For DIY you are looking for something simple easy to do and inexpensive. Otherwise you hire the contractor, go to work and work 2-3 years to pay what he has done in 2-3 days
. On other pictures I can see plywood cut round tubes are sitting in the slot. The advantages of "my" design are:
1 use 1x2 lumber (cheapest)
2 time saving (you cut 1x2 approximately, I can only imagine how much time it will take to cut all rounds and how much waist is left
)
3 tubes do not contact subfloor(the bottom) they are suspended in omega shape heat transfer plates, because 1x2 is 3/4 inch high but 1/2tube OD is 5/8 of an inch.
Tubes and transfer plates contact the top layer of black painted plywood. Wood strips do contact the subfloor, but you have no choice. Ideally you want all heat to go up, heat that goes down is waist because it will heat up the structure, the sealing of the lower floor(if you have one) etc. As everybody knows the heat transfer rate depends on area. In my case the contact area part is only fraction of the whole area of the floor because it is only sum of areas of all 1x2.
4 the heat from tubes and plates (which are the hottest part) is reflected by foil toward upper layer of floor making system more efficient.
5 Tubes expend and contract. In my case they are free at the end and can do it.