HVAC

[archive]

From: "Richard Downs" <richardd@u...>
Date: Sun Feb 25, 2001 5:05 am
Subject: HVAC

Hi Everyone,

I've been a member of this group for quite a while, reading and learning new
ideas and tips.

I've operated a home recording studio in Nashville for twenty years. Now,
we're moving... the neighborhood's gotten 'rougher'.

We're building a new home and studio which brings me to the questions I hope
you'll be able to answer. I will try to upload a floor plan for the studio
later this week... but for now my problem is the heating and air
conditioning. The studio is going to be in the basement of our home... and
has been designed to have 12 foot ceilings and will have approximately 2800
square feet. We're trying to save as much ceiling height as possible (of
course) and we're trying to stay isolated from the upstairs living area.

Because of the size of the studio, we had to put split HVAC units on the
outside and the inside. The heating and air conditioning contractor said
the 'return' would have to be some sort of ceiling chase... in anticipation
of the airtight rooms. He said to take the 'returns' up to the ceiling in
flex tubes - cut a vent in the ceiling and use the entire ceiling as a
'return'. Has anyone ever done this? And if so, what level of air noise, if
any, should I expect on this type of air flow system?

Also, has anyone done any work with Z channels for the ceiling? We're using
the 'silent floor' system for the upstairs living area - so I can use R-30
in the floor joists. Any other suggestions and opinions would be
appreciated.

Thanks
Richard Downs
DBS Studios
Cyber Productions
Nashville, TN

[archive]

From: mike+ dunn <-sub-space-@e...>
Date: Sun Feb 25, 2001 10:42 pm
Subject: Re: [acoustics] HVAC

I don't know if I understand your contracter's HVAC plan, it sounds like
he's suggesting you cut holes in your isolation ceiling and use the airspace
between it and the floor above as a return. I must have misinterpreted as
that would destroy any soundproofing benefit the iso ceiling was built
for...
I built my ceiling using 14" TGIs sloping from 10' to 14' high, 12' on
average. I stuffed it with 10" R-30 and ran Z channel perpindicular to the
joists, stopping before I hit the edge of the wall. I then screwed 5/8"
sheetrock into the channel, using short screws offset from the joists. I
left a 1/4" gap all the way around the wall edge and caulked it in. My HVAC
contracter wanted to cut holes in it so he could hide his flex duct up
there, but I qashed that idea.
I had him build a long, wide duct the length of the low wall with some
bends in it. From that we branched off the individual flex runs to the
various rooms. Where the flex penetrates the iso wall, I'm building
isolation shafts on the interior of the room where the wall meets the
ceiling. They look like a square chute framing in the ceiling, and allow me
to offset the interior vent holes from the exterior penetration by 4-8'.
Each individual leg is blocked off from the next, but inside the room it
looks like one continuous chute with multiple openings at the top of the low
wall. I'm putting in a large version of this chute that runs along one
floor/wall joint and then up the high wall to a large vent. This will
contain one 16" return and the outcropping it provides will be a bench for a
bunch of old tube amps to sit on.
I tried to make my runs as long as possible to the rooms, and once inside,
tried to move the vent opening as far as possible from the wall penetration.
I didn't want to bring my returns through the ceiling because with a 12'
height there's not a lot of room to spare up there.
HTH

[archive]

From: sjoerd@n...
Date: Tue Feb 27, 2001 8:41 am
Subject: Re: HVAC

--- In acoustics@y..., "Richard Downs" <richardd@u...> wrote:

"He said to take the 'returns' up to the ceiling in
> flex tubes - cut a vent in the ceiling and use the entire ceiling as a
> 'return'. Has anyone ever done this? And if so, what level of air
noise, if any, should I expect on this type of air flow system?

Totally agree with the other answer, iy seems your contractors
solution will jeopardise the acoustic integrity of the ceiling.
I have used a number of different methods, the most successful ones being:

- Build a long, narrow airway in the roof, almost the width of a room.
Put it in the right place and it will often give you additional
assistance with diffusion (which often means placing it about 2/3
towards the rear of the room). You can select a readily available
aluminum profile, or even better a "punched hole" type sheet.
Make it into a "soundproof" structure itself, so you don't have to
worry about it replacing insulation in the ceiling.

To minimise noise on your return(s) you can do a couple of things:

1. Do NOT let anyone sell you one of those "lifetime guaranteed -
never need to buy another one - good for alergies etc" kind of
filters. They are extremely noisy. Next one not to get are paper
filters - also noisy. Use the cheap blue-green nylon fiber ones, the
only good ones.
2. Use only quality insulated flex duct. We have found JPL Flex (from
Denver CO and Fresno CA) to be the most cost / quality effective ones.
Avoid using normal metal duct and insulating it - the end result will
be less effective compared to the flex duct no matter what insulation
you use.
3. I presume your intake will run to a collection point / fan chamber,
located in a seperate room / cupboard. Use extra flex duct, coil it
up and fill your extra space with it, you'll be amazed how much noise
this eliminates.
4. The more returns you use, the less noise you'll have. If you can
run 2 flex ducts instead of one to the fan chamber, do it.
5. If you can't build return chamber(s) into your ceiling, you can use
a standard twin 10" collection grill - providing you use coiled flex
duct behind it. Cheap solution.

In our current (under construction) place we have a large aircon /
central heating unit, which looks after over 52000 cubic foot, located
in a small room right next to the tracking room. The returns consist
of 2 x 10" returns from the tracking room, 1 x 5" return from the
control room, and 1 x 5' return from outside. There is NO noise, you
cannot hear, only feel, if the unit is running or not.

A final tip - if at all possible, try and get at least a 5 to 10%
intake with fresh air from outside, you'll be amazed how many
headaches that eliminates!!
Hope this is usefull, I can email you some pictures of our
installation if you like

[archive]

From: steve <whitaker@p...>
Date: Tue Feb 27, 2001 4:40 pm
Subject: Re: HVAC

Hello,

>The heating and air conditioning contractor said
>the 'return' would have to be some sort of ceiling chase... in
>anticipation of the airtight rooms. He said to take the 'returns' up
>to the ceiling in flex tubes - cut a vent in the ceiling and use the
>entire ceiling as a 'return'. Has anyone ever done this? And if so,
>what level of air noise, if any, should I expect on this type of air
>flow system?

I've done this WHEN I DIDN'T CARE ABOUT NOISE
it's good for offices and stores where the $$ saved makes sense.
It's not for you!

There have been a couple of good suggestions posted.
Go for one of them :-)

steve

[archive]

From: BASSMANCP@A...
Date: Tue Feb 27, 2001 4:52 pm
Subject: Re: [acoustics] Re: HVAC

>The heating and air conditioning contractor said
>the 'return' would have to be some sort of ceiling chase... in
>anticipation of the airtight rooms. He said to take the 'returns' up
>to the ceiling in flex tubes - cut a vent in the ceiling and use the
>entire ceiling as a 'return'. Has anyone ever done this? And if so,
>what level of air noise, if any, should I expect on this type of air
>flow system?

In a message dated 2/27/01 11:41:31 AM Eastern Standard Time,
whitaker@p... writes:

<<
I've done this WHEN I DIDN'T CARE ABOUT NOISE
it's good for offices and stores where the $$ saved makes sense.
It's not for you!

There have been a couple of good suggestions posted.
Go for one of them :-)

steve
>>

Steve that is good advice!! If the contractor does not build studios on
a regular basis, he/she will most likely not have a clue as to what real
sound isolation is. If he uses the whole ceiling as the return, you will in
effect be placing a resonance chamber between the ceiling and the
floor above it. If your contractor does not build studios regularly, KEEP
AN EYE ON EVERYTHING THEY DO!!!! even if you think you have
explained yourself thoroughly. Every time I use a contractor they always
want to revert to the way they're used to doing things.

Buyer Beware!!
Chris Preston

[archive]

From: "Richard Downs" <richardd@u...>
Date: Tue Feb 27, 2001 6:30 pm
Subject: RE: [acoustics] Re: HVAC

Thanks for the info. Sure I'd love to see the pics.The more information the
better.
I don't know if we can get any access to outside air it's totally
underground and 10"1/2 poured concrete walls.
Maybe the entrance/lobby?
I also have concerns about the ceiling? Don't know exactly what we are going
to do there yet.
I know fresh air is important especially in the middle of a 10hr. block with
a bunch of musicians.
If I do a tracking session now I have to leave the AC/Fan running all the
time.

-----Original Message-----
From: sjoerd@n... [mailto:sjoerd@n...]
Sent: Tuesday, February 27, 2001 2:42 AM
To: acoustics@y??????roups.com
Subject: [acoustics] Re: HVAC

--- In acoustics@y..., "Richard Downs" <richardd@u...> wrote:

"He said to take the 'returns' up to the ceiling in
> flex tubes - cut a vent in the ceiling and use the entire ceiling as a
> 'return'. Has anyone ever done this? And if so, what level of air
noise, if any, should I expect on this type of air flow system?

Totally agree with the other answer, iy seems your contractors
solution will jeopardise the acoustic integrity of the ceiling.
I have used a number of different methods, the most successful ones being:

- Build a long, narrow airway in the roof, almost the width of a room.
Put it in the right place and it will often give you additional
assistance with diffusion (which often means placing it about 2/3
towards the rear of the room). You can select a readily available
aluminum profile, or even better a "punched hole" type sheet.
Make it into a "soundproof" structure itself, so you don't have to
worry about it replacing insulation in the ceiling.

To minimise noise on your return(s) you can do a couple of things:

1. Do NOT let anyone sell you one of those "lifetime guaranteed -
never need to buy another one - good for alergies etc" kind of
filters. They are extremely noisy. Next one not to get are paper
filters - also noisy. Use the cheap blue-green nylon fiber ones, the
only good ones.
2. Use only quality insulated flex duct. We have found JPL Flex (from
Denver CO and Fresno CA) to be the most cost / quality effective ones.
Avoid using normal metal duct and insulating it - the end result will
be less effective compared to the flex duct no matter what insulation
you use.
3. I presume your intake will run to a collection point / fan chamber,
located in a seperate room / cupboard. Use extra flex duct, coil it
up and fill your extra space with it, you'll be amazed how much noise
this eliminates.
4. The more returns you use, the less noise you'll have. If you can
run 2 flex ducts instead of one to the fan chamber, do it.
5. If you can't build return chamber(s) into your ceiling, you can use
a standard twin 10" collection grill - providing you use coiled flex
duct behind it. Cheap solution.

In our current (under construction) place we have a large aircon /
central heating unit, which looks after over 52000 cubic foot, located
in a small room right next to the tracking room. The returns consist
of 2 x 10" returns from the tracking room, 1 x 5" return from the
control room, and 1 x 5' return from outside. There is NO noise, you
cannot hear, only feel, if the unit is running or not.

A final tip - if at all possible, try and get at least a 5 to 10%
intake with fresh air from outside, you'll be amazed how many
headaches that eliminates!!
Hope this is usefull, I can email you some pictures of our
installation if you like

For more info, unsubscribe, large file uploads, ect:
http://www.studiotips.com
Send small drawing files to dan@s...
To Unsubscribe: Send email to
acoustics-unsubscribe@e????ups.com

[archive]

From: steve <whitaker@p...>
Date: Tue Feb 27, 2001 7:00 pm
Subject: Re: HVAC

hello,

>I don't know if we can get any access to outside air it's totally
>underground and 10"1/2 poured concrete walls.

Fresh outside air is a real pain to get, but (imo) well worth the fight.
wishing you success :-)

Steve

[archive]

From: "Dave Martin" <dave.martin@n...>
Date: Tue Feb 27, 2001 7:14 pm
Subject: Re: [acoustics] Re: HVAC

Richard, if you haven't signed a contract yet with your HVAC guy, you might
want to have Ted Conrad at Accurate Air give you a bid. He did the Tracking
room as well as Soundstage, and really knows what he's doing with studios.
He ain't cheap, but who is?

You can e-mail me off list for a number if you want, since my Rolodex isn't
handy right now.

Dave Martin
DMA, Inc.
Nashville, TN

[archive]

From: sjoerd@n...
Date: Wed Feb 28, 2001 10:47 am
Subject: Re: HVAC

>
> >I don't know if we can get any access to outside air it's totally
> >underground and 10"1/2 poured concrete walls.
>

but....but....but.... You're having a unit installed with the
refrigiration unit outside and the blower inside right?
This means you will have to have a run from the inside- to the outside
unit (normally one small diameter brass pipe and a low voltage wire).
Perhaps use the same run for a 5" flex duct?

Regarding your upstairs / downstairs insulation - Difficult to make
any suggestions without knowing the construction of the house.
My favorite method is using Pacific Gold Board. This is a 2 1/4" thick
board made from compressed wheat staw. Looks like a very thick sheet
of drywall, and it has an STC rating of 33. It is dense and heavy.
If you have a ceiling of 2 x 6 fir you could fill the cavity with
glasswool and apply the PGB under it.
A very cool method is to screw the PGB to the frame, and then screw
lats (something like 1 x 3") over the joints, through the PGB into the
frame. This does not only give the structure extra strength, you have
an additional frame. Cover this frame with sheets of material to suit
your acoustic requirements. For instance - for low frequency
trapping, use sheets of 1/4" finishing ply and you'll have very
effective low frequency absorbsion.

Of cause.... you could go totally anal and tune your whole ceiling.
Thought you were talking to a level headed old sound guy here? Think
again! As I'm building my own place this time, instead of designing /
fixing / working in other places, I've got stark raving over the top
(but it sounds gooooooooood, with bass as tight as a duck's ass, and
that's water tight!) Hey I'm on a roll, might as well tell you about
my control room ceiling.
2 x 6 redwood frame, filled with 6" cellulose insulation. 1/2"
soundboard stapled to the frame. Then 3/4" ply screwed on top of that.
Before fitting the ply, glued a layer of AST30 felt to it. The side
with the AST went against the soundboard. Then stapled & glued a
frame of 3/4" x 3" wide ply against it. Stapled welding rod onto this
frame, each rod set 1/2" inside the edge of the lats. Over this
sheets of 1/2" ply, secured with rows of small screws. The screws
were torqued at certain settings, thereby tensioning the ply over the
welding rod. This allowed for each panel to be tuned precisely.
As all walls are at 22 degree angles (apart from the side walls -
think of a church shape - in the width), this leads to a room with
predictable characteristics. Low frequency is directed to the front
and rear bottom corners, as well as, slightly less so, to the peak in
the center of the room. Therefore the panels are tuned, from the
front (monitor wall) to the rear: 3rd octave - 2nd - 1st (front of
peak) - 3rd - 2nd - first.
It took about 2 1/2 days extra work, was very cheap on materials and
totally worth it. I measured the room before and after and the
difference was pretty amazing, reducing the need for traps in the
corners by over 30%.
Just in case you wonder "why didn't he just use drywall?". Answer 1 -
I might be slightly deranged. Answer 2 - with 6" of cellulose in the
roof there is no problem with highs / mids coming in or going out.
The characteristics of thick plywood are pretty lousy at highs / mids
(compared to drywall), but better at lower frequencies.Whats more fun
then writing about sound? Sleeping???? Goodnight!!

[archive]

From: "Hill, Scott (S.E.)" <shill7@v...>
Date: Wed Feb 28, 2001 1:22 pm
Subject: RE: [acoustics] Re: HVAC

Could you clarify for me a few points about your ceiling design that you
describe below?
1) Are the welding rods on only one edge of each sheet of 1/2" ply, on 2
edges, or all 4 edges?
2) What is the diameter of the rods? Is each panel "tuned" according to the
torque on the screws or by the cavity depth between the 1/2" ply and the
3/4" ply?
3) You mention that "...all walls are at 22 degree angles (apart from the
side walls...)", does this mean that the ceiling slopes at a 22 degree angle
with a peak in the center, and the front and rear walls lean in toward the
center of the room?
Thanks in advance for your reply.
Scott

-----Original Message-----
From: sjoerd@n... [mailto:sjoerd@n...]
Sent: Wednesday, February 28, 2001 5:47 AM
To: acoustics@y??????roups.com
Subject: [acoustics] Re: HVAC

>
> >I don't know if we can get any access to outside air it's totally
> >underground and 10"1/2 poured concrete walls.
>

but....but....but.... You're having a unit installed with the
refrigiration unit outside and the blower inside right?
This means you will have to have a run from the inside- to the outside
unit (normally one small diameter brass pipe and a low voltage wire).
Perhaps use the same run for a 5" flex duct?

Regarding your upstairs / downstairs insulation - Difficult to make
any suggestions without knowing the construction of the house.
My favorite method is using Pacific Gold Board. This is a 2 1/4" thick
board made from compressed wheat staw. Looks like a very thick sheet
of drywall, and it has an STC rating of 33. It is dense and heavy.
If you have a ceiling of 2 x 6 fir you could fill the cavity with
glasswool and apply the PGB under it.
A very cool method is to screw the PGB to the frame, and then screw
lats (something like 1 x 3") over the joints, through the PGB into the
frame. This does not only give the structure extra strength, you have
an additional frame. Cover this frame with sheets of material to suit
your acoustic requirements. For instance - for low frequency
trapping, use sheets of 1/4" finishing ply and you'll have very
effective low frequency absorbsion.

Of cause.... you could go totally anal and tune your whole ceiling.
Thought you were talking to a level headed old sound guy here? Think
again! As I'm building my own place this time, instead of designing /
fixing / working in other places, I've got stark raving over the top
(but it sounds gooooooooood, with bass as tight as a duck's ass, and
that's water tight!) Hey I'm on a roll, might as well tell you about
my control room ceiling.
2 x 6 redwood frame, filled with 6" cellulose insulation. 1/2"
soundboard stapled to the frame. Then 3/4" ply screwed on top of that.
Before fitting the ply, glued a layer of AST30 felt to it. The side
with the AST went against the soundboard. Then stapled & glued a
frame of 3/4" x 3" wide ply against it. Stapled welding rod onto this
frame, each rod set 1/2" inside the edge of the lats. Over this
sheets of 1/2" ply, secured with rows of small screws. The screws
were torqued at certain settings, thereby tensioning the ply over the
welding rod. This allowed for each panel to be tuned precisely.
As all walls are at 22 degree angles (apart from the side walls -
think of a church shape - in the width), this leads to a room with
predictable characteristics. Low frequency is directed to the front
and rear bottom corners, as well as, slightly less so, to the peak in
the center of the room. Therefore the panels are tuned, from the
front (monitor wall) to the rear: 3rd octave - 2nd - 1st (front of
peak) - 3rd - 2nd - first.
It took about 2 1/2 days extra work, was very cheap on materials and
totally worth it. I measured the room before and after and the
difference was pretty amazing, reducing the need for traps in the
corners by over 30%.
Just in case you wonder "why didn't he just use drywall?". Answer 1 -
I might be slightly deranged. Answer 2 - with 6" of cellulose in the
roof there is no problem with highs / mids coming in or going out.
The characteristics of thick plywood are pretty lousy at highs / mids
(compared to drywall), but better at lower frequencies.Whats more fun
then writing about sound? Sleeping???? Goodnight!!

[archive]

From: sjoerd@n...
Date: Thu Mar 1, 2001 2:16 am
Subject: Re: HVAC

--- In acoustics@y..., "Hill, Scott (S.E.)" <shill7@v...> wrote:
> Could you clarify for me a few points about your ceiling design that you
> describe below?
> 1) Are the welding rods on only one edge of each sheet of 1/2" ply, on 2
> edges, or all 4 edges?
> 2) What is the diameter of the rods? Is each panel "tuned"
according to the
> torque on the screws or by the cavity depth between the 1/2" ply and the
> 3/4" ply?
> 3) You mention that "...all walls are at 22 degree angles (apart
from the
> side walls...)", does this mean that the ceiling slopes at a 22
degree angle
> with a peak in the center, and the front and rear walls lean in
toward the
> center of the room?
> Thanks in advance for your reply.
> Scott
>
>OK, I'll try...its easier to draw it really.
1) The welding rods - there are 2 on each strip of wood, apart from on the
strips adjoining the walls. So, where the sheets of ply join in the center
of a strip, the edge of each sheet it pulled over the rod. I made a rough
scetch, attached.
2) Standard welding rod, the cheap stuff. Watch the quality of your ply or
wooden strips, some wood is to soft and the rod pushes into the wood -
effect gone. Best is to use a low grade hardwood like redwood or finishing
ply. Just think of the rods as the steel rim of a drum, the ply sheets as
the skin. Make sure there is a small gap where the sheets of ply meet.
I got the idea when I made a table drum. Very much recommended to do
something like that to practise first. Just get some 2 x 3, make it
into a
frame, apply the rods and a sheet of thin ply. You can make it any size,
but its best not to go smaller than 2 by 2 feet. You have to
pre-drill the
screw holes and countersink them carefully (its gotta look nice).
Space the
screws (small drywall screws - the cheapest and best ones for this)
about 4"
from each other to start with, and screw them in with your driver at its
lowest torque setting. Increase the torque setting evenly all around
until
you have it to your liking, use it as the top for a small table and
varnish
it. One of the first ones I made was used by Mick Fleetwood, he refused to
give it back, and that was about 12 years ago. I ask him to give it
back as
"standard practise" every time I see him, and then he just smiles at
me and
says "no" (he's to big to tackle).
3) Yes - see picture enclosed.