Basic HTML Version
BCD Special Report on
Historic Churches
18th annual edition
17
contains a transparent submicrometric layer
of sputtered metal oxides. The electrical
resistance of the metal oxides causes them
to heat up when electric power is applied.
A thermostat maintains air temperature at
the desired level (usually 40°C) and a second
thermostat guarantees safety even in the case
of failure of the first thermostat. The glass
units provide thermal comfort by means of IR
radiation or direct contact with the back or
the hands. In front of windows or walls they
may counteract cold draughts passing along
cold surfaces. The units can attain an excellent
safety standard and resistance, so they don’t
need to be contoured by a support frame.
They are also easy to clean and maintain.
Heated carpet
(Figure 5) incorporates
a heating foil or element placed between an
insulating layer on the bottom to avoid heat
dispersion to the floor and a carpet-like layer
on the top. The top layer should protect the
heating foil against mechanical damage by sharp
objects, fire, water, etc. The surface temperature
should be low (typically 20°C) and should
provide comfort to feet but is unable to heat the
rest of the body, which should be heated with
other sources such as remote IR emitters (see
title illustration). The area of the church used by
the celebrant is warmed with heated carpets and
remote IR emitters from both sides to produce
even heat distribution. (For more details about
these solutions, see Camuffo et al, 2007, 2010).
Examples of how these concepts can be
applied to box pews are shown in the title
illustration and in Figure 4. Inside the box
pews, some heat sources (heating foils and/
or carpets for example) are located, but the
envelope is too cold to provide satisfactory
comfort. The box provides a thermal island,
protected against lateral draughts, but the
churchgoer’s face is exposed to the cold. For
this reason chandeliers have been installed
which contain electrically-fed IR emitters to
provide some benefit to the upper part of the
body. The aim is to supply a gentle distribution
of heat focused to warm those parts of the
body that are most susceptible or exposed
to the cold, rather than overheating one area
of the body while underheating the rest.
Conclusions
Unfortunately, the environmental conditions
that are most suitable for historic churches and
their contents are less suitable in terms of the
comfort of churchgoers. With low level heating,
these divergent needs may not come into
conflict, but when the environment becomes
uncomfortably cold, or heating is maintained at
too high a temperature, the two requirements
conflict and a compromise between the
two needs to be reached. The ‘compromise’
temperature may depend on the vulnerability
and value of the church fabric and furnishings.
However, if the requirements of
sustainability or fabric preservation mean
that the degree of heating has to be limited,
churchgoers don’t necessarily need to
suffer. Intelligent and carefully targeted
use of heating should mitigate the cold
environment and, as always, churchgoers
should be prepared to dress accordingly.
The Friendly Heating Project and later
related research produced invaluable analysis
and evaluation of all kinds of heaters from
the point of view of the conservation of
cultural heritage preserved in churches.
Among the project’s general conclusions,
the following points are worth stressing:
• reversibility of the installation should be
considered a priority
• conservation and energy saving are
mutually compatible but result in
temperatures that may be uncomfortable
for the congregation
• a compromise between the opposing needs
of conservation and comfort is necessary;
in the case of conflict, conservation should
take priority
• local heating is more energy-efficient than
central heating
• if intermittent heating is required, local
heating systems are less harmful to historic
fabric than central heating
• improving envelope insulation, reducing
heat leakage and wearing warm clothes
should always be the first step. Only
afterwards should the other heating options
be explored.
These basic concepts inform the European
Committee for Standardization’s new
standard: Conservation of cultural property
– Indoor climate – Part 1: Guidelines
for heating churches, chapels and other
places of worship (prEN 15759-1:2011).
Recommended Reading
W Bordass and C Bemrose, Heating your
Church, Council for the Care of Churches,
Church House Publishing, London, 1996
D Camuffo, Microclimate for Cultural Heritage,
Developments in Atmospheric Science 23,
Elsevier, Amsterdam, 1998
D Camuffo et al, Church heating and
preservation of the cultural heritage:
a practical guide to the pros and cons of
various heating systems, Electa Mondadori,
Milano, 2007
D Camuffo et al, ‘An advanced church
heating system favourable to artworks: a
contribution to European standardisation’,
Journal of Cultural Heritage, Vol 11,
No 2, 2010
Conference proceedings, Conference on Energy
Efficiency in Historic Buildings, organised
by the Swedish Energy Agency, Gotland
University, Swedish National Heritage
Board and Churches of Sweden, Visby,
9–11 February 2011
Conservation of Cultural Property –
Specifications for temperature and
relative humidity to limit climate-induced
mechanical damage in organic hygroscopic
materials (EN 15757:2010), European
Committee for Standardization, Brussels
ED Mills, The Modern Church, Architectural
Press, Princeton, 1959
L Samek et al, ‘The impact of electric overhead
radiant heating on the indoor environment
of historic churches’, Journal of Cultural
Heritage, Vol 8, No 4, 2007
Acknowledgements
This article reports the findings of the EU
funded research Friendly Heating Project
(EVK4-CT-2001-00067) and disseminates
the results of the activity of CEN/TC346
WG4 concerning European standardisation.
Dario Camuffo
is a physicist, research
director and lecturer in Physics for Conservation
at three universities. He is the coordinator or
principal investigator of 15 EU-funded projects
on climate and microclimate for cultural
heritage. He has investigated many buildings and
monuments on the UNESCO World Heritage
List and is a member of the technical committee
and task leader for ‘European standardization
for cultural heritage (CEN TC346)’.
Figure 5
Heated carpet composed of: (1) insulating layer on the bottom to avoid heat dispersion to the floor
(2) heating element (3) protective layer forming the underside of the upper cover (4) velcro fastener allowing
removal of the upper layer for cleaning or replacement (5) upper cover resembling conventional carpet