Retrofitting with heat pumps in buildings
Executive Summary I Introduction The potential market for heat pumps for retrofitting in existing heating systems is substantially larger than for application in new buildings. However, in most countries, this potential is far from being realised. This report provides an overview of what is being done to overcome the technical market barriers, in particular to find solutions for the high distribution temperatures which are often required for existing hydronic heat distribution systems. Retrofitting is a means of rectifying existing building deficiencies, improving the standard of a building and, sometimes, making it suitable for alternative uses. It reflects the need to maintain and preserve the building for a longer period of time than the life of its technical equipment. Building retrofit often includes replacing the heating system. Heating systems may also be retrofitted without changing the building itself. Retrofitting of heating systems with heat pumps has its own specific problems, of which the high distribution temperature used in existing hydronic distribution systems is the most prominent. This report provides possible solutions to these problems. Cooling is not considered in detail. The geographical focus is on northern, western and central Europe, as the challenges with high-temperature heat distribution are typical for these regions. II The market The potential market for retrofit heat pumps is about three times larger than the market for heat pumps in new buildings. The new building construction rate is about 2% of the existing building stock annually in most countries. If a heating (and cooling) system needs to be replaced after 15 - 20 years of use, then 5 - 6% of the existing building stock is confronted with the need for a retrofit every year. However, in most countries the real market for retrofit heat pumps is substantially smaller than the market for their applications in new buildings. Even in the USA, only about 50% of unitary heat pump shipments replace existing heating and cooling systems (see Section 3.1.2). In the USA, heat distribution is by ducted air systems in most existing buildings, and consequently the barrier for incorporating the heat pump in the existing distribution system is expected to be smaller than in most northern and central European countries. In Switzerland, only about 20% of the heat pump market (