9.13FS008Understanding ASHRAE 90.1

Fact Sheet FS008

Understanding ASHRAE 90.1

9.13

FS008Understanding ASHRAE 90.1

Cover

9.13

FS008

Understanding ASHRAE 90.1

ASHRAE 90.1

ASHRAE 90.1 sets a code design standard providing minimum requirements for the energy-efficient design of buildings, mechanical equipment, and criteria needed to determine compliance with these requirements. The guidelines span seven regions and provide thermal mass and insulation standards in various climate zones for achieving R-Values. Precast walls and thermal panel design easily meet these ASHRAE 90.1 code standards and can provide considerable energy savings over the life or a precast building.

Thermal mass building envelopes in certain climates can be utilized as a simple way of reducing building heating and cooling zones. The use of sandwich wall panels can result in additional energy savings in most climate zones when compared to standard wooden housing construction. The reductions in heat loss, combined with the thermal mass wall and insulation materials, help reduce building cooling and heating energy demands. Mass walls with insulation may lower peak energy demands and average heating and cooling levels operating in buildings, providing overall long-term energy cost savings.

Thermal mass walls also cause time lags for the energy demands, greatly reducing the heating and cooling requirements of a facility, and providing use of off-peak energy at lower energy rates. This also creates a smaller investment for the owner when purchasing HVAC equipment for the building project. Effect on system is flattening of peak design temperature load, shifting heating and cooling loads to off-peak hours. Mass is then allowing for a natural energy load shift that insulation cannot provide.

Overall, the thermal mass works effectively in building applications by delaying peak heat load. The chart below shows the lag effect of thermal mass, and gauges the shift in peak load that occurs later in the day, showing how the shift in the peak load helps alleviate energy demand.

Page 1 of 4

9.13

FS008

Understanding ASHRAE 90.1

Insulated precast sandwich wall panels can easily achieve code requirements for insulation in all zone climates. There is a significant benefit existing when insulation is combined with large amounts of thermal mass. Basic function of thermal mass is that as radiation strikes a wall, it warms the wall surface. A portion of this heat flows into the wall’s insulation materials where it is temporarily stored in the thermal mass and then released back into living space as the building cools. The thermal mass then begins moderating interior temperatures. Thermal mass is capable of reducing total energy loads in many climates and locations.

The seven climate zones shown in the image below feature specific code recommendations based on humidity, temperature, climate, and location per ASHRAE 90.1.

In order to predict the performance advantage of insulation over traditional build types, the effectiveness of the panel system is based on the location of the thermal mass and the wall materials used, and the degree to which an improvement in R-Value exists in a structure depends on climatic location. It is important to recognize that insulated walls utilizing Thermomass® generally result in the highest effective R-Values in the industry.

Traditional wood builds don’t have the insulation factors that provide the heat retention and release that occurs in thermal mass precast concrete walls. Studies demonstrate that heating and cooling demands in mass wall envelopes of high R-Value can be lower than those in similar building constructed using wood or other light-weight technologies. ASHRAE 90.1 endorses continuous insulation and

Page 2 of 4

9.13

FS008

Understanding ASHRAE 90.1

thermal mass in wall panels and recommends a lower R-Value for high performing insulated walls than for other non-precast systems. The lower R-Value recommendations in the thermal mass buildings allow the design of the precast panels to easily meet the ASHRAE 90.1 code and possibly exceed the code by 30% or more.

If wall materials conduct heat poorly, conducted heat gains will be discharged rapidly. Ineffective systems result in minimal thermal mass effect due to discharged heating gains. Since effectiveness of thermal mass is increased if materials with low thermal conductivity are used, composite connectors and thermal mass can maximize results in retention of heat gains. The concrete panels effectively utilize thermal mass of the concrete creating the R-Values.

Since thermal mass is a property that enables precast concrete wall panels to absorb, store, and release significant amounts of heat, precast concrete building construction and design have a unique advantage when compared to other building types. The energy-saving advantage occurs because of the inherent thermal mass of the concrete and the insulation attributes. The combination of these materials allows the building to slowly absorb energy and hold it for a much longer amount of time than a wooden structure. This delays and reduces heat transfer in the thermal mass panels, leading to fewer spikes in heating and cooling requirements since the temperature fluctuations are moderated, reduced heat transfer and reduction in energy use, and a shift in energy demands to off-peak times.

Page 3 of 4