Best insulating styrofoam? (or other available material) - EEVblog

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CopperCone

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Best insulating styrofoam? (or other available material)

« on: January 06, , 02:01:12 am » Are there different grades of styrofoam? I wanted to make a small insulative box. One option would be to use the stuff from home depot, which typically has a R value associated with it (but im not sure if its thickness only).

What are some good materials and vendors for this task? I want to be able to work it at home using tools I have (either a 10k rpm proxxon drill press, or a dremel drill press (30k rpm?).

I mentioned tools because I wonder if there is a aerogel like material that's cheap and will drill normally. I will have thin wires going through it. IIRC regular aerogel is a bitch to work. I'm thinking something with insulators that is similar to how "macor" is with ceramics.

It will be approximately 1 inch square. I'd like to keep the total size small, which is why I am looking for better materials.

Someone

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Re: Best insulating styrofoam? (or other available material)

« Reply #1 on: January 06, , 02:13:34 am » Polystyrene foam come in a range of densities, the fluffy stuff that used to be common in packing materials is most peoples experience and hard to work with but denser blocks/sheets are easier to work. Drilling is not always the best option and punches can be more appropriate:

Its used in manufacture of composites, therefore the source for small quantities is model airplane shops.

Tomorokoshi

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Re: Best insulating styrofoam? (or other available material)

« Reply #2 on: January 06, , 02:14:51 am » What is the highest temperature?

I've also used the pink polystyrene foam for things. It comes in several fairly precise dimensions along with R ratings. It holds dents, but at least it doesn't break apart and get statically stuck to things as bad as white styrofoam does.

I've also used the layered polyethylene packing material foam for structural projects, cut apart and re-welded together using a heat gun.

CopperCone

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Re: Best insulating styrofoam? (or other available material)

« Reply #3 on: January 06, , 02:19:38 am » Lets say like 50c. Its meant for keeping something cold.

cdev

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Re: Best insulating styrofoam? (or other available material)

« Reply #4 on: January 06, , 02:42:13 am » There are much better insulators than foam. But most are expensive and difficult to work with.

But one that isn't is a "Thermos", a vacuum bottle. "What the large print giveth, the small print taketh away."

ajb

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Re: Best insulating styrofoam? (or other available material)

« Reply #5 on: January 06, , 06:01:23 am » The pink/blue/occasionally green foam is extruded polystyrene (EPS), the white beady stuff is expanded polystyrene (XPS).  I think EPS is slightly better insulator than XPS, but EPS is definitely easier to work with and more rigid.  How big of a thing are you making?  Since EPS is all the same material the R value is proportional to the thickness, as you'd expect with any insulator. 

FWIW, according to this chart, styrofoam has a thermal conductivity of 0.03 W/mK versus 0.02 W/mK for silica aerogel. 

Siwastaja

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Re: Best insulating styrofoam? (or other available material)

« Reply #6 on: January 06, , 07:25:58 am » Polyurethane sheet is considerably (about 30-40%?) better insulator than polystyrene-based styrofoam (EPS) or XPS. It's also completely water vapor tight, unlike most grades of EPS or XPS. I'd say it's about 0.024 for PU vs. 0.032 W/mK for EPS/XPS, but do check the actual product datasheets.

Polyurethane is used in all modern freezers for this reason. Widely used in house insulation as well. Often available with aluminium sheet glued on. And it's tougher and generates less crap when cut/drilled than styrofoam.

Even the price difference isn't meaningful when adjusted for better insulation and other savings from being able to use thinner structures (think about 50mm wall instead of 75mm for the same result).

So, if a standard styrofoam box is not good enough and you need to DIY and design your own and you have found very good insulation as a requirement in your application, I would definitely go for PU instead of EPS/XPS.

Some aerogels can be even better, but most actual aerogels available in the real market are only about 10-30% better than PU, with 10x the price and iffy availability.

While 0.010 W/mK aerogels do exist, the typical 0.020 W/mK aerogel is a joke, unless you need it for some other specific reason than the insulation performance - for example, temperature tolerance. I know people buy these products simply with their mental image of them being "extremely good thermal insulators", without actually checking the numbers.
« Last Edit: January 06, , 07:42:38 am by Siwastaja »

CopperCone

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Re: Best insulating styrofoam? (or other available material)

« Reply #7 on: January 06, , 03:21:45 pm » Interesting.

That means I can stick to PU. I don't think it will get more then 50c above ambient.

splin

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Re: Best insulating styrofoam? (or other available material)

« Reply #8 on: January 08, , 03:38:02 am » Polyurethane (PUR) and polyisocyanurate (PIR) foams are readily available and have thermal conductivities down to .022W/m/K (but watch out - the performance may not be as good for thinner insulation, perhaps less than 50mm). Most expanded/extruded polystyrene is much worse at .033 to .04

However, Phenolic foam is even better than PIR and the best insulation that I know of at a reasonable price. Its performance can be nearly 25% better - Kingspan K107, K108 etc. Is specced at .018W/m/K (for all thicknesses) which is almost as good as aerogel but much cheaper. See:

https://www.kingspan.com/gb/en-gb/products/insulation/insulation-boards/kooltherm/kooltherm-k107-pitched-roof-board

It's very easy to work with, rigid with good compressive strength but not as tough as PIR or polystyrene - it's relatively brittle and can crumble easily so may require some mechanical protection. It is not as moisture resistant as polystyrene or PIR so not good for sustained contact with water. I'm not sure of the maximum temperature but 50C will be no problem and it is probably better than polystyrene foam.

Undoubtably there will be US suppliers of phenolic insulation but in the UK there is only one manufacturer that I am aware of whereas PIR is made by many companies and is more readily available. Also be aware that only the most recent Kingspan product range (within the last 12 months?) are specced at .018 - earlier product such as K7 were specced at .02 so don't assume all phenolic insulation will perform equally.

texaspyro

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Re: Best insulating styrofoam? (or other available material)

« Reply #9 on: January 08, , 09:02:53 pm » Check out aerogel foam sheets on Ebay...

mark03

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Re: Best insulating styrofoam? (or other available material)

« Reply #10 on: January 09, , 01:00:38 am »

Check out aerogel foam sheets on Ebay...

No results in current or completed listings.  It looks like phenolic insulation is also not available in the US.  I couldn't find polyurethane insulation sheet either although I didn't look very hard for that one.  Just following along out of casual interest.

texaspyro

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Re: Best insulating styrofoam? (or other available material)

« Reply #11 on: January 09, , 01:04:27 am »

Check out aerogel foam sheets on Ebay...

No results in current or completed listings.  It looks like phenolic insulation is also not available in the US.  I couldn't find polyurethane insulation sheet either although I didn't look very hard for that one.  Just following along out of casual interest.

Try searching for aerogel insulation.

mark03

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Re: Best insulating styrofoam? (or other available material)

« Reply #12 on: January 09, , 02:47:27 am »

Try searching for aerogel insulation.

Interesting.  "Spaceloft" is pricy stuff indeed, although if I calculate correctly the seller is claiming . W/m/K ?  (translated from the claimed "R value of 30.9 for three inches")

texaspyro

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Re: Best insulating styrofoam? (or other available material)

« Reply #13 on: January 09, , 02:52:51 am »

Interesting.  "Spaceloft" is pricy stuff indeed, although if I calculate correctly the seller is claiming . W/m/K ?  (translated from the claimed "R value of 30.9 for three inches")

Well, a guy has a listing for 500,000 sq feet for 1.5 megabucks.

Teledog

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Re: Best insulating styrofoam? (or other available material)

« Reply #14 on: January 09, , 05:41:39 am » Depending on the temp & RH, maybe thermal blanket{ie:Kaowool or other} or ceramic fiber board .. coated with rigidizer?
Works well for small kilns (F +) - like mini space shuttle insulation
Check your local pottery supply for the stuff

splin

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Re: Best insulating styrofoam? (or other available material)

« Reply #15 on: January 09, , 10:07:12 am »

Try searching for aerogel insulation.

Interesting.  "Spaceloft" is pricy stuff indeed, although if I calculate correctly the seller is claiming . W/m/K ?  (translated from the claimed "R value of 30.9 for three inches")

It is very expensive. The thermal conductivity is specified to be between .014 and .017W/mK for the products I looked at. Eg.:

http://www.thermablok.co.uk/products/thermabloksp-aerogel-blanket

The aerogel I've seen on ebay is spaceloft:

http://www.aerogel.com/products-and-solutions/all-insulation-products

Note that in that table spaceloft is shown as .017W/mK but the datasheet quotes . which makes you wonder how reliable the figures are. Also note that some of the datasheets for other products, such as spaceloft subsea, have a graph showing how the conductivity varies with temperature - it increases at higher temperatures.

[EDIT] Fixed spaceloft link « Last Edit: January 09, , 06:15:30 pm by splin »

Siwastaja

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Re: Best insulating styrofoam? (or other available material)

« Reply #16 on: January 09, , 03:38:33 pm » PU sheet is common like milk, any hardware store has it in stock in dozens of sizes and varieties - at least in the colder parts of the world.

Trade names can be problematic; for some reason, many manufacturers of anything don't want to tell you what they are selling, to make googling and buying more difficult.

westfw

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Re: Best insulating styrofoam? (or other available material)

« Reply #17 on: January 10, , 03:29:21 am » Quote

PU sheet is common like milk, any hardware store has it in stock in dozens of sizes and varieties

huh.  In the US, PS seems to be much more common; I had a vague impression that PU was disallowed due to its nasty decomposition products in a fire, but that doesn't actually seem to be the case.  And you can get "spray foam" pretty commonly.

I don't know how you'd be able to tell comparative performance between "floral foam", "seat cushion foam", "meat tray foam", "spray foam", "foam insulation panel", and whatever else you can find.  My gut feel is that construction details are likely to wipe out your "30% better thermal properties" in many situations...