Conferences and papers
How do nZEB dwellings perform in reality?
The following papers and presentations look at how nZEB dwellings perform with respect to interior temperatures, indoor air quality, energy consumption and occupant satisfaction. The key question is, do they perform as expected?
"Recorded energy consumption of nZEB dwellings – and
corresponding interior temperatures"
By Dr Shane Colclough et al., 2020,
Ireland is mandating the unprecedented mass market deployment of low-energy dwellings via the near Zero Energy Buildings (nZEB) standard, from 1 January 2021 due to the EU wide Energy Performance of Buildings Directive (EPBD). This is among the first academic papers to provide recorded energy and temperature data for nZEB compliant dwellings in Ireland. It reports on initial results of the www.nZEB101.ie Post Occupancy Evaluation project, the objective of which is to uncover key nZEB design and operations lessons, to aid the next iteration of the country’s building regulations. This paper reports on the analysis of winter temperatures and the energy consumption of 17 nZEB compliant dwellings, each of which have been monitored for at least a 12 month period. While analysis of further properties is needed to further validate the findings, key findings to date include significantly higher than expected interior temperatures and energy consumption, and a usage profile which is significantly different from the assumptions in the DEAP National energy rating software.
"Post Occupancy Evaluation of 12 Retrofit nZEB dwellings: The impact of high in-use interior temperatures on the predictive accuracy of the nZEB Energy Standard"
by Dr Shane Colclough, being published
This paper will be put on the website soon- please revisit the website to access papers as they are published
The performance of energy efficient components
This section looks at the performance of the individual components used in nZEB dwellings. This includes the performance of wall insulation and also the performance of the heat pumps. These are critical components in successful nZEB implementation.
"The Performance Potential of Domestic Heat Pumps in a
Temperate Oceanic Climate"
By O'Hegarty et al.,2020
Domestic purpose heat pumps are commonly rated based on a manufacturer specified single Coefficient of Performance (COP). The performance of heat pumps however, is known to vary widely for different seasons and for varying climate conditions. This study is part of an in-depth analysis of nZEB homes through the nZEB101 project funded by the Sustainable Energy Authority of Ireland (SEAI). In advance of undertaking a large-scale monitoring project, preliminary studies of nZEB technologies are being undertaken. This paper outlines a simplified method for calculation of the heat pump’s seasonal performance factor over six heating seasons in a modelled nZEB dwelling in Ireland using real hourly weather data. The study has found that while Seasonal Performance Factor (SPF) values of 4.5 (as often claimed by manufacturers) are achievable, favorable operating conditions are required to achieve these high values. In a new building where under floor heating and modern convective radiators are installed, the primary energy associated with the space heating is approximately 40% that of a natural gas boiler. The total CO2 emissions are also 47% less. However, in a retrofit nZEB building where existing radiators (which require higher outlet temperatures of approximately 65℃) are used, the difference in CO2 emissions from a heat pump and gas boiler is almost negligible. The potential for heat pumps can be improved further by decarbonizing the grid and improving grid and plant production efficiencies.
"Assessment of Highly Insulated nZEB Walls"
By O'Hegarty et al.,2020
Proponents of Passivhaus and nZEB often emphasise a ‘fabric first approach’ to ensure optimumenvelope design, and by extension highest building energy performance. The energy performance of two similar walls, of two separate nZEB-compliant dwellings, are assessed in this paper. The walls have similar construction details, consisting of a layer of 200 mm of mineral wool on the exterior side and a block construction on the interior. The walls are investigated by comparing theoretical and in-situ conductance values while also
estimating the embodied energy of both walls. The study found that, although the walls were of similar design and the test was conducted using the same methodology (in accordance with ISO 9869-1), that there was a significant different between the in-situ performance of both walls. One wall performed only slightly worse than the design value while the other performed more than two times worse. This research extrapolates on the
findings by comparing theoretical heat loss scenarios with both wall types and calculates A) the potential building energy performance for both walls and B) the carbon and energy payback for the insulation used to achieve such high performance. The results demonstrate the importance of good practice in construction of the building envelopes and in the manufacturing, robustness and quality control of the various building components.
Operational and embodied energy analysis of 8 single-occupant dwellings retrofit to nZEB standard
By O'Hegarty et al.,2020
In line with the Energy Performance of Buildings Directive, Irish dwellings are being retrofit to near Zero Energy Building (nZEB) standards - with a number of the deep energy retrofits classified as A-rated. As a result of the low operational energy, the embodied energy share of an nZEB's life cycle energy is significantly increased. Therefore, to obtain a holistic picture of the change in energy profile of buildings, the embodied energy of the material added to achieve that low performance should also be taken into account. This paper presents results from a case study of 8 single-occupant terrace bungalows retrofit to nZEB
standard. The pre- and post-retrofit operational performance is first estimated using the Irish Dwelling Energy Assessment Procedure (DEAP). The post-retrofit operational performance of the space heating and domestic hot water heating system is also measured over a year. The embodied energy is estimated by way of embodied carbon/energy calculations. Monitored results of the 8 similar buildings exhibit a wide variance of operational energy consumption while the embodied energy is (by nature of the calculation) consistent. The average estimated primary energy requirement for the buildings was 674 kWh/(m2ᐧyear) pre-retrofit and 38 kWh/(m2ᐧyear) post-retrofit while the average measured primary energy requirement for space heating and hot water alone was 119 kWh/(m2ᐧyear) – ranging from 74 to 167 kWh/(m2ᐧyear) for the 8 houses. The embodied energy of the materials and technologies used to retrofit the buildings was 676 kWh/m2. Despite the building performing worse than expected, desirable primary energy and carbon paybacks of 2.0 and 6.1 years were achieved respectively. These positive payback periods are largely due to the very poor operational performance of the buildings pre-retrofit.
Do low-energy and nZEB dwellings make financial sense?
The following papers have been produced to carry out a financial analysis, based on both BER values for the energy consumption of dwellings, and also the recorded energy consumption of dwellings.
"Unlocking the potential - Low-Energy Dwelling & Heat Pump.
Investigating their multiple benefits, and how to increase adoption rates"
By Dr Shane Colclough et al.,2020
This paper is novel in that it is a first attempt to analyse the direct and indirect costs and benefits of constructing a 3-bed social house dwelling to low-energy standards in Northern Ireland. It uses data on direct construction and energy costs and augments this with estimates for some of the indirect benefitsfor three potential low energy upgrade for the real scheme of new dwellings. While estimation of Indirect Benefits is by it’s nature imprecise, the analysis provides fresh insights and indicates that a financial argument
exists for constructing to low-energy standards at both societal and individual levels. However the analysis also demonstrates that the decision-maker is dis-incentivised, leading to poor adoption rates for the low energy, carbon efficient dwellings. This has potential policy implications for UK social housing given the conflict with the UK’s stated decarbonising objectives.
"The Costs, Benefits and Stakeholder Analysis of an Irish Social Housing Deep Energy Retrofit Case Study"
By Dr Shane Colclough,2021
This paper analyses the results of a pilot deep energy retrofit (DER) implementation
including the financial perspectives of the stakeholders with the aim of assisting DER policy development. The Multiple Beneficiary Analysis (MBA) provides technical and energetic details for a recent 12-unit DER social housing project and quantifies the multiple direct and indirect benefits – e.g. financial, economic and societal to enable a stakeholder (beneficiary) analysis. The analysis is apposite given the urgent need for effective policy development in order to enable the achievement of the low-energy retrofit mandated by the EU. The MBA finds that the stakeholder who benefits most (the tenant) makes no financial contribution to the higher standards and while the Central Exchequer also benefits significantly, the stakeholder who makes the upgrade decision (landlord) is financially dis-incentivised. Given the significant benefits which accrue to the Central Exchequer, there is an opportunity for strategic investment by the government to unlock the benefits of low energy dwellings. This would simultaneously realise ongoing financial benefits, “seed” the capability within industry and crucially increase the knowledge and understanding of low energy dwellings which is necessary to enable widespread adoption. The key finding is that despite potential returns of approximately twice the investment, and the urgent need to retrofit existing buildings, the required DER uptake is unlikely as the decision-makers require financial support to unleash the multiple benefits of energy efficient dwellings. A self-financing support is suggested for the case study for consideration.
"Deep Energy Retrofit Case Study – who pays, who
benefits, and how best to inform Policy"
By Dr Shane Colclough, 2021,
This paper provides an economic analysis of a recent 12-unit (1 bed 31m2) Deep Energy
Retrofit (DER) social housing project (See Table 1). Based on real costs and monitored post
retrofit performance, it updates the projected benefits described in a previous in-depth
analysis paper [Colclough, 2021]. Through quantification of financial, economic and societalbenefits, a stakeholder analysis is enabled, unveiling a key barrier to DER in Ireland
"Are nZEBs nearly zero enough ? Considerations of nZEB housing and standards as a solution to building associated climate change"
By Oliver Kinnane et al., 2021,
All new dwellings in the European Union are to abide by the near Zero Energy Building (nZEB) Standard from 2020. Accordance to this standard will result in a much improved next generation of residential buildings, over buildings built even ten years ago. This study, however, investigates if considering the urgent matter of climate change, buildings built to this standard are even efficient enough. Or more pertinently it asks even if we build these new buildings to these high standards, are we building too many buildings? Is there enough of our ‘carbon budget’ remaining, or might the construction and operation of a new cohort of buildings push us beyond boundary limits? This paper evaluates nZEB in the context of the above narrative. It places nZEB as the optimum build solution for that which will be built and then questions if the nZEB standard is stringent enough. Does it stipulate a performance that is near enough to zero? And can it capture the full range of performance in and across nZEB homes. Are broader or stricter regulations required to ensure these buildings are nearly zero in operation. Or as previously questioned, is building a folly when considered in light of the greater climate crisis context?
The paper outlines a thought experiment based on construction projections until 2060. Phenomena of building usage are identified using some real data from case study buildings of the nZEB101 project.
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