John and Susie booked an energy audit but are having some trouble understanding the test results.
What does a Blower Door Test do?
A blower door is a machine used to measure the airtightness of houses. It can also be used to measure airflow between building zones, to test ductwork airtightness and to help physically locate air leakage sites in the houses envelope.
Blower door tests are commonly done on new construction to ensure building standards are met and they are also commonly done as part of an energy assessment, ie. in Ontario we have the energuide rating. Homeowners will often book an assessment before starting a renovation so they can take advantage of any government incentives for improvements made to their home. The auditor will perform the blower door test and do a complete walkthrough to locate problem spots around the house. Often with a renovation their is the possibility for your home becoming to tight after insulation is increased or a new air barrier is installed, this can lead to condensation on your windows and the potential for mould growth. This is why it’s equally important to get the test done after the renovation as it is before.
Blower door tests are commonly done on new construction to ensure building standards are met and they are also commonly done as part of an energy assessment, ie. in Ontario we have the energuide rating. Homeowners will often book an assessment before starting a renovation so they can take advantage of any government incentives for improvements made to their home. The auditor will perform the blower door test and do a complete walkthrough to locate problem spots around the house. Often with a renovation their is the possibility for your home becoming to tight after insulation is increased or a new air barrier is installed, this can lead to condensation on your windows and the potential for mould growth. This is why it’s equally important to get the test done after the renovation as it is before.
Understanding the results:
How is air tightness measured?
Air Changes per Hour (ACH) at a specified building pressure, typically at 50 Pa (ACH50).
This metric indicates the rate at which the air in a building is replaced with outside air, and as a result, is an important metric in determinations of indoor air quality. This normalizes the airflow at a specified building pressure by the building’s volume, which allows for more direct comparison of homes of different sizes and layouts.
The Effective Leakage Area (ELA) assumes that all of the individual leakage areas in the building are combined into a single idealized orifice or hole. This value is typically described to building owners as the area of a window that is open 24/7, 365 in their building. The ELA will change depending on the reference pressure used to calculate it. 4 Pa is typically used in the US, whereas a reference pressure of 10 Pa is used in Canada.
To give you some perspective on how air tightness has improved here is a look at the air standards of various building standards;
An unrenovated pre - 1960’s 4 square brick home, could have an ACH of 10-20.
Pre 1990’s would more likely be around 5 - 10 ACH.
Today’s current building code does not require a maximum ACH for performance, the only situation is if a trade off is required (ie. if due to circumstances you weren’t able to achieve a certain insulation level you could compensate with a lower ACH.) in which case 3.0 ACH for a detached house and 3.5 ACH for attached.)
source: Homesol Building Solutions
Air Changes per Hour (ACH) at a specified building pressure, typically at 50 Pa (ACH50).
This metric indicates the rate at which the air in a building is replaced with outside air, and as a result, is an important metric in determinations of indoor air quality. This normalizes the airflow at a specified building pressure by the building’s volume, which allows for more direct comparison of homes of different sizes and layouts.
The Effective Leakage Area (ELA) assumes that all of the individual leakage areas in the building are combined into a single idealized orifice or hole. This value is typically described to building owners as the area of a window that is open 24/7, 365 in their building. The ELA will change depending on the reference pressure used to calculate it. 4 Pa is typically used in the US, whereas a reference pressure of 10 Pa is used in Canada.
To give you some perspective on how air tightness has improved here is a look at the air standards of various building standards;
An unrenovated pre - 1960’s 4 square brick home, could have an ACH of 10-20.
Pre 1990’s would more likely be around 5 - 10 ACH.
Today’s current building code does not require a maximum ACH for performance, the only situation is if a trade off is required (ie. if due to circumstances you weren’t able to achieve a certain insulation level you could compensate with a lower ACH.) in which case 3.0 ACH for a detached house and 3.5 ACH for attached.)
source: Homesol Building Solutions