Sealing the HVAC Ductwork

We are still attempting to pass the very strict Energy Star tests required by LEED (and EPA) concerning air leakage in our HVAC ductwork. Today, Aeroseal is here to seal the ducts from within using a heated vapor plastic product.


The process starts by blocking all of the supply and return vents in the house so they can pressurize the HVAC venting system.

More Blocks

Return Vent Block

Here's a shot of the block installed on the largest return vent.


Then they cut a circular hole into our beautifully finished main supply duct in the basement so they can hook up their system. They also block both the HVAC unit itsef and the ERV, so the dried sealant doesn't ruin them !!!


Here's a view of the inside of their vent showing some dried plastic sealant from other jobs.

The Other End

Then they start setting up the other end of their unit exactly ten feet from the cutout vent.

The Completed Contraption

Here's a shot of them attaching the phaser from the Star Trek series in the 60s ... just kidding. It's actually the nossle that sprays the heated plastic into the ducts under pressure.

The Completed Contraption

This is what their system looks like when it's finally all put together.

Another View

Here's another view of "the contraption" ready to go. Notice all of the extension cords running into the unit. It requires a LOT of electricity to do its job. So much that they had to run FIVE extension cords upstairs to get the required power. And then, they had trouble with it blowing the GFI protection circuit breakers.

A View from the Back

Here's a view of the unit from the back. The nossle has to line up perfectly with the duct exactly ten feet away for it to work. If it's off a bit, the spray attaches to the sides of the long "balloon".

Sit and Wait

Once the unit is up and running, the entire process is monitored by a computer. Essentially, you sit there and monitor the pressure, temperature, and leakage values. That's John Love, my HVAC guy, on the left. He's already bored ;-)

More Waiting

And you monitor ... and monitor ... and monitor. It's REALLY boring ;-)


This shot shows all the details of what the computer is monitoring.

Return Ducts

We got the cubic feet per minute (cfm) leakage down from 110 to 43 on the supply side. That's pretty good. Then, you disconnect the contraption from the HVAC supply line, repair and seal the big round hole, and start the process all over again from the return side.


And then you monitor ... and monitor ... and monitor ;-)

We managed to get the return ductwork down from 190 cfm leakage to 70 cfm. Again, pretty good.

But we ran out of time. They were here at 8:30 AM and didn't leave until after 6:00 PM. They'll be back on Thursday to finish up.