MHE International

Autoclaved Aerated Concrete - Material Advantages - Thermal Efficiency

  • R-20 equivalent without additional materials
  • Lower energy costs
  • Out performs wood and concrete masonry construction
  • Provides air-tight controlled ventilation

An 8 inch AAC - wall out performs conventional wood frame and concrete masonry construction for energy efficiency (equivalent R-value). This exceptional energy efficiency is achieved by a very low thermal conductivity (U-value) along with the thermal mass effect. This is a distinct benefit of the AAC aerated concrete construction over other conventional building systems such as wood frame and concrete masonry construction.

In order to compare the AAC - exterior wall with conventional wall construction methods - wood stud frame and concrete masonry, the Florida Solar Energy Center determined equivalent R-values for the AAC - walls. Weather data for Orlando, Florida as developed in the Typical Meteorological Year (TMY 1981) database served as the basis for the outside conditions. For example, during an average summer day, the 8 inch AAC - wall performs like either a wood stud frame wall insulated with R-20.4 fiberglass batt insulation or an 8 inch CMU block wall insulated with R-8.6 rigid insulation.

Basic Principals

Thermal protection in buildings directly influences the use of energy for heating and cooling, as well as the ability to control the room climate. Less thermal protection results in more energy usage for heating and cooling and a much less comfortable room environment.

The thermal protection requirements for the external construction elements of buildings are generally categorized into one of two groups, either summer or winter.

The thermal protection for winter conditions is intended to minimize heat loss from the building, thus allowing the building to be economically heated. Furthermore, the interior surfaces of the external elements, such as walls and ceilings, should not drop below a certain minimum temperature in order to avoid condensation. The thermal protection properties must, therefore, be determined by considering both criteria.

In contrast, the thermal protection for summer conditions is intended to minimize heat gain from the warm outside temperatures and sun rays, thus allowing the building environment to be economically controlled in a comfortable state. Thermal protection in the 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. As shown below, the thermal mass and thermal conductivity establish the thermal inertia, which causes a damping and time lag of the temperature peaks.

With "AAC", a construction material is available that optimally combines the material properties necessary to provide excellent thermal energy efficiency for the building. Additional thermal protection is not required.

The AAC - building system also provides an airtight envelope, which is critical in controlling the comfortable and healthy indoor environment. A major emphasis in heating and cooling system design is to minimize "uncontrolled" ventilation air. By providing an airtight building envelope, AAC minimizes the "uncontrolled" air changes and allows the ventilation air to be "controlled". Elements such as dust and pollen can be filtered out of the ventilation air before they invade the building. By use of a dehumidifier, the moisture content of the ventilation air can also be controlled which optimizes the comfortable indoor environment. Overall, the volume and quality of ventilation air can be easily and accurately controlled in an AAC building - thus providing a comfortable, economical and healthy environment.

These excellent thermal protection properties of AAC - exterior walls were confirmed in a study by the Florida Solar Energy Center

Thermal Performance for MHE-AAC Block


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