It's a fair question when you're standing in a garage looking at a blowing machine that has a fan, a motor and a long hose. Hook the hose to the other side, run it backwards, and surely it pulls insulation out as well as it pushes it in?
It doesn't. An insulation blower does not also act as a vacuum in any useful sense, because the two machines are built around opposite ideas. A blowing machine keeps the insulation away from its fan. A removal vacuum sends the insulation straight through its fan. That one design choice decides almost everything else about how each machine is built.
Inside a blowing machine, the fan never touches the insulation
The process starts with a compressed bale of fiberglass or cellulose. The job is to open that bale up, fluff it and feed it into an airstream at a steady rate. So the material path looks like this:
- Hopper. You break the bale and drop it in.
- Agitator or shredder. Rotating arms or tines tear the compressed insulation apart.
- Rotary airlock. A paddle wheel with sealed pockets carries measured portions of loose insulation from the hopper into the air path, while keeping that air from escaping back up into the hopper.
- Blower. Separately, a blower produces a stream of air that enters the airlock, picks up the material and pushes it out through the hose.
The blower is upstream of everything. It only ever moves clean air. That's why many blowing machines can use comparatively delicate blower motors: nothing gritty, sharp or heavy passes through them.
The airlock is the clever part, and it's also why the machine can't run in reverse. It's a one-way valve for material. Insulation goes in at the top from the hopper and out at the bottom into the airstream, with no path for anything to come back through the hose into the machine.
Inside a removal vacuum, everything goes through the fan
A removal vacuum has no hopper, no shredder and no airlock. It's essentially a large, heavy-built fan in a housing, with an inlet on one side and an outlet on the other. The fan pulls air and insulation up the intake hose, the material passes through the fan itself, and it leaves through the exhaust into a bag, a trailer bag or a dumpster bag.
Because the insulation goes through the fan, so does whatever was lying in it: old wasp nests, mouse bedding, shingle nails, chunks of lath. The fan and housing take those hits all day, every day, which is why both RAMVAC machines pair an AR-500 steel fan with an AR-400 steel chamber, abrasion-resistant plate of the kind used for wear liners and chutes.
Put a blowing machine's blower in that environment and it would last minutes, and its filters would load up long before that.
Pressure and volume are tuned for opposite jobs
A blowing machine needs enough pressure to push conditioned insulation up a long hose to a nozzle in the attic, at a rate the installer can control. The airlock meters the flow, and the installer dials it back for dense-pack walls or opens it up for attic floors.
A removal vacuum needs a lot of air volume at the nozzle, enough to lift settled, matted, sometimes damp material and keep it airborne all the way back to the machine. It doesn't meter anything. Whatever reaches the nozzle goes through. Feed it a wet chunk or a pile of packed cellulose and the fan takes the load directly. That's the job the RAMVAC-23 was designed around, including the sodden, sooty attics restoration crews deal with.
What happens if you try to vacuum with a blower anyway
People do try, usually with a hose on the blower's air intake or a homemade adapter. Typical results:
- The blower's intake filter clogs almost immediately with fine insulation dust.
- Anything that gets past the filter goes into the blower motor, which isn't built to take it.
- There's nowhere for the collected material to go. A blowing machine has no exhaust path designed to carry insulation into a bag.
- Clumps and debris jam whatever improvised fitting you've made.
If your blowing machine's manual describes a vacuum or cleanup mode, read exactly what it's rated for and stay within it. Expect it to suit tidying spilled material near the machine, not clearing an attic.
Contractors who install usually end up running both
For insulation contractors, the practical answer is that removal and installation are separate pieces of equipment, and crews that run both can take a retrofit from tear-out to reinstall without handing it off. Plenty of attics need the old material out before new insulation goes in: rodent contamination, water damage, smoke, settled cellulose that no longer performs, or an air-sealing job that can't happen with insulation in the way.
The two machines pair well on the trailer. The vacuum clears the attic into bags or a trailer or dumpster bag, the crew air seals, and the blowing machine goes to work on a clean deck. On the bag side, our insulation vacuum bags fit every insulation vacuum and any hose up to 10 inches, so adding removal doesn't tie you to one machine.
Talk to us about adding removal
If you're weighing up a removal machine to sit alongside your blowing rig, the RAMVAC insulation vacuum range is built for exactly this kind of work, and we're happy to talk through which one suits your jobs. Call 404-354-6268 for a quote at any hour. Bag and suit orders ship at no charge on the day you place them.
Frequently Asked Questions
Can a removal vacuum blow insulation in?
Not as an installer. It moves loose material from one end to the other, but it has no hopper, shredder or airlock to open bales and feed them at a controlled rate, so you can't get even coverage or the right density with it. Use the vacuum to take insulation out and a blowing machine to put it in.
Can I reuse insulation I've vacuumed out of an attic?
Generally, no. Material that's been through a removal vacuum is broken up and mixed with dust and debris, and it usually came out because it was contaminated, wet or degraded in the first place. It goes to disposal, which is why removal crews bag it.
Why are removal vacuums so heavy compared with blowing machines?
Because the material passes through the fan, the fan and housing are made from thick, abrasion-resistant steel to survive nails, wood and grit. The RAMVAC-23 weighs 295 pounds and the 40 HP diesel 1,150 pounds, much of it in the steel that takes the punishment.
Do removal vacuums work on spray foam?
No. A removal vacuum is for loose material: blown fiberglass, cellulose, rock wool and similar. Spray foam is bonded to the framing and has to be cut or scraped off first; only the loose debris that results can be vacuumed or bagged.
Is it safe to vacuum vermiculite with either machine?
Not until it's been tested. Some vermiculite carries asbestos, and since removal bags (RAM's among them) aren't HEPA rated, neither machine belongs anywhere near it. A positive result, or no way to test, means the attic goes to a licensed abatement contractor.