Solar effects can be crucial for the energy performance of buildings, but how exactly can you map this? PhD candidate Miktha Alkadri managed to analyze even the surface and material properties of objects in the environment using 3D point cloud data. That enables smarter, computer-aided building designs.
The Walkie-Talkie building in the heart of London is a good example of how disastrous neglecting the sun can be. The mirrored skyscraper was nicknamed “Walkie Scorchie” when reflected sunlight was found to burn off the paint of cars and dazzle passersby. Another high-rise complex turned out to be designed in such a way that all furniture would blow away from surrounding terraces when a wind picked up over the river Thames. “Unnecessary, because nowadays we have technology to accurately calculate wind and solar performance effects in advance,” says Alkadri. “If those calculations are included in the architectural design process, such mistakes can be prevented.”
In existing practice, the calculation of the incidence of the sun is usually done with the aid of geometry. To what extent is the sun blocked after adding a block with a certain geometric shape? This method is time consuming and often neglects relevant surrounding information because it mainly focus on context-oriented buildings. Making 3D scans is simpler and and captures complex information from the existing context.
In principle, it is possible with 3D scanning technology to map the entire environment in one go, followed by performance simulations to calculate material properties of facades. “From point cloud data, our proposed computational method can identify whether an existing building surface consists of brick, glass or steel and where there are trees or shrubs.” This is important, because it gives an idea of the environmental impact that can be expected. Before the first spade goes into the ground, it is therefore clear whether a facade surface will cause discomfort or whether it may contribute to a “heat island effect”.
Resolution
3D scanning technology is nowadays mainly an aid in the reconstruction of cultural heritage. In his PhD research, Alkadri used the scanner as a supporting feature for the design process. With the Terrestrial laser scanner (TLS), he was able to map the environment to within 2 millimeters for single point accuracy per 10 meter distance. To reduce the calculation time, he diminished the resolution to 5 centimeters. “That is still robust enough to perform a good simulation.” By making two or three scans on the same day, a representative image of the environment is created. Every point in the cloud contains information about the position, the color and the intensity of the reflection.
Based on the point cloud data and the 'solar envelope' – the lines within which the sun falls – Alkadri developed two models. The SOLEN (Subtractive Solar Envelopes) model is suitable for a moderate climate and aims for a building mass that blocks the sun as little as possible. The SHADEN (Subtractive Shading Envelopes) model calculates how a building in a tropical climate can create maximum shade, to reduce energy consumption.
Calculations he made with this model for an Indonesian library project led to geometrical exploration and functional adjustments. The main reading room, which would get too hot, was moved to another floor while the meeting room moved to the back of the building.
Should we analyze every new construction project using 3D scanning technology? At this moment that is still quite expensive. “But the price of scanning technology is falling quickly, which is why this is a promising technology for the future,” Alkadri thinks. “It is much more expensive if you have to fix the design flaw with a secondary skin, as was necessary at the Walkie-Talkie building.”