Hygrothermal Behaviour of Insulated Rammed Earth Walls

• Autor(a) principal: Jerónimo, Sara Alves de Melo
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/31863
• topic: Monolithic wall; Rammed earth; Hygrothermal behaviour; Polystyrene insulation; Hemplime insulation; laboratory test; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Civil

Rammed earth is an ancient construction technique for monolithic walls which consists in compacting raw earth in successive layers inside a formwork. The properties of the earth contribute to improve indoor comfort, acting as a buffer to relative humidity levels and internal temperature variations. Moreover, it has a low incorporated energy and it can be reused, contributing to a sustainable building industry. However, earth walls have a low thermal resistance when compared with other solutions used nowadays, which in some regions makes it necessary to add further insulation. The sensitivity of earth wall to moisture content requires the added insulation material to be sufficiently vapour permeable to allow the necessary moisture regulation of the wall. This dissertation aim is to measure in laboratory the behaviour of a rammed earth wall placed into a climatic chamber. In this regard, sensors measuring the temperature, relative humidity, heat flux and water content in different locations of the climatic chamber were introduced. The wall behaviour was monitored without any insulation and was then combined with two types of insulation materials: a synthetic and waterproof insulation board (polystyrene) and a bio-based plaster insulation (hemp-lime), both applied on the interior surface of the wall. The tests consisted in 8h cycles of defined temperature and relative humidity. The obtained results confirmed that rammed earth walls present high thermal inertia properties. With the addition of a polystyrene insulation on the interior surface, the wall is no longer able to release heat when the interior temperature drops, as polystyrene acts as a barrier and the vapour exchange is blocked. The hemp-lime plaster was added with the objective to include an insulation adequate to the vapour permeability requirements of the rammed earth wall. Due to the slow drying process of this particular insulation -with ~11% /month of relative humidity decrease- both the wall and insulation hygrothermal behaviours were not submitted to tests, being this left as future work.