My Little Puppy Dust masks

I was playing with my lego bricks when I had a thought about the insulation 



I forgot to mention how you cut the thick stuff (125mm) as a knife is no use at all. 
I use a normal general saw which does it a treat, but you must mark it well either side and then make sure you are sawing to the lines on either side. 
You also need to cut in the beveled angle where it meets the ridge beam. This prevents any gaps for the warm to dash out of although any gaps you cant plug using off cuts you can use a bit of expanding foam if you are careful with it.
Just use a normal angle measure, that any carpenter would use, and then apply it to the edge you want to go to the ridge beam. Use the edge of the board as one line and then make your angled cut line and follow it with the saw, keeping level with the end of the board. ???? Hang on 
Reading through that I can see that I will need to do some photos when I get back home and post them in explaining it better. 

There is not much mess although you need to clean off the cuts with a stiff brush as the dust can be a pain when positioning the slabs. 
The dust can stick in your throat a bit and give a dry cough so I would strongly advise wearing a dust mask when cutting and installing the thick bits, as well as something to keep the worst of it out of your eyes.

The dust mask modeled below from the "my little puppy" range proved adequate.