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I am preparing to blow cellulose into wall cavities in a small addition (I can’t find anyone around here who can do it). The outside sheathing and siding has been installed, but not the interior drywall.
Is there a problem with cutting out 2-3″ holes in the drywall and snaking in the 1-2″ blower hose? Does the drywall tend to break around the hole? Is there any sense in installing one of those membranes to hold the insulation in and then drywalling over that (or will it bulge out too far to drywall over)? Where do you get that material?
Can I do this with a Lowes-variety blower?
Any other suggestions?
Replies
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bill... no problem....you can either put the board up first or use a membrane..
modify your nozzle with a reducer and some 45 elbows..
we use a 1 1/4 " hole in either the board or the membrane..
if you reduce from 2" to 1.5" these are fairly standard fittings and you'll get a good pack.. in that case you drill a 2" hole to accept the 1.5" pipe
here's the membrane method: Regal wall... works great , too!
http://www.regalind.com/regal_wall.htm
*Bill,I find the patch work easier if you run the drywall horizontally, cut one sheet short enough that it leaves about a six-inch gap between the two sheets, with both edges at the gap having the factory taper. Make a jig out of scrap plywood or sheetrock scrap that is small enough (a tad less than six inches) to fit between the sheets and wide enough to bridge between studs (about 2 feet). Drill a 4-inch hole in the center of the jig, screw it over one stud bay, insert hose to the top of the bay, blow till machine stalls, yank hose back about a foot, it'll start blowing again, blow till it stalls again, repeat till you've backed yourself out of the hole. It helps to put a piece of tape around the hose about a foot before the end so you know when you are getting close to the end and don't pull the hose out with the machine running. Wrap a rag around the hose at the hole in the wall to keep cells from shooting out while you are blowing. Sometimes I blow from the bottom up to the hole then down from the top as well. I seem to get a little better density that way.When done cut a strip of drywall to fill the 6-inch gap out of sheetrock that is 1 thickness thinner (ie: 3/8 inch if using 1/2 inch drywall). Tape and mud to fill the depression.Steve
*Practice makes perfect...Don't think this too silly, but since there is no rock on the ineterior walls, consider screwing a sheet of ply over a couple of stud bays for a couple of practice runs.Pretend the ply is your sheetrock and drill your feeder hole into the bay.Fire up the blower and fill the ply-covered bays...try filling two adjacent ones.When done, unscrew the ply from the studs and slowly and gently pull it from the wall. If the cells were blown tight enough, they'll not fall out of the open bay. It'll indicate to you if you indeed blew the cells into all of the nooks and crannies of the wall cavities.Much better to get the technique down now than to curse cold spots in the wall next winter.
*The suggestions are good and useful. I was considering trying temporary covering to test the technique, I think it is a good idea. The garage side that will get some osb may offer a good spot to try and check if we don't glue it on.I'd like to think this will seem intuitive, but Murphy's Law usually kicks in somewhere along the way.
*In a FH article by the lamentably departed FL, using a "lean" mix of insulation to air is recommended; more air, less insulation resulting in better packing from a higher air pressure and less clogging of your feed hose. Any suggestions as to how to know if you are lean enough or is that another try it and peek at the results situation?
*Bill,Keep a bag count as you go. Calculate how many bags you need to get into a given area to achieve at least 3 lbs/cu. ft. Depending on the machine you use, you should be able to fill a bay in just a few minutes. You need a two-stage machine that meters the cells into the air stream such as a "Force One" machine, which has a "blast gate" that open into a chamber with a turning padle wheel that drops the cells into the blower stream. On that particular machine, I find that leaving about a two-inch gap in the blast gate works pretty well.Steve
*steve.. don't you find the "thru-blower" fans give more force ?i'm looking at a krendl 250A..and a force 1 or force 2.. and an accu1 9218... but i got over 3.5 pcf with an old hurricane blower on an old US Fiber machine..so the gate valves look pretty..but the thru-blowers seem like they will outpack them...what do you know? any other small machines i should check out ?
*Mike,I've only ever used the force 1 myself. I find it's hard to get much above 3 lbs with it. I've seen a krendle in action and it seemed like a pretty serious machine. I'm just repeating what I've heard others say here about needing a two-stage machine. Actually I got delivery of a thru-blowere with a load of cells once and sent it back to the store without even trying it based on what others have said on this board. It looked really cheezy and beat to s--t. Like a ten-gallon drum with a motor stuck on it. Maybe I should have given it a shot. Steve
*i'll let u know.. we've still got 80 bags to blow in the cathedral trusses...but the most serious looking weapon so far was that krendl 309 medium size blower mounted on the 250A...this US Fiber goes back to 1980....
*I'm just a homeowner, and all I can get my hands on around here are the Force 1 machines. I was wondering if this was a relatively "cheezy" machine or not. I blew about 200 bags this past year in my house walls and attic (with another ~100 bags to go). I left the gate open about 1.5-2" like was said above and was able to attain about 3-3.5 lb/ft3, but it took some time! Depending on the spaces, I was running somewhere between 15-60 min/bag!I'm glad to hear the Force 1 machine is apparently not as low-end as I had assumed.
*I just examined the blowers at our local Lowe's. They have Cocoon stickers on them, but Cocoon informs me that they are Promax 118's and should be sufficient to dense-pack. These are blue boxes about waist high and perhaps 3' square across the top. I talked about this with our Weatherization folks (public funded) and they say not. The machines they use are Promax 218's. Their expert even uses a supplimental through-blower to increase air pressure. They have offerred to loan me one of their blowers and I can get quite close to these walls, so may not need the suplimental blower.I have found one reference on the web to using Promax 218's to dense-pack walls. Anyone else have any experience with these?Also, how deep would you blow into the attic? I currently have 2' wide sheets of plywood running up the center of this attic for a catwalk. Do I just blow over this after filling beneath first?
*bill if you want you can pull up the catwalks and raise them to the new depth by running say .. 2x8's across the floor joists and then nailing your catwalks back down...or just bury them...but don't forget where they are.. or you'l be thru the ceiling
*Bill,You have to figure on about thirty percent settling in an open blown attic. So two feet of cells will eventually settle down to about 16 inches. Figure what you need for R-value and aim for that settled depth.Steve
*Mike, Steve, Mongo, thanks for your help. Finished up the walls yesterday and attic today. 8'x14.5"x4" Wall cavities took about 3 minutes each. The only major problem was popping off the drywall 3 times. Do you do anything special when you install drywall over a cavity to be dense-packed? Towards the end, the tubes started to jam, change in humidity? After closing the gate a couple notches and making the mix leaner, we finished. I found that narrow wall cavities were difficult. Two walls were broken up with windows and doors resulting in mostly narrow floor to ceiling spaces. If I blew in the top or bottom until the blower backed up, the opposite side was pretty much already too dense to jam the tube in far enough to pack the entire section to my satisfaction. How do you deal with situations like that? I took three pictures, old hat to you perhaps, but new stuff for me:Garage site walls before starting:
*Promax 218 blower and hose assortment:
*My "helper" (OK, my contractor) packing a wall asn he covers the opening with a batt of fiberglass insulation Completed walls are to his right. Notice the dust covered lens.
*cool....... er, i mean warm....bill i do it differently.... i use a one inch nozzle in a 1 1/8" hole ....either 2 or 4 holes per bay...
*Mike, that would have solved the narrow bay issue. We did open an additional hole in those bays where we couldn't pack the far end.