Low tech as a way to mitigate the hidden environmental impact of buildings
The carbon spike
The environmental impact of buildings is separated in two categories: operational environmental impact and embodied environmental impact. Operational environmental impact is the impact which is generated by a building during its entire usage phase. These are mainly the result of the energy used for conditioning the interior climate of the building. Reducing the operational impact was until recently the main concern of the design practice. By now, architects know how to create energetically performant buildings which can claim a low operational environmental impact. So, our focus has shifted to the construction process and the environmental impact that is related to the production, assembly, and maintenance of buildings. This impact is called the embodied environmental impact. With our attempts to reduce operational environmental impact, the embodied environmental impact has increased, due to a higher amount of materials that are used in contemporary, energetically performant buildings.
In current practice we see that in most buildings, the embodied environmental impact tends to become higher than the operational impact. This is not the only reason why the embodied environmental impact needs our attention. The embodied environmental impact is also the initial environmental impact, which happens before or at the very beginning of construction, so before the actual usage of the building, and in a short period, forming a considerable ‘carbon spike’ (1).
Mitigating this initial carbon spike is an important element in the overall strategy to lower the environmental footprint of our buildings, as it happens upfront (‘now’) and it is sure that it will happen. Choices influencing this spike should be well considered, and if decisions are made that increase the embodied environmental impact, they should be offset by lower operational environmental impacts. The time to offset higher initial impacts, which can be seen as ‘environmental investments’, will vary case by case, by the function and use of a building and by various future energy mix scenarios. There is still quite some uncertainty about this ‘environmental payback period’. Current climate observations have made clear that actions to cut environmental impact in general, and carbon emissions in particular, should start ‘now’ to meet the IPCC 1,5°C pathway. However, generating now a carbon spike with the intention to, hopefully, reduce emissions on the long term, maybe only become breakeven in 20 years, and that is a situation to avoid. So, optimizing both the operational and the embodied environmental impact of our buildings should be of our first concern.
The embodied environmental impact of technical installations
For some years, the embodied environmental impact of common building products is an important decision driver in architectural design practice, with the Life Cycle Analysis tool TOTEM as main guidance in the Belgian context. Hence, the strategy to reduce the amount of new materials through smart combining of building programming and the reuse of existing buildings, building structures and building materials.
Up to now, the embodied environmental impact of technical installations in buildings is overlooked. This is mainly due to the complexity of these installations and the lack of data on the quantities of materials which are used in technical installations. Recent studies have given us more insights and show that between 14% up to 45% of the embodied environmental impact of office buildings is due to the technical installations (2), depending on the type of installation and the considered lifespan. This comes not as a surprise, as technical installations consist often out of (rare) metals and contain liquids with a high GWP (Global Warming Potential). The hot spots are situated in the HVAC distribution and emission systems, the electric wiring (copper), the cooling refrigerants, and the PV panels.
Low Tech as a strategy
Mitigating the embodied environmental impact of technical installations can be done by using different strategies, which in most cases should be combined. The main strategy is to reduce the amount of materials used in the technical installation and to avoid the use of cooling refrigerants with a high GWP.
It’s interesting to notice that different parts of a technical installation have different lifespans, for instance production units have a short lifespan and distribution systems have a long lifespan. Different parts of an installation also have different impacts on the operational energy use and hence the operational environmental impact. The materialization of distribution systems and production units should therefore be considered differently. Distribution systems should be conceived in a way that they are either future proof, or minimized, so that their material impact is minimal. Future proof also means that on a middle-long term different production units, with different energy sources, can be plugged in the installation. On a (rather) short term, we should consider the best equilibrium between material impact and primary energy use, with the related short term environmental footprint (3).
One of the key strategies to reduce the amount and impact of technical installations lays in the architectural conception of the building. The application of climate responsive design strategies, in which the architectural conception of the building mitigates already the bulk of the disturbing influences of the outside climate (heat and cold), offers strategies for low tech maintenance of a comfortable and healthy indoor climate, though, for instance, qualitative daylight harvesting, thermal mass and natural ventilation. By applying these strategies, the net energy demand of the building for maintaining its indoor climate can be considerable lowered. Research has shown that these strategies not only provide to be useful in our current climate, but are even more important in future climate conditions (2 and 4).
Office archipelago, Leuven
Through the combination of thoughtful orientation of the glazing in the facade, exposed thermal mass in the facade, and an elaborated natural ventilation concept, the energy demands of this building are very low. In this way, the amount of technical installations and ducting can be significantly reduced. The amount of installations has further been reduced through careful dimensioning in which not the default values from the normative documents are used, but realistic estimation are used, taking in account the milder inner city climate. In current climate conditions, this new office building reaches acceptable summer comfort without mechanical cooling. In collaboration with KU Leuven, the building is also assessed under future climate conditions. Also under these conditions the ventilative cooling concept provides good summer comfort most of the time. In extreme weather conditions, the reversible heat pump can provide top cooling through the climate ceiling. All technical installations are visible and easily reachable for maintenance and upgrades, knowing that good maintenance is actually the first step in prolonging the life of technical installations.
Alchimiste Local Entrepreneurship Hub, Anderlecht
In the reconversion of this 100-year-old industrial building the energetic upgrade of the building skin allowed us to downsize the heating installations and switch to lower heating regimes. Moreover, decentralized demand-controlled ventilation units with heat recuperation avoid the need for complex HVAC ducts running through the building.
Greenpeace Belgium, Brussels
The technical installations in the new Greenpeace offices, a reconversion of an old organ manufacture, are considerably minimized through the introduction of a hybrid ventilation system in which demand-controlled natural ventilation through operable windows is combined with demand-controlled mechanical extraction with heat recovery by a heat pump. Ventilation ducting is by default reduced by only applying demand-controlled mechanical extraction systems. With an intelligent ventilation concept, also the length of the mechanical extraction ducts could be minimized. In such a hybrid ventilation concept, the primary energy demand is equal to a full double flux ventilation system with heat recovery, but the material impact is significantly reduced. Through the smart validation of the thermal mass, well-conceived solar shading and the application of natural ventilative cooling, the indoor summer climate can be optimized without any need for mechanical cooling. The amount of technical installations has been further reduced through careful dimensioning and using common sense for the indoor comfort targets.
Restaurant Pachthof, Botanical Garden, Meise
The combination of careful architectural design which mitigates high solar loads during summer and optimizes solar gains during winter, in combination with a natural ventilative cooling concept through automatized operable windows, reduces the energy demand and guarantees qualitative summer comfort without the need for mechanical cooling. The thoughtful spatial layout of the mechanical ventilation allows for a flexible use of the building, adapted to either the more crowded summer season or the calmer winter season.
(1) Martin Röck, et al. (2020). Embodied GHG emissions of buildings – The hidden challenge for effective climate change mitigation, in: Applied Energy (https://www.researchgate.net/publication/337591460_Embodied_GHG_emissions_of_buildings_-The_hidden_challenge_for_effective_climate_change_mitigation)
(2) Delphine Ramon, (2021). Towards future-proof buildings in Belgium – Climate and life cycle modelling for low-impact climate robust office buildings, Phd Thesis, KU Leuven (https://lirias.kuleuven.be/3630791?limo=0)
(3) Joost Declercq, (2020). Circulaire economie toegepast op technische installaties – Technische installaties, aanpasbaarheid en reversibiliteit, Seminarie Duurzame Gebouwen, Leefmilieu Brussel (https://leefmilieu.brussels/sites/default/files/user_files/sem05-201016-6-jd-nl.pdf and https://leefmilieu.brussels/sites/default/files/user_files/sem05-201016-6-jd-fr.pdf )
(4) Joost Declercq, et al. (2021). The feasibility of natural ventilative cooling in an office building in a Flemish urban context and the impact of climate change, Proceedings of the 17th IBPSA Conference (https://www.conftool.pro/bs2021/index.php/30811_Declercq_Joost.pdf?page=downloadPaper&filename=30811_Declercq_Joost.pdf&form_id=30811)
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