​​​​Rationale

The term 'deep renovation' in accordance with the EU Energy-Efficiency Directive is a cost-effective refurbishment that reduces both the delivered and final energy consumption of a building by a significant percentage compared with the pre-renovation levels; typically more than 60% energy saving as indicated by the European Commission Staff Working Document SWD (2013) 143 final. ‘Cost-effective’ means that higher energy performance is resulting in the lowest cost during the estimated economic lifecycle of the building, and a quick Return on Investment (RoI) for implemented solutions through energy savings. The definition of deep renovation applies within the framework of major renovation, which means: more than 25 % of the surface of the building envelope undergoes renovation; or, the total cost of the renovation of the building envelope or the technical building systems is higher than 25 % of the value of the building, excluding the value of the land upon which the building is situated.

The ultimate success of deep renovation can only be proven in the building’s long-term sustainability; and therefore, the energy performance goals of deep renovation are achieved when the building optimally fulfils its functional and user requirements throughout its lifecycle. P2ENDURE ensures that public and residential buildings are functionally, technically and socio-economically viable at all times –through transformation of the building’s typology and function at deep renovation.

There is also a very important economic driver for deep renovation with transformation of public buildings into dwellings next to the energy-saving rationale. A large stock of such public buildings (including office, public service, commercial and historic buildings) has become vacant since the beginning of the economic crisis in 2008. Maintaining the vacant buildings is a critical financial burden for public authorities, but demolishing them is often not possible due to high costs as well as critical safety and environmental issues.

Across Europe there is a real and urgent demand for deep renovation to transform vacant, obsolete or sub-optimal public buildings into dwellings. Historic buildings can also be objected to deep renovation with conversion of function while keeping their cultural values. The fastest growing demand comes from the social housing sector due to the ageing population, migrant crisis, and the need for student accommodation. The following statistics shows evidence of over-supply in public buildings and shortage in housing.

Rational decisions on holistic deep renovation of different building typologies should be based on Energy Use Intensity (EUI) that essentially expresses a building’s energy use as a function of its size or other characteristics. In general, a public building has 50-100% higher energy consumption compared to a residential building with an equal floor area. So, deep renovation with transformation of obsolete public buildings into dwellings is the most effective solution to meet the targeted 60% reduction of energy use with the lowest environmental impact and the largest contribution to solving the housing shortage.​