Let me try to clarify my Truss situation. In doing some research, I think what the studio owner is wanting to use is a truss that's half straight (like a Howe) and half vaulted (like a scissor). Apparently, it could be called a Cathedral Truss, where only a portion of the building has a vaulted ceiling.
With that straightened out, I have a question about Knightfly's suggestion of capping all my rooms and making a real room within a room. In your post you said
with the same on the trusses and a foot between the two masses, you'd be looking at about STC 66-67 with LF TL @ about 38 dB @ 50 hZ
Now, is this drawing I've attached (the red and black one) basically what you mean? Would this same sort of thing work with Cathedral truss I've posted above?
Thanks for your help.
Oh, and about the codes thing...this construction is in the sticks of Kentucky....so not much worries.
Sure, that's EXACTLY what I meant - you just need to make SURE those trusses can handle the weight of extra layers (ask the truss manufacturer's ENGINEER) - codes, schmodes - death is still nature's way of weeding out the fools. This is one area where you need to be SURE... Steve
We'll definitely check out all the load weights and make sure the place isn't going to fall in on itself.
With covering the underside of the truss like that, do you run HVAC above that layer and just come in through openings that are caulked and sealed? Or do you run it in the air space between room ceiling and truss' ceiling?
That would partly depend on how much isolation you need - if you run HVAC ducts within the air space between the two leaves of a containment envelope, you compromise that part of the envelope and actually turn it into a "quad-leaf" situation which will weaken LF isolation. So if you want max isolation, you need to keep the ducts OUTSIDE the m-a-m envelope for as long as possible before penetrating that envelope for the actual insertion/removal points (insertion/removal of AIR, that is) -
Then, when you DO penetrate the leaves, you need a way to mechanically decouple at least the INNER leaf from the ducts - you also need to make sure these ducts each have their own separate run from the air handler to each room, and same with returns.
Each "home run" of each duct needs to have at least 180 degrees of direction change in at least two bends, and each duct needs to be at least TWICE the cross-sectional area (more is better) of typical, so-called "quiet" HOME HVAC installs. Noise created by moving air is roughly equal to the 4th or 5th POWER of air VELOCITY, so slowing it down does GREAT things for getting it quiet.
In addition to that, you do NOT want ANY air SUPPLY registers to enter the room at a point that's anywhere close to being BETWEEN you and any speaker - this creates cold (or warm) air currents that will cause phasing/comb filtering effects due to the different speed of sound in different temperatures of air -
Other than that, I don't know SQUAT about HVAC - for things such as pressure balancing, runtime, etc, Rod Gervais is the man I turn to... Steve
if you run HVAC ducts within the air space between the two leaves of a containment envelope, you compromise that part of the envelope and actually turn it into a "quad-leaf" situation which will weaken LF isolation. So if you want max isolation, you need to keep the ducts OUTSIDE the m-a-m envelope for as long as possible before penetrating that envelope for the actual insertion/removal points (insertion/removal of AIR, that is) -
Is this true with flex ducts, too? Or just regular hard ducts?
Basically ANY intrusion into the space between leaves of a containment will weaken the TL - at that particular point in the construction, even a ROUND duct will somewhat act as a quad-leaf construction, in addition to the fact that the duct itself (unless boxed in with double sheet rock) has no real sound isolation properties, so there is only one leaf of mass between the sound source and the inner duct; so any sound that penetrates the single mass and gets into the duct can now travel the length of the duct to places you'd probably not want it to go.
Running ducts OUTSIDE of both leaves of soundproof walls/ceilings limits the weakening of the envelope to the local area where the duct penetrates both leaves; if the duct is decoupled (soft rubber boot or similar) between inner and outer leaf, and both leaves' penetrations are SEALED well, that's about the best you can do. From there, the minimum 180 degrees of direction change per run, oversizing to slow velocity, etc, make up the rest of your isolation... Steve
Wow. There's SO much to think about in designing and building a room right. It's been pounded into my brain that isolation construction is only as effective as its weakest point, and it seems HVAC is one area where it's especially tricky to do well DIY. I've learned a bit about door seals, and the appropriate thickness/airspace for glass to be as effective as the wall it's going in, etc. But figuring out how to handle HVAC so it doesn't waste the time and money of the rest of the construction is proving to be even more mystifying than I expected. (And I expected VERY mystifying!)
I'm still in the earliest stages of planning, but the more I learn, the less I trust that I'll ever know enough. (Not being defeatist or giving up, just standing nose to nose with reality.)
Sorry to jack the thread for a minute -- back to the Sword!
