Sustainability Report

Sustainability information provided by Octavio Mestre, architect and chief executive at OMA Octavio Mestre Arquitectos.

Embodied carbon overview

• The intervention retains the existing building envelope and roof structure, with the addition of insulation to reduce the carbon footprint of the project. OMA Octavio Mestre Arquitectos highlights the environmental qualities of the original nineteenth-century construction, including stone walls approximately 70 centimetres thick that provide thermal inertia.
• All materials used are locally sourced, representing 90 percent of the project’s material palette. The timber used throughout the project comes from controlled logging forests. The original roof was insulated using Heraklith as part of the strategy to achieve a BBC building standard (Bâtiment à Basse Consommation) under French regulations.
• The project reports that 50 percent of materials were reused, while 40 percent of materials were responsible or certified. All work was carried out by local companies.

Operational emissions overview

• The project incorporates a range of passive environmental strategies. The existing 70-centimetre-thick walls help moderate interior conditions without reliance on mechanical heating or cooling.
• The carpentry is double glazed with thermal breaks. Exterior glazing is specified as low-emissivity insulating glazing with argon-filled cavities and CEKAL-certified systems. 
• Rooflights incorporate low-emissivity double glazing with a reported Ug value of 1.31 W/m²K, internal blackout blinds for solar control, and automated opening systems that provide smoke extraction and natural ventilation. New openings on the north-west facade support cross ventilation.
• The project reports an energy use intensity (EUI) of 80 kWh/m²/yr and a 35 percent reduction in operational energy consumption against the baseline. Renewable energy accounts for 30 percent of the project’s energy mix.
• The mechanical ventilation system uses heat recovery with a reported efficiency of 75 percent.
• Reported envelope performance values include:
• U-value of opaque envelope (roof): 0.227 W/m²K
• U-value of transparent envelope (windows): 2.5 W/m²K
• U-value of glass (whole number/absolute value): 1.5 W/m²K
• Solar heat gain coefficient (SHGC): 0.5
• Visible light transmittance (VLT): 0.4
• All lighting throughout the project is LED. 
• The project also reports a 50 percent reduction in water use against the baseline.