[Greenbuilding] Slab heat loss calculation

nick pine nick at early.com
Sat Aug 24 04:44:42 CDT 2013


RT <archilogic at yahoo.ca> writes:

>... In putting our pants back on frontwards, someone noticed that we had 
>all received tattoos onto our backsides:
>
> ? ? ? ? ? "? q? =? A [ dT ( K/s + hc ) +? ( ? * T^4 ) ]? "

How do you estimate slab heat loss?

After lots of finite difference network ground loss calculations Professor 
Kelly Kissock at U Dayton 
http://academic.udayton.edu/kissock/http/EEB/Energy%20Efficient%20Buildings_1.htm 
says an A ft^2 slab on US Rf foamboard with Rp vertical perimeter insulation 
down "to the footer" would have an approximate 
A(0.1140/(4+Rf+Rp)+0.8768/(16+Rp)) Btu/h-F conductance from the room air 
temp to the 4 meter deep ground temp.

For example, a 900 ft^2 slab on R10 foamboard with R15 perimeter insulation 
would have a 900(0.1140/(4+10+15)+0.8768/(16+15)) = 29 Btu/h-F conductance 
from a 65 F room air temp to a 58 F deep ground temp, so the room would lose 
(65-58)29 = 203 Btu/h to the slab.

How much would this change with different perimeter insulation depths?

Nick 





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