To breathe or not to breathe — Cutting a hole in my house for fresh air ventilation into the studio

Part 19— Designing and building a DIY home recording studio.

17 min readMay 20, 2019

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The whole story — part 1, part 2, part 3, part 4, part 5, part 6, part 7, part 8, part 9, part 10, part 11, part 12, part 13, part 14, part 15, part 16, part 17, part 18, part 19, part 20, part 21, part 22, part 23, part 24, part 25

I’ve got lots of pictures for you this time.

Needing fresh air

You first need to know that in order for the room to be “soundproofed” I’m building the studio to be as completely air tight as I can possibly make it.

Having no gaps or cracks in the construction means no sound “flanking” through or around otherwise soundproof walls. Think “water tight”. If the room is water tight, then it will be air tight. I know the room won’t ultimately be able to be 100% air tight, but it’s going to be as air tight as I can possibly manage in real life.

Building the studio to be air tight is fantastic, except for one thing; without having a way for fresh air to enter the room, the air will eventually become stagnant and stale.

This DIY studio project has proven to be quite a tough undertaking, but I’m feeling such a big sense of accomplishment. I can’t really express how educational this entire process has been for me. I’m trying to keep my mind focused on the future end result. And hey, this big thumbs up means I still have a thumb on my left hand!

Because the double glazed window will also be sealed (I’m only leaving it there to let in natural light), I need some way of bringing in fresh air. This means cutting a hole in the wall to let in fresh in — which also sounds like a horrible idea, because now I’m intentionally punching a big hole in a wall that needs to be completely closed in order to remain soundproof.

An example from Ted White at Soundproofingcompany.com of a joist muffler — taken from his installation manual he sent me.

Looking for solutions, my consultant Ted White at Soundproofingcompany.com introduced me to something called a joist muffler. (ps, Although I mention him several times, I’m not in any way affiliated with Ted or the company he works for. I just happen to be a big fan of who they are and what they do, enough to spend a bunch of money with them on soundproofing solutions. =-)

The muffler Ted mentioned refers to a joist cavity that has been soundproofed but has a flex duct running through providing fresh air supply.

Basically, the joist is layered with drywall and Green Glue, sealed and filled with R-13 fiberglass which surrounds a flex duct which passes the air through from the outside into the studio. The muffler traps sound waves as they escape the flex duct which intentionally snakes through the joist cavity in a way that makes sound waves leave the duct as often as possible.

By the way, running the air duct in a non-tight/non-straight manner is normally the worst thing you can do for air flow efficiency. But in this case, the whole point is to make the sound have the most difficult time possible getting from one end to the other. All these bends cause the sound pressure to escape the duct repeatedly and get trapped repeatedly as it gets absorbed into the fiberglass particles which begin to vibrate. Once sound pressure converts into mechanical vibration/heat, it’s no longer sound! Just like a car muffler, the whole goal here is to reduce the noise on one end as much as possible before it reaches the other end. The cool thing here is the muffler works equally well in both directions.

Incidentally, I found out when you buy something from Ted (at Soundproofingcompany.com), he actually sends several build/installation manuals on a wide variety of things which provide step by step build instructions. Here’s a little snippet from the multi-page instructions on the muffler being used in conjunction with a suspended hat channel ceiling like I’m using.

a snippet out of a very comprehensive manual from Ted White at SoundProofingCompany.com on how to build a joist muffler system and chimney.

I will let you know upfront that Ted said building a joist muffler is very time consuming, and definitely not cheap. In fact, Ted actually spent about 10 minutes explaining why he suggested I don’t build the muffler. He said it definitely works, but the time and expense will seem very disproportionate.

Rather than recommending the muffler, he suggested I build a dead vent instead. It’s basically a vertical joist muffler that rather than living in the ceiling, it’s in the room with me. The main difference is it is easier to build because it’s not building something up above my head and having to deal with all the other plumbing and wiring running up in the ceiling joists that would be getting in the way. This is an example of one of the great pictures out of the very detailed step-by-step dead vent build instructions from Ted.

Skipping the muffler in the ceiling and just building the dead vent is the plan! I’m going to just build the dead vent in the corner.

Ooops!

So I had a big learning opportunity that I’ll share with you.

I wanted to test fit the flex duct so I ran the flex duct up into the joist directly above the concrete foundation wall where it seemed it would work best. It’s totally hidden and out of the way there which is great. The other end of the flex duct will also drop down nicely into the deadvent which I’m going to build in the front left corner of the studio.

Now, I’m just trying to figure out a way to hide the deadvent in the corner without having this huge awkward deadvent taking up a bunch of space in the corner. After thinking through some options, I realized I could simply creatively make it part of the corner which was already going to be used for a corner bass trap. So, now instead of having a bass trap in both front corners, the corner on the left will actually be a dead vent that is just finished off on the face of it (with cloth covered rigid fiberglass) to look just like the corner bass trap I’ll have in the right corner.

After carefully thinking through what I would need for the corner (to accommodate the dead vent), I communicated it all to Wes and he quickly came up with a fantastic way to frame it all up. A few minutes later the corner was framed and ready to go! It looked like it was going to work great. That is until I saw my plan in real life and realized I had made a big error (sorry Wes).

BIG NO NO! This would have been a cool way to build the “deadvent” in the corner but unfortunately I realized it wasn’t going to work both ways. Meaning, when it was all built, it would have stopped sound from outside and upstairs from getting ino the studio, but sound from the studio would have traveled up the duct work and leaked into the joist cavity — pumping sound into the bedroom above me. I’m going to have to tear this down, reframe the corner and then rebuild this corner deadvent after the double drywall is up and the floor is in. That way I can have the deadvent feeding right into the ceiling muffler I’m building without any chance of leaking sound into the joist cavity.

What I had asked for was only going to stop sound trying to come into the studio. I need to block sound trying to leave the studio as well and what I asked Wes to build won’t do both. Unfortunately I realized my mistake about 30 minutes too late. I painfully realized the beautiful corner solution Wes had framed just moments earlier would have to come down. SORRY WES!

In order for the dead vent to really work, it has to have double layer sheetrock with Green Glue on ALL sides (not just the face of it), and have all seams and corners and edges sealed to be airtight.

If you look at the picture above, the back and sides (behind the corner) are completely open to the ceiling above. There would be nothing to stop studio sound from entering the dead vent (from the studio side) and going right up and through the flex duct walls directly to any opening or nail holes in the subfloor up to the bedroom above. Big fail on my part.

So…

To correct things, I’m going to have to cut out the angled corner and frame in a 90° corner afterall. And it looks like I get to build this muffler after all that Ted spoke so fondly about.

Red lines represent the joist muffler I’ll be building that soundproofs the joist. Yellow represents the air gap above the top layer of drywall resulting from using hat channel. If any sound gets into this space, it will travel freely to all the joists in the ceiling cavity area and easily into the bedroom above.

The hat chanel I’m going to be using intentionally creates a couple inches of gap below the bottom of the joist so the ceiling sheetrock is decoupled from the joists. But, the flex duct leaving the muffler is going to be completely exposed for those couple inches. I have to somehow connect the flex duct (leaving the bottom of the joist muffler) to the deadvent without ANY sound leaking into the hat channel gap above the ceiling sheetrock. I’m hoping that makes sense.

The gap caused by the hat channel poses a problem because the flex duct leaving the joist muffler will be completely exposed in this gap and sound will escape the flex duct and get into the bedroom above.

Ted gave me directions for a really cool solution. It’s for a “chimney” which is basically a very dense “spacer” barrier that fits perfectly between the top layer of ceiling sheetrock and the bottom of the joist muffler. It is attached to the bottom of the joist muffler and the ceiling sheetrock layer comes up to meet it. Acoustic caulk is applied to the bottom of the chimney so when the ceiling sheetrock is installed it presses up against the caulk and creates an airtight barrier between the top of the sheet rock and bottom of the muffler. Problem solved!

From Ted White at www.soundproofingcompany.com

But for now, time, to rebuild the corner and cut a ventilation hole in the side of my home.

Cutting a hole in the side of my home

This is a bizarre experience and not something I’m wanting to have to do too many times. To minimize the holes in the side of the house I realized I could possibly use the area with the old furnace flue intake/exhaust conduit holes.

The original intake/exhaust flue for the furnace ran above the studio window and had to move anyway.

Not really knowing what I was going to do to patch the holes on the side of the house, I just left these for later.

Now that the furnace flue is going out the back of the house instead. Maybe instead of plugging up the conduits and just abandoning them, I could possibly use the same area for the fresh air vent intake instead.

I’m hoping the vent cover can go right where the PCV pipes are that I’ve abandoned — now that the furnace intake and exhaust flue are running out the back of the house instead.

Looks like it IS going to work out to put the fresh air intake here. Cutting off the ends inside and outside so I can remove the pipes

I used a concrete drill bit to sort of perforate the stucco layer.

The concrete bit didn’t even try to dig into the wood but this 1" corkscrew style bit pulled itself right in and through.

As luck would have it, at the bottom of the hole there is a nice thick piece of metal sheeting that is in the way. It must be because of how low this hole is to where the wall meets the foundation wall. Maybe it is something that helps hold the materials together or maybe it simply protects the bottom of the stucco wall area. I bet one day I’ll know the answer to that. In the meantime, the reciprocating saw took care of it, but I almost completely used up a new metal cutting blade. This stuff was really tough. I finally got the nice round shape I needed for the vent on the duct to fit through.

I’m pleased with how the exterior turned out. AND, I’m glad to be drawing in nice fresh air from this point, rather than pushing out furnace exhaust over a window that if open would potentially bring the exhaust fumes inside the home. I still don’t know how that passed inspection originally, OR when we bought the home last year. Anyway, problem solved and operation install air duct on the outside in place of the flue is complete! It’s really nice this worked out to do it this way so I don’t have to patch the outside of the stucco.

Now it’s time to get the fresh air into a joist muffler.

Step 1 — zip tie the inner flex duct to the elbow

Step 2 — Seal the elbow and flex duct together. Foil taping over the zip tie protect the zip tie connection and tapes the elbow and the flex duct together with a nice airtight seal.

Step 3 — cover it all up and zip tie the insulation to the elbow as a safety, plus it looks nicer this way.

Instead of using the joist cavity above the foundation wall, I have to use a joist that will accommodate the muffler system where I can completely soundproof the cavity. As luck would have it, there is a joist with a nice, long 16 foot run ending right where I need it to at the front left corner of the studio. At first glance it is going to work perfectly. But in order to get into that joist, I will first have to pass the fresh air intake through the side of the joist wall I can’t use and then into another joist. I’m using a 6" ducts — which is a big hole to cut into a joist wall — so I’m reinforcing and strengthening the joist webbing (walls of the joist) on either side of where I’m cutting the hole. The original plumbers didn’t have any issues cutting huge holes in the webbing, but per the manufacturer, anything over 3" is not recommended. Over engineering is better safe than sorry here so I’m going to go ahead and cut the hole, but reinforce!

So far so good. I’m just hoping I can line the holes up properly. As you can see, I was second guessing myself on the location of the hole in the joist. I think I’ve got the right location now.

I get to take advantage of this entire joist cavity. There are a few obstacles I need to work around, but I think I can make it work.

Lots and lots and lots of gaps to fill. It’s really a lot of hours which makes it really hard to see any progress sometimes, but all the work to seal all these gaps and holes up will really pay off for me in the end.

One down

Lining the joist with layers of drywall and Green Glue

Attaching the last piece of drywall to the joist muffler inner wall!

It worked perfectly to cut a hole for the vent cover where the PVC pipes were that I was abandoning and trying to figure out how to seal up. Well, now I don’t have to seal them up, because they are cut out and gone!

Mass-loading the joist for the muffler. It’s getting pretty dense. One layer of 5/8" drywall with Green Glue on the outerwall of the joist and two layers on the inside of the joist cavity.

Almost done! Now I just have to tape the remaining joints to seal any air leaks.

Some type of tar based sound deadening material with adhesive on the back. Mostly used to line trunks of cars so they don’t vibrate when there is an awesome subwoofer booming away. Right now it’s going to be used to wrap the shower drain in the joist to reduce the chance of sound leaking from the ventilation duct into the PVC and also reduce the water draining noise from getting into the ventilation duct. I highly doubt I’d have issues with either, but I’m not going to go through all the work and cost of the joist muffler and then skimp out on a possible weak link item.

This stuff actually molds around the PVC quite well. I’m double wrapping it all. It really formed a nice seal around the pipe/drywall area.

The circled area is a section of drywall I had to remove because the double inner wall was just slightly too thick for the flex duct to pass by the drain pipe. I’m really not worried at all about any sound transferring here through this little cut out because I’ve made up for it by adding the mass back by adding a layer of drywall on the other side of the joist. I’m just really glad the duct was able to pass by without being squeezed out of shape or restricting the air flow — which was my main concern and the reason for notching out the side wall a little.

All Taped up and sealed. Time to run the flex duct and then insulate around it.

Pulling the kraft paper backing of the insulation. Totally unneeded.

Cutting it up into more manageable pieces.

wrapped the water line with the sound block material.

Time to cover it all up!

Ripping down 2x4" into strips of wood that I can install along the bottom of the joist (per the first picture of this post), so I can attach the lid layers on the bottom to close/seal the muffler.

Lot’s of absorption ready to absorb!

The wood rails are installed on either side. It’s time to cover up with a little more insulation and then put the lid layers on.

LOTS of fresh air coming through the duct right now! I’ve been working up a sweat for a while, so It feels FANTASTIC.

First layer is all closed up. time for the cap. EXCEPT there is a problem. The sidewall layers are hanging down too long which won’t let the bottom lid lay flat against the drywall layer. I have to trim them up a bit but I’m not really sure the best way to go about that. I’m exhausted and just wanting to be done with the lid layers at this point.

It must have been pure inspiration to use the saw to level these layers with the first lid.

You can see on the left of the picture that the double layers of drywall on the side are now becoming even with the drywall bottom lid (that the saw is pressed up against). This ended up taking a lot more effort than I thought it would, but it worked GREAT! Time to attach the bottom wood lid layer.

Measuring to cut a hole for the flex duct to come through the bottom lid layer.

I actually messed up on this first one. I really did measure twice. I need some sleep I think. =-)

This is looking better.

Yep, it turned out right. Now, Green Glue and attaching it.

On a roll.

Time to finish the bottom lid layer. But, I’m i’m spent and needing some help. My son Adam is at the right place at the right time!

Adam helping me attach the remainder of the bottom layer of the joist muffler.

Lot’s of tools happening right now to make things go more smoothly.

I was too tired to remember to take a picture of the fully covered joist muffler. I’ll take a picture of it next time I’m down there. But, for now, it’s DONE! Thanks Adam!

PS, Ted White was right about the joist muffler taking a lot of time to build (hours upon hours). Also about it costing some money in materials to build — Lots of screws, almost 4 sheets of 5/8" drywall, several speed loads of Green Glue, several bats of R-13 insulation, 4'x8' 3/4" MDF, flex duct (12") and elbow joints/tape, a couple sawzall blades and the exterior vent cover, BUT, it WILL be totally worth it at the end. (but, I probably will do whatever I can to not have to build another in the future. =-)