HVAC for control room & booth

[thesystem]

Hi guys,

I'm currently building my new mix room and recording booth, but I'm struggling to find the right/best solution for the HVAC. So far I've been in contact with several manufacturers (Mitsubishi/Daikin/Fujitsu), HVAC installers and have been reading on this forum to get more information, but I still have a lot of questions.. I hope you guys are able to guide me in the right direction

First things first, here's a floor plan with all the dimensions (in meters):

floor plan.jpg

The oval shape you see inside the control room is an elevated ceiling. We're considering building a small window in there to let some daylight in the room. For now it's temporarily closed off with wood and beams. Also, the small grey beams you see below the oval will be removed later on. This is an older picture.

ceiling.jpg

The specifics:

Most of the time I'll be working and mixing on my own in the control room. The booth won't be used.
When I am recording (vocals/guitars etc.) I'll use the booth as well. I predict I will have a maximum of 5 people in the control room for listening to mixes, but most of the time it will be less than that.

As suggested by Soundman2020 I've calculated several things:

The volume of the control room is 81,7 m3
The volume of the booth is 31,8 m3

Assuming I want 8 circulations per hour, the total flow rate of the control room is 653 m3/hr or 10,9 m3/min
The total flow rate of the booth is 254 m3/hr or 4,2 m3/min
Combining both rooms the total flow rate is 907 m3/hr or 15,1 m3/min

If I understand correctly, between 20% and 35% of the total volume needs to be removed from the room and be replaced with fresh air from the outside. This means that I need a system that is able to circulate 907 m3 of air every hour and a system that can exhaust and add 20-35% of fresh air (around 181-317 m3) to the room. Correct?

I also need humidity control, especially since I wear contact lenses and dry air puts a strain on the eyes.
The thing is, there doesn't seem to be a HVAC solution that can do heating/cooling, fresh air and humidity all-in-one.

One solution would be to use the Daikin Ururu Sarara split-system (https://bit.ly/2XclXOx). It's currently the most quiet unit on the market, but as I understand it, the air intake is way too small plus you would still need to create an exhaust to take the 'old' air out.

If I do go this route, what sort of unit do I need in addition to the Daikin that can take care of the fresh air intake/exhaust? An HRV? Something else? How would this work in combination with the Ururu Sarara?

Another solution would be using a ducted system such as the Daikin FBA-A: https://bit.ly/2UfsyFQ. Here's the technical data sheet: https://bit.ly/2IqOrzE
The FBA-60 model can do cooling and heating at 15 m3/min on a medium setting which would be sufficient for my studio I suppose. It's also able to add fresh air (although I can't find how much). Another positive is that I can use this unit for both rooms. If I go the Ururu Sarara route I would need to buy 2 units, which is pricey.. I can't seem to find if I can use this unit for taking out the circulated air though. Does it or do I still need a second unit like an HRV?
The downside to the FBA-A is that it doesn't do humidity control. I could however add a humidifier to the system, such as this HomEvap Humidifier: https://bit.ly/2VGzu0i. Am I correct in assuming this is a possibility and will this work?

If we go with the ducted system the next challenge is to find the best place to install the satellite unit. I think there are 2 options: Either we suspend it on the ceiling in the storage room or in the dance rehearsal space (see floor plan). The thing that worries me though is that we'd have to make large holes in the walls to get to the studio. This will create a massive sound leak.. The storage room would be the most quiet place though.
Another idea is to go through the roof and come back in through the dome in the control room. The conditioned air could come in from the front of the dome (right side on the floor plan) and go out in the back. Will that work or is it better to have the registers further apart (more to the right and to the left) in order to cover the room better?

Speaking of registers, I tried to calculate the register and duct sizes I need for both rooms. Please tell me if this is correct:

control room duct and register cross-section -> 653 m3/hr is 384 CFM. Divided by 300 FPM = 1,28 ft2. Converted to cm2 = 1200 cm2. That's about 40cm in diameter for the duct/register
booth duct and register cross-section -> 254 m3/hr is 149 CFM. Divided by 300 FPM = 0,49 ft2. Converted to cm2 = 455 cm2. That's about 24cm in diameter for the duct/register

Correct?

Before I go any further I hope I can get some advise on the matter and get some guidance in choosing the right path forward. Split-system with Ururu Sarara or ducted system? Considering the space and possibilities I have, is it worth going the ducted route/will it be more quiet compared to the split-system? Or is it too complicated to build (that's what one HVAC installer told me..). Also, will I need an HRV or can the FBA-A with the HomEvap humidifier fulfill all my needs?

Thanks in advance!

[Gregwor]

I unfortunately do not have the time to check your calculations right now but I will comment on this:

The thing that worries me though is that we'd have to make large holes in the walls to get to the studio. This will create a massive sound leak.

It will not be a "massive sound leak" because you will have massive silencer boxes with sleeves making ANY penetrations through any of your walls.

I feel that your decision to go ductless or ducted falls upon how much space you have to work with and whether or not you want something hanging off of your wall heating/cooling your rooms.

If you have a lot of space for all of the duct work, MASSIVE silencer boxes, and don't want a big white thing hanging off of your wall, go ducted. If you are very tight on space and don't mind having a white thing hanging off your wall, go ductless.

Greg

[thesystem]

Hi guys, I've been busy trying to figure out the best way to tackle this thing. At this point I've decided to go with a split-system (Daikin Ururu Sarara) for heating/cooling/humidity and an HRV for fresh air (Brink Flair 300). For now I am focusing on getting the HRV right by making calculations and reading threads like this one: http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21895. They are very helpful, but I'm still a bit lost on the finer details. I hope anyone can chip in and help me out

So far this is what I've come up with:

- control room volume is 81,7 m3 x 8 circulations per hour = 653 m3/h total flow rate
- booth volume is 31,8 m3 x 8 circulations per hour = 254 m3/h total flow rate

For the HRV I only need to refresh a maximum of 35% of the total flow rate, so:
- 35% of 653 = 228 m3/h for the control room
- 35% of 254 = 89 m3/h for the booth

This means I need an HRV with a max capacity of 317 m3/h. I've found that the Brink Flair 300 is a relatively silent HRV and it delivers 300 m3/h. I guess that should be more than enough since 8 circulations per hour and 35% fresh air rate is on the high side. Please correct me if I'm wrong.
Here's a tech sheet (it's in Dutch, but most values will make sense without understanding the language):

Brink Flair technical sheet.png

I need a maximum air flow velocity of 1,5 m/s (300 FPM) at the registers. I read somewhere that 1 m/s (200 FPM) would be even beter, don't know if this is true? To be on the safe side I calculated the register sizes by choosing middle ground (1,25 m/s or 250 FPM):

- CR: A flow rate of 228 m3/h with a flow velocity of 1,25 m3/h results in a register with a surface area of 498,7 cm2 (diameter of 25,5 cm)
- Booth: A flow rate of 89 m3/h with a flow velocity of 1,25 m3/h results in a register with a surface area of 194,7 cm2 (diameter of 15,7 cm)

So far so good?

Speaking of registers, are these appropriate to use? They come in different sizes, are made of steel, have fixed vanes and can be mounted with screws:

Register.png

The open area is around 70%. In the specs sheet they only mention it can be used for air return. Could this also work for air supply or do I need something else?

Because this register has an open area of 70% I need to add this to the calculation:

- 498,7 cm2/70% = 712,4 cm2 -> using a 30x25cm would suffice
- 194,7 cm2/70% = 278,1 cm2 -> using a 20x15cm would suffice

Am I still on the right track here?

Now that I know my register sizes I should look at the ducting and silencers. The connection for the ducting on the HRV has a diameter of 16 cm (201 cm2 in surface area). This means that on the side of the HRV I have 201cm2 in surface area and on the other side I have 712,4cm2 for the control room and 278,1cm2 for the booth.

I have 2 questions about this:

1. Do you think 1 register for the control room is going the be enough or do I need 2x supply and 2x return ducts/registers? And why? I think 1 register for supply and 1 for the return air in the booth should definitely be enough, but I'm not sure about the control room. One HVAC contractor I talked to was suggesting at least 2 for example. But then how does that work with the surface area of the register? Do I just divide it by 2? So I have 2 registers of 356,2cm2 for the CR?
2. I need to split the supply and return air ducts to get to both rooms (I even need to split it 3 times if I need 2 registers in the CR). How do I make sure I get 89 m3/h to the booth and 228 m3/h to the CR? And not for example 150 to one room and 150 to the other? There's only one output on the HRV so it all comes from one duct. I don't really understand how that would work.


To create an impedance mismatch I should at least double the cross sectional area right? Preferably more. So with the numbers I calculated above, is this the right way to go?

HRV -> Decflex Sonodec* ducting (201cm2) -> silencer entry point (700cm2, factor of 3,5) -> silencer exit point (1400cm2, factor of 2) -> register (712cm2)

* (as suggested by Philip Newell in his Recording Studio Design Book)

Questions:

- how long should the ducting be before I go into the silencer?
- can you do both sudden cross sectional area changes in one silencer as I did here?
- is the register directly connected to the exit of the silencer or should you add extra ducting between this?
- at the exit of the silencer the cross sectional area is 1400cm2, but the register is twice as small. Won't this create turbulence and/or noise?

Please let me know if I'm on the right track and if my calculations and deductions are correct

[thesystem]

Anyone? Am I way off here? Did I forget something or are the questions unclear? Please let me know so I can adjust it. Would really like some help on the matter

[Gregwor]

Speaking of registers, are these appropriate to use?

Yes.

Could this also work for air supply or do I need something else?

Yes this will work fine as long as it is directing air in the places you want it to go!

1. Do you think 1 register for the control room is going the be enough or do I need 2x supply and 2x return ducts/registers? And why? I think 1 register for supply and 1 for the return air in the booth should definitely be enough, but I'm not sure about the control room. One HVAC contractor I talked to was suggesting at least 2 for example. But then how does that work with the surface area of the register? Do I just divide it by 2? So I have 2 registers of 356,2cm2 for the CR?

If you can fit two, that just means you have twice the cross sectional area and this is a good thing. Lower air velocity, more impedance mismatch, more insertion loss!
If you have 2 registers, you are doubling the cross sectional area, not halving it.

2. I need to split the supply and return air ducts to get to both rooms (I even need to split it 3 times if I need 2 registers in the CR). How do I make sure I get 89 m3/h to the booth and 228 m3/h to the CR? And not for example 150 to one room and 150 to the other? There's only one output on the HRV so it all comes from one duct. I don't really understand how that would work.

Control dampers and proper sizing of duct work.

To create an impedance mismatch I should at least double the cross sectional area right?

Correct.

- how long should the ducting be before I go into the silencer?

This is a toss up. The longer your duct work, the more insertion loss you have. The longer your duct work, the higher your static pressure. I wouldn't add length for fun. Duct work is expensive, especially duct lined duct.

- can you do both sudden cross sectional area changes in one silencer as I did here?

I didn't have time to read through your thread in super detail so I can't comment on how you did it with yours, but yes, you can totally have multiple cross sectional area changes in one silencer. Just realize that each time you do it, it adds static pressure.

- is the register directly connected to the exit of the silencer or should you add extra ducting between this?

As long as your silencer box sleeve has fully penetrated your leaf, you can add ducting if required.

You need a certain distance between any direction change or CSA change and the mouth of your grille/register. I've heard two values for this distance. It's either 3 or 5 times the diameter of that which is feeding the grille/register. So let's say your have a 4" round duct that goes to a required 6" round grille, you'd need a distance of between 12 and 20" of straight duct to prevent noise at the mouth.

- at the exit of the silencer the cross sectional area is 1400cm2, but the register is twice as small. Won't this create turbulence and/or noise?

This is where two registers would help. If your static pressure is okay, you could make the output of your silencer twice as small. See my last answer regarding the distance you need after any cross sectional change. OR, if you don't want two registers, get one big one!

Greg