Civil Engineering Reference
In-Depth Information
where Q
tr
is the total heat transfer by transmission and Q
ve
is the total heat transfer
by ventilation.
As established by the UNI EN ISO 13790, for the monthly and seasonal
methods, the total heat transfer by transmission, Q
tr
, is calculated for each month
or season and for each zone and it depends on the overall heat transfer coefficient
by transmission and on the monthly mean external and internal temperatures,
defined at national level.
Moreover, for natural ventilation in residential buildings, Q
ve
is defined at
national level by UNI/TS 11300 part 1 and calculated using the ventilation rate
default value of 0.3 vol/h.
The total heat gain, Q
H,gn
, of the building zone for a given calculation step are
calculated using
Q
gn
¼
Q
int
þ
Q
sol
ð
3
Þ
where Q
int
is the sum of internal heat gains and Q
sol
is the sum of solar heat gains
over the given period.
The heat gains from internal heat sources are determined for residential
buildings (national indications) as
/
int
¼
5
:
294A
f
0
:
01557A
f
½
4
Þ
where A
f
[m
2
] is the internal floor area of the conditioned space.
The energy performance calculation presented in the chapter is carried out by a
simulation tool which implements the UNI/TS 11300.
Once determined the building energy need for space heating, Q
H,nd
,itis
necessary to calculate thermal losses and electrical consumption of each heating
subsystem:
• Emission subsystem;
• Control subsystem;
• Distribution subsystem;
• Storage subsystem and
• Generation subsystem.
It is possible to determine thermal losses for each subsystem by virtue of
simplified or detailed procedures. Simplified methods provide for obtaining effi-
ciencies from conventional values depending on subsystem typology, while
detailed procedures allow us to calculate distribution losses through the length and
the thermal transmittance of each pipe and also generation losses using values
declared by the manufacturer or measured.
For example, emission subsystem thermal losses Q
l,e
is
Q
l
;
e
¼
Q
H
;
nd
1
g
e
g
e
ð
5
Þ
where g
e
is the corresponding efficiency.
