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Has anyone had any experience with exposed ducts in houses?
We’re building a house in a two-story steel barn, steel trusses and AC ducts we will leave exposed.
THE DUCTS: we’re contemplating 1) leaving them as is, bare; 2) applying a clear acrylic coat; or 3) painting them white or light gray.
AC man suggested we clean them with a 50-50 vinegar/water wash prior to painting, but not too sure he’s had a lot of experience with installations like ours.
Should the ducts be painted prior to installation, or in situ?
We like the silver color, but what happens if we leave them bare ,,, we’re in the country 80 miles NW of Houston, fairly humid at times?
Thanks.
Gup
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Well, you are installing them insides the conditioned envelope, to the primary worry is air-sealing the ductwork. Most ot the good mastic out there is a pasty white color naturally--so you could go with a white color. The mastic is generally paintable, so whatever color you prefer will likely work.
As a guess, the vinegar suggestion was a way to take the natural oil/grease off of the metal, so it would better take paint--but a decent painter ought to be doing proper pre-paint prep in any case.
Left bare, they should work. That's bare, but with the joints sealed. As long as the air inside your insulation envelope is not too humid, the ducts will not condense the humidity any more than the metal structure or any other item in the structure.
80 miles, huh? Anderson? Shiro? Navasota, maybe? Only about 10 miles from me, so it piques my curiosity.
Captain, not so fast...consider what Ray Moore is saying here.....
106517.22
consider what Ray Moore is saying here.
And he makes a good point. I'm guessing that OP's structure is to have a certain contemporary/industrial style to it. Which generally means that some ducting is concealed--and those ducts are the ones most 'at risk" in higher humidity situations for dripping or other problems.
I'm very familiar with the environmental conditions the OP is likely to face, being 90 miles NW of Houston (within 15-25 miles of the OP, probably).
This is not going to be (or should not be) a case where windows will be thrown open to overwhlem the dehumidification the a/c provides 8-9 months of the year. Using what I guess will be a PEMB will likely affect the windows used, as well as their operation, too.Occupational hazard of my occupation not being around (sorry Bubba)
As long as the air inside your insulation envelope is not too humid, the ducts will not condense the humidity any more than the metal structure or any other item in the structure.
During cooling season the ducts will likely be the coldest item in the structure.
During cooling season the ducts will likely be the coldest item in the structure.
But, during cooling season, they will be in the most dehumidified state, too. Also, good design here will put the ductwork up high, in the warmest air.
The risk for condensation is really going to be highest on the inside, just as the system starts blowing cold, dry air into the warm air within the ductwork. However, given that this is all inside the conditioned envelope, the air in the ductwork probably will not be warmer than mid to upper 80's, and (we presume) at RH's under 40-50%--this makes a strong contrast to most of my part of Texas, where ductwork is run through attic spaces that are heated to 130-145 at RH in the 60-75% range (that R6 wrap can seem ironic).
And, there is another method OP could use, too. Simply sleeve the sealed, insulated, ducts in another, larger duct. That outside tube needs only slip jointery and no mastic. It can retain it's natural finish. And, you really only need to "sleeve" in the "where it shows" spaces.
Occupational hazard of my occupation not being around (sorry Bubba)
Your duct material will be galvanized won't it so the humid thing should not be a problem. As for prep of the metal you will have to degrease it in some manner & then prime with compatable primer.
Not being a pro painter I think I would degrease & prime the metal, do the install and then spray paint after the install. That being said I haven't seen the job site conditions & the feasibility of my plan.
I once did a job where we cleaned off fire sprinkler pipes & misc utility on a concrete ceiling, We wiped down everything with mineral spirts, masked off what ever we had to & sprayed with several lighter coats of latex. I was able to spay all the coats in one day.
Best of luck in your project
No one should regard themselve as "God's gift to man." But rather a mere man whos gifts are from God.
Gup,
How do you plan to insulate your steel structure?
Galvanized duct usually comes with an oily film on it that must be cleaned before they can be effectively painted. Detergent and water will work well, but the surface should be scuffed to help the paint adhere.
If you do not paint it, the shiney bright galvanized finish will oxidize and turn a dull, flat gray.
I would paint as much as possible before installation.
Painted, spiral duct is left exposed, uninsulated in commercial installations all the time. Look up in amost any bar/grill and/or casual restaurant.
Ya beat me to it.
Left them exposed in my shop. No paint,... dust doesn't show up so well on the dull, flat gray color. The metal is getting close to the color of the gray of the mastic.
Assuming you are going with round spiral pipe...
Single wall, uninsulated spiral will condensate if it installed close to the ceiling, where it is the hottest.
You can buy spiral pipe with gaskets built-in, eliminating the need for duct sealant. Single wall pipe is easily field cut. The added cost of the gasketing washes when compared to the labor of applying sealant and the aesthetics if the duct is close to eye level.
Double wall insulated (and gasketed) spiral is also available. This material eliminates the condensation issue and noise... and, naturally, it costs more. It is not imposssible to field cut this material, but it is time consuming.
Depending on the manufacturer, you can specify a Paint Grip coating, or order material that is ready to paint (no oily film).
Diffusers that mount right to the spiral are available... or a 2" hole saw works good. I prefer the spiral with round air holes look myself.
Do not waste time painting prior to installation. It is impossible to prevent scratching the paint without adding a ton of install time.
The metal must be cleaned of dirt and oil and prepped with a primer prior to paint. Mask and spray.
Shiny galvanized will turn grey with time.
Thanks to all of you for your helpful input.
AC DUCTS, SPIRAL or PLAIN? As far as I know, our ducts are the plain, ordinary kind. Fear at this point that we should have gotten SPIRAL ducts but when questioning the AC company in the beginning, were told they were considerably more expensive.
Are SPIRAL ducts self-insulated? Are most ducts insulated one way or another? We have NO ATTIC, and our ducts will be visible to all, all the time.
So, more questions:
1) SEALING JOINTS: does the sealing (mastic?) of the joints occur inside the ducts, thus out-of-sight, or on the outside? Is there a way to get the sealing take place so it doesn't show?
2) WRAPPING DUCTS: hadn't planned on wrapping ducts with anything, so, uh, are we going to regret this? Is there a wrap that looks GOOD, since these ducts will be hanging around our ceilings (10' plus), just overhead, for all to see.
Appreciate very much, all the helpful suggestions.
GUP
AC DUCTS, SPIRAL or PLAIN? As far as I know, our ducts are the plain, ordinary kind. Fear at this point that we should have gotten SPIRAL ducts but when questioning the AC company in the beginning, were told they were considerably more expensive.
Hmm, the joints on rectilinear ductwork are going to be very :industrial." The hangers are likely to be similarly under-aesthetic.
Are SPIRAL ducts self-insulated? Are most ducts insulated one way or another? We have NO ATTIC, and our ducts will be visible to all, all the time.
Nope. Ductwork, unless made from insulated ductboard are not insulated. Insualtion is added to ductwork when specified (you did specify insulation when you bid the hvac work?)
Is this really "100% exposed," as in even the air handlers are going to be visible, too? Having the returns (and the filters) right on the handlers is less good in our climate (they really ought to be low down to collect cooler air). Having the filters at "ladder reach" can also be a pain. The plubling connections for airhandlers are also not very aesthetic, either, not without major preperation. There's two drain lines off the a/c section, for one. There's the stat wiring as well as the power for the blowers to sort out.
If you were in Bryan, you'd have to provide at least a 24 x 48" service walkway, as well as the service outlet within 6' of the unit (you'd have to wet vent the A coil, and daylight the A coil's pan drain, too--your AHJ may vary).
1) SEALING JOINTS: does the sealing (mastic?) of the joints occur inside the ducts, thus out-of-sight, or on the outside? Is there a way to get the sealing take place so it doesn't show?
Typically, sealing is on the outside, and it does show. That's because generally nobody's arms reach long enough down the ductwork to reach the joints from the inside.
2) WRAPPING DUCTS: hadn't planned on wrapping ducts with anything, so, uh, are we going to regret this? Is there a wrap that looks GOOD, since these ducts will be hanging around our ceilings (10' plus), just overhead, for all to see.
We are back to "depends." From your description, this is an industrial look, going for a loft-like interior housed in a Pre-Engineered metal building (PEMB) frame and skin. Are you planning large banks of operable windows? Numerous patio or french doors? (Those sorts of things add considerable complexity to the interior purlin and channel work on the building frame, and usually cost more, so that may not be the case for you.)
So, if you are running the a/c, the internal humidity ought to stay in the controlable range (so the ductwork probably would not drip any more than a ceiling register might (that's "ought," "should" and other similar conditionals.) Let's say the air up around the ducts is 84-85, when the stat calls the a/c on. The a/c will then start pumping 60-64 degree air through the ducts. As long as the dew point is less than that, then there's no condensation risk.
From my experience, none of the available insulating wraps have ever passed a client's definition of "looks good." Since you have bent ducts, that's probably even more the case.
Now, if you really need a bunch of work, you can do like one of my clients did, and specify "oh, we'll just slip sonotube of the ducts and paint it." Never did find out how that worked out--could not have been easy.
Now, there is one more middling critical design question here--has the mechanical design taken the exposed nature of this into the design for register placement? A lot of hvac types run a trunk line close to where the needs are, and then run shorter ducts, and then connect registers with flex. Well, there's going to be precious little up there in the open spaces to plant a register upon. Which means you need rigid ducts all the way to the registers. This may not be a feature that your contractor has planned on--so it may be extra. Now, bedroom and bathroom spaces, since they will have ceilings, will not have that problem. But, those connections may be very visible from upper areas, so you have to go through those, too.Occupational hazard of my occupation not being around (sorry Bubba)
WRAPPING DUCTS: hadn't planned on wrapping ducts with anything, so, uh, are we going to regret this?
Gup, As long as you are not concerned about a little bit of dripping water..then you may have no regrets...you can always just "move your chair"
Many of Frank Lloyd Wright's buildings leaked - the story is told of Hibbert Johnson (Johnson Wax) who, sitting eating his Thanksgiving dinner in a Wright designed house, discovered that a drip from the roof was landing on his head.
He picked up the phone and called Wright and asked what he should 'do' about it.
Frank answered, "Move your chair, Hib, move your chair."
So you are saying his exposed duct work is going to remain below the dew point of the air in a conditioned space? His a/c unit won't rmove enough latent heat from the air to prevent condensation?