In our blog, we are dedicating a large number of articles to deep energy retrofits, on one hand, and Passive Houses on the other. However, these two topics are not necessarily distinct from one another: here, we explain why.
When discussing “renovations” or “retrofits”, clearly we’re looking at the modification of an existing structure. The semantics (renovation, retrofit, refurbishment, etc) simply distinguish the level of involvement and general scope of works.
The term “Passive House”, instead, represents a project goal as far as health and comfort, and energy efficiency, whether it is a new construction or a renovation. For a comprehensive definition of what a Passive House is, you can read our article about it.
Is it possible to achieve passive standard in case of a building renovation or retrofit?
Is it always convenient (or cost efficient) to do so?
Not always. Here’s why:
In order to work, a passive building needs to be able to receive passive heating from the sun, as well as to make good use of the heat produced by the people living in it and by the appliances (lighting, home appliances, computers etc.). For the building to rely only on these heat sources, its thermal envelope needs to be compact, well insulated, without thermal bridges or air leakages; and its openings need to be mostly oriented towards the equator.
When a new construction is designed from scratch, it is possible to integrate all these concept from the preliminary stages. This way, the energy efficiency of the building can be maximized, while keeping construction costs low. Compact form and orientation towards the sun determine what the heating/cooling demand of the building is going to be: these factors are a lot more important than any HVAC system or insulation material. For this reason, the design of a Passive House, and more generally of a sustainable building, requires an integrated design approach, where different aspects of the design are developed together, including the thermal envelope, the load bearing and seismic-proof structures, building services, acoustics and so on.
When you are working on an existing building, many of these factors are already given. It is often impossible to modify the shape or the orientation of a building. Consequently, the thermal envelope is going to receive less free heating from the sun, and the heat losses are likely to be higher. This does not mean that it is impossible to achieve the passive goal in case of a building renovation/retrofit: it means that it is not always convenient to pursuit this goal at all costs.
Buildings – like people – are all different from one another. It is impossible to find a one-size-fits-all solution to be applied in any circumstance. Location, orientation, compactness, construction material need to be taken into account. Furthermore: in case of a complete building renovation, where the works also involve the load bearing structures and the inner partitions, the overall evaluation has to be extended to factors that go beyond comfort and energy savings. What are the conditions of the bearing structure? Is the building even worth keeping? Is it necessary/possible to improve the seismic resistance of the structure? What about universal access? Are there barriers? Is it possible to remove them? Is it necessary/possible to improve the acoustic performance of the building?
For the decades to come, building retrofit represents probably the most important development for the construction industry in Italy. The topic is vast and complex. The potential is also very high: improvement of quality of life, economic development and energy savings. These kinds of projects, however, require higher technical skills from designers, in order to avoid gross design mistakes, that often turn out in disasters. Current Italian technical norms fall behind, and cannot guarantee proper building quality as far as health and comfort.
The passive standard is likely to become the future of the European construction industry – for new construction – starting from 2020, even though the 2010/31/EU Directive about Near Zero Energy Buildings still contains some grey areas. In one of our articles, we explained the great difference between the two concepts.
As far as renovations/retrofits are concerned, the passive standard needs to represent a goal, even though project-specific conditions are going to determine to what degree it can be applied. In these cases, in fact, it is more important to have a clear overall picture and aim to improve the building as a whole, including the bearing structure, the thermal bridges and so on. Energy efficiency can then be a secondary area of focus.