Q: Have scientists studied the effect of duct cleaning on air ducts that have been sealed with Aeroseal?
A: Yes.  In 1998, scientists at Lawrence Berkeley National Laboratory published a study, Residential Thermal Distribution Systems, that states:

"Mechanical duct cleaning techniques do not have an adverse impact on the ducts sealed with the Aerosol sealant."

The study goes on:

"Duct Cleaning effect on aerosol sealant (EPA). An issue that has been raised regarding the aerosol sealant is its resistance to duct cleaning. In order to examine this effect, a sheet metal duct system was sealed with the aerosol sealant and then cleaned by professional duct cleaners. The duct cleaners were local HVAC contractors who cleaned the ducts as they would for a regular service call. No attempt was made to change the tasks they performed in order to make the duct cleaning more effective. The cleaning was about four years after the initial aerosol sealing. The system was cleaned four times in total. Before the system was cleaned the measured leakage was 6.2 cfm25 supply and 9.3 cfm25 return.

The first contractor vacuumed duct system supply four times: supply system twice and return system once and both systems the same time once. For the first vacuuming, all of the registers were taped and furnace was isolated. An 8" diameter vacuum hose was connected to the supply plenum. The system was vacuumed for about 15 minutes. The pressure difference across the duct (measured at the furthest part of the duct system from where the vacuum hose was connected) was 35 Pa. The relatively low vacuum pressure was because the cardboard used to isolate the furnace was misplaced and resulted in a big leak. After this leak was fixed, the pressure difference across the duct increased to 254 Pa. The return was vacuumed separately. The two return registers were taped and the furnace was isolated. The return duct was also vacuumed for about 15 minutes. The pressure difference across the return duct was 980 Pa falling to 540 Pa at the end of the vacuum cleaning. A duct leakage measurement was performed after the above cleaning procedures, and the supply and return leakage were unchanged - within 0.1 cfm25 of the pre cleaning leakage.

For the next cleaning an 8" diameter vacuum hose was connected to the furnace burner access panel. Only a rudimentary attempt was made to seal around this connection using a rag wrapped around the hose. All of the registers were simply covered with pieces of paper rather than being completely sealed. The pressure difference across the ducts was about 220 Pa and stayed at the same level during the vacuuming process. After these two vacuumings, the duct leakage was measured to be 6.6 cfm25 for the supply and 9.0 cfm25 for the return. This result shows that the leakage was again unchanged (within the experimental uncertainty) by the vacuuming process.

A second HVAC contractor then vacuumed the duct system with a combination of inserting a spinning brush into the ducts at the registers and brushing all the way to plenum if there was no damper to block it. This was a much more severe test of the aerosol sealant because it could have been abraded by the brushes. The supply and return duct systems were isolated and each grille was removed before inserting the spinning brush and then the register was plugged with a piece of foam. The supply duct was depressurized to about 330Pa. After this brushing and vacuuming, the measured leakage was 7.9 cfm25 for the supply and 9.8 cfm25 for the return. This shows a small increase was possibly caused by a change leakage at boot to wall seal where aerosol deposition was disturbed when the grille was removed, however this amount of extra leakage (less than 2 cfm) is not significant given the measurement uncertainty (±1 cfm???).

It should be noted that the vacuuming only did not appear to remove much dust from the system. The combination of vacuuming and brushing was much more effective and included the removal of a paper cup and a half roll of duct tape!

The conclusion drawn from these tests is that duct cleaning of a system sealed using the aerosol sealant does not remove the sealant."

Click here to see the 43-page report, Residential Thermal Distribution Systems.