Question on air exchange for garage studio

[solarpc1]

Hello, I'm new to the forum, so first off I just want to say thanks to anyone who takes the time to respond to my post.

I'm starting in on building a home studio space in the coming months. This is the first studio space I've ever constructed. I will be building an extension off the back of my 3rd stall garage for this purpose, and will be utilizing about 10' of the back portion of the existing garage space (one side wall section of this 10' feet is sharing the wall with my house) - the very front of the garage will still be used for parking a vehicle and loading gear in/out. The overall dimensions will roughly be about 13' x 22' for the interior live room once done, with utilizing the decoupled room within a room design that seems to be most effective based on my research thus far. I'm not going to to be doing a control room, but rather this will just be a single "live" room that will be a practice space where I will occassionally do some basic tracking. I am part of a 5 piece band with drums, bass, 2 guitars, keyboards and vocals, and my main use for the space will be for practicing with the band. It's a hard rock type band, so volumes will be fairly decent (sorry I don't have exact max dB specifics at this time). I have one neighbor on one side with about 25' in between the outside wall of the my garage and the nearest side of their home. Otherwise I have a large perimeter for the studio to any other nearby houses (roughly 60-80' depending on the direction). I feel I have a pretty good handle on the basic construction design and materials to be used for the most part. I do have some further research to do there and will likely come back with questions when I get underway to the interior construction, but for now I'm focusing on the exterior extension build and working on the planning phases for the interior. My questions at this time are mainly with handling heating/cooling and air exchange, as this is one of the critical components I want to get hashed out before jumping in on construction of the studio space itself.

Most likely I will go with a mini-split type system to handle the heating/cooling aspect, since that will give me good sound isolation due to it not being vented to the outside. I know that cooling the room and pulling moisture out of the air will be crucial, so I wanted to have separate control of this from the rest of the home. But I want to run another option by everyone other than a mini-split, and delve into the air exchange aspects, which is where I need the most guidance.

I have looked at these type of hotel-style heating/cooling units ( http://www.friedrich.com/products/resid ... lt-in/ptac) as an alternative to the mini-split systems since they do offer some air exchange, but I'm concerned that sound isolation will end up being a large problem if I employ a through the wall unit like this. That is unless there's some effective way to dampen it on the outside with a "silencer" type box chambered box lined with sound isolation material that I've seen employed for ductwork in some of the studio photos others have posted on the forum, or a secondary mini-room around it. Whatever unit I end up installing, it would be placed on the far side of the building from the nearby neighbors. My question here is should I avoid these type of units altogether if I want reasonable sound isolation?

If it's best for me to stick with a mini-split system, then I have to come up with an effective way to handle the air exchange. I know I will need an inlet/outlet for the air movement. On one wall of the existing garage I could tap through that into the existing ductwork of my house, and add a cold air return on that same wall. This would probably be most ideal for me from a cost standpoint. My questions here is if I employ the duct "silencer" box design (baffled with sound absorbing material lining it) on the inlet/outlet for the studio space, will that be effective enough to contain a majority of the sound from the studio to greatly reduce what would transmit into the house? I understand I will not get 100% isolation this way, but this room is just a family TV room so it's not quite as critical as if it were a bed room. I just know I can't keep my family up at night doing this because we mostly practice in the evenings, so I'm hoping the "silencer" boxes would be sufficient to contain a good portion of the sound. I do not want to start down this path only to find out later this will not be effective enough, so any opinions on this would be greatly appreciated?

If this approach would be effective enough though, do I need to be concerned about putting in additional intake/exhaust fans for the studio room? I currently run the fan on my home furnace at a low speed at all times to circulate air and create a more even temperature distribution throughout the house. Would doing this be effective enough to move air in/out of the studio space if I went this route? The furnace is brand new and has the capacity to move air for the studio addition as well I believe, but I wasn't sure if the chambered "silencer" boxes for the ductwork would inhibit air flow too much for the furnace fan to be effective enough when the room is occupied by people for an extended period of a few hours.

If it's not going to be effective for air movement or for sound isloation to tap into my home ductwork with the "silencer" boxes employed, then I suppose the next best thing would be to get a separate unit like this http://ecomfort.com/vhr-1404-heat-recov ... d-405.html to place within the garage and create an air intake/outlet using the same "silencer" box design for the part that is still inside the garage. But I really would like to avoid the extra cost of having to buy this in addition to a heating/cooling unit if possible.

So with that, I'm just looking for a little basic guidance/feedback on what I've outlined and what any of you feel would be the wisest approach, or if there's another route I should be approaching this from that I haven't thought of or come across yet in my research. I've been looking at just this aspect for the past couple weeks, and have gotten to the point where I just need some direction since where I live I do not have acousticians or construction companies that specialize in this type of design, and the local heating/cooling companies I've talked to do not seem to be of any help either.

Thanks for your time,
Dave

[Soundman2020]

Hi Dave, and welcome to the forum!

Most likely I will go with a mini-split type system to handle the heating/cooling aspect, since that will give me good sound isolation due to it not being vented to the outside.

True, most mini-spits to not have air passages to the outside (although a very few do), so they do have that disadvantage. However, it can be overcome (and MUST be overcome) with a separate ventilation system that draws in fresh air from the outside world, and also exhausts stale air to the outside world: Mini-splits have the huge advantage of being very quiet, since the noisy part is in a separate unit, placed far away, outside the isolation shell, but they also suffer from the lack of ventilation. They are only really H-AC units, as they are totally missing the "V" part of HVAC...

However, you'll find many examples of good ventilation systems to deal with that.

I have looked at these type of hotel-style heating/cooling units ( http://www.friedrich.com/products/resid ... lt-in/ptac) as an alternative to the mini-split systems since they do offer some air exchange, but I'm concerned that sound isolation will end up being a large problem if I employ a through the wall unit like this.

Exactly. Noise is the big disadvantage of "all-in-one" units, such as those. I've just been looking through that web site you linked to, and all the marketing hype bills them as being "quiet", curiously enough the one specification that they are missing from all the tech specs on all their models, is the noise level. I wonder why they don't list it? If that is supposedly one of their marketing points, then why would they not put that information in the brochures? I can take a guess.... (Even more curious: their full catalog, for all of their products, lists the noise ratings for their mini-split and other systems... just not for these ones... Hmmm....)

That is unless there's some effective way to dampen it on the outside with a "silencer" type box chambered box lined with sound isolation material that I've seen employed for ductwork

You mean by mounting the unit outside the studio, then ducting the air in through a silencer? That would work, but I don't see the advantage to doing that. If you want a ducted system, then it would be better to go with a split system that has a proper AHU designed for ductwork.

Whatever unit I end up installing, it would be placed on the far side of the building from the nearby neighbors. My question here is should I avoid these type of units altogether if I want reasonable sound isolation?

I wouldn't use a product for an application that it wasn't really designed to address. I would prefer to use the correct system to do the job properly.

I'm just wondering what the advantage of these units is: are the a lot cheaper than other units you have looked at?

If it's best for me to stick with a mini-split system, then I have to come up with an effective way to handle the air exchange.

The normal method in that scenario is just to use simple flexduct with in-line fans and silencer boxes: one for bringing fresh air in, the other for the stale air exhaust.

On one wall of the existing garage I could tap through that into the existing ductwork of my house, and add a cold air return on that same wall. This would probably be most ideal for me from a cost standpoint.

It might be possible to do that, but you should get an HVAC expert in to check that your system can handle the extra load. It might not have been sized to handle more than it is already handling.

My questions here is if I employ the duct "silencer" box design (baffled with sound absorbing material lining it) on the inlet/outlet for the studio space, will that be effective enough to contain a majority of the sound from the studio to greatly reduce what would transmit into the house?

Yes, if you design and build them correctly. There are several principles operating in a properly designed silencer, and they all work together to block the passage of sound while allowing the passage of air. The three main ones are impedance mismatch, multiple turns in the air path, and extended path length. Acting together, they can indeed stop the sound from getting through while also not increasing the static pressure too much.

If this approach would be effective enough though, do I need to be concerned about putting in additional intake/exhaust fans for the studio room?

Probably one additional fan will be enough, in either the supply duct or the exhaust duct. Since the room is sealed absolutely air-tight, then blowing air in through one duct is enough to force air out through the other. Or sucking air out through the second one is also enough to draw air in through intake.

but I wasn't sure if the chambered "silencer" boxes for the ductwork would inhibit air flow too much for the furnace fan to be effective enough when the room is occupied by people for an extended period of a few hours.

If the system has the capacity to handle the studio area as well, and you have suitable in-line booster fans, then there should not be an issue. The silencer boxes should not increase the static load too much, unless it is already near the limit. You probably need to get a qualified HVAC expert in to do the measurements, look at your system, look at your plans for the silencers, and give you his verdict.

If it's not going to be effective for air movement or for sound isloation to tap into my home ductwork with the "silencer" boxes employed, then I suppose the next best thing would be to get a separate unit like this

That's just a heat exchanger: I don't see why you would need that. It won't cool or heat the room. All that it does is to transfer the heat from the outgoing air to the incoming air (or vice versa), but it doesn't do any actual heating or cooling. There's no point to that unit, unless you live in a very cold climate and want to recover some of the heat from the exhaust air by transferring it to the supply air.

So with that, I'm just looking for a little basic guidance/feedback on what I've outlined and what any of you feel would be the wisest approach, or if there's another route I should be approaching this from that I haven't thought of or come across yet in my research. I've been looking at just this aspect for the past couple weeks, and have gotten to the point where I just need some direction since where I live I do not have acousticians or construction companies that specialize in this type of design, and the local heating/cooling companies I've talked to do not seem to be of any help either.

I would go with one of the "tried and true" methods commonly used in home studios. Probably the simplest is to just tie in to your existing HVAC system, if it has the capacity to do that, using dampers, silencer boxes, ducts, and fans. Second best would be a mini-split system plus a pair if ducts going through ducts, silencers, and (a) fan(s). Third would be a full-blow ducted system, with an AHU. And fourth would be .... ummm.... OK, there is no fourth...

- Stuart -

[solarpc1]

Thanks for taking the time to reply Stuart.

I saw another person mention that Fantech unit in one of their posts talking about air exchange, so I hadn't caught that it was just a heat pump, but rather I had thought it was used for cycling air in/out of a space based on their description.

I was also leary of the through the wall TPAC systems, but they seemed promising for my needs other than concerns I had about sound isoloation. I had come across these units in my research, and they were also briefly mentioned in Rod Gervais's book that I recently picked up. But he did not really go into if they were a good solution or not, but rather simply that they were available.

I was just looking at all of these various units to try and figure out the best way to deal with my studio space and keep things isolated. It's a hard thing to pin down, as most information on studio design topics seem to focus on layout/construction and most overlook or do not spend much time on this simple/base requirement. There is some knowledge out there on designing a space with it's own full HVAC system (like for a typical professional studio), but it's a lot harder to pin down which is the best way to go for a cost-effective approach from home studio perspective. I've tried talking with a few local heating/cooling places at a local home show recently, but when I start talking about sound isolation they just give me blank stares since they are just used to dealing with simple HVAC requirements of typical homes.

So with all of that I'll probably just start with utilizing my current home ventilation system as you suggested. I'm really glad to hear that the baffled duct silencers will be effective enough such that I can tap into my home's ductwork for air circulation and whatever heating/cooling I will get from that. I'll be sure to check with the people that installed my furnace (brand new last fall) to ensure it has enough capacity to handle the new space of the addition reasonable, but I expect I will be covered. I'll plan on installing an inline fan on just the inlet for the room to help draw air in when in use, as you suggested. I'll probably just wire this to a lightswitch so I can turn it off/on, and just have it running when the room is in use. Would it be wiser to put the fan before or after the duct silencer, or does it really matter? I do want to place it at some point where I have relatively easy access to it down the road in case it ever burns out or needs to be replaced.

I think for now I will just start with using the home ductwork by itself and see what kind of results I get once the space is completed. I expect it to be pretty efficient with all of the layers of drywall/insulation (I'm going to use a 2 leaf system with the interior decoupled room) that heating probably will not be as big of an issue...especially during a practice session. I figured I could just pick up a portable free standing air conditioner that I could place in the room to help control humidity and keep the temp down when in use, or a simple electric heater in the winter if needed (I live in Montana, so winters can be cold at times). Then, if either units make any noise I would just turn them off temporarily when doing any recording. If the heating/cooling is not managed effectively enough though these means, I probably will just add a mini-split system down the road to address this.

Thanks again for your advice on this topic. Is there an ideal number of minimum "S" shaped turns one should do within the silencer box to be effective, and is there a number of turns that if you go over it does not really provide any more benefit? Most examples I've seen people build have 3-4 turns in them.

Also, since I have your attention on this topic and given that I'm looking to start breaking ground on the garage addition in the coming few weeks, I have the option of keeping the space as a rectangle that is roughly 14'x24' (WxL) (14'x10' is currently part of the existing garage structure) OR I can do an additional bump out one side of the garage to give myself an additional 4' of width for 14' of the length on one side making it more of an "L" shaped room instead. I'm leaning towards bumping out the one side a bit since the extra space would be nice to maybe put a vocal booth in or simply store additional gear/recording equipment so they do not take up space in the overall "live" room. The picture I've included is the rough layout of the two approaches. Will doing the "L" shaped type room pose any problems for me in terms of sound isolation? Again, the purpose of this room is mainly a live practice space, but I will be doing some recording here as well. I likely will not have a control room just because of space limitations, as I have a 5 piece band where everyone plays an instrument and it's no fun to be crammed together during a practice. The attached picture gives a very rough layout of the two options I'm looking at, and my preference is the second option. Any opinions on this? Again, it is just a rough design and I know I will be doing a lot more interior acoustical treatment down the road. At the moment I'm focusing on getting the external structure (leaf) component completed.

Dave

[Soundman2020]

I've tried talking with a few local heating/cooling places at a local home show recently, but when I start talking about sound isolation they just give me blank stares since they are just used to dealing with simple HVAC requirements of typical homes.

Exactly. In their normal work, they have no reason to be concerned about the things that are most important to a studio, so they know nothing about it, unfortunately.

So with all of that I'll probably just start with utilizing my current home ventilation system as you suggested.

It would be good to find out what the rated capacity of that system is, to make sure that it is able to handle the load. But assuming that it was designed to do the entire house, including the pace where your studio will be, then you should be good. But it would still be advisable to find out for sure: don't take my word for it!

I'll plan on installing an inline fan on just the inlet for the room to help draw air in when in use, as you suggested. I'll probably just wire this to a lightswitch so I can turn it off/on, and just have it running when the room is in use.

Get one that you can adjust the speed, as needed. Not all fans are speed controllable.

Would it be wiser to put the fan before or after the duct silencer, or does it really matter?

On the other side, away from your room! Fans make noise themselves, so put the silencer in between your room and the fan.

I do want to place it at some point where I have relatively easy access to it down the road in case it ever burns out or needs to be replaced.

Yup! I'm not sure how your room is built, but if it is two-leaf MSM then you might find that you have enough space to put it in the air gap right next to the doors, in between them, for easy access for cleaning, maintenance, repairs, adjustment, and replacement.

I figured I could just pick up a portable free standing air conditioner that I could place in the room to help control humidity and keep the temp down when in use,

probably not! Those units still need some place to send the heat that they remove form the room. Portable units usually have a large air hose on the back that you need to direct outside...

I'd suggest going with a mini-split system: they are the most practical for home studios.

Then, if either units make any noise I would just turn them off temporarily when doing any recording.

A lot of people think the same way at first, but in reality that just isn't practical, for many reasons.

Thanks again for your advice on this topic. Is there an ideal number of minimum "S" shaped turns one should do within the silencer box to be effective, and is there a number of turns that if you go over it does not really provide any more benefit? Most examples I've seen people build have 3-4 turns in them.

Three or four is about right, unless you have extreme isolation needs. The biggest issue is to ensure that you keep the cross sectional area inside the box as constant as possible, and at least twice that of the duct itself.

OR I can do an additional bump out one side of the garage to give myself an additional 4' of width for 14' of the length on one side making it more of an "L" shaped room instead. I'm leaning towards bumping out the one side a bit since the extra space would be nice to maybe put a vocal booth in or simply store additional gear/recording equipment so they do not take up space in the overall "live" room. The picture I've included is the rough layout of the two approaches. Will doing the "L" shaped type room pose any problems for me in terms of sound isolation?

Not for isolation, no, but it might affect internal acoustics. Most likely, for the good! Bigger rooms (more volume) sound better in general, so if you can do it that way, it would probably be beneficial. Provided that you don't plan to use that space for mixing (not as a control room), and it will just be a live room / rehearsal room, then that makes sense.

- Stuart -

[solarpc1]

So I've spent most the past summer adding an addition onto the back of my existing garage, which will be tied into the home eventually too for ease of access. I'll probably start a new thread under the studio build section shortly and put up some pictures of what has been done thus far, but I have a question about adding drywall to the outer leaf/exterior wall that I was hoping to get a quick answer on since I'm about to start on that phase of the build.

I have used Green Glue Acoustic Sealant to seal everything up all the way around the room and now I'm ready to start fitting drywall into each of the wall stud pockets (planning on two layers of 5/8" drywall with further caulk on each layer). I'm not going to use the Green Glue Compound between the drywall sheets on the outer leaf layer just for cost containment concerns, but I will eventually use it on the drywall for the inner leaf/decoupled room once I get to that phase.

My question is if I'm fine with screwing the drywall directly to the exterior OSB sheeting on the addition (caulking any screw heads of course), or is there a preferred approach for mounting the drywall in this situation (like furring strips of wood along the edges to retain the drywall so you aren't piercing the drywall, etc.)?

Also, is it better to fight the drywall tightly in the pockets or leave a bit of gap around the edge (between drywall and studs) to fill with caulk in terms of isolation? Or is it so minute of a difference that it doesn't really matter either way? Like I said, I'll be caulking the perimeter of each drywall sheet on each layer regardless.

With the amount of money I'm putting into this build I just want to make sure I'm doing things correctly at each step. Thanks in advance for any advice.

Dave

[Soundman2020]

Good to see you around still Dave!

The recommended method for "beefing up" (the highly technical scientific term for what you are doing... ) is to cut the drywall a fraction smaller then the stud bay so it will fit in easily, then seal all around the edges with acoustic sealant (or even good quality flexible caulk), and hold it in place with cleats along the edges, nailed sideways into the studs. That gap around the edge doesn't need to be big: if your caulking technique is good, you'll be forcing some caulk into the gap, which is good.

With this method you avoid having to screw through the drywall, and still hold it in securely. If you are going to do two layers, then do the first one and put in temporary cleats, then when the caulk is set take out those cleats, put in the second layer, and the final cleats.

- Stuart -

[solarpc1]

As always, thanks for responding Stuart. I'm hoping to get started on the drywall shortly, but not sure how far I will be able to get before the weather shifts to be too cold for the caulk to set up properly, as I live in Montana and temps are starting to drop. Since I'm doing this in a garage addition, at present I do not have the ceiling/room completely closed off (it's vented to the exterior), so there is no way to regulate the heat.

I'm hoping to get as far as I can with the drywall in the walls, and then shift to getting the ceiling closed off for the external leaf. I'm actually going to be stuck with a 3 leaf system on the ceiling, which was unavoidable. But there's a pretty good air gap between the 2nd and 3rd leaves from anywhere between 6 and 10 feet for most of the space with the way the attic space worked out (this will make more sense when I post pictures), so hopefully it won't be a huge issue. Once I get the ceiling wrapped up I'll run electrical to drop power lines around the room before I start in on the inner room/leaf. I had a separate power sub-panel placed in the garage that will give me up to 12 circuits for the studio space, so my plan is to put each outlet on it's own breaker, lights (LED most likely) and the inlet fan on a single breaker, and finally 2 breakers for the mini-split system I'll add next spring.

I think I'm going to try and head the route of using a single "super door" for the two room entry points versus the double door airlock. I may still do the double door for the exit to the garage (that point will be more for load in/out for gear for my band when having practice or doing gigs), but between the studio space and my home I would like a single door to make it feel more part of the home. In just starting to research the door situation I ran across this. https://soundisolationstore.com/shop/pr ... tion-door/ It seems like this would fit the bill well, but that's pretty pricey for just a door. Do you have any other recommendations for a drop in door setup that would be as effective, but more reasonable in cost? I could always go the route from the Rod Gervais book where he constructs his own super door by getting a solid core door and adding a sheet of lead to it and plywood over that (if memory serves me), but again since this is part of the home I was looking for something with a little nicer finish appeal. I'm open to suggestions though.

Dave

[Soundman2020]

I'm actually going to be stuck with a 3 leaf system on the ceiling, which was unavoidable. But there's a pretty good air gap between the 2nd and 3rd leaves from anywhere between 6 and 10 feet for most of the space with the way the attic space worked out (this will make more sense when I post pictures), so hopefully it won't be a huge issue.

You should be fine like that. The gap up there is plenty big enough that there won't be much of a 3rd leaf effect anyway.

I had a separate power sub-panel placed in the garage that will give me up to 12 circuits for the studio space, so my plan is to put each outlet on it's own breaker,

Great! But you can make those double outlets if you want: it's hard to have too many outlets in a studio! And don't forget star-grounding...

I think I'm going to try and head the route of using a single "super door" for the two room entry points versus the double door airlock. ... It seems like this would fit the bill well, but that's pretty pricey for just a door. Do you have any other recommendations for a drop in door setup that would be as effective, but more reasonable in cost?

Buying ready-made acoustic isolation doors is pricey! They don't come cheap. Rod's design is a darn good DIY alternative, for a lot lower cost.

but again since this is part of the home I was looking for something with a little nicer finish appeal

You can still make Rod's design look really good: He just shows the construction details, but the final finish surface is up to you. You could face the door with any type of wood you want, perhaps stained or varnished to look really nice, then make the trim from the same type of wood. It could look just as good as the commercial door that you showed in your link. And it would certainly work out a lot less expensive!

- Stuart -

[solarpc1]

So I have the electrician finally coming this week...now that the bills from the holidays are dealt with I can get things moving again. Basically at this time I'm having him drop power lines from the sub-panel in the addition so I can then get to work closing off the ceiling of the external room leaf. Then it won't be so cold when I'm working out there, as it's just the open trusses at present and vented to the outside.

As part of this, I've been planning out all the electrical lines I need ran. At this time I'm planning on having one 120V circuit for LED lighting/air exchange fan, 5-6 120V circuits for wall outlets, and one 220V circuit for a mini-split system. I will be talking to the electrician about star grounding. I may also need another 220V circuit for supplemental electric heat. That is where my current question comes in...

I have been researching mini-split cooling/heating systems and have gotten a couple estimates (and was surprised at how expensive the quotes were: $2500-3500 range), and I find that most units only operate with a heat pump for the heating aspect. Most of the time this would be sufficient, but I do live in Montana and there are usually a number of weeks each winter with sub-zero temperatures where a heat pump will not keep up and I would need some sort of supplemental electric baseboard/cove heating. Given that, would you just get a mini-split unit to handle cooling only with and stick with a separate electric baseboard/cove heater for the heating aspect? Of course, I'm not sure how much difference this would make in my electric bill if I took that approach since from what I've read heat pumps are more efficient. I want to take the best approach for the room, but I'm already a bit frustrated based on the estimates I've been getting to see that they want to charge nearly as much as I paid for a new furnace and A/C coil for my house a couple years back when I'm just dealing with heating/cooling a single room. Mainly, I'm just trying to find that balance between cost, reliability, and efficiency.

I did also find a unit that states it has an electric heat backup in the mini-split itself, which would be more ideal to handle my situation with a single solution and it's more cost-friendly. But it's not what I would call a known name brand (Soleus), and there are not a lot of reviews on it I can find so that gives me pause. Here is the link to the unit http://www.ajmadison.com/cgi-bin/ajmadison/KFTHP12.html so you can see the specs. Do you think this would be a good approach to go? It definitely seems more cost effective than a number of others I've looked at, but that could also be an indicator of quality/reliability. Alternately, if you were going to recommend a preferred mini-split system brand/model, which would you go with? A 9,000BTU unit would be sufficient for my space...I was just looking at that 12,000BTU model because they did not have the electric heat backup on the 9,000BTU models. Any suggestions/input on this would be greatly appreciated.

Dave

[Soundman2020]

was surprised at how expensive the quotes were: $2500-3500 range

I never have figured out why they are so damn expensive in the USA! Where I live, I'd pay about one fifth of that for a small unit! Take a look here:

http://www.sodimac.cl/sodimac-cl/produc ... NavAction=

That's a 9000 BTU unit for a lot less than US$ 600. And here:

http://www.sodimac.cl/sodimac-cl/produc ... NavAction=

That's an 18,000 BTU unit for under US$ 900! (The Chilean peso is about 550 to the dollar right now). That's just one hardware store (similar to Home Depot), and you can sometimes get them even cheaper than that. Right now, they are premium products here, since it is mid summer, but in a few weeks their overstock will be on sale, and the prices will be even lower.

So I have no idea why you guys have to pay five times the price in the USA: Somebody is making a huge killing, at your expense!

and I find that most units only operate with a heat pump for the heating aspect.

Those two (above) are both heat/cool units. The same capacity in both directions. (eg. 18,000 BTU heating, 18,000 BTU cooling). Normally, if you need 18,000 BTU cooling, you probably need LESS heating capacity, since there are several other things that are also heating your studio: you, your gear, your lighting, etc..

Most of the time this would be sufficient, but I do live in Montana and there are usually a number of weeks each winter with sub-zero temperatures where a heat pump will not keep up

Why? Even when if it is way below zero outside, a good head pump can still extract a lot of heat from that. Also, since your studio will be very, very well insulated from the outside world (huge amounts of mass, multiple layers of insulation, total air-tight seals, large air gaps, etc.) there will be very little heat loss through the walls.

Given that, would you just get a mini-split unit to handle cooling only with and stick with a separate electric baseboard/cove heater for the heating aspect?

I would hire a local HVAC expert to take a look at your plans, your gear, your room occupancy, your thermal insulation level, and do the math to properly calculate how much heat you will be losing through the building structure on the coldest day of the year, then use that information to decide which HVAC unit you need, and whether or not it will need supplemental heating. My guess is that you won't need any supplemental, or if you do, it will only be minimal.

Of course, I'm not sure how much difference this would make in my electric bill if I took that approach since from what I've read heat pumps are more efficient.

Right! MUCH more efficient. Mini-split systems use the phase-change effect of the refrigerant fluid to move heat from outdoors to indoors when heating, or indoors to outdoors when cooling. That's what is actually getting your warm, or cool, NOT the electrical power. All that the electrical power does, is to run the compressor and fans. So the unit can draw (for example) 2000 watts of electrical power, yet provide 5000 watts of heating (or cooling). On the other hand, to provide 5000 watts of heating with a supplemental heater, the heater needs to draw 5000 watts... And that assumes it is 100% efficient. It might need to draw even more power if it is not efficient...

But it's not what I would call a known name brand (Soleus), and there are not a lot of reviews on it I can find so that gives me pause. Here is the link to the unit http://www.ajmadison.com/cgi-bin/ajmadison/KFTHP12.html so you can see the specs.

It looks fine to me. I have bought a few non-"name brand" mini-splits over the years, and been quite happy with them. They are very simple units: just a compressor, two fans, and some control circuitry. Not much to go wrong. If you buy it from a reputable company that offers a good warranty and is known to actually meet their warranties, then you should be OK.

Do you think this would be a good approach to go? It definitely seems more cost effective than a number of others I've looked at, but that could also be an indicator of quality/reliability.

Or it might indicate that you are buying closer to the source, at a more reasonable price, without multiple middle-men robbing you blind! That price is much more in line with what I would expect to pay for a decent unit, where I live. And think of it this way: you can afford to buy four of those units for the price of ONE of the other units you have been quoted, so even if it fails four times over its useful life, you are still no worse off!

A 9,000BTU unit would be sufficient for my space...

Are you SURE about that? I have a couple of 9,000 BTU units in my home (one in my office, one in my bedroom), and they only barely handle the load on hot days. If I were to do it again, I would pay a few dollars more and buy 12,000 BTU units. The correct way to figure out how much cooling you need is rather complicated, but basically you need to figure out your "sensible heat load" (how much heat you will be producing inside the room (people, equipment, lights, etc. and how much heat will be coming in from outside), and your "latent heat load", which refers to how much heat the unit has to remove from the air just to account for the relative humidity, before it can even start changing the temperature of the air. If you live in a very hot, humid area, then the latent heat load can be quite high. In that case, the unit can run full-bore and not cool the air at all, simply because it is using all of its capacity just to extract the humidity from the air. For example, if your latent heat load is equivalent to 7,000 BTU/Hr in summer, and you get a 9,000 BTU/Hr unit, then you only have 2,000 BTU/Hr of actual cooling capacity, which is not much at all. If you got the 12,000 BTU/hr unit, you'd have 5,000 BTU of actual cooling capacity, which is much better, and with the 18,000 BTU/Hr unit you'd have 11,000 BTU/Hr of actual cooling, which is really good. On the other-other hand, if you live in a relatively dry area, where humidity never goes above 20%, then you don't need to worry too much about latent heat load since practically all of the capacity of the unit goes directly into actually changing the temperature of the air.

So you do need to figure that out carefully, to be sure you are getting the right unit!

On the other-other-other hand, you also do NOT want to over-dimension the unit. If you do, then it's duty cycle will be very short: it will come on for only brief periods, blast you very cold and very dry rather quickly, then stay off for a long time... so the temperature an humidity in the room will swing wildly from one extreme to the other. If you dimension the unit correctly, the duty cycle will be about 40% to 50% on the low setting, give or take, so it will be keeping the temp and humidity fairly constant, while still having excess capacity to take on those extreme days with the high setting.

In other words, you have to do the math to figure it out correctly for YOUR room where YOU live. Don't just buy a unit because the sales brochure says that 9,000 BTU is good for a room with xx square feet of floor area! Garbage! It is much more complicated than that.

- Stuart -

[solarpc1]

Thanks again for the feedback Stuart...wow, I must say mini-split units in your neck of the woods are MUCH more reasonably priced!

After discussing this further with the heating/cooling people they agreed that a 12,000BTU solution would be best for my 425 square feet room to have a bit of extra coverage if needed, so I'll go that route. Both the heating/cooling people and my electrician still thought I would need supplemental electric heat just for those really cold times of the year. We did have a stretch this winter where it was about -20F for 3 weeks, which isn't all that uncommon for winters here to have a few weeks like that each year. I just don't know that they exactly grasp what I'm doing, as I've had to articulate it repeatedly to both parties to get them to wrap their heads around it since it is not a typical home construction situation. I have discussed the very insulated nature of my room within a room design with them, and they still thought it would be necessary. That is why I was looking to see if I could find a mini-split that had electric heat backup, so I wouldn't have to run another 240V for cove heating (electric heaters mounted more towards ceiling versus baseboard electric heaters - want to keep those away from any studio gear) or have more than one wall unit.

That Soleus model is literally the only brand I could find online with electric heat back-up. I do like the idea of an all in one unit, but it makes me wonder why no other manufacturer has taken this approach. Do they make mini-splits with electric heat back-up built in where you live? But I do think it might be worth the risk for the dollar savings alone to go with a more generic brand...I just can't quite choke down that $3600 price tag for the Mitsubishi model they were recommending for just heating/cooling a single room. The electrician is going to drop the main power lines in the studio next week before I close up the ceiling, so I'll need to decide quickly what I want to do there. We do have more of a dry climate here, so that is not as big of a concern at least.

[solarpc1]

What is the best type of insulation to use for sound absorption (mineral wool, fiberglass batting [paper backed or not], etc.)? I'm hoping to start putting some of that up in the walls of my external leaf room in the very near future. I'm sure not all types of insulation are created equal from a sound absorption point, so I'm trying to figure out best material for the job. For example, if chosen, does the paper on the paper backed fiberglass causes any sound absorption concerns, etc. It seems like a lot of people on the forum use mineral wool for their studio spaces, so I thought I'd just ask to see what is the typical preference. Any input is appreciated.

Work has been super crazy for me lately and slowed things down a bit on the studio build, but it's going back to normal and I'm finally going to get around to setting up a studio build post here shortly to share the progress of my project as I move things along.

Dave

[Soundman2020]

I'm sure not all types of insulation are created equal from a sound absorption point,

They aren't!

The property that actually matters is a technical characteristic called "gas flow resistivity" or "GFR" for short. It is sort of like a measure of the impedance that the material offers to air moving through it, and therefore also to sound waves, which at the most basic level, is just air molecules moving.

Unfortunately, most manufacturers of insulation don't bother measuring or publishing the GFR numbers for their products, simply because their products are design mostly for thermal insulation, not so much acoustic isolation. Fortunately, there's a rough relationship between the type of insulation, the density of that insulation, and the GFR for that insulation. So if you know the density and the type, you can get a good idea of what the GFR would be, even if it has not been measured.

It tuns out that for isolation walls, if you use fiberglass insulation the you need a density of around 30 kg/m3, and if you use mineral wool, then you need a density of around 50 kg/m3. So that's what you should be looking for.

There is some evidence that paper facing on one side of the insulation can improve isolation slightly, but it's not a huge effect.

- Stuart -

[solarpc1]

The whole studio build process is pretty fascinating in all that you have to consider...luckily each step takes so long that you have plenty of time to mull stuff over. thanks for being such a great knowledge resource Stuart. \m/

Well, I ended up selecting/installing Roxul ComfortBatt mineral wool insulation for the exterior walls before you responded, and it doesn't have the density you were recommending. http://www.roxul.com/files/RX-NA_EN/pdf ... withSS.pdf

I had done some digging online, and it seemed like a large number of people were for mineral wool for its sound absorption properties, but then I also saw people say that fiberglass was better. In the end I went with mineral wool for some of its other characteristics. It does have a higher R value than the same thickness fiberglass. It costs a little more, but I also like the idea of the fire/water/mold/pest-proof nature of the material. Since it doesn't burn, I was actually planning on using small strips of this stuffed between the inner/outer leaf wall frames along each corner section to ensure proper fire breaks, which would still be essentially decoupled in nature. I'm glad I got Rod Gervais's book, or I would not even have considered the need for fire breaks.

I was planning on using the Roxul Safe & Sound mineral wool for the interior room walls, since it's more geared towards sound containment instead (STC rating of 52). It doesn't really have much of an R value rating, so that's why I went with their normal insulation for the exterior walls instead of the Safe & Sound. But the Safe & Sound product is more in line with the density you were recommending, and would be fine on the interior room walls where the R value is not really as important. http://www.roxul.com/files/RX-NA_EN/pdf/SafenSound.pdf

Am I going to take a big hit in sound isolation performance by using the insulation I've selected?

I'm nearly finished with the exterior leaf room...all I have left is one layer of drywall to add to the ceiling and the insulation on the ceiling, and then I'll be able to start framing up the walls for the inner leaf room. I decided in the end that it would be easiest for me to go with the double-door/airlock setup for the entry into the room. I did have one question about the best way to handle the transition in regards to this between the inner/outer leaf rooms since the goal is to keep the two rooms decoupled. I'm using this Iso-Sill product (http://isostore.com/shop/product/pliteq ... nking-pad/) under the base plate sill for my inner leaf wall frame. I was wondering if I ran a strip of that along the whole frame of both door jams and then screwed a solid broad door frame plank between the two rooms with the Iso-Sill in between if that would be an effective enough decouple of the inner/outer leaves? There's still going to be some direct contact just from the anchoring screws through the door jam into the frame, but the majority of the surface area would be isolated. I like the idea of a fully enclosed door frame between the two if it is not going to cause sound transference problems by taking this approach. What is the best way to handle the transition and still keep it looking clean?

Dave

[Soundman2020]

I had done some digging online, and it seemed like a large number of people were for mineral wool for its sound absorption properties, but then I also saw people say that fiberglass was better.

Either one will work. Both have some advantages and disadvantages, but both types do the job very well.

I was actually planning on using small strips of this stuffed between the inner/outer leaf wall frames along each corner section to ensure proper fire breaks,

Right! That is, indeed, the best way to do that.

I was planning on using the Roxul Safe & Sound mineral wool for the interior room walls, since it's more geared towards sound containment instead (STC rating of 52).

Careful! Insulation alone will NOT get you STC-52! Not even close. Not even DISTANTLY close. Insulation is really lousy at isolating, when used by itself. You will only get STC-52 if you use it as part of an isolation system.

Also, be careful with STC ratings... STC is no use for measuring studio isolation: It was originally meant for putting a single number to indicate isolation in typical house/office/shop/school walls, where the "noise" is moistly voices, telephones, HVAC air noise, typewriters, office equipment, and suchlike. Not meant for music. STC does not even consider the bottom two and a half octaves of the music spectrum at all! Drums, bass, the low end of keyboards and electric guitars, etc. just aren't taken into account when calculating the STC rating for a structure. so you can quite easily have a wall rated at STC-50 that does a really lousy job of isolating a studio, and another wall rated at STC-40 does an amazing job.

When talking about studio isolation you should be talking what is knows as "Transmission Loss" or "TL", which is basically a graph that shows isolation across the entire spectrum, and can be summed up reasonably accurately by measuring the "inside" and "outside" levels with a decent sound level meter set to "C" weighting and "slow" response.

"STC-52" does not mean that the wall provides 52 dB of transmission loss...

Safe-&-Sound is good stuff, and will work fine, but don't believe the hyped numbers that some distributors throw around misleadingly.

One product that you didn't mention, that is really good four acoustics: Owens Corning OC-703.

I was wondering if I ran a strip of that along the whole frame of both door jams and then screwed a solid broad door frame plank between the two rooms with the Iso-Sill in between if that would be an effective enough decouple of the inner/outer leaves?

Nope! Because you would not have the weight of the wall on that strip there, and neither would you have the solid floor underneath... Right product... wrong application....

The normal way of filling in between leaves is to wrap a piece of 703 with fabric, and press-fit that into the gap. Covers it very neatly (aesthetically), and also keeps the two sides decoupled, acoustically.

There's still going to be some direct contact just from the anchoring screws through the door jam into the frame, but the majority of the surface area would be isolated.

Therein lies the problem: Those screws would be perfect flanking paths. Not even ONE screw can bridge the gap.

What is the best way to handle the transition and still keep it looking clean?

As above: fabric-wrapped 703, press-fitted in place, or perhaps hot-glued on ONE side only, to keep it firm.


- Stuart -