ERIKA MATA

Dr. Erika Mata is a researcher in the Unit for Climate & Sustainable Cities at the IVL Swedish Environmental Research Institute in Gothenburg. She has worked internationally as architect, energy consultant and researcher, on the transformation of the building sector to meet environmental, economic and social targets, with a focus on climate impact. She has been project leader, WP leader and researcher in numerous national and international research projects with various geographical boundaries, aggregation levels and topics (models and data, building retrofitting, demand and supply side, effects of future climate change, policy). She is currently Lead Author for Chapter 9 Buildings of the Working Group III contribution to the 6th Assessment Report of the Intergovernmental Panel on Climate Change

Carbon neutrality in the building sector requires minimum and flexible demands on energy and materials, as well as the integration of renewable energy sources. Whereas in individual buildings, minimum demand is achieved with active and passive efficiency measures in combination with comfort flexibility and increased tolerance to automated management, approaches at district level allow for additional synergies key to carbon neutrality.

'With the proper upscaling mechanisms, districts can be catalysts of innovative solutions'

The Swedish building sector and energy system are quite particular. Existing buildings perform relatively well and the energy system relies largely on low-carbon energy generation – the predominance of district heating and clean electricity. The Swedish government aims for carbon neutrality by 2045, and roadmaps are being designed to achieve this target. The total energy use in buildings should decrease by 20 % by 2020 and 50 % by 2050, from a 1995 baseline^[1] . As substantial growth is expected around the biggest urban areas, with 705 000 dwellings to be built by 2025^[2] , these goals are even more challenging. In this context, the examples below are key to establishing a market for solutions for very low carbon buildings and thus, meeting environmental, social and economic targets.

Comprehensive urban regeneration

CITIFyED project^[3] has renovated an area of 379 rental apartments in Lund. Beyond improving energy efficiency, measures were taken to prevent a large rent increase: a broader urban retrofit of the area with densification projects, retrofitting and modernisation, including new passive houses, and a renewed town square. Communication activities from the early stages increased social acceptance.

Local heat recovery

An energy system of a community of mixed uses can provide positive demand-supply synergies. For instance, 1.2 EJ/year^[4] are potentially available for recovery from urban heat sources in the EU. This corresponds to more than 10 % of the EU’s total energy demand for heat and hot water. ReUseHeat Project demonstrates the techno-economic viability of urban heat recovery, e.g from data centres, metro ventilation or cooling systems. A technoeconomic assessment^[5] shows that the availability of urban excess heat exceeds what is cost-efficient to use. Issues regarding contracts, business models and barriers to investment have been identified in interviews with stakeholders^[6].

'Projects at district level present an outstanding opportunity to develop and test the solutions for very low carbon buildings that are required to achieve the ambitious environmental targets'

 

Heat supply to new low-energy building areas

Three options exist for heat supply in new construction: ‘individual’, ‘on-site’ and ‘large heat network’. A study drawing on real data in Sweden^[7] shows that the individual and on-site options increase biomass and electricity use, which in turn increases carbon emissions in a broader systems perspective. The impact of the large heat network option depends on the scale and supply-technologies of the district heating system. A cost assessment^[8] shows that in most cases, the large heat network has the lowest system cost.

Sharing facilities

Many premises lend themselves to sharing, such as canteens, receptions and storage facilities. An estimation^[9] of the potential for sharing office spaces shows that energy demand for heating could be reduced by 35-75 %, and electricity use by 41-57 %, resulting in correspondingly substantial CO₂ emission reductions. Additionally, the reduction in floor area implies a substantial reduction in the energy need and associated emissions from the construction of new office buildings. In a residential community, sharing can be extended to laundry spaces, hobby rooms, libraries and rental rooms for family guests, allowing for smaller apartments.

Networks for reusing construction products

The construction industry in Sweden creates a waste stream of about 10 million t/year. There is national potential to reduce waste volumes by 18 000 t/year, greenhouse gas emissions by 21 000 tCO₂ e, and purchasing costs by around EUR 60 million/year by reusing existing interior construction products in conjunction with office renovations. A recent study^[10] shows that local networks are central to mapping, storing and relocating used construction material. Incentives should be aligned with the EU waste hierarchy. The property owner is seen as a key stakeholder, with the opportunity to create and spread incentives for reuse.

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