Hydronic Floor Advice for Shop

[Larry Edgerton]

I pour the slab, insulate, and then tubing and concrete/lightcrete above the structural slab, so that if anything ever goes wrong I will just have to work on the thin [1 1/2"]top layer. Not a lot of added cost, and a lot of peace of mind.

I too have seen plastics that do not last as long as claimed.

Look for a low oxygen permeation level in your tubing. I used Stadler last time as it was the best, but there could be better now. Below the slab is not a place to scrimp.

[Tom Godley]

O2 barrier Pex has been around for many years and has a proven track record. Other types of tubing have been used over the years -- some with disastrous consequences -- A rubber one comes to mind I would not worry about the life of the tubing.

Normally you want to use O2 barrier Pex so that all the free oxygen will be driven out of the water. If you use regular Pex then all components must be corrosion free -- this is often impossible or too expensive.

The Pex/AL/Pex holds its shape and has a better heat transfer rate because of the Aluminum sandwiched inside. Some people like it better but it can be more difficult to work with in a confined space. It is a little more expensive that standard O2 Pex and is not necessary in a slab situation. I just used some on an addition -- Product was Mr. Pex -- I think from Sweden.

My first radiant project was a large sun room with a lot of glass all covered with expensive limestone. With the fear of a leak I ended up using wire mesh and two complete loops in the floor. It used a lot of tubing but it was a learning experience. Because of the tubing coverage I was able to lower the water temp in the tubes. Over time you learn what is important without designing in overkill.

Radiant is very nice in a shop because you are not warming the air at the ceiling level -- by warming the floor you are warming the areas where you are working. Because of this you can often lower the overall temp in the space.

You must do a heat loss for the area so you know what the different spacing will do to the water temps. Also some design are slower to respond then others when you want to raise the temperature

[Rick Cabot]

Hi John
I am not sure of your location, but cold climates demand special consideration. I have attached a photo of our shop (2 stories) floor construction in a very cold Northern Maine climate. After the gravel base was well compressed, I added a layer of poly, followed by 2" of rigid pink insulation. The radiant pex tubing was then connected to the rebar and the floor poured. The system, including the upstair baseboard and domestic hot water, is run by a propane Brady-White water heating system. It works like a charm and our average cost on the coldest days is between $5-6/day to heat a 40'X40' slab. If you need any further input just let me know.
Regards and good luck
Rick Cabot
Northern Maine

[John Legg]

FIW, I am in Northern Indiana. Cold? Oh yes. This week being the exception, we typically, have blustery cold windy winters without a large amount of snow to go along with it. As I type this, it's 5 without a windchill.