Improve Building Energy Efficiency Research Articles

Developing a Reference Material for Diffusion-Controlled Formaldehyde Emissions Testing

Formaldehyde, a known human carcinogen and mucous membrane irritant, is emitted from a variety of building materials and indoor furnishings. The drive to improve building energy efficiency by decreasing ventilation rates increases the need to better understand emissions from indoor products and to identify and develop lower emitting materials. To help meet this need, formaldehyde emissions from indoor materials are typically measured using environmental chambers. However, chamber testing results are frequently inconsistent and provide little insight into the mechanisms governing emissions. This research addresses these problems by (1) developing a reference formaldehyde emissions source that can be used to validate chamber testing methods for characterization of dynamic sources of formaldehyde emissions and (2) demonstrating that emissions from finite formaldehyde sources can be predicted using a fundamental mass-transfer model. Formaldehyde mass-transfer mechanisms are elucidated, providing practical approaches for developing diffusion-controlled reference materials that mimic actual sources. The fundamental understanding of emissions mechanisms can be used to improve emissions testing and guide future risk reduction actions.

Comprehensive Utilization of Solar Energy and Building Energy Saving

Starting from the present situation of energy in China, we discuss how to improve building energy efficiency through comprehensive utilization of solar-energy (SE). Moreover, we study how to adapt the multi-function system for SE, which not only can be used for solar refrigeration but also for solar heating and hot water supply.

Utilizing Diffusion Theory to Model Carbon Dioxide Sources for Improved Energy Efficiency and Ventilation Control

ABSTRACTControlling air exchange rates in response to occupancy has the potential to significantly improve building energy efficiency. A current challenge associated with demand control ventilation research is the development of methods to correlate carbon dioxide concentration to occupancy that are accurate and have low computational overheads for more effective ventilation control. Due to false triggering and drift in readings, ventilation systems are often set to go to full air flow when a minimal carbon dioxide concentration is indicated, which results in excess ventilation and lost opportunity for energy savings. This article describes a new method of relating carbon dioxide source density to carbon dioxide concentration at set locations in a room operating in a reduced ventilation energy-saving mode, by utilizing diffusion theory. Recommendations for carbon dioxide monitor placement are made, along with suggested techniques to correlate occupancy patterns with the developed theory.Dual beam infrared...

A RISK BASED METHODOLOGY TO ASSESS THE ENERGY EFFICIENCY IMPROVEMENTS IN TRADITIONALLY CONSTRUCTED BUILDINGS

Abstract. In order to achieve the CO2 reduction targets set by the Scottish government, it will be necessary to improve the energy efficiency of existing buildings. Within the total Scottish building stock, historic and traditionally constructed buildings are an important proportion, in the order of 19 % (Curtis, 2010), and represent cultural, emotional and identity values that should be protected. However, retrofit interventions could be a complex operation because of the several aspects that are involved in the hygrothermal performance of traditional buildings. Moreover, all these factors interact with each other and therefore need to be analysed as a whole. Upgrading the envelope of traditional buildings may produce severe changes to the moisture migration leading to superficial or interstitial condensation and thus fabric decay and mould growth. Retrofit projects carried out in the past have failed because of the misunderstanding, or the lack of expert prediction, of the potential consequences associated to the envelope's alteration. The evaluation of potential risks, prior to any alteration on building's physics in order to improve its energy efficiency, is critical to avoid future damage on the wall's performance or occupants' health and well being. The aim of this PhD research project is to point out the most critical aspects related to the energy efficiency improvement of traditional buildings and to develop a risk based methodology that helps owners and practitioners during the decision making process.

Development, validation and application of a fixed district heating model structure that requires small amounts of input data

Reducing the energy use of buildings is an important part in reaching the European energy efficiency targets. Consequently, local energy systems need to adapt to a lower demand for heating. A 90% of Swedish multi-family residential buildings use district heating (DH) produced in Sweden’s over 400 DH systems, which use different heat production technologies and fuels. DH system modelling results obtained until now are mostly for particular DH systems and cannot be easily generalised. Here, a fixed model structure (FMS) based on linear programming for cost-optimisaton studies of DH systems is developed requiring only general DH system information. A method for approximating heat demands based on local outdoor temperature data is also developed. A scenario is studied where the FMS is applied to six Swedish DH systems and heat demands are reduced due to energy efficiency improvements in buildings. The results show that the FMS is a useful tool for DH system optimisation studies and that building energy efficiency improvements lead to reduced use of fossil fuels and biomass in DH systems. Also, the share of CHP in the production mix is increased in five of the six DH systems when the heat demand is reduced.

Air Leakage Characteristics and Leakage Distribution of Dwellings in High-rise Residential Buildings in Korea

Reliable airtightness data is needed to estimate the level of air infiltration and the thermal loads for improving building energy efficiency and indoor comfort. While useful information on air leakage in low-rise dwellings exists, there is little data available on dwellings in high-rise residential buildings (particularly those with a central core plan). In this study, airtightness measurements using the fan pressurization method were conducted on approximately 350 dwellings in 4 high-rise residential buildings in Korea. The results were compared with the airtightness requirements for high performance buildings or several airtightness ratings. The measured results showed that average ACH50 (air change per hour at 50Pa) was 2.3. This is within the range of 2~5, which is the level of ′quite tight′ based on the ASHRAE airtightness ratings. The results of the building component test showed that the parts of the dwelling that leaked the most were the internal walls between the residential units.

Desiccant wheel thermal performance modeling for indoor humidity optimal control

Thermal comfort is an important concern in the energy efficiency improvement of commercial buildings. Thermal comfort research focuses mostly on temperature control, but humidity control is an important aspect to maintain indoor comfort too. In this paper, an optimal humidity control model (OHCM) is presented. Model predictive control (MPC) strategy is applied to implement the optimal operation of the desiccant wheel during working hours of a commercial building. The OHCM is revised to apply the MPC strategy. A case is studied to illustrate the practical applications of the MPC strategy.

Optical properties across the solar spectrum and indoor thermal performance of cool white coatings for building energy efficiency

Two single-layer, waterborne cool white coatings for building envelopes were recently developed for use in improving building energy efficiency. After the coatings were manufactured, their optical properties over the solar spectrum and their indoor temperature reduction effect were systematically investigated using appropriate tools, and the advantages/disadvantages of single layer cool white coatings over multilayer ones were discussed in detail. The preparation process enables these two coatings to integrate multiple cooling principles and thereby exhibit high solar heat reflectance and good indoor temperature reduction. The predicted industrial limit of solar heat reflectance for practical reflective cool white coatings is 0.91. Use of cool white coatings significantly reduces radiant heat flux. The temperature reduction effects evaluated by a self-developed device cannot describe adequately the indoor cooling performance of cool coatings.

Heat Consumption Assessment of the Domestic Hot Water Systems in the Apartment Buildings

This study presents the analysis of energy consumption for domestic hot water in apartment buildings in Riga, Latvia. The aggregate data contains information about 39 apartment buildings, including heat energy consumption and domestic hot water (DHW) consumption. The analysis is focused on the heat energy consumption and seasonal characteristics in the DHW system. The analysis characterizes the DHW consumption, energy consumption for DHW and energy losses in the DHW systems in apartment buildings. The energy consumption of DHW needs of households and some other building sectors constitutes a significant part of the building's energy balance. The building energy efficiency improvement measures reduce the heating energy required proportion and logically increase the share of energy consumption for DHW needs. It is likely that the production and distribution of DHW in buildings will constitute a dominant share of both the present, and in particular, the future energy design requirements of buildings. (1) Previously studies carried out in various European countries (2), (3), (4), China (5), (6), Japan (7), (8), (9), USA (10), (11), Canada (12) points the many differences in DHW consumption as well as the tendency to change over time due to a global increase of energy prices, changes in technologies, introducing of individual metering, as well as wide variety of other factors that may appear on local or regional level. Measurements in Denmark documented not only a relatively high energy consumption for DHW in apartment buildings, but also recorded surprisingly large heat losses from the DHW circulation lines (13), (14). Recent investigation of 24 buildings in Danmark shows that most of the energy demand for DHW is lost in the circulation system. The efficiency was 0.30-0.77 (heat loss 23-70%) in apartment buildings and efficiency 0.11- 0.46 (heat loss 54-89%) in office buildings. (1) The Energy Performance of Buildings Directive (EPBD) (15) in the version of 2010, the so-called recast EPBD, demands in annex I 'Common general framework for the calculation of energy performance of buildings (referred to in Article 3)' that '(1) the energy performance of a building shall be determined on the basis of the calculated or actual annual energy that is consumed in order to meet the different needs associated with its typical use and shall reflect the heating energy needs and cooling energy needs (energy needed to avoid overheating) to

Multizone airflow models for calculating infiltration rates in commercial reference buildings

Sixteen reference building models were created in the multizone airflow and contaminant transport program CONTAM in order to support physically based airflow calculations, as well as indoor air quality analyses, that are not possible using the existing EnergyPlus input files of these buildings. The EnergyPlus models were created for assessing new technologies and supporting the development of energy codes in pursuing building energy efficiency improvements. These models employed an oversimplified approach to infiltration in which infiltration rates were input as constant values. A number of additional inputs had to be defined for the CONTAM models to realistically account for airflow, including the addition of several building zones. Annual airflow simulations were performed in CONTAM for six of the sixteen reference buildings. There are clear relationships between the infiltration rates calculated by CONTAM and weather, which are not exhibited in the EnergyPlus results. In addition, the building envelope airtightness values assumed in either approach have a major impact on calculated infiltration rates. The results of this study provide a baseline for subsequent use of these models to investigate design approaches and technologies that are intended to reduce building energy consumption, improve indoor air quality, or both.

As-Is 3D Thermal Modeling for Existing Building Envelopes Using a Hybrid LIDAR System

AbstractThis paper introduces a hybrid method for rapidly measuring thermal data and three-dimensional (3D) geometries of buildings, allowing “virtual” representations of the energy and environmental performance of existing buildings. The 3D thermal models can be further used for many applications by building occupants, owners, and outside consultants to make retrofit decisions. Existing buildings represent the greatest opportunity to improve building energy efficiency and reduce environmental impacts. This research aims to help decision makers improve their buildings by providing reliable, visual information about their buildings’ energy performance using the developed hybrid light detection and ranging (LIDAR) system. The 3D thermal model described consists of point clouds of building geometry with thermal data on each point, including temperature values (°C) and thermal color generated on the basis of the temperature value. Window detection algorithms were developed in this study to create virtual ther...

Shaping climate policy in the housing sector in northern Chinese cities

What are relevant urban development investment strategies for improving building energy efficiency (BEE) and decarbonizing the urban district heating supply in rapidly urbanizing China? Different trajectories of BEE and energy supply technologies are compared in the urban context in a northern Chinese city. Vigorous improvement of BEE will significantly enhance the prospective financial capacity to facilitate deployment of backstop technologies (e.g. carbon capture and storage) in order to decarbonize the energy supply and achieve the long-term targets of low-carbon buildings. Carbon finance instruments should be used to facilitate public policy to accompany the necessary transition in the urban development process. The government-run efficiency procurement scheme will overcome the problem of insufficient incentive and high transaction costs associated with individual Clean Development Mechanism projects. Appropriate investment strategies (allocation of financial resources over the time frame) will allow local governments to harness the large potentials of carbon emissions mitigation while minimizing the risk of long-term technical lock-in in the built environment in Chinese cities.

Energetic and Ecological Analysis of Energy Saving and Passive Houses

Abstract In this paper results of influence of building-installation system parameters on value of energetic coefficients were calculated. Three types of buildings (standard, energy saving and low energy) with heating surface of 100, 150 i 200 m2 were used. The above types of buildings differ on thermal barrier and heating system efficiency. The influence of the gravity and mechanical ventilation systems on the final heat energy of different kinds of houses was shown. Parameters of the certificate for energy characteristics of building were used. Mathematics models of influence of thermal barrier parameters and heating surface on the value of energy characteristics, namely final energy EF, primary energy EP and useful energy EU were established. Influence of such parameters as heating energy factors, ventilation system and energy sources on the energy efficiency improvement of buildings was analyzed. The building environmental assessment system was proposed on the base of energetic and ecological analysis of houses.

Indoor air quality in sustainable, energy efficient buildings

Building designers, contractors, owners, and managers have long been challenged with providing quality indoor environments at a reasonable energy cost. Current efforts to improve building energy efficiency, including goals of sustainability and net-zero energy use, are bringing more focus on how to simultaneously achieve energy efficiency and good indoor air quality (IAQ). While energy efficiency and IAQ are sometimes viewed as incompatible, there are many strategies than support both ends. This article discusses the relationship between IAQ and energy efficiency, with outdoor air ventilation being the primary connection. A number of strategies that are currently being used or proposed to provide both improved IAQ and energy efficiency are highlighted, including increased envelope airtightness, heat recovery ventilation, demand controlled ventilation, and improved system maintenance. In addition, the manner in which various green and sustainable building programs, standards, and guidance documents address IAQ is reviewed. These programs and documents are driving the trend towards sustainable buildings, and the manner in which they consider IAQ is critical to achieving energy efficient buildings with good indoor environments.

A comprehensive study of the impact of green roofs on building energy performance

Abstract Green roofs have several environmental benefits, such as improving building energy efficiency. The present paper provides a comprehensive study of the impact of a green roof on building energy performance. A model of green roof thermal behavior was coupled with a building code to allow the evaluation of green roof foliage and soil surface temperatures. Simulations were conducted for a single-family house with conventional and green roofs in a temperate French climate. In the summer, the fluctuation amplitude of the roof slab temperature was found to be reduced by 30 °C due to the green roof. The heat flux through the roof was also evaluated. In the summer, the roof passive cooling effect was three times more efficient with the green roof. In the winter, the green roof reduced roof heat losses during cold days; however, it increased these losses during sunny days. The impact of the green roof on indoor air temperature and cooling and heating demand was analyzed. With a green roof, the summer indoor air temperature was decreased by 2 °C, and the annual energy demand was reduced by 6%. The present study shows that the thermal impact of green roofs is not functionally proportional to the leaf area index parameter. It also shows the high dependency of this impact on the roof insulation. Finally, the simulations suggest that green roofs are thermally beneficial for hot, temperate, and cold European climates.

A review of building energy efficiency in China during “Eleventh Five-Year Plan” period

With the increasing building energy consumption, the improvement of building energy efficiency (BEE) becomes a key part of the reduction of energy intensity in the “Eleventh Five-Year Plan” period (during 2006 and 2010) in China. For this reason, the China central government has enforced and implemented a series of policies to promote BEE. Based on the analysis of main characteristics of BEE development in China and developmental routes of BEE, this paper systematically explored six fiscal incentive policies. Meanwhile, four specific programs involving new building, existing residential building, government office building and large-scale public building, and applications of renewable energy in building were investigated. Besides, the key factors of BEE development and BEE developmental stages were analyzed. The research revealed the present progress of implementation on BEE policies, and identified the drawbacks of the present BEE mechanism. Moreover, four proposals were recommended to enhance the development of BEE in the next “Five-Year Plan” period.

Multi-objective learning of white box models with low quality data

Improving energy efficiency in buildings represents one of the main challenges faced by engineers. In fields like lighting control systems, the effect of low quality sensors compromises the control strategy and the emergence of new technologies also degrades the data quality introducing linguistic values. This research analyzes the aforementioned problem and shows that, in the field of lighting control systems, the uncertainty in the measurements gathered from sensors should be considered in the design of control loops. To cope with this kind of problems Hybrid Intelligent methods will be used. Moreover, a method for learning equation-based white box models with this low quality data is proposed. The equation-based models include a representation of the uncertainty inherited in the data. Two different evolutive algorithms are use for learning the models: the well-known NSGA-II genetic algorithm and a multi-objective simulated annealing algorithm hybridized with genetic operators. The performance of both algorithms is found valid to evolve this learning process. This novel approach is evaluated with synthetic problems.

Achievements and suggestions of heat metering and energy efficiency retrofit for existing residential buildings in northern heating regions of China

In order to promote energy efficiency and emission reduction, the importance of improving building energy efficiency received sufficient attention from Chinese Government. The heat metering and energy efficiency retrofit for existing residential buildings of 0.15billionm2 in northern heating regions of China was initiated in 2007 and completed successfully at the end of 2010. This article introduced the background and outline of the retrofit project during the period of 11th five-year plan. Numerous achievements that received by retrofit such as environmental protection effect, improvement of indoor environment, improvement of heating system, investment guidance effect, promotion of relevant industries and increasing chances of employment were concluded. Valuable experience that acquired from the retrofit project during the period of 11th five-year plan was also summarized in this article. By analyzing the main problems emerged in the past, pertinent suggestions were put forward to promote a larger scale and more efficient retrofit project in the period of 12th five-year plan.

A performance-based method for energy efficiency improvement of buildings

Building energy standards provide control over excessive use of energy in buildings, promoting energy efficiency and mitigating detrimental environment impacts brought by high energy consumption. The central objective of this paper is to develop correlations that will predict building heat gains and cooling energy consumption for commercial buildings in tropical climates. The energy performance index OTTV was first revised to obtain a new performance index, ETTV for commercial buildings. We developed new correlations to investigate the impact ventilation rates and building aspect ratios had on building cooling energy consumption. Comparing estimated and simulated results, we demonstrated good agreement, even for buildings having different aspect ratios. A study was further conducted to investigate the impact of weather conditions on the developed methodology for estimating the energy consumption of buildings. We employed a design-day weather file to provide simplicity, flexibility and greater ease of use. The design day concept is pivotal in providing key inputs to the cooling energy-estimating methodology yielding good agreement with DOE-2.1E simulated results. We believe that the results presented in this study will benefit building authorities in their pursuit of developing and refining stringent building energy standards in order to realize better energy efficient buildings.

Energy-Efficient Buildings Facilitated by Microgrid

Recent research shows that 20%-30% of building energy consumption can be saved through optimized operation and management without changing the building structure and the hardware configuration of the energy supply system. Therefore, there is a huge potential for building energy savings through efficient operation. Microgrid technology provides an opportunity and a desirable infrastructure for improving the efficiency of energy consumption in buildings. The key to improve building energy efficiency in operation is to coordinate and optimize the operation of various energy sources and loads. In this paper, the scheduling problem of building energy supplies is considered with the practical background of a low energy building. The objective function is to minimize the overall cost of electricity and natural gas for a building operation over a time horizon while satisfying the energy balance and complicated operating constraints of individual energy supply equipment and devices. The uncertainties are captured and their impact is analyzed by the scenario tree method. Numerical testing is performed with the data of the pilot low energy building. The testing results show that significant energy cost savings can be achieved through integrated scheduling and control of various building energy supply sources. It is very important to fully utilize solar energy and optimize the operation of electrical storage. It is also shown that precooling is a simple way to achieve energy savings.