Thank you for the info. All my walls including external ones are 2 X
So I cannot run 6" or 8" ducts inside them. I don't know if using rectangular or oval ducts is better than using 4" round ones. My 50 yo house has all 4" round ducts from plenums.
I also didn't know ducts are insulated from inside. Do all ducts need to be insulated even those running inside heated space? again. all my walls are 4" (actually 3 1/2 ") thich. This does not leave much space for insulated ducts.
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gfretwell
You only need to insulate ducts that run outside environmentally controlled space.
Round and oval duct is more efficient per square inch of cross section than squares and rectangles because of the surface area. You see rectangles because that allows more square inches in a wall cavity. They swap size for efficiency. Flex can virtually match the efficiency of metal if it is installed straight and tight.
If you are running forced air from below a ground floor to a 2nd story typically a large run is made somewhere inside like the back corner of a closet to a distribution hub in the attic. Then branched out from that with flex to ceiling registers. Personally on a 2 story house I prefer two smaller independent systems. Also handy when one fails at an inopportune time, you still have heat/cool in part of the house.
As I said I want to new heating cooling system independent of existing one for new addition. The addition is master suite on second floor over the family room and office and the workshop on ground floor with new slab on grade foundation adjacent to existing house garage. I also want this new system to be two zone heating/cooling bedroom and workshop independently.
I don't know yet where new furnace and A/C will be, may be in the basement though I don't have space there. Possibly in garage, I don't know if it is good idea since garage is not heated. I will discuss this with HVAC guy who will be doing HVAC drawings and with the architect. If it is in garage I will have to run ducts from basement to second floor. The same probably for returns. Where is the best to position registers height wise? Is it better to position them close to floor (all my registers are 14" from floor level) or higher close to ceiling?
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gfretwell
You are touching on the biggest problem with heating and A/C using the same ducts. The objective is exactly opposite depending on which you are using at the time. Cold air drops and hot air rises
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ls02
I understand this. Ideally you would have lower registers for heating and upper registers for cooling. I will talk to HVAC pro but I still want to see what generally accepted solution to locating register is. From space perspective I want them all to be high close to ceiling. Right now several of my existing registers are blocked by furniture.
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jamesgangnc
Commonly these days they are located where it makes it easiest to connect them. Ceiling for attic systems and floor for garage/basement systems.
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Stormin Mormon
Yes, flex has more resistance. Yes, you can insulate metal ducts. I've done it.
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Jules
Yes, that's the problem I have in our place - no upstairs ducted heat (just electric baseboard), and it'd be hard to get anything up there due to the layout and wall thickness. All the upstairs rooms have two windows, too, so I'd really need two registers per room.
I'm thinking water-filled rads would be a *lot* easier - I should be able to run plastic pipe without disturbing the floors too much Only downside is that I need quite a few pipe runs at right-angles to the floor joists, and I don't like drilling holes in critical structures :-)
cheers
Jules
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Jules
I'm always surprised that even works - it means really long runs, going through cold attic space, only to have warm air come out at ceiling level, right where it's least useful for heating the room.
cheers
Jules
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Existential Angst
One possibility is to do the plumbing runs on the wall surfaces, and hide them behind a kind of cove or crown molding -- basically just a 45 deg slat of wood at the baseboard, or ceiling, or where two walls meet vertically. Aesthetically, cosmetically, these 45 deg ditties could actually be a plus, if done right.
And, it would make the runs easier to do.
That still leaves the A/C, tho -- unless someone figgers out how to do a hot water/chilled water system economically. If I went through the trouble to run hot water (which doesn't seem like all that much trouble, compared to ducting,esp. considering the results), I'd proly go the whole way, and avoid A/C ducting, via mini-splits.
Another idea, if going the ducting route, is to install both high AND low registers, that are switchable, for heat, A/C. TOH or hgtv showed this pneumatic ditty, where full zoning is achieved via pneumatic air bags in each register -- which can also be retrofitted, btw. I posted a link to the company that did this a while ago, don't have it offhand. Very inneresting, tho, to see them snake bitty plastic pneumatic lines thru the ductwork, registers..
Imo, however, ducting is inherently "sloppy", energy-wise, unless one goes through phenomenal effort to make sure everything is air-tight, insulated, etc.
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Jules
interesting idea... in fact I've seen a lot of houses back in the UK where they just run the pipes on the walls and don't cover them at all. Looks a bit messy, though.
Last place I had in England had 10mm microbore for the radiator pipework (which is what, 3/8"-ish) and that worked just fine - but I've not investigated in the US yet to see if I can get fittings to do something like that here. That'd mean trim for the rooms would only stand about 1/2" from the wall, which could easily work (subject to something interesting having to happen at the corners)
Yeah, thankfully that's not a problem I've got up here in MN; even in mid-summer heat, just opening the windows and/or using a fan gets enough airflow, so I don't need to worry about fitting AC.
That's a really neat idea. I was (idly, not seriously considering doing it) wondering a while ago how I could motorise registers, but that approach is far more sensible...
Yeah, seems that way to me. I'm not sure why the US still uses so much of it, except maybe just industry inertia. Maybe it'll change and we'll see more and more hot water systems around in the next few years...
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Grumpy
Yes I bet it is messy but only that poor efficiency and is OK if don't get to cold in the area where they use that system, but? I guess it is lot cheaper. Now if that is embedded into floor that would be different story.
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Existential Angst
Heh, exposed plumbing is a bit of a retro-rage in some high-end bathrooms, NYC/Greewich Village/SoHo type stuff.. Chromed, of course.
So 1/2 copper (do they make a 3/8 copper?? I think they do -- I've got oddball smallish fitting) would do just fine, then.
And think Wire-Mold for office-type surface wiring -- in that office beige/brown. Not really my style, but perhaps something analogous could be done with the whole baseboard system, a very slight tasteful "boxing out". Or, a bottom cove.
Well, check out
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about 2/3 down, "parallel blade zone damper" and
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. Grainger's has motorized dampers, but larger area, larger price.
I'm looking into one of the above for a drafty kitchen vent.
Proly cuz it half-assedly kills two birds with one stone -- heat and A/C. I'm hoping someone figgers out a nifty residential hot water/chilled water system, altho that would proly be only for new construction. The condensate handling would be a bear for retrofitting. But mebbe someone can figger that out as well.
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