I am in the process of air sealing my mid-1980's 2-level stick-built house (2500 sq ft simple rectangular plan; has a conventional unheated attic outside conditioned space, everything resting on a concrete slab).  Assuming all the measures work out ok, I'll hopefully get to the point where I'll need mechanical ventilation of the HRV style.  However, my house is heated by hydronic baseboards, so I have no existing ductwork.
One of the suggestions from toolbase is high-speed mini-ducts.  The alternative is conventional ductwork.

I've seen one old thread (http://hvac-talk.com/vbb/showthread.php?p=1853369) suggesting issues with mini ducts, but in context that was about A/C capacity which is a bit of a non-issue for me, as I have no plans to add A/C -- this is all purely for ventilation.  Most everything else I've read has been quite positive about mini ducts, especially for a retrofit situation.

So my question for the community is what sort of experience have you had with mini duct systems for ventilation?  I have no plans on trying to DIY this, and have started digging through local installer lists to do interviews, but I am interested in a second opinion from the group.

Bill

check out the Zender units. (zenderamerica.com) Its a German HRV which uses a system of 3" flexible ductwork, so it should be a cinch to retrofit. Unlike the mini duct systems, their ducts have a smooth interior which allows for substantially better airflow.

Thanks, but they don't seem to sell into Canada.  The product looks cool, though.

I am also looking into Unico, High-Velocity, and SpacePak.  The comparison, of course, is retrofitting with regular big ducts.  I was hoping for some real-world experience with:
1) fishing the smaller mini ducts through a finished house vs. fishing bigger ducts (eg, sliding up in between studs), and
2) performance and reliability, especially given that with a mini duct system I have an extra box or two to accelerate the air. (presumably with bigger ducts I can just use the HRV directly?)

Bill

agree with this recommendation

Can't tell you about retro fit but I have install a Unico System in my new house. As I have hydronic floor heat I have added the coil to the unit and bring in fresh air that way. I have size a primary exhaust fan to give the required air exchange. This works better for me as there is no freeze up or recir. time that you would have with an HRV unit.