Mod Con boiler sizing on new install in a brick building

Rich_49

Chris said:

Heat loss is wrong.. If you did a convention loss and came up with 123,000, radiantly its more like 80,000... and in radiant we aren't heating air, we are controlling the heat loss of all objects in the room so you can take the hot air rises, cold air falls to the garbage can.

We are in all actuality maintaining a mean radiant temperature in a space . If all the surfaces are sharing an MRT then the room will feel warm , including the keyboard Jamie . You can certainly bang away on the keys . However , the air is not heated as much as only by the heat transfer between the heated objects and the air . Radiant panels transfer heat energy through radiation and that energy is not released until contacting a surface / object

Zman

The panel radiators also have a convective component that will help warm the exterior wall surfaces, this will help offset the colder MRT of those surfaces.

kcopp

Its been a while since we have heard back from the OP.....

Jamie Hall

kcopp said:

Its been a while since we have heard back from the OP.....

I think we scared him...

In reality, the only heating type we usually encounter which does not have a significant radiant component is forced air, when one really examines it. And, of course, anything which has a optical (well, infrared, but that's a detail) line of sight with the radiant emitter -- whether it's the floor, a panel radiator, a big old steam radiator, doesn't matter -- will be warmed, more or less, by that radiant emission.

The problem comes in when there is only a radiant emitter -- the most extreme example, of course, being the overhead infrared emitters often used in warehouses or barns. In those situations, anything which is shadowed will not be heated.

I wonder a little if we aren't getting tangled in terminology here. A radiant floor, for example, cannot heat the upper surface of a table or couch (or piano keyboard!) by direct radiation -- and yet one can be quite comfortable in a space with only a radiant floor -- but only if the radiant floor has managed to bring the objects in the space up to a comfortable temperature. I would propose that the only way that happens is if the radiant floor (or whatever) heats the parts of the objects which "see" it, which in turn heat the surrounding air, which by convection will, eventually, heat the rest of the space. Provided there isn't too much air circulation.

I have experienced several structures with radiant ceilings -- with ample capacity. The floors and spaces under the beds in one which I particularly recall were pretty cool (well, cold...) and the air temperature, while suitable for sleeping, was too cold for any sort of comfort, although surfaces of furniture and so on were nice and warm...

As a counter example, however, in areas where the overhead emitters are used and there is air circulation, the air temperatures tend to follow the great outdoors pretty faithfully.

Would it be more precise, perhaps, to refer to large surface area low temperature emitter rather than radiant emitter? A good bit clumsier -- but perhaps more accurate?

Gordy

MRT would be the proper term. Any emitter can achieve an MRT. How efficiently the selected one does is another matter.

The goal is to bring all mass in the space to a comfortable mrt. Once equilibrium is reached MRT follows. The more mass containing components in the space the slower mrt is reached, and the slower it falls. This is of course from a cold start condition from below set point. Once set point is achieved mrt just needs a bump to maintain set point.

Shadowing which is what Jamie refers to under furniture in radiant ceilings, or on top of furniture with radiant floors.

This is why I like radiant ceilings. We sit on couches, chairs, and lay on beds. Save the floors for barefoot areas such as baths, tiled floors etc. I used both in a lot of rooms radiant sandwich