No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Operating and Certifying a Net Positive Energy Building During a Pandemic
The Living Building Challenge is the most rigorous performance-based challenge for buildings in the world. The energy petal of version 3.1 of the challenge mandates 105% net positive energy generation for an entire year of operation. Building simulation plays an important role in predicting building performance; however, there are several assumptions made regarding the expected use of the building, and there is inherent uncertainty associated with building parameters that serve as inputs to the energy models. Ignoring these uncertainties may lead to a false sense of security that the building will meet the strict targets. This paper explores the use of low-and high-resolution tools to check the performance at the whole-building as well as zonal level, and quantify the risk of not achieving energy targets.
This study presents a methodology and process to establish a mandatory policy of zero-energy buildings (ZEBs) in Korea. To determine the mandatory level to acquire the rating of a ZEB in Korea, this study was conducted under the assumption that the criteria of ZEB was a top 5% building considering the building’s energy-efficiency rating, which was certified through a quantitative building energy analysis. A self-sufficiency rate was also proposed to strengthen the passive standard of the buildings as well as to encourage new and renewable energy production. Accordingly, zero-energy buildings (ZEBs) in Korea are defined as having 60 kWh/(m2·yr) of non-renewable primary energy (NRPE) consumption in residential buildings and 80 kWh/(m2·yr) in non-residential buildings, and the self-reliance rate should be more than 20% of the renewable energy consumption as compared to the total energy consumption of the buildings. In addition, the mandatory installation of building energy management systems (BEMS) was promoted to investigate the energy behavior in buildings to be certified as zero-energy in the future. This study also investigated the number of ZEB certificates during the demonstration period from 2017 to 2019 to analyze the energy demand, non-renewable primary energy, renewable primary energy, and self-sufficiency rate as compared to those under the previous standards. For ZEB Grade 1 as compared to the existing building energy-efficiency rating, the sum of the NRPE decreased more than 50%, and renewable energy consumption increased more than four times.
Wireless infrastructure such as WiFi access points
(APs) has grown in popularity while we witness an increased
use of wireless smart devices among communities worldwide.
Therefore it is desirable to use metadata from the WiFi APs
for sensing occupancy as opposed to dedicated physical sensors.
In this paper, we (a) compare the performance of WiFi-based
occupancy sensing with hardware-based occupancy sensing at
room level and then analyze hourly WiFi data across the
UNSW campus (b) to understand the applications of occupancy
monitoring using WiFi data in a campus environment. Our
study explains the feasibility of using WiFi metadata for roomlevel
occupancy estimation by comparing the performance with
hardware beam counter sensors while adding insights on how
campus communities can benefit from using lightweight WiFi
infrastructure for occupancy sensing.
With buildings around the world accounting for nearly one-third of global energy demand and the availability of fossil fuels constantly on the decline, there is a need to ensure that this energy demand is efficiently and effectively managed using renewable energy now more than ever. Most research and case studies have focused on energy efficiency of ‘new’ buildings. In this study, both technical and financial viability of Net Zero Energy Buildings (NZEB) for ‘existing’ buildings will be highlighted. A rigorous review of open literatures concerning seven principal areas that in themselves define the concept of NZEB building is carried out. In practice, a suitable option of the NZEB solutions is needed for the evaluation and improvement for a specific geographical area. The evaluation and improvement has been carried out using a novel hierarchy-flow chart coupled with a Building Information Model (BIM). This BIM or digital twin is then used to thoroughly visualize each option, promote collaboration among stakeholders, and accurately estimate associated costs and associated technical issues encountered with producing an NZEB in a pre-determined location. This paper also provides a future model for NZEB applications in existing buildings, which applies renewable technologies to the building by aiming to identify ultimate benefit of the building especially in terms of effectiveness and efficiency in energy consumption. It is revealed that the digital twin is proven to be feasible for all renewable technologies applied on the NZEB buildings. Based on the case study in the UK, it can be affirmed that the suitable NZEB solution for an existing building can achieve the 23 year return period.
This study compared the energy performance and initial cost of photovoltaic (PV) and heating, ventilating, and air-conditioning (HVAC) equipment for a residential net-zero energy building (NZEB) in different climate zones across the United States. We used an experimentally validated building simulation model to evaluate various electrically-powered and commercially-available HVAC technologies. The HVAC accounted for 23.8% to 72.9% of the total building energy depending on the HVAC option and climate zone. Each HVAC configuration was paired with a PV system sized to exactly reach the net-zero energy target, so the economics were compared based on the initial PV + HVAC cost. Mechanical ventilation was considered with and without heat recovery; the heat recovery ventilator (HRV) saved a significant amount of energy in cold winter months and hot summer months, and the energy recovery ventilator (ERV) provided additional benefit for humid zones. The HRV was cost-effective in the cold northern latitudes of Chicago, Minneapolis, Helena, and Duluth, where energy savings reached 17.3% to 19.7%. In other climates, ventilation without recovery was more cost effective, by 1% to 9%, and sometimes even more energy efficient. The ERV was never the lowest cost option. A ground-source heat pump (GSHP) and an air-source heat pump (ASHP) were compared, with the GSHP providing significant energy savings, 24.3% to 39.2%, in heating-dominated climates (Chicago through Duluth). In warmer climates, the GSHP saved little energy or used more energy than the ASHP. The PV + HVAC cost was lower everywhere with the ASHP, though it is possible for colder climates that a carefully sized GSHP and ground loop could be cost-competitive. The energy and cost data as well as the required PV capacity could guide HVAC and PV designs for residential NZEBs in different climate zones.
The study starts with the analysis of the current situation of both the existing buildings and the energy sector in Egypt, analyzing the energy consumption patterns and the inefficiencies leading to these patterns, then defining the nZEB concept to familiarize the reader with its different aspects. The empirical part of the study utilizes simulation to validate the proposed guideline by applying it on an already existing residential building. The detailed steps of converting an already existing residential building to an nZEB is the final outcome of the research.
With the net zero energy balance for heating, domestic hot water, ventilation and auxiliary energy, the Swiss MINERGIE-A Standard is a major step towards standardized, economically feasible net zero energy buildings. Not only the zero energy balance but also the requirement for limited embodied energy is a new challenge for architects and designers. In the two years since the launching of the Standard and the writing of this paper, approx. 240 buildings have been certified or pre certified. The new standard is widely accepted and its challenges are appreciated in the building sector. A cross analysis shows that a wide range of different energy concepts and embodied energy strategies are possible in the scope of the Standard. The wide variety of options is one of the main findings of the rollout of this new zero-balanced standard.
Sustainable development in the building sector requires the integration of energy efficiency and renewable energy utilization in buildings. In recent years, the concept of net zero energy buildings (NZEBs) has become a potential plausible solution to improve efficiency and reduce energy consumption in buildings. To achieve an NZEB goal, building systems and design strategies must be integrated and optimized based on local climatic conditions. This paper provides a comprehensive review of NZEBs and their current development in hot and humid regions. Through investigating 34 NZEB cases around the world, this study summarized NZEB key design strategies, technology choices and energy performance. The study found that passive design and technologies such as daylighting and natural ventilation are often adopted for NZEBs in hot and humid climates, together with other energy efficient and renewable energy technologies. Most NZEB cases demonstrated site annual energy consumption intensity less than 100 kW-hours (kWh) per square meter of floor space, and some buildings even achieved "net-positive energy" (that is, they generate more energy locally than they consume). However, the analysis also shows that not all NZEBs are energy efficient buildings, and buildings with ample renewable energy adoption can still achieve NZEB status even with high energy use intensity. This paper provides in-depth case-study-driven analysis to evaluate NZEB energy performance and summarize best practices for high performance NZEBs. This review provides critical technical information as well as policy recommendations for net zero energy building development in hot and humid climates.
Buildings are responsible for 36% of CO2 emissions in the United States and will thus be integral to climate change mitigation; yet, no studies have comprehensively assessed the potential long-term CO2 emissions reductions from the U.S. buildings sector against national goals in a way that can be regularly updated in the future. We use Scout, a reproducible and granular model of U.S. building energy use, to investigate the potential for the U.S. buildings sector to reduce CO2 emissions 80% by 2050, consistent with the U.S. Mid-Century Strategy. We find that a combination of aggressive efficiency measures, electrification, and high renewable energy penetration can reduce CO2 emissions by 72%–78% relative to 2005 levels, just short of the target. Results are sufficiently disaggregated by technology and end use to inform targeted building energy policy approaches and establish a foundation for continual reassessment of technology development pathways that drive significant long-term emissions reductions.
The paper starts from the results of one of the six case-studies of the SubTask B in the International Energy Agency joint Solar Heating and Cooling Task40 and Energy Conservation in Buildings and Community Systems Annex 52, whose purpose is to document state of the art and needs for current thermo-physical simulation tools in application to Net Zero Energy Buildings.The authors extend the Net Zero Energy Buildings (Net ZEB) methodological framework, introducing the life-cycle perspective in the energy balance and thus including the embodied energy of building and its components. The case study is an Italian building, tailored to be a Net ZEB, in which the magnitude of the deficit from the net zero energy target is assessed according to a life-cycle approach. The annual final energy balance, assessed with regard to electricity, shows a deficit which makes the case study a nearly Net ZEB, when the encountered energy flows are measured at the final level. Shifting from final to primary energy balance the case-study moves to a non-Net ZEB condition, because of the large difference between the conversion factors of photovoltaics generated electricity and imported electricity. The adoption of a life cycle perspective and the addition of embodied energy to the balance causes an even largest shift from the nearly ZEB target: the primary energy demand is nearly doubled in comparison to the primary energy case.
Retrofitting existing buildings is urgent given the increasing need to improve the energy efficiency of the existing building stock. This paper presents a scalable, probabilistic methodology that can support large scale investments in energy retrofit of buildings while accounting for uncertainty. The methodology is based on Bayesian calibration of normative energy models. Based on CEN-ISO standards, normative energy models are light-weight, quasi-steady state formulations of heat balance equations, which makes them appropriate for modeling large sets of buildings efficiently. Calibration of these models enables improved representation of the actual buildings and quantification of uncertainties associated with model parameters. In addition, the calibrated models can incorporate additional uncertainties coming from retrofit interventions to generate probabilistic predictions of retrofit performance. Probabilistic outputs can be straightforwardly translated to quantify risks of under-performance associated with retrofit interventions. A case study demonstrates that the proposed methodology with the use of normative models can correctly evaluate energy retrofit options and support risk conscious decision-making by explicitly inspecting risks associated with each retrofit option.
The concept of Zero Energy Building (ZEB) has gained wide international attention during last few years and is now seen as the future target for the design of buildings. However, before being fully implemented in the national building codes and international standards, the ZEB concept requires clear and consistent definition and a commonly agreed energy calculation methodology. The most important issues that should be given special attention before developing a new ZEB definition are: (1) the metric of the balance, (2) the balancing period, (3) the type of energy use included in the balance, (4) the type of energy balance, (5) the accepted renewable energy supply options, (6) the connection to the energy infrastructure and (7) the requirements for the energy efficiency, the indoor climate and in case of gird connected ZEB for the building–grid interaction. This paper focuses on the review of the most of the existing ZEB definitions and the various approaches towards possible ZEB calculation methodologies. It presents and discusses possible answers to the abovementioned issues in order to facilitate the development of a consistent ZEB definition and a robust energy calculation methodology.
Why Don't Green Buildings Live Up to Hype on Energy Efficiency?
- Richard Conniff
Conniff, Richard. 2017. "Why Don't Green Buildings
Live Up to Hype on Energy Efficiency?" Yale
Environment 360, May 25.
A Common Definition for Zero Energy Buildings
- Kent Peterson
- Paul Torcellini
- Roger Grant
Peterson, Kent, Paul Torcellini, and Roger Grant. 2015.
A Common Definition for Zero Energy Buildings.
Washhington, DC.
Building Council. 2022a
- U S Green
U.S. Green Building Council. 2022a. "LEED Zero."
U.S. Green Building Council.
Optimize Energy Performance
- U S Green
U.S. Green Building Council. 2022b. "Optimize Energy
Performance." U.S. Green Building Council.