Retrotec USACE - Manual (Page 361)

H1
Appendix H
Building Energy Balances
A building energy balance helps the energy auditor identify and account for
all building energy inputs and outputs. Energy balances may be calculated or
measured.
There is one major difference in calculated and measured building energy
balances:
The calculations have to assume certain conditions on climate, usage, ■
and system operation, so they calculate energy demand under these con-
ditions.
The measurements on the other hand take into account the actual
■
conditions, including ineffi ciencies of systems, errors in operation
and wrong usage. Therefore, what we measure are consumption data
(metering) and quantities to calculate loads (e.g., temperatures or ven-
tilation airfl ows).
H.1 How to Determine Heating Loads
An energy balance (kW, kWh) is expressed by the following equation:
Q
∑
= Q
loss
+ Q
inf
+ Q
vent
+ Q
hw
+ Q
int .load
where
Q
∑
= heating load brought into a building from external sources
Q
loss
= losses of heat through the building envelope, kW
Q
inf
= heat losses due to infi ltration
Q
vent
= thermal load on ventilation,
Q
hw
= thermal load on hot water supply
Q
int .loss
= internal thermal emissions, including heat recovery from exhausted air