Help with one room studio design in Delta BC, Canada

Thanks everyone again for all the info and insights. This got me thinking:

Filling your joist cavities decreases the gap in your MSM system, but for many of us, there's no other choice. I haven't done the math to see if this is feasible, but with that in mind, did you ever consider running 2 or 3 sets of your long joist cavity style silencers down each side of your room? One side being supply, the other being return. You could have your outer leaf silencers mounted on the outside of your room (like the supply silencer in your recent picture). They could have 2 or 3 sleeves on them that would connect to the inner leaf silencers (these would be the long skinny joist cavity style).

I'm wondering if I can do a combination now... running my small silencer boxes for the return on each leaf, 6 runs of them... 3 along each side of the room (6x36" cross sectional area = 216"... I know that's not the right number, but I was thinking I could get away with 5 changes per hour instead of 6, in which case this would be large enough of a cross sectional area, and a low enough velocity), and have them vent out on the east wall. I spoke with my contractor and he doesn't think the large boxes on the East Wall (the wall with my supply boxes in my previous post) will fly with the inspector due to setback requirements. Instead I could utilize the pool room next door for the supply boxes on both leaves as you suggested... bumping out my outer leaf wall to accommodate the larger boxes. This would put my supply register in the front right corner of the room, but I could duct it to the front central bottom of my baffle, and then have multiple return registers on the ceiling in the rear of the room. I feel like this works for HVAC, but I can't help but think it might not work well for preserving my isolation as I'll be taking out a lot of my spring volume in my MSM system to accommodate 12 silencer boxes. I might consider shortening the boxes to allow for more spring area of just insulation... There would still be 6 inches of spring from the insulation on the inner leaf with this design though. Also, cutting that many openings for registers in my double layers of drywall seems mental... Something like this is what I was thinking: Interested in if anyone has any thoughts on if this is indeed a bad idea. Failing that, at some point I might just have to back off of my isolation requirements as a compromise and work around noise levels at different times of the day... and resort to one silencer per opening that penetrates both leaves via a massive wooden duct. Thanks, Aaron

Three quick questions (sorry if you've answered both, but I don't have time to read through your entire thread again to find out. I skimmed it but didn't see the answer): 1. Are you doing forced air or a ductless minisplit? Can you share any HVAC calculations you've done? 2. What is the room opposite of your pool mechanical room being used for? Can you sacrifice a corner of it (up high or a side wall corner) for a silencer box? The reason I suggest this is because it would allow you to easily have supply and return on opposite sides of your room! 3. Are you doing an inside out ceiling?

Also, cutting that many openings for registers in my double layers of drywall seems mental...

With silencer boxes, it is 100% okay!

I spoke with my contractor and he doesn't think the large boxes on the East Wall (the wall with my supply boxes in my previous post) will fly with the inspector due to setback requirements.

What about putting the silencer boxes on the front side of the building? You could hide them with a nice design so no one would really be able to tell what they are. Greg

I feel like this works for HVAC, but I can't help but think it might not work well for preserving my isolation ...

Well.... Silencer box being raised into place between engineered joists... Silencer box in place (yeah, it's a tight fit, but there are air gaps all around that: no contact with the joists): View from directly below: camera is on its back on the floor, with the lens pointing up at the ceiling. The silencer box is in place, part of the inside-out ceiling is in place, and the flexduct is visible through the part where the ceiling module has not yet been put in: Completed inside-out ceiling, with the silencer box sleeve extending down through it: That's the ceiling of an iso booth, big enough to fit in a drum kit at a pinch. It gets a little more than 50 dB isolation, probably around 55. Drums are barely audible in the room upstairs. Vocals and instruments are dead silent. Hopefully that answers your doubts! :)

Also, cutting that many openings for registers in my double layers of drywall seems mental...

Drilling one single 1/2" hole through your leaf is already mental! ... if it isn't done correctly, with excellent seals and enough mass to get back to the right situation. That's why you need silencer boxes on every penetration... - Stuart -

1. Are you doing forced air or a ductless minisplit? Can you share any HVAC calculations you've done?

OK, first off Greg, thanks for asking this question... looks like somewhere along the line I got turned around and doubled my cross sectional requirements for my silencer boxes. In copying my calculations below I realized that 6 runs of these return silencer boxes is more than enough cross sectional area... In fact I only need 4 runs. Having said all that... I am planning on a fan at the supply duct just to bring in fresh air for the near term, and likely end up putting in a forced air heat pump down the line. As for calculations here's what I have up to now: - My room volume = 9'9 1/4" x 14'1 1/2" x 8'11 7/8" = roughly 1240 cf - my cubic feet per minute should = Refresh rate * Volume / 60 = 6*1240/60 = ~124 cfm - I need to try to get to sub 300fpm at the register, so I used a calculator I found on this site. It suggested I need a 9" diameter opening at the register to get to ~280 f/m air speed. - 9" diameter is 63.6 square inches. - Which means my cross sectional area of my silencers needs to be ~127 square inches - My silencer boxes in my ceiling joists for the return air have a cross sectional area of 4.5"x8" = 36" - If I run 4 of them along the joists that would give me a total of 144 square inches of cross sectional area on my return silencers. - For my supply boxes, I used your formula (width-7)/2=x. I made the depth of my boxes 15" which would give me 11" of air space. I need ~13" to get to 144 square inches, so my width=(2x)+7 = 33" wide. so my Supply boxes will be 2'9" x 15"

2. What is the room opposite of your pool mechanical room being used for? Can you sacrifice a corner of it (up high or a side wall corner) for a silencer box? The reason I suggest this is because it would allow you to easily have supply and return on opposite sides of your room!

Unfortunately not, that'll be the family TV room, and there's going to be a built in media center right across that wall. However, with my current design, I don't think I'll need to do that, as I will have the supply register vented to the front bottom of my speaker baffle wall, and have the 4 return registers in the ceiling in the rear of my room. Am I missing something?

3. Are you doing an inside out ceiling?

I wasn't planning on doing an inside out ceiling. I read that you recommended it above. I'm guessing the main benefit is the extra few inches of effective ceiling height? I am wondering if I'm better off not doing that and using the 6 inches of the inner leaf ceiling joists as spring, since I'm now eating up a lot of space for the silencer boxes.

What about putting the silencer boxes on the front side of the building? You could hide them with a nice design so no one would really be able to tell what they are.

This is a no go as far as the wife approval factor... That wall faces our pool, and she's just not having it. But unless I am missing something, I think using the pool equipment room works doesn't it? So here's an updated look at what I'm thinking. And an open look at the silencer boxes. First the inner leaf: Stuart, thanks for the reference, I added the duct from the silencer into the room on the bottom: And the outer leaf: I am unsure of how I should cut out the holes on these boxes for the ducting between them, do I just cut out a circle on the end where I would attach the flex duct (appropriate size flex duct still to be calculated...) Also, I haven't designed the supply boxes yet, as I think I have ample room to make sure that they're right. Unless, anyone tells me I've missed something, I'm thinking that this is the design that I'm going to move forward with. Interested to hear your thoughts. Thanks, Aaron

Hey Aaron, I have to ask this question again because you kind of failed to directly answer it:

Are you doing forced air or a ductless minisplit?

A few things: 1. I don't see a designated air handler in your space. 2. Due to your back wall architectural guidelines, there is no room for your returns to get back to an ducted air handler. Therefore, I'm guessing that you're using a ductless mini split? If so, you could get away with WAY less cross sectional area than you're currently calculating. This means smaller silencer boxes. Okay so, if you have 1240 cubic feet, yes 6 air changes is 124 CFM. Now, that's needed if you're rocking a ducted system. For fresh air, which your silencer boxes are passing, you only need ~ 30% of that amount. So, 124CFM x 30% = 37.2 CFM. Much less, right? You might have troubles finding an inline fan that will move only that amount of air. You might have to get crafty. Also, before I forget, I need to point out that due to your current design, you can't fit an HRV in there which as I'm sure you know would be really really smart to have in BC climate. If are aren't cool dumping all of your conditioned (heated) air out into the cold winter and then have your fan blowing really cold air in on your feet (under your speakers), you certainly should consider an HRV unit. Anyway, the smallest round duct you're going to find around your area might be 5" flex duct. Unfortunately, this crap isn't duct LINED, it's insulated. So, we have to rely on the low frequency attenuation in any flex duct runs and rely on the silencer boxes for the mid/high frequency attenuation. 5” RD duct = 19.63 sq in. Double = 39.26 sq in. That means that the inside total cross sectional area of your silencers only need to be 39.26 sq in. in order to achieve doubling of your cross sectional area. You wrote that each silencer box in your joists has a cross sectional area of 36". So you're ~91% there with a SINGLE joist cavity of boxes! Let's say you have two joist cavities of boxes. That gives you 72 sq in. Now, going from 5" inlets on the box to 72 sq in inside, you've increased your area by 3.67 times! Now THAT's an impedance mismatch. Kick ass. Also, regarding velocity: Air velocity in ft/min = CFM Flow rate in ( ft3/min) / CSA Cross sectional area in ft2 Air velocity in ft/min = 37.2 CFM / 72 sq in Air velocity in ft/min = 37.2 CFM / 0.5 ft2 Air velocity in ft/min = 74.4 feet per minute. Now THAT is slow :yahoo: Remember, you might have more CFM happening though depending on the fan or HRV unit you find to drive the system. Either way, as you can see, you're in very very good shape. With an HRV you could run it on low (as long as the CFM falls into your equations well) and if it is exchanging too much air, you could set it for 40 min per hour instead of being on steady. Or 20 min per hour even if it's just you in there and your chilling out not working hard.

I wasn't planning on doing an inside out ceiling. I read that you recommended it above. I'm guessing the main benefit is the extra few inches of effective ceiling height? I am wondering if I'm better off not doing that and using the 6 inches of the inner leaf ceiling joists as spring, since I'm now eating up a lot of space for the silencer boxes.

Do inside out. Okay, so, here are some thoughts: 1. show us where you're putting the mini split. 2. you should have your fresh air blowing in right ABOVE your indoor mini split head unit, not the floor under your speakers. 3. try to implement an HRV into your design and put it in the pool mechanical room (I have one really bizarre idea of how to get your duct work on your ceiling joist boxes into the pool room) 3b. since it's a mechanical type room, I'm guessing there's a floor drain in there you could use as a drain for your mini split yeah? 4. you're making insanely good progress here so please stay with us and as you can imagine, once this HVAC crap is behind you, you'll be off to the races! Greg

OK Greg... you got me. Just when I thought I had things under control you ask some questions that remind me how much I don't really know... :) Let me give this a try... but I think I'll have more questions then answers again...

Are you doing forced air or a ductless minisplit?

Well... I guess I would say forced air. But now I'm not sure... I have radiant floor heating built in to the concrete so my main concern was getting fresh air into the room to not kill myself, and secondary concern was A/C for the hotter months. That's why the first time I answered that I was just thinking of adding a fan at the supply of my ducting to pump the appropriate amount of fresh air into the room. Naively I was thinking that I could then down the line (maybe after the setback inspection) change the fan out with something like a heat pump to control the A/C in the hotter months and still provide the necessary fresh air. However, you then rightly pointed out that I'd be dumping cold air onto my feet in the winter with my current plan and I started looking into the heat pump/HRV systems. My understand now is that the heat pump sometimes will cut off the fresh air completely depending on the external temperature and what it's trying to do (heat or cool), so this might not actually be a viable plan. But I must admit though, that after trying to research a bit I am not confident that that statement is necessarily correct, and I think I'm more confused now than before about how all these systems work (HRV/Heat Pump/AC unit etc.) and on what I should be doing with my plan. :oops: I'm assuming that you pointed this out:

1. I don't see a designated air handler in your space. 2. Due to your back wall architectural guidelines, there is no room for your returns to get back to an ducted air handler.

Because through my research the heat pump also utilizes the air from the exhaust too, thus the need to pipe back to the air handler?

Therefore, I'm guessing that you're using a ductless mini split?

Well... I wasn't... but to be honest, now I feel like I really don't know what I am doing and a bit back at square 1... well, maybe square 2 or 3, but either way a whole lot more figuring to do.

If so, you could get away with WAY less cross sectional area than you're currently calculating. This means smaller silencer boxes. Okay so, if you have 1240 cubic feet, yes 6 air changes is 124 CFM. Now, that's needed if you're rocking a ducted system. For fresh air, which your silencer boxes are passing, you only need ~ 30% of that amount. So, 124CFM x 30% = 37.2 CFM. Much less, right? You might have troubles finding an inline fan that will move only that amount of air. You might have to get crafty. Also, before I forget, I need to point out that due to your current design, you can't fit an HRV in there which as I'm sure you know would be really really smart to have in BC climate. If are aren't cool dumping all of your conditioned (heated) air out into the cold winter and then have your fan blowing really cold air in on your feet (under your speakers), you certainly should consider an HRV unit. Anyway, the smallest round duct you're going to find around your area might be 5" flex duct. Unfortunately, this crap isn't duct LINED, it's insulated. So, we have to rely on the low frequency attenuation in any flex duct runs and rely on the silencer boxes for the mid/high frequency attenuation. 5” RD duct = 19.63 sq in. Double = 39.26 sq in. That means that the inside total cross sectional area of your silencers only need to be 39.26 sq in. in order to achieve doubling of your cross sectional area. You wrote that each silencer box in your joists has a cross sectional area of 36". So you're ~91% there with a SINGLE joist cavity of boxes! Let's say you have two joist cavities of boxes. That gives you 72 sq in. Now, going from 5" inlets on the box to 72 sq in inside, you've increased your area by 3.67 times! Now THAT's an impedance mismatch. Kick ass. Also, regarding velocity: Air velocity in ft/min = CFM Flow rate in ( ft3/min) / CSA Cross sectional area in ft2 Air velocity in ft/min = 37.2 CFM / 72 sq in Air velocity in ft/min = 37.2 CFM / 0.5 ft2 Air velocity in ft/min = 74.4 feet per minute. Now THAT is slow :yahoo:

This all sounds fantastic save for the dumping cold air on the feet part, but as I said before, I am now back to trying to figure out what system I really do need so I can figure out if this is indeed applicable to me.

1. show us where you're putting the mini split. 2. you should have your fresh air blowing in right ABOVE your indoor mini split head unit, not the floor under your speakers. 3. try to implement an HRV into your design and put it in the pool mechanical room (I have one really bizarre idea of how to get your duct work on your ceiling joist boxes into the pool room) 3b. since it's a mechanical type room, I'm guessing there's a floor drain in there you could use as a drain for your mini split yeah?

If this is the way I go I will do all of these things. But given what you know now from my requirements (no need for heat, mostly fresh air, secondarily cooling, but given my climate only in a couple months in the summer...) is this the system you would suggest? I also have a bit of tissue rejection from the actual unit that is mounted in the room for the mini-split since it's big and ugly... but if it's what I need I could get over that...

4. you're making insanely good progress here so please stay with us and as you can imagine, once this HVAC crap is behind you, you'll be off to the races!

Thanks for the positive encouragement... although it feels more like I just took a punch to the gut :lol: But sincerely, thank you for all the help, I wouldn't have gotten this far without you and Stuart... and I will press on, and hopefully this is just a small set back in my planning process. Apologies for my ignorance... Thanks, Aaron

Well... I guess I would say forced air. But now I'm not sure...

Forced air means either a heat pump that drives a coil/fan unit the size of a small furnace that then blows air through ducts of your original calculation size. It needs supply duct work FROM the fan unit and return air BACK to the unit, just like a normal furnace runs here in Western Canada. Then, you need fresh air from outside and stale air pumped outside just like our homes here have. In Western Canada, HRV's are standard in new builds and as far as I know even required here in the Edmonton area. As I described in my last post, it doesn't make sense to blow all of your heat outside only to replace it with -20 cold air. HRV's are quite efficient. So yeah, with a ducted system, you have a lot of duct work required If you go with a ductless mini split, sure you'll have a big, kind of ugly looking unit on your wall, but it will do all of your cooling and heating, taking over where your floor fails to keep your room nice and warm when you aren't in there during the brutal cold month of February. Also, it will keep the air nice and comfortable during super hot summer months when you and your friends are hanging out working on tunes in your room. The duct work I described in my last post can be nice and small and literally just replaces your stale air with nice fresh air from outside. Running it through an HRV will save you a ton on heating/cooling costs and also keep the air being brought in from outside at almost the same temperature as the air in your room! Your biggest issue may be finding a small single room HRV as most run around and above 100 CFM. I know small ones exist, but I couldn't link you to one right now. You'll also need to find out where you can put the heat pump for your mini split. Luckily, they are small and really quite quiet outdoor units.

Because through my research the heat pump also utilizes the air from the exhaust too, thus the need to pipe back to the air handler?

In a ducted system, yes. As I described above, it runs just like a regular Western Canada furnace does.

is this the system you would suggest?

For what you're doing, yes. Just make sure you get a low temperature good brand name (like Mitsubishi or at worst case, get a Fujitsu) mini split. You'll see that if you get a cheap one (even if it's a good brand), they don't operate at low temperatures like we get in our area. The low temp ones only heat EFFICIENTLY down to like -25 celcius which is probably fine for you. It's a bit colder here in Alberta. It'll still throw heat below that temperature, just not as efficiently. Plus, your in floor heating will help keep you warm in those cold times. If you ever feel the need to have your mini split throw max heat at very low temperatures, you can add on modules to the unit.

Thanks for the positive encouragement... although it feels more like I just took a punch to the gut :lol: But sincerely, thank you for all the help, I wouldn't have gotten this far without you and Stuart... and I will press on, and hopefully this is just a small set back in my planning process.

You're doing awesome man! I hope you feel confident that you're doing the right thing. Think of all of the people who just throw rooms up with zero knowledge of studio design. Your place is going to rule and you can be so proud of it. Thank you for being part of the forum!

Apologies for my ignorance...

Don't apologize! I was in your shoes not to long ago and I have to tell you, learning about this stuff is so cool. And it's so awesome to help people out answering questions that you've learned the answers to the hard way! Having said that, I truly feel the best way to learn this stuff is to read threads regularly and try to help people out. It forces you to do research on topics you don't know well and most of the time, you then learn things that directly apply to your own build. Before you know it, you can answer most of the questions without looking anything up! So please feel free to chime in and answer peoples questions on here. If we all help one another out, it makes for a better forum and better studios all over the world! Greg

Thanks again for all your help Greg. Still trying to wrap my head around this... I think the mini-split is the way to go. I am trying to figure out where the best place to put it is, I'm guessing that maybe front centre up high on my baffle wall might be a good place, because I could at least partially hide it with the cloud. I can also still pipe fresh air in just above it just like my previous plan had. I've asked my contractor if mounting the heat pump for the mini-split on the ground on that east wall is going to be a problem for setbacks, and am waiting to hear back.

The duct work I described in my last post can be nice and small and literally just replaces your stale air with nice fresh air from outside. Running it through an HRV will save you a ton on heating/cooling costs and also keep the air being brought in from outside at almost the same temperature as the air in your room!

Question for you though: 1) Do I still need to run my exhaust air back to the supply to put an HRV in line with my fresh air supply? Or does the HRV just draw air from the outside? My thinking is that if my fresh air requirements are less, then the 2 big supply silencers will get smaller and I could put the HRV in the pool equipment room. (Caveat that this is all before I've done my HRV research so I'm hoping that this is possible... going to do research now...) Thanks, Aaron

1) Do I still need to run my exhaust air back to the supply to put an HRV in line with my fresh air supply? Or does the HRV just draw air from the outside?

An HRV does what it says: it Recovers the Heat in the Ventilation air: It extracts the heat that is in one flow of air going one way, and transfers that heat to the other flow of air going the other way. So it MUST have both a supply duct AND an exhaust duct: it has the transfer he heat FROM one of those TO the other one. If you only have one stream, then there's nothing to transfer from/to. So which way does it transfer? Heat always flows from hotter to colder, so whichever stream is hotter will end up cooler, and whichever stream is cooler will get warmer. Which is very fortunate for us, because in summer, when your HVAC system is cooling the room, the cool room air that you are sending out through the exhaust will be heated up from the heat in the incoming air from outside, and that incoming air will therefore end up cooler. In effect, the HRV will seem to have transferred the "cold" from the outgoing air to the incoming air, and relatively speaking, that's true.... But in absolute terms, the heat went from the incoming hot air to the outgoing cold air. Then in winter, when your HVAC system is heating the room, it works the other way around: the outgoing hot air will have it's heat transferred to the incoming cold air, which is exactly what you want. So in both summer and winter, the heat is transferred the way you want it to be. As Greg mentioned, these units are quite efficient and can recover a very large percentage of the heat, saving you big money on heating and cooling bills. There's another type of system, called an "ERV" for "Energy Recovery Ventilator", and it does even more: it also transfers humidity, which recovers even more energy... but it's more complex, and only works in climates where there's going to be a big difference in humidity between the indoor air and outdoor air. If the humidity is similar, only differing in a few percentage points, then it won't be able to move that humidity very well.

I could put the HRV in the pool equipment room.

You can put it wherever you want, basically, provided that the ducts are suitably insulated if it is in a very hot or cold location, and/or if it is far from the room (long ducts). And here to, you have to be careful with static pressure: like any other fan, the HRV can only deal with a certain maximum static pressure, so do make sure that you design your duct system with that in mind. - Stuart -

Greg

OK. Here's what I'm thinking now. Caveat that it might not work because I am not sure that I can get the flex duct to the pool room, and that I need to go to the site to look at a few things to see if it's plausible... but here's where I am thinking. - CFM of fresh air requirement = 37.2 CFM - 2 runs of silencers on inner leaf with ~72 sq inches of cross sectional area total - Connected to 2 runs of 5" diameter flex duct (total cross sectional area of 19.6x2=39.2 square inches), that joins together to 1 run of 5" diameter flex duct (cross sectional area of 19.6 square inches) and runs 90 degrees to the pool equipment room. - That flex duct then connects to my outer leaf Silencer on the inside of the outer leaf in the pool equipment pop out outer leaf wall, with a cross sectional area of 60 sq ins for a 3x impedance mismatch. - Outer leaf then connects to HRV in the pool equipment room, which then connects back to the outer leaf silencer on the inside of the outer leaf for the supply. Same size cross section as return outer leaf silencer. - which connects to the inner leaf silencer in the same box out with the same cross sectional area. - which then is ducted to vent above a mini-split near the top of the centre of my infinite baffle. - Mini-Split goes out the east wall to the heat pump mounted on the ground. (not modeled yet in Sketch Up.) Looking like this: Things I need to figure out: - if I can find an HRV that blows as low as 37.2 CFM, and can handle the static pressure of the system. (will do some research on this one tonight.) - if I can find a path for the 5" flex duct to the pool equipment room. (dicey, but I'm going to the site now to check this out) - Contractor to confirm that I can put the mini-split heat pump on the ground and not violate the setbacks. - Have to source an economical mini-split that fits my purposes. - Need to appropriately size registers for another impedance mismatch... but should be easy to do this given the lower CFM. One question: 1) How does one do the calculations to figure out the static pressure of the system? I know I'll need to take this into account for the HRV requirements... I feel like this can work if I can figure out the ducting, but I wouldn't mind a sanity check from you Greg, or Stuart. And as always... thanks for all the help. -Aaron

- Mini-Split goes out the east wall to the heat pump mounted on the ground. (not modeled yet in Sketch Up.)

If you can't put it there, then it's probably not a problem. The system likely comes with tubing that is several meters long, and it is possible to buy extension kits to get several more meters out of that. Check the manual for the systems you are thinking of BEFORE buying to see what the limit is. In the specifications section, or the installation section, it should tell you what the maximum allowed tubing length is. Caveat: Don't buy ordinary copper water pipe and try to make your own extensions! Won't work. Buy the correct complete kit, with the connectors already attached on both ends. The type of pipe used in HVAC systems is specially meant to carry the very high pressure gasses and liquids. Normal copper pipe is no good for that. Also, you cannot solder HVAC pipes with ordinary electronic solder and a soldering iron: you need special silver solder and very high temperatures to solder HVAC pipe. In fact, it isn't really soldering at all: it is brazing. Not worth learning to do that yourself. Just buy the correct pipe kit for the length you need, then hire a qualified HVAC installer to connect it all up for you, and charge the system with gas... not something you should try to do yourself! You can probably mount the compressor and indoor unit yourself, and also cut the holes and push the pipes/wiring through, but don't try to do the connection of those pipes. Don't even take off the protective caps! Also, it's a minor but still important point but part of the "bundle" of pipes, tubes and wires that connect the indoor unit (sometimes called the "condenser") to the out door unit (usually called the "compressor" or sometimes the "heat pump"), is the condensate drain pipe. It drains away the water that will condense on the cooling coils of the indoor unit, from the humidity in the air. That pipe must always descend, never climb. It must always slope downwards, all the way from the indoor unit to wherever you want the water to go. Sometimes, that takes careful planning. What moves the water through that pipe, is just gravity. Water can't climb uphill... it always flows down. Thus, no part of the pipe must ever be higher than the bottom of the indoor unit, or the water will never run down the pipe: it will accumulate in the drip pan inside the unit, then overflow and run down your wall... So do take that into account. That condensate drain pipe is usually a flexible plastic pipe, and it does not actually need to go to the compressor: you can guide it anywhere you want to let the water drain out. So it doesn't need to follow the same path as the rest of the "bundle", and it can be as long as it needs to be to get wherever it is going... provided that it always slopes down. - Stuart -

- Connected to 2 runs of 5" diameter flex duct (total cross sectional area of 19.6x2=39.2 square inches), that joins together to 1 run of 5" diameter flex duct (cross sectional area of 19.6 square inches) and runs 90 degrees to the pool equipment room.

The only downside to this plan of attack is that it prevents you from building your ceiling inside out. What if you built inside out all the way to the front of your room at which point you left one joist traditional in order to run your duct down it as it is in your current drawing. You'd just have to rearrange your pool room silencer boxes to accommodate this configuration. You REALLY should build inside out to maximize your room volume.

- That flex duct then connects to my outer leaf Silencer on the inside of the outer leaf in the pool equipment pop out outer leaf wall, with a cross sectional area of 60 sq ins for a 3x impedance mismatch.

The penetration of your outer leaf wall going into your pool equipment room NEEDS to be the sleeve of the silencer box. You have it drawn that the flex duct penetrates the wall. But think about it, the flex duct is very thin and light and the mass of your outer leaf is not maintained. The sound can just blow right through the light plastic duct sleeve. If your 1" MDF silencer sleeve is going through the leaf instead, with caulk around it, the mass is maintained and attenuated through the silencer box so it's nice and quiet by the time it exits the silencer!

- Outer leaf then connects to HRV in the pool equipment room,

HRV's have filters in them that need to be cleaned. The Fantech model in my house has a lid that unclips so it can lift out of the way. This would work in your current design, but I'm just suggesting that you make sure whatever model you buy can be accessed in the little space you have the HRV housed in.

- if I can find a path for the 5" flex duct to the pool equipment room. (dicey, but I'm going to the site now to check this out)

There is ALWAYS a way!

- Need to appropriately size registers for another impedance mismatch... but should be easy to do this given the lower CFM.

Don't worry about impedance mismatch here. By nature it has a HUGE impedance mismatch! It's going from your small silencer cross sectional area to the entire volume of your room! What you need to worry about is air velocity and what the NC rating of your registers are. Also, regarding registers, make sure they throw the right direction. They're expensive, but check out Nailor brand stuff as they have great documentation on their products.

1) How does one do the calculations to figure out the static pressure of the system? I know I'll need to take this into account for the HRV requirements...

I posted my static pressure calculation spreadsheet on this page (7th post from the top): viewtopic.php?f=1&t=21752 It's very annoying to do.

And as always... thanks for all the help.

As always Aaron, your hard work is evident. Greg

If you can't put it there, then it's probably not a problem. The system likely comes with tubing that is several meters long, and it is possible to buy extension kits to get several more meters out of that.

Good to know, Stuart. Thanks for that, and all the detail about tubing as well!

The only downside to this plan of attack is that it prevents you from building your ceiling inside out. What if you built inside out all the way to the front of your room at which point you left one joist traditional in order to run your duct down it as it is in your current drawing. You'd just have to rearrange your pool room silencer boxes to accommodate this configuration.

OK. I'll look into this.

The penetration of your outer leaf wall going into your pool equipment room NEEDS to be the sleeve of the silencer box. You have it drawn that the flex duct penetrates the wall.

yeah, I had intended for it to be a sleeve, I just mocked up the drawing quickly to show the concept. I am working on details now... Which brings me to a couple of questions I have: 1) What's the best way to connect a rectangular sleeve to round flex duct, and still maintain a seal? 2) I'm thinking whatever the answer to number 1 is will also apply to connecting the end of my inner leaf silencer box to round flex duct as well, but in the event it doesn't, what's a good way to do that too?

HRV's have filters in them that need to be cleaned. The Fantech model in my house has a lid that unclips so it can lift out of the way. This would work in your current design, but I'm just suggesting that you make sure whatever model you buy can be accessed in the little space you have the HRV housed in.

Good call, and will do.

They're expensive, but check out Nailor brand stuff as they have great documentation on their products.

Thanks for the tip!

I posted my static pressure calculation spreadsheet on this page (7th post from the top): viewtopic.php?f=1&t=21752 It's very annoying to do.

Took a quick scan, haven't gotten into it fully yet. But again, thanks for the link! -Aaron

1) What's the best way to connect a rectangular sleeve to round flex duct, and still maintain a seal? 2) I'm thinking whatever the answer to number 1 is will also apply to connecting the end of my inner leaf silencer box to round flex duct as well, but in the event it doesn't, what's a good way to do that too?

To obtain the impedance mismatch, try to avoid smooth conical type transitions. Just fix one of these to your box (apply caulk to the bottom side of the ring before you brad nail it on), seal the hell out of it with mastic and you're good to go! Greg

Hey Guys, I have a random selection of a few more questions for you. 1) Is there any reason why an inside out ceiling wouldn't work with joists that are 16"OC? I think I read somewhere Stuart suggesting that he normally sisters the joists at 24"OC with blocking every 48". With 16"OC I'm assuming my ceiling panels would be more plentiful and long and skinny, but maybe still doable... 2) And also is there anything I should consider with respect to the inside out ceiling if I'm doing conventional walls (non-inside out)? My inner leaf ceiling joists are hung from the walls, not built on top. I'm assuming as long as the top plates of the walls are acoustically sealed where they meet the ceiling panels I would be ok, true? 3) If I can do inside out ceiling, am I right to think that I could run the electrical wiring through the joists just below my ceiling panels to my track lights to preserve the one entry into the room? This way I could cover that wiring with acoustic treatment after the fact. 4) If I do inside out, and fill the ceiling cavities with treatment, am I running the risk of making the room too dead with 2-4" worth of 703 or similar? 5) For my cloud above my listening position, I haven't yet had the chance to properly do my vertical plane ray tracing, but I believe I read Stuart somewhere recommend pulling the cloud away from the baffle wall, as the reflections right up against the baffle wall aren't going to reflect to my listening position. I imagine that it's pretty unique per room, but is there a rough guideline on how far away from the baffle the cloud could be? I'm pretty sure the answer is I need to do the calculations/Ray-Tracing, but I was thinking I might put a track light between my cloud and my baffle wall if there would be enough room, so I am just trying to understand roughly if that is going to be a bad idea or not... Sorry for the shotgun questions without much context from my side, but my electrician is on site tomorrow and I want to discuss where the lighting should be going with him... I was hoping to have had time to finish my design by now so I would know exactly where to tell him but life has gotten in the way :( . I figure if I can wrap my head around the possibilities a bit better, then I could buy myself the time to finish the design properly. Thanks again, Aaron

1) Is there any reason why an inside out ceiling wouldn't work with joists that are 16"OC? I think I read somewhere Stuart suggesting that he normally sisters the joists at 24"OC with blocking every 48". With 16"OC I'm assuming my ceiling panels would be more plentiful and long and skinny, but maybe still doable...

The larger the distance between joists the better. This is because the sheathing can then flex more. If you look at any tests done, 24 OC is better than 16 OC. Ultimately, you need to get an engineers stamp saying your ceiling design will hold the load you're putting on it. You could probably have greater OC distance using LVL studs (West Fraser is manufactured near you -- that's what I got) but 2x8's (which is 7 1/4" deep) is as small as they come. To run ~22' my engineer had me sister these and that got me 25.5" OC. For my smaller room I didn't have to sister.

2) And also is there anything I should consider with respect to the inside out ceiling if I'm doing conventional walls (non-inside out)? My inner leaf ceiling joists are hung from the walls, not built on top. I'm assuming as long as the top plates of the walls are acoustically sealed where they meet the ceiling panels I would be ok, true?

You CANNOT hang your ceiling joists from the walls. Your walls need to be built shorter so that the joists can rest on top of the double top plates. Your contractor will know this. You need to install a sort of rim board (just use regular 2x8's of whatever dimension your engineered joists are). Then you lift your modules into place. Your perimeter modules can rest on top of the walls. I recommend building the perimeter modules first and then build custom sized ones to slip up into the middle. This will allow all of your perimeter modules to rest on top of the walls. The other thing you need to consider is vapour barrier. Remember, it must be snug against the COLD side of your inner leaf sheathing.

3) If I can do inside out ceiling, am I right to think that I could run the electrical wiring through the joists just below my ceiling panels to my track lights to preserve the one entry into the room? This way I could cover that wiring with acoustic treatment after the fact.

Correct. All of your wiring can run up inside of the frame work hidden by your insulation/fabric.

4) If I do inside out, and fill the ceiling cavities with treatment, am I running the risk of making the room too dead with 2-4" worth of 703 or similar?

Possibly, but that's where you can tune your acoustic response with things like plastic, wood slats, etc depending on how your room shapes up acoustically speaking. In a control room it's typical for the entire ceiling to be filled with insulation. As long as you don't put fabric over it during your treatment stage, it's easy enough to tune it as I've described and THEN cover it up with fabric.

5) For my cloud above my listening position, I haven't yet had the chance to properly do my vertical plane ray tracing, but I believe I read Stuart somewhere recommend pulling the cloud away from the baffle wall, as the reflections right up against the baffle wall aren't going to reflect to my listening position. I imagine that it's pretty unique per room, but is there a rough guideline on how far away from the baffle the cloud could be? I'm pretty sure the answer is I need to do the calculations/Ray-Tracing, but I was thinking I might put a track light between my cloud and my baffle wall if there would be enough room, so I am just trying to understand roughly if that is going to be a bad idea or not...

Your electrician can't really run anything because your room isn't built yet. But yes, plan for a lighting circuit in your cloud area. You will have to ray trace it to see how much space you'll have along the front of your cloud. You might only be able to put some strip lighting there. Or heck, maybe your design will end up not having any lights there. Either way, plan to run wires there.

Sorry for the shotgun questions without much context from my side, but my electrician is on site tomorrow and I want to discuss where the lighting should be going with him... I was hoping to have had time to finish my design by now so I would know exactly where to tell him but life has gotten in the way :( . I figure if I can wrap my head around the possibilities a bit better, then I could buy myself the time to finish the design properly.

I've been swamped so I apologize if I haven't been super quick to respond. As you can see, the design stage is the most important. It's not worth rushing anything. You've made great and fast progress. Keep it up! Greg

Hey Greg, Thanks again for all the help. I feel like I have a plan that works now for the HVAC... met with the contractor and found a way to run the 5" Flex duct to the pool equipment room, so now the only thing I still need to do is find an HRV that can go as low as 37.5CFM. Will get on that next.

The larger the distance between joists the better. This is because the sheathing can then flex more. If you look at any tests done, 24 OC is better than 16 OC.

Got it. Thanks!

The other thing you need to consider is vapour barrier. Remember, it must be snug against the COLD side of your inner leaf sheathing.

Is there an acoustical/isolation effect of this? or are you just speaking on the correct place to put it in terms of code/construction?

Possibly, but that's where you can tune your acoustic response with things like plastic, wood slats, etc depending on how your room shapes up acoustically speaking. In a control room it's typical for the entire ceiling to be filled with insulation. As long as you don't put fabric over it during your treatment stage, it's easy enough to tune it as I've described and THEN cover it up with fabric.

Got it. Thanks!

You will have to ray trace it to see how much space you'll have along the front of your cloud.

OK... I took a stab at this, but I'm a bit confused about where to vertically ray trace from. I'm assuming that I do it from each speaker, and not the front centre of my baffle wall. Trying to do this I struggled to do it in 3D in Sketchup so I made a 2D version of the vertical space on the side and came up with this: I was able to clear 2.5' either side of the centre of my head with a 4' long cloud at a 25 degree angle sloping away from the baffle wall... However, when trying to convert this to 3D space, I basically just mirrored the same cloud above the other speaker and got sort of a weird peaked convex shape. I am worried that this method isn't the right way to do this. Here's another angle from a bit higher up so you can see the peak... Also, I'm not sure how I ray trace from the other speaker in the vertical plane given this model, as it starts to present some weird angles. I thought I'd check in to see if there is better approach to this.

I've been swamped so I apologize if I haven't been super quick to respond.

Are you kidding me? Both you and Stuart have been amazing. I don't think I could have gotten this far without you. Thanks again, Aaron

Is there an acoustical/isolation effect of this? or are you just speaking on the correct place to put it in terms of code/construction?

Purely for code and to prevent moisture/rot issues from happening!

Trying to do this I struggled to do it in 3D in Sketchup so I made a 2D version of the vertical space on the side and came up with this:

I do it from the acoustic axis center line of the speakers similar to what you're doing too.

However, when trying to convert this to 3D space, I basically just mirrored the same cloud above the other speaker and got sort of a weird peaked convex shape. I am worried that this method isn't the right way to do this.

That's a pretty cool look but convex shapes are not good acoustically and that would also be very hard to build accurately. Typically what happens after the ray trace is that you just build the cloud straight across the room.

Also, I'm not sure how I ray trace from the other speaker in the vertical plane given this model, as it starts to present some weird angles. I thought I'd check in to see if there is better approach to this.

Draw your cloud straight just like all of the clouds you see on the forum and double check that your RFZ sphere around your head is maintained. Greg

This is such a useful thread to follow, thanks for keeping up the work and detail! Yes the Vapour membrane as Gregwor has said is very important, in the uk you are able to use fairly thin plastic sheet but we normally use the same stuff we use for Damp membranes... slightly thick at corners when folding but you don’t want vapour problems... I’m not sure if this has been covered but do mini splits typically control humidity at adjustable levels or do you need to get certain models that can do it? I should probably google! Tom

I’m not sure if this has been covered but do mini splits typically control humidity at adjustable levels or do you need to get certain models that can do it?

controlling humidity is what all air conditioners do best! It's the first thing they do, before cooling the air. Window-mounted, ducted mini-split, non-ducte mini-split, ceiling cassette, free-standing portable units, whatever... they all work on the same principle, and it's actually not complicated. The cooing cools inside the indoor unit (the ducted or non-ducted AHU) are, well ... ummm. they are "cool". In fact, they are very cold: icy. When humid air comes into contact with a cold surface of those coils and the fins attached to them, the water vapor in the air condenses on the cold metal, into liquid water. It then drips from the cooling fins into a condensate collection tray, and is carried away through a condensate drain. Thus it is gone: removed from the air, and removed from the room. The air has then been dehumidified. That's the FIRST thing that happens when the air passes over the cold fins and pipes in the AHU. The SECOND thing is that it actully cools the air... but only if it is able to do so. There's a secondary issue here. When water vapor condenses into liquid, that is a heating process: it heats up the cooling fins and pipes in the AHU. So if the unit is not powerful enough, it will use up all of it's capacity in just turning the humid air into drier air at the same temperature, but WITHOUT cooling it. The heat generated by condensation will be enough to "use up" all of the "coldness" in the coils/fins, warming them up to room temperature... so they won't be able to cool the air, after they dehumidified it. That's why you need to do the calculations carefully for your HVAC system, to make sure that it has enough capacity to deal with both the latent heat load in the air (humidity), and also the sensible heat load in the air (warmth). The unit cannot remove any sensible heat until it has first dealt with the latent heat. All air conditions work the same way: passing the room air over some type of cooling coils with fins on them, so the issue is exactly the same, regardless of the type you chose. Yet another one of the 47,653 things you need to take into account when designing your studio! :) - Stuart -

Geeze that makes so much sense! Is there a chance it could over dehumidify the air which could cause stringed/wooden instruments to have problems? I guess the heat transfer in an HRV is much less dramatic, but does it also have a condensate tray? Great explanations guys! Thanks! Tom