Prepping the basement for drywall

[Velvet Elvis]

Pictures - Set 1 of 4

Ok... Here are some pictures to better explain some things:

This first one shows the layout/plan of the studio portion. I am also doing a home theater at the same time, so some of the following pictures will show the theater portion as well.

The next picture shows the existing portion of the basement, entering into the area I am working on (theater and studio)

This next picture is in the theater and shows one of the HVAC vents I was talking about. I can see how I'd caulk around the boot, but it seems like sound would leak left and right out of the actual duct. I AM planning on changing this duct over to flex, to break the metal to metal connection.

This picture shows the theater looking back toward the doorway to the existing part of the basement. The wall to the right is the outside foundation wall. You can also see a portion of the soffit with the OSB to the left that I was mentioning.

This is a picture of the vent boot and the sill plate area that I was mentioning as well.

(more to come in additional posts)

Jim

 

[Velvet Elvis]

Pictures - Set 2 of 4

This picture shows the soffit area in the theater. You can see two HVAC feeds. One is to the room and the other is to a room upstairs. Both run back to the house's central trunk.

You'll also notice recessed lighting. This is ONLY in the theater and they are air-tight fixtures. They will be caulked and puttied just like any other electrical fixture.

This picture shows the entrance to the studio area from the theater. This opening is the ONLY opening to get into the studio. All 4 walls are otherwise concrete foundation in the studio area.

This picture is standing in the entrance to the studio. You can see the drum booth window to the right. Notice two separate walls between the control room and the drum room. You will also see and HVAC feed to the upstairs on the left hand side and a feed to the studio hanging from the center. Both go back to a trunk just above the camera in the soffit. ONLY feeds come off this central branch area. Returns from the studio actually run all the way back to the furnace via flex.

This picture shows the HVAC feed to the upstairs in the studio ceiling. It also shows an area of the sill plate (to the left) that is near impossible to treat. They have two I-beams sitting inches apart from the actual construction of the house. The outer left I-beam is the outside of the foundation wall in this area.

(more to come in additional posts)

Jim

 

[Velvet Elvis]

Pictures - Set 3 of 4

This is a closer look at the soffit area in the studio. It was PACKED with stuff from the construction of the house, so it is impossible to treat the sill area behind it. This however faced up against the concrete slab of the garage floor (at sill level). You can see the studio HVAC feed on the left and an upstairs feed on the right.

This is the corner above the drum room doorway. You can see the double wall construction. You will also notice that the walls are nailed into the I-beam above (which is partially why all walls need RC). This is the only real wall set that was constructed. All the others were existing in the house and already touched the I-beams (the outer walls).

This is another picture of the sill area to be treated in the studio. You can see the existing wall (built by the original contractor as required in my city). Above the wall is insulation which is tucked in the cavity between I-beams. There is outer sheathing beyond the insulation and then the siding etc (this is an outer wall).

This shows the drum room ceiling. The HVAC on the left is a feed to the upstairs and goes back to the trunk at the other end of the room in the soffit. The flex on the right is the feed for the drum room.

(more to come in additional posts)

Jim

 

[Velvet Elvis]

Pictures - Set 4 of 4

These first two pictures show holes in the sub floor above the drum room that I need to repair. My plan is to cut OSB to fit the area, cut out the hole for the drain etc then cut that board in half (so I can fit it around the drain). Screw it in place and caulk all edges, seams, and pipes etc.

This picture shows the soffit at the back of the studio. The HVAC trunk at the far back is shared with upstairs and the studio, but each room takes its own feed from that trunk. There are also various pipes etc for fresh air and venting for the furnace. You can also clearly see the OSB drop around the soffit. This is the area I was wondering about NOT using RC on in order to avoid a three leaf type system.

This is a view of the same soffit from standing back in the studio a ways. The door on the right exits out into the theater area.

This last picture shows the soffit area looking from the drum room out through the control room into the theater area.

Does that help you guys visualize what I am dealing with a little better?

Jim

 

[RICK FITZPATRICK]

Does that help you guys visualize what I am dealing with a little better?

. Hi Jim. Yea. Hey, that plan sure looks familiar.

First off Jim, I haven't got time this morning to reveiw each of the pictures and read the whole post. Got Monday morning "honey-do's" So
I think I'll wait to see if Rod has anything to say about the ducting issues before I make a fool of myself again He really is the expert here.

Although I'm a litte confused about your use of the word "trunk". Is that the same thing as a plenum? Or a distruibution box? I always thought of a HVAC "trunk" as a MAIN duct leading from a plenum or supply box that has a larger diameter than the rest of the ducts which are fed from this main duct. I guess what I am trying to visualize, which is STILL a little confusing even though you provided pictures, is whether or not, each of the supply and return ducts to the studio are TOTALLY seperated from the ducting to the areas above. In other words, do each of these ducts to the studio feed ANY ducting to upstairs, or are they all seperate ducts leading back to a main plenum? At first glance, its hard to say. Maybe you answered it already but like I said...no time at the moment.

If any of these ducts share a common duct "TRUNK", maybe something along these lines is needed. Hard to say at this moment though.
http://www.acousticalsurfaces.com/hvac/duct_silen.htm?d=26

Personally, maybe if you drew an overlay of the plan showing all these ducts and where they feed from or tie together, it might enlighten us. Well, outta time now. Talk later.
fitZ

 

[Velvet Elvis]

Rick,

Yeah... excuse my terminology... I'm just a "regular Joe" and call it whatever it looks like You're lucky I'm not saying "the round thing-a-ma-jig".

Here's a drawing of the HVAC paths (see below).

The feeds and returns to the studio area are all flex ducting and have some bends and turns to them.

The feeds and returns to the upstairs are all standard HVAC ducting, but could easily be replaced with flex to remove any coupling of the metal boot to the trunk etc.

As you can see, ALL of the HVAC for this end of the house had to fit through that doorway opening. The reason being is that all the other walls are concrete and this is the only opening to the area. It allowed us room to put a separate return for the studio, but not a separate feed.

Jim

 

[RICK FITZPATRICK]

Yeah... excuse my terminology...

Howdy. Actually, to my way of thinking, your "terminology" was dead on. Hey, now that plan REALLY helps visualize whats going on. Thanks. This type of info is what I've been trying to pry out of people for years here. It really does make a difference when you are trying to help people with correct solutions. And believe me, when it comes to HVAC, I'm really pretty much of a dunce. But maybe Rod will see that and i'm sure it'll help him. If he doesn't I'm sure we can get some answers to the "flanking" path issue. One other thing, I think there is some kind of "decoupling" termination hardware for ducts at the registers too. Don't want all that work in RC in vain.

One other thing. I know you have built a room in a room, but with no "decoupled sway brackets" where the top plates meet the I-beam joists, to my way of thinking, it looks like you need to use RC on EVERYTHING. As to the duct soffit covered with OSB, you could use it there too, but you'd have to cut some fairly large holes(like with a 5" or so holesaw) in the OSB to vent the airgap between the drywall and the OSB. I THINK. Rod? With 2 layers of 5/8 DW on RC over the OSB, I think it would be fine, butI'd sure like Rod to chime in on this as well.
Theres a ton of details for offseting the DW joints at ceiling/wall intersections, overlaping the DW joints in layers, and allowing for caulking clearance at door jambs and the floor as well. Attention to DW detailing prior to fastening as well as critical STORYBOARD installation of the RC itself so fastening the DW later doesn't short out to a stud or something. Also, placement of the RC at top and bottom locations has some offset details as
well, which Rod knows better than I.

Gotta go now. Later.
fitZ

Ps... Looking good Jim.

 

[Velvet Elvis]

Rick,

Glad to provide my pretty little drawings

Yes, I am well aware of the drywall staggering/corners etc stuff. Cool.

So... are you saying that the HVAC might be OK as is? (given the flex ducting and making sure I don't short the RC work when I install the registers?

Also... GREAT idea on the soffit OSB... I hadn't thought of drilling holes in it!

Yes, I was planning on RC for EVERYTHING. All walls and the ceiling.

Thanks again. You're slowly, but surely, making me feel that I'm not wasting my time and might actually have a usable product when done!

Jim

 

[Velvet Elvis]

One more note...

I called the Acoustical Surfaces place... and there is no way I can afford duct silencers. They are $700 EACH

However, they said that they make a 1/2 inch, 1 inch and 2 inch cotton acoustical lining for HVAC ducts. They suggest oversizing the duct work, and then lining 4 to 8 feet of the duct with this material. If I can add a bend or two in the duct, it helps even more.

This stuff is VERY reasonable (25ft x 48 inch wide roll of 1 inch for $200 shipped).

Does that sound like a possibility for helping?

Thanks,
Jim

 

[Velvet Elvis]

You know, I started thinking about my HVAC situation... since all the ducts run back to the main trunk (as shown in the drawing), that means that sound has to make two 90 degree turns to enter into the other ducts... that should help matters, right?

IE - for sound to travel down the HVAC vent in the studio and then enter into the HVAC vent for the floor above, it would have to make a 90 degree turn out of the studio duct into the main trunk and then another 90 degree turn from the main trunk into the duct for the floor above.

This is of course assuming that the ducting itself isn't leaking sound (which I would assume needs to be a concern.

Thoughts?

Jim

 

[RICK FITZPATRICK]

IE - for sound to travel down the HVAC vent in the studio and then enter into the HVAC vent for the floor above, it would have to make a 90 degree turn out of the studio duct into the main trunk and then another 90 degree turn from the main trunk into the duct for the floor above.

Jim, I'm no acoustic expert, but I believe LF doesn't see it that way. Think "vector pressure". Rod, please correct me if I'm wrong here. Jim, sound is not what you think it is in this context. In fact, its not "sound" untill your brain interprets the vibrations against your ear drum, which is in effect...pressure differences. Normal household sound probably wouldn't have a chance propogating up these ducts under normal conditions. But think IMPACT sounds from a bass drum or LF notes from a bass at 100db. Rod?
fitZ

 

[RICK FITZPATRICK]

Oh, btw, I'm working on it.
fitZ

 

[Velvet Elvis]

Anxiously awaiting, Rick... looks cool

Jim

 

[Velvet Elvis]

By the way, a friend of mine that works in the HVAC industry got me hooked up with a local supply house that carries duct board, JM duct liner and flex conduit with a R value of 8 (instead of the typical 4.6).

Prices are decent, too!!

So... I'm ready to put this together the right way once I know what you and Rod suggest for my situation.

Thanks,
Jim

 

[RICK FITZPATRICK]

Working on it jim. Figuring out a "silencer" is NOT easy. Lots of stuff to read. I'll get there though. Hang in there.
fitZ

 

[Rod Gervais]

Jim, I'm no acoustic expert, but I believe LF doesn't see it that way. Think "vector pressure". Rod, please correct me if I'm wrong here. Jim, sound is not what you think it is in this context. In fact, its not "sound" untill your brain interprets the vibrations against your ear drum, which is in effect...pressure differences. Normal household sound probably wouldn't have a chance propogating up these ducts under normal conditions. But think IMPACT sounds from a bass drum or LF notes from a bass at 100db. Rod?
fitZ

You got it Rick.

The only reason we concern ourselves with baffles is for things like motor noise - i.e.: fan noise - as well as air noise itself...... but those are higher mid and high frequency noise which is more directional whereas LF transmissions are more radiant.

But the baffles are not meant to act as an extension of the studio isolation unless some real care is taken in their design - and even then they don't handle LF real well.......

This is why I generally design totally seperate systems for HVAC whenever possible - and then carry the seperating wall assemblies to the underside of what's above to maintain the room seperations even above the ceiling (just to deal with what might escape the ductwork itself).

Sincerely,

Rod

 

[Velvet Elvis]

Rod,

So, in your opinion - given that a separate system isn't really an option for me - what would you do (within reason)?

Is it worth building a baffle, or will using flex and/or duct board be about as good as it is going to get?

Thanks for your expertise (both of you guys!)

Jim

 

[RICK FITZPATRICK]

But the baffles are not meant to act as an extension of the studio isolation unless some real care is taken in their design - and even then they don't handle LF real well.......

Rod, I looked at everything I could find within 2 hours this morning, mainly to discover the principles by which propogation of sound BACK through the ducts from the studio could be attenuated. Frankly, I coulnm't find a THING! Yea, all kinds of things to do with sound propogating from fans and turbulance in the ducts themselves. But jesssus, I couldn't find a thing. No wonder Everest described seperate systems.

I'm a little confused by the terminology..."baffles"...Please explain. I mean, I looked at silencers, splitters and tons of other things and I think I understand your meaning but that doesn't mean diddly squat. Are you refering to the inner perforated plates of silencers?

This is why I generally design totally seperate systems for HVAC whenever possible - and then carry the seperating wall assemblies to the underside of what's above to maintain the room seperations even above the ceiling (just to deal with what might escape the ductwork itself).

on second thought,, I think I see the light. Just what I thought all along.....omg. Jim....maybe its time to make the best of what you have.

I was going to suggest adding a layer or two of DW to the underside of the floor between the joists. But now, I don't even know if its worth it. I think we've discovered the weak link Jim. No sence in trying to improve it if its impossible.
Well, thats all I have to offer now. Good luck Jim.
fitZ

 

[Velvet Elvis]

So I guess my question is, what IS the best that can be done with the situation?

I'm confused... help me Obi-Wan.

Jim

 

[RICK FITZPATRICK]

what IS the best that can be done with the situation?

Frankly Jim, personally I don't really know. I only tried to point out what I saw as a possible flaw in the OVERALL TL scheme. Unfortunately, because ducting penetrates the TL envelope, HVAC has always been the tough one, especially in basements where the same ducting connects upper and lower areas. Hence a direct flanking path. Even with a couple of 90 degree turns, high SPL LF and impact noise is a BITCH to attenuate, even for experts as Rod points out. Hence the double systems in pro studios.

Jim, I'm certainly no expert in this area, and I hate to be a naysayer, but like I said, a SERIOUS re-evaluation of the relevance of RC may be in order. Why spend all that time and money on something that is already compromised...ie..WEAK LINK SYNDROME. Its like putting a Door with a TL rated at 56, in a wall assembly rated at 40(just an example).

Maybe Rod has a solution, but other than some sort of "baffle" plenum, and replacing the flex ducts with LINED flex ducting and POSSIBLY, replacing the existing upper floor registers/grills with a type that can be closed AIRTIGHT
...I don't have anything to offer. Even then, I don't have the expertise to design this so-called "baffle" box. Sorry. Well, thats all I have time for now. Good luck Jim.
fitZ