A tighter home means:

• Lower heating costs
• More energy efficient
• Less drafty, more comfortable

As airtightness improves, money can be saved, but proper ventilation also becomes more necessary as:

• Moisture can potentially remain in the home longer
• Potential for stale air and pollutants to remain in the home longer

Airtightness plays a large role in determining the energy efficiency and comfort level of a house. Every hole or protrusion between the interior and exterior of the building envelope should be sealed to maintain the airtightness of the home. A small hole can increase the air leakage greatly.

All rough-ins should be completed before insulating begins. Additional rough-ins and or changes after insulating can be very detrimental to the airtightness of the house. Whenever a new rough-in is added to a home, ensure all protrusions to the exterior of the home are sealed properly, and that the air barrier remains continuous.

Great care must be taken to ensure the vapour retarder and air barrier are installed correctly and that the air barrier is sealed and continuous throughout the entire home. Keep this in mind with upgrading an existing home and be sure to reseal any holes created in the existing air barrier during an upgrade.

What is an Air Test?

An air test measures how quickly the air in the home is replaced by outside air. It is expressed as air changes per hour (ACH) and a blower door is used to perform the test.

The lower the air changes the better. It means that heated indoor air will remain in the home longer during the winter, and cooler air will remain in the home longer during the summer. However, moisture and pollutants may also remain in the home longer, so it is important to control the quality of the indoor air.

How the blower door works:

• Air from the house is pushed outside with a fan (depressurization), or outside air is pushed into the home (pressurization)
• The fan maintains the air pressure in the home at a certain pressure difference between inside and outside (50 pascals)
• The volume of air the fan has to move to maintain the pressure lets us know how much air is entering the home through leaks and cracks
• With this information we can determine how airtight the home is

Airtightness Requirements

There are many Energy Efficiency Programs that require an airtightness test to be completed:

• EnerGuide Rating System (ERS)
• EnergyStar
• R-2000
• Net Zero
• Net Zero Ready
• Passive House
• Novoclimat 2.0

Different energy programs have different standards/targets for airtightness. They are expressed in air changes per hour (ACH).

For most programs there are different standards if the home is detached or if the home is attached. It is usually higher for an attached home because there tends to be penetrations and leaks between the adjacent house/houses.

Although ERS does not have a pass or fail ACH requirement, it is recommended that the builder aims for an ACH of 2.5 or less for detached homes and 3.0 or less for attached homes. If a new detached home is insulated and sealed properly, getting an ACH of 1.5 or less is easily obtainable.

Housing Types

The type of house can have a large impact on the airtightness testing results of the home. Since there are different standards set for the different types of homes, it is important to be able to distinguish between these different types.

Housing types according to NRCan :

Improving Airtightness and Energy Efficiency

The following should be completed to improve airtightness and energy efficiency:

• Install insulation properly with no empty spaces or gaps
• Use the right insulation for the right job
  • Exterior vs interior
  • Above grade vs below grade
• Exterior rigid insulation acts as a thermal break for the wall, and improves airtightness if installed properly
• Properly attach the vapour retarder, air barrier, and weather barrier, and seal properly

Things to keep in mind:

• When insulating make sure there are no gaps in the insulation that are more than 3/4". This will cause a convection current and air to circulate in the gap. This increases heat transfer through the wall cavity
• Compressing batt insulation will reduce the effective R-value of the insulation
• Taking the proper time/care to cut/insert batts, and spray-foam properly can make a difference in the airtightness and heat transfer of a wall, header, or ceiling/attic
• When installing the air barrier make sure anything that penetrates it is properly sealed with acoustical, approved tape, or gaskets. (Will be explained further in Module 2.1)