Want energy savings? Don’t forget the cladding attachments
Most of us in the glazing industry understand that to meet model energy codes’ increasingly stringent requirements and to achieve their intended energy savings, we need buildings with high-performance fenestration and façade systems. Focusing on the glass, we sometimes overlook the importance that wall cladding and connecting elements play in attaining high thermal performance.
As we know, aluminum is a highly conductive metal. When it is used in fenestration, aluminum framing members need to be separated and insulated to avoid transferring heat from the building’s interior to the exterior. This same consideration should be given to the façade’s wall cladding, attachment clips and continuous insulation. If highly conductive elements are used, thermal bridging can occur and will compromise the building’s thermal effectiveness and energy savings.
What is thermal bridging?
Thermal bridges are localized areas where energy in the form of heat flows through walls, roofs and other insulated building envelope components. This is caused by highly conductive material components penetrating and bypassing the thermal insulation. In turn, this reduces the effectiveness of the insulation, its specified thermal performance and its potential energy savings.
What is continuous insulation?
Continuous insulation, as defined by ASHRAE 90.1, goes across all structural members without thermal bridges other than fasteners and service openings (windows, skylights, doors, and building service systems). It’s installed on the interior, outside of the primary structure (wall sheathing), or it’s integral to any opaque surface of the building.
To help ensure well-insulated buildings, the International Energy Conservation Code (IECC) has required continuous insulation in the building envelope since 2012. The 2018 IECC prescribes how much insulation is required for each of the eight U.S. climate zones and for various types of above-grade walls, below-grade walls, roofs and floors.
What materials are of greatest concern?
This is an efficient and cost-effective method to provide improved thermal performance and meet code requirements, but its effectiveness depends on thermally efficiency of cladding attachment system used.
Continuous Z-girts, made with galvanized steel or aluminum, are the most commonly used cladding attachments. These structural mounting devices secure the continuous insulation and support the exterior wall cladding materials.
Unfortunately, these conventional cladding attachments can be a significant thermal bridge and can reduce exterior insulation thermal efficiency by as much as 60 percent.
How can we avoid thermal bridging and improve energy savings?
Similar to aluminum fenestration framing members, several engineered cladding attachment systems now incorporate thermal breaks to reduce or prevent energy loss in the continuous insulation system.
If code-compliant performance and energy savings are truly a goal for your client’s project, remember that the cladding attachment strategy can have a dramatic impact on the building performance. Once installed, it can be difficult to identify an issue and costly to correct. Before the project moves from paper to the field, please speak up and ask questions. When in doubt, bring in manufacturers to help the team evaluate solutions for effective performance, efficient installation methods and competitive costs to achieve a “total value” solution.