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