Insulation in attic

JoeMilner · Post by **JoeMilner** » Sat Oct 30, 2004 5:27 am

Hi
I have a 6-foot attic space above the ceiling of my recording area. The building was built in 1930, and has a curved roof, so the roof is sheathed with 1x6s, not plywood, and is uninsulated.

Per Steve, in the attic I've laid down a layer of R19 topped with a layer of mineral wool between the ceiling joists, and plan to add a layer of 1/2 or 3/4 plywood on top of the joists.

Is there any benefit (or detriment) to insulating the roof purlins above as well? It would seem that adding plywood underneath the purlins would result in a triple leaf (assuming the ceiling joists below had plywood on them), but would adding just the R19 and/or mineral wool help/hurt?

Does that question make sense?

knightfly · Post by **knightfly** » Sun Oct 31, 2004 5:16 am

Joe, it's been a while; currently, do you have (between you and the world) two SEALED masses, with air/insulation between? If so, then mass-wise you're DONE - and any extra insulation you place in the cavity can do nothing but HELP, up to slight compression... Steve

JoeMilner · Post by **JoeMilner** » Sun Oct 31, 2004 5:58 am

Hi Steve!
Let's see, from the sky down it goes:
1) Roofing material (composition)
2) 1x6 sheathing
3) 6 feet of attic airspace
4) 1 1/2" mineral wool
5) 6" fluffy
6) Drywall ceiling, single layer 5/8"

Thanks in advance, hope you've been well!

knightfly · Post by **knightfly** » Sun Oct 31, 2004 7:58 am

Hey Joe; been fighting a nasty cold, typical for this time of year; I'll get over it, thanks for asking -

IS your upper roof mass (roofing, sheathing) SEALED from the outside, or VENTED ? (I know we covered this before, too little time to look for it) If it's sealed, all you can do is add more layers to your inner drywall (if the ceiling framing can support it; this is important) and add insulation.

IF the outer roof is VENTED, then you may be able to make a noticeable difference by having sprayed cellulose added to the attic (a lot of it)just above your existing insulation - otherwise, this could get really tricky - I'd need to see both pix and drawings, as well as spans and sizes of everything before I could venture a guess for a plan.

How noisy is the place now; have you done any tests for isolation, or just noticed hearing things you shouldn't (or vice versa)? Steve

JoeMilner · Post by **JoeMilner** » Sun Oct 31, 2004 8:07 am

Hi Steve, I'm feeling a cold coming on myself...
Actually, the roof is SEVERELY vented right near the stage, which obviously compromises the isolation. and I'm in contact with the HVAC contractor to discuss more acoustically sound methods of ventilating the attic. The previous (now unused) heating system had its giant ductwork running down the center of the attic, and was vented (3 foot diameter) right above the stage...nice.......

So, all my questions are predicated on the assumption that that particular question will be resolved, and made acoustically sound.
The isolation of the space is pretty good already, even with the "ventilation" issue, it's just that I'd like to improve the ratio of time spent recording to time spent waiting for a noise to pass by, etc. As you know, it's never the bad take that has noise on it, it's always the perfect one