A hydronic, or radiant, cooling or heating system uses water as the cooling medium instead of air, and this potentially offers many advantages.

In this module, we will look at:
- the challenges facing cooling and heating systems in buildings;
- how hydronic systems, or radiant systems, meet these challenges; and
- how the owner benefits from the added value high efficiency hydronic systems offer, compared to air-based systems. Let’s start with the challenges facing building owners.

Typical system issues, or challenges, facing building owners might include a compromised indoor climate, which can lead to:
- reduced working performance; and,
- poor compliance to climate legislation and other requirements.

These compliancy requirements are ever increasing, for example in relation to the United Nations Sustainable Development Goals, in particular SDG13 – Climate Action and reducing CO2 emissions.

Challenges related to indoor climate often have as their root cause the use of air-based distribution systems for chilled water or heating, which can decrease the indoor climate quality as well as occupant satisfaction.
Air-based HVAC systems for heating or cooling depend on high air volumes for energy transport and distribution, and high air velocities are often required to ensure sufficient heating or cooling to a building or room.

For occupants of the building, this can lead to:
- high noise levels from the increased air volumes and velocities; and,
- reduced satisfaction and compromised working environments, which again may lead to reduced working performance.

However, hydronic systems, or radiant systems, utilise the high energy density of water to transport cooling or heating in small pipe distribution networks, improving space performance in the building as well. Let’s look more closely at how a hydronic system works.

Because water based hydronic systems result in more pipes and fewer ducts, you get:
- reduced air volumes;
- smaller air handlers and smaller air ducts; and
- lower energy distribution costs.
And that is not all. There are a number of derived advantages of the hydronic system that are equally important."
With a hydronic system, the occupants of the building can enjoy an improved indoor climate compared to that in buildings with forced air systems. There are a couple of reasons for this.

In a forced air system, we have heard about how occupants often experience the following issues:
- too low or too high supply air temperatures;
- high air velocities;
- cold air drop;
- a drafty, noisy environment; and,
- occupants delivering a lower working performance.

Buildings with hydronic systems need much smaller air volumes. This means that:

- the air velocities used are lower;
- there is less draft;
- noise levels are reduced; and, in the end,
- the result is a better indoor climate and higher working performance.

From a compliance point of view, the building owner risks:
- lawsuits if indoor climate requirements and legislation are not complied with;
- additional time spent on solving indoor climate challenges during the design process; and,
- increased time spent on troubleshooting indoor climate issues during building operation.

On top of that, there is a potential risk of up to 50% energy overspend for cooling or heating of a building using an air-based system compared to the more efficient hydronic systems.

We have discussed how hydronic systems utilise the high energy density of water to transport chilled water or heating in small pipe distribution networks, improving space performance in the building as well. So, a hydronic system for chilled ceilings and floors ensures efficient, reliable and low-cost operation. Let´s recap the advantages of hydronic systems.

Firstly, disturbing noise, cold drop and draft is widely eliminated from the workplace because air volumes may be significantly reduced.

Secondly, a hydronic system enables increased use of high temperature sustainable energy sources for cooling and low temperature sustainable energy sources for heating, ensuring that future legislative requirements are potentially met.

Thirdly, hydronic systems offer a variety of advantages connected to the building’s HVAC system:
- Significantly reduced cost for energy distribution;
- Significantly reduced construction costs of ventilation systems;
- Reduced space requirement, because there are fewer ventilation ducts;
- Less time spent solving indoor climate during building operation; and,
- Increased end-user satisfaction and working performance.

In fact, you can save up to 35% on energy costs within a short time horizon with hydronic systems and achieve a faster return on investment with hydronic systems compared to air-based systems.

Basically, hydronic systems reduce energy consumption substantially and give you a faster return on your investment, and hydronic systems guarantee improved indoor environment for the occupants of the building.

Finally, as legislative requirements increase, for example in relation to SDG13 and reducing CO2 emissions, investing in a high efficiency hydronic system that enables use of high temperature sustainable energy sources for cooling and low temperature sustainable energy sources for heating, makes good business sense.