Hi everybody, after reading about Green Glue and doubling up the drywall, I'm planning to do my basement ceiling as such. However, I'm also planning to install quite a few pot lights. Will GG still be effective or will the noise simply leak out of those pot lights and wasting my money? Is there anything I can do to seal those pot lights? PS. I will not sacrificing those pot lights as we really prefer them in the basement. Thanx.

You can keep the lights, just build backer boxes.

http://www.soundproofingcompany.com/manual/sim_backer_box_installation_guide/

Using GG without building Backer-boxes will significantly reduce the effectiveness of the GG. I have been told this by Ted White personally. Backer boxes are super easy to make.

After you take care of the backer boxes for the lights, use putty pads for all the electrical boxes and take a critical look at your HVAC system.

If you use backer boxes I would recommend using an IC (Insulated Can) pot light, as it's designed to have insulation directly against it.

The IC pot light will be able to deal with the restricted air flow, and therefore less heat loss caused by the box.

If you use a standard pot light and it begins to over heat you may get the thermal overloads tripping within the cans causing them to flicker on and off.

If it's too late, you can also reduce the wattage of the lamp, which should fix the problem in most cases.

I would recommend using an IC (Insulated Can) pot light

Close but no cigar.

IC stands for it's OK to be In Contact with the surrounding insulation. There is not an ounce of insulation in my IC cans. Just an air gap and a thermal sensor. Non IC rated cans must have a specified gap between the can and the surrounding insulation.

What you want is IC and Air Tight rated cans.

I did a back box for the ceiling electrical plug, as well as my spot lights with a double drywall/GG ceiling.

An excellent thread on back boxes is buried in the archives: http://archive2.avsforum.com/avs-vb/showthread.php?t=654719 (http://archive2.avsforum.com/avs-vb/showthread.php?t=654719)

I have had but one thermal trip in 2 years, with retrofit style PAR20 50W cans. It initially appeared I was getting substantially less bulb life, but I haven't lost a bulb recently.

Thanx everybody. That's a great idea for pot lights. Will definitely build my own backer boxes.

Couple of more question:

1. What about air vent and heat registers? Will noise be leaking thru those?
2. Where do I go to buy Green Glue in Canada?

Send me your email through a PM and I'll forward a couple of Soffit & Ventilation articles that will tell you what you need to build. We make these available to all AVS people.

As an aside, why do you call these "pot" lights? I've heard "canned" lights and recessed lights, but not "pot" lights.

Same thing I believe

Backer boxes are super easy to make.

I haven't made mine yet, but these backer boxes don't seem super easy to make. For instance, I'm going to be buying a table saw because I can't figure out any way to use my circular saw to cut 4x8 sheets of MDF/backer board while maintaining straight lines. You also have to maneuver heavy sheets onto a table saw, and do this outside, because the dust is supposedly terrible.

I'm also putting in 12-6 inch cans and 5-4 inch cans (aka recessed lights), so that's a lot of these boxes. And, you have to glue/screw each one of these. Then you're going to have to align them with the layers of drywall while hanging them. (And this doesn't count cutting the first layer of drywall around them. Also, for my lights, I may have to build them slightly larger, as the cord between the box and the canned part of the light juts out a bit and may make it hard to put a side right up against the cord.

So "super easy" might be an overstatement.

I'd use OSB and cement board. Cheaper and massive. Less dust. See the link I provided.

Can some of your can lights be mounted in a soffit rather than directly in the ceiling?

I have 23 can lights in my theater, but only 6 of them were in the DD/GG ceiling so only those 6 required backer boxes. The remaining lights were mounted in soffits that were constructed after the DD/GG went up.

BTW - my backer boxes are just MDF - I did not use any cement board,etc. I did some thermal tests and there was never enought heat (with my lights/bulbs) to cause me to use cement board.

Concerning HVAC, you really need to read some of the larger posts. All of what you are trying to do has been done before.

Best of luck.

You can certainly insert lights in a protected soffit. By that I mean the ceiling drywall and wall drywall has been applied. Then the soffit is built. This way, any sound that leaks into the soffit cavity through the lights has no where to go and is absorbed by the insulation in the soffit.

You would not share ventilation duct runs and lights in the same soffit due to cross talk between the light openings and the flex duct.

I haven't made mine yet, but these backer boxes don't seem super easy to make. For instance, I'm going to be buying a table saw because I can't figure out any way to use my circular saw to cut 4x8 sheets of MDF/backer board while maintaining straight lines. You also have to maneuver heavy sheets onto a table saw, and do this outside, because the dust is supposedly terrible.

I'm also putting in 12-6 inch cans and 5-4 inch cans (aka recessed lights), so that's a lot of these boxes. And, you have to glue/screw each one of these. Then you're going to have to align them with the layers of drywall while hanging them. (And this doesn't count cutting the first layer of drywall around them. Also, for my lights, I may have to build them slightly larger, as the cord between the box and the canned part of the light juts out a bit and may make it hard to put a side right up against the cord.

So "super easy" might be an overstatement.
Bob,

You can buy a straight edge for your circular saw that clamps onto the wood. Most residential table saws are not big enough (the table part) to support a full 4x8 sheet of plywood/mdf anyway. But a table saw is nice for when you get down to making multiple cuts of the same size material. So generally most of us here would use a circular saw to rip the 4x8 sheets down to a more manageable size (or have your lumber yard rip them for you), then use a table saw for the final cuts.

I used to do custom car stereo work and our table saw was 9.5' wide by 8' deep with a 4' out feed table that could be added on. We could rip 5'x10' sheets of MDF without breaking a sweat! That was fun!

That's what I've done for Panels. Additionally, I epoxied a port on my circular saw. The port accepts a shop vac hose. So while I'm cutting there's no dust. Cost $1

I use something like this http://www.rockler.com/product.cfm?page=16448&filter=edge%20guide for cutting large sheets down. Its a little fiddly and you have to make sure it is not cocked, but it works fine.

"Super easy" is indeed an accurate statement. I had Home Depot rip the MDF to the needed height and I used a chop saw ay home for the lengths. The outer shell was 1/8" MDF (small joist cavities) cut to rough size with a jig saw and I used a router with edge trim bit and edge guide to size the outer panels after they were GG'ed to the interior shell.