Ooops! Problem! Big one!
You cannot use that roof as your outer-leaf...
It is a vented roof, and those are the inlet vents, under the eaves. From the sunlight pouring through the top, there's also clearly a ridge vent up there, to let the air out again.
You cannot seal that up, so therefore that cannot be your outer leaf.
So, what you will have to do is to put drywall directly on the bottom of those trusses, sealed to the wall, and that will be your outer-leaf. Then you will have to build a proper "room-in-a-room" studio below that: four walls and a ceiling.
Yes, you will end up with a 3-leaf roof, but you don't have any options here. You'll need some extra mass on that middle-leaf, and a larger-than-normal gap between that and the actual inner-leaf, and you can still get good isolation like that.
I'm sure this is not what you wanted to hear, but fortunately there is a solution. I've done a few studios like that, and it works out just fine.
- Stuart -
HVAC for Seattle Studio Build
Originally posted at johnlsayers.com, topic 20544.
There's been no shortage of those on this project, haha.Ooops! Problem! Big one!
Exactly right. Airflow in through the eaves and then out through the ridge vent. This was the easiest way to meet code here in Seattle. So much so that in a pre-construction meeting with the city's building department, the inspector told me that he did not want to see gable vents on this structure. He was pretty clear about wanting eave and ridge vents, so that's what we went with. I also briefly explored the notion of a "warm roof" system where the vaulted portion of the structure is completely sealed up and insulated with closed-cell spray foam. The same inspector told me that if there wasn't adequate ventilation up there (despite lots of articles indicating that a fully sealed vaulted ceiling is truly the way to go) he would fail my permit inspections until it was changed. C'est la vie!It is a vented roof, and those are the inlet vents, under the eaves. From the sunlight pouring through the top, there's also clearly a ridge vent up there, to let the air out again.
So from the top down I'd be looking at the following (please correct me if I'm wrong): Asphalt shingles Felt paper Plywood sheathing Scissor trusses Drywall (single layer?) Air gap Drywall/Green Glue/Drywall sandwich Inside-out ceiling framing Is that correct?So, what you will have to do is to put drywall directly on the bottom of those trusses, sealed to the wall, and that will be your outer-leaf. Then you will have to build a proper "room-in-a-room" studio below that: four walls and a ceiling.
To be clear; The inner leaf is the drywall on the backside of the inside-out ceiling. The middle leaf is the drywall on the bottom of the existing trusses. The outer leaf is the roof sheathing, felt paper and asphalt shingles. Is that correct? If that's the case, how much extra mass will I need on the middle leaf? Two layers of drywall? How much larger of a gap are we talking here? I'm concerned about losing too much ceiling height.Yes, you will end up with a 3-leaf roof, but you don't have any options here. You'll need some extra mass on that middle-leaf, and a larger-than-normal gap between that and the actual inner-leaf, and you can still get good isolation like that.
As I mentioned before, this project has been filled with things I didn't want to hear (mostly related to the site work outside the structure and permitting hangups), so I'm fairly numb to it at this point, haha. Just thinking out loud here: Since the ceiling is becoming a larger complication than previously expected (by me at least), would I be better off avoiding the inside-out walls/ceiling and just going back to my original plan of using Whisper Clips and hat channel to decouple the interior from the structure? Would that still run into the same problems with requiring a third leaf on the ceiling?I'm sure this is not what you wanted to hear, but fortunately there is a solution. I've done a few studios like that, and it works out just fine.
OK, so it's a perfectly normal studio build, then... :)There's been no shortage of those on this project, haha.
Wow. Not so nice! And he doesn't even seem to know his own building code, because as far as I'm aware, across the USA that is an acceptable alternative... Oh well...The same inspector told me that if there wasn't adequate ventilation up there (despite lots of articles indicating that a fully sealed vaulted ceiling is truly the way to go) he would fail my permit inspections until it was changed.
Right. But I'd go with more mass on your "middle" leaf, and maybe on your inner-leaf as well, so we can get you a smaller air gap...So from the top down I'd be looking at the following (please correct me if I'm wrong): Asphalt shingles Felt paper Plywood sheathing Scissor trusses Drywall (single layer?) Air gap Drywall/Green Glue/Drywall sandwich Inside-out ceiling framing Is that correct?
Right.To be clear; The inner leaf is the drywall on the backside of the inside-out ceiling. The middle leaf is the drywall on the bottom of the existing trusses. The outer leaf is the roof sheathing, felt paper and asphalt shingles. Is that correct?
Ahhh! Now that's the 64k$ question, now isn't it? :) Yep. The answer is: "How much isolation do you need?" (measured in decibels). . . :cop:If that's the case, how much extra mass will I need on the middle leaf? Two layers of drywall?
Mass and air gap are interchangeable, to a certain extent. With more mass, you can go with less air gap. but first there's a question that needs answering: "How much isolation do you need?" (measured in decibels)How much larger of a gap are we talking here? I'm concerned about losing too much ceiling height.
No.Since the ceiling is becoming a larger complication than previously expected (by me at least), would I be better off ...
Yep. Your wall plan is fine: It's your ceiling that is the problem. - Stuart -Would that still run into the same problems with requiring a third leaf on the ceiling?
I'll get back to you with specific decibel requirements for isolation. Currently on my phone and need to do that from my desktop.
In the meantime:
Would I be able to move back to a two leaf system if, after I pass inspection, I pull out the newly installed insulation, block and air seal all of the existing vents and then reinsulate using a "no air flow/warm roof" method? Would that even be achievable?
Precisely!OK, so it's a perfectly normal studio build, then... :)
I've had to make trips to the Seattle DPD and argue with them during the site development phase of the project. They often argue things because of how they feel rather than simply enforcing code. I overturned one such decision. I had a surveyor I contracted to do a property line delineation (to locate the studio building on my property) tell me "The Seattle DPD is a black hole where good projects go to die." No shortage of love loss there, haha.Wow. Not so nice! And he doesn't even seem to know his own building code, because as far as I'm aware, across the USA that is an acceptable alternative... Oh well...
Let me set the scene for you: The loudest piece of equipment ever operating inside the space at any given time will live drums. Since there's only one room where sounds will be generated (mixing and tracking occur in the same space due to size limitations), I'm not worried about bleed in the rest of the studio. There's a storage vestibule, but that's inconsequential to this discussion. The building is located against an alley. There's a neighbor's house on the other side of the alley that is roughly 20' from the western wall of my studio building to the eastern wall of his house with a wooden fence in between. There are cars that go up and down that alley periodically, but it's not a major thoroughfare. So with all of that in mind I would say that a drummer with a light touch will be in the 90-100db range, whereas a drummer that's an absolute basher might be well above that. 105db? 110db? 120db? I wouldn't be surprised if it were possible to get that high, but I suspect it will commonly peak out around 100-105db. The bass drum will likely be the sound that penetrates the isolation perimeter most readily simply due to its lower fundamental frequency than the rest of the kit. If I could get the resultant sound outside the studio to be non-obnoxious to my nearest neighbor I'd consider the isolation a success. If I could get everything down to the 50-60db range I would be happy, although more than that would obviously be better. I'm using the db chart on the Sound Proofing Company's website to make relative comparisons to "real world" sounds and their apparent loudness (db). I have a good relationship with all of my neighbors, and don't plan on tracking loud instruments late at night, so the isolation concerns are somewhat mitigated socially. I'm definitely attempting to build such that I can maximize sound isolation while preserving as much internal working space as possible. A better end product is more important to me than cost savings. In terms of isolating external sounds from getting into the studio is concerned: The loudest exterior sound will be a car driving down the alley. It will be around 5' from the exterior wall of the structure, but its a dead end alley with only two homes at the end, so the cars are typically traveling very slow (~5mph) and none of them are large trucks or anything noisy like a motorcycle. If I can keep that relatively quite noise from getting into the studio and ruining a perfectly good take I'll be very happy. SPC has an average street at 70db, so I'd estimate this to be in the 40-50db range.The answer is: "How much isolation do you need?" (measured in decibels). . . :cop:
Stupid ceiling! Haha Reiterating my question from earlier: Would I be able to move back to a two leaf ceiling if, after I pass inspection and am done with the city, I pull out the newly installed insulation, block and air seal all of the existing vents and then reinsulate using a "no air flow/warm roof" method? I could physically block the vents with thin strips of lumber or metal flashing, caulking, and then shoot the whole thing with a closed-cell spray foam insulation. Would that be worth my time and money given my stated goals above? Or instead, in your estimation, will I be able to achieve my desired level of isolation or better despite the three leaf ceiling? Thanks once again Stuart!Your wall plan is fine: It's your ceiling that is the problem.
Giving this a bump.
General project update: I've been hit with some delays recently, so I'm still in the process of insulating the exterior walls such that they'll pass inspection with the City of Seattle. I'm hoping to have that wrapped up this weekend or over the course of the following week.
I would not do that, no. It's not worth the hassle. Just build it as a 3-leaf roof, while taking the necessary precautions.Would I be able to move back to a two leaf ceiling if, after I pass inspection and am done with the city, I pull out the newly installed insulation, block and air seal all of the existing vents and then reinsulate using a "no air flow/warm roof" method?
Yep! you sure can. As long as it is built decently, it will work fine. - Stuart -in your estimation, will I be able to achieve my desired level of isolation or better despite the three leaf ceiling?
I assumed as much, but wanted to get your opinion before I started putting up the "middle" leaf.I would not do that, no. It's not worth the hassle. Just build it as a 3-leaf roof, while taking the necessary precautions.
I've been doing all of the work, and plan to continue doing so (minus the electrical, vacuum test, line purging and charging of the mini split system, and sound door install). Since I'm doing the work I can take my time, do it right, and not worry about cost overruns due to extended timelines. Thanks again Stuart!Yep! you sure can. As long as it is built decently, it will work fine.