Compressed Air Transfer System

Blowing polystyrene beads into house walls for DYI insulation - version 3

I'm migrating this info over to a blog at:

Once it's settled in I'll come back and rebuild this wiki into a step-by-step how-to guide.

Progress will be slow because I can only work on this a few hours a week.

Cheers, Paul
13 August 2011

See also:

13 August 2011 - migrating to

I'm migrating this info over to a blog at:

That's where my ongoing experiments will be posted from now on.

Once it's settled in I'll come back and rebuild this into a step-by-step how-to guide.

Cheers, Paul
13 August 2011

11 August 2011 - Blower gun detail

Jim from Levin asks for some close-up's of the blower gun so he can make one himself.

Blower gun close-up.
Blower gun close-up.
Blower gun with insert in blow direction.
Blower gun with insert in blow direction.
Blower gun with insert in suck direction.
Blower gun with insert in suck direction.
Blower gun with lines showing air flow.
Blower gun with lines showing air flow caused by the venturi effect. Blue lines show air being forced in from compressor. Red is air and beads sucked from the bag.

Air comes in from the compressor thru the handle. (The trigger opens a simple valve to allow the air to flow.) The air then enters a circular chamber (seen in the "insert" photos above). The chamber has about a dozen little holes that are angled to direct the air along the barrel (or, if the insert is turned around - back down the barrel). So the air from the compressor rushes along the barrel and out the nozzle.

The venturi effect causes air and beads (shown in red) from the other end of the PVC tube to be sucked up and out the nozzle end of the gun - hopefully into your wall cavity.

Note: the Wikipedia article on the venturi effect didn't help me understand what's going on.

As an aside: a cool use of the venturi effect is in bladeless fans.

5 August 2011 - sources for beads outside Wellington?

I've just received this from Tim M in Dunedin

It is going to cost me $400 freight to ship $100 of poly beads to my house from Wellington because I live in Dunedin. While this is still worth it in my opinion, it would be nice if there was a source for beads down this way. Would you know of any?
I am an electrician so I can just rerun the segments of electrical cable that go down external walls in "non-migratory purple cable" which is easily done although cost of the purple cable is three times the normal TPS cable.

Do you know of sources for polystyrene beads outside Wellington? Email Paul if you do

For those interested in "non-migratory purple cable" here's a few links:

25 July 2011 - Electrical wiring in polystyrene test 2

Electrical wiring in polystyrene, test 2.

My first power cord in polystyrene test is still running; nothing noticeable is happening.

Someone pointed out that a consumer grade power cord, as used in the first test, may be made to higher resiliency standards than the kind of wiring you find inside the walls of your house.

So now I've made a short extension cord out of standard electrical wiring (the same you'd find inside the walls of your house - although mine isn't decades old). I've plugged my fridge/freezer into it as a real-world load. Then I've stuffed some of the electrical cable into a coke bottle filled with polystyrene beads (sourced from PolyPalace). And I've plugged in a KillaWatt meter to measure the power going through the wiring.

This test will be easier to monitor as it's sitting on top of the fridge. (The other test is running in the garage.)

I'll keep you posted.

24 July 2011 - finishing off my house

Back in 2007 when I "finished" my house I hadn't worked out a way to insulate wall segments that contained electrical wiring - so I left them empty.

Thanks to a suggestion from Steve in Rotorua I'm now blowing Rockwool Granulated into those final 5 segments. Rockwool is highly inert so it avoids the problem of polystyrene reacting with electrical insulation plastic. Our 32mm diameter blower gun works fine - it's a bit slower than the polystyrene but gets the job done.

I've discovered another lesson worth passing on:

When doing your own house - blow the Rockwool segments around your house first. Then do the polystyrene segments.

What I discovered is the "empty" segments had some polystyrene beads in them. (I removed the face plate of electrical power outlets to inspect. Make sure you switch off the mains before trying this yourself.) They must have drifted in from neighboring segments I'd filled. So - if you blow the Rockwool first you won't have polystyrene migrating into those segments.

The other consequence of having the polystyrene drift into the empty segments is it means the neighbouring segments have now lost beads - so there will be a gap at the top of those segments. Doh! I'll try to get another IR Thermal camera to look for segments with gaps. Hopefully it will only be a problem on segments adjacent to the empty ones.

If you blow the Rockwool segments first you can avoid these problems.

I'm also testing a 24mm nozzle (made from plumbing bits). So far it seems to have good flow speed and does not block up. It may be a good compromise between (a) wanting the smallest hole possible, and (b) wanting high flow rate.

Comparing the size of 19, 24 and 32 mm holes.

18 July 2011 - Mike from Porirua

Mike from Porirua is the first person to hire the new blower gun kit. He has 4 bags of poly beads to blow. Here's an update from him:

Hi Paul
I have got started and finished one wall of one bedroom (the only external wall), and the external wall of the toilet next door. Have hit a hold-up as my daughter and two grandsons are staying in the other room with two external walls to do and they don't go away until Wednesday. So whilst I have marked out where I think the studs and dwangs are, I can't get going until after midday Wednesday.
Some pitfalls so far...
1. Finding the braces [dwangs] between the studs. I haven't got a stud-finder so use my ears and tapping with a light hammer, then tapping through with a thin nail. It works really well for the studs. Once I have found one the rest are pretty easy by measuring, and tapping, and checking with the nail. I can find the horizontal dwangs easy enough in the same way - apart from when they are not there, and we have a diagonal brace. I discovered best way of doing this is to drill one hole at top and drop a plumb line in with a large nut on the end. So I get one position then work out the rest of diagonal by tapping and exploring with thin nail. The beauty of the thin nail is it almost disappears without fill. Though of course that will happen when I finish the job and paint the room.
2. Problem number 2 was having drilled the 32mm hole, I found they were the source of lots of investigation by grandchildren and their newly discovered fear of spiders and the fact I wasn't doing the blowing of beads until the next day, so I nipped out and bought some doweling which turned out to be 35mm. This wasn't a problem as I found drilling into plasterboard not so exact and definitely had a bit of wobble when I got through, so the 35mm dowel fitted in almost exactly. [Note: A tri-bit drill does a cleaner job in Gibb/plaster board. Paul]
3. Because of the wobble when drilling the fit for the gun was a bit loose, but not so much of a gap that I had beads blowing everywhere. That came later...
4. When I started the filling of the cavities I found some beads would emerge from the other drilled holes, and I had some doubts about the integrity of the building paper between the studs and the weather boards. On about my third fill I found myself filling at ceiling level and it taking a longer time than expected to fill so looked down to find them emerging just as fast as they were going in about my knee level. Guess that was where a dwang had been placed upright, which gave access to the cavity below. But of course having got all the dowels I was able to plug these holes and solve the problem. [In columns with multiple holes it might be best to start filling from the bottom hole first. Paul]
5. Time for the filling was usually well under a minute. I have a pretty grunty compressor. Working on my own, I found wiggling the tube in the bag sometimes difficult. At times I found the tube filled but beads weren't emerging. So tapped the tube to empty it and then blew out the gun in case there were any sticky particles there. This happened only 3 or 4 times in 30 odd fills. [If the hose becomes blocked you can try putting your hand over the gun nozzle, then "twitching" the trigger. This may create enough blowback to push the beads back down the hose. Paul]
6. Discovered filling the drill hole with the expanding foam harder and much messier than I expected. I solved that problem by using the end of one dowel pressed up to the hole with only a small aperture for the foam to enter hole. Worked really well. [We've also found the expanding foam process tricky. I'm not sure if something like Polyfilla would be any better - my hunch is that a 32mm hole is slightly too big for Polyfilla to fill cleanly. Paul]
All going well - I should be finished on Thursday.
I am pretty happy with everything so far so thanks so much again, and I am enjoying the experience.
Regards, Mike

Then there was a follow-up after he finished the job on the 20 July:

Hi Paul
This morning I got back in to getting the remaining 1 and a half walls done.
And I had a nice surprise when I had filled the half wall and begun drilling into the last big wall to find the previous owners had obviously put pink batts in.
So that part of the job finished inside 3 hours. Whole job done - and 1 and half bags of beads left over which PolyPalace say they will take back.
All went absolutely great. The blow gun is fantastic, though I found the tube and its pretty insistent curve a bit frustrating. Another person managing the open end of the tube in the bag would have made it much easier.
I am really pleased and now ready to see about double glazing the main room. It actually has the smallest window too. I will go for a factory made unit, though I am tempted to look at acrylic sheet for another experiment... though I expect my wife will not be so willing.
Thanks again, Mike

14 July 2011 - Second blower gun and hose available for hire

I've made up a second blower gun to hire out to fellow experimenters. The package contains a blower gun and 2 m hose, plus a strap to clamp the hose in the bag of beads. [I'll post a pic soon.]

I'm currently hiring it out at $10 a week (but maybe that's too cheap?)

Email me if you'd like to hire it.

13 July 2011 - dealing with polystyrene dust

Polystyrene bead bag with dust tarp wrap

Currently the white 250 litre bags of beads PolyPalace supply are mostly dust proof. Or to put that another way - they leak a fine powdery polystyrene dust if you man-handle the bags enough (which you do when you're trying to suck to the last 5% of beads out of a bag). To combat this we've created a anti-dust wrap from a small tarp. It seems to work fine.

PolyPalace are working on building a dust filtering system "soon" that should remove this problem.

I work on the assumption that breathing polystyrene dust is a bad thing for the health of the installers. Once the walls are filled and holes covered the dust is not a problem - as far as I'm aware.

16 June 2011 - update from Steve in Rotorua

Here's an update from Steve in Rotorua (who put me on to the Rockwool solution to filling wall segments with electrical wiring):

Hi Paul
Thanks for that great video clip. I figured it would settle a little over time, once the cavities were full I poked round with a wire and my finger to push it in more then blasted more in, repeating until it felt jammed tight. Your test cavity actually filled better than I thought it would on first fill. I think my main fill problems are round the cable and outlet sockets as once the wool binds up and jams a section nothing will get past it so fill could be very lose opposite side of cables. As you say, it's still far better than leaving the cavity empty.
Finishing up our kitchen earlier in the week and screwing the power-points back in after painting I noticed a couple of sockets that had little wool behind them and could feel the cold when I put my fingers in the flush box. I stuff these up by had with more wool and could notice a difference straight away as I didn't notice the cold with my fingers in the box. I only have fibre cement panels for cladding which offer no insulation really, so the insulation is keeping the cold out (or preventing it from wicking the heat away) as much as keeping the heat in. We have noticed a big difference in heat retention after competing installation of both Rockwool and beads (since they were done at the same time). From the readings on the ventilation system which shows both room and roof space temperature compared with outside temperatures with no heating, the room temperature has been 5 degrees or more warmer than outside and roof temp in the mornings. And that is without curtains since we had them down for plastering and only just finished painting last week. Before insulation often the house temp was similar to outside temp at 7am.
It was definitely worth the effort as it only cost about $500 to do the whole house however it took a lot of time plastering. I did have to redo all the joins due to cracks in the walls as the original build didn't use tape and joins are in wrong places but these weren't due to insulation just other work that needed to be done. If I were doing it again with walls in the same condition and had the money I would pull out all the old Gibb, put in batts and re-line. That would have been much faster as there would have been less plastering work. If the walls are in good condition with good Gibb already, I'd probably blow insulation into the walls again.
Thanks again for the info and have a great day.
Steve, Rotorua

15 June 2011 - New compressor and Rockwool update

Some days our amateurism is more evident than others...

New compressor

On the weekend I bought a slightly gruntier compressor via TradeMe. It's a cheap "Euro HP-3.0" compressor normally sold by SaveBarn in Auckland. I tested it's power rating with my Kill-a-Watt power meter and got a maximum reading of 1960 kW which is 2.2HP. It has a regulator (our previous compressor didn't) and it recharges it's 50 litre tank in 144 seconds, compared to 193 seconds for the old one.

However - when I opened the water bleed valve at the bottom of the tank, a lot of rusty water came out. I'm guessing the previous owner may have never bleed the water. You're supposed to do that once a week or so to prevent the tank rusting from the inside. So, my recommendation is - if you're buying a second hand compressor make sure you bleed the water release outlet and don't buy if their is a lot of rusty water.

And today we discovered that it has a crack in the regulator block. Grrrrr.

We also discovered that if you turn this compressor almost upside down to examine the crack - all the oil in the motor drains out.

It was a classic amateur error. Sigh

Rockwool granulated settling

According to the AIS Granulated Rockwool Data Sheet "Granulated Rockwool, correctly installed, will not settle or blow around in a confined ceiling space."

Our experience this afternoon suggests either we are not "correctly installing" it, or it is sub-optimal as a wall insulation. Note: we're using a DYI approach that you can do yourself with cheap equipment - so perhaps a professional would get better results?

Here's what happened:

First we tried blowing the Rockwool in to the test box at 60 PSI - this was partly to test our new regulated compressor. We were curious to see if 60 PSI would be enough to do anything. It kinda worked, but took 6 mins 20 secs to "fill". It was very loosely packed. A corner of the box was left empty. As I moved the box around the Rockwool slumped leaving a gap at the top of the cavity. That's not unexpected when we were blowing it in at such a low PSI. I banged the box on the floor to compress the Rockwool even more.

Then I ramped the compressor up to 100 PSI and blew in some more to fill.

That's a lot of slumping.

You'll notice the blower clogs a few times. Then I pull the gun out of the hole, stick my hand over the end, and pull the trigger for a instant to blow the obstruction back down the line. Then plug the gun back in and carry on. This is a useful technique when blowing polystyrene thru a small (eg 19 mm) hole too.

Next we tried sucking out the Rockwool - it wouldn't budge. Our blower sucker running at 120 PSI could not extract anything. (Bloopers one and two.)

So the lessons are:

  1. Blow it in at the highest pressure your compressor can muster (although I'm not sure about pressures above 120 PSI though).
  2. With this equipment it looks like we may not be getting enough density to constitute "correctly installed" - so it will settle.
  3. With this equipment you can't suck the Rockwool back out. But - if you did open the wall it won't fly around the room like polystyrene - it'll just sit in place.

Having said all that - I'm still planning on adding Rockwool to the 4 segments of my one house that have electrical wiring and I'd left empty. If I was really obsessive I'd revisit the Rockwool segments a year later to top-up.

This reminds me that polystyrene beads fill the cavity and don't settle (at least when viewed with a high-end IR thermal imaging camera three years after installation.)

It also makes me wonder how hard it is for even a professional installer to "correctly install" Rockwool? Is it quite tricky to avoid settling?

We finished the day by blowing some more Rockwool into the one segment of wall on this side of the house that has electrical wiring.

Here's a view of the sucking end of the hose, showing the Rockwool granulated "de-clumped" in a plastic bucket.

Expanding foam hole filler

We finally got round to using the expanding foam to fill another dozen holes from previous sessions. They we're all filled with polystyrene bead weeks ago.

Here's the result:

Expanding foam hole filler

It's not that pretty. We haven't got the hang of under-filling the hole and then letting the expanding do the rest. What you see here is excess foam oozing out the hole. We'll let those dry and cut off the excess with a long bladed craft knife.

The foam keeps expanding for several minutes so you have to be very restrained - squirt in much less than you expect. A bit more experience should be enough to get the knack.

8 June 2011 - Building Consent?

According to our friends at BRANZ the building regulations were changed late last year to require building consent for any insulation work on exterior walls. That would even include Pink Batts.

David went in to the Wgtn Coty Council last week and asked if he needed a resource consent. I went in to the Hutt City Council this morning and did the same.

Both officers said something along the lines of "I'm not telling you not to apply, but..." and then listed reasons not to bother:

  • wall insulation in the form we're doing is hardly a "change" to the building - it's trivial
  • it'll cost more for the consent than it's worth bothering about

We're keen to press on regardless so that others can learn/copy from our example (or chose not to).

I'll keep you updated on how that goes.

3 June 2011 update

Our supply of beads has stalled (PolyPalace has a higher priority customer) so we're working on other things at the moment.

I've made a up a 25 mm diameter funnel for the blower so we can test to see if that's a good compromise between flow rate and hole size.

And that caused me to make this pretty chart (which will look better once I've got a third data point):

This understates the time of the smaller 19mm hole in real world use because every couple of minutes the beads would block at the end of the funnel, which required me to clear the blockage, then continue.

But - the smaller holes are (a) easier to drill and (b) easier to seal off.

22 May 2011 You Tube surfing

Just been watching some wall insulation videos on You Tube (as one does) and found some interesting ideas in this one from USA:

  • Lead safe - this installer goes to great lengths to make sure his hole drilling avoids letting any lead flakes/dust from interior wall paint getting loose inside the house. I've been assuming we're dealing with non-lead based paints on our walls.
  • [2:00 mins] They also insulate one cavity in any "T" walls (interior walls that join the exterior wall). I'd never thought of doing that. I wonder if it makes any measurable difference?
  • [3:00 mins] 2.5 inch holes - that's 63.5 mm diameter! So our 32 mm ain't that big. My guess is they're using that size because it allows them to pump the insulation (dense pack cellulose) in very fast. In the UK they seem to be drilling 22mm diameter holes mostly.

18 May 2011 - blowing Rockwool granulated

CSR Bradford Rockwool granulated

We had our first go at blowing Fibertex Rockwool Granulated. It comes in a 12.5kg bag measuring 1m * .6m * .2m, fits in the back seat of a small car, and cost me $45 + GST from Potters Interior Systems Limited in Petone (they have branches elsewhere).

Rockwool granulated - instructions on the bag.
Health and safety information - click to enlarge

Our process:

  • grab a handful of Rockwool from the bag and put it into a plastic 60 litre rubbish bin
  • "decompress" the handful/clump with our fingers (wearing rubber gardening gloves) by just pulling the clumps into smaller and smaller clumps. Ideally to the point where there are no clumps.
  • then blow it in to the wall straight from the rubbish bin.
Hand loosening Rockwool granulated.


  • It works fine with our blower gun and the 2HP air compressor
  • It really looks a lot like wool when it's still in the bag.
  • This process did not generate any visible dust or particles.
  • The Rockwool seemed nicer to handle than fiberglass "Pink" Batts.
  • The end result of our "de-clumping" was still a bit clumpy.
  • It generated a lot of static electricity which we hadn't observed with the polystyrene (our friend Ian has experienced static with polystyrene though).
  • It blows in slower than the beads - maybe 2 or 3 times slower. [I'll do a timed run with my demo/test box at some stage.]

We blew in about 40 litres worth of de-clumped Rockwool. This equated to about 1 metre of a single column.

For David's wall the calculations went like this:

.1m (wall cavity thickness) * .4m (approximate distance between studs) * 1m height = 0.04 cubic metres

0.04 * 1000 = 40 litres

The rubbish bin had a .4m diameter. So a radius of .2m (actually it got wider toward the top so the calculations should be for a dissected cone, but this will be close enough).

π (pi) * 0.22 (radius squared 0.2 * 0.2 =0.04) * 0.32 (depth) = 0.040 cubic metres = 40 litres

[I worked out the depth (0.32m) in a lazy/ugly "non-maths" way. I used Excel to create a list of numbers 0.01, 0.02, 0.03 etc in column A, then in column B entered the formula =A1*PI()*0.2^2*1000 and replicated that down a page, then saw that at row 32, A32 was 0.32 and B32 was 40.21 which was the desire volume. I should be able to re-arrange the formula for 40 litres and just get the answer - but I can't remember how to do that - and this way gives the right answer.]

So 0.32 metres (320mm) up the side of the rubbish bin = roughly 40 litres, which should fill a section of David's wall up to about 1 metre.

We filled about 1 metre then ran out of time today.

The whole point of using Rockwool is it is very inert (it's made of 95% rock). It does not react with electrical wiring insulation - unlike polystyrene for which there is research indicating wiring insulation may go brittle over time.

If your wiring comes in to the wall from below then there's the possibility of filling the first 1 metre of wall segment with Rockwool, then filling the rest with polystyrene (which is cheaper and faster to fill).

If your wiring comes in to the wall from above then you'll need to fill the whole segment. Either way you'll want to know how much de-clumped (uncompressed) Rockwool you've blown in to the wall - so it's worth sticking a length of masking tape up the inside of your rubbish bin and marking the volumes at various 10 litre intervals.

If you have a rectangular rubbish bin the volume calculations are a bit easier; width * depth * height.

Cheers, Paul

PS. Anyone with better maths skill is encouraged to send me the formula for working out the correct depth of a cylinder of r=0.2m and 40 litres volume.

16 May 2011 - estimating costs

I've made up a spreadsheet for estimating the total costs.

It's still a bit rough:

  • it doesn't include using Rockwool granulated for sections of wall that contain electrical wiring
  • the formula to estimate volume of polystyrene beads required is based on David's house thus far, but the same formula doesn't tally with the amount I used for my house (even adjusting for the different wall size). My house only took 4 cubic metres of polystyrene beads whereas my calculations suggest it should be closer to 9 m3. Need to figure that out.
  • We haven't done a house with dwangs, so I don't know what that will do to the time estimates. At least with a wall that has dwangs you're unlikely to have hardwood sarking so the drilling will be much easier and faster.
  • The cost for IR thermal imaging is based on a 2010 quote of $400 for my 90 m2 house.
  • I've got an entry in the expenses section for time/labour - for a DIYer it's at zero. It's interesting to play with that number to see what it takes to equal the Airform quote (they don't include IR thermal imaging).

Rockwool granulated experiments

We're picking up a 12.4 kg bag, (1 x 0.6 m size), of Rockwool granulated for $51.75 this week and I hope to play with it on Wednesday.

Rockwool does not react with the insulation around some electrical wires the way polystyrene may.

11 May 2011 - progress on David's house

David and I spent another afternoon on his lounge wall.

This time we were drilling the larger 32mm holes.

I first tried a new tri-bit (like a spade bit but with three cutting "wings") - which was a nightmare. It's fast and clean drilling through Gibb, but the moment I hits the hardwood sarking (we think it's totara) it grabs and jambs, causing the electric drill to fly around in my hand! I suspect the tri-bit is design for a hand brace, not electric - so it mau have been a stupid selection on my part.

So David popped out and bought a standard $12 spade bit. It's much less dangerous, and worked fine on the first hole. Subsequent holes were a lot harder to get through though. It looks like cheap spade bits are good for not much when it comes to New Zealand hardwoods. This is the same experience I had drilling 35mm holes in my home back in 2006-2007. The best I caught get was about 9 holes before the bit was stuffed. My feeble attempts at resharpening the bits were not successful.

Anyway - we persevered and drilled 5 holes to complete the south side of his long lounge wall.

We then filled 4 of those in less than an hour - including stops for general mucking about. If we're focused on the task we could have completed them in less than 30 minutes.

There was also a cavity with a 19mm hole that needed filling. It took ages - maybe 20 minutes, including several stops to wait for the compressor to recharge, plus a couple of stops to clear out blockages due to miscellaneous over-sized bits of polystyrene.

Also - as the pressure fades away the bottom side of the clear PVC feed tube gains a layer of non-moving beads. The lower the pressure the deeper that layer becomes until a threshold is reached and the tube gets blocked with beads. Then you have to wait for the compressor to recharge it's tank and tap the beads in the tube back down into the bag of beads. Then you can continue.

You could solve that problem by using a more powerful compressor.

We're completely sold on the full bore 32mm holes when using our current 2 HP compressor. If we have a gruntier compressor we might get away with smaller holds.

Other notes:

  • David's ceiling is 3.3 m high (11 foot)
  • a full height wall cavity is 400-425mm wide * 3300 high * 102 mm deep = 134-143 litres
  • the spacing between studs seems to vary considerably
  • we're drilling out holes 125 mm from the ceiling
  • a 1850mm section (above a window) of about 56 litres took 48 seconds to fill. That's about 70 litres per minute.
  • during a fill of a full height 3.3 m section the compressor ran out of puff once, requiring several minutes for the compressor tank to recharge.

One other advantage of the 32mm hole setup is that the gun can be jammed in to the hole and left there - you don't need to keep holding it up - which is really tiring. The cheap flexible funnel/nozzle that provides us with a 19 mm hole output requires you hold one arm up above your head for several minutes at a time - not fun.

If you jam the gun into the wall "all the way" it will force the trigger "on". This allows the process to be done with just one person. Make sure you have the inlet end of the clear PVC hose not buried in the beads before you try this trick, or their won't be enough air flow to get the beads flowing. So - then you use one hand to move the inlet tube into the beads and keep it moving in a small circular motion to ensure a consistent mix of beads and air. As you're doing that watch the beads flow into the wall.

As it is the process works fine with a cheap 2 HP compressor - but what difference would a high quality 2.5 HP or 3 HP compressor make? (That's the biggest you can get that will plug into a standard mains plug. Bigger than that and you either need 3 phase power or a petrol engine.)

So by the end of a afternoon we'd completed south wall of the lounge except for one section which contains electrical cables coming up from the floor. Our plan is to try Rockwool Granulated in that. It's more expensive, but doesn't have the issues with wiring that polystyrene does.

10 May 2011 - building consent requirement

I've just be advised by a friend in the building trade that at the end of last year the New Zealand Department of Building and Housing introduced a requirement that all retrofitted wall insulation requires a building consent. Building Inspectors will have no trouble signing off on Batts but it will be more challenging for them to inspect blown products – especially given that it is not as easy to inspect the wall cavity and building paper.

8 May 2011 - More blower testing

I'm going to demonstrate the blower setup to a Transition Towns Lower Hutt meeting this Tuesday so I tidied up my test/demo wall segment box and ran a few more tests.

I changed the "filter" setup around the back of the test box to remove any gaps. If you look at the fill test did on 4 May 2011 you'll see a little puff of beads jet out the left side. That's because the filter consists of a roll of loose knit fabric held in place with length of aluminium with holes in it. I've done a tidier job on it now.

It was just me this time so everything took longer as I faffed about with the stopwatch, gun, hose, bag of beads and test box.

I'm using the same Adendorff air compressor as on 4 May 2011. It's 2hp, 7.3 CFM, 206 litres/min, 115 psi and has a 50 litre tank.

The test box is 112mm x 500mm x 500mm = 28 litres.

All the tests were with 32mm holes.

Test 1. Filling box

34 secs. I fluffed about a bit the first time.

Test 2: Extracting beads from box

About 2 mins. I had to stop and make sure the bag end of the hose was not buried in the beads, because that prevents air flow - which prevents bead flow.

So the lesson is: when extracting beads make sure the end of the hose is clear of anything that might impede air flow.

Test 3: Filling box

26 secs. That was a good run.

Test 4: Extracting beads

32 secs. Another good run.

It's looking like the extraction could be about the same speed as filling if there's no mucking about by the operator.

In a real home you're not likely to need to extract the beads in the next 10 years - but it's nice to know the process is easily reversible.

The most likely scenarios are if you want to add an electrical outlet somewhere or put a new window in a wall. In those situations you can suck out the beads from the one/few segment(s) of wall in less than an hour.

5 May 2011 - Polystyrene vs electric wiring real-world test

As mentioned previously - polystyrene can react with some of the plasticizers used in the plastic cord that surrounds mains electric wiring. The reaction casues the plastic coating around electrical wires to "melt" or become brittle.

So I'm going to test what that might mean in real life. Does the fact that I'm using recycled beads affect the "melting" process? Does the fact that I'm using a 5-year power cord affect the process? Does the temperature matter? Does the current in the wires change the process? Are there thresholds below which the "melting" does not occur? Let's find out!

Web server power cord in a bottle of recycled polystyrene beads.
Web server power cord in a milk bottle filled with recycled polystyrene beads.

Here's the power cord for the web server that runs this site - stuck in to a plastic milk bottle filled with recycled polystyrene beads. I've now plugged it back in to the server and it's running. This a nice test because the load is steady and known. I used a Kill-a-Watt meter to measure the Compaq Proliant DL360 server load - it consumes 0.56-0.65 Amps at 230 VAC, 89-119 Watts, or roughly 2kW/hrs daily. It's running 24/7.

If I was being really careful I'd have built a little box made from materials you'd expect to find in a wall. But I can't quite be that bothered. I'm really looking to see if there is any noticeable effect.

If the plastic of the milk bottle does react with the polystyrene or power cord I expect the reaction would be highly localised. I'll be looking out for that when I pull the cord out to inspect it.

My current plan is to give the setup a brief visual inspection (without removing the cord) every morning to make sure nothing dramatic is going on.

Polystyrene vs power cord test - running.
The polystyrene encased power cord in position - tucked under the web server.

Once a week I'll pull the cord out for a closer inspection then stick it back in the bottle. After 4 weeks I'll reconsider whether to continue the experiment further or not.

Geek note: the Compaq Proliant DL360 server that runs this site cost me $35 on TradeMe last year. (It's got twin hot-swappable SCSI drives and hardware RAID!) My first one got water damaged (it's sitting up in the garage rafters) so I've now got two spares. It's downside is it's noisy.

Thursday 5 May 2011, 9amWeather 14 degrees C, Humidity high (probably 75%).Start of test. The bottle is located in our garage (which is "mostly waterproof") on a shelf beneath the web server. It is not in direct line of the server fans airflow. The cord is a standard off-white coloured computer cord. The surface of the cord is smooth with no signs of dimpling anywhere along it's length.Power cord condition on 5 May 2011, 9am.
Sunday 8 May 2011Rainy but warmIt looks fine.Couldn't be bothered photographing it yet.
Sunday 15 May 2011OvercastIt looks fine. No obvious signs of anything going on yet.No photo
Friday 24 June 2011 (6 weeks)Cold overcastI pulled the cord 90% out of the bottle and inspected the cord visually and with my fingers. It didn't feel sticky or brittle. It looked exactly the same as the cord left outside the bottle. Nuthin' to see here folks.Power cord condition on 24 June 2011, 9pm.
TPS power cable Update 16 May 2011: I had a conversation with an electrician who reminded me that the insulation around wires comes in many different varieties - so it's quite possible my computer power cable is made from plastic that does not react with polystyrene. What I should probably do is make up a short extension cord using the sort of mains wiring you find inside walls. Given that BRANZ are going to do a study on the same issue - I may not bother.

See also: - what happens to old home computer wireing stored in their original polystyrene box

4 May 2011 - Testing wall cavity box with 32mm hole experiment

I fixed the problems with my demo wall cavity box by adding a trim of fabric around the back rim. That lets enough air out to allow the blower to work. In a real wall there are enough gaps between wall cavities to allow airflow.

On the first test run we used our standard 19mm hole setup. It took 94 secs to fill the 28 litre cavity.

Then, following a suggestion from Steve (see below) that we try a larger hole size - we did a second test using a 32mm hole (the outside diameter of the Pneu Vac gun).

Here's what happened:

That's 28 litres in 20 seconds. 4.5 times faster than the 19mm hole setup.

Steve also suggested we check the compressor was set to blow at maximum power. It turns out our compressor does not have a limiter - so it's always going 100%.

Here's the extraction process:

We had to fiddle about a bit because I'd left the donut of plywood from drilling the hole and it blocked the gun. Our conclusion was that if you wanted to extract beads from a wall cavity at some stage you should drill your hole as close as possible to the bottom of the wall cavity. In the real world you're very unlikely to be extracting beads - but if you want to it's pretty straight forward too.

[In later extraction test I got the time down to 32 to empty the box.]

Area of a circle

Here's the area of the different hole sizes. I've assumed the funnel has a thickness of 1 mm so the diameter that the polystyrene flows thru is 2mm smaller.

Drilled hole dia. (mm)Area (square mm)Test box fill time (secs)Comment
1922794Blockages occur every few minutes.
3270720No blockages. 4.7 times faster than the 19mm hole. 3 times larger hole area.

I'll test a 25 mm hole at some point.

26 April 2011 - Blowing Rockwool instead of polystyrene beads

Just received this email from a reader:

Steve blowing Rockwool in to his walls
Hi Paul
I got the Vac-u-gun sometime ago and finally got to try it out after picking up 7 bags of beads while in Wellington last weekend. I was surprised by your problems with compressor size - mine is a cheap small GMC unit and has worked fantastically. The specs on mine are 24 ltr, 1500w, 206 l/min, free air delivery 117 l/min. It will fill a 23l cavity in what feels like less than a minute with beads, haven't timed it but very fast.
Originally the first cavities where slow to fill but the regulator was set too low, after adjusting this up to 80psi the beads just zoom in. The main differences to your setup are, I have 32mm holes in the walls, there is an 8 metre rubber air line hose to the compressor (this adds a little capacity and pressure on first pull of trigger due to expansion of hose) and a US made Vac-u-gun. I think it is the 16mm holes giving you the problem as it is restricting the flow.
I have solved the problem of cavities with electrical cabling. I am using Bradford Granulated Rockwool, also known as Fibertex Rockwool Insulation, comes in 12.5kg bags. This is the stuff they blow into roof spaces for insulation, we have it in our roof. It transfers perfectly with the Vac-u-gun. This is one of the reasons I'm using 32mm holes in the wall to make it easier to transfer the Rockwool.
It's a two person job. One person has to pluck at the Rockwool to loosen it up so it can be sucked up the tube as it is packed very tight in the original bag. One way to improve on this would be to transfer quarter of a bag at a time into a drum where it could be stirred up with a fork or something to loosen it up. The Rockwool is about $40 a bag and we fill just over nine 23lt cavities with a bag. It's more time consuming than the beads as it's slow, however still faster and more cost effective than pulling the linings down and putting batts in the sections where cables run. Of course you need to know where all the cables go in the house, which is easy to tell in our place as they all come down the walls from the roof space.
Steve, Rotorua

And then a follow-up:

Most compressors will have two gauges and outlets. One has a regulator with a knob on it that controls the pressure to the outlet, the other is unregulated and the gauge shows the pressure in the tank. Plug the gun into the regulated outlet and pull the trigger, you should see the needle on the gauge drop down to what ever the regulator is set to. Holding the trigger and adjust the knob to obtain the pressure/flow you desire. This is to enable using different tools, paint guns only need 10-20 psi, air grinders 90psi. The little compressor you tried originally should do the job just fine.
I get the Rockwool locally from Best Insulation Rotorua, I think they said they get it from Tauranga. Might be from this place Initially I just rang round the insulation installers to find out who used it and would sell a bag to me to try out.
Make sure you ask for the granulated Rockwool. Not the stuff that's like Pink Batts.
Steve, Rotorua

14 April 2011 - CO2-e savings

I need your help! I'm trying to work out some way to quantify the CO2-e saving that might result from doing wall insulation.

I've been Googling it for a while now and still haven't managed to find any good papers that link home insulation with actual quantities of CO2-e that might be saved.

It seems safe to say that a home with good insulation will require less heating compared to an equivalent home that is not insulated (assuming the same desired interior temperatures).

I'm sure someone else has gone in to the details of trying to work this out. I sure hope so! Because as soon as I start to think about the variables it becomes a non-trivial task.

From a strictly personal perspective, having been obsessively collecting my household electricity usage data I know that:

  • in 2004 we used 3262 kWh (per person) of electricity to heat and run the house
  • in 2010 we used 2416 kWh (per person) of electricity to heat and run the house

Between 2004 and 2007 I did all my major insulation projects (drafts, ceiling, underfloor, and walls, etc).

So that's a difference of 846 kWh per person or 2538 kWh for the household. And that equates to 355 kg CO2-e according to the CarbonZero household calculator.

How much of that can be attributed to the wall insulation alone?

According to this:


A whopping 35% of the heat loss in an uninsulated house is through the walls.

Does that mean that 35% of the 2538 kWh electricity savings are from the wall insulation? The would be 888.3 kWh or 124.36 kg CO2-e savings per year. (For comparison our current household CO2-e emissions, as calculated using CarbonZero, is averaged 181 CO2-e per month in 2010.)

I suspect I've grossly oversimplified the situation so I'm not too confidant in the quality of that final result - but it's a start.

What have I missed? Email me

I did also find this: - Attach:Energy_Savings_Wall_Insulation.pdf Δ (PDF) which came from a 76 page paper Energy Saver Fund Technical Manual Review produced for EECA by Energy Solutions Ltd back in 2004. Which includes:

 LocationAnnual SavingsLifetime savings
  kWh/yr.m2$(disc.)kWhkg CO2
Wall insulationWellington48.4$93968581

And there is:

13 April 2011

Spent another hour blowing beads into David's wall. We drilled 6 holes and filled 5. The last hole was above the side of the old chimney (which is hidden from the inside). The plumb revealed something odd at 1 metre above the floor level. We'll try to figure out what's going on inside the wall next time.

Last week we filled and foam plugged about half the wall. Here's how they look now.

Six 19mm holes in top left corner of the lounge. I left the flash off when taking this photo to show how hard/easy it is to see some of the holes. This is before they have been sanded, plastered and painted.

These are all full of poly beads and then the hole plugged with expanding foam. The foam was allowed to dry then the excess trimmed off with a craft (box cutter) knife.

Next step will be to sand them back, plaster over to smooth, then paint over them.

7 April 2011

ECCA have approved some funding from BRANZ to conduct tests any possible reaction that may occur between polystyrene insulation and electrical wiring.

I'll keep you posted on what transpires.

Here's some background to this issue:

Commonly used PVC plasticisers tend to exhibit solubility in polystyrene and polyurethane insulating materials, As a result of this there will be migration of plasticiser from the PVC compound where there is a direct contact between the two materials, this causes the PVC on the cable to become harder and more brittle. There is also potential for plasticiser migration into bituminised building paper, causing the bitumen to soften and flow. More...

My building expert friend notes that there is currently very little research on this. He thought there actually be just one scientific paper, in which the ran hung an electrical cord over a block of polystyrene and ran a constant current through it for the equivalent of 10 Amps running for 50 years.

My friend also wondered if the effect occurs in a linear fashion, increasing the damage steadily over time, or does it all happen in the first week then taper off? Does the reaction occur in "old" recycled beads or just new beads (which retain more of the chemicals used in the beads manufacture)?

And I'm thinking - I don't have any appliances that run at 10 Amps 24/7 for 50 years. Some examples:

  • the web server this site runs on is running continuously at 89 Watts at 230 Volts AC = 0.37 Amps
  • my fridge/freezer runs 225 Watts when the motor is running, so that's about 1 Amp. But the motor only runs in cycles. Over a whole day it uses 1894 Watts, or 1894/24 = 79 Watts, which means an average of 0.34 Amps. [Please tell my if I've got my maths right/wrong here? Paul ]
  • my oven is probably about 3kW so that's 13 Amps, but again we don't run that 24/7.
  • my heat pump peaks at 2740 Watts = 11.9 Amps. We have been known to run that all day in the weekend in mid winter.

Incidentally - I use a Kill-a-Watt (version 2) meter to measure the power consumption of our appliances. Here's my latest raw data.

Anyway - hopefully the new research from BRANZ will give us a better picture of what the risks are (or aren't).

25 March 2011 - lists

Parts/tools list

ItemsSourcePrice (2011)Comment
19 mm drill bitMost hardware stores$20I'll assume you already have a drill
Stud finderAny hardware store$25 or more 
Clear PVC hose (32mm dia x 200mm)Some hardware stores$12/mI got mine from Mitre10 Mega in Petone
PnueVac Vacmaster 22 blower/vac gunIndustrial Tooling Ltd$50 + $9 courier 
Polystyrene beadsPolyPalace (Porirua)$25/cubic metreMy 90 square metre house took 4 cubic metres to fill the walls.
Ribbed anti-static vacuum cleaner hose$1 Buy second hand from rubbish/junk shops
Can of expanding polyurethane foamHardware store$10 or more 
Air compressorTool shops or equipment hire$800 to $1800Hopefully you can borrow one from a friend
Vacuum cleanerAppliance stores$100 to $500You probably already have one. Used for cleaning up any mistakes
Infrared thermal imaging $300 quote for my small houseHire a service to validate your insulation


  1. Wooden cavity walled house (with no insulation in it)
  2. Permission (are you the owner of the house?)
  3. Located close enough to PolyPalace or other source of used polystyrene beads
  4. Time and inclination to do the job yourself
  5. Decide whether to drill form the inside or out side. If drilling from the inside then I recommend you clear everything away form the wall before starting. Doing it from inside means you can work at any time of day and in any weather. Doing it from outside may mean less interruption for other householders (you won't need to move their stuff around).
  6. Decide if you're going to risk blowing beads into segments of wall which contain mains electrical wiring. See discussion: polystyrene melting electric wiring. I chose not to for my house - I left all those segments empty - I'm hoping to eventually find a suitable cheap & effective re/solution. Fortunately for me I only had 4 segments with wiring in them, all the rest of my house wiring is in interior walls.

The process

  1. Start with a room/wall on the south side (the side that gets the least sun) of your house. (In the northern hemisphere you'd start with a north facing room/wall.)
  2. Identify where in your exterior walls your house wiring is running. In most houses most electrical wiring is located on the interior walls - especially old houses. My house had just 4 places where there was mains wiring in the exterior walls.
  3. Use a stud finder to find where your vertical if you have horizontal "dwangs" in your walls. If you are very lucky you'll have a pre-1930's house which doesn't have dwangs. This will enable you to drill just one hole at the top of each segment between vertical studs in your wall. If you have dwangs you'll need to drill a hole for each compartment inside the wall (hopefully you have a good stud finder)
    • Start in either top left or top right corner of the wall. There should be a stud in the corner of the room (unless you're in a corner with a poorly built interior wall - all wall joins are supposed to line up with a stud). Move the stud finder horizontally, starting from a point about 100mm below the ceiling and 100m along from the corner. Drift along the wall till you find a stud. It should be somewhere between 400mm and 600mm out from the corner. Then mark a drill whole roughly halfway between the corner and the stud, and 100mm below the ceiling.
      Wall stud finder
    • Note: if you have an old house with sarking (horizontal wood planks on the inside walls) rather than dwangs (horizontal braces between the studs) you may find that a stud finder will register the gaps between each plank 200mm wide plank. This means you need to be careful when using a stud finder. (a) if you "set" it over a sarking board then drift up or down enough to pass over the horizontal gap - it might give you a false "stud" reading and (b) if you "set" it over a gap, then drift up or down a bit you may get a false "stud" reading. So - if you're finding the stud finder seems to provide semi-random results this could be why, or it's a cheap crappy stud finder, or you're not using it properly.
    • In the corner of my house there was a diagonal beam as well - which was confusing when I was only expecting vertical and horizontal beams.
  4. Once you've established where the studs are, mark your holes 100m down from the top of each wall cavity, roughly in the middle between each vertical stud.
  5. Drill the first hole. We used a 19mm drill bit which our plastic petrol can funnel fit in to nicely.
  6. Make yourself a "plump" to see how deep the wall cavity really is. We just tied some nuts (smaller than the hole) onto the end of a piece of string. Then fed that into the hole and kept feeding till be heard a "clunk". Hopefully you'll hear it hitting down at floor level. It's a good idea to mark the string with a black marker at this point. Then pull the plum out of the hole and see how far it hangs beside the wall. (Hopefully the bottom will be at floor level.)
    Wall plumb made with spare nuts
  7. Proceed to the bead blowing step, filling your first segment completely. Record how long it takes. Multiply that number by the number of segments you'll be doing. At this stage you can decide to continue or abandon the project (if you think it's all too hard). Or hire someone else to do it for you.
  8. If working from inside then drill all the remaining holes in your first room then cover them with masking tape. If working from outside then drill all the holes along the south facing wall then cover them with masking tape.
  9. Blow beads into each segment
    • stick the funnel into the hole and hold the gun with one hand.
    • stick the end of the intake hose 250 mm into the bag of beads and use a piece of string or short bungee to seal the top of the bag around the hose.
    • turn the air compressor on and wait for the pump to finish pumping air into it's tank.
    • hold the intake hose at the top of the bag and lift the intake hose up above the beads inside (this provides the blower gun with enough air to get the suction started).
    • squeeze the blower/vac gun handle and hold it.
    • use the end of the intake hose to "giggle" the beads in the bag - to flow smoothly the systems needs just the right combination of beads and air. You'll get better at this technique after you've done a few segments. [Incidentally - this step is probably the biggest technical challenge for commercial "blown insulation" systems. That's why you'll see them have large hopper boxes at the intake. We've chosen to avoid that challenge by simply giggling the intake hose to aerate the beads.]
  10. Inside: Seal each completed segment hole with a little squirt of expanding polyurethane foam.
    Outside: Seal each completed segment hole with [something weather proof].
  11. Repeat for the rest of the house.

Polystyrene R-values

I don't know how to realistically measure the R-value of loose polystyrene beads in wall cavities.

As a rough indication:

  • EXPOL underfloor polystyrene blocks quote R 2.3 to R 2.7 for a 100mm (4 inches) thick block.
  • Smarterhomes info on polystyrene insulation: Approximate R value for 100mm-thick polystyrene is 2.5 to 3.0.
  • 150mm Concrete = R0.09
  • 50mm Timber (12% moisture content) = R0.42
  • 90mm Pink Batts Ultra fibreglass insulation = R2.6 to R2.8
  • 95mm Terra Lana wall sheep’s wool insulation = R1.8 to R2.4
  • Try the Construction R-value Calculatorsulation Guide]]
  • BRANZ House Insulation Guide

My guess is; loose polystyrene in a wood framed wall results in an overall wall R-value of about 2 (including losses from heat conducting thru the studs).

What have I missed? Email me

24 March 2011 - fire test

One of the questions I get about the idea of using loose recycled polystyrene beads in wall cavities for insulation is: is it flammable? Does it behave like cheap foam couches which burn really well?

Here's a quick test to see.

The short answer is: yes it does burn with enough heat and oxygen.

Of course - the fire has to get though your wood walls before it can ignite the polystyrene beads, plus there shouldn't be that much air inside the wall cavity left to help feed the fire because the space is full of polystyrene. So burning insulation might be the least of your problems if you get to the point where they are actually burning.

Update 31 March 2011

Just found this: Guidelines for the use of expanded foam polystyrene panel systems in industrial buildings so as to minimise the risk of fire (79 page PDF, 2376 KB) By R.J. (Bob) Nelligan, Fire Engineering Research Report 06/1 2006, a project submitted in partial fulfilment of the requirements for the degree of Master of Engineering in Fire Engineering Department of Civil Engineering, University of Canterbury.

Note: this report is about polystyrene panel systems - not loose beads inside a standard wooden house wall. The key difference is polystyrene panels are exposed to more fire risks and provide a fresh air surface to support ignition. Nevertheless, there are some good issues raised that it is worth dealing with.

Highlights include:

  • A review of New Zealand Fire Service data from the last four years shows that the major causes of fires in buildings containing EPS remain unchanged. They are: electrical faults, heating from solid fuel equipment, and hot work (welding gas cutting, braising). Electrical faults are twice as likely to start a fire than any other cause.
  • over 750,000m2 per annum of EPS is produced in New Zealand
  • In general there are two commonly used grades of expanded foam polystyrene. Standard, and flame retardant. Standard grades are used widely in the packaging industry. Electronic equipment such as computers, telephones, and televisions are packaged for shipment and distribution using polystyrene. This product is easily ignited and burns readily although the heat release rate is low as there is a high ratio of air to polystyrene mass in the expanded form. This occurs at 285-440°C when the decomposed or depolymerized flammable materials including styrene ignite. The 16

flash ignition temperature is given as 345-360°C and the self ignition temperature as 488-496°C. [APME “Fire Behaviour of Expanded Polystyrene (EPS) Foam”. Rev. 1 18/12/1992.]

  • Flame retardant grades demonstrate different behaviour when exposed to temperatures above about 100°C. The EPS commences to soften and shrink, melting away from the heat source, until it is reduced to its original density prior to expansion. On further exposure to heat above about 200°C, gaseous combustible products are formed by decomposition of the melt. However at these temperatures if ignited with a flame, the EPS extinguishes itself as soon as the ignition flame is removed. ... Typical flame retardants include such complex compounds as hexabromobutene and hexabromophenylallyl ether. What should be noted, is that in such small proportions, these flame retardant compounds can easily be overwhelmed in a large fire to the extent that they will only slow down the fire growth until they are expended. It is also possible that after a prolonged period (years) of exposure to even modest heating, the flame retardant compounds lose their effectiveness. EPS will eventually burn provided it is in the presence of a large ignition source or a significant heat flux of at least 50 kW/m2 (7). Pilot ignition temperature is 320-380°C. In the absence of a pilot flame the self ignition temperature is 450-510°C. [Flammability Handbook for Plastics. Technomic Publishing Company Westport Connecticut 3rd edition 1982.]
  • EPS has one other insulating property that is often overlooked. Just as it is used to keep heat out of a cold store, it is also equally capable of slowing the rate that any heat generated can escape by conductive or convective means from an enclosed cavity. Thus a heat source surrounded by insulating polystyrene, may increase the compartment temperature in comparison with a non-insulated scenario.
  • For over ten years it has been mandatory to use a flame retardant grade of EPS in the construction industry. The flame retardant conforms to AS1366 Part 3 – 1992(8) It reduces the flammability and spread of flame on the surface of EPS products to such an extent that it is classified as “flame retardant” according to the European DIN Standard 4102(9).
  • While in the last 25 years the method of construction of these types of buildings has changed, the ways that they catch fire has not substantially altered. As will be seen in the New Zealand Fire Service Data and in the selected case histories, electrical fires, fires caused by hot work (welding, braising, gas cutting, grinding etc) and fire spread from overheated machinery are the major contributors.
  • Do not rely on plastic conduit to separate electrical cables from foam.
  • Do not mount electrical switches on EPS panels so that the body of the switch penetrates the metal skin of the panel.
  • Electrical panels, switchboards, and gas fired or electrically operated heaters should not be positioned directly against an EPS wall. An air gap should be maintained, or a sheet of fire resistive material placed between the equipment and the wall. Consider radiation effects particularly for long term exposure.

After reading this report I was left thinking:

  1. If one were to put loose polystyrene beads into a section of wall that also contained electrical wiring the highest risk areas would be in switches and at bends in the cables. This is were you might get small locations with high temperatures. In the case of a switch you might get momentary arcs - if your switch was faulty and was "almost off" you could get an intermittent arcing which could then ignite polystyrene beads if they were allowed to enter the switch box cavity.
  2. sprinklers are a really good thing.

And here's the Wikipedia entry on health and fire hazards. The concluding seems to be - make sure you use beads treated with fire retardant.

23 March 2011 - first run at filling test box

It took 3:33 to fill the box, which is 23.25 litres capacity.

Compressor specs:

  • 2 HP, 1.5 KW single phase electric (230VAC)
  • 7.3 CFM, 206 l/min {conversion}
  • 50 litre tank

This compressor works better then last weeks one (which only had a 25 litre tank) but is still under powered.

Lessons learned:

  • It's clear we still need a better intake system. We'll try to copy Ian's intake system. For the moment we just have to keep waving the intake tube around to loosen the beads and give the system enough air. This technique works - but it would be nice not to have to faff-about as much.
  • Need a better air compressor (see below).
  • I should have waited longer for the glue holding the perspex on to set. (Doh!) I've now added screws to hold the perspex on.
  • Ian recommends I should try a ribbed tube - which should loosen the beads up to provide better flow. He also suggested an anti-static tube would be better too.
  • This setup should be good enough for the talk I'm giving on Sunday.

David and I popped in to a few tool shops last week and found:

  • Powertool Shop (Lower Hutt): 3 HP (2.2 KW), single phase electric, 50 litre tank, 16 CFM for $1839
  • Tool Team (Lower Hutt): 3 HP (2.2 KW), single phase electric, 50 litre tank, 16 CFM for $1739
  • Hire Quip (Lower Hutt): 15 CFM, electric for $78 per day or $382 for 7 days, up to $949 for a month

So - theoretically, they'd provide twice the flow.

20 March 2011 - building a demo wall box

I'm giving a talk at next weekends Sustainable Home and Garden Show on "Tips for DIY Insulation". In order to demonstrate the blower I'm building a portion of wall with a perspex front.

[I'll add photo's and video when it's done. In the meantime you could watch this: ]

17 March 2011 - visiting a building industry expert

David ad I went to visit a friend who is an expert in the building industry. He's taken the basis idea of blowing in loose polystyrene beads and played with it in more elaborate ways than I can. His leaf blower system has double intake tubes and double outflow tubes, plus a remote on off switch. It works a charm.

We're going to try building a new intake based on his so that we can reduce the intake tube blocking. Currently we have to jiggle the intake continuously to get a nice steady flow. His system ads extra airflow down at the intake end.

In our general discussion he explained why, in the UK, where polystyrene beads are used a lot, they also add a glue. This is because their process is designed for double walled brick houses - which can have gaps and ventilation openings - so using a glue avoid the beads drifting out of the walls. In our case we're blowing the beads into wooden houses which seldom have ventilation openings. However, when I was doing my own house (in my case, from the outside) a few gaps between wall boards became apparent as I was blowing in the beads. I just squirted some silicon sealant into the gap, gave it a few minutes to dry, then carried on blowing the beads. I was grateful for discovering the gaps - because they would have been points of extra heat loss in winter.

We gained a bit of insight into how the New Zealand insulation industry works. A lot of the profit, here in New Zealand, is made by product wholesalers. Installers tend to be earning the minimum wage. In other countries there's enough competition between insulation material providers that the product prices are lower.

This dynamic may mean we get a lot of low quality insulation installations. This is important because the experts tell us small gaps in insulation degrade the overall performance more than you'd expect. [Source needed.]

Late last year I helped install some irrigation tubing under the Alicetown Community House. It had solid polystyrene block insulation installed. These were wedged up between the joists under the floor and held in place by friction fit. I'll bet the installation was remarkably fast and very cheap because - roughly 10% of the blocks had dropped out and were laying on the ground. It's effectiveness is probably close to zero.

If you do the job yourself you will be able to make sure it's done really well. Having said that - it's a horrible job and you'll probably hate it - so I know exactly why you might choose not to.

You should ensure the blocks are really tightly wedged in - or better still, fix them in place somehow. In my house I added a vapour barrier (aluminium foil) under the blocks and held it all in place by stapling packing strap under that. You can also get plastic brackets to nail the blocks in place. I prefer my solution because it provided two extra modes of insulation; vapour barrier and heat reflection.

So if you are given a quote for installing insulation and are amazed at how quick and cheap the installation portion of the quote is - be wary. You may get a crappy installation.

This industry dynamic also explains why the standard approach to retrofitting wall insulation in New Zealand is to pull down the interior wall cladding (and throw it out), staple in batts then install brand new interior wall cladding. That seems like a very resource hungry, time inefficient and expensive process to me.

But... I'm just an amateur.

Cheers, Paul

3 March 2011 - working even better

David and I got together again at his house.

We added a funnel to the end of the blower gun [photo soon] which ends with an outside diameter of 19mm.

Plastic 5 litre fuel can with yellow funnel.

The (yellow) funnel we used was from a "standard" 5 litre plastic fuel can (probably bought from The Warehouse). I cut off the lip, leaving a wide opening the same size as the nozzle of the blow gun.

I used 50mm of the clear PVC tubing (cut from the end of the main suction hose) to create a snug sleeve that joined the two, then I wrapped electrical tape over the ends to prevent air escaping.

I also cut the main suction hose down to 2 meters which makes it easier to handle and the beads flow better. This does mean that you'll probably need to put the bag of beans on a chair or something as it empties.

We went out and bought a 19mm wood drill bit. It's the perfect fit. The nozzle sits in the hole firmly. Note: David's wall has "sarking" (horizontal wood planks) on the inside) then standard plaster board over that. We drill through the plaster and keep on going. The nozzle fits snuggly in the scarking part of the hole. The plaster board section of the hole ends up being 20mm (because the plaster board is so powedery).

If you end up with a different nozzle then it might not be 19mm. Your drill bit size should exactly match the outside diameter of your nozzle - no more, no less.

Once that was all done we started filling the wall - it all works very cleanly now - no extra dust escaping.

Now - we were using a borrowed air compressor; a cheap 2hp Black Ridge BAC95 which we discovered is too small. Once the air tank is at full pressure it would drive the beads for about 60 seconds before running out of puff. Then we'd wait for it to refill and go again. The wall segment took about 10 repeats of this.

So - buy or borrow a 3 or 4hp compressor. Otherwise the systems seems to be complete.

With the 2 meter hose and the funnel that plugs into the wall hole the system is workable by 1 person.

Next time we'll find a better compressor and I'll shoot some more video.

Cheers, Paul

22 Jan 2011 - works OK

We got the system up and running today. It works fast, but still has a few issues to be ironed out.

In the video you can see:

  • the black tube running into the blower handle is the compressed air line.
  • the yellow thing in my hand is a PnueVac blower/vac
  • the clear tube is a 32mm PVC tube, through which the polystyrene beads flow
  • the big white bag at the other end of the tube is full of recycled fire-retardant polystyrene beads
  • outside the back door is a cheap air compressor supplying the air
  • the holes in the wall are 16mm diameter


  1. We are currently just holding the blower against the wall. [Fixed, see 3 March 2011 above]
    • This means you have to hold it firmly and not wiggle the blower, or some polystyrene dust will escape into the room. This is a bad thing because polystyrene dust apparently stays in your lungs. I don't know what the chemical/poison implications of that are. So, it's important we wear a good respirator. I did my house from the outside which greatly reduced this problem because the ventilation was very good, and my nozzle plugged into the whole I'd drilled so there was no leakage. But it was a much 32 mm diameter hole, rather than this new 16mm hole.
    • We made a quick seal ring with a piece of closed-cell foam from an old gardening knee-pad. This helped a lot - but also made it harder to line up the blower hole with the wall hole.
    • A better solution is to create a reducer piece so that we can plus the blower nozzle into the whole in the wall. This may mean we should increase the wall whole size to 18mm to allow for the reducer nozzle to retain an inside diameter of 16mm (which my friends at BRANZ say is the smallest hole that will easily allow a good flow of beads).
  2. The intake still needs to be wiggled constantly to produce a steady flow of beads through the tube. [Fixed, see 3 March 2011 above]
    • This means the job currently needs two people.
    • Alternatively if we could work out a hopper system that provided the perfect feed in flow it would reduce the amount of attention the system required.
    • If we can get a nozzle reducer fitted onto the blower then it can be plugged into the wall hole and won't need careful attention.
  3. Our borrowed air compressor might have been a bit whimpy.

5 Jan 2011

Bought a 3m length of 32mm diameter clear PVC tubing from Mitre10. It's about $12 per meter.

And got a compressed air connector nipple ($4.70 from Tool Team in Lower Hutt) that screws into the handle of the PnueVac (see blow).

Now all I need is an air compressor.

22 Dec 2010

We're now going to try something a little closer to what professional insulation blowers use; a compressed air powered blower/transfer gun system. (The Ryobi Leaf Blower is a little cumbersome so we're hoping this will work better.)

PnueVac Vacmaster 22
PnueVac Vacmaster 22

I've just bought this PnueVac Vacmaster 22 from Industrial Tooling Ltd for $50 plus $9 courier. I also looked at the Exair Vac-u-Gun but they wanted to charge US$198 to ship it.

We'll borrow an air compressor after we get back from our holidays, around mid January.

PnueVac Vacmaster 22 instructions

Cheers, Paul

Page last modified on 07 July 2014 at 10:04 AM