Trying to get some specific basics so that I can ask the right questions.

[hurple]

Hi,

I'm in the process of converting a brake shop into our home (don't worry, all the environmentals came up clean) (http://

1923mills.blogspot.com for pictures). I'm about to hire an HVAC contractor to install some ducts for A/C (it's a slab on grade with cathedral ceilings, so heat will be provided using radiant tubes). It's a loft style building so there is a huge open area (about 1200 sqft with a cathedral ceiling 22ft up to the center) and a few smaller rooms with 9 ft ceilings (under the loft). For the big area what I would like to see is commercial style exposed spiral ducting which would work nicely aesthetically for the space. The other rooms would have traditional resi ductwork. I have a few questions.

1) I don't know anything about flex duct other than it sounds like it's often used inappropriately. If the contractor wants to use flex duct for the smaller rooms what should I watch for?

2) The size of the large area is obviously relatively huge compared to the small rooms. Does that matter? It seems like there would need to be some sort of balancing. Is that true? What should I hear from the contractor on that front?

3) Anything else I should know so that I can be a reasonably informed customer? I seem to be bumping into some specialisation issues as far as commercial people not wanting to do resi and resi people not comfortable with spiral.

Thank you all so much.

[jamesgangnc]

Nothing wrong with flex if it is sized and installed properly.

A single system should be able to be installed and adjusted to work properly but I agree you should worry about the balance. One way to avoid that entirely would be to use two smaller independent systems.

[Bubba]

A smaller system, unless it only has one supply run, STILL needs to be balanced. Bubba

[HVAC fella]

Put in adjustable balancing dampers in each supply duct, then you can regulate how much air you want to go where. Dont close them any more than 50% otherwise not enough air will move over the Cooling Coil of the a/c system and youll have problems with the equipment in time. Have the supply and return ducts lined with DuctLiner which is half inch insulation -- it will make for a much quieter system plus prevent condensation on the outside of the supply ducts.