Villa Castelli

Restauration: The façade has been completely restored according to the input requirements of the heritage authority: cleaned, consolidated (acrylic resin with brush and syringe), missing parts supplemented in original technique. For a perfect function of the internal insulation special care was taken to close all joints and cracks. Sealing: The exterior walls have been sealed, injecting at high pressure a micro emulsion of concentrated silicones into regular drilled holes at a height of about 0,5 m above the interior floor level. The horizontal sealing of the baseplate was then pulled up on the interior sides to the level of horizontal cut in the exterior walls. Static consolidation: In order to consolidate the building statically, in certain areas the existing ceilings were removed and replaced by timber-concrete composite slabs, which distribute the loads better and reinforce the building itself. Detail planning/hygrothermal simulation: Based on the holistic pre-intervention survey, the individual components and junctions were analyzed and solutions were developed within an integrated design process, which included energy efficiency as well as thermal bridges, the correct humidity behavior, architectural aspects and static specifications (earthquake resistance!). The critical points in the design planning as well as in the execution of the construction work were certainly the high number of different nodes (about 30 pcs.). To simplify the design as much as possible, the planning was limited to two internal insulation thicknesses (20 cm perlite and 8 cm aerogel, where geometrically required). The moisture transport in the wall construction was simulated for both interior insulations (with WUFI). In addition, all knots were planned in detail and with special attention to airtightness, vapour diffusion and convection.

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An airtight building envelope was important in two respects: firstly, to ensure that the interior insulation was not damaged in the long term and secondly to limit ventilation losses in view of the location exposed to the wind. The installation of a comfort ventilation system ensures optimum air hygiene (primarily CO2 concentration, but also room humidity). Particularly when using internal insulation, a continuous layer airtightness layer all around the building envelope is crucial in order to avoid condensation of warm room air behind the internal insulation or in construction nodes. In case of the external wall, the internal plaster forms the airtight layer, whereas on the underside of the roof the vapor barrier under the internal gypsum plasterboard and on the baseplate a foil under the subfloor on the XPS insulation forms the airtightness layer. In all points where this continuous air-tightness layer is interrupted/penetrated, e.g. by ceiling beams, detailed solutions were be sought individually to guarantee air-tightness.

A mechanical ventilation system with heat recovery was installed. It guarantees a pollen-free, healthy indoor environment and improve the comfort indoor for the users. It controls the air humidity in the rooms, given that the building is lying in a zone closed to the lake. A set of CO2 sensors regulates automatically the air exchanges and the heat exchanger allows a further reduction of the building energy demands. The mechanical ventilation system is centralized at each floor, in order to guarantee the independency of each flat. Thus, three centralized comfort ventilation units with 480m³/h per unit and a heat recovery of 87% (according to the passive house certificate) were installed.

The heat pump also supplies the air conditioning. It must be emphasized that the specific power of cooling is very low (soft cooling) in order to avoid condensation in the floor structure.

The heat pump with a geothermal plant (probes) generates also domestic hot water production. The hot water is stored in a 900 l buffer tank.

The remaining energy demand had to be covered locally and in a renewable way. Electrical energy is produced with a PV-system, integrated in the roofing and not visible from outside. Before the heritage authorities approved the PV system, several prototypes were developed for a roof-integrated and preferably invisible installation. The heritage authorities opted for the double-curled aluminum sheet covering of the roof - which is quite common for buildings of this age in a similar way - with integrated mono-crystalline PV modules, folded plates with integrated photovoltaic cells, of about 11 kWp. A sailboat outfitter supplied the extra-thin PV modules.

The heritage office in charge of the project has evaluated as fundamental criteria: (i) the aesthetic characteristics of the panels (color and surface finish); (ii) their geometric arrangement in relation to the shape of the roof surface and the orientation of the building (shape of the plant, modularity); (iii) the adherence and coplanarity to the roofing; (iv) the non-reflective surfaces; (v) the perceptibility from around, with particular reference to the road, lake and circus-standing landscape level. The design of the panel respects the triangular or trapezoidal shape of the roof surface, trying to promote as much as possible the perception of a homogeneous coating of the entire surface. All the panels have the same orientation, consistent with the general orientation of the building, in order to minimize their perceptibility from around.

Also micro wind turbines installed on the roof contribute to the production of electricity.

The brine-water heat pump (see also heating section) use geothermal energy to generate energy via three deep probes with 80 m each.