Sizing Floor Heat Piping

Brad White_105

with regard to radiant system design, is the Rad Pad (available from this site and via the RPA). Of course, Dan's books, Siggy's book and lots of other things... but the Rad Pad is one of my favorite tools. (I play with it on the train and it almost guarantees me my own seat... :) ) I own two.

Now, to your question:

If you are using an above floor system (say Climate Panel for one example) the piping diameter will be fixed for you. Cannot be thicker than the board of course.

Other considerations are spacing, depth of cover, tubing output, water temperature, floor covering R-value, tubing circuit lengths ...ALL of these things in concert...

Firstly, and forgive me if too basic but your calculated heat loss is an absolute must-do before you start.

From there your BTUH per usable radiant floor square footage can be derived.

From that, your spacing and then your available water temperature can be derived, one may dictate the other.

As an example (not checked, just for conversation), a given room may have a heat loss and floor density of 28 BTU's per hour per SF.

You could have any combination of tubing at a dense spacing but with a lower water temperature, tubing at a wider spacing with a higher water temperature... but with identical outputs.

If your floor topping is thin you may tend toward greater density to avoid "striping" (perceptable warm-cold zones on a given floor). This will dictate a different water temperature than a less dense layout.

If your circuits are unavoidably long you may want to use a larger tube size and the smaller size tubes are more limited. Most practitioners use a 300 foot mazimum for most tubing sizes but for 3/8" (10 mm), 150 to 200 feet maximum...

So you can see how all work together as a system.

Do yourself a favor- buy a Rad Pad and play with it. It gives abundant "what-if" scenarios that will answer nearly any question you may have.

Not like the "Magic 8-Ball" or Ouija Board of course, but those too will get you your own seat on a train.

Brad

p.s. I do not work for anyone who remotely sells or promotes the Rad Pad nor do I have any financial stake in any product or system I may recommend. Full disclosure here.

borysewicz@gmail.com

Sizing Radiant Piping

Anyone have any advice regarding tubing diameter for floor heat? It seems that a most people use 1/2" but some have suggested that 3/4" or 7/8" is better. Supposedly, with the bigger tubing you can get away with further spacing (12"-16" as opposed to 8").

Does tubing size have any ramifications on system performance or comfort? I would appreciate any insight.