OLTRISARCO AREA - VIA ASLAGO - PROJECT ANALYSIS AND DESIGN SOLUTIONS
The site project is located in the Southern part of the city of Bolzano, in an area close to the Isarco River named Oltrisarco. The area is near the industrial area and it’s crossed by a highway and a railway. The site is located in Via Aslago and it’s about 7000 square meters. Actually the site consists in 7 residential buildings built during the ’40. IPES, the local authority responsible for social housing residences, planned to demolish those buildings and commissioned 80 new accommodations.
One of the main features of the area is the presence of the Kohlern Mountain located East, which significantly affects the shadowing of the whole area, especially during the morning.
Part 1: Shadows analysis
A. Shadows analysis – considerations
As we explained in the previous post, the East orientation represents a significant problem because of the presence of the mountain, so that the morning sun hardly irradiates the façades. As a result, we decided to invert the orientation of the present buildings in order to get a more correct enlightenment of the main façades.
Firstly we decided to make the shadows analysis of the project site in order to understand the solar exposition of the courtyards and squares designed. We considered several situations during the year 2015. We picked up the dates of the equinoxes and solstices and 3 different moments of each day (9:00, 12:00, 18:00).
This analysis brought us to some useful considerations. As it can be clearly seen, we have to figure out some solutions in order to improve the use of the squares and courtyards. During summer (21st of June) those public spaces seem to be quite hot, as they are completely enlightened for almost the whole day.During spring and fall the squares will be quite nice in the morning: although the sun is not so hot, they are well enlightened. On the other hand they are quite cold and shadowed in the evening. We also realised that the courtyards will be shadowed for almost the whole day during winter.
B. Design solutions
In order to improve the shadowing of the squares and courtyards during summer we decided to plant some trees. We picked up two different types: a birch, used mainly for the lowered squares, and a prunus pissardi, used for the rest of the site. This choice comes from the necessity to create masses with different heights and volumes, as they have to shadow different spaces.
We can make now a new shadows analysis within trees masses. We picked the most critical periods of the year – summer and winter – and we set a parameter in order to consider the different behaviour of trees while the different seasons. It can be noticed that trees concretely take part to the shadowing of public spaces during summer, while they don’t contribute to the shadowing at all during winter, when crowns are sparse.
In order to create a liveable space during winter, we decided not to plant trees on the terraced steps facing the park. It can be seen from the analysis that this area is the only one enlightened during winter. We designed it so that it can be enjoyed from residents during winter: people can sit and be heated up by the sun.
Part 2: Solar radiation analysis – ground floor
A. Solar radiation analysis - considerations
In order to make a deep analysis of the quality of public spaces, we decided to study the solar radiation on the ground. We analysed the solar radiation during the different seasons and made a comparison. The colour – based method analysis validates the studio we made while studying the shadowing. The solar radiation during summer is quite high – it peaks with 115 KWh/m2 between 12 and 2 pm – while it only reaches 35 KWh/m2 during winter.
B. Design solutions
Areas that need to be more shadowed from the summer solar radiation are the lowered squares and the private terraces. In addition to the choice of planting some trees, we are considering to use bright paving materials that can reflect the solar radiation, such as white stone slabs, spaced out in some places with green strips. In order to avoid mould, efflorescence and humidity stains during winter, especially in the places always shaded by the building, this paving should be weatherized.
Part 3: Solar radiation analysis – façades
- Solar radiation analysis - considerations
Then we chose to study the solar radiation of the Northern and Southern façades. As it can be seen from the pictures, the North facing façades don’t receive any solar radiation at all. Only buildings that are slightly rotated peak with a radiation of 50 KWh/m2.
The situation is completely different on the façades facing South. They receive a quite high solar radiation both during summer – which results to be around 150 KWh/m2 – and winter – 75 KWh/m2.
Then we considered the situation of the skywalk, which faces East and West. The West side results to be always cold, with a radiation that remains constantly around 10/20 KWh/m2. On the other hand, the East façade receives a quite high solar radiation during summer – around 150 KWh/m2 – while the number is low during winter - around 40 KWh/m2.
B. Design solutions
In matter of the treatment of Northern façades, which result to be very cold, we should adopt preventive measures in order to avoid deterioration signs. As it can be seen in the Northern elevation, we were thinking about dark stone slabs, able to absorb the slight radiation and the use of waterproof sprays to avoid humidity stains, mould and efflorescence.
The Southern façades present the opposite problem: the radiation is very high, so that we need to design appropriate shading systems. Luckily, South facing façades come up with the best situation as far as exposition is concerned, so that we can think about opening big windows on them. During summer, when the sun is quite high, they can be easily shaded with cantilevers, in order to let the light in but not the heat. On the other hand during winter, when the sun is lower, sun rays warm up the house. To sum up, those façades will be designed with big openings and terraces.
The radiation analysis of the skywalk’s façades shows that the Eastern façade needs to be constantly shaded because of the high solar radiation. We designed a vertical brise-soleil, capable to protect the skywalk, which runs all over the surface.
Part 4: Solar radiation analysis – terraces
- Solar radiation analysis – considerations
In the end, we decided to study the behaviour of the South facing terraces we designed during the different seasons of the year. We made a comparison between the solar radiation analysis and the shadows one during the most critical hour of the day, 12 pm.
On summer the radiation peaks with 49 KWh/m2 on the corner between the window and the façade, but the terrace results to be all shadowed, so that the space won’t be too hot because of the summer’s sun.
During the winter, when the sun is lower than the summer one, the radiation reaches 59 KWh/m2. The shadows analysis shows that more than the half of the biggest opening is enlightened, so that sunrays will warm up the house and the terrace results to be a quite nice space where resident can be heated up by the sun.
On spring the radiation is slightly lower than the summer one, but the terrace is enlightened for less than the half. This means that this space is a quite liveable place for almost the whole year.
B. Design solutions
In order to avoid the overheating of the façade during summer, it should be used a Low-emissive (Low-E) glass. As we explained in the previous post, it is a window glass that has been treated with an invisible metal or metallic oxide coating, creating a surface that reflects heat, while allowing light to pass through. This glass is obviously more expansive than a float one, but it’s coatings are proven to reduce energy consumption.
