Thermal protection in buildings
directly influences the use of energy for heating and cooling, as
well as the ability to control the room climate at comfortable levels.
Any heavy material has the ability to absorb, store and gradually
release heat. This property is commonly referred to as thermal mass.
One of the most important benefits of thermal mass in house construction
is its ability to moderate temperature extremes.
Thermal protection for winter conditions is intended to minimise
the heat loss from the building, thus allowing the building to be
economically heated. Furthermore, the internal surfaces of the external
elements, such as walls and ceilings, should not drop below a certain
minimum temperature in order to avoid condensation. When the outdoor
temperature is cold, heat from the sun (and also from heaters) can
be stored in high mass elements of a building. This heat is gradually
released into the home once the energy source is no longer available.
In this way the mass is effectively acting as a heater long after
the original source of heat has gone.
In contrast, the thermal protection for summer conditions is intended
to minimise heat gain from the warm outside temperatures and sun
rays, thus allowing the internal environment to be economically controlled
in a comfortable state.
Thermal protection in summer is mainly determined by the capability
of the exterior building elements to store and dissipate heat. This
property is determined by the mass and thermal conductivity of the
building material. The thermal mass and thermal conductivity establish
the thermal inertia, which causes a damping and time lag of the temperature
peaks. In other words the mass absorbs heat from the sun and stores
it. As the heat is stored in the mass, the air in the room is not
heated as much as in a lightweight building.
The heat is only released into the building when the room temperature
drops below that of the mass.
The structure of CELCRETE AAC optimally combines the material properties
necessary to provide excellent thermal energy efficiency for a building
and additional thermal protection is not required except where the
veneer block and veneer panel products are used. A 200mm CELCRETE
block wall outperforms conventional wood frame and concrete masonry
construction for thermal efficiency (equivalent R value). This exceptional
thermal efficiency is achieved by a very low thermal conductivity
(U value) along with the thermal mass effect. This is a distinct
benefit of AAC construction over other conventional building systems.
The R value of a 200mm thick uncoated CELCRETE wall with 9.5mm of
plasterboard directly fixed to it is 1.6 as compared with the minimum
requirement of .60 for solid walls in Climate Zones 1 and 2.