Radiant Ceiling – Heat from Above

Pipes that normally run through radiant floors can also run through the ceiling, making many renovation and energy saving projects in existing residential buildings easier.

This is a fairly recent technology whose applications have most often concerned industrial warehouses, or rooms with significant heights, but it could also be applied in the residential sector, especially on existing buildings where the thickness of the floors and the laboriousness of the process do not always allow the installation of a radiant floor system.

The benefits promised by radiant ceilings are similar to those of radiant floors.

The first is the low operating temperature and it is above all from this that a significant energy saving can derive. They are both systems that work around 30°C, compared to the approximately 60°C of normal radiators. 
Let's say we need to bring water from 0 to 30°C, we know that the heat needed is not half of what would be needed to get up to 60°C, but much less.
From an energy saving perspective, replacing an old boiler with a more efficient one is certainly a good idea, but making it work less than half, that is, needing less performance, perhaps a smaller and less expensive boiler, is definitely an excellent idea.

We also know that in a room the hot air tends to rise, this could lead to the belief that a radiant ceiling system heats the room below little and in the end ends up heating the tenant on the floor above more. 
Obviously it can't be like that. 
In fact, a difference that should not be underestimated between radiant floor and ceiling systems is that in the first case the pipes are embedded in the floor slab, while in the second they can be suspended. 
The most interesting typologies that we are going to consider, the pipes are not in contact with the ceiling and are also separated from it by a panel of insulating material placed between the pipes and the intrados of the attic.
Contact occurs between the tubes of the suspended coil and the elements that support it, for example metal slats hanging from the ceiling, or from a support structure. The slats heat any exposed finishing panels that in fact radiate.

A radiant ceiling works mainly through radiation, more than a floor does.

Even radiant floors work by radiation (about 50%), but although it is small, it still has a conduction component (the tubes heat the screed and tiles) and a rather important convection component (the air in contact with the tiles heats up and tends to rise).
The heat transmitted by infrared radiation passes through the air and warms bodies (humans, furniture, etc.), but not the air, so whether the system is placed one or three meters above our heads makes little difference. Furthermore, to obtain the same feeling of well-being for humans, the indoor air temperature (the one detected by room thermometers) can remain lower, usually by a couple of degrees, compared to traditional heating systems with radiators, and even more so in the case of fan coil heaters. By slightly reducing the temperature difference between inside and outside, the formation of condensation and mold is also less likely.

It should be added that with radiation from above the air "circulates" less than with radiation from below, so there is less dust around and even the annoying swelling of the feet of less sedentary people should no longer be felt. 
These two factors mean that the system is particularly appreciated in some production areas linked for example to food processing, or laboratory analysis, in short in all those cases in which workers often stand and operate in environments in which hygiene and cleanliness are elements that cannot be ignored.

We talked about pipes covered by metal profiles. So the radiant ceiling is a bit like the baseboard heating, fixed to the ceiling instead of the base of the walls.

Not really. The slats are missing and that's no small thing.
Skirting board systems require that the “cold” air at floor level passes through the skirting board through a dense series of slats crossed and heated by pipes that carry hot water. There is certainly a good radiant component in the system, but the convective one is not at all secondary. The heated air then runs vertically along the wall, heating it.
In ceiling systems there are no slats, the hot water pipe is in direct contact with the metal dagger. Certainly a “slice” of air will heat up, but it will be of limited thickness, it will stay “still” in the upper part of the room and will not heat the upper floor too much, thanks to the insulating panels.

What does radiant ceilings lack compared to floor or baseboard systems?

The furniture is missing.
In all homes, a good part of the furniture is placed against the walls, certainly rests on the floor, while some wardrobes and shelves sometimes touch the ceiling. Since what you can't see cannot radiate, a radiant surface with a wardrobe on top (or on top of it) will at most heat the wardrobe, which is not a solid, it is full of clothes and air, so it is an excellent insulator of 60 cm thickness. The same goes for kitchen furniture, bookcases, beds, sofas... they are all excellent "thick" insulators that limit the usable surface of radiant floor, wall and even skirting board systems.
The ceiling is usually much clearer, it can be used throughout its surface, leaving ample freedom to move furniture, change furnishings, hang pictures, etc.

The radiant ceiling works well even in summer, alone or combined with the air conditioner.

If hot air rises in a closed environment, cold air will take the free space lower down, this happens naturally. 
So if you cool the air near the ceiling, the warm air below will take its place and the cold air will descend, certainly not with the vehemence typical of air conditioners (responsible for summer neck pain in the office), but more gently, almost imperceptibly.
In this case, dust is probably not avoided (even less with air conditioning), but stiff necks and colds, perhaps.

There is nothing to prevent the ceiling system from being combined with an air conditioning system, as is normally done with cooled radiant floors, but, given the above, this may also be superfluous.

In both seasons, the radiant ceiling also proves to be more “reactive” to temperature changes compared to the floor one which, as we have said, has a normally smaller usable surface and a certain thermal inertia. Before starting to radiate, it must heat the tiles, while the metal profiles take less time.

Custom-made and modular radiant ceilings.

There are both modular and custom-made radiant ceiling solutions on the market. The former have the advantage of being easy to install, but they can hardly exploit the entire available surface, especially in the case of rooms with an irregular layout, and may present critical issues where there are chandeliers or other hanging elements. Custom-made solutions require a slightly more laborious design and installation, but should offer better performance, more variations in the warping and assembly of the structure, and more refined aesthetic solutions.

Under the structure that supports the piping, the exposed covering can be made of simple plasterboard sheets, or better yet, fibre plaster for better conductivity, but also with sound-absorbing panels, especially in the case of offices and conference rooms, or other panels with particular hygrometric characteristics. It is a system that is characterised by its ductility, also suitable for historic buildings with floors, or valuable walls that you do not want to damage with plant equipment.

The design of the installation of these systems starts from a thermotechnical assessment to define the energy needed for heating and cooling. Based on this, the system is chosen and sized with the correct number and distance between the pipes, so as to be able to provide the required power. After the dry assembly of the load-bearing profiles, the heat-conductive ones and the pipe coil, the system is connected to the hydraulic system, filled and tested.

The finished packages can have very low thicknesses, starting from 3 – 5 centimetres, which makes it possible to install them practically anywhere, in apartments with a height just above the standard limits, as well as in attics and lofts.

It is a convenient solution for apartments with independent heating, where the boiler can be replaced by a heat pump for the single housing unit, while in the case of condominiums with central heating it is necessary to reduce the flow temperature of the hot water, because the operating temperature of these systems is lower than that of common radiators.