IAQ 2003, Presentation 27:
The Problem of Heating Churches Without Generating Negative Impact on Artworks
Dario Camuffo, Emanuela Pagan & Stefano Sofia
Many artworks and historical objects in churches and other historical buildings have adapted to the natural microclimate that has been kept the same for centuries. The materials have lost elasticity and reversibility, so that any departure from the original conditions is dangerous and has a cumulative effect that, in the long run, becomes visible. The recent church heating, mainly operated at broken times, constitutes a tremendous challenge for conservation of this extremely important cultural heritage. Despite an extensive literature, deterioration mechanisms are not fully known. Often the dynamic regime established with weekly heating cycles associated with release of moisture from people can generate conflicting situations: the sharp warming of the air causes a drop in the relative humidity, and artworks with short-time temperature inertia (e.g. paintings on canvas) are dehydrated and contract. On the other hand, the walls for their slow response remain cold, below the dew point, and part of the moisture emitted by people condenses on frescoes, decorations and mortars, with negative consequences. Smoke from candles and incense deposit on paintings and decorations blackening all the surfaces. Unfortunately, wood, ivory and parchment are extremely sensitive to temperature and especially humidity changes. The reason of the rapid decay of works of art, which occurs nowadays in churches, is that all materials expand or contract because of heat and humidity excursions. This mechanism is even more dramatic in the case of a rapid change of temperature or humidity, since steep gradients are formed from the outer surface of an object. The surface layer, which is most affected, is deformed differently from the innermost levels, giving rise to great inner tensions, that then turn into superficial micro- or macro-cracks, or the outer layer detaches from the underlying ones. A novel heating system, i.e. FRIENDLY HEATING, able to contain heated air just in the area where people stay is under study, supported by the EC. The heating system can be adjusted for the human well-being and heat and moisture will kept in the controlled area far from the works of art on or near the walls which remain absolutely safe. This avoids the problem of the excess of moisture condensing on cold surfaces, as always occurs when people are concentrated in rooms normally unheated, or heated at the occasion of the happening. For this reason, it will also be possible to operate the heating system at some selected time intervals, without risk of thermal shocks to artworks. The proposed heating has the clear advantage of providing an efficient conservation strategy for indoor cultural assets based on preservation measures and constitutes a useful tool for the sustainable management of cultural heritage. The first results of this research are illustrated.
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