Hey gang, I'll try to make it brief.
I'm building a new 2 1/2 story house. I would like to put the HVAC
equipment in closets on the 1st and 2nd floors, but our designer is
pushing us to just stick 'em in the attic.
My rationale is that the attic installations tend to take up a lot of
floorspace that I'd rather use for storage or something useful on the
3rd floor. Also, there might be some gain in efficiency with shorter
duct runs and having the equipment operating inside the conditioned
So, what do you all think? Would you rather install/maintain equipment
in a dedicated closet, or a hot attic? How big a closet would you like
to see for this? I'd like to make it as easy as possible to work on.
Any other words of wisdom? :-)
Thanks for sharing your opinions.
Tell the designers that they can put them in the closets or they can look
for another job. If they persist with their ignorance, drag them up into a
hot attic and make them knee crawl, through all the fiberglass insulation,
to the other side of the house where the air handler got put, then ask them
if they are going to do a complete service on the unit?? and are they going
to be willing to crawl up in the attic when its 100 degrees outside, on the
4th of July to replace a transformer, because the homeowner cut and shorted
out the condenser control wire with a weed wacker.
think accessability for service, maintenance, and repairs.
Put the air handlers in closets, make them big enough so that you have a
*MINIMUM* of 6 inches clearance on both sides, 1 inch on the back and 8-12
inches on the front behind the door if its all electric, and 12 - 16 inches
on the front if its a gas furnace. Do check your local codes and the
manufacturers instructions for the exact *MINIMUM* requirements. Ita always
a real good idea to leave a little extra room, and make the access door
frame a couple of inches wider than the unit to allow for replacement down
Thank you for your comments. They are quite helpful, and I agree 100%.
I haven't spec'd equipment yet, so don't know the exact sizes, but was
looking at doing a 4x5 foot closet, which should provide at least as
much clearance as above.
There are three issues brought up by our designer for why he prefers
1. Lost floorspace in the living area - I can live with that.
2. Noise - I think I can live with that.
3. Zone dampers. Where to put them.? In a closet installation, all the
ductwork will be concealed in soffits and ceilings, so where do you
put the zone dampers where they will be accessible. I don't quite know
how to address this one.
In addition, since all the ductwork will be inaccessible, I'm pushing
for all metal ductwork instead of flex. I think this may also be
causing our designer some heartburn, as he has to be a bit more
careful to leave space to route it.
OK... that works... however 4x5ft is a bit of overkill
He's getting paid by the sqft.....it cuts into his bottom line
If the system is correctly designed and sized, it should be almost virtualy
Each system will be its own zone... unless you have less than about 800
sqft, or more than about 2500 sqft or so per floor, zone dampers shouldn't
be an issue.
Get the correctly designed and sized tin ductwork....when done right, it
will last the life of the house and is a 1 time expense, where flex *WILL*
have to be replaced repeatedly over the life of the house.
That's good to know. I won't push to make them any bigger than that,
which should make our designer happy.
Our floors will be, I think, in the 2000-2500 sqft range. So, you're
saying that, at that size, there's not much benefit in zoning within a
given floor? I can see that, I suppose. I was thinking that some
zoning might be nice for convenience/comfort, though. So, for example,
the kitchen could get extra air when it's hot in there, without
freezing the rest of the floor. (A problem we have now.) Is that worth
doing, and if so, back to the original question...where to put the
I'm going to push for that. Finding a company willing to do it that
way may be a challenge around here (Houston), these days, sad to say.
Dampers usually go on the main trunk lines. FWIW, with a correctly installed
system with properly sized and designed equipment and ductwork, there should
be no more than a degree or so temp diference between any 2
rooms....including the kitchen. Keep in mind that the kitchen needs to have
proper supply and exhaust ventilation, as well as utility room(s). Think
about having an ERV or 2 installed.
They are out there, its just a matter of finding one... and no, they will
not be the lowest bidder.
So, if I understand you correctly, you're saying that zoning is
probably more trouble than it's worth, in this case. Well, I can live
with that, I suppose. About the only thing we'd really give up is
individual control of some (or all) bedrooms, which would be nice, but
not absolutely required.
No argument there. I expect that it's not going to be cheap to do it
the way I want to. But, hopefully, if I do it the right way, I'll only
cry once, as the saying goes.
Yeah, but when was the last time you cried over the cost of something? Do
Now, when was the last time you bitched over something that was designed
wrong? Today, yesterday... I bet it wasn't long ago. :-)
have you did any research whatsoever on zoning? One very important
facet to remember is for the most part, residential hvac systems are
constant volume Oh sure, they may have a variable speed blower, but
they're moving a fixed cfm thru the coils. Now along comes a zoning
damper that closes and what happens to the air that was going thru the
coil and down that duct? Where does the extra air go? Well, some
systems would then have a bypass damper, such that the air you just
paid to be cooled is now dumped right back into the return air. Now
you pay to cool it again. Pretty soon the supply air temp sensor says
Hey, I'm too cold & therefore it will cycle the compressor off so the
coil doesnt freeze.
Cheaper zoning systems have dampers that are either open or closed,
far better systems have dampers that modulate from 0%-100%. Another
critical factor is upsizing the branch ducts to accomodate the extra
airflows imposed when zone dampers modulate closed. Then there's the
bypass system. Cheap, barometic control or modulating motorized
control. Does your zoning system have communicating thermostats &
is it web-enabled?
Regarding the tin ductwork: I'm in Ca and easily 95% of ALL homes in
Ca have flex duct installed in them, even brand new homes. I'll
venture a guess that you will not find a resi hvac contractor in
Houston that installs metal ducts in attics or in new resi, unless its
a custom home. Sealing sheet metal when its crammed into tight soffit
areas etc just isnt going to happen. I'd rather have a tight flex
duct system than a leaky tin system anyday.
Another form of sheet metal is the insulated aluma-flex duct. This
stuff is great, as long as you dont have to trim to fit or dont squash
it. It's very easily damaged, and no way to re-straighten it.
Personally I think you're far better off with R8, mylar jacketed flex
duct. Pricier than R4.2, but for mor energy efficient as well.
I hate Flex, and will not use more than 6' at any one time, properly
installed it will not need to be replaced, but we are one of those crazy
resi company's that use all metal except for returns and connectors
Are they still selling 4.2, I thought it all went to 6 and 8!
None of the vendors in my area are stocking R8, even though it's code
statewide. Most bldg dept's dont enforce it. I witnessed a remodel
of a City bldg where I pointed out the specific codes to the building
officials, and yet the R4.2 FSK remained.
So, is this another vote for zoning being more trouble than it's
worth? That seems to be what everyone is saying, here.
Well, it hasn't been spec'd yet, but that would be nice!
This is, in fact, for a custom home, designed from scratch, which is
why I'm soliciting advice here on what to tell the designer to include
to make the HVAC work as well as possible. I'll look into the flex you
mentioned, but I'm still leaning towards metal, if at all possible,
and trying to get the designer to leave adequate room to install it.
I'm sure you're right, though, it's going to be hard to find a
residential contractor to install metal. I've looked at a lot of new
homes lately (to get design ideas), and I always peek into the attic.
I've never seen anything other than miles of flex running every which
On custom homes we almost always zone the master suite from th erest of the
second floor, and the main living area (kitchen, family room, and entry from
th erest of the first) Seperate trunkline for each zone!
I tried to send this direct... it bounced.
I'm not re-writing so let the flame begin.
I posted at the long end of the replies... after reading the lot
If you want real zoning real comfort & few or no air handlers at all...
Go to mehvac.com
Mitsubishi Electric of America.
Look at the PUMY series of HVAC equipment.
The PUMY is an air source heat pump that can have up to 8 indoor units on a
single 4 ton outdoor.
The inverter drive operates from 30% to 130% (5tons) of capacity & is dirt
cheap to operate in comparison to anything else on the market.
The larger units PURY & PUHY's can handle up to 24 indoor units on a single
The PURY is a simultaneous heat & cool unit that's very efficient for
Neither the PURY of the PUHY are realistic for residential installs, but a
couple PUMY units will suit your purposes perfectly.
I have been working with these for a number of years & have had great
I hesitate to post this response in the newsgroup, as there are a number of
folk that would scream of blasphemy.
Most are air heads (force hot & cold air) & a few are wetheads (hot water
chilled water or DX) A few might have heard of "mini-split" systems, but
these are multiple minisplits for lack of a better word & I doubt many have
You might try posting a question in that regard.. I'd also "ping" Abbey
Normal in the group.
He's probably heard of / installed these as he's a tech in the islands...
these systems are going in al over FLA. & points south.
I've seen his posts around, but I haven't lurked this group for a while,
haven't posted for years. Too many control freaks as far as I'm concerned.
That said, find a good refrigeration contractor that's installed this system
before & I'll guarantee you'll love it.
Houston(?) is a perfect application as your heating design temps never reach
the subzero's as they do here in MN. & the units can provide heating easily
down to 15dF, a region I doubt Houston will rarely see.
This system will also win the praises of your designer as you'll need NO
mechanical space, or any you do use, for ducted units, will easily fit in
the soffit spaces you've already agreed upon.
Depending on the layout of the home, you could have a separate zone for
I'll recommend an ERV for ventilation as well, but that's an easy fix.
If your interested, I can contact Mitsubishi in Atlanta & ask them for a
list of the best contractors in your area.
I won't make a penny on it, but I hate to see a bad system put into a decent
I can also guarantee you'll save some serious cash on cost of operation & it
will pay for itself in less than 10 years, maybe less..
If I had a set of plans I could run a room by room load & cost analyze the
whole thing. I can lay it out on cad if you like.
That's what I do, as I stated in my post (the end of the longest thread)
I've been doing it for years & I do it well...
The only other thing I do well is snow ski, & I've done that since I was 2.
Well, I've heard of them, but have never seen one in any of the houses
we've toured. So, I'm pretty ignorant. Forced air is far and away the
only thing you see down here. In Houston, AC dominates of course, and
heating is usually an afterthought at best. Dehumidification is also a
key consideration, and especially so for me, as I'll be 3/8 mile from
a major river.
I'll definitely check it out.
15?! Yeah, we might see that once or twice...a decade. :-)
Yeah, I'm sure he'd like that!
Definitely looking at an ERV, anyway. And, from what I've read, in a
high humidity climate, it might make more sense to run completely
separate ductwork for it. If so, then the ERV could work with
Well, hold that thought! I'm still at the beginning design stage, so
it'll be a few weeks until the layout is finalized. But, I'm trying to
push the HVAC design considerations now so I can get these things
addressed before it's too late. Also pushing for extra insulation,
radiant barriers, low e windows, shading, attention to solar angles,
etc. in hopes of taking as much heat load off the building as I can.
Well, I'd rather not run the ducting all the way up to the attic, and
back down. In the closet would be good, if there's a convenient place
to branch off there. Otherwise, I guess I'm looking at access panels
in closets or something like that. Is that doable?
I hope they don't need much maintenance, but since they're electrical
AND mechanical ... well, sooner or later!
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