Most of us have seen some remarkable work done with XPS insulation foam. Whether is being used as the base for a diorama or being cut up into individual 1/35 scale bricks, this material is light but strong. You can carve it, cut it, and shape it into some cool shapes. The wargaming crowd has been using XPS foam for years, but we modelers are more recently discovering its wonders.

My barn in-progress

XPS foam is used for insulating buildings and comes in large sheets. They typically come in 4’x8’ sheets of various thicknesses (1”, 2”, 3”), although stores may sell smaller cut downs too. If you want thicker construction, gluing several pieces together is going to be much less expensive and radically easier for us hobbyists to find than thicker pieces.

This material is great because you can shape in so many ways and with so many tools. You can cut it into smaller pieces with a table saw or hot wire table (mine is from Proxxon and is fantastic). You can shape with a hobby knife, hot wire tool or knife, or even a pair of pliers.

 

The base layer of foam

The pink stuff is easily procured at Home Depot and similar stores. You can even buy it online at sites like: https://insulation.supply. What you’ll notice at those sites, however, is that there is a lot of options for what you can buy. XPS foam is all the same, right? Nope. There’s a ton of “compression strengths” that are more or less “firm”. And each manufacturer has different ways of talking about the different types… as well as coloring them differently.

If you’ve followed what the European diorama builders have been doing, you’ll be familiar with a grey XPS foam called Styrodur. This is simply an extra firm version made by BASF. The pink stuff is made by Owens-Corning. The blue stuff by Dow.

I’ve been on a monumental search to source the Styrodur foam. And I’ve learned some things along the way. Buckle in, it’s about to get nerdy!

The pink foam boards that home improvement stores like Lowes and Home Depot sell is Owens-Corning Foamular 150. It’s the really soft stuff, but relatively inexpensive. (The blue version is basically the same stuff, but made by Dow)

Owens-Corning sells Foamular in other density (compression) levels too. But these are only sold at insulation supply houses (I’m pretty sure every somewhat big town has one) and some places online.

I found a local supply house here in Austin (IDI Distributors) and picked up two density levels:

Foamular 250: it’s still soft, but better than the Home Depot stuff. It was also pretty cheap at $27 USD for a 4’x8’x1″ sheet

Foamular 1000: this stuff was like a rock. Cuts perfectly on the hot wire table, resists when you push on it with your finger and probably wouldn’t dent when you drop it like the 150 or even the 250 does. I also was able to “draw/carve” pretty nice bricks and rocks into it without it generating the “crumbs” and tears like the 150. I also used a brick pattern roller to “roll” a brick pattern into it. Worked great. (The 250 was better with the roller than the 150, but still not great). You can even use a wad of aluminum foil to add some rough brick/stone texture.

If I had to guess, and based on the limited feedback from the foam supply house manager, the Foamular 1000 is likely very close to Styrodur that the Europeans use. These sheets were much more expensive at $134 for a 2’x8’x2″ sheet.

(NOTE: Styrodur also comes in multiple density levels. YouTuber Uncle Nightshift, for instance, told me the Styrodur 2800 is just way too coarse to use)

The supply houses are targeting commercial clients and the one I went to here in Austin told me they rarely order the Foamular product. I just happened to luck into a bit of stock they had to due to their “ordering mistake”. Ha! They said they could reorder it without problem, but… it would need to be a minimum order of 9 (!!) full shipping pallets. Yikes. Same thing, in theory, for getting the Styrodur (a BASF product) but it would take a minimum of 3 months and have AT LEAST those same minimum order quantities.

Using a ball of aluminum foil to texture, a pencil to “draw” the bricks in, and some acrylic paints to add color, this Foamular 1000 was great to create walls!

I also traded emails with https://insulation.supply support and they told me that these two are popular with their scale modeling customers:

  • Kingspan GreenGuard Type VI XPS Insulation Board
  • Kingspan GreenGuard Type VII XPS Insulation Board

I haven’t put hands on either of these or compared the specs.

The main metric that we modelers seem to need to pay attention to when shopping for foam is the compression rating.

OH! And the gray color Styrodur comes in is just a tint issue. Apparently the grey is more environmentally friendly and some US manufacturers are moving away from their current colors to get more environmentally friendly too.

Hope this helps some other Americans who are trying to get a replacement for the tasty Styrodur.

Be sure to follow the Barn Diorama project page for more info on how I actually put this foam to use.

To find out more info, here’s a few links:

Uncle Nightshift: a great modeler and YouTuber who has done some remarkably cool foam building/base builds

https://www.youtube.com/c/NightShiftScaleModels

North American foam modeling: A Facebook group for folks building with foam

https://www.facebook.com/groups/670784366801948

Example of a HUGE diorama built with standard blue foam

https://www.facebook.com/watch/?v=624014708935279