Thermal Mass and Precast
Thermal mass is the ability of a material to absorb and store heat energy, which can be thought of like a thermal sponge. High-density materials like concrete have a high heat capacity, which means that a lot of heat energy is required to change its temperature. Materials with high heat capacity are said to have thermal mass.
All materials have some amount of heat capacity, but not all have enough thermal mass to regulate the heating and cooling loads in a building. Research has shown that thermal mass reduces annual heating and cooling requirements.
The advantage of thermal mass is recognized in the national energy codes, which allows reduced levels of insulation in mass-wall buildings because they use the same amount of energy as buildings with frame walls and more insulation. This reduction in insulation can result in significant first-cost savings. In Chicago and Minneapolis, mass walls with reduced amounts of insulation still meet the performance of the ASHRAE-specified R-value when allowing for thermal mass effects. To maximize thermal-mass effects, insulation should be placed on the outside of the concrete walls, but thermal mass still works when insulation is on the interior or inside face of the mass walls.
Another important way to use thermal mass of concrete is as a storage reservoir for solar energy collected through south-facing glass. Concrete passive solar collectors may be either floors or trombe walls, which later release the stored the heat when surrounding temperatures have dropped.
Saving energy is important
- Can reduce owner utility bills
- Energy code requirements are generally determined to be cost-effective by the U.S. Department of Energy
- Benefits to the environment from less fuel use and less pollution
National energy codes and standards
- ASHRAE 90.1-2016
- 2018 International Energy Conservation Code
- Designer's Notebook: Energy Conservation and Condensation Control (DN-15-06), 2006
- Nonresidential and mid to high rise residential
- New construction, additions, and major renovations
- Envelope requirements including air leakage and insulation
Thermal mass chart shows the benefits of thermal mass.
- Thermal Testing and Performance of Precast Wall Systems - September 2, 2020. Watch On Demand
- Designing Parking Structures and Maintenance Schedules - March 10, 2020
- Sealants 101 - March 17, 2020
- Simplify the Building Envelope with Infinite Facade - On Demand
- Designing Total Precast Office Buildings - On Demand
- Rethinking the Concrete Building Envelope (Through PCI) - August 25 and August 26, 2020
- Precast for Schools and ICC-500, Storm Shelters - December 9, 2020
Climate Map shows climate zones that is called out in energy codes requirements.