For those that have used door knockout/cutouts for insul.

how does one go about figuring out where to get them from? I am waaaaaaaaaay too tight in my garage build budget, and I really dont want to have to sacrafice the radiant heat. I have a spreadsheet with all material pricing made up and am desperately seeking ways to cut costs. I am looking at spending 1200+ for 2" XPS. I have read posts where others used the door cut outs and spent 1/3 of what they would have spent to get XPS. I just dont have the slightest clue where to start looking and my internet searches have proven fruitless.

Okay...at the moment I am clueless. What is a door cutout and what is XPS?

The door "cutout" is the piece of an insulated steel entry man door that gets cut out when a window is being installed. It is usually abour 24" x 30" and is scrap. Great for insulation under a concrete floor though because it is a sandwich of insulating foam between steel skins. Tough so you can walk on it and you can screw the PEX directly to it using a plastic clamp - thereby eliminating the need for the wire mesh and a vapour barrier.

The contractor that I had pour my floor sourced them from a local steel door manufacturer. I have also seen them for sale at a hardware store near where I live. Maybe check your local yellow pages for a steel door manufacturer near where you live and then call them to see what they do with the cutouts.

XPS = Expanded Polystyrene

I spent about an hour last night googling for door manufacturers in this state, but I didnt find anything. I guess I can check the yellow pages too

I took every door brand carried by all the local big box stores and found where they are located... only one was remotely close, and they recycle the cutouts internally. I asked if I could purchase some of the cutouts from them and was refused.

The brand name on the doors in the store may not be the companies you want to talk to.

The guy at the Big Box store that actually orders the doors gave me the names of the companies in my area ( Benbuilt and Irwin Builders supply) that get the door blanks from Thermo Tru, etc. and install the windows and make the jambs, then sell the finished door to the Box store.

You want to call everyone that sells doors in your area and see who they order from, then talk to that company. Home Depot may have a different supplier than Lowes. The local Mom and Pop may have a third. Try them all.

Also, I found that they recycle the steel ones here, but the fibreglass ones they have to pay to get rid of, so they were happy to give them to me for free. Although I did get questions like "What would you want those for?"

I had a pretty good system going for a couple of weeks, where they would save them up and I would go on Fridays and pick them up.

Hope this helps John

craigslist in my area (tacoma)has free pallets full. Wish I saw them before my shop build.
(I know old thread, just FYI)