The R-factor for housing insulation gives the thermal resistance in units of ft2 °F h/BTU. A good wall for harsh climates, corresponding to about 10 in of fiberglass, has R = 45 ft2 °F h/BTU.

Question

a) Determine the thermal resistance (in m2 K/W) in SI units.
b) Find the heat flow per square meter through a wall that has insulation with an R-factor of 45, with an outside temperature of -21.1 °C and an inside temperature of 24.1°C.

Answer 1

dQ/dt= dTemp/R= 45.2/45 Btu/hr

a. 1 ft^2 F hr/BTu= Lord chaning units..

1m^2=10.76ft^2
1 BTU=1055 joule
1 watt= 3600Joule/hr

ok, then 1 BTU/hr=1055*3600/hr

now for the conversion

1ft^2(1m^2/10.76ft^2)*F*(9K/5F)/(1055*1036 W/hr)

and you can check that, and multiply it out.

Answer 2

it's wrong i think, i cannot understand