by J.R. Babineau
High-performing commercial buildings are becoming popular because of evolving codes and stricter standards for occupant safety, comfort, as well as energy efficiency. In addition to providing benefits like improved indoor air quality (IAQ), buildings designed and constructed with efficiency and performance in mind set the stage for financial and environmental sustainability because a stronger building envelope is created. One can achieve high-performing building envelopes by combining continuous and interior cavity insulation solutions.
At the outset, construction teams must evaluate the threat of thermal bridging—caused by materials with higher thermal conductivity—to wall systems and identify opportunities to create a more high-performing building envelope. This can be accomplished by using a variety of insulation materials.
An ideal wall structure comprises two cooperative components—continuous insulation (ci) on the exterior of the wall and interior cavity insulation on the interior. Including interior insulation with the exterior insulation helps reduce sound transmission and airflow through walls, which provides a more comfortable space that can decrease the total project scope. The combination of interior cavity insulation and exterior continuous insulation (ci) is often also the most cost-effective approach. Applying only exterior insulation, for example, can make for a complex and expensive project when factoring in other components such as windows, doors, and cladding attachment systems.
Continuous insulation, as defined by the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, is insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It can be installed on the interior or exterior and should be an integral component to any opaque surface of the building envelope. Installing the insulation on the interior is typical for projects without framing which includes masonry, concrete, and pre-engineered metal buildings.
Interior cavity insulation (i.e. insulation installed in the interior space between structural members) is another element to consider for maximizing the building’s energy efficiency.
This two-pronged approach minimizes thermal bridging and maximizes performance by leveraging the unique benefits of both cavity insulation and continuous insulation. While there is no one-size-fits-all approach, a variety of material options are available.
The building envelope of a high-performance structure effectively manages heat flow, air leakage, and rain/moisture intrusion. When creating a high-performing system, it is advisable to first consider all relevant building code requirements for insulating commercial buildings. Both the International Energy Conservation Code (IECC) and ASHRAE 90.1 require minimum R-values, sealing against air leakage, and ci in building envelopes. These R-value minimums vary based on geographic location, facility occupancy, and the building material (masonry, wood, steel, or metal framing). Both documents also prescribe how much insulation is required for above- and below-grade walls, roofs, and floors in each of the eight U.S. climate zones. It is important to always refer to the correct code version for a given jurisdiction. In newer editions of the codes, climate zones have shifted in some parts of the country, and some insulation requirements have changed as well.
Secondly, consider the climate zone and its impact on the required R-value. As the zone number increases, the climate gets colder, and most of the required insulation R-values also increases. R-value stands for resistance to heat flow—the higher the R-value, the greater the insulating power and resistance to heat flow. The climate zone determines whether the solution will need to protect more against hot, cold, or mixed climates. For example, climate zone 6 (e.g. Minneapolis) tends to be cold, and therefore, a higher R-value is required for both cavity and ci to help resist loss of heat in the winter.
Lastly, bear in mind the types of walls and their functions. A successful wall system manages heat, air, and moisture leakage, and different building materials can react to these elements at varying degrees. Metals are good conductors of heat, and may cause thermal bridging, but they are also less susceptible to burning in the event of a fire or rotting due to moisture issues. Conversely, wood is more susceptible to moisture damage, but has significantly lower heat conductivity than steel or concrete. The overall design of all wall systems, from cladding and structure to where the various control layers will be (thermal, air, and water), should be thought through and decided in the planning stage of a project.
Careful consideration of these components early in the planning process will impact whether or not the insulation solution meets the goals for energy efficiency and overall building performance.