Net zero has long been used to describe the highest performing buildings – an objective in the building industry’s quest to reduce its environmental footprint and combat climate change. In 2016, B.C. released the Climate Leadership Plan, with the goal to make buildings net zero ready by 2032.
But what does net zero ready mean? And is it an achievable goal for all buildings?
Net zero is typically defined as a building that produces as much energy as it consumes on an annual basis. But this definition can vary by project – is renewable energy production on-site or off-site? How does it consider efficiency versus renewables? Does net zero hinge on the building’s size, location, and access to solar? Does it consider greenhouse gas emissions or just energy?
Toward Net Zero the “Right Way”
In theory, any building can be net zero energy with enough photovoltaic (PV) panels. However, the best practice approach to net zero takes three steps:
- Reduce the demand for energy through passive design measures like a highly insulated building enclosure and heat recovery ventilation.
- Efficient use of energy through low-energy mechanical systems, equipment and lighting.
- Generate the balance of energy through renewable supply like PV, geothermal, etc.
The B.C. Step Code tackles the first two: reducing demand and using energy efficiently. Whether this achieves net zero ready will vary by building, but it’s a step in the right direction.
The Step Code Approach
The Step Code introduces new energy performance targets through two primary metrics: Thermal Energy Demand Intensity (TEDI) and Energy Use Intensity (EUI).
TEDI is a metric of the building’s modelled heating needs, which is primarily influenced by building enclosure insulation and airtightness, as well as the ventilation system. A more highly insulated, airtight enclosure with heat recovery ventilation will achieve a better TEDI value.
Airtightness testing is required, with Part 9 limits ranging from 3.0 ACH50 for Step 2, to 1.0 ACH50 for Step 5. In Part 3 buildings, the tested airtightness rate is used in the energy model to meet the TEDI and EUI targets.
The Step Code TEDI and airtightness testing requirements ensure the building loads are reduced to a reasonable performance level.
EUI is a metric of the building’s total modelled annual energy consumption including heating, cooling, ventilation, plus lighting and plug load energy for Part 3 buildings. The metric is slightly different for Part 9 buildings, which looks at only Mechanical Energy Use Intensity (MEUI) and omits lighting and household appliance/plug loads.
The Step Code EUI/MEUI requirements ensure the building equipment and systems use energy efficiently.
For those who have worked with the Passive House certification program, the Step Code approach may sound familiar. Passive House uses a similar approach with requirements for heating demand (similar to TEDI), primary energy (similar to EUI) and airtightness, although there are still some key differences between the metrics in the two programs. The highest Step Code steps achieve close to Passive House performance and allow teams to use the Passive House software tool to demonstrate Step Code compliance.
Implications for New Buildings in B.C.
The introduction of the Step Code means a few changes for new buildings in B.C.
Although the Step Code is now a part of the BCBC as of December 15, 2017, the Building Act will change to require that local governments reference the Step Code when setting requirements for better-than-code energy performance. While the Step Code will be optional to jurisdictions, local governments can choose to require or incentivize it as part of their sustainability strategy. This will remove ever-changing requirements that varied from jurisdiction to jurisdiction while mapping out a path forward. Teams that want to get ahead can aim for higher Step Code levels and learn from the experience with a consistent set of metrics.
The Step Code will improve delivered performance by requiring airtightness testing for all buildings that comply with the Step Code. Airtightness is a highly cost effective energy conservation measure and while there may be an initial learning curve for some teams, experience south of the border has shown that airtightness testing is highly effective and achievable.
The Step Code will expand the role of energy modeling as all buildings meeting the Step Code will require a model. The Code references the City of Vancouver’s Energy Modelling Guidelines, which must be followed to determine the TEDI and EUI for Part 3 buildings. Other guidelines for professionals are in the works, including energy modelling professional practice guidelines as well as additional guidelines and training material.
The Step Code only applies to certain building types: Part 9 residential, Part 3 multifamily residential, and Part 3 commercial. The Step Code applies to Part 9 buildings province wide, but Part 3 buildings only in Climate Zone 4, covering the Lower Mainland, Southern Vancouver Island, and Southern Okanagan.
In summary, the B.C. Energy Step Code will bring consistency and predictability to the building industry, while advancing the energy performance of new buildings towards the province’s ambitious goal of net zero ready by 2032.
Brittany Coughlin is an associate, energy and sustainability specialist RDH Group. For more information, go to: http://www2.gov.bc.ca/gov/content/industry/construction-industry/building-codes-standards/energy-efficiency/energy-step-code