I'm going to be installing RSIC (whisper clips) plus two layers of drywall and green glue on my ceiling and one interior wall. (For three exterior walls, I may use the staggered stud construction.) I'm also going to be building boxes for my recessed lights.

For the walls, I was thinking wiring, then insulation, then hat channel. (In terms of installation.) Does this sound correct?

For the ceiling, it's unclear to me how to handle this. I have to have the hat channel up before I put the boxes in, as I'm going to hang the boxes for the recessed lights on the hat channel. That seems as if this would be hat channel, then wiring, then recessed light boxes. But then the insulation would be last, which seems as if it'd be really hard to put insulation in after all of hat channel and lights have been installed. On the other hand, if I put insulation in first, it seems as if I'll be cutting part of it out to put in the boxes for the recessed lights and will have to work around it to install wiring. Any hints for the sequence for how these should be installed to the ceiling?

Finally, for a ceiling with joists that are 5.5 inches or so wide, do you use 3.5 inch thick insulation or go with thicker insulation?

If you have a limited number of ceiling boxes I think I would run your wires, then position a box on temporary strapping run from joist to joist, then get all your insulation in place. As you complete each area around the box you can drop the box and move on. You could even make a cardboard box as a proxy for the real boxes if you wanted something light weight to use to fit the insulation.

After all the insulation is up then put up the hat channel and put the boxes back as you go, or after all the channel is up which ever is going to be easier.

Its so wierd that you posted this today. I was just thinking about this exact topic this morning! I came to the same conclusion as Big....HAT last.

OK, speaking from experience, what I SHOULD have done....

Conmplete ALL framing first, which includes the hat channel. Then place your light cans and any backer boxes. Then run your wiring. Then the insulation.

It really should not be a big deal to fit the insulation in around the channel and boxes. At least it wasn't for me.

The mistake I made was placing the boxes, running the wiring and THEN running the hat channel. The boxes interefered with the placement of the boxes. It would have been MUCH easier to place the boxes around the hat channel (which is pretty much what I ended up having to go back and do with help From BigmouthInDc and BritInVA). It's easier to take the channel down to place a box than it is to take a box down to place the channel. And actually it's the same for putting in the insulation last. Just take down the channel, put up the insulation and then snap the channel back in. The hard part of the channel is getting the clips up and everything leveled out. Once that's done, snapping channel in and out is easy.

Don't forget to make sure the bottom of the boxes take into account the extra layer of drywall....it makes all the fixture fit a lot easier.

When you did your backer boxes, there are 2 ways to cut the drywall and I am curious which route you went. You can cut a square just a tiny bit smaller than the box in the first layer to seal the first layer of the drywall with the edge of the box, and then cut a circular hole in the second layer for the light. You could also cut circular holes in both layers.

Here is what I plan to do:

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=155524&stc=1&d=1255989252