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Retrofitting a building

Passivhaus architecture is not just about new buildings; retrofitting our existing buildings is just as important as building new ones to the highest possible standards. In fact extensive deep retrofit of our existing building stock is essential if we are to have any hope of addressing some of our most pressing problems, notably climate change and the ongoing energy crisis.

Refurbishment vs retrofit


Refurbishment is a familiar term to most people. The main driver for refurbishment is addressing building defects (such as dampness) while making cosmetic improvements such as installing a new bathroom or kitchen. While it can involve some energy efficiency improvements (in fact it is the ideal opportunity to add insulation to reduce future heating bills) energy efficiency improvements are not usually the principal objective of a refurbishment project.  


Retrofit involves all of these things but is principally concerned with adding materials (such as insulation) and components (such as high performance replacement windows) that were not part of the original building in order to improve energy performance. In order to carry out an effective retrofit project which achieves significant improvements, a “deep retrofit” of the whole building is usually necessary. This will involve taking down ceilings, removing floor boards and stripping wall linings. It is not generally possible to carry this out while living in the house. If a building needs improvements such rewiring or a new kitchen anyway, this is the ideal time to consider deep retrofit. A house extension can easily be combined with a retrofit of the existing building, especially if the extension results in the completed house having a more energy efficient form. 

One very common example of a deep retrofit project is the conversion of redundant agricultural buildings such as barns, steadings and stables. Transforming such buildings, which were never intended to be heated, inevitably involves adding insulation, fitting windows and doors and installing a heating system.

A successful deep retrofit will involve applying many of the same principles as a Passivhaus new build project. 

  • Often the building will already have a energy efficient form – many old buildings (think terraced houses) were built in this way because simply because it was cheaper. 
  • Improving insulation of the floor, walls and roof
  • Ensuring that there are no gaps in the insulation, while accepting that this can sometimes be challenging in an existing building
  • Improving airtightness to eliminate draughts and vastly improve comfort as well as reducing energy bills – addressing draughts can often be one of the easiest and most cost effective ways of improving energy efficiency
  • Installing high performance windows and doors
  • Providing a good ventilation system, which may include heat recovery, to ensure an excellent level of air quality in what will be a much more airtight building

Another very important consideration in retrofit architecture projects is the control of moisture. All too often, attempts at improving the energy efficiency of buildings can inadvertently cause moisture to be trapped inside the building structure leading to future problems. Selecting the right insulation strategy for your building is essential and this is where an architect with the right knowledge can really help. 

Graeme has completed the AECB Retrofit Foundation course in order to apply his knowledge of Passivhaus principles to the improvement of existing buildings.

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