Clay-ver - To build with what is under our feet

Page 26

CLAY & INDOOR CLIMATE THERMAL COMFORT

Body heat lost

Body heat produced

Body heat produced

Body heat lost

Body heat lost Cold feeling

Warm feeling Body

Body

lost

produced

Figure 17. Thermal balanceheat(By the author) heat Body heat produced

Body heat lost

Clothes thermal resistance (m2°C/W) 0.1 0.2

0

0.3

3.0

90%

10°C 12°C 14°C

80%

2.0

Body heat produced 26°C

1.0

28°C ±1°C

70%

16°C 18°C 20°C

60% 22°C 24°C

50%

Body heat lost

±4°C ±3°C

40% 30%

100

Active (W/m2)

PPD

PPD : Predicted Percentage of Dissatisfied Thermal comfort ±5°C Mean 150Vote PMV : Predicted

±1.5°C

20%

±2°C

1.0

±2.5°C

50

2.0 Clothing (Clo)

10% 0%

-3 -2 -1 0 1 2 Figure 18. Optimal operative temperature (Fanger, O., 1970)

Cold

Cool

Slightly cool Comfortable Slightly warm

Warm

3 Hot

PMV

90%

PPD

Humidity

Body heat produced

Thermal comfort

VENTILATION DEPENDANT

Air velocity

Cold feeling

Warm feeling

Metabolism (Met)

The most important vital parameter for a good indoor climate is thermal comfort, and it is also the one for which clay has the most positive effect. Thermal comfort depends on different parameters shown in Figure 16. (Nilsson P.-E., 2003) Humidity and radiant temperature can be effectively improved with the use of clay, and the strategies developed later in the testbed are based on these parameters. The air temperature depends on the internal and external heat gain and is therefore related to the insulation of the building and the heating system. Earth materials are poor insulators, however when mixed with fibers, they get better (Minke, G., 2009). Finally, the air speed is more dependent on the ventilation and the building’s airtightness, on which clay do not have much effect. Thermal comfort is difficult to describe and involves many parameters. The main condition for feeling comfortable is that the heat exchange between the body and its environment is balanced, Figure 17. Ole Fanger has developed a way to determine the optimum temperature for an environment by evaluating user satisfaction. His theory considers that “acceptable thermal comfort” is reached when there are no more than 20% dissatisfied and that in all case, it will always have about 6% dissatisfy, Figure 19. He explains that the thermal comfort zone depends not only on the temperature of a room but also on the metabolic heat and the insulation of people’s clothes, Figure 18, which explains why it is such a subjective parameter and why it is difficult to satisfy everyone (Nilsson P.-E., 2003).

PPD : Predicted Percentage of Dissatisfied PMV : Predicted Mean Vote

80%

Air temperature

70% 60% 50% 40%

Clothing insulation USERS DEPENDANT

Users parameters

Metabolic heat

OPERATIVE TEMP.

Environmental parameters

Figure 16. Thermal comfort parameters (By the author, Data from Nilsson P.-E., 2003)

24

30%

Radiant temperature

20% 10% -3 Cold

-2 Cool

0% -1 0 1 Slightly cool Comfortable Slightly warm

2 Warm

3 Hot

PMV

Figure 19. Acceptable comfort zone (Fanger O., 1970)

Clay-ver, To build with what is under our feet - Mathilde Grunacker


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