Blown in cellulose insulation for "un-crawl-able" crawlspace

[branimal]

I debating DIY blown-in-cellulose for a crawl space attic. It's the space b/w the roof and the metal stud ceiling.

B/c it's a flat roof building (3/8:12 slope), and I have 2 different ceiling heights in the building, the crawl space varies in height throughout, but it is un-crawlable.

Space is 1000 sq ft (18'x55')., I'm in NYC, Looking to get into the R-30 zone.

Right now there's no sheetrock on the ceiling. See pic.

I'm trying to come up with a plan and this is what I've got.

1. sheetrock the entire ceiling
2. install IC rated air tight recessed light
3. Insulate the dryer duct line and the kitchen exhaust duct,
4. Cut square holes in the sheetrock large enough to get a human head & shoulder's through every 10' or so.
5. Blow in insulation up to required height. I'll put paint sticks with markers for appropriate insulation height.
6. Close the hole and move onto the next hole.


Right now I have a Cupola (doghouse) vent in the center of the building. I've read I need to add 2 vents (front and back) to allow airflow in the crawlspace.


Good plan? What needs to be changed?

 

[Jlbc212]

I served as a full-time firefighter for 37 years in an old city with balloon, wood frame tenement housing. The vast majority of the housing was built before electricity became commonplace. When electricity was added "bx" metallic sheathed cable was used. The outer metal sheathing served as the ground path. Then in the 70's (the time my career began) came the energy crisis with the need for additional insulation. Blown-in cellulose insulation is the cheapest, most common method to insulate. From actual first-hand experience I had at least a half dozen fires each year where the cellulose insulation was the first material ignited. Most of these fires started in the ****-loft, the small space between the ceiling and the flat roof of these tenement buildings. An electrical short to ground (the poor conductor outer metallic sheathing) would draw just enough current not to blow a fuse or trip a breaker but enough to cause that metallic sheathing to heat up and glow red like a toaster wire. The heat would initially start a slow smoldering fire in the cellulose before eventually bursting into open flame. Many times the entire roof would burn off the building before full control of the fire. From my experience I would never recommend cellulose or other organic based insulating materials. There are other inherently non-flammable insulating materials such as fiberglass or vermiculite that can be blown in.

 

[rsanter]

Can you spray foam on the bottom of the roof deck?

 

[DC73]

Sounds like a good plan. You definitely need to make sure you have enough ventilation of the space above the insulation. BuildingScience.com and GreenBuildingAdvisor are a couple of resources where you can find info on proper attic ventilation.

At a minimum, you need at least the same square feet of intake vents that you have for exhaust vents in the cupola. More might be better.

Blown cellulose settles somewhat so if you want to end up with R-30, blow more to start with. There's a chart somewhere on the internet that shows how much cellulose settles.

Modern cellulose insulation is treated with a Class 1 fire retardant. I wouldn't have any concerns about installing it. In fact, I put some in my mother's house.

DC

 

[brownbagg]

hire it out, cheaper less hassles

 

[NUTTSGT]

Even treated, cellulose still burns or smolders until it catches other material on fire. We just had a rekindle a week ago Friday because the stuff.

Granted, I get why people use it but I try to stay away from the stuff. If I were to build a new large shop, I might use it in the ceiling and there is a local place that makes it, so it'll be cheap.

 

[engineer2]

My house is insulated with cellulose. Just sayin', but mice and carpenter ants love the stuff for nests.

 

[branimal]

Interesting point on the bx cables igniting the cellulose. I rewired the entire place with 12/2 MC cable with a green ground wire in the shield. And I ran 19 circuits for a 1000 Sq ft apt. And all the heating/cooking/drying is done with gas so there are no 240volt circuits. I'm not worried about electricity igniting the cellulose. But perhaps something else could cause the cellulose to ignite /smolder.

Mice nesting in the cellulose is a scary thought. I cannot stand vermin. I see they make pest control cellulose, but it's not mice proof.

https://www.homedepot.com/p/TAP-Pes...-Insulation-30-lbs-36-Bags-INSTAPLD/305501160