Scissor Truss Ceiling Insulation

[saghi]

I am building a 20' x 32' pole barn shop. A 24' x 20' section of it has scissor trusses that are 5:12 on top and 3:12 on bottom. They span the 20' length. The short span leaves very little room between the top chord and bottom chord. My plan was to install vapor barrier on bottom chord of truss, baffles to block insulation from flowing into the vented soffits, those foam air channels so insulation wouldn't block venting, and then blow in several inches of fiberglass. Vented soffits and ridge (only the vented closure strips not a big raised ridge vent). This will be a minimally climate controlled shop.

Since it's such a small area, I'm now wondering if I can just blow in enough fiberglass to nearly fill the area. I probably couldn't completely fill it but could put more than I was planning. I'm going to have the machine rented so I might as well do as much as I can.

If I do this, I think I would leave the soffit and ridge vents and install the baffles and channels the same, then fill as much of the remaining area as possible.

Does this seem like a good plan? I doubt I would be able to completely fill the area so it might end up being 12-18" of insulation and 6" or so of air space but my goal would be to fill it as much as possible. Due to the shape, I would end up with thicker insulation towards the middle.

I plan to attach the hose to a pole and have access from both ends of the area so I think I can do it without having to crawl into that tiny space. Trusses are 4' oc and the ceiling will be lined with 29g ribbed steel panel.

Is this a bad idea? Would having the space mostly filled with insulation create any negative issues I don't see? Is leaving the venting in place a good idea? It was never planned to be a usable space so I figure I might as well put as much insulation as I can....

 

[MagKarl]

When we built our house the inspector would not allow blown in insulation on sloped ceilings, had to be batts.

 

[matt_i]

There is a scissor truss in my house center. it is all insulated with batts.

 

[saghi]

Interesting. I didn't think an inspector would not allow the blow-in. I know it would settle and want to move away from the middle but my space is so skinny, if I put 12-18" of blow-in, it would be completely against the vent channels at the outer edges and I figured that would keep the insulation from sliding out of the middle too much.

I could do batts but would have to put them in first from below, then vapor barrier, then ceiling panel.

I do have to have the framing inspected and a final inspection. I'm not sure if they would look above the ceiling or not. I'll ask if blow in on scissor trusses is acceptable before I do anything.

My previous house in the neighboring community had blow in on slopes but I'm in a different county now so that means nothing.

If I can mostly fill the void with blow-in, does anyone see a problem I'd be creating by doing that?

 

[sands35]

Batts can come with a kraft face. No need for a vapor barrier (poly).

*Some* scissor trusses can be ordered with an "energy" or "raised" heel to allow for more insulation.

 

[PittsS1]

I blew in cellulose in my scissor trusses, 5/12 roof, 2.5/12 interior pitch.

Used full width cardboard vents/baffles, sealed around them at top plate with canned foam, poly'd ceiling, drywalled, then blew it all in. Real tight quarters as I had to crawl up there, but ended up with about half the roof filled as you describe (insulation from drywall filled all the way to vent chute). I can't see a downside.

Cellulose did slide down and pack as I was blowing it in- that poly is very slippery and helps everything to slide down to the eaves, but I haven't noticed much settling since, plus it's much heavier than blown fiberglass. One thing to be aware of though- I went through way more insulation than I calculated to need, and I think most of that was due to it compressing a bit as it tried to slide down. Buy extra. I've blown a lot of cellulose and can typically estimate it closely- I was way off on this one.

I taped an extendable painters pole to end of hose. It was still a hassle to maneuver it around trusses, but I could get all the way down to eaves and shorten it up when needed. The plastic hose on those machines seems to always want to coil back up, catch on everything, and tangle. It was a frustrating but worthwhile project- garage is insulated better than my house and gas usage was very low for keeping it at 50 all winter in MN.

 

[saghi]

Thanks. I think it's going to be a pain due to tight quarters no matter which way I do it so I figured putting as much blow-in as I can would end in the best result.

Just wanted to make sure I'm not overlooking an obvious reason not to do it.

 

[GYPSY400]

I was told it had to be batts when i did mine.. i have the vent channels at the end, then one row of batts. . Which goes to two rows once there is clearance..(also offset the batt joints).. it will stick up there by itself, so putting up the VB wasn't that hard.




GYPSY400