Re-ducting the entire house

[chrisw]

As part of a larger geothermal installation (at a fixed cost) which includes zoning our house with a 4-ton, 2-stage system, our contractor is recommending we re-duct the whole thing in the basement (basement is unfinished and the current supply and return all terminates there). They took a look and are saying that at some point, someone reversed the supply and returns and now the return is way too small for effective airflow. They'd like to reverse the two and do some re-ducting which I'm fine with - I knew there would be some of that involved with getting the second zone working.

The question I have is that they're looking at also turning all of the vents on the first floor into supply vents and then adding one new large return vent in the middle of the house. This would add a new rather unsightly vent to one of our closets and cause us to lose a little bit out of the bottom of that closet for the duct work. Does this sound like a good approach?

Another question I have is that the downstairs is open but there is one bedroom and a bathroom down there. If the returns are all eliminated in favor of one large return, how will the bedroom get cooled/heated if the door is closed? They tell me that the air will flow through the cracks in the door.

I understand that it's hard to tell without actually seeing/evaluating the house but right now with our 3 ton unit, we haven't had any problems with the downstairs.

[vstech]

central returns are acceptable, if there is adequate space under the door. the main reason to do it, is to get better filtration of the ductwork system.
there MUST be at least 1 return per 1600 square feet of floorspace, and 1 per level of the conditioned space.
also, the filter size should be at a minimum of 200 square inches/ton of cooling. more is better.

what's the contractor planning to do with the holes in the floor where your original returns were?

[chrisw]

Sorry I wasn't clear on that - they want to use the existing ducts around the first floor as supply.

My main question, though, is that if the heating/cooling on the main level seems fine now, what advantage is there to adding a large central return and converting all of the existing ducts to supply?

[teddy bear]

Many states do not allow central returns any more. Ideally you should have a match supply/return in each room. This eliminates the over-pressurization of the isolated rooms and depressurization of the open central area.
Regards TB

[chrisw]

I'm in Virginia. How can I find out if my state is one of those states?

If states don't allow the central returns, what's the reasoning behind that?

[comfortdoc]

I'm in Virginia. How can I find out if my state is one of those states?

If states don't allow the central returns, what's the reasoning behind that?

Many states do not allow central returns any more. Ideally you should have a match supply/return in each room. This eliminates the over-pressurization of the isolated rooms and depressurization of the open central area.
Regards TB

As stated by TB - keep the room pressures in balance.