HiV Confusion

[thegau]

We have a 1922 two-story Dutch Colonial in the upper Midwest, and are planning to add central A/C. Before getting bids, I did some research on this forum to learn about the differences between Hi-Velocity and Conventional. I think I have a decent understanding of how the systems work, and their pros/cons.

Given the age of our house and lack of any central ductwork, I had assumed I would need to go with a Hi-Velocity solution. However, as we were getting bids, one installer said that we could actually go either way -- conventional or Hi-Velocity. Our house has interior closets, which is apparently not so common in houses of our style, and which makes it a little easier to run the necessary ductwork for a conventional system. Does this sound right?

The installer who mentioned this seemed to be technology-agnostic. He is giving us quotes for both a conventional and a Hi-Velocity system, and said that either way would work for us.

Now, here is where my confusion starts. All three Hi-Velocity installers indicated that we would need to have multiple Hi-Velocity ducts in each of our closets -- like, 3 or 4 in each. The agnostic installer said the same, but said that if we went conventional, we would only need to have one six-inch duct in each closet (without insulation).

So here is my first question: If Hi-Velocity is supposed to be space-saving, how are 3-4 insulated ducts per closet less space than a single 6-inch (uninsulated) duct?

My understanding was that one of the benefits of Hi-Velocity was that the ducts could flex and be run in between the floor/ceiling joists to get to places that would be impossible to reach from a conventional system. Yet all three Hi-Velocity installers indicated that they just planned on drilling straight down from the closets and opening the vents there. So I guess my second question is: If we're going to go straight down, couldn't a conventional system do the same?

Third question: If we went conventional, would we also need a return duct for each room? Or is there a single central return duct, like there would be in a Hi-Velocity system?

Finally: If our house can deal with a conventional system, and if the conventional system is both more efficient (higher SEER rating) and much less expensive, *and* if it seems like Hi-Velocity would actually eat up more closet space, and if we don't need to take advantage of the flexible ducts of Hi-Velocity, what reasons would we have to choose the Hi-Velocity option? (I realize that Hi-Velocity has better circulation, fewer dead spots, and lower humidity, all of which could be important to some degree -- but are there other reasons I'm not thinking of?)

Thanks in advance!
Chris

p.s. -- A mini-split system is not an option for us, because of cosmetics. We are trying to preserve the feel of the house (it has been impeccably maintained over the years) and are trying to minimize the visual impact of our retrofit. A conventional (or Hi-Vel) duct in the ceiling is probably fine, but not a large mini-split blower.

[slimwoodie]

Oooooohhhhh ...

for a minnit ...
i was thinkin'

HIV .....:rolleyes:

[rubberduck]

What does HIV stand for?

[timebuilder]

Maybe it's a duct infection.

[BaldLoonie]

HiV is high velocity. Like a Space Pak or Unico.

Remember that you won't need many outlets on the first floor. Cold air falls. My cousin lives in her old family home. 2 story, conventional ducting. Auntie wouldn't allow supplies on the first floor where they could be seen so there is one in a corner of the living room and one in the back hall ceiling. It's not an open floor plan but still the first floor stays nice & comfy from cold air coming down from above and heat rising.

But yes, there could be cases where 2 or 3 outlets are needed in a room. But then one 6" conventional probably would be insufficient as well. An 8" may be more appropriate for a larger room.

Any time you can have return in each room, you are more comfy and can shut the door without hurting cooling. HiV usually has 1 large return. Conventional can be that way or better to be ducted to each bedroom.

We've done a few 2 story homes with conventional and done just fine. So definitely can be done. Easier? Cheaper? Can't say without seeing.

HiV is expensive and a SEER and capacity killer. Just in equipment, for the price of a HiV air handler which often turns a 13 SEER outdoor unit into maybe 11 SEER - you can get a top line variable speed air handler and get 14 SEER plus good dehumidfication. Next question is: does the high cost of the HiV ducting balance out with easier install or not.