Study by Roberto Torreggiani (technical engineer for Giacomini Group)
Radiant floors can be divided in two categories: traditional radiant floors and radiant floors with low thermal inertia or reduced thickness. This distinction has an operational and applicative origin. This article describes reduced thickness radiant floors for new or under renovation buildings.
The main characteristics of low thickness radiant floors are:
- Reduced thickness compared to traditional radiant floors (considering insulation + screed + surface finishing)
- Lower inertia and, therefore, a decreased duration to reach the floor surface temperature and the desire room temperature.
- Under certain circumstances, it can be installed directly on pre-existing flooring as additional layer without any undesirable demolition.
Observations on the inertia in radiant floors
In physics, particularly in mechanics, the inertia of a body is the property that determines the resistance to variations in the state of motion, and this is quantified by the inertial mass.
Applying this concept to radiant floors is complex because there are many thermodynamic parameters that can influence the inertia of radiant floors.
The factors that affect the inertia of radiant floors are:
- Radiant floor characteristics (materials, thickness, thermal conductivities)
- Delivery flow temperature, flow rate, and temperature difference
- Initial temperature
- Room temperature to be conditioned
- Location of the room (inner or towards the outside condition)
A quick and precise method for calculating inertia is making a dynamic simulation with all the components of the system on floor sections.
Instead, if we want to carry out this calculation through an experimental analysis, we can measure, from starting temperature, how much power is delivered to the screed, and observing at the same time the supply and return temperatures, room temperature, and average surface temperature.
An example of the results that can be obtained is shown in the above figure above where the supply and return temperatures are shown together with the heat provided by the screed at the same time.
For low thickness panels, the time necessary to reach the desired surface temperature (lowest point of the green curve) is less than 30 minutes. For traditional panels, the time necessary to reach the same temperature is longer.
This factor must be taken into consideration while designing and setting the radiant system to ensure a desired temperature throughout the whole day in consideration of occasional use.
On the other hand, the aspect of inertia of the system is also important when turning off the system: a system with low inertia panels will take less time to cool down than a traditional system.
In a nutshell, the systems with low thermal inertia, along with offering more freedom in renovation works, can also suit to situations with high insulation.
Given the heating/cooling speed of radiant systems with low thermal inertia, they can make the most of free thermal contributions without the room overheating.
The impact of dynamic balancing manifolds in radiant systems with low thickness panels
Latest changes and trends in the market, with an increasing focus on energy saving, shows low thickness underfloor radiant systems can be complimented by coupling it with dynamic flow balancing technology.
It is in fact from the superimposition of the effect of low thermal inertia and the dynamic control of the flow rate that the best effects are obtained.
The dynamic balancing of the water flow has an important potential energy saving impact on the system that is often underestimated and neglected.
The goal is to make the dynamic balancing of the water flow easier to apply into new or existing systems application.
A system with Giacomini manifolds with dynamic balancing - DB series allows to keep the flow rate balanced in all the system, therefore reducing the risk of overflows and, resulting to significant energy saving.
In general, dimensions and applications are the same as standard manifolds, but the patented DB valve installed in each circuit can perform new various functions:
Flow rate regulation: when the pressure in the system changes, due to the opening or closing of some circuits, the diaphragm of the cartridge valve intervenes by changing the opening of water flow passage then adapting the flow to the pre-set value, even in the presence of high differential pressures: operation up to 60 kPa for the Low Flow versions; up to 150 kPa for High Flow versions.
Flow rate pre-setting: it is possible to set the max. desired flow rate for each circuit.
Room temperature optimization: The combination with electrothermal actuator heads and thermostats the temperature control is optimized at the highest level
To obtain an estimation of the energy saving with such technology, some studies have been carried out, among which there is the one of Professor Stefano P. CORGNATI, Professor of Technical Physics of the Energy Department of Turin Politecnico: "POTENTIAL ENERGY SAVING WITH DYNAMIC FLOW BALANCING MANIFOLDS".
The scientific study approach provided for design and development of an analytical-numerical model applied to two sample cases referred to as “individual” and “collective” model. The "individual" case reviews the typical situation of the actual effects occurring inside an individual housing unit, which may be a single-family home or an apartment with an independent radiant system.
Conversely, the "collective" case reviews the typical situation of collective/multi-family residential buildings (condominiums, for an example) with a centralized heating system where energy savings are linked to the energy consumption dynamics and behavior of the individual units.
Within the aforementioned simulation model, the action of dynamic balancing has a concrete impact in eliminating the overflows considered as overconsumption from pre-set water flow as the point of reference. This overconsumption corresponds to the ENERGY SAVING, and obtainable through the use of manifolds with " dynamic balancing of the flow ".
In regards with the two cases examined with the reference to calculation boundary conditions (input and characteristic parameters of the model), thus we have results of:
- the "individual" case, an example of the energy saving of housing units with independent heating system, showed savings on heating energy consumption of up to 12%;
- the “collective” case, an example of the energy saving of multi-family buildings with centralized heating system, showed savings on heating energy consumption of up to 25%.
The savings achieved are important and clearly establish the perfect application combination of low thickness radiant system and balancing systems.
This combination is not only true on a theoretical level, but also goes hand-in-hand with an application simplicity that makes the products suitable for easy, flexible, and massive applications; therefore, it offers important solutions for the mature and effective implementation of radiant systems with high energy saving.