To understand how radiant ceiling heating and cooling work, first we need to get the #1 myth out of the way before we discuss radiant ceiling in greater detail.
MYTH: “Heat goes up”
FACT: “Heat does goes down”. Just stay in the sun and feel it.
This principle should read like this: “hot air goes up and cold air goes down” unfortunately the bad habit of generalizing has made it known in the wrong way.
A radiant panel not only uses the air as a method of heat transfer but, as the name implies, uses mainly thermal radiation.
It is based on electromagnetic waves, the same physical principle that allows many other technologies to work, for example lightings, televisions, mobile phones. Don’t worry, even if X-rays are also electromagnetic waves, here we’re talking about waves characterized by different frequencies: the most physiological and natural electromagnetic waves, the ones radiated by the human body. To be more precise we are talking about infrared rays at low frequency that are emitted from surfaces at temperatures typical of biological organisms.
In common with all the other electromagnetic waves, they all travel at the speed of light.
A radiant ceiling heated only a few degrees more than the other surrounding surfaces, immediately emits infrared heat (thermal radiation) in all directions. These radiations directly warm any object or surface in the surrounding area, no matter if they are up or down.
In heating the thermal emission of the radiant ceiling it is almost exclusively of the radiation type since the air that is in contact with the ceiling, even though heated for a few inches, is trapped without a way of rising.
In cooling the radiant ceiling panels are cooled down, and rather than emit infrared radiation, they absorb the thermal output of surrounding objects, bodies and surfaces that become “radiators”. Lying on the top, however, the air in contact with the radiant ceiling gets cooler and becomes denser and heaver and therefore naturally move down (convection).
Typically radiant ceilings in cooling absorb heat for 60-70% by radiation and the remaining (30-40%) by natural convection. The combination of these two effects significantly increase the performance of a radiant ceiling compare to radiant floor.
And our body? With its surface temperature of about 86-96F is almost always warmer than the surrounding surfaces. In the winter it will emit less, holding for itself the metabolic heat and giving a feeling of warmth. In summer it will emit more giving that feeling of freshness (in this mechanism plays an obviously important role the clothing).
You might also find this blog interesting:
Radiant Heating from above, radiant ceiling vs radiant floor
Do you need insulation in the roof if you have radiant heating in the ceiling? And you have a flat roof with no attic.
Ray Magic radiant panels come with 1 1/2″ EPS back insulation with 9.8 R value. It is not necessary to add insulation since the radiation will be directed down to the room.
The insulation is part of the panel and will add R value of about 10 to the ceiling structure.
It refers to a number of conditions in which the majority of people feel comfortable.
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Is there any concern for the safety of a human exposed long term to EMFs from ceiling radiant electric heat (electric wires as opposed to heated coils)?? For example, an individual with a pacemaker, or an individual who has aneurysm clips in their head, or an individual who has an autoimmune disorder?
Dear Bonne, thank you for contacting us.
Our system is hydronic and does not generate any electromagnetic fields.
Could a ceiling fan be installed AFTER panels have been installed and sheetrocked?
Typically we avoid areas where ceiling fixtures will go in the design process since our panels only require about 70% ceiling coverage. But if you have access to the attic and want to install a ceiling fan after the fact, you could use a thermal camera to see the serpentine piping within our panels, then you could cut a hole that is 3 inches in diameter between the piping to install ceiling fixtures!
Two questions; Does ceiling height affect the performance of heating and cooling? And is shadowing effect performance to warm or cool under objects?
Increasing the ceiling height doesn’t change the performance of the panels, but it does increase the room’s load requirements, so you might need slightly more panels to meet the loads. When you turn the system on, there will be a shadowing effect where the objects directly “in view” of the panels will heat up or cool down faster, but the entire room will approach the set-point, so the difference will be negligible in areas not in the direct line of sight of the panels (like your feet under a desk).
Can you add radiant cooling to an existing radiant heating system? Also, can you put floor boards on top of a radiant system? (We have radiant heating in the ceiling , with no access to our attic).
If you have an existing hydronic radiant ceiling (not electric), you could use our mSense room comfort sensors and our mControls to provide radiant cooling. You’d need our mSense room comfort sensors to monitor the dew point in each room, and you’d need mControls to modulate the temperature of the panels to stay above the dew-point temperature. If the radiant surface temperature drops below the dew point temperature, condensation would form, so that’s why you need strong sensors and controls to provide cooling. Heating doesn’t have the same risk of producing condensation since the water temperature will always be higher than the dew point. You’d also need to add mixing valves to the mechanical room, and you’d need a source for cooling, like an air-to-water heat pump (which would also be able to generate hot water for heating). If the radiant system is electric, you won’t be able to provide cooling.
Is this used a lot in basements?
Most of our projects provide heating and cooling to the entire building/home, not just the basements!
Is it fair to say that a radiant ceiling is less efficient for heating than a radiant floor? Even though the ceiling will radiate heat in all directions, the air closest to the ceiling will be the least dense due to being the hottest in the room and thus will move upwards.
I suppose if the needs are for both heating and cooling, that the ceiling could make sense though.
Thanks for your comment! In terms of efficiency, you would be correct if we tested this in a lab-like environment with no windows, furniture, or comfort (meaning, the goal is not comfort, but efficiency). This is due to the additional convection exchange you mentioned, where roughly 70% of the thermal energy transfer is radiant, and the remaining 30% is convection.
But in real-world environments, a radiant ceiling still beats out a radiant floor in terms of heating efficiency. We can break this down into 5 reasons:
1. The Field of View (FOV): When radiating thermal energy, the thermal energy performs similarly to how light does, meaning it can be blocked. Since radiant floors have furniture over them, the underside of the furniture will obstruct the radiant surface. For the most part, a radiant ceiling has a direct line of sight to the occupants, so it’s easier for the thermal energy transfer to take place.
2. Next, the FOV also impacts how the radiant surface reacts with windows which often increases loads. As windows introduce a cold surface, a radiant ceiling often has a better line of sight to the windows. Because of this, a radiant ceiling can exchange heat with the cold windows in a more efficient way. A floor, however, still must battle obstructions and often has a worse line of sight to the windows.
3. Thermal mass also comes into play as radiant floors have a much greater mass relative to a radiant ceiling. Because of this, more energy must be used to bring a radiant floor up to temp. The thermal mass difference also adversely affects the radiant floor’s time to delivery.
4. Next, radiant floors are limited in their max temp due to comfort levels. Typically, you don’t want the radiant floor to go above 80°F because it would create an uncomfortable living environment. With a radiant ceiling, however, you don’t have the same issue, so we can run water that is 90-130°F to deliver more heating much faster. An added bonus is that our system is not fixed temp; our controls can start with a high water temperature and dial it back automatically as we approach the set point.
5. And that brings us to the last point, speed! Since our panels have a much lower thermal mass, they can be heated up much faster, so you wouldn’t need to run the system as long to reach the set-point.
Let us know if you have any further questions!
Is radiant heat electric or gas?
Great question! It can be both! It all depends on the energy source used. Our panels provide radiant heating and cooling so we need hot and cold water. An air-to-water heat pump can be electric or gas and it can provide hot and cold water. Alternatively, you can use a boiler to provide hot water only for heating, and those can be electric or gas. Finally, for cold water only, you can use a gas chiller. Let us know if you have any other questions!