Our response to NBC Tiered Building Code review
Lambda Science is a Canadian firm active in the small residential construction sector. Our flagship product StepWin is a community-driven web-based software developed since 2017 to help the builder community comply with the BC Energy Step Code. Builders wanted to know “how much would it cost to take our design to the next Step Code level?” and the answer to that was not clear before StepWin. After starting a successful pilot in the City of New Westminster, StepWin currently has demonstration projects with the City of Port Moody, the City of Kelowna, and the City of Penticton. With these agreements, StepWin is freely available to hundreds of builders across British Columbia.
We provide you the above background to highlight our extensive research and work relevant to the Tiered Energy Performance Compliance proposal.
The proposal, in its intent, is a crucial and welcome improvement to the Building Code. It is meant to establish a performance-based compliance path for buildings, which we believe can be foundational for ensuring durable, affordable, and comfortable designs. We support the general structure of the proposal and the use of Airtightness as one metric inside it; however, we oppose the use of the Reference House (or Reference Building) as the compliance metric for the Tiered Energy Performance Compliance.
Our reason for opposing the Reference House use is its irrelevance to the aim of the proposal which is "develop requirements meeting the goals set out in the Pan-Canadian Framework". Pan-Canadian Framework's primary goal is GreenHouse Gas Emissions (GHGs) Reductions. The relationship between the given metrics and the GHG reductions is not clear. Our understanding is that there are two avenues to reduce GHGs of buildings: Construction/Embodied GHGs and Operational GHGs. Only the latter appears to be in the scope of this proposal.
For the Operational GHGs, in the Impact Analysis section says: "Tiers 2-5 approximate the energy savings targets of ENERGY STAR, R2000, Net-Zero Energy Ready and Passive House programs." To us, it is unclear how a "Net-Zero House" is equivalent to a "House performing X% better than the reference house". In other words, suppose a homebuilder is building a house to the proposed Tier 5, should they be – without doubt – expecting a "Net-Zero Ready House"?
Our review of HOT2000 outputs for over 3,000,000 Single Family Dwelling design alternatives of our users shows no strong correlation between the Reference House comparison and the Thermal Energy Demand Intensity (TEDI) of a design . The Impact Analysis done in the proposal appears to be based on set Building Archetypes, which may not generate comprehensive results due to limited variance in building shape and properties.
Moreover, our understanding is that the Tiered Energy Performance Compliance is meant to provide the ability for each jurisdiction to plan ahead. To achieve that, the compliance measures must not frequently or drastically change. The Reference House is inherently opinionated (see an example in ). This has the potential to cause discrepancies and surprises, which may cause significant changes to the code.
We recommend the following modifications to the committee:
- For energy consumption, beyond envelope-first, attention must be given to objective metrics such as the building's actual energy consumption (TEDI, kWh/m2.yr). This can easily establish that a house is in fact Net-Zero Ready (albeit in a Standard Operating Condition and given the modeling uncertainty).
- Include a "low-carbon materials and practices" provision to address Construction/Embodied GHGs.
- Assessing the Reference House rating of the EnerGuide Rating System should be strictly a separate and voluntary metric. Not a part of this compliance.