Factor 4

for setting out sustainable energy retrofitting policies

Factor 4 Programme of actions towards a factor 4 in existing social housings in Europe

pave factor 4


The Factor 4 project is focussing on social housing retrofitting for improving the energy efficiency and the use of renewable energy in order to participate to the reduction of greenhouse gas emmissions by a factor 4 before 2050. Its objective is to help socal owners to optimise their retrofitting programmes for their whole building stock and to set up strategies towards energy efficiency and the factor 4. The Factor 4 approach is based on the Lyfe Cycle Energy Cost (LCEC) analysis

Objectives – Results

Factor 4, Programme of actions towards Factor 4 in existing social housings in Europe

EUROPEAN COMMISSION– Intelligent Energy – Executive Agency for Competitiveness and Innovation (EACI) – (Grant agreement EIE/05/076/S12.419636)

The Factor 4 project

The Factor 4 project follows the Sustainable Development World Strategy, the Kyoto protocol and the European energy policy which is to reduce by a factor 4 energy consumption in European countries before 2050.

It is focussed on social housing retrofitting for improving energy efficiency and facilitating the use of renewable energy, in order to participate to the reduction of greenhouse gas emission (GEG) by a factor 4 before 2050.

The Factor 4 project aims at:

  • helping social owners to set up sustainable energy retrofitting strategies for their whole building stockworking out innovative solutions and their experiment for energy retrofitting
  • providing technical and economic information for tenants and (small) local professionals on energy efficient techniques
  • the promotion of the initial energy performance diagnosis of buildings
  • the dissemination and larger use of life cycle (energy) cost analysis
  • facilitating the dialogue between social owners and their financial partners.

The Factor 4 project’s objectiveis to help social owners to set up sustainable energy retrofitting strategies for their whole building stock taking into account energy savings and the reduction of greenhouse effect gas (GEG) emissions towards a factor 4 according to the European policy which is to cut by 4 GEG emissions before 2050.

The life cycle energy cost analysis allows to set out these sustainable strategies because it allows to deal together with energy savings, the reduction of GEG emissions and socio economic issues such as the pay back return for social owners and the reduction of charges for tenants.

The Factor 4 approach for setting sustainable strategies for energy retrofitting of social housing building stocks and at territorial scales

The Factor 4 approach allows to reach the factor 4 levell (note 1) and to identify the necessary technical and economic means.
The Factor 4 approach is for various actors:

  • for social owners for setting up strategies for their buildings and their whole building stock
  • for local authorities and public administration for territorial strategies: for identifying the needed level of subsidies for social owners, for setting regulation or rules, for regeneration projects at the neighbourhood or city scale, etc.
  • for banks for defining financial rules
  • For building companies and industrial in order to better know and so to anticipate the future development of technologies, which brings a better local know how and competitiveness.

The Factor 4 approach is focussed on a life cycle energy cost (LCEC) analysis and made of the 3 following phases:

  • Phase 1: a building typology for selecting the representative buildings of the building stock
  • Phase 2: the building scale analysis: analysis of each representative building and optimisation of their energy retrofitting programme with the life cycle energy cost Factor 4 model, id est with 3 optima together: an ecological optimum (reduction of GEG emissions), an environmental optimum (reduction of energy consumption) and an economic optimum (for both the social owner and the tenant).
  • Phase 3: the whole building stock analysis in order to set a sustainable energy retrofitting strategy for the building stock identifying the optimised retrofitting programme for each building andFor more information on the Factor 4 approach, read or download the deliverables or contact us.1 Reaching the factor 4 means to divide CO2 emissions (and so energy consumption) by 4 after retrofitting works.


List of deliverables and newsletters to download

There are deliverables for each step of the Factor 4 approach

The first step on the housing sector and on the building typology

  1. deliverable 3 :the first building typology (English only) 4 files are available: Del3 part1; del3 part2A on France; Del3 part2B also on France and the annex
  2. deliverable 4: estimation of energy consumption and CO2 emissions of each national social housing building stock 3 files are available, one in English and 2 in French (del 4 and Del 4 annex )

The second step with the building analysis:

  1. deliverable 7 optimisation as regarding the CO2 objective (or how to reach the factor 4) (English only with 4 files available: on Denmark, France, Germany and Italy )
  2. deliverable 9 LCEC analysis of best practices (on representative building types) 3 files are available: in French for the French analysis, in Italian,
  3. Newsletter 3 : 4 languages are available: English, French, Italian and Romanian

The third step with the building stock analysis for setting up a sustainable energy retrofitting strategy:

  1. deliverable 10 elements for a national or a territorial energy retrofitting strategy. 2 files are available: in English and in French
  2. Newsletter 4 – 4 languages are available: English, italian, romanian , French,

The Factor 4 model:

  1. deliverable 5 (English only) synthetical description of the various versions of the Factor 4 model, including the previous state of the art on existing tools
  2. deliverables 8 description of each version of the Factor 4 model in national languages, 5 files are available: in French, in German, In Italian and in in Romanian
  3. deliverable 6 data base on the energy efficient technologies dealt with in the Factor 4 model 2 files are available (Introduction and the data sheets themselves) (English only)
  4. Newsletter 2 4 languages are available: English, French, Italian and Romanian

on energy retrofitting and on LCC:
deliverable 11 (English only)

Overall synthesis
: Factor 4 Brochure 4 files are available in English French and in Romanian, Italian version

Partners of Factor 4 Project:

Sustainable Energy Europe, a European campaign to raise awareness and change the landscape of energy” et ” Energie durable pour l’Europe, campagne européenne de sensibilisation pour changer le paysage climatique

Coordinator: SUDEN association

  • Denmark : Cenergia Energy consultants and KAB
  • France: La Calade, Moulins Habitat , Union Sociale pour l’Habitat (USH) and HTC (Habitat et Territoires Conseil)
  • Germany : Volkswohnung
  • Italy : Soc Coop ABITA ARL and  Ricerca & Progetto
  • Romania: Association of promotors for a local development APDL

For more information, download  the Factor 4 newsletter 1 in English , in French, in Italian or in Romanian or the Factor 4 partners file (in English)

final Conference

The Final conference was the 2nd of June 2008 in Paris at MEEDDAT, the French ministry of Ecology, Energy, Sustainable Development and Land Planning. It was supported by PUCA, a public administration in charge of research in Urban, Construction and Architecture.

180 participants were registered and more than 150 participated:

  • social owners
  • of course but also:
  • agents of national and regional public administration in charge of housing or neighbourhood regeneration (and sometimes of environment),
  • national and local environment agencies such as Ademe,
  • territorial and local authorities, and especially agents in charge of housing or neighbourhood regeneration,
  • banks,
  • land planners and architects,
  • universities,
  • technical or energy consultants.

The programme can be download in French and English.

A book gathering the slides has been distributed to the participants and can be download. It contents:

– 6. The SEC model
– 7. The life Cycle Cost analysis for a neighbourhood analysis and a building stock strategy (with the Factor 4 / SEC model), for new housing (without pictures) and the last presentations (on standards…)


The SEC model is regularly improved and is usable since 2009 for single houses and for private ones. The users (social owners, local authorities, local energy agencies, etc.) are gathered in users groups in order to share results and experience on the one hand and to allow a regular updating of the model (price evolution, new technologies, etc.). »
For more information : contact-us

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