BC Energy Step Code and Acoustics

BC Energy Step Code and Acoustics

Our buildings are going to look a lot different in the not-so-distant future. British Columbia is on the cusp of a transition to constructing much more energy efficient buildings. Starting in 2032, the BC Building Code will require new buildings to meet a net-zero energy ready standard. The BC Energy Step Code provides the path to get there. Little by little, buildings will need to be more airtight, use less energy to heat, and have more efficient mechanical systems in an effort to reduce the energy demand from one of the most significant energy consuming sectors.

To find out more about how the BC Energy Step Code works, and if it has been implemented by a specific local municipality, check out energystepcode.ca.

What role will acoustics play in the shift to net-zero energy ready buildings? This post reviews some of the ways the BC Energy Step Code will impact building design and examines the acoustical factors affected by the following metrics:

  • Airtightness;
  • Thermal Energy Demand Intensity; and
  • Mechanical Energy Use Intensity (for simple buildings covered under Part 9 of the building code) or Total Energy Use Intensity (for more complex Part 3 buildings).

Those who are familiar with Passive House design will recognize similar principles in the Step Code and find the following discussion pertinent.

Airtightness

Step Code: Making a building envelope more airtight helps keep thermal energy from leaving the with the air. Airtightness is measured in air changes per hour.

Acoustics: Sealing cracks and holes improve the high-frequency sound attenuation of the building facade. However, existing building practices tend to provide a sufficient level of high-frequency sound attenuation to meet most interior sound criteria. Therefore, we don’t expect significant acoustical benefits to result from a more airtight exterior facade.

Thermal Energy Demand Intensity (TEDI)

Step Code: TEDI is a measure of annual heating demand per unit area per year (kWh/[m2 year]) and is determined through energy modelling. Thicker walls, better windows, , more airtight exterior facades, minimized thermal bridging, and lower form factors – a contrast to highly articulated building facades that look fancy but lack energy efficiency. By “decorating the facade” instead “decorating with the facade,” building designers can achieve low TEDI targets while also setting the stage for a better acoustical environment.

Acoustics: An envelope-first approach has the potential to benefit the sound attenuation properties of exterior building facades. We expect to see the largest acoustical changes as a result of more stringent TEDI targets in the following areas:

Windows: Historically, windows have been the building facade component with the weakest sound attenuation properties (measured using the Outdoor-Indoor Transmission Class [OITC] metric). With a shift to windows that are thicker to offer better thermal performance, as well as a relatively lower window-to-wall ratio, you can expect a Step 5 building to be quieter indoors, with less exterior noise ingress than buildings constructed to Step 1 standards. Note that triple pane windows don’t necessarily offer better sound isolation compared to double pane—the performance depends on the OITC rating.

Form Factor: A lower form factor means that fewer external walls will be exposed to sound.

Figure 1: Plan View of Building A with Three Exposed Facades, and Building B with One Exposed Facade

In the figure above, Building A will have a higher indoor sound level compared to Building B because it has less exposed area to sound. Therefore, a building design that decorates the facade as opposed to decorating with the facade benefits both the TEDI and interior sound levels.

Thermally improved walls: When designing exterior facades, be aware that adding lightweight insulation does not always mean that a wall will attenuate sound better. Facades with exclusively external insulation pose the risk of creating a mass-air-mass resonant chamber, reducing the sound isolation of the wall assembly compared to a split-insulation wall.

Mechanical Energy Use Intensity (MEUI) or Total Energy Use Intensity (TEUI)

Step Code: The Mechanical Energy Use Intensity (MEUI) or Total Energy Use Intensity (TEUI) considers the annual energy consumption per unit area per year (kWh/(m2 year) including heating and cooling, and ventilation. For buildings under Part 3 of the code, the TEUI applies, and includes lighting and plug loads.

Acoustics: Historically, air delivery heating and cooling have been the norm in Canada. With advances in technology, mechanical systems that use water or refrigerant to condition buildings have become smaller and more feasible (particularly in Part 3 buildings). In general, smaller, more efficient mechanical systems generate less noise. However, the overall sound level of these mechanical units can still pose a problem if acoustics are not considered. With annual cooling demands forecast to increase significantly as a result of climate change, an emphasis is being placed on passive methods to cool buildings, such as natural ventilation. If the building site is located in a noisy environment, however, relying on natural ventilation (such as open windows) can make it difficult to achieve low interior sound levels.

Conclusion

To wrap it up, expect net-zero energy ready buildings to be quieter inside due to an improved exterior facade assembly and quieter mechanical systems and equipment. Bad news for acoustical consultants? Not really. While lower interior noise levels are generally desirable, noise levels that are too low can create other problems. Without the masking from exterior noise sources like traffic or interior mechanical services, people are more likely to hear everything their neighbours are up to!

Achieving lower background noise levels requires improved interior sound isolation design to maintain the same level of acoustical privacy. In addition, other building trends like modular building design, lightweight construction, and building materials with lower embodied carbon will keep us busy in an industry that is adapting to the Canada’s climate and energy needs.

If you have a project that requires excellent acoustics and a net-zero energy ready design, please contact our office. Our consultants bring insight, flexibility, and experience to every project. We’re familiar with the latest energy efficiency standards, and we work hard to deliver effective solutions to acoustical problems in almost any sector.

Here’s to a more energy efficient future!

To read more about the BC Building Code and acoustics, check out the following articles:

 

Written by Forest Borch

 

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