PhD theses

PhD theses supervised in whole, or in part, by faculty members of the research group. Click on blue hyperlink for full-text, or elsewhere in the grey box to view summary.

Mehrdad RABANI (2021) “Retrofitting of Norwegian Office Buildings towards Nearly Zero Energy-Technical, Environmental, and Economic Aspects” [PhD thesis]. Norwegian University of Science and Technology (NTNU). ISBN 978-82-326-5202-0

Summary: Some take-home messages from Mahrdad Rabani’s PhD-thesis: • He describes a methodology (Graphical Scripting linking GenOpt & IDA-ICE) for nZEB deep-retrofit. • Optimal retrofit packages (LCC & comfort/daylight) including controls, were developed for case studies of typical office buildings from years 1987 & 2010, in cold climate*. • High-quality windows (approx 0.6-0.8 W/m2K*) and external walls (approx 0.10-0.12 W/m2K*) should always be part of the retrofit package. • Roof & ground floor retrofitting are costliest; use only when priority is energy, not investment. • Retrofit DCV all-air heating/cooling with 85% heat-recovery (rotor) replaces the need for distributed hydronic heating (existing radiators). • Optimum external shading (Bronze screen), combined with window airing, both controlled by external facade-mounted irradiance sensor (>70 W/m2*) & room temp. (>22°C*). • If there’s opportunity to adjust window/floor area-ratio, then approx 15-17%* is a multicriterion optimum (LCC & thermal/daylight/glare comfort). • Roof-mounted polycrystaline PV (45%* of floor area, 14% efficient, 35° tilt*) has lower LCA than monocrystaline (18% eff.). [We need more efficient mass-produced BIPV!]. • These retrofit installations reduce the GHG footprint of the 1987 office building (The increace in embodied GHG due to retrofit, is offset by a larger reduction in operational GHG emissions). • The above optima are on condition of keeping original electric boiler (EU28 mix). Retrofitting district heating (CHP plant) gives lowest GHG, or GSHP is 2nd best. Further study needed on this. * interdependent, and depends on climate (Oslo values shown here).
Supervisor(s): Prof. Natasa NORD from NTNU, and Habtamu B. MADESSA from OsloMet.
Acknowledgements: GK AS.

Alex GONZÁLEZ CÁCERES (2020) “Promomoting cost-effective energy retrofits through improved energy labelling” [PhD thesis]. Technical University of Denmark (DTU). ISBN 87-7877-553-1

Summary: Global energy consumption is projected to increase by 48% in 2040 compared to 2012. A more detailed analysis of the distribution of energy consumption calls attention to the fact that the building sector is responsible for up to 40% of our energy and resource consumption in both developed and developing countries, and up to 30% of all energy related greenhouse gas emissions.Due to their life cycle, which is expected to be several decades, a significant number of residential buildings will need to improve their energy performance in order to effectively reduce energy consumption and greenhouse gas emissions. More than 40% of Europe’s residential buildings have inefficient energy conservation measures because they were built in the 1960s. Moreover, between 1961-1990 the housing stock doubled.By improving energy efficiency in domestic buildings, many benefits can be achieved, such as reduced operating costs, increased indoor environmental quality, user satisfaction and labour productivity. Two important measures to reduce energy consumption and lessen the effect of global warming are the Energy Performance of Buildings Directives (EPBD) and the Energy Efficiency Directive (EED). The main measure concerning the renovation of residential buildings is the establishment of a certification system for the energy performance of buildings which will include recommendations for the optimal or cost-effective improvement of the energy performance of a building or building unit.The most common model used to draw up the list of recommendations that accompanies the energy certificate refers to an automatic list. This is based on standard measures according to the type of building, without considering the actual energy consumption. Examples of these measures include increased insulation, replacement of windows and the use of heat pumps. According to different sources, the list of energy measures is often of little practical use. This is because energy certifiers do not prepare the measures for each specific building, nor do they suggest sensible costs or a chronological order for the implementation of such measures. To address this problem, this research proposes the development of a tool within the framework of the certification system, which will allow the generation of tailor-made recommendations. To this end, the study was developed in four collaborative stages. The first two stages established the basis for what needs to be improved in the certification system. Compiling a literature review, state of the art, interviews and evaluation of certification tools were the main tasks. The third stage of the research explored different techniques that could be used to formulate recommendations. Tools for obtaining geometrical models of buildings were tested and measurements of physical properties relevant to energy consumption were carried out. Finally, according to the results obtained in the previous tasks, a methodology for building evaluation was proposed, which included the use of current technologies with long-term benefits. The results show that it is possible to generate tailor-made recommendations, through real data, with reliable benefits and costs, thereby benefitting all stakeholders involved in the certification process.
Supervisor(s): Assoc.Prof. Jan Karlshøj and Assoc.Prof. Toke Rammer Nielsen from DTU-byg, and Assoc.Prof. Tor Arvid Vik from OsloMet.

Anders Benteson NYGAARD (2019) “Exploring the built environment microbiomes of Norwegian kindergartens and nursing homes” [PhD thesis]. Oslo Metropolitan University (OsloMet). ISBN 978-82-8364-153-0

Summary: BACKGROUND: People spend much of the day indoors. Here they are exposed to the microorganisms that are present in buildings, often referred to as the indoor microbiome. This contact is now known to have relevance for human health and development. The aim of this thesis was to provide new insights into the structure and significance of indoor microbiomes in Norwegian kindergartens and nursing homes, based on modern high-throughput sequencing (HTS) and supplementary analyses. HTS-technologies are enabling unprecedented insights into microbial communities. MATERIALS & METHODS: Analyses was performed on ventilation filter dust and floor dust samples collected from Norwegian kindergartens and nursing homes. Dust samples were analyzed for microbial content by sequencing 16S rRNA gene amplicons on several HTS-platforms. In addition, dust samples were analyzed using supplementary culture-, endotoxin-, and antibiotic resistance genes (ARG)-analyses. RESULTS: It was found that ventilation exhaust-filter dust and indoor floor dust samples had high proportions of human-associated bacterial taxa, some of clinical significance, such as Propionibacterium, Streptococcus, Staphylococcus, and Corynebacterium. In addition, the results of culture-, endotoxin-, and ARG-analyses provided valuable information to supplement the results generated by HTS. Further, it was found that for classification of indoor microbial communities, the Oxford Nanopore Technologies (ONT) MinION was able to provide greater taxonomic resolution than Illumina MiSeq, particularly at the species level. CONCLUSIONS: The works presented in this thesis taken together, show that indoor microbial communities in kindergartens and nursing homes as revealed by the HTS-approach, are clearly structured by human occupancy. Furthermore, the newest addition to the HTS-market, the ONT MinION sequencing platform, provided good taxonomic assignments, by comparison with the Illumina MiSeq platform. This suggests a potential for future use of ONT MinION for studies of indoor microbial communities.
Supervisor(s): Prof. Colin CHARNOCK from OsloMet.
Acknowledgements: The Arctic University of Norway.

Line Røseth KARLSEN (2016) “Design methodology and criteria for daylight and thermal comfort in nearly-zero energy office buildings in Nordic climate” [PhD thesis]. Aalborg Universitetsforlag. ISBN 978-87-7112-560-3

Summary: The objective of this PhD thesis was to arrange for an integrated building design with respect to thermal comfort, daylighting and energy use, applicable for office buildings in Nordic climate. In order to achieve this, it is suggested that modelling of mean radiant temperature (MRT) should be improved by considering the location in the room, accounting for both long and short-wave radiation and that daylighting should be modelled in a dynamic manner. Full-scale measurements have been conducted to verify improved models for MRT and climate-based daylighting and their implementation into the simulation tool IDA ICE. Furthermore, the control of solar shading is given attention, since it is a crucial link between the thermal and daylighting performance. The thesis presents results of an occupant survey with 46 subjects, which was carried out to investigate occupants’ preferences towards automatically controlled venetian blinds and their sensation of glare in a work environment. The results indicate that view to the outside was important for the occupants’ satisfaction. Moreover, a correlation between both vertical eye illuminance and horizontal illuminance at the desk and the occupants’ perception of glare was indicated. Based on these results and findings in the literature, a shading strategy was proposed. Its performance is verified by full-scale measurements and annual simulations.
Supervisor(s): Prof. Per K. HEISELBERG from Aalborg Univ., and Adj.Prof. Ida BRYN from OsloMet.
Acknowledgements: Erichsen & Horgen AS, SBi, Velux AS, École Polytechnique Fédérale, Equa Simulation AB.