ZEMCH 2015 - International Conference Proceedings | Page 760

Thermal Mass in Walls
Thermal mass is the capability of fabrics to save heat. It can be integrated into a building as part
of the buildings components in the walls and floor. High thermal mass materials, such as concrete, brick, stone and earth, can absorb and hold heat and release it slowly later on when there
is a temperature difference between the material and the surroundings (Light House Sustainable
Building Centre and Guido 2009). It is suggested to use high thermal mass materials in building
components in hot regions, as this provides a comfortable indoor environment by reducing indoor air temperatures and avoiding overheating in summer (Kasmai 2008). Based on Givoni and
Kruger (2008), using high thermal mass materials in external walls keep the indoor air temperatures in the acceptable condition in winter period as it absorb heat of the surrounding in the
day time and release it slowly at night. In this study various thermal mass materials with different
thicknesses were applied to the simulation model (Table 4).
Table 4: Thermal mass materials using different thicknesses in external wall components
Thermal Mass

Thickness (cm)

Brick (base case)

30

Brick

20

Heavy concrete

25

Heavy concrete

40

Medium concrete

25

Medium concrete

40

Light concrete

25

Light concrete

40

Figure 8 shows that the application of thicker high thermal mass resulted in lower reduction in
indoor air temperatures in both classrooms. Based on the literature, the impact of thermal mass
is increased by increasing thermal density and decreasing the thickness of the material which
causes more constant heat capacity. A thinner density of mass material responds faster to surface
temperature fluctuations and consequently will store excess heat gains and dampen interior air
temperatures more effectively (Byrne and Ritschard 1985; Autodesk Sustainability Workshop 2011;
Fehr 2009). It is also essential to locate thermal mass in direct solar radiation, for it to have more
impact on indoor air temperatures (Autodesk Sustainability Workshop 2011; Nasrollahi 2009).
In addition, it can be seen that using light-weight and med-weight concrete increases indoor air
temperatures in both classrooms. Based on Rise and Holm (2004), using lightweight concrete in
a building’s envelope cause longer time lags. In addition, Vangeem et al (2013) reported that reducing the density of the concrete masonry walls results in increasing thermal lag. They cited that
for external uninsulated concrete walls, the beneficial effects of thermal mass are increased as
density is reduced from 2400 kg/m³ to 800 kg/m³, which might be a possible reason for the higher
temperatures seen when using light-weight concrete masonry walls compared to heavyweight
concrete. However, it is suggested to use heavy-weight thermal mass material with thicker thickness in order to reduce the indoor air temperature in warm season to avoid overheating.

758

ZEMCH 2015 | International Conference | Bari - Lecce, Italy