Conclusion

This section is a conclusion on the entire investigation on modelling of floor heating systems.

Discussions of the individual sections have been included in the sections.

The following results have been achieved:

- As basis for the results, the simulation program FHSim has been used. The program has proven useful for modelling floor heating systems by coupling the floor with floor heating to the room model where the room temperature is calculated. Thereby, dynamical

calculations of the conditions in the floor heating system are possible.

- The two-dimensional model has been validated against measurements from a small and narrow building showing that the required simulation could be simplified from a three- to a two- dimensional analysis by introducing the characteristic dimension of the floor as the width of the model. This has previously been shown only for buildings without floor heating. It is also shown that the smaller the characteristic dimension, the higher the relative extra heat loss compared to a model without floor heating.

- It is important to use a dynamical simulation coupling the detailed floor model to a room model for finding the correct heat loss to the ground. Therefore a dynamical inclusion of the temperature in the pipe of the floor heating system cannot only be used to correctly model the temperature and thermal comfort in the room and energy consumption – it is also important for correctly finding the heat loss to the ground.

- The heat loss from the floor construction and foundation is larger in a building with floor heating compared to a building heated by other means and especially the linear thermal transmittance has a large impact. Additionally, it is shown that a poorly insulated

foundation is more critical for a house with floor heating than one which is heated by other means.

- A calculation of the linear thermal transmittance including floor heating based on dynamical simulations has been compared to standard methods. This dynamical

calculation resulted in larger ψ-values, which means that the standard method does not give a conservative estimate for floors with floor heating as it is supposed to. Moreover, the dynamically calculated ψ-values also depends on the energy consumption in the house. An interesting investigation would consequently be to establish a calculation procedure for the linear thermal transmittance where floor heating is included.

- A higher supply temperature to the floor heating system resulted in higher energy

consumption. However, here it must be noticed that the larger energy consumption led to higher temperatures in the room above the set point temperature – a result of inefficient control.

- The last section investigates different modelling techniques, both simple models with only a few nodal points and a detailed two-dimensional model. Generally a comparison to the two-dimensional model showed that all other models had lower energy consumption and heat loss to the ground. One reason for this is that the influence of the foundation is typically not included, which in this chapter has been found to be important.

- The simulation time in the different models range from a few seconds to half an hour for one year of simulation – a relative difference of approximately 1:100.

- A simple thermal network model can include the linear thermal resistance as an extra heat loss term from the concrete deck. This method is by far the simplest, yet it has results that are close to those found using the detailed two-dimensional model.

- An electrical inclusion of the floor heating pipe has shown to underestimate both energy consumption and heat loss to the ground compared to models with a hydronic

implementation of the pipe due to more efficient control and a system that can be turned off immediately. Further, the method cannot model a given supply temperature. The system is therefore not particularly useful for hydronic floor heating.

- Using a serial coupling of several identical simple models to include the cooling in the length direction of the pipe has proven not to be needed – at least not with the heat losses that are used in the models. A single model has proven able to also finding the return temperature from the pipe.

- The inclusion of extra ground volume below the floor construction in one-dimensional models to include the dynamics of the ground volume does not influence the results.

- The method supplied in EN ISO 13370 where the heat loss is split into a stationary and a dynamic part is not useful for models with floor heating since the adiabatic ground

boundary condition means that the floor is always heated and the functionality of the floor heating is therefore not going to be realistic

6 Thermo active components

The thermo active system has so far mainly been used in buildings where the deck has been in-situ cast, which is the typical building tradition in the Central European countries where the system was first introduced. In the Danish building tradition buildings are most often based on fabricated building elements. Therefore, one aim of this work is to investigate pre-fabricated decks where the thermo active components are integrated already in the production.

In section 6.1 the use of pre-fabricated decks designed as thermo active components is described.

In section 6.2 a simple way of integrating thermo active capabilities in an existing pre-fabricated deck will be investigated using a simple test setup. The activation of the deck is achieved through placing a pipe directly in the air cavities in the deck. However, the heat transfer in the cavities is not as effective as pipes integrated in the concrete and at the same time difficult to predict by simulations. Nevertheless if such a setup should prove to have a cooling capacity, which is large enough to cool the building, it would be a very simple way to make a thermo active component.

Thermo active components based on pre-fabricated hollow core decks is tested in section 6.3 in a large test mock-up. The measurements will be used to find the maximum cooling capacity of the decks and to validate the simulation model used by TASim.

Finally, in section 6.4 a simulation study using TASim will be presented.