Abstract
This paper describes the influence of thermal parameters—conductivity, transmittance, and thermal mass—in the estimation of comfort and energy demand of a building with rammed earth walls, and consequently, the compliance with standards. It is known that nominal design data does not match in situ measured values, especially in traditionally constructed buildings. We have therefore monitored a room in a building with rammed earth walls, designed a computerised model, and compared four different alternatives where we have changed the value for the thermal conductivity (in situ vs. estimated) and the consideration of thermal mass. When we then analyse the compliance with the Spanish energy saving code, using measured values would result in lower differences with the standards’ limits and even comply with the global thermal transmittance (K-value) requirement. This would mean a more realistic approach to the restoration of traditional buildings leading to the use of thinner and more suitable insulation and retrofitting systems, encouraging the use of rammed earth in new buildings, and therefore reducing the carbon footprint due to materials used in construction. Results show that the building model that uses in situ values and considers thermal mass (S1) is closer to reality when assessing thermal comfort. Finally, using nominal data would result in requiring 43% more energy in the selected winter period and 102% more energy in the selected summer period to keep the same comfort conditions as in the alternative where measured values are used.
Highlights
Understanding the thermal behaviour of materials is essential to achieve a correct energy evaluation of buildings, their demands, and the environmental impact due to the consumption of resources
In the first three methods, the analysis parameter has been the indoor dry-bulb temperature as it was the parameter that was measured for the whole period and that affects both comfort and energy demand of the room In the fourth method we have used the indoor operative temperature, which is the mean temperature between air temperature and radiant temperature
Compliance with the Spanish Energy Saving Code. We have studied this compliance for the versions used in S1 and S2, using a Spanish software called “CE3X” (Certificación Energética de Edificios) that has been developed by Efinovatic and the Spanish National Centre for Renewable Energies (CENER)
Summary
Understanding the thermal behaviour of materials is essential to achieve a correct energy evaluation of buildings, their demands, and the environmental impact due to the consumption of resources. The use of materials that have minimal impact on the environment during their lifecycles will contribute to mitigate the effects of climate change. One of these materials is earth, and its awareness in construction is high, its current use remains low [3]. In order to achieve an efficient use of materials in buildings, governments of many countries improve energy and environmental demands in construction standards. There is an application included in the Spanish Code that gives theoretical parameters of materials that can be used to execute approximate calculations and can help us analyse the behaviour of the building once it is in use [6]
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