Heat Loss Calculation

ApacheCalc – Heat loss/gain calculations using CIBSE procedures to determine design heating/cooling loads.
ApacheLoads – Design heating/cooling loads calculations using ASHRAE Heat Balance Method.
mech student
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Heat Loss Calculation

Postby mech student » Wed Oct 07, 2015 5:13 pm

Hi there,

I am carrying out a heat loss calculation and I noticed that my IES results are different from the hand made calcs.

Could anyone give me any ideas of reasons that this might be happening?

Also, the table that Apache Loads gives doesn't mention anything about heat losses? Is the 'steady state heating load' column the heat loss calc?

I would really appreciate any of your feedback.


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Re: Heat Loss Calculation

Postby Terence » Wed Oct 14, 2015 5:26 pm

Is your hand calculation Q=U.A ΔT?

CIBSE Loads uses a more rigorous calculation than this that looks at environmental temperatures etc – As mentioned in the Apache Calc (CIBSE Loads) method document in the user guides area, this is as described in appendix 5A of the 1995 edition of CIBSE Guide A. From this, fabric heat loss is determined by the difference between outside environmental temperature (assumed to equal air temperature) and room environmental temperature (not room air temperature).
Terence McMahon
IES Technical Support

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