What Is Air Leakage and What Role It Plays in Energy Efficient Homes?
To comply with the Passive House Standard, a home must have an extraordinarily airtight building envelope, among other things. One of the Passive House Standard’s primary objectives is to reduce heating energy needs by 90% compared with existing homes. One of the main ways to reduce the heating and cooling load, and one of the Passive House Standard’s specific performance requirements, its airtightness.
What Is Air Tightness?
Airtightness refers to the ability of a building to prevent air infiltration through unsealed joints in the structure and around the windows. A leaky home ventilates poorly, letting too much cold air in during the winter and not enough during the summer. While ventilation is an important factor for indoor air quality, the best approach is to build an airtight home with a whole-house ventilation system that can carefully control how the air is ventilated and conditioned.
How Do You Measure Air Tightness?
The ability of a window to retain heat by reducing air leakage through gaps in or around the window is described by its air infiltration and is typically measured in cfm/ft². The lower the air infiltration, the less air is leaking in or out. A basic replacement window has the infiltration value of air around 0.3 cfm/ft2. A high-performance window can have an air infiltration value of as low as 0.01 cfm/ft2, allowing approximately 95% less air to pass through and around the window.
While air infiltration refers to the window’s performance, Air Changes per Hour (ACH) reflects the airtightness of a structure as a whole. ACH measures the amount of air that leaks out of the house (from walls, windows, ceilings, etc.) and are expressed in terms of the number of times per hour the volume of air in the house is exchanged through leakage – in other words, how much your house breathes.
How Do You Test Air Tightness?
In practice, airtightness can be measured using a blower-door test. A blower door is essentially a powerful, calibrated fan that mounts into the frame of an exterior door with a device to measure the pressure inside and outside the door. The fan blows air in or sucks the air out of the house and creates a pressure difference between the inside and outside air.
This pressure difference forces air through all leaky areas in the building envelope until the inside and outside pressures equalize. The tighter the building envelope, the longer it takes for the pressures to equalize.
Air Tightness in the Passive House Standard
The Passive House Standard requires an ACH score of 0.6 or lower on a blower-door test, i.e. a home cannot leak more than 60% of its air volume in an hour. This represents a drastic reduction compared to average airtightness in mainstream construction.
Increase Air Quality and Home Energy Efficiency by Performing Leakage Testing
A simple air leakage test is the first step you need to do to improve your indoor air quality and energy efficiency. All that is required is a fan to be set up near a door. Once you have placed the fan near the door, you will see that air that flows throughout the fan is equivalent to the air that is coming through a leak in the outer shell of your home.
If you utilize white smoke when you do the air leakage testing, you will see leaks in doors or windows that are enabling your air conditioning and heating to go away or toxins to enter. Dust, mold spores, pollen, and insects enter the home using these cracks.
Most individuals are aware of the reality that older homes are usually drafty because of numerous leaks, but the fact is, newly built homes can likewise have air leaks. It is accounted that new homes may have around 300 square inches of air leaks in the outer shell. In case you have a ducted air circulation system in your new home, these leaks can create a lot of pressure within the home that will drive air by these leaks.
Conclusion
One final caveat. If you are thinking about sealing your home to enhance the air quality and energy efficiency, you must consider minimizing the measure of chemicals that you utilize. More and more researches are demonstrating that the air quality in our homes is also worse than the air we inhale outside.
Carpeting that gives off cleaning products, toxic fumes, personal care items, and electronic gears are just a few of the items that we utilize indoors that leads to sick house syndrome. So, it is advised that before you resolve the job of enhancing your air quality and energy efficiency of your home, use natural products more often in your home to keep you healthy and your family safe.
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