keoto | Realization economic and ecologic retrofit of 2 office buildings Zürich

Realization economic and ecologic retrofit of 2 office buildings Zürich

Building owner: Miteigentümer Rämistrasse 42 / Wolfbachstrasse 5, c/o Ecoimmobilia AG, CH – Winterthur
Project: zero emission retrofit + monument conservation
Period: October 2012 – Dezember 2014
Phase: Architecture Energy-Concept, Building, Monitoring
Characteristics:  deepest Borehole in Zurich, 550 m

Object description


The building at Rämistrasse is listed in the Monument Protection Inventory of the City of Zurich. This means that the scope of protection is not defined, but renovations to the building façade must be discussed with the Office of Monument Protection. According to the Office’s assessment, the casement windows needed to be protected during any intervention on the façade.


Heating is currently provided by a conventional oil-based system. Two boilers supply four groups (3x heat distribution/1x ventilation) in total. An air conditioning and ventilation system serves the Jecklin shop and is currently not in operation. During operation in summer, excess heat in the shop is exhausted to the environment through a heat exchanger in the upper floor. Heat distribution in both buildings is supplied by radiators. The store is additionally supported by an air-heating system.

Renovation concept

Building envelope

No energy- or construction-related measures are planned for the building envelope in the upper floors. The renovation of the ground floor will change the thermal characteristics of the shopping area, that is, the insulation will be improved.

New heating and cooling system

A new brine/water heat pump is planned. One of the existing oil boilers was integrated into the concept as a backup system. The heat exchanger on the roof will be taken out of service and dismantled. The cooling of the shop is integrated in the new system by using the ground as a heat sink. The cooling load of the store is supplied through large area heating and cooling ceiling panels. Using the heat pump to supply the hot water demand is not included in the plan. Four deep borehole heat exchangers (1 x 550 m + 3 x 450 m) are planned as a low temperature heat source for the heat pump. The heat exchangers are of U-tube type. In order to increase the total system efficiency, new heat convectors were installed in the upper floors. Coupled with radial ventilators, these convectors increase the heating power capacity of the system. Therefore, in spite of the old building envelope, the maximum flow temperature of the heating systems can be kept at 45°C, thus ensuring a high COP. The operational efficiency will continue to be improved in the following years through monitoring the building operation.