[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 DEVELOPMENT52001-05-012001-05-01falseCriteria in absence of specific data.3280.509Sec. 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:
[GRAPHIC] [TIFF OMITTED] TC17OC91.006
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
(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
(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.