SaLüH! Renovation of multi-family houses with small apartments, low-cost technical solutions for ventilation, heating and hot water

New innovative concepts for heating and ventilation were investigated. Very compact heat pumps are developed in such a way that it will be possible to integrate these units into the window parapet or into a prefabricated timber façade.

Short Description

Experience show that in the renovation of residential buildings, which often have small apartments with very inhomogeneous heat supply (gas, oil or firewood stoves, electric boiler, etc., see e.g. EU project Sinfonia) a complete renovation including conversion to central heating and DHW Supply with e.g. connection to district heating, biomass boiler with or without solar thermal or groundwater heat pump is hardly possible. Measures inside the inhibited flats are often associated with number of complications (technical, legal, financial). Thus the centralization of ventilation, heating and domestic hot water (DHW) is often dropped. Unfortunately energy and cost efficient decentralized (and less invasive) solutions for mechanical ventilation (MVHR) and for heat pumps are also not available. Especially for residential buildings with small flats currently available decentralized solutions are often not feasible for space and cost reasons.

The aim of the research project SaLüH! was to provide housing associations, manufacturers of ventilation and heating systems and planners with concepts and development trends for a complete package for decentralized (flat wise) ventilation, heating and DHW supply. The concept allows for a cost-effective and simple (step by step and apartment by apartment) transition to energy efficient building services in the framework of the renovation, without restricting users in their usual living environment. A coordinated and complete renovation package consisting of thermal insulation, windows, a ventilation system with heat recovery, and heating (and possibly cooling) and domestic hot water supply was developed, which can be implemented inexpensively and with minimal intervention in the home. A simulation-based assessment of the concept with respect to the indoor air quality, the thermal comfort and energy efficiency as well as an economic evaluation was performed. Functional models for a compact hybrid mini heat pump for ventilation, heating and (optionally cooling) as well as a compact domestic hot water heat pump were developed optimized and measured in the laboratory.

In addition to the space required for the technical components for heating and DHW heating, the duct installation represents a further challenge during the refurbishment of buildings. The concept of active overflow, which with respect to the concept of extended cascade flow, offers a further reduction of required ducting and thus construction costs. The supply air is transported by means of active overflows (small sound-damped DC fans). Therefore, ceiling suspension in the hallway is not needed. The simplified air supply with active overflow elements was investigated systematically with focus on small apartments with decentralized wall-integrated heat recovery systems and design guidelines were developed. A functional model was created and measured in the laboratory with respect to the efficiency (power consumption) and sound emissions at different volume flows.

The ventilation and heating heat pump (compact ventilation unit with integrated mini heat pump) was designed in such a way that optimum efficiency, compactness and investment costs could be achieved. This variable speed mini heat pump with a heating capacity of about 2.5 kW uses the enthalpy of the exhaust air of a mechanical ventilation with heat and moisture recovery as a source. Limiting the air exchange to the limited hygienically required value are of high importance in particular in alpine space with longer phases of low ambient temperatures and correspondingly low absolute humidity in order to avoid or at least reduce the problem of dry indoor air and thus increase the acceptance of MVHR. The use of moisture recovery reduces the problem of dry air and allows higher air change rates. However, moisture recovery can hardly be regulated and care must be taken that it does not get too humid. A decoupling of the heating (or optionally cooling) power from the hygienic air exchange is achieved by means of additional recirculation of secondary air (heat sink side) and additional ambient air (heat source side). The power limitation of the supply air heating is thus largely eliminated and a significantly better controllability is achieved. Cooling is optionally due to the reversible operation of the heat pump and thus the increasing demand for increased summer comfort is addressed.

All components are mounted in a cost-effective foam casing with integrated micro-sound absorbers, which is easy to install. The system was designed to provide optimized flow control in terms of pressure drop and uniformity of flow and noise reduction. At the same time, the design enables a high degree of prefabrication and thus cost-effective production.

In this renovation concept, DHW preparation is provided by a compact DHW heat pump with a compact storage tank independent of the heating system. This compact heat pump can also be integrated in small bathrooms as a pre-wall installation, optionally in the parapet below the bathroom window or in a curtain wall. For this purpose, a modular unpressurised storage tank (90 l or 120 l) was developed. The charging of the tanks takes place via a loading circuit with flow control. The storage-unpressurised tank is combined with a domestic hot water station (so-called fresh water station). The compact mini DHW-HP is supplied on the source side via a brine air cooler (flat-wise source) or a brine bus (building-central source).

As an option, the integration of the active components in the existing window parapet or in a prefabricated timber frame façade was examined. The building integration (façade integration) offers in particular in small apartments with generally very small bathrooms and kitchens if at all, the possibility to realize a mechanical ventilation and switch to a modern and efficient decentralized heating system. In addition, the length of the ambient and exhaust air ducts can be minimized by means of façade integration, thereby reducing heat losses and saving installation costs.

In the outdoor laboratory of UIBK (PASSYS test cell), a functional model of a test façade with integrated outside unit of the ventilation and heating heat pump was installed and measured. The test façade on a scale of 1:1 (2.7 m x 2.7 m) was designed as a prefabricated timber frame construction. Together with the outdoor unit of the heat pump several temperature and humidity sensors were installed in the façade. In addition to the indoor laboratory experiments (performance and efficiency measurements), practical aspects such as handling and installation were tested and building physics measurements (sound emissions, condensate avoidance) were carried out. Building physics properties were evaluated by accompanying thermal (3D) and hygrothermal (2D) simulations.

Project Partners

Project management

University of Innsbruck, Unit for Energy Efficient Buildings

Project or cooperation partners

  • J. Pichler Gesellschaft m.b.H.
  • Arbeitsgemeinschaft ERNEUERBARE ENERGIE Institut für Nachhaltige Technologien
  • Internorm International GmbH
  • SIKO Energiesysteme Gesellschaft m.b.H. & Co. KG
  • Kulmer Holz-Leimbau GesmbH
  • Vaillant GmbH

Contact Address

University of Innsbruck
Unit for Energy Efficient Buildings
Fabian Ochs
Technikerstr. 13
A-6020 Innsbruck
Tel.: +43 (512) 507 63603