You would like my attic Steve, about a degree warmer than the space
Attic is sealed, white standing seam metal reflects the heat,
styrofoam below the standing seam keeps the left over heat from making
it into the attic. Maybe its R7 but it smokes fibreglass insualtion
and a vented attic
when I have to crawl in to a hot attic your going to buy something
you could even end up getting sould a new furnice installed in the closet
there is no such a thing as a cool attic in the summer
standing seam roofs do not reflect heat lay some sheet metal out in the
summer sun and try picking it up after an hour or so
It's a roof that is externally insulated. The standing seam is on top
of the insulation. Attic is a less than two degrees warmer than the
air conditioned space below.
The sealed, insulated attic keeps the heat out in the first place.
Vented attics are for ice dams. This is a year round cooling
Well, I agree with you, there.
Around here (Houston, Texas) pretty much all the installs I've seen
look like the "giant silver octopus," which is to say the air handler
is smack dab in the middle of the attic, with a tiny plenum, and miles
of flex duct running every-which-way from it.
I'd like to try to do better!
yeah, well just wait until its time to replace it.
how many times have we seen a furnace in an attic that the only way to
get it out and a new one in is to cut a hole in the roof.
Or when there's a condensate drain issue and water backs up,
overflows, and ruins sheet rock ceilings.
Your designer probably isn't a HVAC designer...
If he's ever removed an air handler, or even a component, out of an attic,
he'd probably be able to tell you there is much added expense incurred in
dealing with the conditions of the attic (temperature & space) & keeping the
house clean as he moves out the old & in the new.
Up here in MN we have basements for our equipment.
Second, if he or anyone, is recommending flex duct, make sure they can
justify the added duct dimensions required.
Flex duct needs to be up sized at least one dimension in order to allow for
the static pressure increase inherent to the duct. I've been designing HVAC
systems for over 12 years now & never allow more than 6' for the final
My recommendation would be a main floor closet installation (in the best of
all possible worlds it would be a straight shot in from the driveway side
door that would allow a 2 wheeler clear passage to & fro)
The mains would be sized for a trunk serving the upstairs from floor
diffusers & the main floor from the ceiling.
I'd then try routing the majority of return air from high wall (or ceiling)
mounted return grilles. The main floor would also have high returns.
Remember the warm air from the main floor will migrate to the upper floor,
so a return in the stairwell will serve as a lower level return. A SA & RA
main would also need to be run to the 1/2 story attic.
Since I don't have load calcs I'll assume your running between 600-750 per
If the floors are 2000\\2000\\1000 sq.ft.
your looking for between 2-1/2\\2-1/2\\2 tons to 3\\3\\2 tons.
(Have your local contractor verify these loads before signing anything.)
In this case I'd install a unit on the main floor with ceiling SA & RA
grilles & a 2nd unit on the 2nd floor serving floor & ceiling grilles as
(of course the 2nd floor parking level would allow a straight shot as well
If most of the areas are on the main floor, I don't see a need for zoning,
but a simple system should be easy enough to install for the kitchen & other
spaces. Zoning the upper floor might be required for master bedroom suites,
bedrooms, office areas, etc... but without plans I wouldn't venture a guess.
My background has leads me to believe a well designed residential system,
with proper installation (i.e. no flex) & a decent air balance, with a room
by room heat loss & balance report, won't need zoning.
In an effort to produce the maximum amount of flames, I'll go further &
suggest these options:
If I were to zone 2 systems on 2 levels, as afore mentioned, I would install
bypass dampers that dumped the air to the other level via grilles serving
the space rather than directly back to the return of the zoned system.
I would consider installing an air source a heatpump to one of the 2
systems, probably the lower & use electric strip for heat in the other, that
would all depend on electric & gas rates, & cost of up grade. Truth told I'd
install HPs on both systems. High Seer cooling & staged heating...
I will never consider a constant volume blower in any home I'd build.
I replaced a CV with a variable speed furnace a couple years ago & have been
saving $15.00 a month on electric with the fan on constantly, which by the
way is the best way to insure even temperatures throughout the home.
On that I'll stake a claim.
Just remember, why would you want to cut corners on your future comfort...
Why save $5000.00 to be uncomfortable in your $500000.00 home (prices may
Pay for decent equipment now by forgoing the granite counter top etc...
In a few years you can "remodel" the kitchen by swapping Formica with
granite, upgrading the faucets, etc...
then the wife will be happy a 2nd time.
Now I'll don the firesuit & read the replies...
Since we're running a return duct system for ceiling mount grilles, I'd
throw another, but not the only one, into the stairwell space. Proper
airflow is vital & return is just as important as supply... nomatter what
they say, it's a blower not a sucker.
The initial post stated a 2-1/2 story, so I'm assuming there's an attice
office or some other occupied space.
My kids would kill me if they saw me do that after i yekk at them for
holding the fridge door open (in hopes of something better showing itself)
This is just a theory I've come across lately, but it make some sense.
First, in my neck of the woods heating is the priority.
In one of the previous posts someone mentioned bypassing cold air back to
the unit & shutting down on high head...
stated "too cold". Well, we've got just the opposite problem here.
If a system is sized with multiple zones & only one calls, say the smallest
one 150 cfm out of a 1000 cfm system. We'll be bypassing the (50%) of the
non-calling zones, or 425 cfm of 120dF air. Mix that with the 70dF air via
return grille & our mixed air will be about 90dF throw that through a 50dF
heat exchanger & the over heats start popping. Same principle in the cooling
mode, just different temps & sensors.
By bypassing to the non calling system, operating on low airflow we're able
to"dump the bypass, insure safer operation of the system & the btu's won't
be wasted. This, of course, only works in a multiple system configuration,
and is as I said a theory...
Your gonna love the response I posted just prior to this regarding
Mitsubishi mini splits w/ multiple indoor units on a single outdoor...
They're finally moving inverter drives & multi-minis into the residential
Besides my Geothermal experience is in -20F winter design territory...
Thanks... I've been here for years, but quit posting about 8 yrs. ago.
The flames were too... obnoxious?
Well, it indeed is not really an "attic" in the classic sense. There's
about 600-700 sqft of living space there, which leaves precious little
attic space left for storage. I'm fighting to keep it, instead of
having it stuffed full of air handlers and flex duct, which is what
started this discussion.
Well, I'm seriously considering it! We have a couple of acres, so we
should be able to run slinky pipe, or do wells. We need a water well
anyway, so maybe we could get a package deal from the driller. :-)
That's an interesting idea. I'll have to research those a bit more. My
initial reaction is that we're going to have quite a number of smaller
rooms, closets, and other spaces that we'd at least like to have air
circulation in, and it might be difficult to do that with a ductless
system. But, I'm fairly ignorant about them.
Me too. As a longtime lurker, I'm trying to put to use what I've
learned and not cut those corners. It's tough, though, when the state
of the are around here is to put 'em in the attic, and run flex
everywhere. But, I'm trying!
There are only a couple folks allowed to make that decision... You & your
If you builder or contractor start telling you... or your designer for that
matter... find someone else.
It's you name on the mortgage payment for the next 30 yrs.
If you decide on geothermal...
igspha is in Tulsa & on the web. do a search for the heat pump consortium.
both can put you in touch with installers & contractors.
Make sure they're Igspha trained & certified.
If your well driller has done geo great, if not you'll need another. The
rule for geo installed is $1500-$2000 per ton for a loop field installed.
7-9 tons might get you a better rate but not much.
Horizontal slinkys are great if your moving allot of earth anyways.
You'll need 3-4' wide 7' deep 100' long trenches 6-8' apart for each ton.
I'd seriously look at the mitsu first as I think it's gonna take a big chunk
out of geo's market...
If your going for a "close to green" building, geo & mitsu could get you
I've never seen a LEEDs certified bldg with standard A/C.
True, but since he's probably not going into the contracting business I
doubt he cares.
It's a realistic number in most areas, & the final bid from the contractor
will include it.
For a budget number it's sound...
The geothermal & the Mitsubishi systems use R-410A as well, & are as "real"
as any conventional system out there.
The only problem is, when in operation they save so much more money.
I'll give you the up front cost argument, but a conventional multi unit
zoned, multi story, ducted system, using variable speed blowers & air source
heat pumps isn't cheap either.
The initial cost difference will be paid back in a matter of years.
3-5 would be my guess but it could reach the 7-10 year range.
A friend of mine built a "mechanical room" in his house.He put his breaker
panel,a/c, water heater,water softener,washer,and dryer
in one room.The room had a floor drain,powervent and a large door to the
outside.If I ever build another house I will probably do the same.
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