[Bldg-sim] ASHRAE 90.1 "HC" heat capacity

[Seth P. Spangler]

Hello,

 

ASHRAE defines a mass wall as a wall having a heat capacity (HC) of
greater than 7 BTU/ft2 * F but I have been unable to find this property
listed in tables of building materials. I am trying to calculate the
heat capacity of a CMU wall and would like to confirm that my
calculation methodology is correct.

 

Per ASHRAE 1997 Fundamentals:

*         8" concrete block - two cores filled with concrete (normal
weight) - ~130 lb/ft3

*         Thickness .67 ft

*         Specific Heat ~ 0.22 BTU/lb * F

 

Therefore NC =(130 lb/ft3 )*(.67 ft)*(0.22 BTU/lb * F)

 

NC=19.16

 

Using this methodology even a 4" brick wall has a HC greater than 7 (7.5
to be exact).

 

Thanks in advance.

 

Seth Spangler, LEED(r) AP 

Project Engineer

 

RMF Engineering, Inc 

Ph: (843) 971-9639 ext:1497

Fax: (843) 971-9641 

sspangle at rmf.com

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