does colour matter? (leo g)

leo g_13

installation we are doing, some of the rads are to inset to the wall. my client asked recently, what colour he should paint these. i thought at the time he was asking more about a colour to "frame" the rads in. but now i am thinking that maybe the colour of the background could "push" the rads to a better output?

is this possible? i know that we have discussed painting free standing rads, has anyone done any kind of testing for the colour behind the rads? M E? H R?

my line of thinking right now, is that if he goes with a dark colour behind the rad, it may "store" some energy for later release during the night set back period.

or if he uses a light colour, this may "reflect" the energy from the back of the panel out into the space, thus providing a better output of the rad, so less energy will be needed to heat the space.


hmmmm.....


leo g

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Uni R

Depends

Are those exterior walls? If so a reflective adhesive might be your best bet. I'd actually do the same even if it were an interior wall. The more energy you store for setback, the less effective setback works for saving energy.

Christian Egli

Jet black

The idea of storing heat in the wall behind the radiator does not make sense if we are talking about an ordinary room.

The radiator will emit heat in all directions into the room, half will shine towards the wall behind the radiator, the other half into the three remaining walls. And all those walls absorb and release heat at the same rate, from the same radiator and into the same room, just at different concentration. So there is no different storage for the room wether the back wall is black or reflective.

If the back wall is an outside wall, I agree that a reflective coating is a must.

But, for instance, if the radiator is surrounded by three glass walls in that room, through which a lot of the heat rays will be lost straight into the atmoshpere, then adding a reflective coating behind the radiator would just make the loss even bigger. In this case painting the back wall black would slow the losses of the room.

For measurable overnight heat storage, I think you would have to place a large water tank behind your radiator which could hold and release heat from the radiator to the room. I would only see the sense of doing this if you had some tropical fish to put in the tank.

My favorite color for radiators is black on the front side and silver on the wall side. The difference in emissivity is huge.

Black should be a designer color. Thanks for making me think.

leo g_97

i love

the idea about the fish tank!

leo g

scrook_2

anything...

non-metallic on the front of the rad, regardless of color, should be fine, and anything metallic ('silver' aluminum being an obvious one) should do what you want to do.

As for storage in the wall I wouldn't worry about it, but for outside walls a reflector (say thin, bright, perhaps even clear Irridite finished, aluminum sheet metal) might be helpful to reflect radient heat back into the heated space.

Mike T., Swampeast MO

In that room with three glass walls...

...the IR heat isn't lost straight to the atmosphere.

I know it's hard to comprehend and impossible to "see" but window glass is almost completely opaque to heat in the form of IR radiation.

Single-pane windows loose a lot of heat because they are cold--on the INSIDE--and the glass is quite emissive. The glass accepts lots of radiant energy which in turn heats the glass which in turn radiates in all directions--both inside and outside. Since the outside of the glass is now warmer than most everything else outside, more radiation is flowing from the outer surface than to it. Since the inside of the glass is probably the coolest thing in the room more radiation is flowing into the inner surface than from it.

Multiple glazing lets the inner-most surface of glass stay warmer than normal--thus it accepts less radiant energy and has less to transmit from its back side to the next pane.

If window glass were transparent to IR, multiple glazing would have NO effect on radiant heat loss because it would just be passing through...

When thinking about windows and radiant heat consider the window to be a wall--albiet a thin, poorly insulated wall.

With this in mind, read the active post regarding insulation and consider why traditional storms on old windows (wide air gap and everything in good shape of course with good infiltration control) are generally regarded as just as efficient as modern multi-pane replacements. Then think of why the one guy was serious when he said that in hindsight he'd use two double units with a big air gap instead of his triple "pain" windows.

leo g_13

mike

i was talking to one of mycontractors (a good german one!) about windows. here is his angle. he feels that a single pane, but about 1/2" thick would be just as effecient in R value as your typical double pane. actually, he feels that over the life of the windows this single pane would be more effecient, as there are no seals to fail.

thanx for the physics on the window heatloss, it makes sense.

i have 4 of these panel rads going on outside walls. right now we are figuring on painting the backside of these spaces with an oil based high gloss white.

leo g

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jerry scharf

glass as insulation

> i was talking to one of mycontractors (a good

> german one!) about windows. here is his angle. he

> feels that a single pane, but about 1/2" thick

> would be just as effecient in R value as your

> typical double pane. actually, he feels that over

> the life of the windows this single pane would be

> more effecient, as there are no seals to fail.

> thanx for the physics on the window heatloss, it

> makes sense.

>

> i have 4 of these panel rads

> going on outside walls. right now we are figuring

> on painting the backside of these spaces with an

> oil based high gloss white.

>

> leo g

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 286&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Mike T., Swampeast MO

Leo

You might want to do some web searching regarding the placement of panel radiators.

A growing number of people (particularly in Europe and Canada) are studying placement and are finding that placement on inside walls in full view of the exposed surfaces results in greater radiation, less convection and less temperature stratification. (This does assume modern construction/renovation with insulation and decent air infiltration control.) No need to insulate behind the panel when its' back is towards conditioned space.



Ask a drive-up bank teller some day how well they think thick glass "insulates".

jerry scharf

glass as insulation

I like to be a bit specific about this. Glass is opaque to long wavelength IR. The IR spectrum is very broad, and covers the entire range of wavelengths from about 1 micron to about 1 milimeter. Glass is quite clear at 1.3 and 1.5 microns, that's what fiber optic cables use. Radiant heat is long wavelength IR. That's why greenhouses work.

As for 1/2 inch glass as an insulator comparable to double pane, no way. Glass is a much better conductor of heat than gas, especially heavy noble gases like argon. Also with double pane, you can put a "low e" coating (a very thin layer of metal) on an inside surface and substantially improve the window's performance.

jerry

Mike T., Swampeast MO

Thanks Jerry

Is longwave IR also referred to as the "far" infrared range?