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The attention paid to the energy efficiency of the building, together with the improved
efficiency of PV modules, will help in including PV in the buildings design (e. g. by
reducing the surface area of PV modules needed).
A chronological view of smaller residential Net ZEBs exposes a tendency to reduced
sizes of PV systems during the last years. Improved efficiency of PV modules and
lowered demands of the buildings will move forward this trend.
The necessity of this is shown by the fact that so far, Net ZEBs have not been built
extremely dense, but mostly very flat. Net ZEBs with more than three storeys are rare,
as larger floor area mean higher consumption and, proportionately, a smaller PV area
per net floor area (figure 9).
It seems important that in the future in the development of new PV components for Net
ZEBs integration, the energy performance of the system as a whole is taken into account
(e. g. roof systems with high energy performance as insulating materials).
4.3 The use of PV in listed buildings
Developing innovative approaches to energy retrofitting of existing and listed buildings is
necessary in order to avoid several of them from becoming technically obsolete which
leads to rising energy running costs and finally in some cases demolition.
Furthermore, from an economic point of view, the energy production, can be an occasion
to earn a budget useful for the building’s maintenance and operation. For instance, there
are several cases in Italy, where, being the feed in tariff for building integrated
Photovoltaics very effective, public schools (big surfaces for PV) can earn money by
selling the energy they generate.
In the energy retrofitting of existing buildings several challenges appear, most of them
related to merging the technical systems with the construction and with the architecture.
Establishing solar systems on buildings or nearby is a design challenge that can be
handled but only if care is taken; the possible design approaches depend very much on
the cultural heritage legislation that varies in different countries.
There are examples of attempts at addressing this issue in a serious way where the
necessary design input have been applied for the purpose of a complete rethink of
alternative strategies. Architects who retrofit existing buildings are to the best of their
ability normally trying to handle existing constructions with care and to add positive
elements of architectural merit to them where possible and necessary. This is the case
of historical, but not listed buildings, even if part of a listed area of a city or of a
landscape, where it is possible to transform parts of the building envelope (figure 10 and
figure 11). [Scognamiglio 2009b]
But, in the most extreme cases where existing buildings are protected by the antiquarian
authorities as listed buildings it is very often impossible to change any part of walls or
roofs. The envelope will remain static. In such cases, definitely in Grade 1 listed
buildings any energy producing system will have to be positioned at a distance from the
listed buildings or invisible (e. g. CHP inside the building). In many countries there is in
addition a “banned zone” around the building, at times this zone is defines by a 360
degrees and 60 meter distance (radius) from the building.
There are examples of attempts at addressing this issue in a serious way where the
necessary design input have been applied for a complete rethink of alternative
strategies.
In this case, the only possibility is considering on-site energy generation systems,
designed to be in a formal relationship with the building, and as a part of the site design
(figure 12).
