Insulation for New Shop

[Jim Andrew]

Sound board is fairly effective. When I was in college, they had little practice rooms lined with acoustic sound board where you could practice your horn. Could hardly hear anything as you walked by, and there was a glass in the door. Think you would like the cellulose, if you used the glue that keeps it from settling. My nephew used blue denim insulation he bought at Menards to insulate between his upstairs and basement. Kids have rooms in daylight basement. Pretty effective.

[Dave Cav]

Spray foam insulation. More expensive but worth it.

Craig

That's what I did in my new shop.

[mark mcfarlane]

Cellulose & mineral wool are both better than fiberglass, which is better than spray foam. Spray foam is better thermally, but for sound proofing, not so much. Cotton batts are also good, but pricey. Decoupling & mass are also more important than the type of insulation.

Frank, saying that spray foam is the worst acoustic insulator compared to cellulose, mineral wool, and fiberglass was somewhat counterintuitive to me. I thought the tight air seal provided by the spray foam would help.

So I did some further research and it appears you are correct (although there are disagreements). Spray foam is not a good acoustic insulator. Open cell is a little better than closed cell.

Thanks for making this point. I just changed my specs on a new shop.

[Kerry Wright]

When I built my shop, I insulated everywhere there was a possible (sound) leak. In most cases I used regular rolls of fiberglass. In the tight spots I would use foam.

Every stud or rafter had a 1/4" bead of silicon applied, once dried I hung the first layer of sheet rock 1/4" off the floor and 1/4: from each adjoining wall and rafter. (Careful do not over tighten the screws). Then a second bead of silicon is applied and left to dry. The second layer of sheet rock is then hung making sure all seams were staggered and the 1/4" spacing at floor, corners and ceiling was maintained. (Ceiling is also double layered)

Finished it up by caulking every 1/4" space with silicon. I even sealed around all of the electrical boxes.

My only sound leaks are the two windows and the main door. I have two four inch inserts (made from sound board and insulation) for the windows and a large piece of soundboard to cover the door. Neither of which I have ever had to use.

The other upside is no matter what the weather outside is doing, the temperature in my shop is easy to maintain.

[William Shelley]

Frank, saying that spray foam is the worst acoustic insulator compared to cellulose, mineral wool, and fiberglass was somewhat counterintuitive to me. I thought the tight air seal provided by the spray foam would help.

So I did some further research and it appears you are correct (although there are disagreements). Spray foam is not a good acoustic insulator. Open cell is a little better than closed cell.

Thanks for making this point. I just changed my specs on a new shop.

Is it a poor insulator for all frequencies of noise?

My expectation is that the higher density of spray foam insulation would result in a more effective reduction of high-frequency noise (such as the whine of high rpm universal motors). Low frequency noise would probably be conveyed through the foam.

[Wayne Cannon]

Mass/density, absorbancy, and isolation are your friends.

Mass/density = thick sheet rock, DENSE insulation (i.e. not fiberglass or shrubbery), thick glass, stone, etc. The same amount of sound energy will result in smaller vibrations of high-mass materials. Acoustic tile is better than airy fiberglass, but minimally better.

Absorbancy = Rubber, etc., that absorb vibrations (i.e., convert vibrations into heat energy), such as rubber sheet of caulking between two sheets of sheet rock. "Quiet rooms" are sometimes lined with rubbery cones (the cone shape helps with reflected sound/echoes, not transmitted sound)

Isolation = Eliminating sound-conducting paths, e.g., by using double-stud walls so vibrations in one wall are not conducted to the other wall (watch out for paths at floor and ceiling joints, however), and hanging sheet rock with sound-isolation strips instead of fastening directly to the stuffs. Two (or more) panes of thick glass without a path from one to the other around the edges.

[Bill Jobe]

Don't suppose there's such a thing as white noise technology applicable to this subject?

[Scott T Smith]

Several years back I built a shop that has a 400HP generator in one corner of the main room. When operating, the generator is so loud that if you're standing next to it you cannot even be heard when yelling at a person standing next to you.

The approach that I took works very well, and it is a blend of the techniques recommended already in this thread. Sound level outside of the generator room is very low - you can tell that the generator is running but it is a very low level that allows for normal conversation levels right outside of the generator room.

The two outer walls are double wall with 14" of loose fill spray foam insulation scraps placed in them from floor to ceiling. The two walls inside the shop are 2 x 4 stud walls with open cell spray foam insulation totally filling the cavities. On top of the studs is a strip of foam sill tape, in order to isolate the drywall from the studs. Two layers of 5/8" drywall are installed over the studs, one layer at a time. The inner and outer drywall layers are separated by a "green glue" product which is an adhesive that isolates vibration between the drywall sheets. Finally, the outer most layer is some 5/8" homosote sound deadening board.

The doors have two layers of drywall (installed similarly to the inner walls), along with a layer of homosote board. The primary noise transmission outside of the room is through the doors.

The ceiling is open cell spray foam.

Overall the sound deadening is quite effective.

[Peter Aeschliman]

Wayne knows what he's talking about!

Much of the conversation in this thread has been about blocking direct airborne paths of noise (kind of like blocking air leaks) and insulation.

What's not intuitive at first is that most of the noise that gets transmitted through a typical wall or ceiling (assuming there aren't gaping holes of course) is vibration from the structure. Sound waves hit the wall and vibrate it, which passes through the fasteners into the studs, which passes through the outer surface of the walls, and produces airborne sound waves.

Insulation will help, but it's not enough if you want to be serious about it.

Mass in the wall itself (i.e., two layers of drywall) is your first line of defense. Green glue between the layers can also act as an isolator. Second line of defense is decoupling the drywall from the studs using resilient channel, which is snapped into noise isolating clips. Third line of defense is insulation, but if you do the first two steps right, the type of insulation you use isn't a first order decision. Mineral wool is better than fiberglass, but if you have mass and decoupling, you probably won't notice a big difference. Spray foam is not great for noise because it's too rigid, so it can transmit vibrations.

Anyway, good luck. Double drywall, green glue, and staggered studs might be good enough in this situation, but I'm just sharing what I've learned.

[Bill Dufour]

If nothing else use the denser Canadian type fiberglass insulation. R15 instead of R13 for very little extra cost. For some reason it is only special order in my part of the USA. I do not understand why R13 is still code?
Bill D.