Prescriptive vs Performance

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Prescriptive vs Performance, which Path should I choose?

Since 2014 the Alberta Building Code has Included Section 9.36 which specifically relates to Energy Efficiency of Houses and Small Buildings. The application of this is meant to reduce the Carbon Footprint related to Residential Housing.

There are essentially 3 main ways of complying with Section 9.36 of the Building Code:

  • Prescriptive Path
  • Performance Path
  • ENERGY STAR / LEED etc

If you are considering the ENERGY STAR / LEED path you likely already know enough that you don’t need to read on. Feel free to discuss this option with us, but we will not go into further explanation here. So that leaves us with Prescriptive Path vs Performance Path.

 

What’s the Difference?

PRESCRIPTIVE PATH compliance basically means that you need to meet the minimum requirements as Prescribed in the building code for every element of the building envelope and heating / cooling system.
Summary: Prescribed Minimum Efficiency Targets for each Individual Element

PERFORMANCE PATH compliance does not require every element to meet prescribed Building Code minimums, as long as the finished house Performs as well or better than the Building Code requires. This is calculated using software modelling to compare the proposed house specifications to a similar one (note: not identical, *see below) that uses Building Code minimums.
Summary: Overall Efficiency Performance of the house is calculated

The end result is that the regulation requires us to show that the house is built to either (1) a minimum standard, or (2) that if the minimum standard is not met on all elements it will not adversely affect the efficiency of the house (*see below).

 

Which is Better?

Does that mean that both Prescriptive Path and Performance Path will always produce the same result?

The simple answer is no. There are 2 reasons for this:

  1. Performance Path often relies on using Higher Efficiency Heating Systems in order to offset lower insulation values.
  2. Performance Path allows for certain concessions(*) that Prescriptive Path does not.

* By taking advantage of these concessions, Performance Path compliance can often reduce efficiency below Prescriptive Path requirements while remaining compliant. Performance Path also allows the removal of an HRV (Heat Recovery Ventilator) from the system without a corresponding increase to the envelope rating.

As a result, each path has it’s own pro’s and cons:

Prescriptive:

Pro’s:

  • Building a solid envelope is key. Prescriptive compliance requires each element of the envelope (many of which are difficult to upgrade later) meet code minimums.
  • If you want to upgrade your efficiency at a later date, this is relatively simple to do by upgrading mechanical equipment to higher efficiency models.
  • Prescriptive compliance does not have to be recalculated each time you build the house (should you build it more than once).

Con’s:

  • In order to meet minimum targets, it is often advisable to include a HRV (Heat Recovery Ventilator). This means adding a piece of mechanical equipment to the heating system that otherwise may not be required.
  • It is often the more expensive way of meeting the Code Requirements.

Performance:

Pro’s:

  • Ability to ascertain the real world value of increasing efficiency in various areas of the structure. (eg would there be greater benefit to increasing the efficiency of the furnace versus adding more insulation?)
  • Often the more economical way of meeting the Code Requirements.

Con’s:

  • It can be difficult to upgrade efficiency at a later date, as initial performance compliance often relies on upgrading mechanical equipment to higher efficiency in order to meet compliance.
  • Performance compliance must be recalculated each time you build the house (should you build it more than once).
  • Is not necessarily as energy efficient as a Prescriptive Path compliance (*see more above)

 

Which should I choose?

We recommend the following considerations:

You should choose Prescriptive Path if:

  • You prioritize a higher quality building envelope (insulation) over reducing construction costs on the envelope.
  • You are happy to further increase your insulation value or use a HRV (Heat Recovery Ventilator) as part of your heating system.
  • You are on a tight time frame for planning.

You should choose Performance Path if:

  • You are only looking to meet code minimums and want to reduce your construction cost.
  • You want to build a higher quality home, but want to choose where to put the extra investment into energy efficiency
  • You don’t want to use a HRV (Heat Recovery Ventilator) as part of your heating system, and you don’t want to increase your insulation value to compensate.

Conclusion

While many drafting offices may promote one compliance path over another, we feel that as the owner and/or builder that it should be up to you to make an informed decision. We are happy to provide Code compliance via Prescriptive Path or Performance Path. If you are still unsure which path to choose, come talk to us!

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About the Author:

Andrew has a Diploma in Applied Science (Architectural Technology). He refined his skill as a designer working for several award winning architects, and established Global Design Studio in 1999.
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