What impact do different design decisions have on the solar energy potential of building blocks?

If you scroll down, you can find it out yourself. The page is set up in such a way that you can compare two different building blocks designs with each other.

Step 1

The first step is to set all parameters needed to obtain a result. The four parameters are configuration, density, orientation and roof type (please note that not all options exist yet). These parameters are explained more in detail on this page. All areas of the 3D building blocks are divided in 1 x 1 metre and an annual solar irradiation analysis was performed. Then, all areas where divided into the categories: unsuitable, reasonable, good and very good. The  following table shows how this division was done (Threshold values for different categories (values in kWh/ m²a)).





Very good




900-1 020

>1 020




900-1 020

>1 020


Design & orientation

Typical Swedish building blocks were taken to enable studying the potential of solar energy in Swedish cities. The dimensions were chosen to resemble the reality and are therefore dependent on the configuration. The available configurations:


The available rotations are 0°, 15°, 30°, 45°, 60°, and 75°. 0° means the block is facing towards South, and the other rotations are counter clockwise.


The Floor Space Index (FSI) is a well-used metrics by urban planners. The following picture explains the principle of the FSI. Assume there is a plot of land that can be built upon. If nothing is built, the FSI is 0. If a building would be built with one floor on the whole plot, the FSI would be 1. If the building would have two floors, the FSI would be 2. If the owners / developer do not want to build on the whole plot, then the FSI changes. The picture shows an example of different configurations with their FSI.

Comparing different FSI with each other might lead to complications; in some countries; it means that only the plot area where the building is built is considered, while in other countries, it might also include neighbouring streets or parks. In this study, the FSI is considered to be the area where the building is built upon plus half of the neighbouring street.


Roof type

The following roof types are simulated:


Step 2

The next step is reading the results

Results are divided in several parameters:

  1. A picture, showing the chosen options with the following colours:

    1. Unsuitable: White

    2. Reasonable: Green

    3. Good: Yellow

    4. Very good: Red

  2. SAFAR650 : Which is defined as the suitable area (Area receiving an amount of solar radiation greater than or equal to the preset threshold n) divided by the Floor Area of the considered building (m2). The higher the value, the more energy can be produced by solar energy.

  3. Two graphs showing how the roof (left graph) and the façade (right graph) is divided into the different categories. Hovering over the graph gives you the amount of square metres in the categories.

  4. The next two graphs shows how much irradiation reaches the roof and facades.

  5. The last graph shows how much the building blocks could cover their own energy use. To calculate that, the energy demand of the building block was calculated according to the Swedish building code BBR and according to the Swedish passive house standard FEBY. Then, the scenario was taken that all surfaces on the building envelope which were classified 'good' and 'very good' were used to set up active solar energy system (with a 50% PV/ST ratio). Ultimately, the ratio "produced energy / used energy" was calculated.