Wall Insulation Questions

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How to convert a hair dryer

August 2010

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Reaction with electrical wiring?

6 September 2009

I am considering getting into this insulation in South Island. Was very informative to read your experiences. Can anyone tell me more about the reaction with electrical wirirng.

Barry T

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.
There are a bunch of other links there which all seem similar.
In sections of wall which include electrical wiring I suggest you fill with Rockwool granulated insulation using the same blower.

Suggestion: how to create a hole for an extractor fan outlet in a wall filled with polystyrene beads

6 March 2009

Try a "circle" of small holes (probably 5 or 6) around the proposed duct position and inject expanding polyurethane foam. Expanding foam should have enough pressure to push the beads back and replace them with solid foam. You can then drill through the foam for the duct.

John P (UK)

Blown cellulose insulation into attic floor adventure

26 February 2009

I just want to thank you for sharing your experience in making the two insulation blowers. I recently purchased 8 bags of fiber glass blown insulation for just some Attic touch up after installing 2 bathroom exhaust fans on the floor beneath. I had thought of renting a professional blowing machine but had not realized how large and heavy they are. Problem is you need a truck to haul this heavy machine. I think your home made blowers will work well for my small task. This week-end I'll start making one using the exhaust port of a vacuum cleaner which I think is more powerful than the dryer method. I'll email you after I'm done. Again thanks.

Jerry G

And then...

3 March 2009

Hello Paul,

I wanted to give you an update. I tried your "Y" connector vacuum cleaner exhaust system that you designed for blowing polystyrene insulation in wall cavities but I was blowing cellulose insulation onto my attic floor. (I did not try the hair dryer method.)

Unfortunately the "Y" system did not work with the heavier dense fiberglass blown fibers I was using. I had only eight bags (2 x 2 x 3.5 feet) and used a new system which I developed out of desperation/frustration while standing in my attic.

I opened each bag one by one and emptied the contents and while the fibers expanded I speared the contents using my hands in a circular and pulling motion. I separated the bale into many smaller portions and then continued with my hands and feet to separate the lumps. It was labor intensive and I do not recommend it for large projects and I do not feel this is an ideal solution. Then I used the exhaust on my vacuum to blow the pieces across the attic. Also the air from the vacuum hose continued to separate the fibers more.

I'm sure I still had some small clumps but it was acceptable for this small project due I did not want to rent and transport a very heavy profession insulation blower especially since the units would not fit in my car and I do not own a truck. Considering my circumstances I am pleased with the results and that I finally finished.

But I'm very glad my wife could not see me doing this.

Best regards
Jerry G

12 Oct 2008

Found your article very helpful but for a different insulation problem. I have a modern penthouse flat with insulation in the flat roof construction not the ceiling 2ft below the roof. There is a lot of heat loss. Several insulation contractors have been to quote and because its small the price is expensive (£4k for one!) I'm going to use your vacuum solution to do it myself. How far do you think the vacuum cleaner will blow beads into the roof space ie., if I put a 10 ft extended noozle on the Y section.

Simon T (UK)

Hi Simon
I never measured the blowing distance.
The main challenge you may find is avoiding them blowing back towards you as you work. The beads are incredibly light - when you release them in a small space with a blower going I suspect they fly all over the place. Make sure you have a very good mask - the polystyrene dust is probably a very bad thing to get stuck in your lungs.
How could you prevent them drifting back out the man-hole as you work?
Cheers, Paul


I'm really impressed with your work and it looks like you just managed to finish before the baby arrived! Do you think your system would work from the inside? ie cut holes in plasterboard, fill with beads then re-fill the plasterboard? Does polystyrene degrade PVC used in electrical wiring? I also have dwangs so I\'ll need 3 times the number of holes too! Anyway thanks again for the inspiration

Tom M (Scotland, UK)
6 September 2008

Hi Tom
Yes - polystyrene does "eat" PVC electrical wiring - so you need to avoid it at all costs! I was also fortunate that most of my wiring is on interior walls. There were only three places were I had to leave the section empty. I've been thinking about blowing in some other sort of filling - maybe wool?
I think going from the inside walls should work. (I suspect my wife may not have tolerated that much hassle.)
Cheers, Paul

Hi Paul,

Did the EPS beads get a static charge from all the handling? How did you keep the beads from creating a "chimney effect" in the wall when the static charge creates a void in the middle of the wall cavity?

Any regrets yet?

Most houses in Southern California built before 1975 (mine) don\'t have insulated walls, and your retrofit solution sounds better than the expanding foam or celulose (shreaded newspapers!) blown in.

Garth L
4 July 2008

Hi Garth
Must confess I hadn't thought about static charge. It's a very good question. [My latest experiments show no signs of this problem.]
The frustrating thing is... I don't know of an easy way to measure the thermal resistance.
One thing I have noticed is condensation on the outside of the walls in the areas where my insulation is (between the studs) - and no condensation where the studs run up the walls.
That suggests to me that the area between the studs is cooler than the stud area. Therefore the studs are conducting heat out of the room better than the polystyrene filled spaces. And that's another way of saying the polystyrene is a better insulator than the solid wood stud.
By comparison - I have a few columns that I have not filled (because they contained electrical wiring - and polystyrene melts wiring insulation). These sections do not show condensation.
So all that tells me is that the polystyrene sections are better heat insulators than the non-filled sections. But how much better? - I just don't know.
In the year after the wall insulation went in my power usage (all my heating is from a electric heat pump) was down a wee bit - right up until we had a baby. Looks like were going from 5000 kWh last year to about 6500 kWh this year.
Cheers, Paul

What about electrical wires - doesn't the polystyrene react with the plastic around the wires?

I'm lucky that our house has almost all it's wiring on the interior walls (ie between rooms) not the perimeter walls. There are about 4 spots with wires - so I just left those empty. At some later stage I'll think about filling those with something non-reactive, like wool or paper fibre.

Is it fire retardant?

Yep. Poly Palace only use fire retardant polystyrene in their underfloor products (so I made sure they gave me fire retardant beads).

In the UK polystyrene wall insulation is blown in with a glue. Why is that?

My guess is:
  1. it means the next time you drill a hole in the wall you don't have a lot of beads dribble out
  2. it stops/reduces the polystyrene from settling
  3. it may improve the polystyrene water resistance
I don't have an answer to any of these issues with what I've done.

I've heard that polystyrene absorbs water over time. Given that your house has wooden walls - will any leaks mean your walls become water logged over time?

I've heard that too. Which is one reason why if you have underfloor polystyrene blocks it's very important to have a vapor barrier too - so that they don't collect the water vapor expiring from damp ground. polystyrene blocks used in floating marina's have to be replaced eventually when they become waterlogged. I'm not sure how long "eventually" is.
In my case I'm currently just hoping that my walls are waterproof.

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