Single family House - Bern, Switzerland

A Zehnder comfort ventilation system with heat recovery has been introduced.

On the top floor, the supply air is routed via the screed into the built-in cupboards: apart from the inconspicuous supply air grilles in the cupboard walls (usually behind furniture), no architectural intervention in the rooms (pipes) is necessary. No audible ventilation noises.

The hot water preparation is carried out by the 2’840l tank, which is mainly supplied by the heat pump and the PVT system.

The system doesn't need conservation compatibility.

Two different types of STh have been used: special system on the lower part, PVT on the top of the roof (cfr. section PV)

Due to preservation orders, no conventional collectors were allowed. The collectors of the special system (lower part of the roof) are integrated in the underroof (layer battens and counter battens). External layer of the roof is natural stone plates, and the system is not visible at all.

Since originally no conventional solar system was possible due to monument preservation regulations, a collector that is not visible from the outside has been developed, with which the heat can be efficiently extracted from the natural slate roofing. 13m2 of natural slate collectors were installed, which corresponds to an output of about ~5kWp. The collector consists of copper lamellas, which are clamped between the slate plates. The heat is conducted via the fins into a soldered copper tube, through which it is dissipated via a glycol solution, as in conventional collectors. Due to possible condensation moisture and to increase efficiency, a 1 cm aerogel insulation, covered by a sub-roof foil, was placed between the roof battens and the slate. PVT and the natural slate collector systems are used to support the heat pump by increasing the water temperature into the heat pump improving the COP. The PVT and natural slate collector systems are also used to regenerate the geothermal probes/ground temperatures with excess heat available from the PVT and the slate collectors on multi-day to seasonal time scale (on diurnal time scale the solar tank is the heat storage). The regeneration thus increases the net solar electricity production and at the same time prevents the ground to cool down over time, assuring a constantly high COP over the lifetime of the geothermal probes. In addition, the cooled roof helps the rooms of the top floor to remain cooler in summer. This renovation deserved the Swiss Solar Prize 2014.

Roof-integrated PVT (13 m2) + roof integrated PV (5.5 m2) + STh natural slate collectors (13 m2)

Due to the high level of protection, solar panels are slightly visible from the street, leaving part of the original slate roof intact. During the refurbishment, the requirements of the preservation of historic monuments were somewhat softened, so that both PV+PVT system was possible on the flat (upper) part of the roof.

The arrangement of solar panels on triangular pitched roofs approaches solves the critical points with tailored solar modules with attention to detail and fixing systems. First 'optical' roof-integrated system with 3S Hybrid 900/240 modules. Optically' integrated into the roof, because the installation is integrated into the roof and flush with the eaves, but the solar system is not a completely tight roof skin. The actual dense and back-ventilated roof skin lies underneath, i.e. the installation is hybrid roof-integrated and 'on roof'. - Eight hybrid collector modules (13 m2) and 12 purely photovoltaic special modules (5.5 m2) on the southern, 25° inclined roof surface. - Electrical output: 2,728 kWp. Active cooling of the modules increases the annual electrical yield by up to 10%. - The thermal output of the hybrid collectors is at least 7.2 kWp (manufacturer's specifications).

Stove

In the building there was already a fireplace/stove whose only element visible from the outside was a chimney that came out in the north-west part of the roof. This chimneypot remained intact, while the gas boiler chimneypot was removed. The new stove is located in the living room and is connected to the central heating system.

The new heating system includes several interventions. The main source is the water heat pump, which is supplied partly by geothermal probes and partly by the PVT and the natural slate collector systems. Both systems are used to support the heat pump by increasing the water temperature into the heat pump whenever possible and thus to improving the COP. The water is stored in a 2840 L tank. It also works thanks to the stove. In addition, a 'Frischwasserstation' which contains a small heat exchanger to provide warm water (Brauchwasser) on demand have been installed which prevents the formation of legionella. The hot water of the solar tank is used to heat up the 'Brauchwasser' in the Frischwasserstation when required. From the tank the water is then distributed to the radiators and wall radiators.

Heat pump with bore holes

The execution in a geothermal heat pump is not very invasive for any building, in fact all the pipes coming out of the building are underground, while inside the building there will be a presence of greater pipes due, in this case, to the complexity of the system that combines several energy carriers. The use of more vectors allows a better management because it gives priority to the vector that has production potential at any specific moment.

The new heating system includes several interventions. The main source is the water heat pump, which is supplied partly by geothermal probes and partly by the PVT and the natural slate collector systems. Both systems are used to support the heat pump by increasing the water temperature into the heat pump whenever possible and thus to improving the COP. The PVT and natural slate collector systems are also used to regenerate the geothermal probes/ground temperatures with excess heat available from the PVT and the slate collectors on multi-day to seasonal time scale (on diurnal time scale the solar tank is the heat storage). This regeneration is a win-win situation: By cooling the PVT panels and transferring the excess heat (up to 12 kW) into the ground e.g. in summer, the PVT panels produce significantly more electricity (up to 500 W) than the pump required to transfer the heat into the ground (~50W). The regeneration thus increases the net solar electricity production and at the same time prevents the ground to cool down over time, assuring a constantly high COP over the lifetime of the geothermal probes. In addition, the cooled roof helps the rooms of the top floor to remain cooler in summer. The water is stored in a 2840 L tank. It also works thanks to the stove. In addition, a 'Frischwasserstation' which contains a small heat exchanger to provide warm water (Brauchwasser) on demand have been installed which prevents the formation of legionella. The hot water of the solar tank is used to heat up the 'Brauchwasser' in the Frischwasserstation when required. From the tank the water is then distributed to the radiators and wall radiators. The geothermal system includes two probes of 150 m each.