Villa Castelli is a listed building from the 19th century located at the riverside of Lake Como (Italy). The owners set the ambitious goal of renovating the Villa, which had belonged to the family for about 140 years, to the lowest possible energy demand while maintaining the original use of the rooms and the external appearance. The renovation achieved a 90% energy demand reduction and a significant increase in comfort, demonstrating that also a listed building can become nZEB.
The villa is under formal protection in two respects: the building is listed in the land-use plan as a building worth preserving and as part of the riverside landscape, it is situated in a protected area. During the planning phase the planning team searched for a direct contact and exchange with the heritage office. Usually the process for developing heritage compatible retrofit solutions was that the planning team was proposing a solution to the heritage office and in case they declined, the planning team proposed a new solution (often several times) until it was approved.)
The exterior wall in local natural stone masonry with lime mortar was insulated from inside with 20 cm perlite, applying on the existing lime plaster layer another layer of lime plaster as leveling layer, the glue, the perlite insulation panel and the interior plaster. For the wall construction with internal insulation the moisture transport was simulated (WUFI). In addition, all nodes were designed and planned in detail with special attention to air tightness, vapor diffusion and convection.
A very substantial part of the work has focused on the restoration of the facades. It was based on a careful analysis of the state of conservation and an exchange with the conservator about suited restoration techniques, materials and colors. We started with a general cleaning of the facade with traditional restoration techniques. All structural cracks were sealed with a special kind of lime based mortar. The micro cracks were sealed with the introduction of silicates by the use of syringes. The surface plaster was consolidated with a filling of silica materials. The intervention, conducted by a team of specialized restorers, was completed with the restoration of the hoof on ground floor and the repainting of the plaster in the area of the veranda.
- U-value (pre-intervention) [W/m2K]: 1,33W/m²K
- U-value (post-intervention) [W/m2K]: 0,19W/m²K