help with airducts in my home studio DIY project

Hey...I have been on here everynow and then, so being stuck on the following topic led me here for wisdom and counsel! I have been building a home studio in my basement (I have never done ANYTHING of this sort...I am totally a newbie). It consists of 3 rooms...A tracking room roughly 10 ft x 13 ft, a drum room about 10ft x 9 ft and a vocal room 5 ft by 8 ft. Above this area in my basement is 2 two bed rooms. Here are things I am really wanting and sort of concerned about: 1) I want the noise in my studio to be totally trapped, not leaking to the rooms above or anywhere else for that matter. I am double sheet rocking with two layers of 5/8 drywall, and the rooms all have their own walls. The ceiling does not touch the rafters holding the floor for the above rooms. 2) I would like to have air vents from my heating and cooling system in the studio area. So...I will just rattle off some of my issues. Correct me and please add advice...if I have air vents in the room attached to the existing air ducts which lead to the rooms above, will sound leak to rooms above, even if I use insulated ducting? Will the holes made in the drywall for vents make sound leak through the opening? Could I even tap into an existing airduct? What issues would I face if I did this? I know this basement area is usually cool...so part of me kind of wants to not deal with the hassle of cutting an existing airduct to allow me to attach an air vent for my room. I am however afraid that with the equipment in the room and lights (I will be putting track lighting with 5 35watt bulbs in each room) will cause heat...and I am not sure if that heat will make that area overly hot. Even if I cut into the airduct, I AM NOT SURE HOW...if this is something people usually do, could you expain how I go about it? And also, I am concerned that tapping into existing ducting will make the airflow into the above rooms diminish.... I am now open for input. I will post some pics to give you an idea of what I am looking at in my ceiling.

Based on the tools, your layout, the drink can and type of insulation you are using, I can tell to within about two counties where and in what state of America you are. If there were a window open and you held a clock up I could also tell you the time there :) I wonder if any of the Australian brothers and sisters >>>where this forum originates<<<, can do that? Maybe you could tell us all and ease the burden? Welcome, Brien

I can see the clock but it's upside down!

A couple of comments: It doesn't matter where you live or how cool the basement is under normal conditions, you absolutely *have* to have ventilation and fresh air!!! Air-tight rooms will also get hot very quickly, especially with gear and people in there. Lack of oxygen also makes people cranky and get tired easily, and you will have a difficult time making good music in an otherwise awesome build out. You must provide HVAC and fresh air, you will be so sorry later if you do not. You are going to all of this work, don't ruin it by skimping here. All I can say is you have been warned!!! :lol: Next, I am going to scold you a bit here (sorry!)... you should have thought about this earlier rather than waiting until you are all framed in and insulated. Your job will be more difficult now, but it is still do-able, so you are not sunk yet! HVAC is one of the most important things that you have to include in your planning, it impacts your ability to work *and* your ability to isolate sound. It is critical, yet it appears to me that you have left this to the end and have not put much thought into it. All I can say is that when you are done, you are going to wish that this was the FIRST thing you thought about, rather than the LAST. Poor planning here can ruin an otherwise great studio build. It is possible for you to cut into the existing air ducts, but that is not advisable. You really should be tying into the main trunk (usually a big rectangle-like metal "tube") where the smaller round ducts tie into. Cutting into smaller ducts is going to make them much less efficient at the far end. Once again, if you had been planning better earlier on, this would have been easier... Also remember that you not only need outlet vents, but you also need cold air returns in EACH room. Otherwise, it is like trying to blow air into a coke bottle, it just will not work. For example, in my control room, I have 2 exhaust vents, and 1 return vent. This is CRITICAL!!! Regarding sound transmission... Sound will travel through these ducts, without doubt, and it will be even worse if you are tying into the small round ducts rather than into the main trunk line as I described above. The best way to avoid this is to install a small, dedicated, split HVAC system dedicated just for your studio. Sounds like that is not going to happen at this point, especially if you are asking these questions so late in your build. One way to help *reduce* sound transmission through the ducts is to build duct silencers. Search this forum, there are several examples around here. These will help some, but will never truly isolate sound. Your sound isolation is only as good as your weakest link, and even if you build the most awesome wall/ceiling/window/door isolation in the world, if your HVAC leaks sound, you might have wasted a lot of money in the rest of the build out since sound is just going to POUR out of your HVAC vents. They are just like sound tunnels, and since you asked, insulating them does not help, it is still a hollow tube where sound will travel. Where air goes, so goes sound. Try to include as many right-angle bends as you can in the duct work, this will help some, and look into the silencers as I mentioned. Another issue to consider: When you tap into the main HVAC system, you are also now a slave to how someone else in the main part of the house has the thermostat set! This is especially bad in the winter when someone upstairs has the heater going, and you are suffocating down in the basement due to bodies and equipment. Trust me on this one!!! There are formulas around that are used to calculate how much HVAC you will need based on size, the amount of equipment, and the number of bodies that will be in the rooms, etc., and I can pretty much guarantee that you will NOT have enough if you are tapping into the main system!!! Check out this book, it will help you out immensely in this area: "Home Recording Studio Build it Like the Pros" By Rod Gervais ISBN: 1-59863-034-2 Amazon Link for Rod's book Good luck, you have some very difficult decisions to make, ones that should have been made a long time ago (sorry if I seem harsh!).

the one tip I could add to this is when tapping in to your existing HVAC, do so way back at the air handler unit and run metal lined duct to each room, send and return. Once inside the room, continue the duct around the ceiling at least one 90 turn and then soffit that in with drywall or you can create a frame around it, fill with rockwool and cover in fabric to create bass trapping as a part of the duct design. Bringing that duct around inside your room will help room-to-room isolation and quiet down the air noise a bit. -ashley

doublehelix wrote:

...and I can pretty much guarantee that you will NOT have enough if you are tapping into the main system!!!

You are trying to "add" considerable floor space to a unit that most likely is topped out for your residence already. This will place undue burden on the system to do what it is designed to do potentially resulting in premature failure and other issues that result from over loading.

It would be worth it to make sure the system has the capacity. What I have often seen is that residential units are waay oversized. Oversized units do not work well since their duty cycle will be shortened and they will not de-humidify well. Contractors sometimes try to sell more equipment that the house needs. Sometimes clients think "bigger is better" and upsize the unit without understanding the reality of it all. Rod's book has really useful info on this. Doing the load calc is worth the hour or so with a calculator that it requires. It would be worth it to have a qualified HVAC guy do the calc for your whole house and see if the unit is properly sized. You might get lucky and find there is extra capacity to handle the studio! :yahoo: Beware that what cools the house to a certain degree might not be right for the studio so you might need some dampers or zoned thermostats to deal with that. HVAC is rough. If you want it right, its gonna cost ya.... -ashley

Sorry to hijack the thread but I am curious about what ashley said:

then soffit that in with drywall or you can create a frame around it, fill with rockwool and cover in fabric to create bass trapping as a part of the duct design.

I was wondering if making your own duct in the soffit something like this would act as both a bass trap and supply duct?

eddiemunster666 wrote:

Sorry to hijack the thread but I am curious about what ashley said:

then soffit that in with drywall or you can create a frame around it, fill with rockwool and cover in fabric to create bass trapping as a part of the duct design.

I was wondering if making your own duct in the soffit something like this would act as both a bass trap and supply duct?

Something like this maybe? http://www.johnlsayers.com/phpBB2/viewtopic.php?f=1&t=11506 John

The second one is close. I used metal duct hung in the upper corner of the room. Then you make a frame around that duct and insulate all the gaps between frame and duct. Then either cover it in drywall if you are interested in better isolation or fill them with rockwool and cover in fabric for more trapping. Wish I had a pic.... You can see some on my build thread.... Like this..... http://johnlsayers.com/phpBB2/viewtopic.php?f=2&t=10533&start=30 -ashley

bassman wrote:

I used metal duct hung in the upper corner of the room.

So, your duct is placed on the inside of your wall, not on the outside like I have it on my design. In that case you don't need drywall, it will create a 3rd leaf on your wall, a frame with insulation to damp and absorb should be enough but the real question here is, why do you have your duct inside the room? I thought the practise was to place the ducts on the ceiling or on the outside of our walls creating a soffit with the drywall. Maybe I'm missing something... :? John

Third leaf effect is minimal and what we are trying to do is minimize the effect of the direct penetration of the room. Putting the air duct right at the penetration will leave you with weak points at the edge of the duct hole. Continuing the hard duct inside the room in a drywalled soffit around at least one corner provide better isolation and quieter air handling noise. At least that's the idea. It also allows you to raise a good portion of your ceiling height since most of the duct is incorporated inside the room. You can also bring in the supply and return at the same point and then route them to better locations in the room for optimal air flow and coverage. -ashley

bassman wrote:

Third leaf effect is minimal and what we are trying to do is minimize the effect of the direct penetration of the room.

Maybe I'm not seeing this clearly in my head (a lot of things are going on in there at the moment... :roll: ) but I respectfully disagree with you. The way I see it is that you've cut at least three holes on your walls to get the duct through. One hole at the point of entering the room, one hole for the air to enter the room (or leave the room if it's a return duct) and one hole at the point where the duct exits the room and goes outside or in another room. If that's not direct penetration, then I don't know what it is... If you bend your wall around the duct though, you only need to cut one hole on your wall. It's trickier to make your walls bend at the top but it's better for them since you leave them unscarred... :wink:

bassman wrote:

It also allows you to raise a good portion of your ceiling height since most of the duct is incorporated inside the room.

Your ducts shouldn't determine your ceiling height, unless you place them on the ceiling and you need to increase the air gap between the ceiling and the floor above to fit them there. That's why I thought it was common practise to bend your inner frame at the top corners of the walls/ceiling inside and up (like in my drawing). Cheers, John

There's only two holes.... supply and return. When the duct terminates, a vent goes into the room. I'd have to draw it up to better explain. The pics in the build diary show if fairly well. -ashley

bassman wrote:

There's only two holes.... supply and return. When the duct terminates, a vent goes into the room. I'd have to draw it up to better explain. The pics in the build diary show if fairly well.

Please, draw it if you can because I've seen the pics and I'm more confused now... :? I attached one of your pics from your diary showing a duct which (hopefully) terminates after the duct hole. The red circle marks the spot that the duct went from outside to the inside of the room, hole in the wall so to speak, the blue cirle marks the terminating point of the duct. What's the size of the hole on your wall that the duct uses to enter the room and what's the size of the duct hole that supplies or returns the air? And it's not only the hole on the wall, I believe it's more serious to have the duct in the room alltogether. No matter how many insulation you put around it, it still gonna transmit sound to the next room or outside and outside noise is goona get inside your room through there. I tell you, all I've build in my life is my dog's house (Newfoundland, imagine big... :mrgreen: ) and I really envy you for your build, but this HVAC duct inside the rooms is not something I would do. It just doesn't feel right, if you know what I mean... John

I understand your confusion!! :D That particular duct actually enters the live room space around two other corners that you cannot see. That wall there at the red circle is just a closet for storage and occasional amp isolation. That whole space there under the duct is being used as a bass trap area. The face where the actual duct opening is has been drywalled. The results we have so far are great on the HVAC system. Yes, it might not "feel" right, but then again, so many acoustic building techniques are not intuitive. I don't want to hi-jack this thread with my build but if this info is helpful, then great! -ashley

The original poster seems to have disappeared anyway... go ahead!

Let the battle begin! John's HVAC ------------ Duct Location: In between inner and outer wall Duct Shape: rectangular Duct Material: ?? Duct Size: 7" x 7" Silencer Location: Inside the room enclosed in a soffit Silencer Size: approx. 4" x 4" x 1' 8" (Is this silencer too small for the given duct??) Soffit: Triangle shape filled with insulation enclosed with cloth(including vent) Soffit Size: 2' 8" Horizontal by 2' 8" Vertical Ashley's HVAC -------------- Duct Location: Inside the room enclosed in a rectangular Duct Shape: rectangular Duct Material: metal. (Not sure if it has Duct liner??) Duct Size: ?? Silencer Location: ?? Silencer Size: ?? Soffit: Rectangle shape with a few triangle shapes filled with insulation enclosed with sheet rock. The vent opening is covered with ?? Soffit Size: ?? Could you guys fill in the ?? above and make any corrections? Go ahead and beat up on my design HERE..... YAH!

[quote="eddiemunster666"]Let the battle begin! Ashley's HVAC -------------- Duct Location: Inside the room enclosed in a rectangular soffit Duct Shape: rectangular Duct Material: metal. (Not sure if it has Duct liner??) it is lined Duct Size: ?? depends on the room. that should be calculated based on the load of that room. Ideally, the duct should be the correct size for normal HVAC systems at the entrance to the room. Once inside, you can double the size of the duct to slow the air down before it comes out the vent. You want that air barely puffing out, quiet as a mouse. Silencer Location: ?? don't have any, using the turns and proper design to keep rooms segregated. Silencer Size: ?? none Soffit: Rectangle shape with a few triangle shapes filled with insulation enclosed with sheet rock. The vent opening is covered with ?? a normal vent diffusor, typical commercial one. Soffit Size: ?? just a few inches larger than the duct The triangle shapes were due to cosmetic needs in getting around a door opening in one room. No acoustic purpose. -ashley

eddiemunster666 wrote:

Let the battle begin!

Guys, come on, keep a cool head... :horse: :mrgreen: there isn't a "battle" going on here... bassman has build the damn thing! It works fine for him! I just drew a design to illustrate the way I was thinking about HVAC ducts in relation to their position in the room without, I must admit, a proper study of the subject. However, I'm still confused of how Ashley's duct goes in the room, I'm still waiting for that diagram :P That's the first thing I'm gonna discuss with the wall guys and the HVAC guy. They should work together on this one.

eddiemunster666 wrote:

I don't want to hi-jack this thread with my build but if this info is helpful, then great!

Me too and of course this is helpful stuff! :thu: John

Ashley, are you using any silencers? If yes, where did you mount them? Thanks, Jeff

No silencers. The duct just simply goes through the wall. the pic shows a duct running along the wall. The duct enters in the center of that run. The "T" in the duct effectively doubles the size of the duct by going in two directions. Then you have two outlets that come out of the soffit. Double the volume, half the speed, less noise. Plus the turns that the T provides helps with transmission through the duct and out of the room. -ashley