThermal Protection
Sec. 3280.509  Criteria in absence of specific data.

    In the absence of specific data, for purposes of heat-loss/gain 
calculation, the following criteria shall be used:
    (a) Infiltration heat loss. In the absence of measured infiltration 
heat loss data, the following formula shall be used to calculate heat 
loss due to infiltration and intermittently operated fans exhausting to 
the outdoors. The perimeter calculation shall be based on the dimensions 
of the pressure envelope.

Infiltration Heat-Loss=0.7 (T) (ft. of perimeter), BTU/hr.

where: T=70 minus the heating system capacity certification temperature 
stipulated in the Heating Certificate, in F.

    (b) Framing areas.


Wall.....................................  15 percent of wall area less
                                            windows and doors.
Floor and Ceiling........................  10 percent of the area.
 

    (c) Insulation compression. Insulation compressed to less than 
nominal thickness shall have its nominal R-values reduced for that area 
which is compressed in accordance with the following graph:

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When insulation is installed over the framing members the thermal 
performance of the insulation is reduced due to compression at the 
framing members. The Resistance value of the insulation between the 
framing members is reduced by 12.5 percent for framing members 16" O.C., 
8.5 percent for framing members 24" O.C., and 4 percent for framing 
members 48" O.C.
    (d) Air supply ducts within floor cavity. Air supply ducts located 
within a floor cavity shall be assumed to be heating or cooling the 
floor cavity to living space temperatures unless the duct is 
structurally isolated by the framing system or thermally insulated from 
the rest of the floor cavity with a thermal insulation at least equal to 
R-4.
    (e) Air supply ducts within ceiling cavity. Where supply ducts are 
located in ceiling cavities, the influence of the duct on cavity 
temperatures shall be considered in calculating envelope heat loss or 
heat gain.
    (f) The supply duct loss (and/or heat gain where applicable--See 
Sec. 3280.511) shall be calculated using the actual duct surface area 
and the actual thickness of insulation between the duct and outside of 
the manufactured home. If there is an air space of at least \1/2\ inch 
between the duct and the insulation, heat loss/gain need not be 
calculated if the cavity in which the duct is located is assumed to be 
at living space temperature. The average temperature inside the supply 
duct, including ducts installed outside the manufactured home, shall be 
assumed to be 130 F for purposes of calculation of heat loss and 60 F 
for heat gain.
    (g) Return air cavities. Cavities used as return air plenums shall 
be considered to be at living space temperature.