Insulating truss webs

[spudley]

In a build presently and considering options for insulating the unfinished ceiling.

I'm dealing with 16" deep floor trusses on 16" centers and trying to figure out how to insulate the webbing of the truss. At 16" centers I have 12 1/2" openings between trusses. Haven't found any fiberglass insulation that width. With a floor above I'm limited for access. I'm thinking I could cut 23" wide fiberglass in half to get 11 1/2" and stuff in some pieces to fill remaining gaps along the field but the 3 1/2" webs between those openings appear to be a major PITA.

I'm open to either sheetrock or metal for the finish ceiling.

Maybe blow in insulation as I go?

 

[JackAndy]

Is this a garage or house? I guess I'm not sure if this is a basement ceiling or if this is the ceiling between the first and second floor or a 1.5 story home. I know that might sound redundant but even though I have a finished basement, I would insulate the ceiling just to control noise. So I'm not making many assumptions here.

You could blow it in but can you imagine the mess every time you need to access the ceiling to fish a cable through or change a light fixture? This would probably be the easiest/cheapest solution though.

Or you could do what you mentioned with the fiberglass rolls and the cut sheets of rigid foam insulation board. It comes in 2" thickness and isn't difficult to cut exactly to size.
I guess you'd have to trace the pattern of the 3.5" webs and get a template going on a piece of plywood or something. Then you could lay that on the rigid form board and cut it out. They even make a heated styrofoam cutting blade that 'cuts like a hot knife through butter'.

A third option would be spray foam insulation. This might be good if its a basement ceiling. With 16" deep floor trusses, you could achieve your required R value by spraying on the bottom side of the subfloor/top side of those truss webs. It would only be a couple inches thick and the rest of the space would be open for ducts, wires etc. Then if you ever had water damage and had to replace the sheetrock, you could remove it without having a ton of blown-in insulation.

 

[speed bump]

I would install your ceiling and blow in cellulose from the top. Unless you already glued down your subfloor removing some subfloor and filling from the top should be pretty easy and quick.

 

[matt_i]

I think you are trying to fill in the triangles?

If so, I would get 3-1/2" Roxul that's ~15" wide for 16" stud cavities. and an insulation "knife" its sort of a bread knife/saw.

Cut and fit the Roxul to each one of the webs. Then you can push your fiberglass into the large open cavities.

 

[ripperd]

Our builder for our house put an insulation "net" on the bottom of them, and then blew in insulation. After that it was drywall. You could probably do something similar with a net or even the drywall, going some as you go.

Something like this probably:

https://www.menards.com/main/buildi...insulation-netting/nt6250/p-1444423326355.htm

 

[rburke65]

I don’t think that’s the usual plan of attack to insulate. Can you not just blow in insulation?

 

[spudley]

I think you are trying to fill in the triangles?

If so, I would get 3-1/2" Roxul that's ~15" wide for 16" stud cavities. and an insulation "knife" its sort of a bread knife/saw.

Cut and fit the Roxul to each one of the webs. Then you can push your fiberglass into the large open cavities.

I like this. I'd like it better if I wasn't the lone ranger on this project.Oh well...

Our builder for our house put an insulation "net" on the bottom of them, and then blew in insulation. After that it was drywall. You could probably do something similar with a net or even the drywall, going some as you go.

Something like this probably:

https://www.menards.com/main/buildi...insulation-netting/nt6250/p-1444423326355.htm

That might work as I could at least see if those triangle areas get filled.

I don’t think that’s the usual plan of attack to insulate. Can you not just blow in insulation?

Not easily as the area above is sealed off, by a glued/nailed 3/4" sturdifloor. I did consider blowing in insulation as I install a few feet of either metal panels or a sheetrock ceiling.

 

[scottydosnntkno]

Drill 3” holes every few feet from the top in a grid and blow it in. As long as your doing some type of flooring other than carpet you’ll be fine

 

[readhead]

What are you trying to accomplish? Is this for sound, heat or cooling? Depending on what you want to do I might have some ideas.

 

[Radix2]

Insulators fill cavities like this all the time.

Put up your ceiling except for one sheet.

Make sure your bays are as clear as possible - wires secured off the bottom, braces etc.

They will feed the hose to the furthest end then pull back, filling the cavity as they go. Stuff the last part with fiberglass and put up the last bit of ceiling.

Cellulose has better cold performance and will fill all those odd spots.

 

[spudley]

What are you trying to accomplish? Is this for sound, heat or cooling? Depending on what you want to do I might have some ideas.

Mostly heat. It's a garage with a partial second floor.

Insulators fill cavities like this all the time.

Put up your ceiling except for one sheet.

Make sure your bays are as clear as possible - wires secured off the bottom, braces etc.

They will feed the hose to the furthest end then pull back, filling the cavity as they go. Stuff the last part with fiberglass and put up the last bit of ceiling.

Cellulose has better cold performance and will fill all those odd spots.

The insulator will be me. If I go with cellulose, I'm thinking I could install a row of sheetrock and then blow insulation as I go.
Hmmm...that sounds like I may need some help (especially with the sheetrock), but that's another issue.
Seems I'm getting to be a one man band lately as all my friends (except for me) are getting old.

 

[readhead]

How about a layer of rigid foam first and then whatever finish material.

 

[matt_i]

If I go with cellulose, I'm thinking I could install a row of sheetrock and then blow insulation as I go.
Hmmm...that sounds like I may need some help (especially with the sheetrock), but that's another issue.
Seems I'm getting to be a one man band lately as all my friends (except for me) are getting old.

The problem with hang-a-sheet, fill-it-up is that you rent the insulation machine by the day, and unless you have a huge crew the rental cost will spiral.

The tactic mentioned of hanging the entire drywall save leaving a strip or one sheet off and then using that clearance to blow in the insulation would be best.

You have to look at the way the insulation would "flow" and look at areas that could be blocked off because you'd never see them and the result would be an uninsulated air pocket.

For insulating before enclosing the very last sheet/strip you could either hang an insulation net and poke just a hole for the hose or use roxul.

Buy or rent a drywall sheet lifter to make your life so much easier

 

[spudley]

The problem with hang-a-sheet, fill-it-up is that you rent the insulation machine by the day, and unless you have a huge crew the rental cost will spiral.

The tactic mentioned of hanging the entire drywall save leaving a strip or one sheet off and then using that clearance to blow in the insulation would be best.

You have to look at the way the insulation would "flow" and look at areas that could be blocked off because you'd never see them and the result would be an uninsulated air pocket.

For insulating before enclosing the very last sheet/strip you could either hang an insulation net and poke just a hole for the hose or use roxul.

Buy or rent a drywall sheet lifter to make your life so much easier

The ceiling area is approx 23' x 39' so trying to blow insulation over 20' (leaving a center piece out) and realistically filing all the triangles with braces blocking some areas doesn't seem too viable.

I'll probably use your earlier idea of roxul cut to fit and fiberglass in between.

Spray foam would be best but I haven't won any lotteries lately.

Really just want the area to hold in some heat on the colder days.

If I go with drywall (and I don't mind mudding and taping), I'll definitely buy a lift and resell when finished.