I completed the foam in the ditch project. The ditch was dug with excavator, and backfilled by hand. Wife and 2 daughters helped with that... Amazing huh ? If I were to do it again, I wouldn't. I would spend the big bucks and install the pricey insulated pex. Many new creative words were heard coming from both ends of my 85' ditch. My wife closed the windows. Did I take pictures of the process, NOT. I had my hands full. If you think you want to try DIY foam in ditch, PM me .... I will convince you to leave it to the pros.
