**6. Discussion and simulation examples**

With all that we have expounded thus far, the reader is in the position to extract useful consequences to find the performance of radiation in buildings, either existing or projected.

Using his original software, based on the former section, the author has conducted a wide variety of simulations around the world. Most of them were validated by means of direct monitoring, both automatic and manual where available.

However, some provisos have to be taken into account. First of all, it has been assumed that radiation is emitted in a diffuse manner following Lambert's law. While this may be true for many materials especially modern ones, when dealing with heritage buildings such properties may not be accurate. In fact, the reflectance of surfaces at no longer extant architectural spaces remains largely unknown.

Even more difficult is the question of glazing in ancient buildings. Transparent glass panes which follow quantum dynamics in transmitting radiation are relatively modern. An added constraint is the fact that, recently, a wide variety of systems capable of selective or holographic transmission has been made accessible to designers and builders.

The main solution has been to define a directional or volumetric transmittance for glazing. This is a similar concept to the well-known photometric curve and gives us the spatial or spectral properties of glass-emitters. For the time being, these transformations can only admit bi-ellipsoidal form in the author's software.

For these and other reasons, interferences of radiation like diffraction and scattering, though predictable, are not handled in their entirety. Fortunately these phenomena are not very common in the building industry, especially because they may lead to visual discomfort and are generally avoided by users and designers.

This situation is convenient for the treatment of several building features that perform as radiation filters such as canopies, awnings, louvers and even courtyards or reflective ponds. For instance, in a system of louvers it is possible to isolate the volume seen in figure 18 and treat it as a single space with three virtual faces. Once the radiation that reaches the surface of the glass is obtained, the procedure is the same as for a room without louvers but the emissive power used for the window is the previous value and not the one applicable for

In this way, most of the problems derived from the geometry of the design are solved and radiation filters can be properly evaluated. Previously they were only considered

With all that we have expounded thus far, the reader is in the position to extract useful consequences to find the performance of radiation in buildings, either existing or projected. Using his original software, based on the former section, the author has conducted a wide variety of simulations around the world. Most of them were validated by means of direct

However, some provisos have to be taken into account. First of all, it has been assumed that radiation is emitted in a diffuse manner following Lambert's law. While this may be true for many materials especially modern ones, when dealing with heritage buildings such properties may not be accurate. In fact, the reflectance of surfaces at no longer extant

Even more difficult is the question of glazing in ancient buildings. Transparent glass panes which follow quantum dynamics in transmitting radiation are relatively modern. An added constraint is the fact that, recently, a wide variety of systems capable of selective or

The main solution has been to define a directional or volumetric transmittance for glazing. This is a similar concept to the well-known photometric curve and gives us the spatial or spectral properties of glass-emitters. For the time being, these transformations can only

For these and other reasons, interferences of radiation like diffraction and scattering, though predictable, are not handled in their entirety. Fortunately these phenomena are not very common in the building industry, especially because they may lead to visual discomfort and

holographic transmission has been made accessible to designers and builders.

the unobstructed orientation.

Fig. 18. Subdivision of louvers in a protected window

**6. Discussion and simulation examples** 

architectural spaces remains largely unknown.

admit bi-ellipsoidal form in the author's software.

are generally avoided by users and designers.

monitoring, both automatic and manual where available.

obstructions without any potential to add for the energy balance.

Once the radiative transfer is settled for a given space through its geometric and optic features, the amount of renewable energy available is known. This may become an important figure in the energy analysis or may have a thermal or visual correlate. The visual results are more intuitive than the thermal ones.

To find the temperature field due to radiation on a surface, Stefan-Bolzmann's law has to be invoked and significant differences with the luminous domain emerge. The first and more relevant one is that the temperature of the surfaces considered has to be found or estimated since there are no elements at 0 K in buildings. The author's and other correlations help in this respect but may not be definitive. A second proviso is that reflectances for thermal radiation are not similar to those in the luminous domain. Fortunately, most of them fall into the range of 0.9 for interior building surfaces.

Finally, if due to ventilation a convective field coincides with that provided by radiation, the latter, according to our experiments, will not be significantly altered in the short term because what is mostly affected is the thermal sensation.

With all the former in mind, the author would like to present the simulation cases of two paradigms of ancient Roman architecture, whose accurate radiative performance was largely unknown: the Pantheon and its superb baroque evolution the Church of Sant'Andrea all Quirinale. The architect and sculptor of light Gian Lorenzo Bernini completed this masterpiece, considered to be his own spiritual retreat.

Following the discussion of radiation in centralised spaces, a building currently under construction, the new railway station at the airport of Barcelona (Spain) is briefly presented in an effort to show how simulation can help in the design process and assessment.

Fig. 19. The Roman Pantheon illuminated by diffuse radiation of an intensity of 10000 lumen/m2 (lux). A typical situation in autumn and spring. Scale 0 to 400 lux

Fig. 20. Sant'Andrea all Quirinale's Church by Bernini (Rome) illuminated by direct solar radiation in winter. Values in lux(0-800)

Fig. 21. Sant'Andrea all Quirinale's Church. Section under direct solar radiation in winter. Values in lux(0-1600)

Fig. 20. Sant'Andrea all Quirinale's Church by Bernini (Rome) illuminated by direct solar

Fig. 21. Sant'Andrea all Quirinale's Church. Section under direct solar radiation in winter.

radiation in winter. Values in lux(0-800)

Values in lux(0-1600)

The final case to be introduced is the Rautatalo building of 1955, by the modern Finnish master Alvar Aalto. Originally a department store, it beckoned Helsinki's citizens by its intelligent use of luminous radiation, enhanced by conical skylights subtly adapted to the solar path in this northern city.

In the first two examples, luminous radiation is nuanced and constant for the lower spaces. It is outlined that the values for the Pantheon were not significant (sometimes, under 200 lux) and this fact may have led to the introduction of vertical windows in the drum of the cylinder by late Renaissance or Baroque epochs. Radiative performance does not show an acute seasonal variation, but allows for sunshine to reveal certain decorative details of the structure adding to the reputation of spiritual luminous atmosphere that encompass the work of Bernini. A hall of more than 300 square metres featuring a consistent level of 800 lux with only nine carved windows and the magnificent lantern is remarkable for the 17th century.

Fig. 22. Section of the new railway station in Barcelona. Radiation design by the author. Project by the architects Cesar Portela and Antonio Barrionuevo. Values in lux (0-600)

Changing the scale for the modern requirements of transportation spaces which have become the cathedrals of our time, the author proposes a lighting design in which the oculus reaches a diameter of 35 metres and the radiative energy is distributed by means of massive aluminium louvers with a height exceeding 3 metres in total. The simulation shows good levels and an acceptable raise of temperature at the glazed aperture due to the mild climate of Barcelona.

Fig. 23. Plan of the railway station in summer. Values in lux

The last example, the Rautatalo building, brings the reader back to the efforts of the modern movement in architecture to control radiation. With 40 skylights it was subsequently adapted to many projects around the world, which generally speaking fared less well than the original for climatic and economic circumstances.

Fig. 24. The Rautatalo building of 1955 by Alvar Aalto, Helsinki. Simulation of 40 skylights (8\*5), performed in June with direct sunlight and monitored on 21st of June 2011. Values in lux

Fig. 25. Solar Chart of Helsinki. Latitude 61.16 degrees north

This climate-responsive building would remind the reader that, in order to produce universal results there is the need to consider local weather parameters.
