Improvements to model energy codes are boosting advances in the use of insulation for commercial and residential building envelopes. Continuous insulation (CI) is quickly becoming the standard for high-performance building due to its ability to greatly improve operational performance while simplifying design and installation. In the ASHRAE 90.1 standard, Energy Standard for Buildings Except Low-rise Residential Buildings, CI is defined as: "Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope."
CI is one of the most thermally efficient ways of complying with modern energy codes and mitigates energy loss that commonly results from thermal bridging. A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area with higher thermal conductivity than the surrounding materials—like the studs of a wall that have batt insulation between them, creating a path of least resistance for heat transfer. In an otherwise insulated building, thermal bridges can account for up to 30 percent of energy loss. Using CI, the insulation doesn’t skip over studs or other obstructions in the wall cavity; it covers the entire surface. This results in:
- Increased thermal performance
By blocking thermal bridging, a continuous insulation system increases the overall thermal performance of a wall assembly and a building.
- Reduced operating costs
Continuous insulation keeps energy and heat loss to a minimum, increasing the building’s energy efficiency and leading to lower monthly operating costs.
- Reduced air infiltration and exfiltration
Continuous insulation with taped or sealed joints restricts air movement through the wall, helping to further reduce building heat loss.
The benefits of certain CI solutions go beyond enhanced energy efficiency. For example, polyiso insulation can serve as an air barrier, water resistant barrier, and water vapor control/retarder in wall assemblies. These capabilities provide the following additional benefits:
- Reduced risk of water condensation and moisture intrusion
Continuous insulation is a very moisture-resistant system, guarding the thermal and structural performance of the building.
- Efficient installation
When used as sheathing, continuous insulation can simplify the steps to construct a code-compliant wall assembly.
- Dimensional Stability
Polyiso insulation has excellent dimensional stability and meets ASTM C1289 Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board.
There are a multitude of building envelope product options, and a variety of design and construction methods used for achieving compliance with code requirements for the thermal envelope. To learn more about polyiso CI systems and their tried and true methods to meet these requirements refer to PIMA Technical Bulletin #403: “Continuous Insulation Using Polyiso Wall Sheathing” and this AIA CEU course which covers:
- The different roles a product can play in the building envelope to simplify its design.
- The code requirements for buildings classified as International Building Code Type I-IV Construction.
- Strategies for achieving code compliance.
- How polyiso can play multiple roles to meet or exceed these code requirements.