On the second link it shows how to make it. Although the 'front porch' is kinda inclosed so that might make it more than one sheet. But you also have to think the hole they made for the heater and window. They might have used that. I was thinking you could always go to a salvage yard and pick up the window for next to nothing. Im not sure about the heater, but the plywood would cost $13 or so. But then again you have to think is it worth it to YOU. I personally wouldnt pay this much, but Im sure there are 30 people in line behide me that would. It just depends on how you ask.