What are the requirements for duct leakage testing?
In new construction both the 2012 IECC (International Energy Conservation Code) require duct tightness to be verified. Verification can take place via either a post-construction test or a rough-in test.
For the post-construction test, leakage measurement must be made across the entire system, including the manufacturer’s air handler enclosure, with all register boots taped or sealed at a test pressure of 0.1 inches w.g. (25 Pa). The 2012 IECC only contains a requirement for total leakage of less than or equal to 4 cfm per 100 ft2 of conditioned floor area.
For the rough-in test, leakage measurement is made across the system, with the manufacturer’s air handler enclosure if it is installed. The test is conducted at 0.1 inches w.g. (25 Pa) with all registers taped or sealed. The 2012 IECC limits the leakage to 4 cfm per 100 ft2 of conditioned floor area when the air handler is installed and 3 cfm when it is not installed.
What does this mean to builders? Let’s consider the example noted here. This is a new construction home approximately 2,000 sq. ft. of living space. Given the code requirements, the leak test would fail at any value greater than 80 cfm. In this home, all of the ducts have already been sealed the “conventional way” using aluminum tape. Note the “Pretest Results” below:
Even with the joints sealed, the ducts leaked 348.5 cfm of air. That is equivalent to 65.8 square inches of openings throughout the duct system. Simply put, the opening is equivalent to a 6 inch by 11 inch hole in the duct work! After the Aeroseal process the measured results were an incredible 7.8 cfm or a hole 1.2 inches square. This is an incredible 97.7% reduction in leakage. But more importantly to the contractor – the labor and material to seal these ducts was already expended prior to applying Aeroseal. Material may be low … maybe $75 in tape … but the labor to seal this duct system was probably equal to about one days labor for his install team. I don’t think we need to get into the economics of using Aeroseal for the contractor any more than this … but here are some additional data points for the homeowner to consider:
Average Energy costs in Southern New England for a 2000 sq ft home with a forced hot air system run between $2,800 and $3,900 (oil) and $1,100 – $1,500 (Natural Gas) in very well insulated homes (like new construction requires). This average is across the spectrum of homes that have between 30% – 40% loss in their system because of leaks. Let’s be conservative and say we can eliminate 90% of that loss … using an average loss of 35% … the average costs would look like this:
Oil – between $1,918 and $2,772 (savings of between $882 and $1,228 per year)
Gas – between $753 and $1,027 (savings of between $346 and $472 per year)
Keep in mind these numbers are based on very well insulated homes … so an existing system in a home built prior to 2012 will see savings up to 20% greater. Obviously these numbers are based on broad averages. Actual savings will be based on size, insulation, climate considerations, construction … even the angle your home is built in relation to the sun … but consider the goal of the IECC which is to limit the carbon footprint of buildings (among many other conservation based initiatives). Aeroseal will be good for the environment in terms of limiting the carbon footprint by reducing this waste, will provide greater comfort in your home, will improve Indoor Air Quality and is an economic no-brainer for contractors. What’s the catch? There is none! Just look at the cost of this process!