Passive houses are often regarded as one of the main answers to dealing with environmental sustainability in the built environment. This is especially the case when it comes to governmental policies in Europe.

But are passive houses really sustainable? And are they always the right answer to the climate challenge?

 

The fact, that the passive house standard purely focuses on the energy demand for peration, and in some cases, the embodied energy of the materials used in the building, does withdraw from the status of passive houses being sustainable by default (see table 1).

Sustainable buildings need not address all the themes listed in table 1, but the more themes a project considers the more holistic the approach to sustainability is.

The fact that the passive house standard does not consider whether the house is located in an area with Combined Heat and Power (CHP) with a low Carbon emission footprint (e.g. straw), is a major weakness one has to be aware of when choosing to do a passive house.

A study carried out at the University College in Dublin [3] shows that seen in a 50 year life cycle perspective, the embodied energy of the materials used for the last kWh/m  reduction needed to achieve the passive house standard, actually increased the energy consumption for the building to such an extend, that the energy reduction achieved for operation was balanced out by the increase in embodied energy.In other words – the last kWh/ m2 needed to achieve the passive house standard, actually increased the energy consumption for the building to such an extend, that the energy reduction achieved for operation was balanced out by the increase in embodied energy.

In other words – the last kWh/m2 energy savings for operation do not necessarily lead to an overall lower impact on the environment. Actually it might increase the increase the impact considering the fact that the energy consumption for operation might be changed to a fuel with lower Carbon emission than today or if the fuel for the CHP plant already has a low carbon footprint.

Based on this, the proper answer to the question posed in this blog would be that: passive houses can be a sustainable choice if the project considers the production of the house, as well as, other issues of sustainability (e.g. water consumption, waste handling, site selection and impact, procurement of materials, goods and services, and user and community interaction etc).

Basically, a passive house design should always be assessed as a possibility of reducing the energy demand for building operation in relation to the specific context that the building is located in, as well as, the other issues of sustainability. Thereby, establishing whether a passive house is the most economically, socially, environmentally and climatically sustainable solution for that specific project.

References:1.  www.passiv.de  2.   Hansen (2007): SENSITIVITY ANALYSIS as a Methodical Approach to the Development of Design Strategies for environmentally sustainable buildings. PhD thesis,