HVAC Systems, Radiant Cooling

Radiant Cooling Mythbusters – Dispelling The Myths About Radiant Cooling

Radiant cooling is a technology that most architects and engineers are familiar with. For those of us living in cold or temperate climates, many of us may experience its effects on a daily basis. Yet, most know relatively little about the details of radiant cooling solutions, and just how effective it can be in maintaining thermal comfort in all manner of building types. Most are misled by the myths about radiant cooling out there.

As with most things we know little about, we usually fill the gaps in our knowledge with assumptions or half-truths to try and get a complete picture. In this blog we’d like to set the record straight by demystifying some of the myths about radiant cooling.

Myth #1: Radiant Heating & Cooling is a New Technology

Myth 1

There is a general misconception that radiant heating and cooling is a new, futuristic, high-tech technology. This is wrong!

Hydronic cooling was first recorded in China around 5800 years ago. In Korea, the traditional Korean home is radiant heated with an ‘ondol’, a technology with an equally impressive archaeological history of over 5000 years. Over in Europe 2000 years ago, the Romans also used radiant heating with their ‘hypocaust’.

Closer to the modern day, radiant heating was even used in the Battle at Winchester in 1864. A 500 tent hospital was erected that featured a unique radiant floor heating system which proved invaluable in the freezing winter months. To say radiant heating and cooling are new technologies would be like describing the Great Wall of China as a prime example of modern architecture.


Myth #2: We All Know Heat Rises


Let’s start this one off by saying, it’s okay if you think heat rises. You would be correct, heat certainly does rise, but the fact here is that not ALL heat rises, and that is a pretty important point to make.

Myth 2

If heat only rose then how could we possibly feel the warm glow of the sun or bask in the glow of a camp fire? We would have to stay on top of the sun to get warm! Radiant energy moves in any direction from hot to cold.

In a radiant heated and cooled home, the home is only warm or cool because its surfaces are warm or cool, and it makes no difference if the surface being conditioned is on the floor, ceiling or wall. Hot air may rise relative to cold air, but radiant energy does not. The main benefit of this is that radiant panels can be placed anywhere and still provide optimal cooling.

Myth #3: Radiant Cooling Causes Condensation


This is perhaps the most wide spread of all the radiant cooling myths out there. It’s understandable. All you have to do is lower the temperature of a surface below the dew point and condensation will

occur. For example, forgetting to close your fridge door properly will lead to water condensing on every surface of your fridge.

Myth 3

Let’s try not to forget what century we are in! With today’s building standards such as ASHRAE Standard 160 ‘Criteria for Moisture-Control Design Analysis in Buildings,’ we know we have to control the moisture of buildings that are designed and built.


So, what about buildings in hot/humid climates?


When one significantly reduces the temperature of a space in a building and creates cool surfaces that are below the dew point, condensation will occur. However, this is certainly not caused by radiant cooling as a method of cooling. Buildings utilizing forced air cooling systems such as HVAC (without appropriate ventilation and dehumidification) would result in the same phenomena.

The key to avoiding condensation when cooling, as with any building design, is augmenting cooling technologies with the appropriate use of ventilation and dehumidification. In this way condensation can be avoided. In doing so the thermal comfort is also vastly improved and the spread of viruses and bacteria reduced.

Myth 3-2

Case in point is the new, radiant cooled Bangkok (Suvarnabhumi) International Airport in Bangkok, Thailand. The climate at nature of this public space poses a particularly hostile cooling environment, with significant solar loads, high background humidity and internal latent (people) loads of around 12,000 passengers per hour. This challenging environment has proven that radiant cooling, with the use of radiant floors, can be used to cool the building effective, maintain thermal comfort and all without the fear of condensation!


Myth #4: Radiant Cooling is Really Expensive


Are radiant cooling systems expensive? Well, in short the answer is “NO”!


Energy Saving


Radiant cooling helps reduce the energy required to effectively cool a building and its occupants.

Myth 4

Energy savings are linked to the type of climate you are in and can vary between 17% in cool humid areas to around 42% in hot regions according to Lawrence Berkeley National Laboratory.

Another study done in Hyderabad, India, compared results from identical buildings owned by Infosys. The buildings, Software Development Building 1 (SDB-1), had a traditional HVAC and radiant cooling installed.

The bar graph shows the load requirements from different components within the building. It clearly shows a 40% reduction in energy required by the radiant system when compared to the traditional HVAC system.


Installation and Maintenance


The traditional thinking is that installing a radiant conditioning system is complicated and tricky. A fact which is simply untrue. Radiant cooling systems have developed more efficient manufacturing techniques to help reduce the cost of installation and make it simpler.

Myth 4-2

Uponor, has developed a prefabricated roll out mat that makes installation quick and simple. Radiant piping can also be incorporated into precast slabs incorporating it into the buildings design, helping to lower overall project costs.

Along with upfront costs, it is also important to consider the life cycle costs of the chosen cooling system. Forced air systems require continual maintenance work. Cleaning ducts, repairing fans and leaks all add to the systems costs. A radiant system uses significantly less moving parts. This means less cleaning, less maintenance and ultimately lower operating costs.


Myth #5: Radiant Cooling is Slow


Another popular myth is that radiant cooling is slow. To understand why this is nonsensical and untrue we have to understand the difference between thermal lag and thermal performance. Thermal lag describes a body’s thermal mass with respect to time.

Myth 5

The slow night-time cooling of a home after its external brick wall has been heated by the sun is one example of thermal lag. Thermal lag is the reason a day’s high temperature peaks in the afternoon instead of when the Sun is at its peak (12 noon).

Thermal performance is the response time of radiant transfer which is instantaneous. Thermal lag can be attributed to poor building performance or an inadequate radiant system.

A recent study of a radiant system install at the SKAI building in Hamburg, Germany, showed the building yielded excellent results. They recorded a drop in temperature from 33 °C to 26 °C in the space of 30 minutes.

SKAI Hamburg


Rebutting the Myths Surrounding Radiant Cooling


There is a lot of information out there on radiant cooling and radiant heating. Some good, some bad and some simply untrue. Hopefully we have managed to shed some light on radiant cooling and the myths that seem to surround it in this blog.

In summary:

  1. Radiant heating and cooling has been around for hundreds of years, from China, Korea and Rome to modern day Thailand.
  2. Not ALL heat rises. Radiant energy moves in all directions and is just as effective when used in hydronic ceiling cooling panels and when it is used in the floor.
  3. Radiant cooling, when used correctly does not cause condensation.
  4. Low maintenance requirements accompanied by an energy efficient hydronic system and prefabricated panels all contribute to making radiant cooling a cost effective, energy efficient and easy to maintain system.
  5. Radiant cooling certainly isn’t slow. A recent test done on a radiant cooling system designed by Uponor at the SKAI building in Hamburg showed excellent cooling times with a 7 °C drop in a mere 30 minutes.


Radiant cooling vs all air cooling eBook

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