Interviewee: Camille Sifferlen
Energy Review, Vol 4. Issue 9. 2022
Energy Review: Given that the construction sector contributes a substantial share of the global emissions, can you elaborate on the importance of passive houses and sustainable buildings in achieving net-zero and climate mitigation goals?
Ms. Camille Sifferlen: The Passive House Standard is an international standard for high-performance buildings. It is mostly known for drastically reducing energy demand. Thanks to a high-quality building envelope and efficient technical services, the energy demand of these buildings can be up to 80% less, for cooling than existing buildings (or 90% less for heating), depending on the climate. At the same time, these buildings provide better living and working conditions to their occupants (good indoor air quality, comfortable temperatures all year round,
no drafts or mould). They, further, are future-proof, because they won’t need a deep energy retrofit in the next decade, making people afford their low operation costs. Such buildings, thus, provide more independence from fluctuating energy prices and resilience to warming climate conditions.
Highly energy-efficient buildings are crucial to achieving net-zero and climate mitigation goals. The energy demand is so low that it can easily be covered with renewable energy sources. This helps not only to reduce CO2 emissions but to reduce the stress on the energy grid, as peak cooling and heating loads are also significantly smaller than those of existing buildings. As an approach to Net-Zero, making the building more efficient first and then adding the renewables is known to be the most cost-efficient strategy. Due to the increase in urbanization, more and more high-rise buildings are being constructed in India now. This also brings the question of the available area for the installation of renewables. Moreover, to make renewable energy reliable, energy storage is generally required along with it. As the total building energy demand increases, the size of required energy storage increases and so do the building lifecycle costs.
You will find several Passive House examples which generate a certain amount of renewable energy on the Passive House database, where a high variety of projects with different shapes, scales, materials, functions and locations is highlighted.
ER: Although passive houses promise energy efficiency, the high costs of the construction challenge the SDG goal of ‘Affordable and Clean Energy’. In that context, what are your views and recommendations for cost-efficient construction materials to be used in sustainable buildings?
Ms. Sifferlen: The SDG goal of ‘Affordable and Clean Energy’ will only be possible with a very reduced energy demand. Building to a high-performance standard generally requires additional investment costs which can be covered by the savings in operational energy, over the life cycle of the building. Having the required high-performance products manufactured in India and trained professionals available locally will also help to reduce the additional investment cost in the future and improve the post-sales services. This can be seen in Europe, where the number of social housing projects built to the Passive House standard is increasing, e.g. in Spain or the United Kingdom.
Besides, high-performance buildings can also be greatly supported by adequate policies and incentives, such as better loan rates, permit fast-tracks and extra density allowance. Investment costs are also lower if the Passive House principles are taken into account from the very beginning of the project. This includes ensuring a good building orientation and compactness, as well as reducing window sizes in hot climates whilst still ensuring enough daylight, in order to prevent additional solar loads. The floor plan also has an influence on energy efficiency. By grouping and stacking rooms of similar uses, the length and complexity of pipes and ventilation ductwork can be simplified. The impact of such design decisions was assessed during the study on “Replicable designs for energy-efficient residential buildings”, supported by GIZ India and done in collaboration with the local partners from Ashok B Lall architects, Lead Consultancy and KPMG. Its results are now available on the Econiwas platform. The study shows that buildings that are less compact or with less favourable orientation would need more insulation and better glazing to reach the Passive House standard.
ER: Technological innovation has undoubtedly enabled the rapid growth of green and energy- efficient buildings. As a passive house consultant and designer, can you explain some of the advanced technologies that are being used to construct energy-efficient buildings?
Ms. Sifferlen: The Passive House Institute is working together with manufacturers worldwide to help them increase the efficiency of their products and make the required information available on the Passive House component database. Some of the advanced technologies which will be needed to construct Passive House buildings in the cooling-dominated climate zones of India include:
1. Ventilation units with improved heat and humidity recovery, significantly reduce the heat and humidity loads through the air, not compromising on air quality. If you ventilate houses with windows in Bhubaneswar, for example, 100% of the exterior heat and humidity will enter your building and your air conditioner will have to work harder to get rid of this unwanted heat. Whereas, if you use a ventilation unit with heat and humidity recovery, the hot incoming air is precooled by the colder extract air, and most humidity is kept outside of the building thanks to the humidity recovery. In addition, the air is continuously filtered.
2. In hot climates, the glazing should prevent solar heat transmission as much as possible, but at the same time also make maximum use of daylight. Such requirements can be achieved through spectrally selective glazing. This type of glazing allows the visible fraction of the solar spectrum to enter a building while blocking the others.
3. High-performance buildings require smaller air conditioning units that can handle their low cooling load and efficiently address both cooling and dehumidification needs (in hot and humid climates). One single split unit per dwelling unit may be enough, preferably with a climate-friendly refrigerant such as propane.
There are also continuous innovations in the airtightness sector, to further increase the ease of application. Besides, as more attention is being paid to embodied energy, prefabricated construction systems with sustainable materials like strawbales, wood fibre or cellulose are becoming more popular.
(Ms. Camille Sifferlen is a Certified Passive House Designer, Passive House Institute representative, and Board member of La Maison Passive France.) ■□■