A few building questions for my specific situation

Thanks, Steve! I appreciate it. On another note, would someone be able to refresh my memory on how many air-changes per hour generally need to happen in a basement room-within-a-room scenario? I know code is usually where to look for that type of info, but I seem to remember someone mentioning 'eleven' on here at some point as a rule of thumb. I searched and couldn't find anything. Once you know how many room-changes are needed per hour, how do you then use that knowledge to calculate the right HVAC gear you'll need? In general terms, I'm thinking a line in for fresh air, a line out for stale air and a mini-split, but I'll obviously need to figure out the diameter / length of ducts, fan-type, etc. The room will be mainly for me practicing drums, but I'd like to be able to comfortably provide for a few dudes playing amplified rock-band instruments in there from time to time. I realize I'm jumping around with questions, but after all this window talk, I just remembered I need to verify how big my ducts will need to be in order to preserve some window space for them! I'll obviously wanna do silencer boxes, so I'll need to do account for those in determining the length of my ductwork, as well. Thanks very much again, guys.

Just wanted to bump this bad boy to see if anyone could help me with the query above.

Guys - Forgive the poor iPhone pic. Can I get a quick consult from someone who knows what's up with windows, if possible? If I were to build my own 2x8 frames into the rough masonry openings seen below, how would I deal with the voids created along the sides, bottoms, and (especially) the corners where the 2x8s won't butt up all the way against the blocks? Prior to running into this problem I had planned on using butyl caulk along the entire perimeter, but now am wondering if I shouldn't use that pink / yellow foam crap. It seems like if I use caulk I'd be caulking for days, and I don't know that that'd even properly insulate gaps this wide, would it? Anyone have a strong perspective on this one? Thanks so much!

n1ck wrote:

Forgive the poor iPhone pic.

doesn't look like the photo uploaded mate. It would be helpful to see what you're seeing if you can manage it.

n1ck wrote:

Prior to running into this problem I had planned on using butyl caulk along the entire perimeter, but now am wondering if I shouldn't use that pink / yellow foam crap. It seems like if I use caulk I'd be caulking for days, and I don't know that that'd even properly insulate gaps this wide, would it?

It may be possible to use expanding foam in middle of the cavity to add a very slight redundancy for your outer seals, but use an acoustic caulk for the outer seal between the timber frame and the masonry. If it's not sealed air tight then it won't perform to the level you require.......and yes, you will caulk for days. That's probably rule number four in studio builds: Thou shalt use an obscene amount of acoustic caulk. Caulk everything. Seal everything. You only get one real chance to do it right without having to pull things apart to re-do them. The technique which is mostly used is to use backer rod to fill the cavity so you can run a nice bead of sealant against it. all the best, Steve

Thanks, Steve. Not quite sure what happened there with the pic. I tried to attach it at the bottom this time. Can you see it? I guess my concern is: on the right side, for instance, it seems like there's going to be a consistent 1/4" void from the inner face of the window all the way to the outside world. The idea of filling that entire cavity with caulk seems crazy to me. Will having just caulk (particularly the acoustic kind) provide enough of a weather seal for my needs? This is an exterior window in my basement. How do you apply the caulk so that when you're pumping it through one side it doesn't make a total mess as it eventually pumps out the other side? Wouldn't it all start pumping out as you fill the whole cavity up? Thanks!

n1ck wrote:

Will having just caulk (particularly the acoustic kind) provide enough of a weather seal for my needs? This is an exterior window in my basement.

no, you don't want to use the acoustic caulk as a weather seal. When you take out your old windows, square up the surrounding masonry so you can make your frames fit with a much closer tolerance than you have now. That will probably involce an angle grinder and fair bit of work unfortunately. Once you have a closer tolerance you can put some backer rod in the gap and then caulk a bead against that. On the exterior face of the window you would then have a timber casing bridging the window frame and masonry to protect the caulk seal.

n1ck wrote:

How do you apply the caulk so that when you're pumping it through one side it doesn't make a total mess as it eventually pumps out the other side? Wouldn't it all start pumping out as you fill the whole cavity up?

The backer rod stops all this happening. all the best, Steve

Hi all - Hope you're well. Long time no write. Funny how life gets crazy like that. So I'm still very much pursuing this wild adventure, though I've modified my plans slightly to be more realistic with my situation. It looks as if I'm now going to build a simple / rudimentary room within a room in my basement to be used for drum practice. My main goal is to isolate sound from the rest of my family and to be able to practice at weirder hours. I had a few questions. My basement is primarily cinderblock and is about 3/4 underground. The existing ceiling above me basically goes drywall, joists and then subfloor (so there's 2 ceiling leaves already.) My wife is adamant that I do no demo, so I'm gonna have to make some compromises in this process. I'm thinking I'm gonna do a single frame for each of the walls, support the new ceiling on top of those walls, and then do a few layers of drywall on each side of the frame (except for the ceiling, on which I'll only drywall one side.) Does that sound reasonable? For ventilation, I'm gonna do two vents (each with a baffle box) and an inline fan. Question: where does the fan actually go? I've heard that it should ideally go in one of the baffle boxes to minimize noise. Is that true? Sounds kinda weird to me. I've been forced to think about this project in a much more half-assed way, so even though it's not up to code, I'm strongly considering letting the vents exhaust and pull from inside the basement itself. Am I an idiot? And then for electrical, I'm thinking about either NOT having it (and just using some silly LED push-on lights) or running a small piece of conduit with an extension cord and then sealing up the hole really well. I was hoping you guys could tell me whether you think this idea is at all viable. Thanks so much! Nick

Just wanted to bump this in the hope that someone who knows their stuff can help me out with the query above. Thanks, all!

Just a little bump once again. Hoping someone can help me out.

The existing ceiling above me basically goes drywall, joists and then subfloor (so there's 2 ceiling leaves already.) My wife is adamant that I do no demo, so I'm gonna have to make some compromises in this process.

Not even taking off the drywall from the existing ceiling? Is she aware that the cost and complexity go up, and the degree of isolation goes down? In other words, that you'll have to spend more money and more time building it, for less result?

I'm thinking I'm gonna do a single frame for each of the walls, support the new ceiling on top of those walls, and then do a few layers of drywall on each side of the frame

.... and that would make your walls 3-leaf as well, thus complicating thing even further, and increasing your costs even more... The question is: why do you want to do 3-leaf walls?

(except for the ceiling, on which I'll only drywall one side.)

Correct. If you did it on both sides of that frame, then you'd have a 4-leaf ceiling, which is even worse than a 3-leaf ceiling...

For ventilation, I'm gonna do two vents (each with a baffle box) and an inline fan. Question: where does the fan actually go? I've heard that it should ideally go in one of the baffle boxes to minimize noise. Is that true? Sounds kinda weird to me.

You are right! That would be weird. And it would be a mistake to use an in-line fan as well. If you had an inline-fan inside a silencer box, you'd have no way of accessing the fan for maintenance, repairs, or replacement. You'd have to rip open the box to do that... It's far better to have an exhaust fan on the far end of the outlet duct, or a supply fan on the far end of the intake duct. The characteristics of the fan will be determined by the room size and occupancy. You will use the equations to calculate what the flow rate, flow velocity, static pressure, and duct diameter will be for that fan. Don't guess. You will also use those equations to figure out the size of the mini-split unit that you will need to do the cooling and dehumidifying. Don't guess there, either...

so even though it's not up to code,

Then you have a problem.... a BIG problem! Do not ever build anything that is not up to code, and fully inspected and approved, with all the paperwork in order. Apart from anything else, modifying your house without that will certainly invalidate your homeowner's insurance, so anything at all that goes wrong in your house puts you on the hook, both financially and criminally. For example, if part of the ceiling falls and injures someone, you would be criminally liable for that, as well as financially liable for the medical bills, and for whatever else that person decided to sue you for. Bad, bad, bad idea to build anything that does not meet code, and/or does not have all the paperwork in order.

I'm strongly considering letting the vents exhaust and pull from inside the basement itself.

Code does not allow that. You cannot use one habitable space as the source for "fresh" air that feeds another habitable space, nor can you exhaust the stale air from one into the other.

And then for electrical, I'm thinking about either NOT having it

... and where would you plug in your equipment? Battery powered amp? If you ever want to record, battery powered console? Battery powered DAW? Battery powered mini-split HVAC?

or running a small piece of conduit with an extension cord and then sealing up the hole really well.

While technically feasible, once again that would probably not meet code, and could be a fire hazard. Hiring an electrician to correctly wire in a single outlet and single light inside your room would not be all that expensive. Especially when considering the huge liability you'd be taking on by doing illegal electrical work. If that extension cord overheating and started a fire, you can bet your bottom dollar the insurance company would not pay out a single cent, ditto for any injuries/deaths caused by the fire. If the fire affected your neighbor's houses, you'd be liable for that too...

I was hoping you guys could tell me whether you think this idea is at all viable

Once again, while technically possible, the risks are pretty nightmarish. I would not advise you to do that. I'm also thinking that the the money you'd save by NOT building a 3-leaf ceiling and 3-leaf walls would go a long way to paying for the electrician and paperwork... - Stuart -

Stuart - Thanks very much as usual for your thoughtful reply. I'm gonna have to think about all this in the coming weeks. I obviously don't want to do anything to compromise my isolation, but I have to be realistic about what I can do. The three-leaf situation might just be my new reality. I have gotten back on board with the permit thing, though. I'm glad you talked some sense into me there.

:thu: - Stuart -