The Importance of an Energy Efficient Design Summary (EEDS)

Published on November 30, 2018

The Importance of an Energy Efficient Design Summary (EEDS)

If a home is unable to meet the prescriptive path of energy efficiency that is required in order to meet Ontario Building Code, a builder can have an Energy Efficient Design Summary (EEDS) performed by a Registered Energy Advisor. This shows the builder what alternative approaches could be taken to improve energy efficiency, in lieu of what is missing to meet code.

Quite often the air tightness level of a building will need to be evaluated as part of an EEDS to prove that the level of efficiency has been improved. This is beneficial for home builders in more ways than one, as it also locates all points of air leakage in the home - helping builders double check their own work, as well as work done by subcontractors.

Involved in an EEDS

In the case of the performance path (when substitutions are being made) an EEDS is a computer modelled evaluation of a home, and is conducted in order to balance energy efficiency levels. This means that all aspects of the home are evaluated to show what supplemental modifications could be made to still meet code, and what the best option is for the builder to attain enough energy credits to differ from the code’s prescriptive path.

Alternatives that are provided in the EEDS are specific to each home, and may include suggestions such as: improving levels of air tightness, installing a higher efficiency HVAC system, improving insulation levels, or any combination of the above.  

Deciphering Air Tightness Values

When an Air Tightness Test is deemed necessary as part of an EEDS, the builder receives the results containing a few terms in regards to the home’s airtightness: the Equivalent Leakage Area (ELA) and Air Changes per Hour (ACH).

The ELA refers to the combined area of leakage in the entire house - visually represented as if it was once space. It is helpful to think of the ELA as a window that can never be closed unless the level of air sealing is improved. Knowing the size of this unclosable ‘window’ is extremely beneficial in determining how much air leakage is occurring, and is helpful for builders to know before they finish construction so that the process of fixing air leaks is as simple as possible.

The ACH of a home refers to how many times in an hour a building will exchange all of its inside air with exterior air, while it is at a basic and constant level of pressure (50 pascals). The ACH is one of the most important numbers used to determine if a home reaches or surpasses building code, and can be determined by a Registered Energy Advisor conducting a Blower Door Air Tightness Test.

Barrier Sciences Group Can Help!

After an EEDS has been performed, a builder may see opportunities to gain energy credits that they may not have been able to identify had they not chosen to have the summary done. For some homes a builder can change insulation levels, such as adding an R8 insulated underslab, and use this change in replace of what’s normally required in the prescriptive path of the Ontario Building Code.

Recently, I completed a Blower Door Air Tightness Test for a builder who had never had one conducted before and they were astonished to find out that the home they just built was much more airtight than they had expected. The home was modelled to have 2.25 ACH @ 50Pa, but the EEDS showed an extremely airtight value of .95 ACH @ 50Pa. This is significantly more airtight than the 3 ACH @ 50Pa that is required in the Ontario Building Code.

In some cases, having an exceptionally high level of air tightness can be detrimental to air quality without sufficient mechanical ventilation. Having an EEDS completed is helpful for the builder to know the exact efficiency levels of the home during construction, and what supporting modifications may be necessary in order to still meet building code, as well as what should be done to supplement the new changes.

Builders can rely on an EEDS to help them find things that may have been overlooked by both themselves or their subcontractors, as well as provide them with information that precisely indicates the level of energy efficiency to which they have been building.

When it comes to building quality and more energy efficient homes, accurate measuring should always be the first step.