how to blow-in cellulose into a truss ceiling?

[vavet]

I'm looking at insulating my 24x32 detached garage. It has roof trusses - not intended for storage.
I'm getting hung up on whether cellulose is a viable option. I like the concept better than fiberglass because it fills more tightly around wires, outlet boxes, etc. I understand there is a net installed. At what point is the cellulose blown? I can see a few ways to do this.
1. install a net down the length (perpendicular to the truss chord leaving an opening, perhaps in the middle, perhaps multiple openings. Spray in the cellulose. Because you are able to work above the bottom chord, you can see how deep it is. How do you fill the area that is the last to be netted?
2. Install the net over the entire area. Puncture the net with the nozzle at various points to blow it in the attic. How do you know how deep it is? Or that it's even remotely close to being even?

Maybe you start with technique 1 and use technique 2 for the last bit that needs to be done?

Seems like most of the videos on youtube and instructions sheets I can find assume there is walk-in/hatch door access.
I wasn't planning to install a hatch, because it seems like I'd need multiple hatches to be able to reach all of them.

 

[Kaizen]

Install a hatch. You will need it at some point in the future. I’ve never seen just a net used. Always drywall or metal holding it up. Mark height on trusses for reference. Blown in is good because it’s easy to install.


Sent from my iPhone using Tapatalk

 

[JJohns3WG]

The times I have had it done they used the netting on the walls, then came back after the sheetrock was hung and blew in the ceiling.

 

[matt_i]

If I am reading correctly, I don't think you want to close off the attic completely. I would install the hatch, you never know when you'll want to add wiring or even inspect the underside of the roof for leaks. Worst case, check for critters.....

Once you do that, now you don't even need any ceiling net. Just install the ceiling covering and use the access point to move around and broadcast it completely.

I've seen some paper tape measures which were stapled here and there as depth gauges, but I think you could just measure and mark here and there with a sharpie marker.

 

[vavet]

I was under the impression that the roof trusses, unless they are specifically designed for it, should not have weight placed on them.
If I take some 3/4 plywood or 2x12s and use that to spread my weight across several bottom chords, is that enough for me to be able to move around while I blow it in?

If I locate the hatch centrally, I don't think the blowing machine is going to be able to reach the far ends of the structure. That would mean either me physically getting up there to move around, placing my weight (~190 lbs) on the bottom chords of the trusses, or creating multiple hatches.

The garage is 24x32. If I made hatches at the 8 foot and 24 foot marks (along the 32 foot dimension), that would mean I need to blow out 8 feet along that axis and 12 feet out towards the sides.
If I created only one hatch, it would have to blow 16 feet from the central point out for the ends of the 32 foot dimension.

I was tempted by the lower cost of blown-in (vs batts) and the idea that it can pack more tightly around obstacles (switch boxes, receptacles). The settling issue in the wall cavities seem like a show-stopper though. You end up with a huge air void at the top of the wall cavity.

Maybe I'll just got back to the fiberglass batt idea.

 

[EdT]

When I built my shop I tried to do as much of the work as I could to keep costs down and know what mistakes were made and who made them. It's insulated conventionally with fiberglass batts. I was preparing to install the batts myself and had priced out the materials from the local big box. Just on a lark I had a quote done by a local, fairly large, insulation company. The quote was about $75 more than the cost for me to buy the materials. That was a no brainer, so I didn't learn all about how to install insulation. So, before you worry about how you're going to do it and what you're going to use, you might at least get somebody out to give you a quote. It won't cost you a thing and you might pick up some useful info even if you end up doing it yourself.

 

[Muckin_Slusher]

I was under the impression that the roof trusses, unless they are specifically designed for it, should not have weight placed on them.
If I take some 3/4 plywood or 2x12s and use that to spread my weight across several bottom chords, is that enough for me to be able to move around while I blow it in?

Your trusses can handle you climbing/standing on them anywhere as they are, no need for plywood/2x12 unless it's for your own comfort.

 

[NUTTSGT]

Attic access/hatch about 24"x48" Big enough to get in and out easily, make it too small and you will be cussing yourself any time you need to get up there.

You only need one, not several. Make it somewhat centralized and not too close to the edge where the roof line comes down. Whoever you rent the cellulose blower from will have extra hose to reach where you need to be.

Don't cover up your soffit vents. Add baffles if you need to. Blow in more than you think you'll need. Not only will it settle, do it once and be done. You don't want to go back up there in a few years because you need more insulation.

Spray paint some marks on the trusses for depth so you don't have to keep measuring.

My access cover in the house is 3/4" plywood with stryofoam screwed on the backside for insulation. The cover sits on/hole trimmed out with some 1x4s. To keep the blown insulation back away from the hole, you may need to add some "retaining" walls around the perimeter of the access hole.

 

[vavet]

I've made the decision to proceed with the blown-in insulation. I've learned blown-in fiberglass is also an option and is not as prone to settling like cellulose is, making it a better option for the walls.
I've started putting up the fabric. I'm using a HF pneumatic stapler. It's not the ideal tool, but it's the tool I have. I have the first 32 foot long wall done. I cut out around the outlets and applied tyvek tape around the opening to prevent them from tearing open any further. I used about 4000 staples on this one wall. I know they have to be stapled pretty tightly and I'll admit I probably overdid it. While I was doing it though, I had a thought.

Why does the whole piece of fabric need to be stapled so tightly? They use these products in older homes with no insulation and trust the drywall to hold the insulation in place. On the rest of the area, my plan is to do this:
apply the fabric. Don't go crazy with the staples along the upper and lower 4 feet. Go crazy for that middle foot. Then install the drywall sheets horizontally at the top and bottom, leaving that middle foot exposed. That gives me just a one foot area that I can access when I'm ready to blow in the product. The net will still be there to reduce the load held in by the drywall, but the fabric is backed up by the drywall which is held securely by the drywall screws.
Any reason why this wouldn't work?

 

[TLCObsession]

Install insulation chutes
(optional) create raised catwalk
box out hatch area
Install ceiling drywall (assuming electric has been run)
Foam the penetrations
Blow in insulation

Forget the netting and other nonsense.

 

[csp]

Why does the whole piece of fabric need to be stapled so tightly? They use these products in older homes with no insulation and trust the drywall to hold the insulation in place.

Which is more rigid, fabric or drywall? Seems self-explanatory to me.

There isn't really any "load" that is being held in place, but the fabric will stretch, allowing more volume of cellulose in the cavity than the actual volume of the cavity is supposed to be.

 

[Firstram]

Pulling the fabric tight minimizes the the humps from overfilling. Lots of staples to hold it there. Filling it before drywall is the only way to be sure there are no holidays/voids.