[Interview] Jessica Grove-Smith, Joint Managing Director & Senior Scientist at Passive House Institute

  • by Build Up
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  • 2022-04-20 10:51:34
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  • International
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Photo : Timber construction settlement in the Prinz-Eugen-Park, Munich, certifeid Passive House district © Architekturwerkstatt Vallentin

Jessica Grove-Smith is senior scientist and joint managing director of the Passive House Institute in Darmstadt. Her areas of expertise include energy efficient building solutions to the Passive House Standard around the world, interrelations between efficiency and renewable energies (the PER concept) and deep energy efficiency for public indoor swimming pools. Jessica frequently participates in conferences internationally on technical and policy related topics with regard to high performance buildings.

1. Before discussing about future scenarios and renewable energy sources in Passive House (PH) constructions, can you share some figures on where the development of PH standard is today:

What is the current uptake of the PH standard and certification outside Europe? /in other climate regions, different from the central and northern Europe ones where this standard originated?

Passive House is rapidly increasing in popularity in many parts of the world. At the start of this year, we recorded over 29,000 units certified to the international Passive House criteria, which equates to more than 2,7 Mio m² living area the world over. Of course, this only includes the certified projects, as we don’t have figures of the number of non-certified projects built based on the Passive House concept. Though we encourage building owners to certify their Passive House buildings as a quality assurance measure.

To help log projects, we have the online Passive House Project Database, which is constantly growing and provides useful insight into the diversity of projects worldwide, from innovative single-family houses combining Passive House with low carbon materials, to various more complex non-residential buildings typologies, as new-builds and retrofits. It can also be a great place to look if you are looking for Passive House projects and professionals in your area.

The standard has definitely picked up outside of Europe. There is substantial uptake, for example, in North America, with Vancouver being a prime example of incentivising Passive House through local policy. The next few years are going to be very exciting, as we expect completion of a number of local large scale schemes that could be game-changing for the perception and awareness level of the standard. On the other side of the globe we are seeing continued growth in China – not only in terms of built projects but also in terms of high-performance components, which is absolutely crucial in achieving market transformation. Passive House components can be browsed and filtered by type and country in our component database. Last year also marked the completion of the first regional larger scale non-residential project on the Australian continent.

Also very encouraging to see are Passive House “firsts” in new regions, for example a retrofitted factory in Sri Lanka, new builds in the UAE and in Saudi Arabia, as well as in Brazil. We are also involved in initiatives in India and, as research institute, are taking part in important discussions surrounding the projected rising cooling demand in emerging economies. So, as you see, Passive House is truly expanding across the globe.


2. In 2015, along with the release of the 9th version of the Passive House Planning Package (PHPP 9), the Primary Energy Renewables (PER) method was introduced as well as the Plus and Premium certification categories on top of the Classic one.

May you summarise the rationale for developing this PER approach?

The reason for developing the PER approach is the ongoing transition to an energy supply based primarily on renewable energy. The currently prevalent evaluation systems to measure the overall impact of buildings are non-renewable primary energy (PE), or CO2 as indicator for GHG emissions. These methodologies were developed for the traditional fossil-fuel heavy energy supply structure and they simply don’t do justice to the changing infrastructure with increased renewable energy supply (RES) because they fail to measure and incentivise efficient use of renewable energy resources. Renewable energy generation, transmission and storage requires infrastructure, investments and requires space, which eventually becomes a decisive limiting factor. A sustainable energy supply based on RES can only be achieved if we use these resources wisely and efficiently. 

Driven by the urgency of meeting global climate goals, we at PHI developed a new scheme to better reflect synergies between energy efficiency and the use of renewable energy resources. In a nutshell, the PER (Primary Energy Renewable) methodology provides an assessment of a building’s compatibility with renewable energy supply. For example, using a heat pump water heater to produce hot water will result in a lower PER demand than using a gas tank water heater.

In more detail: Renewable primary energy (PER) is the unit of energy generated from renewable resources, e.g. electricity produced by a photovoltaic system/wind turbine. PER-factors reflect the primary renewable resources needed to cover the final energy demand of a building, specifically including distribution and storage losses. The higher the PER-factor, the higher the required renewable energy resources. These PER-factors have been derived based on a future scenario of a 100% renewable energy supply. They take into account site-specific hourly load profiles of the energy demand for different end uses compared to the hourly available renewable energy supply. The heating demand for domestic hot water and for household electricity feature fairly constant demand profiles over the course of the year, and the demand can be covered to a large extent directly from the renewable primary energy source, without the need for storage or via efficient short-term storage technologies. The energy demand for heating, on the contrary, only occurs during winter with lower renewable energy resources. A relevant part of the energy demand must, therefore, undergo seasonal storage, which implies high losses and a higher PER weighting factor. The higher factor provides a direct design incentive to prioritise efficiency measures for reducing the heating demand over measures for reducing cooling demand, which is much more compatible with renewable energy resources.

In addition to differentiating for various end uses of electricity, the PER scheme also considers other fuels in the context of a sustainable renewable energy supply. For example, gas for heating furnaces is considered as power-to-gas, with the respective conversion losses. Efficient use of the highly valuable resource biomass is taken into account via a limited biomass budget.

The aims of the PER methodology are to incentivise electrification (preferably with a heat pump), to limit the use of biomass and to prioritise efficiency measures for those end uses that are least compatible with the regional renewable energy supply. I encourage to dig deeper into the topic by following the links provided at the end.

The additional categories Plus and Premium, on top of Passive House Classic, were introduced at the same time as the PER methodology in order to encourage designers and clients to go the extra mile by adding renewables to their Passive House building. If we want to meet climate goals, we ultimately need both – efficiency plus more renewable energy supply.

This PER indicator of energy consumption is now recommended for Passive House certification over the non-renewable Primary Energy one, which was used before and is still the common reference in standard EPB calculations.

Can you still choose, when certifying a project, to go with conventional PE calculation?

Yes, Passive House certification is possible either through the PER or the PE scheme for the “Classic” category. As soon as renewable energy production is accounted for as part of the project (Passive House Plus or Premium) the PER scheme has to be used.

Do the PHPP calculations still provide both the PER and PE figures in order to maintain a level of comparability?

Yes, most certainly, and that will not change. PHPP provides the calculated energy demand as final energy, as PE, as PER and also as GHG (CO2) emissions. They cannot be directly compared because they have different purposes, but they all have their validity. As described above, PER provides a future-oriented assessment in the context of a sustainable renewable energy supply. PE and CO2 are indicators of the building’s environmental impact in today’s energy supply structure.

Personally, I’d like to encourage all designers to use PER to guide major design decisions, as this will facilitate and the energy transition towards RES and provide long-term sustainable solutions. The structure of energy supply will change substantially during the lifetime of a building that is constructed today, and this needs to be taken into consideration. CO(or PE) should be used as a secondary indicator to cross-check the current environmental impact of their choices.


This article was posted on Build Up

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 energy efficiency
 ecological transition

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