Not all floor heating systems are created equal

Energy efficient Nereus floor heating for Finnish homes with 20 years of experience

During more than 20 years, Nereus Oy has developed its operations and products to meet the energy requirements of the Finnish building code. In practice this means a manifold customised for one-family houses, correct tube sizes and extensive experience on planning floor heating.

The energy efficiency requirements of buildings have become tighter during the past years by more than 35%. This means that heat insulation has to be improved, air leaks must be reduced and the annual efficiency of ventilation must be improved.

For a heating system, increased special requirements primarily mean that the overall heating efficiency requirement becomes smaller, as do the annual consumption of heating energy and the cost of energy consumption. In practice, the reduction of required efficiency means smaller dimensions of heating devices, both physically and in terms of efficiency. For heat distribution, reduced need of efficiency implies smaller water flows, for example.

As a result of decreased requirement for efficiency and flow rates, the adjustment range and accuracy of the circuit valves of the floor heating manifold are more important than before. In addition, the tube size is important. Also local circumstances must be taken into account in the planning (southern vs. northern Finland). Nereus has long experience on observing the conditions as well as possible in every part of Finland.

Circuit-specific control valves are used in the manifolds for adjusting the water flow of the floor heating circuit according to the requirements. The control valves are physically small, so accurate adjustment results should be obtained with minor changes of the valve position. This can only be achieved if the control range of the valve is small enough and in the correct range. In modern houses, the correct adjustment range is 20–120 l/h.

In one-family homes, Nereus uses a Finnish manifold developed in cooperation with Oras. Its most important quality is its small water flow rates (< 120 l/h). The adjustment section of the Nereus manifold circuit valves was improved in 2006 to become even more accurate in order to reach the flow rates required currently. It can now be said that the water flow of every heating circuit in a one-family house can be adjusted accurately with very small changes of the valve position within the adjustment range of the Nereus manifold. This creates an even temperature in all rooms. The fourth version of the Nereus manifold is currently being marketed and sold to Finnish one-family homes, taking into account the Finnish weather conditions and building regulations.

A large adjustment range (such as 30–900 l/h) makes it practically impossible to adjust the water flows. The flow may be many times higher than the calculated even with the smallest adjustment value. As a result of this, too much water flows in the heating circuits, resulting in uneven heating and excess use of energy.


In practice, the energy efficiency requirements mean that if the heating requirement of a house was, say, 8 kW, it is 5.2 kW after the implementation of the new regulations. This means a decrease in the total water flow from 864 to 540 l/h. When this flow is distributed among 10 circuits, for example, the water flow rate is approximately 50 l/h.

It should also be observed that many of the current sources of heat (ground heat pumps, heat exchangers) are equipped with automated circulation pumps. They control the water flow in the heating network according to the actual heat requirement. In the spring when the sun is shining, for example, the thermostats of floor heating are turned off and the flow rate can drop even to a half. Manifolds with large adjustment ranges become even more inaccurate and difficult to adjust (loose open circuits “steal” water).

A Nereus planner calculates the correct water flows for the manifolds that are subsequently adjusted with the line control valves of the manifolds. The control valve is equipped with a numbered disc that is simply set to the calculated preset value. Making adjustments is easy as no tools are needed for adjusting the heating circuits or line control valves.

Adjusting the correct water flows also sets the circulation pump of the building at a correct rotation speed, saving electricity needed for the pump.

“Warm and energy-efficient floors with more than 20 years experience”