White subfloor affect suspended tube output?

kevin_5

This is a suspended tube over a basement. Straw bale walls above ground, and insulated concrete forms for basement walls. They will have low R value floor covering such as slate. The thing is they had a mold problem and sprayed the bottom of the subfloor with bleach and then sprayed "Kilz" white primer over it. We will be insulating underneath the tube with the reflective bubble stuff, but the question is: Since white reflects, will it affect the heat transfer from the tube to the subfloor and consequently the output of the floor? Before I staple the tube up, I wanted to find out your opinions. If it's a problem, would it help to paint it black? I gave them the option of extruded plates, but they haven't bit on 'em. So whaddya think guys? Thanks in advance. Kevin

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=270&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Unknown

Primary heat transfer in suspended tube is via convection, not radiation (the part that would be reflected). That shouldn't be affected.

However, without doing full thermal modelling I would guess you may see a small drop in output on the radiant transfer itself. If the project is close to "borderline" for suspended tube, I would play it safe, and put in plates. But then I play it safe most of the time anyway

_______________________________

Northeast Radiant Technology, LLC

Robert Brown, Co-Owner, RPA certified Radiant Designer

207.899.2328
NRT@maine.rr.com

Nron_9

color no important

unless you are planning on floor warming only you should always use plates in a staple up you will be surprised at the money saved with greater energy transfer see pm mag with John Seg latest artical at www.pmmag.com

kevin_5

I agree with you but...

I showed the lady the temp differences required to get the same BTUs out of the floor with and without extruded plates and told her that it translates into better efficiency. Anyway she's not buying it and it's nowhere close to marginal or I wouldn't attempt it without plates. As far as the previous post goes, maybe I'm confusing terms. "staple up" is stapled tight to the floor. "suspended tube" is hanging below not contacting floor. Staple up would be conductive and suspended tube radiant am I correct?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Floyd_5

I really .....

wouldn't give a rat's behind for the difference.....
That mm of contact ain't gonna make a 'nuff difference to ever measure.....with real numbers at least.. maybe somebody trin' to pull the wool over yer eyes can try.....

If it were me... I'd say play my way or I'm outta here.....
it's yer butt if it don't work!!!!! You really want to be puttin' up plates fer free when it don't work and she denies that you "told her so"????

Mike Kraft_2

Suspended tube =

convection.Each joist bay is isolated with insulation.Including the rim joists.The tube heats the air in each joist bay and the joist bays become plenums.The heat transfer convects to the cold floor which in turn becomes your radiant panel.Lotta things going on to make heat.Slow response.But it works if design is on.Extruded aluminum beats it hands down for response,cooler temps and much more even surface temperatures.

cheese

jerry scharf

white at what wavelength

I said this in another thread asking about painting things black. You don't care what you see, you need to know the reflectivity in the 50-100 micron wavelength. Not many people besides NASA care at this wavelength, so I doubt you'll be able to get information about Kilz.

Like the others said, I doubt it will make a measurable difference.

jerry

Tim Doran_2

ASHRAE document

The following is taken form an ASHRAE document that discusses the output of radiant systems. One of the key factors discussed was emmittance and as they have stated it is considered to be uniform and not color dependant. Emmittance is equal in both directions meaning that it effects both output and input(absorbtion) of a surface equally.

1. The various materials tested (vinyl, carpet, plastic, paint) had uniformly high surface emittances of 0.9 and greater. The significance of this is that these surfaces are all equivalent radiators.
2. These same materials can be considered to be diffuse emitters. The surfaces will radiate almost equally well in all directions from the surface normal.

Tim D.

kevin_5

Thanks guys, you're the greatest

I have to honestly say I'm sold on all the benefits of extruded plates but I haven't installed any of them... yet.
To me the issue is like 4 wheel drive. Some people can't live without it and some people can. Where do you live and where are you going?
The only thing that I'm not buying is more even surface temps with plates. Why would they be more even than with the entire joist bay acting as the plenum? It would seem if any design had the edge for even surface temps it would be the suspended tube. What am I missing? Thanks again, Kevin

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"