Insulation for radiant systems

KCA_2

At some point there was a debate over whether insulation was necessary in joist spaces under a radiant system, whether in gypcreet or a staple up....  Some said that it was required and others said no.....  I continually run into installers leaving the insulation out and I tell someone about it but no luck...  The general contractor won't put it in because the installer of the radiant system says that it's not necessary...

Later the basement is overheated and the first floor requires a sweater below 30degF outside... 



What is the skinny?



  :-) Kca

Mark Eatherton

You are operating under the control of the ICC, correct?

Actually, the whole state of Colorado operates under the ICC.



In the International Energy Conservation Code (IECC) of the ICC, insulation is REQUIRED below ALL radiant floors.



Any company that tells you that it is not necessary is setting themselves up for one heck of a lawsuit.



It's the basics of energy transfer. Heat flows from warmer to cooler, downward, horizontally , omni-directionally through the path of least resistance, In certain cases, someone may try and convince you that the upward loss is the same as the downward loss, or that both rooms have identical gain/losses and that a radiant floor, which can act as a radiant ceiling to the space below will work… It won't. It might work, but it won't be controllable.



Reflective foil will not work after the first year. Dust settles on the face and quashes its spectral reflective qualities. AIr gap can be critical, but foil is getting hard to find.



ME

icesailor

Insulation not needed:

You seem to be the smarter one in the room.

The few radiant staple up floors I did never worked for squat or close to my expectations because no matter how many times I explained to the Contractor or the insulator, the reason and need for the air space between the coils/floor bottom and the insulation, it seemed to be like telling the unruly to stay out of the cookie jar. They jammed the insulation up as hard as they could against the coils and lost the ability of the coil to spread the heat to the whole entire floor space. Even when using transfer plates, you still need insulation to reflect heat energy in the way you want it to go. UP!!!. Additional insulation means additional cost to a GC. Like taking the cookies away from the unruly child.

On a hot, sunny Summer windless day, would you sit in the direct sun and have the sun toast you? Or sit in the shade of an umbrella or something? Insulation is like the umbrella or something.

Did this "Contractor/Expert" come from the warm climes like the South where heat is an inconvenience that "those damn Yankees who think they know it all" have to deal with? For some, they live in a parallel reversed universe where they think that cold flows to heat and dryness flows to dampness. In Florida, where I have aluminum irreplaceable windows set in stucco that are no longer made, I can not convince my wife to keep the vertical blinds closed when it is really hot out. The roof overhangs all shade the windows, but the aluminum frames are all the same temperature as the outside. IE, If it is 100 degrees outside, and 78 inside, the frame is 100 degrees and is sucking the cold out of the room. However, a Florida Contractor, certified by the state as an energy expert, told me that cold DOES flow to the heat, and that was why I didn't need to add more insulation to my attic. In a way, your problem with the GC and the insulation in my attic are similar. The hot sun beats down on the roof. It gets to over 130 degrees in the attic in spite of the attic/roof ventilation. The ceiling below gets hot from the heat radiating through the insulation and the inside ceiling gets to a few degrees over the room temperature, whatever the AC is set at. An exposed can light would show the attic temperature of 130 degrees with a IR thermometer gun. Adding R-30 insulation to the attic dropped the ceiling temperature to whatever the inside temperature and the can lights are the slightly higher than the ceiling temperature when you shoot inside.



It shouldn't take a lot of common sense to understand that if you don't insulate under a floor radiant panel, the floor radiant panel quickly becomes a radiant ceiling panel.  The most important thing I ever figured out is that no matter how careful you are to be sure that your (my) installation is perfect and well designed, there will always be someone coming behind to screw it up, never take responsibility for them screwing it up, and behind your back, telling everyone that will listen, how bad you FU'd and what a FU you are.

IR heat guns are cheap now, It is one of the handiest tools you can own. They have "issues" but the more you use them, the more you understand what they are and how to get around them. Shoot the floor, shoot the ceiling under the floor. It will be hotter than the floor. If they can't understand why the ceiling below the floor is hotter than the floor you are trying to heat, they must be from The South, or un-teachable.

IMO.