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Latest Step Code Changes:

Law of the instrument

i.e. over-reliance on a familiar tool. This article gives an overview of the issues with the newest BC Energy Step Code Revisions. The key improvement in the newest Revision, is offering higher fidelity on climate conditions; however, the new metric of “Reference House TEDI” was also introduced which in our opinion should not be relied upon.

When it comes to building homes, it seems everyone is in agreement that building energy efficiency must increase, the quality of construction work must improve, and we should be on our path to very efficient homes. When it comes to making this a reality, the Building Code is the target-setter. The BC Step Code defines what parameters in the design should comply with what numbers to meet the energy efficiency requirements.

This all worked out until we reached the implementation stage.

According to Clean BC: “by 2032, every new building in B.C. will have an ultra-efficient, net-zero energy ready design.” This is done by a provincial policy that “establishes deadlines for the government’s adoption of BC Energy Step Code metrics”. The BC Energy Step Code is based on metrics derived through the federal government’s building simulation tool, HOT2000.

Intention of the Step Code Practicalities of the Step Code
The complications in the implementation of the Step Code

The tool’s implementation turned out to not address the Energy Step Code intent well . Since the tool (HOT2000) belongs to the federal government, the immediate solution was to make workarounds in the BC Step Code process to steer clear of the problems. We believe these workarounds are now threatening the original vision for the following reasons.

Public consultation was missing from the process

We think if the community support is expected behind a Building Code revision, a public review period must be held for it. Unfortunately, this was not the case for these changes:

“The Building and Safety Standards Branch also considered possible amendments to the BC Energy Step Code targets for houses and small residential buildings, with a focus on climate zones 5 and 6 (including Kelowna, Kamloops, and Prince George). These possible changes were still in development at the time of the public review, and so did not form part of it.” [source]

Changes do not address the issues

As per the revision’s summary of changes, one of the issues the new revisions meant to address:

Issue #2: Alternative for Measuring Building Envelope Performance

In some buildings with unique or energy-challenging design features (such as cathedral ceilings or multiple articulations in the roofs or walls), modeling results can show significant improvements to overall energy performance, yet the same buildings may nonetheless not meet the requirements for even Step 2 using the current TEDI targets. For some buildings, even the Lower Step TEDI targets may be impractical to achieve.

In other words, designs were done where TEDI was not performing well but when reference house TEDI was showing much better results.

But instead of asking why TEDI performed poorly, perhaps we should ask why the Reference House performed so well? And what would that establish? Next item will expand on this.

With the changes, a home evaluated as Net-Zero-Ready may not perform that way after construction

As the famous statistician George Box puts it: “all models are wrong, but some are useful”. The Step Code process establishes a standard which inherently cannot be fully tested in the real world. There is no guarantee a home labeled as “Net-Zero-Ready” will perform as Net-Zero but that doesn’t mean the actual performance should be far off.

A standard, such as the one set out by the Step Code, aims to reflect reality. It is easy to get indulged in complex math for the sake of accuracy but more rules and assumptions can also backfire (see Performance Gap). The current code increases the possibility of such “attack vectors”.

As per the new code, a house that has a TEDI of 50% better than the reference house will meet Step Code level 5; meaning that when it is built and occupied it should perform as a Net-Zero Ready home. Given that the Reference House is an inherently opinionated metric (see Power Minute: Reference House), the correlation is not clear and we have not found any studies that would suggest a relation.

We studied over 3,000,000 h2k files of designs in 5 BC climate zones and did not find a strong correlation between the energy demand of a house and it's improvement compared to the reference house.

TEDI and % Better Correlation
TEDI and TEDI Ref % and their lack of correlation

Software code is considered to be as the law

The current HOT2000 simulation tool has been a valuable asset for the community; however, any software tool has limitations. Lambda Science had discovered that HOT2000 11.6 was creating reference houses with notable differences from the NBC specifications, causing up to 3 GJ of discrepancy in the reported results. The source code HOT2000 is not accessible to us and it is only supported on Windows. The building code should go towards being software agnostic to allow flexibility in the market for alternative solutions. The new changes go in the opposite direction and further depend on HOT2000 outputs.


Consequently, we believe that addressing the existing Step Code issues requires a broader look towards how the CleanBC goals will be met:

It is our assumption that the new Step Code changes are proposed to align with the proposed National Tiered Building Energy Code. Lambda Science is also preparing comments for that proposal, recommending against the reliance on the reference house.