Energy Efficiency of historic building
April 24, 2013
Improving energy efficiency in the historical heritage is an urgent and topical issue, now undervalued by the legislation, which tends to act more incisively on construction of new construction.
The European Union wanted fairly ambitious goal of 20% reduction in greenhouse gas emissions compared to 1990 levels and energy consumption by 20% compared to the levels in 2020, as well as for increasing the use of renewable sources for get 20% of total energy production (European Commission, 2008 and 2010), requires an integrated approach on existing buildings and new construction.
Recent studies (Eurostat, 2009; Cresme, 2011; Fasano, 2011), in fact, have shown that act by imposing limits on consumption only to new buildings is not enough to achieve these goals. The intervention to improve the efficiency of existing homes, most clearly in the case of goods identified as belonging to the cultural heritage, always poses a fundamental question related to the risks of a transformation that could lead to a decrease in the value of the building material and immaterial.
The evaluation of the energy efficiency of historic buildings is an issue not yet fully resolved, because the tools and criteria available to the designer are geared primarily to the needs of the new buildings. The ancient buildings, however, have a very different physical functioning as the lack of air conditioning systems and lighting required a conscious exploitation of local natural resources. The buildings are adapted to external weather conditions thanks to the breathability, strength, thermal inertia of the enclosure. For this reason, in temperate climates, the walls of old buildings are made with locally available materials and equipped with a good water vapor permeability and stratigraphy thick. The increase in thickness, in fact, improves endurance performance and thermal inertia (ie the lag time and the rate of attenuation) of the wall, providing a fair standard of living and welfare of users in the indoor environment.
The theme, to date, is addressed according to different perspectives in European and national legislation, in financing measures of redevelopment, in scientific research and in clinical practice.
First, European legislation (Directive 2002/91/EC, Directive 2010/31/EU) opens two distinct scenarios for the existing building type monumental and widespread. In the first case, you can resort to one simplistic use of the instrument of the “exception” that allows you to maintain the reduced energy performance of historic buildings of monumental type, or monumental buildings, places of worship, monuments protected as part of a designated environment or because of the special architectural or historic merit, in that the measures could generate “unacceptably alter” the historic character and appearance of the building.
At Community level, therefore, it is recognized that the undifferentiated and uncritical application of restrictive energy efficiency parameters on the monumental buildings can result in serious conservation problems, while not entering into the merits of the matter to be left open to interpretation by each State in respect of the culture and national legislation on the protection of cultural heritage. In fact, this has encouraged the uncritical spread of the derogation which was accepted “to remove the problem,” while, on the contrary, should be an opportunity for a conscious modulation of the project and for taking action on the basis.
In the second case, the existing building of the diffuse type is entirely subject to compliance with minimum energy efficiency performance particularly restrictive and not easy to get in old buildings. In particular, in buildings above a certain size, the restructuring should be seen as an opportunity to increase the energy efficiency of the whole building or parts of it.
The policies have been implemented at the national level without significant changes compared to European addresses.
In Italy, also, the alignment of legislation poses no substantial differences in terms of performance requirements to new construction and existing buildings, with the exception of the monumental buildings in which you can use the tool of the exemption (Legislative Decree no. 192/2005 and integrations). In all other types of existing buildings, the means of intervention depend on the size of the property. 1.000m2) is necessary to respect energy efficiency requisites for the winter heating, for the envelope and for thermal plant. In high-rise buildings (S> 1000m2), observe the energy performance requirements for space heating for the building envelope and the heating system. In buildings of small size (S ≤ 1.000m2), however, the only legislative constraint is given by the adoption of ‘minimum thermal transmittance of walls “, but do not include analysis on the global building-plant system.
The project built on the Italian legislation requires action according to a prescriptive directed to the individual technical element, considering the retrofit energy as the sum of individual actions carried out on parts of obsolete or inefficient. This logic can cause serious problems for the conservation of the property or of its parts, favoring the adjustment performance and the replacement of the individual components (windows, glazing, the vertical walls, roofs, …).
The typical example is the replacement of existing windows with more efficient systems, instead of maintaining the existing frame and replace only the glazing.
Basically in the current ITALIAN legislation there are two scenarios:
• monumental buildings: You can use the instrument of exemption, in accordance with Community law and national law;
• historic buildings but not monumental: it requires compliance with legislative requirements, which provide performance measures differentiated according to the size of the building.
The problem of protection of historic buildings has become even more serious because of the system of economic incentives and financial measures in the efficiency of existing buildings, which currently has no effective regulation also designed according to the protection and enhancement of property . Even in this case, it is required to improve the energy efficiency of a single component of the building.
Studies on energy efficiency have become field of research of the most popular and promising, but the art analysis shows that the relationship between performance improvement and energy conservation of historic buildings is a subject still little studied. Scientific research is structured into two separate strands that are:
• the technical energy audit;
• a method of identifying the most appropriate retrofit for existing assets.
In assessing the energy efficiency of existing buildings, the studies focus on energy audit procedures, techniques and instrumental diagnosis on energy simulation software, without placing specific attention to the historical heritage. In contrast, experimental studies on the non-destructive diagnostic performance characteristics (infrared thermography, sonic analysis, environmental monitoring) are applied mainly to the monumental architectural heritage. We note, however, the lack of a connection between the two disciplines that belong respectively to the physics building and architectural restoration.
A second line of research particularly common at European level concerning the energy and environmental retrofits to be implemented on the existing buildings.
A project of particular interest in this context is “3ENCULT Efficient Energy for EU Cultural Heritage” which seeks to identify a number of passive and active solutions to redevelop energy buildings of the Modern Movement, in order to prove that energy efficiency, structural protection, welfare of the occupants and conservation of cultural heritage elements are interdependent in the energy retrofit project. The approach is project-oriented, in that it suggests the most appropriate measures to increase efficiency for modern building, the designer trying to show that there are many design alternatives other interventions traditionally considered to be thermal insulation and replacement plant.
In the countries of Anglo-Saxon prevailing tendency practical application through the publication of numerous books aimed at managers, planners and the general public with the aim of explaining the most appropriate practices for the conservation and management of heritage. In them there are also suggestions for good behavior and user solutions energy improvement of existing assets (Inglese Heritage and Historic Scotland). Particularly significant examples are related to the drafting of guidelines to govern the application of the tax legislation and the incentives for energy efficiency for historic buildings.
Italian studies, however, is to identify actions to improve performance of the individual parts of the building envelope, as required by legislation. Of particular interest is the study carried out by the Green Building Metadistretto Veneto Veneto District and the Consortium of Cultural Heritage (2010), which places strong emphasis on all aspects of upgrading the energy efficiency and environmental sustainability of local historical heritage, giving operational guidelines for the designer.
Italian Green Building Council is developing an environmental certification system following the protocol Leadership in Energy and Environmental Design is dedicated to historic buildings (“Protocol LEED Historical Building”). The goal is ambitious as it aims to change the traditional methods of design, construction and management, in order to create places in harmony with the environment, healthy and that improve the quality of life. It is a complex system of environmental assessment, which considers variables to scale urban and building. The areas of interest, similarly to what happens for the “Protocol LEED New Construction”, relate to the sustainability of the site, the efficient management of water, energy and atmosphere, materials and resources and indoor environmental quality. For each category being defined indicators that allow you to get the environmental credits. The transferable elements include the introduction of a fundamental concept related to the coherence between the policies of sustainability and urban reuse involving the reduction of waste in land management, the importance assigned to the management and implementation of sustainable energy retrofits adaptable for their reusability future.
To date, the prevailing approach has been to roll out regulations containing requirements ever more demanding, often designed from the design of the new. As was the case for other interventions, the sectoral approach has so far been poorly mediated application to historical buildings, where the project must deal with a variety of aspects related to the usability of the cultural values of the building, use, duration over time, as well as the safety, accessibility and all ‘energy efficiency.
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