Jurisdictions around the world are rapidly increasing the stringency of their energy requirements for new and existing buildings. At the same time, more and more building owners and developers seek to go beyond code minimums to demonstrate a commitment to sustainability, deliver greater comfort to occupants, and enjoy operational savings. Facades play a huge role in determining a building’s energy performance, but they also drive aesthetics and as a result, marketability. All of this begs the question: What happens when energy efficiency requirements start dictating dramatically different facades?
Façade Design Will Change
SageGlass recently commissioned RDH Building Science to look at different façade options for meeting more ambitious energy efficiency requirements.1 Specifically, RDH examined three key questions:
- How do smart windows help meet the requirements of Passive House Certification, British Columbia Energy Step Code (Step 3) and the Toronto Green Standard (Tier 3)?
- To put the Canadian targets in a more familiar context for US audiences, the Toronto and BC targets are roughly 50% more energy efficient than ASHRAE 90.1-2016 levels,2 the benchmark level referenced by LEED 4.1.
- How do smart windows help address cooling loads, and potential HVAC downsizing, in these climates?
- What other ECMs (Energy Conservation Measures) would need to be used to meet the requirements if traditional Low-E windows were used instead of smart windows in the buildings analyzed?
Top 5 Findings
The results of the RDH analysis revealed five significant findings relating to future façade choices and energy efficient design:
- Big change is coming soon. Meeting future requirements cannot be done with “business as usual” design approaches and features.
- The changes can have aesthetic impacts. In the past, meeting energy targets did not always have a significant impact on building design, specifically exterior aesthetics. This will not necessarily be the case for future requirements. This means early stage design ought to consider energy targets to create concept renderings that accurately depict future buildings.
- Smart windows prevent trade-offs. Incorporating smart windows can help projects meet energy requirements without incorporating other costly features or reducing the amount of glazing. This report calls out two specific design features that would frequently need to be used if smart windows were not included:
- Exterior shading. Future office and multifamily buildings will often need to include these features for all glazed areas. This includes both fixed and operable solutions. Regardless of the exact solution employed, exterior shading has significant impacts on a building’s aesthetics as well as upfront costs.
- Greatly reduced window-to-wall ratio (WWR). If exterior shading is not employed, frequently the only viable alternative is reducing WWR, sometimes cutting the amount of glazing in half. As the amount of glazing is tied to daylight and views of the outdoors — features that support wellness and provide significant occupant value — this trade-off may be unacceptable from a marketability standpoint.
- Smart windows reduce peak cooling loads. Across building types, standards, and climate zones, smart windows were shown to significantly reduce peak cooling demand. This can allow for HVAC system downsizing and associated cost savings (subject to discussion with project mechanical engineers).
- Smart windows can provide comfort without mechanical cooling. Vancouver requires buildings that don’t include mechanical cooling to demonstrate that they will meet thermal comfort criteria. The data show that smart windows help meet both thermal comfort and energy requirements.
If you want more info, our white paper provides detail on these findings, as well as the data itself.
- The full report by RDH can be found here. Data and findings are based on specific building archetypes analyzed in certain locations. Changes to archetypes or locations would impact the data. The report contains all relevant details and assumptions.
- This is specific for large offices, the primary archetype analyzed. The comparison here is on a site EUI basis for this archetype.