DIY dense pack cellulose
 

Has anyone here ever done dense pack cellulose insulation? I'm planning on doing it for my office remodel and am just wondering how difficult it is? If there are any tricks, necessary tools, etc.

I know there are different ways of doing it. I've seen it blown in using insulation mesh over an open wall so you can see what is going on. This is the method I plan on using having never done this before.

I've also seen it where they just drill holes and fish a tube into the wall and slowly pull it out as the cavity fills up.

I don't have any links handy, but a dense pack cellulose calculator so you know how much to buy would be quite useful too.

Anyway, if you have any tips, tricks, info or links, please share!

Here is a good general overview, not really any tips but describes the different methods of using cellulose insulation:

Cellulose Insulation Facts & Do-it-Yourself Guide | RafterTales | Home Improvement Made Easy

The problem with DIY dense pack is that it's difficult to get the proper pressure with a rental machine. I have yet to find one that can produce the necessary pressure even right at the outlet of the blower. Also you need to step down the diameter of the hose in slow increments so you will need to buy the hoses (it's really important for the last hose at least to be of proper quality) and the reducers. Aside from that, you just push the hose to the top or bottom of the cavity through one hole in the middle and then run it until you hear the pressure back up in the hose. Then you pull it out a little bit and repeat. After you get back to the hole push the hose down to the bottom and repeat. The insulmesh serves two purposes. First it lets you kick the tires so to say. Also it keeps the cellulose in place but lets the air escape instead of it all blowing out the hole you're sticking the hose in.

I guess I'll start calling around to see if any places have machines for dense packing cellulose.

You might also want to get some quotes for having someone do it for you. At least out here a lot of the cellulose guys are very reasonable. They are often willing to work with me on costs. They pay less for cellulose because they buy it in huge amounts. So maybe you can work a deal where you fill the hopper while the guy packs it. Something like that. I can't imagine it would cost too much to dense pack one wall.

I do actually know a guy who is getting into the business. Hes from the local makerspace and I helped him a few weeks ago. He bought a machine and was modifying it to get more power for dense packing cellulose. I'll probably shoot him an email.

So what happens if you use a rental machine to spray in cellulose in the walls and try to dense pack? Is it just loose fill and settles and creates voids?

Yep. This is why the blowers have gotten so much more powerful. It used to be done with a cheap blower and the "two hole method" and now all of those walls have spots with no insulation. At first it's really nice though as loose cellulose has better R value than dense pack. Not by much but a little. Actually This might be canceled out by the fact that loose fill doesn't have the same air sealing properties as dense pack. These days the two hole method is only used if there is concern about the inside wall blowing up under the pressure. Even with a pretty nice blower (Force 2) you need to reduce the hose size quite a bit to get the needed pressure. There's no way to get 3.5 Lbs. with the giant hose used for a loose blow.

Apparently Robert Riversong uses a rental machine so it's theoretically possible. You need to get a pressure tester for it which can be picked up at, well, I'd get it at National Fiber because they are right near by. You also need a good hose (read Tiger Flex) for the last length or else you will get clogs and all kinds of other problems. Regular vinyl hose keeps it's shape so it will be all curled up and not interested in going where you want it leading to voids, frustration and settling. You also need to reduce the hose size gradually or you again will get clogs.

Hi Tim,
I've never done it myself, but there are a couple pretty detailed descriptions here:

Blowing Cellulose Insulation into Existing Walls

Gary

Thanks Gary. I think I'll call around and see if anyone has a machine capable of dense packing.

Get a pressure tester so you can verify for yourself that it can push out 3.5 Lbs. Make a test box. Build a 16" O.C. box out of 2x4's. Cover the back with OSB or something and mesh off the front. Make it tall enough to give you a sense of how filling it all up works. I'll be easier to tear the cellulose out of a bad test box than an entire cavity.

I just did this last weekend in my kitchen project. I'm not sure if my job is up to dense pack standards, but with my open hand, I can not push into the cellulose at a test hole. I think it worked very well.

Here's what I did.

I rented the basic machine from Lowes. Set the adjustable plate at the output to about 25% open. Bought a 1 7/8" diameter universal vacuum hose and taped the included adapter to the end of the long 3" diameter hose that came with the blower. Then I pulled the hard adapter out of the flexible vacuum hose at the very end. This was so it would flex enough to pull out of the wall while blowing.

I used a 3" hole saw to drill a single hole at a time in the inside of the wall to be insulated. I did not want cellulose to blow out empty holes nearby. I drilled these holes about 6 foot high as the vacuum hose was 6 foot long.

The thin vacuum hose slid down the wall easily and I wrapped a towel around the hose to seal the hole. with the machine running I could hear when it bogged down. When this happened I pulled a few inches of hose out of the wall. When the hose got close to the hole I quickly turned it and pushed it up into the top of the wall, two feet above.

I did drill a few test holes to check the results and as I said above. I could not push my open hand into the cellulose.

To finish up I sprayed "Great Stuff" foam in the holes and pushed the plugs from the hole saw back in. As the foam cured I adjusted the plugs to be flush with the wall surface.

A note on prior steps: I had these walls open the week before and sealed everything with 2 -3" of spray foam from "Tiger Foam". I also made sure there were no barriers to keep the cellulose from filling the cavity.

The end results, I estimate an R-value of 39.5 where at best I had R16 before, and nearly a complete air seal.

How thick are your walls?

I was at Lowes the other day and saw their cellulose machine sitting out and I don't have the slightest bit of faith that it would be able to achieve a dense pack that wouldn't settle or wouldn't leave big holes. I think that calling rental centers to find a Force 1 or 2 would be what you'd have to do.

They were 2x4, now they double 2x4 with a small gap between = 7.25".

| 3.5' | .25"gap | 3.5" |

The key was setting the adjustable plate at the output to 25% open. This way the full volume of the blower air was pushing a small volume of cellulose. I am confident that it is packed enough to never sag. Maybe not up to dense pack standards, but it won't sag. That was my goal.

You have to do the same thing with a brand new Force 2. If the blower can't put out 3.5 lbs at the hose you can't get a dense pack.