Seismic BuildTog++ in brief
Italy is a seismic country so earthquake are a serious problem for the Italian constructing sector and for population’s safety. ALER BCM owns about 600 buildings located in seismic zone 2 (high risk level).
A big part of those areas are close to Grada Lake. Seismic risk it ‘s not the only problem for Italian Housing Stock.
The most of the buildings are more than 40 years old and with poor energy performance. Most of them have been constructed before the first regulation for energy saving, so they are in the energy class G (the worse in Italy).
The additional problem in social housing sector is that almost the majority of the dwellings are occupied by tenants, but renovation it is not allowed. For this reason invasive works are not possible
The project site will be composed by two twin buildings. Both of them host 5 dwellings and are three floors high.
The challenge and the targets
ALER Brescia aims to renew two buildings, located in Toscolano Maderno. The renovation is quite challenging since there are some very strong constrains:
- they are located and there is no possibility to relocate tenants;
- the aim is to reach a seismic adaptation, that means reach the standards nowadays compulsory for new buildings;
- the budget is limited
- energy efficiency target is for a first intervention step 50 kWh/m2.year and with a second step down to NZEB
- there must be a specific attention to LCA
Due to the boundaries explained above the solution that has been identified is based on a double skin facade. The double skin facade is meant to be an exoskeleton to improve both the seismic and thermal behaviour, moreover it can change the facade layout.
The baseline project is:
- seismic improvement (adaptation of building to what is required by current legislation)
- energy saving (now the energy consumption is 200 kWh/m2year, the first target is to reach 50 kWh/m2year and the second step is to transform the building in a nZEB)
- architectural quality (the exoskeleton is designed to extend the building’s life cycle).
They are starting with geotechnical and geological analysis and materials analysis.
Aler BCM is facing with local specific regulation, because the buildings are close to Garda Lake, so there is a special regulation to preserve landscape.
Aler BCM studied different solutions with different costs level, finally decided not to use second skin facade, but only insulation layer because local regulation doesn’t allow to change external facade. So Aler decided to create an exoskeleton in adherence to the existing building, made by steel columns.
Flying expert workshop - Manchester 2019
During the workshop came to light some doubts and some advices about the project, the main topics are showed below.
Solar panels could be put on some facades.
The project must consider the fire protection problem. Is better to use mineral wool for the insulating system.
Specific calculation about the internal and external insulation must be done to reach the NZEB target. Is better if there is much insulation on the outside face.
It’s too early to think about a new heating system.
Ventilated facade can improve the energy efficiency during all the year.
Take care about the foundation and stairs connections.
The exoskeleton connection could create thermal bridges, because they interrupt the insulating layer. Is better to use insulated connectors or an independent exoskeleton.
Elevator structure could improve the whole building structure.
Is important to design sun shading system in Garda Lake area.
There is the risk of “non residential” feelings with some design of the exoskeleton.
Green references like Bosco Verticale could be taken.
The exoskeleton can create new volume, new shapes.
Is it possible to create new spaces for new dwellings? This could be an economical input to support the investment.
Flying expert workshop reply and discussion - Treviso 2019
During the meeting in Treviso ALER BCM show the feedback to the flying experts workshop andsome important consideration regarding seismic problems came to light during the discussion.
The retrofitting cost of this building is 1 million € more or less and the seismic retrofit is the 80% of the cost. The building is seismic zone 2, a critical zone, but not the worst in Italy. There are regional policies to help seismic retrofitting: if you make both seismic and energetic retrofitting you can have 85% of tax incentives.
It’s easier to consolidate an old building than a building like this (built in ‘70s), because in historical buildings all the walls are structural, so it’s easier to link them together than in case of concrete frame structure.
In Italy it’s impossible to standardize the solutions for different buildings, because materials and conditions change a lot, for example different grounds or different building shapes need different solutions. It is possible to define a standard approach and adapt it for different buildings and different places.
In UK they stabilized the ground before the construction, but they considered only static effects, not dynamics.
In France there are 5 seismic zones and there are different laws for different type of buildings (hospitals, schools, homes…) like in Italy.
In Germany, Sweden and UK there is a moderate seismic risk.