Climate and security for art

Luigi Berti*

The Municipal Art Gallery of Cagliari is a remarkable example of integrated design, implemented in the context of a magnificently restored building that respects the values of its origin.

The Municipal Art Gallery is located in Cagliari in the public gardens, north of the Castello district.  The main facade was built in 1828, while the original building block, the first headquarters of the Royal Gunpowder company, dates back to 1700 and was turned into a permanent art gallery in the late twenties in the 1900s.  The building is built on two floors with a rectangular planimetry and a central section from which the two symmetrical wings branch out. The ground floor, in addition to the exhibition hall, also houses the offices and reception area.  On the first floor, there are exhibition halls and offices.  In total there are fifteen rectangular exhibition rooms, of different sizes and volumes, with no natural light.
The Gallery boasts an outstanding collection of works by 1900 artists, including the Ingrao legacy, with works by Ardengo Soffici, Umberto Boccioni, Filippo De Pisis, Giorgio Morandi, Ottone Rosai, Francesco Messina, Felice Casorati, Mino Maccari and many more.  There is also a collection of Sardinian ethnographic material.

The restructuring works

The restructuring was completed a few years ago and was beautifully executed; it has enhanced the preserved artistic features, whilst providing the Gallery with a series of facility installations indispensable for the safeguarding of visitors and the works of art.  The facilities project, managed by Eng. Carlo Bernardini and his studio in Cagliari, in addition to the air conditioning, also involved the electrical, fire protection, lighting and security systems, and many more.  The following sections provide descriptions on the most important facility solutions as regards the HVAC industry.

Air-conditioning systems

The existing facilities at the Municipal Art Gallery in Cagliari comprised a system used to produce hot water and chilled water produced by a boiler and a refrigerator group, a distribution pipeline system and terminals in the environment installed to reduce accumulated heating loads.  This facility plant, however, was now obsolete and unable to generate the ideal temperature and humidity conditions in the various rooms of the building; moreover, it was not working and had been in this state for several years.
The facility system designed for the air conditioning of the Gallery premises consisted of a variable refrigerant flow (VRF) system, manufactured by Mitsubishi Electric, with a direct expansion air-air heat pump which allows the distribution of the coolant itself using just two small diameter tubes (gas and liquid) in order to provide maximum flexibility and ease concerning the composition and management of the system.  These facility systems have proved to be particularly suitable when renovating museums, as was the case with the Poldi Pezzoli Museum in Milan where, in 2003, a similar VRF system was installed and, more recently, its application was further confirmed in the technical rooms and the dimmer room at the Teatro alla Scala in Milan.  This application confirmed the compliance of Mitsubishi Electric systems with the strict and often critical requirements imposed by the need to protect works of art and artefacts of historical and ethnographic value.
In the specific case of the Municipal Art Gallery in Cagliari, the machines and components were astutely installed within the context of the restructuring, to ensure they would be almost invisible.  What’s more, we also used many prestigious air flow solutions in many of the rooms, with air channelling using circular and flexible tubes and small adjustable nozzle diffusers, which are totally non-invasive and of a unique aesthetic design; the objective was to conjugate respect for the formal values of the environments with a circulation of air flow that was able to meet all the requirements concerning the control of temperature and humidity conditions inside the rooms.
The refrigerant used in this system is R 407C, a fluid, as you know, which is completely harmless to the ozone layer (ODP = 0) and characterised by an extremely low contribution to global warming (GWP, Global Warming Potential).

Outdoor units

The plant system includes four outdoor units, located behind the main building, in a special fenced off areas which was suitably prepared to house the same, each of which could be connected to up to sixteen indoor units of different types and sizes, so that only and exclusively the flow of refrigerant gas actually needed to heat or cool the area served by the indoor unit was supplied via the refrigerating tubes, thus saving energy and, consequently, generating a significant cut in costs.  In this case,  internal units suitable for hanging on the office walls were installed, whilst floor-type units and other system channelled through  suspended ceiling sections were used for the exhibition halls.
The system therefore uses a cooling system that allows distribution of refrigerants that can be adapted to provide excellent solutions for all specific needs, achieving substantial savings in space and a noteworthy level of functional reliability.

Adjustment of Inverter capacities

By installing an Inverter control system it is possible to include multiple indoor units within the same circuit, with significant benefits for the entire facility; in fact, it is well known that traditional air conditioning systems need a total capacity equal to the sum of  maximum loads in each room.  In many buildings, however, quite considerable lags occur in relation to the moment when each individual room reports its own maximum load.  Thanks to the inverter system, however, costs are cut in two different ways: first, it allows the installation of a number of indoor systems whereby the sum of their nominal capacities is between 50% and 130% of the rated capacity of the outdoor unit to which they are connected.  Secondly, it allows you to standardise the operational activities  of each internal unit according to the immediate environmental conditions  in the environment in which it is installed.  On the extremely rare occasions when all the indoor units are required to operate perform at maximum potential, the Inverter control will split the yield provided by the outdoor unit equally among all such units.
All this, combined with the fact that the hermetic scroll compressor of the outdoor units are equipped with linear frequency controlled inverter (variable between 20 Hz and 115 Hz), which makes the adjustment from 12% to 100% of rated output of  outer section, and that you have installed a LCD remote control in any environment in order to drive the individual internal sections by setting the desired temperature and humidity conditions, has allowed this air conditioning system to respond optimally to the requirements of temperature control of this  particular museum environment.
One must bear in mind, however, the fact that it was for the installation of a system of management of the whole plant, built with a central control unit connected to the remote control units and outdoor environments of the individual, in order to carry out a check on all  their functions from a single point in the building, enabling the management of the more simple and straightforward.
The design solution developed to take account of the architectural and aesthetic values that the Municipality of Cagliari wished to safeguard necessary for a building like the one in question.  For this reason we have designed special indoor and outdoor routes for the passage of the air conditioning ducts and identified the type and the best position to locate the various units responsible for maintaining the internal temperature and humidity conditions of  project in different environments.

Ventilation and heat recovery

As the space available to lay the various distribution networks used by all the new contracted plant systems was very restricted, we decided to realise a system of controlled mechanical ventilation in just one part of the building to ensure a minimum number  of outdoor air exchange units in the environments hosting art exhibitions.  This system consists of a number of heat recovery machines and a network of channels for the distribution of the outdoor air within the environment through appropriate terminals.  However, due to the fact that for architectural reasons, it was impossible to construct suspended ceiling on the ground floor, whilst on the first floor the space available to create suspended ceilings was very limited, the facility system was installed only in the lateral areas where it was possible to install the heat recovery equipment.

Conclusions

The design of the above described facilities (and others, such as the elevators which were deliberately omitted from this article) was able to exploit a high level of integration, making it possible to comply with and satisfy all the requirements and objectives set by the Customer, i.e. restructuring the Art Gallery and ensure all-round protection for the exhibited works of art.  In particular, the integration of VRF air conditioning systems has proved to be particularly positive, and their level of functionality has surpassed all relative expectations.

* Studio Bernardini, Cagliari