Thermal Transmittance Measurements of the Historical Masonries: Some Case Studies

Abstract

The background shows that intervention on historical walls highlights the difficulty of identifying design solutions that are effective and compatible due to the lack of specific data on the thermal characteristics of the specific contexts investigated. This determines the choice of design solutions that are frequently inadequate and unsustainable from an environmental and economic point of view. Starting from acquired data a methodology has been developed that is based on in situ experimental investigations able to return the most probable value of transmittance of the historical walls. The values measured on the samples analysed do not reflect the literature data. For some of the samples analysed, the measured transmittance is lower than the one recorded in literature of about 10–15%. For the remaining ones, there are no reference values. The importance of an in-depth knowledge of the real behaviour of an existing historical envelope of a building is therefore fundamental, given that any evaluation mistake can have serious consequences from both an economic and environmental point of view. Underestimating the transmittance of a wall implies a waste in the use of available resources but also the disposal of greater quantities of building materials in relation to the end of life. The developed methodology can be easily replicated in other contexts and extended to all building elements that make up the historical envelope. The study will be continued by analysing further samples in order to create a reference knowledge database accessible to researchers, professionals and organizations.

Moisture Influence on the Thermal Operation of the Late 19th Century Brick Facade, in a Historic Building in the City of Zamora

“…The higher the water content, the greater the value of the thermal conductance. In the case of brick walls similar to the ones studied, the thermal conductance can be two to three times higher in a saturated wall than in a dry wall [29], because the water content they can absorb is high.…”

Experimental characterisation of the periodic thermal properties of walls using artificial intelligence

“…The stationary thermal transmittance method contains procedures for making appropriate estimates for existing walls as long as the walls are in adequate states of repair. Rotilio et al [32] found differences of 10%e15% between measured and estimated values for walls damaged by earthquakes and other eans. There are, however, no acceptable methods for determining all of the variables that affect periodic thermal properties, although some methods using hot boxes have been used to characterise these types of variables [33].…”

Assessing the Environmental Impact of Thermal Transmittance Tests Performed in Façades of Existing Buildings: The Case of Spain

“…This is a method used in many studies: (i) Lucchi [30,31] assessed historical brick and stone walls with the heat flow meter method. The results showed that the heat flow meter method allowed to characterize correctly the thermal transmittance of the walls, while the theoretical method overestimated the results; (ii) Rotilio et al [32] also showed that the most suitable method to assess the thermal transmittance is the heat flow meter method. In their study, the authors obtained overestimates of up to 15% when the theoretical method was used; (iii) Asdrubali et al [33] analyzed six walls designed following bio architecture principles.…”