John Sayers' Design Forum

John Sayers' Recording Studio Design Forum

A World of Experience
Click Here for Information on John's Services
It is currently Sat Oct 20, 2018 6:59 am

All times are UTC + 10 hours




Post new topic Reply to topic  [ 47 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
PostPosted: Tue Jul 25, 2017 10:05 pm 
Offline

Joined: Mon Jan 05, 2015 11:47 am
Posts: 60
Location: Apollo Bay, Australia
Soundman2020 wrote:
For single-room studios I usually use a mini-split plus a duct system for the fresh air inlet/stale air exhaust (with the Ururu unit in a small room you only need exhaust), but for larger facilities with three or more rooms I tend to go with a central AHU plus plenums, ducting, variable dampers and a system controller. The two-room studio can go either way.

But regardless of whether you decide to go split or AHU, you still need the ducting and silencer boxes. You can't avoid that.

- Stuart -

Hi Stuart. Is the Ururu Sarara split system still an option you'd recommend for single room studios? It seems to have some good features and sounds like it can provide a good amount of fresh air. Daikin says it can fill a 26m2 room in 2 hours. If we assume a ceiling height of just 2.4m, that equates to almost 9 litres of fresh air per second.

On the downside, the indoor unit which can run at between 42db to just 19db depending on fan speed, still might not be as quiet as a well designed ventilation system with appropriately balanced airflow rates, duct sizes and silencer boxes. Is this a fair assumption?

Thanks Stuart.


Report this post
Top
 Profile  
 
PostPosted: Wed Jul 26, 2017 1:16 am 
Offline
Site Admin
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11264
Location: Santiago, Chile
Quote:
says it can fill a 26m2 room in 2 hours.
ASHRAE recommendations call for 5 to 10 room air changes PER HOUR! In other words, all of the air in a room should be replaced every six to twelve minutes, not every two hours... A good rule of thumb for a studio is 6 changes per hour, or one every ten minutes. So in a 26m2 room that is 2.5m high, the volume is 65 m3, so the flow rate for 6 changes per hour would be 65 x 6 = 390 cubic meters per hour, or about 7 cubic meters per minute. In imperial units, that's roughly 230 CFM.

Here's some interesting reading on the subject:

http://www.contractingbusiness.com/serv ... e-room-cfm

http://www.engineeringtoolbox.com/air-c ... d_867.html

http://www.engineeringtoolbox.com/venti ... d_115.html

http://isites.harvard.edu/fs/docs/icb.t ... 1_2004.pdf


The unit itself is probably fine, and should work well as an air conditioner, but the fresh air supply does not meet building code requirements, from what I can see. It's probably fine for supplementing the flow in a typical bedroom, office, shop, etc., but those are not sealed airtight, like studios must be. There's plenty of natural air infiltration in ordinary construction that does not happen in studios.


Quote:
On the downside, the indoor unit which can run at between 42db to just 19db depending on fan speed, still might not be as quiet as a well designed ventilation system with appropriately balanced airflow rates, duct sizes and silencer boxes. Is this a fair assumption?
:thu:

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Wed Jul 26, 2017 9:52 am 
Offline

Joined: Mon Jan 05, 2015 11:47 am
Posts: 60
Location: Apollo Bay, Australia
Hi Stuart.

Oh dear. It seems I'm having another ventilation brain spasm. Ouch. I'm just ... not ... getting ... this.

You mentioned that all the air in the room should be replaced every 6-12 minutes, but in this other thread (http://johnlsayers.com/phpBB2/viewtopic ... 86#p141934) it sounds like you are saying that the air does not need to be replaced, just recirculated, while adding in a fresh air component.

Do the words 'replaced' and 'recirculated' have the same meaning in this context?

The Urura Sarara has an airflow rate of roughly 200 litres per second (presumably that's recirculated air from within the room), but can also bring in 9 litres per second of fresh air. Does that not tick all the boxes for air circulation and the fresh air component?

EDIT: I've re-read some of your other posts about ventilation and some other online articles and I think I've answered my own question. I think I'm just getting caught up on the word "replaced" which I wrongly interpret as meaning "all the air in the room needs to be replaced with fresh air". My understanding now - and correct me if I'm wrong - is that all the air in the room does need to be replaced multiple times per hour, but this is achieved primarily through re-circulation. Some fresh air does need to be added in to that mixture though, and an equal portion of air evacuated completely.

I also concluded that the Ururu Sarara (now called the US7) might be effective for a control room with a limited number of sedentary occupants, but would fall short in a room filled with sweaty musicians bashing it out.

Here endeth the brain spasm.


Report this post
Top
 Profile  
 
PostPosted: Tue Aug 29, 2017 7:34 pm 
Offline

Joined: Sat Feb 16, 2013 9:14 pm
Posts: 78
Location: Queensland, Australia
Hi Stuart

I'm trying to ascertain the fresh air volume for our studio. I have found out that an average human breathes in about 1/2 cubic metre of air an hour.

If I use the example of say 10 adults in the studio(that would be fun) as a maximum that would roughly work out to be 5 cubic metres of fresh air required every hour. Does this sound right?

We are setting up a ducted system in our live room and control room. One unit feeding both rooms with dampers, silencer boxes etc.


I hear that the HAVC contractors just add a small duct from the outside then attach to the main unit in the ceiling to bring fresh air into the circuit.

Do I let them know that that we need a minimum of 5 cubic metres of fresh air for our system?


Report this post
Top
 Profile  
 
PostPosted: Fri Sep 01, 2017 1:47 am 
Offline
Site Admin
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11264
Location: Santiago, Chile
There's two concepts here, Anthony, that often get confused and muddle together. One is the total flow rate of the system: how muc hair you need to move through the room every hour, to ensure even mixing, good temperature distribution, proper humidity control, good control of stale air, etc. The other is how much FRESH air you need to add to that, to keep people alive, and even more important, how much STALE air you need to remove in order to keep people alive.

On that second point: Many people assume that the reason for bringing in fresh air is to provide enough oxygen: that's partly true, but it's not the real reason. The REAL reason is that you need to get rid of the CO2! You exhale a large volume of CO2 with every breath, and it builds up fast in a sealed room. Since the concentration of CO2 in air is very small (about 0.04%), you don't need to add a lot before the concentration gets up high. On the other hand, the concentration of oxygen is about 21%, so even if you use up a LOT of oxygen as you breath, there's still plenty there. You will die from CO2 poisoning long before you die from oxygen starvation, and CO2 rises very fast in sealed spaces, much faster than oxygen decreases. And you pass out from CO2 poisoning long before you pass out from lack of oxygen. And way before that, at much lower Co2 concentrations, you start to feel bad, suffer headaches, nausea, vision problems, attention problems, ... way before your body even notices the slightly lower level of oxygen. You can die in a room that has plenty of oxygen available, if the CO2 is high enough. You can live with only 15% oxygen in the room (6% points down from normal), but 6.04% CO2 (6% points up from normal) is not something you want to have in your room, if you plan to live.... :shock: ....

So firstly, you need to REMOVE enough CO2 (stale air) to keep people alive, and in order to do that, you need to provide enough fresh air to replace the stale air that you removed.

And that's the reason why you also want to move a much larger volume of air around the room, and through the room: to ensure that the fresh air comes on and mixes with the room air, so that the concentration of both CO2 and oxygen stays about the same THROUGHOUT the room. Consider this: If you sit still in one place and there is no air movement at all in the room, then you create a "bubble" of atmosphere around you that is high in CO2, low in oxygen, high in humidity, high in temperature, etc... while over in the corner of the room, it is cooler, dryer, and with a property balanced mix of CO2 and O2.

So, firstly you need to ensure that you are bringing in enough air and removing enough stale air to keep everyone alive and comfortable. That's what you are talking about. Also sometimes called "make-up" air in HVAC terminology. Yes, you need ducts in your HVAC system to do this. First, a duct that dumps some of the room air overboard, into the outside world, and ANOTHER duct that brings in the same amount of fresh air from the outside world.

That's the first part. That is based on occupancy: how many people there will be inside the room.

Then thees the SECOND part, which is just recirculating air through the room to ensure good mixing, so that temperature, humidity, CO2, and O2 are pretty much contant throughout the room, with no "pockets" of hot, humid, "bad" air, nor of cold, dry, "good" air. The general rule here is that you need to replace the entire volume of air in the room, every ten minutes or so. In other words "6 room changes per hour". Some people recommend more than that, such as 8 room changes per hour (roughly one every 8 minutes), or even ten per hour (once every six minutes). But for a typical studio, 6 per hour is about right. And certainly no less than that (for example, 4 per hour would not be enough).

Therefore, you need to calculate the TOTAL air volume in ALL of your rooms, multiply that by 6, and that's how much air your AHU must be able to move, under normal circumstances, on average. That's NOT the maximum amount when it is running full bore! It's the normal amount when running normally. You also need some "headroom" in the system, for dealing with difficult days....

So when you dimension your HVAC system, your AHU must be able to move enough air to replace the entire volume in all of your rooms, 6 times per hour.

That is your flow rate.

Then IN ADDITION to that, you need to have your "make-up" air ducts, that bring in a much smaller volume of fresh air, mix it with the recirculating air, and also take some of the recirculating air and dump it overboard. That might or might not need an additional fan to drive the make-up air, and you might or might not decide to add an HRV to the make-up air system, to recover some of the energy that would otherwise be lost from dumping the stale air.

Then, when you have figured out all of that, only now can you start dimensioning the ducts that fo to your rooms, and the size of your silencer boxes and registers. Because only at this point, after you have done all the above math, only now do you know how much air is flowing through it! You cannot decide on duct sizes or silencer boxes BEFORE this point, because there's nothing to base it on!

So, you know how much your air flow rate is (cubic meters per hour) through the AHU, ducting and silencers: and you also know the maxim air flow velocity (about 1.5 meters per second), so now you can do the math to figure out what the duct size must be to get THAT speed at THAT flow rate. The speed cannot be higher, or it will create noise just due to the movement of air. So that's your limiting factor here. The speed can be lower if you want, and that's great.

So, with that info in hand you can now calculate what size ducts you need, and what size registers you need, and therefore what the interior dimensions of your silencer boxes need to be, since the air flow speed must suddenly drop by at least half at the entrance, and double at the exit (at least).

So now, with all THAT in hand, you can finally calculate the last piece of the puzzle: what your static pressure will be, for the duct, silencer, and register system that you have designed. Then you need to check that calculated static pressure against the specs of the AHU units you are considering, and find one that can handle that much static pressure. If none of the ones you are considering are able to handle that pressure, then either you need to look for a larger AHU and run it on a lower setting, or you need to modify your duct/silencer/register system to decrease the static pressure such that it is within the range of the AHU. You CANNOT run an AHU into a system where the static pressure is too high: that will cause the fan blades to stall, or at least work outside of their design range, thus causing the fan motor to work much harder than it needs to, but it still won't be able to move the correct volume of air at the correct speed, the fan will overheat, the life span will be shortened, the fan will fail, and apart from that, even while the fan is working, the rooms will not be cooled or dehumidified properly, and you won't be supplying enough air, either in re-circulation of in make-up.

So there's a lot to take into account here. Normally when I design a studio, I spend as much time on the HVAC system as I do on all of the rest! It's a big deal, and getting it wrong is an even bigger deal...

Quote:
We are setting up a ducted system in our live room and control room. One unit feeding both rooms with dampers, silencer boxes etc.
Fine, but are you going to adjust those manually, or are you going to have a system controller with sensors to do that for you automatically? If you opt for a manual system, you will have to be adjusting the dampers, flow rates, flow speeds, and temperatures constantly, yourself.

Quote:
I hear that the HAVC contractors just add a small duct from the outside then attach to the main unit in the ceiling to bring fresh air into the circuit.
Right, and the also add a similar sized duct (generally a bit larger) to exhaust the stale air from the system. And BOTH of those ducts must be sized correctly to provide the correct flow rates without increasing the static pressure too much.

Quote:
Do I let them know that that we need a minimum of 5 cubic metres of fresh air for our system?
No. Either you find an HVAC contractor who already understands studios and has done several, successfully, and provides references for you to go check, or you find someone to design the system correctly for you, and hand over that design to the contractors, with the instruction: "build it like that". If your contractors have no experience in doing HVAC systems for studios, then they won't understand the need for low velocity, high volume, low noise, silencer boxes, insertion loss, etc. They'll do it like a normal house, office, shopping center, church, school, etc, and it will be too noisy to be useful, and won't control the humidity and temperature correctly. There's a lot of reasons why that is, but too many to go into. HVAC is a much, much bigger issue than most studio builders realize, and much more different for studios than most contractors realize... unless they have done it before, successfully.

First rule of thumb: don't let an inexperienced contractor with no studio experience design your system!

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Mon Sep 04, 2017 12:23 am 
Offline

Joined: Sat Feb 16, 2013 9:14 pm
Posts: 78
Location: Queensland, Australia
Thanks for the great explanation. It makes so much sense now. I'm sure this will help a lot of people.

Good question about the control dampers, I will have to ask our contractor.

Do you design studio HAVC systems for clients so they can hand to their contractors?


Report this post
Top
 Profile  
 
PostPosted: Mon Sep 04, 2017 12:40 pm 
Offline
Site Admin
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11264
Location: Santiago, Chile
Quote:
Thanks for the great explanation. It makes so much sense now. I'm sure this will help a lot of people.
:thu:

I'll PM you about the rest.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Wed Sep 20, 2017 6:56 pm 
Offline

Joined: Sat Feb 16, 2013 9:14 pm
Posts: 78
Location: Queensland, Australia
Hi Stuart

Using the great information you gave us below I was able to calculate the duct diameter we need for our studio.

Our Control Room has a volume of 72 cubic meters and the live room is 36 cubic meters.

So....

6 room changes per hour (6 x 108 m3 = 648 m3/per hour) divided by 60 = 10.8 m3/min

- Control room 2 x supply air ducts 250mm diameter
- Control room 2 x return air ducts 250mm diameter

- Live room 1 x supply air duct 250mm diameter
- Live room 1 x return air duct 250mm diameter

We calculated that for 6 air changes per hour for both rooms we need 10.8 m3/min

Based on a Max air velocity of 1.5 meters/sec as suggested we calculated the following...


A 250mm diameter duct @ 1.5 meters/sec = 4.4 m3/min air volume.

So - 3 x 250mm supply ducts(two for control room and one for the live room) will push through 13.2 m3/min @ 1.5 meters/sec air flow velocity as a maximum.


Our total NORMAL studio requirement (CR & LR) is 10.8 m3/min So this means we have about 22% more flow capacity to reach our Max air velocity of 1.5 meters/sec as suggested.

What do you think?


If this is correct................then the silencer boxes would be as follows.

Lets say that the 250mm diameter duct calculated to make a square is 220mm x 220mm.

If I say at least make it twice the cross sectional area that would mean that the internal size of the silencer box would be 380mm x 380mm!
That is quite large for an internal cross sectional area but if it has to be then I guess it will have to be.

It will make the boxes very large and I will have to make 6 of them. 3 for the supply air and three for the return air.

:shock:


Report this post
Top
 Profile  
 
PostPosted: Mon Oct 09, 2017 10:53 pm 
Offline

Joined: Mon Oct 09, 2017 10:45 pm
Posts: 3
Location: La Jolla
Quote:
I hear that the HAVC contractors just add a small duct from the outside then attach to the main unit in the ceiling to bring fresh air into the circuit.



It is right that to add a duct. I wait for your fresh air into the circuit.
Thanks


Report this post
Top
 Profile  
 
PostPosted: Tue Oct 10, 2017 10:31 pm 
Offline

Joined: Mon Oct 09, 2017 10:45 pm
Posts: 3
Location: La Jolla
The Humidity controlling air conditioner and fresh air supplier are very very good thing that can use every person for his/her personal purpose.


Report this post
Top
 Profile  
 
PostPosted: Wed Oct 11, 2017 1:52 am 
Offline
Site Admin
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11264
Location: Santiago, Chile
Thanks for adding a location to your profile, "kabinsons1", but I'm surprised that there is a city called "La Jolla, California", located in south east India, close to Bangladesh!

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Wed Oct 11, 2017 11:27 pm 
Offline

Joined: Mon Oct 09, 2017 10:45 pm
Posts: 3
Location: La Jolla
How can control my humidity with an air conditioner?


Report this post
Top
 Profile  
 
PostPosted: Wed Oct 11, 2017 11:52 pm 
Offline
Site Admin
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11264
Location: Santiago, Chile
kabinsons1 wrote:
How can control my humidity with an air conditioner?
Simple: Turn it on.

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Wed May 16, 2018 3:12 am 
Offline

Joined: Tue May 15, 2018 2:14 am
Posts: 12
That looks great! I'm impressed. Is it very noisy? I'm not interested in something that will take away from my studio.


Report this post
Top
 Profile  
 
PostPosted: Wed Sep 26, 2018 10:25 am 
Offline

Joined: Tue Sep 05, 2017 8:30 am
Posts: 2
Location: Santa Cruz, CA
Hello folks,

This is my first post, and I am hoping for a simple reality check from experienced folks related to ventilation and AC in my under construction home studio.

For the last year, I've been building a small drum room in an existing structure in my backyard. Interior dimensions are roughly 8' x 10' with 7' ceilings. We framed a room within a room within the original framing, 2 leaf design, interior and exterior walls both have a layer of Auralex sheet-block wedged between their respective layers of sheet rock or siding, with 2 isolated doors, no windows. It is a stand-alone structure on a concrete slab. Knowing what I now know from reading here I would have done alot of things differently, but such is life, the money is spent and my needs are modest. I don't plan on doing any serious recording in the room, it is primarily a jam room for myself and possibly a few friends that I can play in during the evening without disturbing my suburban neighbors.

I am currently looking to add some ventilation to the room, despite any acoustic or isolation problems the room will have, it is effectively air-tight. This thread keeps coming up every time I google for solutions which is why I am posting here. Having learned from my mistakes, I am looking to have a mini-split AC system installed by a local reputable HVAC shop. So far the most concrete recommendation I have received is for a 9000 btu Fujistsu mini-split system. I am in central California so temperature and humidity are mild, but I know it will get hot in there. The part that I am confused on is 2 different "professionals" have told me that the mini-split should be sufficient to bring in new air from the outside and remove old air. This doesn't seem to jive with everything I have read here regarding the need for additional ventilation and ducts to move air/humidity into and out of the structure. I know extremely little about the subject, so am torn on trusting these experts.

Can someone here let me know if I am off base on this?

Thanks for your time.


Report this post
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 47 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC + 10 hours


Who is online

Users browsing this forum: Baidu [Spider] and 15 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group