Here are the radiant-heat pipes that work their way down the center beam of the house. The larger pipes (at left, which disappear to the other side of the beam) are for the kitchen/family room infloor tubes (one pipe is the hot "supply", the other the cooler "return") ; the 4 smaller pipes are for the mudroom's infloor tubes (2 pipes, supply and return) and for the baseboard radiators in the garage attic (again, 2 pipes).