Marc's Patio & Garage Studio

rod gervais · Post by **rod gervais** » Thu Apr 05, 2007 9:29 am

guitardad72 wrote:

Well yes... the room can not go without cooling so it has to be hooked up to the existing central air OR have it's own HVAC cooling system.

If the room (as planned) is hooked up to the existing central air and the room is vented to the outside then all the conditioned air and fresh air with 89% humidity would get mixed via my room... essentially adding the fresh humid air to the house.

Marc......

like I said- tie a 4" directly to the 12" supply entering your room - install a fan capable of 30 cfm

That mixes with the air in the12" supply - so if you were feeding 100 cfm from the supply - it would now be 130 cfm -= with 23% of that being fresh air.............

now install another 4" - tie it into your return - and duct outside - install a barometric damper on it - set to dump 30 cfm when the room pressurizes.........

Now you're back to 100 cfm returning to the unit - of which - worse case - 77% is fresh air- whic means you have to dehumidify 23.1 cfm of
un-blended air...............

Heck- you bring morethan that into the house - for your system to deal with - if you even THINK about opening a door.........

Please show him the numbers, then him I would love to see his calculations if he woud be kind enough to let me.

Sincerely

Rod

Post by **sharward** » Thu Apr 05, 2007 10:23 am

Wouldn't an HRV connected in the same fashion be more efficient in the long term, Rod?

Of course, my understanding is that HRVs tend to be much more efficient in preserving heat on cold days, rather than preserving cool on hot days...

--Keith

rod gervais · Post by **rod gervais** » Thu Apr 05, 2007 2:25 pm

sharward wrote:Wouldn't an HRV connected in the same fashion be more efficient in the long term, Rod?

Of course, my understanding is that HRVs tend to be much more efficient in preserving heat on cold days, rather than preserving cool on hot days...

--Keith

Not when you're talking about this small a quanity it wouldn't......... and I believe that for cooling loads it's an ERV that you us - they have dissacant dehumidifiers in them......

But still not cost effective for this - they are intended as whole house systems..... or at least for large zones with much larger amounts of fresh air than we're speaking ofhere.

Rod

guitardad72 · Post by **guitardad72** » Fri Apr 06, 2007 1:16 am

I did a gig last night, have 6 more in the next 3 days. Couldn't help but think about this all last night. I wanted a real life example of 30 CFM and Rod clearly posted this on my thread. THANK_YOU

I'm going to add a fresh air intake to my room. but still wonder if I open every my door 15 to 30 mins to have a smoke outside, only close inner door when needed (remember I got a week outer/exterior door with window that does not open but made this choice for natural light and to break sound iso on purpose) combined with just HVAC from house if I'd be fine... besides the point I realize and I don't plan to be a smoker forever, so... just had to say it but I am still going to add the fresh air intake.

Got more research to do.

Only thing that's really got me is how a fan set to 30CFM is going to kick back pressure of my air handlers fan and not let air out (go backwards) of a fresh air supply duct connected to my supply HVAC duct for room. My air handler is 40,000 BTUH, 3.5 tons. The fan is really strong. My HVAC guy suggested it's pushing 600 cfm BUT I could be totally wrong on what he said/can't remember/I think he was guesing... I just know it blows real hard and then I'd have to figure out the cfm by counting my registers in my house, so on and so forth. Every register in the house moves enough air to blow dry hair... I got to figure it out.

OR is this really where the barometric damper on the return kicks in?

My air handler model # TWE040E13FB2 but the closet model I can find info online is TWE040E13F. It has the name American Standard on it but it's really a Trane:
http://www.trane.com/Residential/Produc ... Speed.aspx

Sharward,

I read this (quote below) the other night. ERV would be better in my case BUT reading the last line in the following quote (have not looked up other source for 3 opinions yet), Rod's words, knowing my current HVAC removes more than 5 gallons of water from my house per day (I keep a 5 gallon bucket under the drip and use it for watering plants) and the additional cost I think NO ERV.

ERVs are especially recommended in climates where cooling loads place strong demands on HVAC systems. However, keep in mind that ERVs are not dehumidifiers. They transfer moisture from the humid air stream (incoming outdoor air in the summer) to the exhaust air stream. But, the dessicant wheels used in many ERVs become saturated fairly quickly and the moisture transfer mechanism becomes less effective with successive hot, humid periods.

Source: http://www.toolbase.org/Technology-Inve ... entilators

There is more good info on that site too: http://www.toolbase.org/TechInventory/t ... tailID=797

Go to run to the next gig, hopefully I'll have this all figured out by next week and will post a drawing for review with calculations.

Marc

rod gervais · Post by **rod gervais** » Fri Apr 06, 2007 2:57 am

guitardad72 wrote:I did a gig last night, have 6 more in the next 3 days.

Marc,

congrats on the gigs........

guitardad72 wrote:Only thing that's really got me is how a fan set to 30CFM is going to kick back pressure of my air handlers fan and not let air out (go backwards) of a fresh air supply duct connected to my supply HVAC duct for room. My air handler is 40,000 BTUH, 3.5 tons. The fan is really strong. My HVAC guy suggested it's pushing 600 cfm BUT I could be totally wrong on what he said/can't remember/I think he was guesing... I just know it blows real hard and then I'd have to figure out the cfm by counting my registers in my house, so on and so forth. Every register in the house moves enough air to blow dry hair... I got to figure it out.

OR is this really where the barometric damper on the return kicks in?

You got it - that is why the barometric damper is required.........

As I explained earlier - where I am suggesting to place this is NOT where I would normally put it........ but you don't have a whole lot of options here..... not without messing with the existing system - and then a whole slew of ploblems because there is no wat to for the fresh air t go just to that room - so it has to tie into the durct work off the trunk line to be dedicated for your room.

The trick is this - how many cfm go to your room -

what size is the duct feeding it?

how many feet of duct?

then I can calculate the static pressure - and spec a fan that will deliver 30 cfm at just above that static.......

it has nothing to do with the cfm - the static pressure is everything.......

for example- 12" round duct - doesn't develope 1" of static (back) pressure until you reach about 2300 cfm for 100' of pipe -

At 400 cfm - the static pressure is only (the same 100') .039"wc.

So if that were the case I would spec a fan capable of delivering what was needed......

example:

Duct Fan FANTECH FR-100 - grainger price 184.00
Type Centrifugal, In-line
Fits Duct Dia. (In.) 4
Inlet and Outlet Dia. (In.) 3 7/8
CFM @ 0.000-In. SP 122
CFM @ 0.200-In. SP 100
CFM @ 0.400-In. SP 78
CFM @ 0.600-In. SP 55
CFM @ 0.800-In. SP 15
Max. Inlet Temp. (Deg. F) 140
Voltage 115
Hz 60
Phase Single
Max. Amps 0.18
Max. Wattage 19
Motor RPM 2900
Motor Enclosure Totally Enclosed
Bearing Type Ball
Housing Dia. (In.) 9 1/2
Length (In.) 9 5/8
Flange Width (In.) 7/8
Speed Control 4YC44
Housing Material Thermoplastic
Mounting Position Horizontal or Vertical
Agency Compliance C-UL-US
Includes Mounting Bracket

2 each 2C905 Roof Cap BROAN 636 $15.06
1DGV1 Fan Speed Control,3 A DAYTON 1DGV1 $20.45

And then add to that the cost of 1 barometric damper - 1 balancing damper - and what? 30 feet of 4" round galvanized duct.

sequence -

verify existing air flow with Lo Flo Balometer prior to running or adjusting supply air fan.

assume for this exercise that yu are getting 400 cfm.

Install fan w/ balancing damper on load side of fan - and tie into system.....

On low fan setting - (with barometric damper wide open) adjust damper until air flow is 430 cfm measure with Low Flo Balometer

Balancing Comment regaring balometers and air balancing in general:

your HVAC buddy should either have one of these - or be able to borrow one - they are much more accurate than the small handheld electronic Anemometer.

Generally the techs do not take enough point readings with an Anemometer to report actual conditions - and small variances can add up to fairly large decrepiancies in actual flow rates.

The balometer is a one shot deal - if calibrated properly you can't get more accurate readings.

they look like this:

http://www.alnor.com/products/balometer-loflo.aspx

where as the anemometer looks like this:

http://www.omega.com/Green/pdf/AIRFLOW_MEAS_REF.pdf

Now adjust the barometric damper to dump 30 cfm with fan on low. This will be only partly open.

After this - switch fan to meduim and high - test and verify actual air at the supply register.........

the 30 cfm in low setting will satisfy 2 people- for each additional 15cfm in the higher settings - you can safely add another person...... the barometric will automatically open to allow the excess air flow to escape if using higher fan settings.....

See how easy that is?

Sincerely,

Rod

guitardad72 · Post by **guitardad72** » Wed Apr 11, 2007 1:24 pm

PROGRESS:

The screen wall for my patio got put in today. My drummer friend (who owed me a favor or two) installed it with my help for about $100 over the cost of materials. Total cost was $450, but he would have charged $750 if he did not owe me the favor and was not hungry for gigs

PLUS he did a great job, appears to know screen and aluminim well and went the extra mile. I am not going to confirm that, I just want to be left with a completely positive feeiling about my buddy who is a subcontractor. This part of my build has nothing to do with sound isolation and did not have to meet any real code.... if he did do something wrong I do not want to know.

I'll get pics of the screen wall tomorrow when it's daylight again. Does it ever make my (new smaller) patio, seem smaller.

Only other surprise was how my buddy referred to the aluminum door frame and chair rail (horizontal bar in screen, chair height) feeling really tight and steady. Compared to the 2x4 frame wall and door frame I just built... well can't compare, the screen is just for keeping the bugs out.

Rod,

congrats on the gigs........

I could elaborate on that positively and show my ego OR negatively and come closer to the truth, so I'll refrain. Just glad I'm working and feel lucky to be able to support my family via playing music for a living. Not many who want to, can.

I'm still working on a diagram of my HVAC but I got a couple questions:

You keep mentioning 12" duct for examples. I wanted to use 8", HVAC guy said 6" and we agreed on 7". HVAC guy says smaller duct for my room will be easier to balance room to the house.

1. Do you have an opinion on duct size I should use from my air handler to and from my room?

Silencer:
As Sharward noted recently on his thread, previously there were not to many clear plans or pics of silencers on this forum (or in your book

) The best silencer diagram now seems to be yours:
http://johnlsayers.com/phpBB2/download.php?id=16137
THANK-YOU

2. If I were to build this silencer for a 7" duct I would increase the silencer size in your diagram... basically every where you're noting 12" in box I increase to 14" and increase every other measurement proportionally (so the air moves twice as slow through the box)...or larger to be safe.... or the larger the better.... just make sure entry and exit of box is the same size?

I think I'm going to build the silencer box(s) out of 3/4" plywood because I have a lot of 3/4 plywood sitting around. Going to build at least one on the outer side of room (in attic) and place just before air passes through wall.
Then I'm thinking about building another set of silencer boxes in the room, or more like in between the inner and outer leafs because of the available space.
I've seen you advice (I think) 1 silencer box per duct run through wall as well as 2 silencer boxes (one on either side of wall).

3. For a room such as mine: Goal STC 65, TL @ 50hz -30dB via double frame walls 2 layers (or better) of 5/8" drywall etc...
Do you have a recommendation for how many/how much silencer box to use.

The 4" fresh air supply duct I'm thinking on feeding directly to the silencer box instead of Y'n into the HVAC supply duct. I'm thinking this would be hard to give an opinion on unless I provide a diagram BUT I've not yet made up my mind what exterior wall, soffit/overhang or roof I am going to run the fresh air ducts to.

4. If I had a long enough run, and 2- 90 degree turns could I run the fresh air duct straight into a silencer box with out causing problems.

I want the ability to "shut the window" or close off the fresh air while not in use. Fresh air supply duct gets a fan and a full closing damper. Return gets barometric damper and a full closing damper. Full closing dampers would be the ones when power is off they close so I can hook these up with fan to one switch. Goal is that when I am not in room, fan is off I close those vents so conditioned air is not flowing out them.

5. Any potential hazard with the OFF fresh air switch besides letting the occupant have control for potential suffocation?

6. I'm thinking about full OFF/ON dampers to shut HVAC/conditioned air off to the room. This way when it is cooler out I can just give myself fresh air.

Sharward is planning the supply fresh air vent under a soffit/overhang on a cooler side of his house. Rod has (only) suggested I go in and out of my roof. The closest soffit on north (cooler side) of my house is right over my noisy HVAC heat pump/condenser unit. To get to another spot on north side of house away from condensor I'd have to run 30' and install duct in a spot in attic that would for sure warrant a 1,000 word post ranting on how I hate my attic.

7. Do you (or anybody) think it will make that much of a difference in temperature of air coming in to run fresh air supply to a shadier/cooler part of exterior on the house?

I realize I may not have given enough info for some of above to be answered

, some info I don't have.

Dang I didn't mean for this post to be this long.

Marc

rod gervais · Post by **rod gervais** » Wed Apr 11, 2007 9:18 pm

how much air did he say he's going to supply you through that 7" duct?

XXXX cfm......... ???????????????????

The reason I insert the fresh air where I do is so that it will have a chance to mix completely before entering the room............

I'll get back to you on the rest.........

Rod

guitardad72 · Post by **guitardad72** » Thu Apr 12, 2007 2:38 am

See pics of Screen Wall below. Still have to caulk around the perimeter. Then I can rebuild and clean up my garden area, re-install drip system, hanging plants in patio, etc...

Rod,

how much air did he say he's going to supply you through that 7" duct?

XXXX cfm......... ???????????????????

Don't know. Maybe he guessed at 100 cfm? BUT wouldn't I more being going for the "correct feel" number for the room... once the balancing damper on supply is in (closing to 80% max) then I will adjust that till the temperature feels right in the room, this will decrease the cfm to room (right?). Think I am going to install a manual controlled balancing damper with in easy reach of my attic access.

Shouldn't I be asking him for a guess number of what cfm should be going to my room of 130 sqft/ less then 1,000 cubic feet, all based on our local temperatures, insulation of room, my air handler, etc... OR does this sound like a number I truly won't be able to measure till it's all installed? Maybe I'm over-thinking this but I will ask him tonight, I have to show off my new screen wall.

BTW My HVAC guy is my neighbor, friend, our kids play together and we help each other out with house hold projects when needed. He helped me with my recent ceiling drywall, I helped him with drywall in his bath, etc...

AND I've not yet told him that I am going to install the fresh air ducts.

The reason I insert the fresh air where I do is so that it will have a chance to mix completely before entering the room............

Maybe I over thought that too. Thinking was it would be an easier install and somewhat cheaper to run both conditioned and fresh air ducts to silencer box. BUT if the fresh air duct Y's into the conditioned air duct at some distance before the silencer box then it would be less likely for noise to travel from outside into room, so that's making more sense to me, even if it's only a small difference.

The only other info I got right now is the conditioned air supply duct will be about 20' to 25'. The return will be 15' to 20' long. Both will have 2 90 degree turns with those lengths BUT...

Question: HVAC guy said just curving the duct around would be enough to stop sound from passing through ducts. Does it have to be 2- 90 degree turns OR can the duct curve around a min of 180 degrees. I'm planning to use this newer heavy grade flex duct. HVAC guy is calling this green duct and I want to get the manufacturer name from him, tonight, hopefully if he does have time to look at my new screen wall.

Marc

guitardad72 · Post by **guitardad72** » Thu Apr 12, 2007 3:07 am

AND one more thought/concern.

What about when the air handler is off. It would only turn the fan on when the thermostat in house calls for (conditioned) air, unless I set the fan to on while I am in the room but that would only be at 50% (I guess). Plus it's a variable speed air handler (12 speeds). Starts slow to move warm air out of ducts (in attic) then kicks in full (self adjusting for static pressure I believe). Once the thermostat has reached it's temperature it stops conditioning the air but the fan then goes back to a slow speed to move extra conditioned air out of the ducts into house. That is what really sold me on this HVAC system when I bought it 4 years ago.

When the fresh air fan is on pumping air into the studio room and air handler fan is OFF there would be nothing to hold this air back from going the other way back into the supply ducts of the house UNLESS I install a automatic back draft damper on the conditioned air duct right before the Y where fresh and conditioned air get mixed.

Could feed the fresh air ducts straight to room via there own registers BUT that does not seem like a good idea. More holes in the walls, more silencers and the two air supplies would not mix pre entering the room.

hmmm

Marc

rod gervais · Post by **rod gervais** » Thu Apr 12, 2007 4:34 am

guitardad72 wrote: Think I am going to install a manual controlled balancing damper with in easy reach of my attic access.

Marc,

NO NO NO NO NO......... with emphasis on the "NO"......... you do not want to be messing with the balancing once it's done- the right way to do this is with a pair of motorized dampers - placed on the main side of the fresh air in and outlets - wire those to a cooling thermostat - when your space is satisfied - the thermostat will close down the dampers - and then open again when you need more cooliing. Meanwhile - your fresh air fan can be running and providing you with fresh air.......... it will still work (and not effect your system) because once the rooms pressurizes - the barometrric damper will still open. The only other thing I would consider would be an humidistat that also tied into the motorized dampers - that could open them to say 50% if the humidity started getting high in the room - at least that would allow your fan coil the chance to dehumidify the air while not freezing you out........

Shouldn't I be asking him for a guess number of what cfm should be going to my room of 130 sqft/ less then 1,000 cubic feet, all based on our local temperatures, insulation of room, my air handler, etc... OR does this sound like a number I truly won't be able to measure till it's all installed? Maybe I'm over-thinking this but I will ask him tonight, I have to show off my new screen wall.

Dayam, when you read the book you never really paid attention to the section on HVAC......... you should be asking him for a hard calculated number based on gear (sensible load) ..... people in the room (latent load) fresh air (sensible and latent loads) and lighting (sensible load)

I just finished designing a smallish semi-pro studio in NC - and the HVAC was a part of my contract........ the control room required 3 tons of cooling....

That was all because of gear........ his control room gets 60% of that - and he has a seperate equipment room (w/ computers and a lot of rack gear) that gets the balance...... but that's still 1.8 tons in his main room- and roughly 480 cfm of air........ all of which I keep below 100 feet per minute of flow - with 6 supply registers with 2 large returns.

look at the calc sheet.........

Question: HVAC guy said just curving the duct around would be enough to stop sound from passing through ducts. Does it have to be 2- 90 degree turns OR can the duct curve around a min of 180 degrees. I'm planning to use this newer heavy grade flex duct. HVAC guy is calling this green duct and I want to get the manufacturer name from him, tonight, hopefully if he does have time to look at my new screen wall.

I am not overly concerned about fan noise traveling through the duct - AIR FLOW is a different issue........ 100 cfm in a 7" round duct is about 380 feet per minute of velocity - and with flex duct it's noiser than with hard round lined......

I like to see numbers not exceed 100 fpm.......... I don't have a real good feel about this............

I take it that he doesn't want to mess around with a custom built silencer box?

Only one concern is fan noise - the other is that you have this hole cut through your iso assembly - what if a plane flies over head - or there are screaming kids around - or some kid playing his boom box?

The iso chamber helps to keep that noise out as well....... that's why it needs to be installed so it becomes a piece of the ceiling or wall that is being penetrated.

I hope this helped.

Sincerely,

Rod

guitardad72 · Post by **guitardad72** » Fri Apr 13, 2007 2:31 pm

I'm in a stretch of gigs again over the weekend and have a few "must do" tasks to take care of... April 15 (US tax deadline) is right around the corner. Studio work and planning is on hold for a bit even though the HVAC is warping my brain (even though Rod has implied it's simple), I really want to get the plan/diagram done. Still need to talk to my neighbor/HVAC guy.

I was saying to my wife last night (who is wonderful for just listening to me rant for over a year now about my room) about the HVAC: I thought/could do this..., Sharward is doing..., others on forum are doing..., our HVAC neighbor says..., and Rod says...

Her reply was simple "do whatever Rod says"

Marc

Post by **sharward** » Fri Apr 13, 2007 2:53 pm

I agree!

johnz · Post by **johnz** » Sat Apr 14, 2007 12:41 am

taxes aren't due till april 17th this year, hope that's a relief. (i have yet to finish up my returns as well)

guitardad72 · Post by **guitardad72** » Mon Apr 16, 2007 3:35 am

taxes aren't due till April 17th this year, hope that's a relief. (i have yet to finish up my returns as well)

Yeah 17th but...

My desktop is doing major crashing, all my tax stuff is on there (and a huge pile of archived audio and video work) and I as of 2 days ago I can't trust it to stay on long enough to do any work....complete crash with no warning 5 times in 24 hours... It's a hard drive failure , computer has been warning me, it's just getting worse.

So my relief...
Desktop is 5 or more years old and I'm buying a new one

.
File an extension on taxes and send in a "good faith" payment to IRS.

It's not a relief trying to decide how much money I want to spend on how powerful of a computer for what end use... new computer could be for studio and/or office needs.. URH I plan to re-use the crashing computer with another hard drive.

Oh well

Marc

guitardad72 · Post by **guitardad72** » Wed Apr 18, 2007 4:29 am

Just had an inspection for drywall.

I passed and then asked inspector (who was the same one from my last inspection) "What else do I need to do to get a final for my storage room?" He said "Do you want one now?"

I got a final inspection for my storage room!!!!!!

So now I can really get to work.

What I am really, really, really happy about is that I did not have to put drywall mud over the screws on the drywall I just put up. Meaning I can now easily take down the drywall on the short wall (as planned) and even reuse that drywall. I can also, if needed easily take down some of the drywall on the ceiling so that I can have an easier time installing air ducts.

Also, I bought a new desktop computer HP Pavilion Media Center TV PC (M8000N) with Vista on it. It smokes... but I am weary of what software I have that worked perfect on XP will work on Vista. I really do not think I'll being using this Vista computer in the studio (Pro-tools is not yet Vista compliant), this will be my office, game and bash around computer.

It sure is nice to have a super fast desktop that does not crash.