Residential ducts can represent a great opportunity for improving energy use, and air quality performance in the home. Excessive air leakage, lack of insulation and improper balancing are the cause of poor performance in Australian homes.
- One of the key ways of improving the effectiveness of your ducted heating system is by keeping the system as balanced as possible. Closing off rooms that aren’t in use, by closing doors that have supply outlets, restricts air flow from that outlet getting back to the air handler which then allows the air handler to draw air from somewhere else (outside)
- If doors are kept closed in a home, install a Door Grill vent available from our Efficiency Matrix webshop. Do not block off outlets in unused rooms. Most ducted heating systems are designed to warm a whole home not part of it.
- Ensure your return Air supply is as air tight as possible. Watch our video at the bottom of this page.
Here are the Problems that can occur in duct systems.
1. Building envelope boles on the Return air side, as shown in the video at the bottom of this page, can create the following problems:
- Causes a net loss of air into the house from outside. A state of depressurization occurs in the main area connected tothe return outlet which increases the potential for back draughting internal hot water heaters and furnaces should they exist inside the building envelope. Dust-laden air also will make its way in, making it difficult to keep the building clean.
- Return air leaks in a wall cavity connected to under the house and/or the roof area will draw dirty air into the duct system which decreases the performance of the air handler and adds nutrients to mold, mildew, and bacteria in the duct system.
2. Supply ductwork leakage can make rooms uncomfortable.
3. Conductive losses will occur where ducts run in the roof area or under a house. The loss can be quite significant depending on the temperature differential. ducts are basically a part of the building envelope.
How we check the air tightness and efficiency of duct systems.
- We can measure the air flow from an outlet, with the use of a flow hood. It can indicate if there is a balancing issue or a leaky supply duct.
- We prepare all the outlets of a ducted heating system, and then we retrofit a fan to the return air outlet, where we depressurize the ducts to measure a leakage rate.
Duct Cleaning or Duct Testing?
Duct Cleaning in America has been researched to provide no measurable difference in air quality. Once dirt sticks to the inside of ducts it stays there for good. Below are some of the statements made…
From Canada Mortgage and House
“in the 1990’s duct cleaning research conducted by Canada Mortgage and Housing Corporation and the US Environmental Protection Agency tested house and duct performance before and after cleaning. Researchers observed little or no discernible differences in the concentrations of house airborne particles or in duct air flows due to duct cleaning.”
From Indoor Air 2002 (1C6o5 on page 25)
“duct cleaning had no measurable effect on supply air quality.”
From the EPA:
“The results of the particle mass measurements suggest that… the airborne concentrations before and after cleaning were not substantially different…”
Before you choose to clean out your ductwork, consider testing them for air tightness so that less dust/moisture can get inside them in the first place.
Here is a common flaw in residential Ducted heating systems in Melbourne Australia