Case Study: nZEC - Energy refurbishment of 131 dwellings and new construction of 45 dwellings in Via Caldera, Milano, Italy (UNDER MONITORING)

Short Description

The project consists in both renovation and new construction of buildings. The buildings were built in the 1909 and in the 1960 and are currently occupied by 160 households, all with a contract of rent from the Cooperative. A significant share of the tenants is low income (retired or living alone).

The renovation process includes new roofs, facades, new windows, new thermal generation system with gas condensation boiler, removal of the domestic hot water and kitchen stoves which currently burn butane gas. The domestic hot water system will be centralized, the energy provided by the condensation boiler (natural gas) and by a solar thermal system. There will be a monitoring system to measure consumption of heat and hot water in each dwelling. New electric induction stoves will replace the old gas stoves, a choice which will improve also security.

One of the existing buildings will be demolished and replaced by 2 new buildings with high energy performance and innovative solutions for the division of internal spaces.
A new car park will be constructed underground, while the surface space will be converted to green. In general, all the space on the ground level will be restored and reorganized i order to facilitate and incentivize socialization. Architectonical barriers will be demolished, new lift will be installed

Key Elements

Certification

Each household will have access to its own consumption. A clear information about own consumption is the first step towards technological and life style improvements which could lead to concrete energy saving results.

Project Management

Different renovation options have been evaluated to identify optimal results. Maintenance works is a variable which have been considered in the different scenarios. It has been challenging to find the right balance between investment costs and energy savings, considering that the development is rather large and all the units are rented, generally to low income households.

Concerning the legislative aspect of the retrofitting process, every year the SHO Board of Directors must draw up a plan of maintenance of their housing stock, as a part of the medium-term program, which is presented and discussed during the annual General Assembly of Shareholders. This is required under the Statute of the SHO itself, in order to maintain the housing stock efficient and in compliance with the regulation in force. The individuation of technical and design solutions for retrofitting are not subjected to special preventive participatory process with tenants.

The proposals are prepared by the SHO Technicians, in accordance with the Board delegates to the topic. Then, the chosen technical solutions are illustrated to the tenants, whose consensus remains critical to the success of the work. The sharing by tenants is the result of proper communication strategy of the SHO staff and of the Board of Directors. The awareness of the inhabitants of what you do allows them also to better face the inevitable inconvenience that retrofitting normally involves.

Work with Residents

Tenants need time to "accept" the operational phase of the construction works, which will have impact on their lifestyle. To overcome this, an important role is played by the relationship between the cooperative and the tenants, which starts when the “future tenant” applies for a dwelling. The SHO not only provides a “home”, but a set of services: tenants are informed about the inner workings of the Cooperative, as well as about possible scenarios that could emerge over time (e.g., the renovation of the building where they wish to live) with all the possible effects both in terms of the increase of rent that with regard to the hardships (and the positive effects!) that a renovation may bring.

The involvement phase of tenants has been developed in different ways:

• when a building is upgraded, tenants already know that the rent is revised and increased to allow for the recovery of the investment, so no more “bad news” for the tenants who are confident in the SHO and do not impede the renovation process;
• several meetings were organized between tenants and designers in order to present the renovation project and share the architectural solutions (and thus have greater consensus);
• another way to inform is the SHO magazine- in the case of via Caldera even the direct dialogue with the technicians of the company, as the building is next to the offices of the SHO.
  
  
  

Heating and Hot Water

All roofs will be replaced, thermal insulation improved by mean of 10 cm thick insulation panels. No additional insulation will be added to the external walls, as this would have been too expensive for this project. 

Windows and Shading

The old wooden framed windows are currently being replaced with PCV frames and low emissivity double glazing.

Heating and Hot Water

The heating and hot water system will be completely replaced with a new one: 3 gas boiler (condensation technology), plus a third one for the sole production of DHW. Circulation pumps will be of the “inverter” type, which allow modulating the power in function of the actual need. Each dwelling will have a consumption meter for heating (ech radiator will have its own “allocator”, interconnected via radio waves to the others) and hot water (volumetric meter).

Solar Thermal

A solar thermal collector field will be installed on the roof, while the storages will be placed in the boiler room. When the energy provided by the solar system won’t be enough, the gas boiler will provide the remaining energy to heat the water to the required temperature.

Monitoring

Click here to access the monitoring data on the HIVE Database!

Funding

Energy efficient measures table:

Main Results

The building consumption has been monitored by web panel HIVE. The  comparison between winter 2012/2013 and winter 2013/2014 shows that there are very significant savings of about 36%. Savings have been corrected on the basis of the degree-days recorded last winter season, since it was milder that the previous one (-13.9%). Despite the normalization, heating savings are around 27%. This result is due to the replacement of all windows, which occurred during 2013. The Social Housing company expects a further improvement after the renovation of condensation boiler and the installation of thermostatic valves and energy meters in every flat.

Lessons learned

The housing company already manages solar thermal systems. Below, there is a list of lesson learned they kept in mind when designing this new solar thermal systems.

• The housing company decides to install two separated hot water storage boilers instead of only one (as they did in other buildings) in order to maximize the solar apport. In fact, from their experience, they recognize that householders mainly use the hot water when there is no solar contribution (in early morning or in the evening). Consequently the water is heated mainly by the condensation boiler and not by the solar one. Two separated boilers with a regulations system allow to use first the hot water deriving from the „solar“ storage and then the other one.
• Referring to solar thermal systems in multi-family centralized systems, it is very important to have a heat generator which is dedicated to hot water production, in order to reduce maintenance cost during summer, when heating systems are switched off.
• Maintenance cost is a crucial point: costs are acceptable, but the energy performance of the system should be carefully monitored, in order to promptly verify the plant settings.
• It should also be expected to carry out adequate insurance coverage, because hail and other weather events can cause serious damage to solar collectors that are quite vulnerable.
  
  
  

Additional Information

Ms Rossana Zaccaria
Legacoop Abitanti - The Italian Federation of Housing Cooperatives
E-mail: r.zaccaria@ancab.coop
Web: www.legacoopabitanti.coop