Hi folks,

Our current home (and new home under construction) has an Energy Recovery Ventilator that we run pretty much year-round. The house uses rigid-foam cladding, and it's very very tight, so we rely on the ERV for regular air changes.

The unit is installed in the basement and the HVAC installers use insulated 6" flex duct (see link) for the intake and exhaust runs that are about 25 ft.

http://www.homedepot.ca/product/flexible-insulated-ducting-6-inch-x-25-foot/959965

In our current home we've had to get the intake duct replaced three times because of either slits and tears in the vapour barrier, or else poor sealing on one side or the other, allowing humid inside air to get into the insulation and condensate on the inner duct that is passing really cold winter air to the unit. Each time water has accumulated in the lowest point of the duct run.

After the first two times this happened, I stopped having the HVAC guys do the warranty repair and I terminated the ends of the ducting myself to make sure it was done properly. The installer was lazy and used screws to hold the duct to the exterior cap, and then just wrapped tons of "duck tape" around it, taping it on. I followed the proper installation procedures of sealing the duct and vapour barrier separately to the collar, etc. Problem is that when the installer shoved the duct up into the floor joist, it came in contact with a bunch of screws poking down through the subfloor from above. I tried to catch all the tears and seal them with tuck tape, but I must have missed some and after this winter, once again I'm getting a bit of water accumulating in the insulation.

I'd like to not deal with this in the new home and replace the flex duct with insulated rigid ducting myself. Does this exist? If so could someone recommend what I'd need? Could I maybe get away with a smaller diameter since rigid wouldn't restrict airflow as much as the flex does?

Thanks in advance!