Cork-based mortars for thermal bridges correction in a dwelling: Thermal performance and cost evaluation

• Minimization of energy consumption and condensation effects in a dwelling from the 1980s.
• Contribution of cork-based mortars for thermal bridge correction.
• Based on the original design stage of the existing dwelling, different scenarios were investigated.
• The influence of electric energy cost and its annual growing rate in Portuguese buildings.
• This analysis will enable to choose the best solution from a technical and economical point of view.

The aim of the present work was to simulate the behaviour of cork-based mortars in the minimization of energy consumption and condensation effects in an existing dwelling from the 1980s built in Lisbon, Portugal. Tests were carried out on hydraulic lime mortars and cement mortars with several proportions of cork as regards rheological characterization, thermal behaviour in and water vapour permeability. The first assessment of the behaviour of an existing dwelling showed that the power of heat dissipation in the dwellings’ thermal bridges is of the same magnitude order than heat loss in roof and much higher than in vertical opaque envelopes or openings, which enhances the need to reduce thermal bridges in the building. The selection of the most adequate mortar was then carried out in view of several scenarios. The best solution corresponds to the correction of thermal bridges using a Hydraulic lime mortar with 70% of cork granulate (CH70). An economic evaluation was also done concerning electric energy cost and its annual growing rate in Portuguese residential buildings. The results show that the use of CH70 mortar for thermal bridge correction has a payback of 3 years when compared to the simple repair of the original external plaster.