Life Cycle Cost Perspectives on Zero Energy Renovation of a Single Family House

There are 1.2 million single family houses in Norway constituting approximately 50 % of the total dwelling stock. The energy use related to Norwegian single family houses was 30 TWH in 2009. There is a potential of an annual saving of 8 TWh within 2020, if the building envelope of all single family houses built before 1990 are upgraded. When supplementing such an upgrade with installation of energy efficient ventilation and renewable energy production on site, the energy saving potential is even greater.This research investigates if it is possible to renovate a single family house to become a zero energy building and at the same time fulfil requirements related to cost and improved home qualities. This is analysed doing a case study of houses built in the 1980s.Two strategies for zero energy renovation of a single family house built in the 1980s are analysed. The Facade strategy includes upgrade of the thermal properties of the facade including walls, windows and doors, installation of ventilation with heat recovery and renewable energy production on site. The Ambitious strategy includes renovation of the whole building envelope to passive house performance, installation of ventilation with heat recovery and renewable energy production on site. The higher heating requirement for the Facade strategy is compensated with more renewable heat production. The more extensive Ambitious renovation results in higher lifecycle cost than the less extensive upgrade.Norwegians spend huge sums of money on upgrading their homes. Upgrading kitchens and bathrooms are most common for single family houses built in the 1980s, and some of the houses are renovated. However, there is no correlation between the number of defects and the renovation status of the houses. Four categories of houses with common characteristics regarding technical condition and renovation status are identified:a) The ‘as built’ houses have not been maintained, redecorated or renovated.b) The ‘do-it-yourself’ houses have been redecorated and/or renovated by the homeowner and their social network, but may not be in a good technical condition.c) The ‘aesthetic upgrade’ houses have been redecorated and the visual qualities are upgraded, but may not be in a good technical condition.d) The ‘well-kept’ houses are maintained and renovated and are in a good technical condition.For privately owned dwellings, the optimal sustainable renovation strategy can be identified using energy performance, lifecycle cost and home qualities as indicators. The optimal zero energy renovation strategy depends on the homeowner priorities for home improvement. The 'Aesthetic' innovators and the 'Well kept' homeowners are the ones likely to prefer the Ambitious strategy due to its social impacts on factors such as aesthetics and indoor comfort, while owners of 'Do it yourself' houses and the owners of 'Aesthetic' houses wanting to keep the qualities of their house, are most likely to prefer the Facade strategy. The owners of 'As built' houses do not renovate and leave a renovation backlog to future owners of the house.Market success for zero energy renovation of dwellings depends on homeowners' priorities for improved home qualities. However, the homeowners face barriers such as lack of knowledge, lack of services and attractive products and bad advice from craftsmen when they want to carry out energy saving renovation measures. The homeowners that renovate and succeed in energy savings today are either conscious consumers or they have the required knowledge from their profession