Niko Heeren

Environmental Impact of Buildings—What Matters?

The goal of this study was to identify drivers of environmental impact and quantify their influence on the environmental performance of wooden and massive residential and office buildings. We performed a life cycle assessment and used thermal simulation to quantify operational energy demand and to account for differences in thermal inertia of building mass. Twenty-eight input parameters, affecting operation, design, material, and exogenic building properties were sampled in a Monte Carlo analysis. To determine sensitivity, we calculated the correlation between each parameter and the resulting life cycle inventory and impact assessment scores. Parameters affecting operational energy demand and energy conversion are the most influential for the buildings total environmental performance. For climate change, electricity mix, ventilation rate, heating system, and construction material rank the highest. Thermal inertia results in an average 2-6% difference in heat demand. Nonrenewable cumulative energy demand of wooden buildings is 18% lower, compared to a massive variant. Total cumulative energy demand is comparable. The median climate change impact is 25% lower, including end-of-life material credits and 22% lower, when credits are excluded. The findings are valid for small offices and residential buildings in Switzerland and regions with similar building culture, construction material production, and climate.

Housing and Mobility Demands of Individual Households and their Life Cycle Assessment

Household consumption, apart from governmental consumption, is the main driver of worldwide economy. Attached to each household purchase are economic activities along the preceding supply chain, with the associated resource use and emissions. A method to capture and assess all these resource uses and emissions is life cycle assessment. We developed a model for the life cycle assessment of housing and land-based mobility (excluding air travel) consumption of individual households a small village in Switzerland. Statistical census and dwelling register data are the foundations of the model. In a case study performed on a midsized community, we found a median value of greenhouse gas emissions of 3.12 t CO2 equiv and a mean value of 4.30 t CO2 equiv per capita and year for housing and mobility. Twenty-one percent of the households in the investigated region were responsible for 50% of the total greenhouse gas emissions, meaning that if their emissions could be halved the total emissions of the community would be reduced by 25%. Furthermore, a cluster analysis revealed that driving factors for large environmental footprints are demands of large living area heated by fossil energy carriers, as well as large demands of motorized private transportation.

Towards a 2000 Watt society – assessing building-specific saving potentials of the Swiss residential building stock

Switzerland declared the notion of the 2000 Watt society as their leitmotif towards a sustainable development in terms of energy. This implies that worldwide, no more than 17520 kWh of total primary energy and 1 ton CO2-eq. are to be consumed per capita and year for all services. Thus, in order to meet the targets of the 2000-Watt society, it is necessary to reduce primary energy demand by 44% and greenhouse gas emissions by 77%. The building stock model, described in this paper, assisted the government of Zurich to identify the necessary steps in order to achieve the goals with regard to the city‟s residential, school, and office buildings. The objective of this paper is to investigate the role of energy demand reduction in residential buildings on the way towards the goals of a 2000-Watt society. In order to illustrate the mechanisms within the building stock and to identify the effects of construction activity, the model works with different scenarios. Specific measures were isolated and analysed individually. All three measures act directly on the building stock; each have comparable reduction potential in terms of primary energy demand (ca. 15%) and greenhouse gas emissions (ca. 40%). In order to further cut back greenhouse gas emissions, measures to reduce carbon intensity of fuels and electricity need to be considered.

Comparative emission analysis of low-energy and zero-emission buildings

ABSTRACT Different designs and concepts of low-energy and zero-emission buildings (ZEBs) are being introduced into the Norwegian market. This study analyses and compares the life cycle emissions of CO2 equivalents (CO2e) from eight different single-family houses in the Oslo climate. Included are four ZEBs: one active house, two passive houses, and a reference house (Norwegian building code of 2010). Monthly differences in CO2e emissions are calculated for the seasonally sensitive Norwegian context for electricity generation and consumption. This is used to supplant the previous applied symmetric weighting approach for CO2e/kWh factors for import and export of electricity for the ZEB cases. All the ZEBs have lower use-stage emissions compared with the other buildings or the reference case. Embodied impacts are found to be 60–75% for the analysed ZEB cases, confirming the importance of embodied impacts in Norwegian ZEBs. The lowest total emissions were from the smallest ZEB, emphasizing area efficiency. The highest emissions were from the reference case. By abandoning the symmetric approach, a new perspective was developed for assessing the performance of ZEBs within the Norwegian context. One of four ZEB cases managed to balance out its annual energy-related emissions.