Building Science

Mass Walls and Energy Efficiency

There’s a reason man has built with mass walls for centuries

From mud huts to stone castles, buildings constructed with thick and dense walls have always been valued for their thermal properties. In parts of the southwest United States adobe buildings have been the housing of choice for as long as people have resided in that area.

Adobe buildings provide exceptional thermal benefits, keeping residents inside cool on even the hottest summer days, and warm at night in spite of winter temperatures that can drop below freezing. This thermal mass, or thermal inertia, effect is well understood in the architectural world and is also featured prominently in recent building codes. While insulating materials in the building envelope help to slow down the rate of transfer of energy through a wall system, thermal mass amplifies the energy efficiency of the system by absorbing a significant amount of heat energy that reaches the insulation. This boost in energy performance is strongest in climates and seasons where there are large swings in temperatures throughout the day.

In the 2015 International Energy Conservation Code (IECC), for example, the amount of added insulation required for a commercial building in Dallas, Texas (IECC Zone 3, Prescriptive R-value Method) constructed of light gauge framing is R-13 in the wall cavities – plus an additional R-7.5 continuous insulation on the outside of the wall. For the same building constructed of a mass wall system, the code only requires the addition of R-7.6 of continuous insulation to achieve the same level of performance.

While wood and light-gauge steel framing are still very popular, they have become more complex and costly to construct. New building codes with stricter energy-efficiency requirements are forcing builders to add more and more layers of expensive insulation, as well as pay for the additional labor and costs of adding these materials. In the end, the new building might pass code, but it will fail to provide nearly as much energy efficiency as a mass wall system. Just as important, cavity wall buildings fail to provide the level of fire and storm safety that has been demonstrated by many mass wall systems.

In contrast to light-frame cavity-wall systems, Bautex Block is a lightweight, insulated concrete block that, when used to construct a building, provides structure, envelope, fire and storm resistance, an air and moisture barrier, and continuous insulation – all in a single integrated assembly. It’s a modular, mortarless wall system where blocks are stacked and then filled with reinforced concrete to create an insulated structural wall. The wall system is constructed using the same labor, tools and techniques as those used in traditional concrete masonry construction.

The result is a simple, single, integrated wall assembly that creates an airtight, R-14 continuously insulated mass wall for the building envelope with higher energy efficiency performance than most cavity-wall or traditional mass wall systems – all without any additional insulation – while providing substantially improved levels of performance and safety.

Download Understanding R-value, Mass Walls, Continuous Insulation and Air Tightness