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HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
*
Fig. 2.3: Pre 1977 temperatures in a standard house (90/70/20 °C)
30
28
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24
22
20
18
16
14
12
10
0
Cold and
not pleasant
Still Pleasant
Pleasant
Too hot
10 12 14 16 18 20 22 24
t Aw
= 12 o C
t F
= 0 o C
t HKm
= 80 o C
t A
= -14 o C
inlet= 90 o C
return= 70 o C
*
Fig. 2.5 – EnEv 2009 (45/35/20 °C)
30
28
26
24
22
20
19
18
17
16
14
12
10
0
Cold and
not pleasant
Still Pleasant
Pleasant
Too hot
10 12 14 16 18 20 22 24
t Aw
= 19 o C
t F
= 17 o C
t HKm
= 40 o C
t A
= -14 o C
inlet= 45 o C
return= 35 o C
t R
= room temperature
t R
= 20 o C
t R
= room temperature
t R
= 20 o C
*
Fig. 2.4. EnEV2002 (55/45/20 °C)
30
28
26
24
22
Still Pleasant
Pleasant
Too hot
20
t Luft
= -20 o C
18
17
16
Cold and
14
not pleasant
12
10
0
10 12 14 16 18 20 22 24
t R
= room temperature
t Aw
= 18 o C
t F
= 14 o C
t HKm
= 50 o C
t R
= 20 o C
t A
= -14 o C
inlet= 55 o C
return= 45 o C
The walls in Fig. 2.5 are almost at room temperature. Even
the windows are warm, despite the freezing exterior. Notice
that the radiator output now needs only to reach a mean
water temperature of 40 °C to achieve this ideal scenario
– 50% less than the same building insulated according to
the standards of Fig. 2.3.
* Thermal Comfort: There are several standard criteria; here are some:
• the average value air temperature and mean surface temperature is
around 21°C.
• The difference between air temperatures and mean surface temperatures
varies by no more than 3°C.
• The difference between mean surface temperatures in opposite direction
varies by no more than 5°C.
• The average temperature between head and ankle heights are less than 3°C.
• The air velocity in the room less than 0.15 m/s.
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