Net Energy Analysis of Double Glazing for Residential Buildings in Temperate Climates

Energy used in buildings is a major contributor to Australia’s energy consumption and associated environmental impacts. The advent of complex glazing systems such as double glazing, particularly in northern America and Europe, has partially closed a weak thermal link in the building envelope. In milder climates, however, building envelope features may not be as effective in life cycle energy terms, i.e. including the embodied energy of their manufacture. A net energy analysis compares the savings in operational energy to the additional requirements for embodied energy, in terms of the energy payback period and energy return on investment. The effectiveness of double glazing is determined for an Australian residential building. A wide range of building operation regimes was simulated. These results support the principle of installing double glazing in residential buildings in Melbourne, Australia, at least in terms of net primary energy savings.

Investigating glazing system simulated results with real measurements

Over the past decades there has been a great deal of research related to simulation programs that calculate glazing thermal performance. In this study, several glazing systems were designed using VISION 3 (University of Waterloo, 1992) and WINDOW-6 (Lawrence Berkeley National Laboratory, 2010). The systems were fabricated and experimentally tested in-situ for a summer month. It was found that in most cases the predicted results of the glass temperature matched those measured, though slight discrepancies were observed during periods of high solar radiation, particularly for more complex systems and systems with shading devices.

A simple-to-use calculator for determining the total solar heat gain of a glazing system

Architects and designers could readily use a quick and easy tool to determine the solar heat gains of their selected glazing systems for particular orientations, tilts and climate data. Speedy results under variable solar angles and degree of irradiance would be welcomed by most. Furthermore, a newly proposed program should utilise the outputs of existing glazing tools and their standard information, such as the use of U-values and Solar Heat Gain Coefficients (SHGC’s) as generated for numerous glazing configurations by the well-known program WINDOW 6.0 (LBNL, 2001). The results of this tool provide interior glass surface temperature and transmitted solar radiation which link into comfort analysis inputs required by the ASHRAE Thermal Comfort Tool –V2 (ASHRAE, 2011). This tool is a simple-to-use calculator providing the total solar heat gain of a glazing system exposed to various angles of solar incidence. Given basic climate (solar) data, as well as the orientation of the glazing under consideration the solar heat gain can be calculated. The calculation incorporates the Solar Heat Gain Coefficient function produced for the glazing system under various angles of solar incidence WINDOW 6.0 (LBNL, 2001). The significance of this work rests in providing an orientation-based heat transfer calculator through an easy-to-use tool (using Microsoft EXCEL) for user inputs of climate and Solar Heat Gain Coefficient (WINDOW-6) data. We address the factors to be considered such as solar position and the incident angles to the horizontal and the window surface, and the fact that the solar heat gain coefficient is a function of the angle of incidence. We also discuss the effect of the diffuse components of radiation from the sky and those from ground surface reflection, which require refinement of the calculation methods. The calculator is implemented in an Excel workbook allowing the user to input a dataset and immediately produce the resulting solar gain. We compare this calculated total solar heat gain with measurements from a test facility described elsewhere in this conference (Luther et.al., 2012).

The next step in energy rating: the international ETTV method vs. BCA Section-J glazing calculator

The most important prevention in minimizing energy transfer in commercial buildings is the treatment of glazing in the building facade. In a commercial building, while the impacts of roof, walls and floors on the overall heating and cooling loads of the building have low effects, glazing is likely to be the most important factor. This paper investigates the BCA Section-J glazing calculator and the ETTV (Envelope Thermal Transfer Value) methods and tries to look for differences as well as similarities in calculation of building envelopes energy performance. For this investigation, a hypothetical high-rise commercial building in Melbourne, Australia is considered when evaluating the energy performance of the envelope through these two methods. Both methods consider the U-Value of glass and wall materials as well as Solar Heat Gain Coefficient (SHGC) and Shading Coefficient (SC) of the glass. Findings in this research project indicate differences and significant discrepancies between the BCA Section-J and ETTV methods in evaluating the energy performance of commercial building façades. Issues of calculation weaknesses are identified with the lack of air leakage and infiltration of a particular façade design or window to wall ratio (WWR). Suggestions have been made where improvement to the overall energy calculation through facades of a commercial building is needed.

High performance low-energy buildings

The era of legislation and creditable methods towards producing sustainable buildings is upon us. Yet, a major barrier to achieving environmental responsive design is in the lack of available information at the programming or pre-design phases of a project. The review and evaluation of climate as well as energy-efficient strategies could be difficult to consider at these preliminary stages. Until recently, introducing energy simulation tools at the design stage has been difficult and perhaps next to impossible at a pre-design or programming stage. However, analysis of this sort is essential to ‘green building rating’ or performance assessment schemes such as LEED (Leadership in Energy and Environmental Design) and BREEAM (Building Research Establishment Environment Assessment Method). This paper discusses the implementation of a particular tool, ENERGY-10, where ‘basecase’ building defaults are compared to a low-energy case which has applied multiple energy-efficient strategies automatically. An annual hour-by-hour simulation provides a daylighting calculation with a subsequent thermal evaluation. Calculation results provide energy consumption, peak load equipment sizing, a RANK feature of the energy-efficient strategies, reporting of CO2, SO2 and NOx reduction, optimum glazing type as well as excellent graphic output. Consideration is given as to the approach of how such information can be introduced into the building project brief enforcing a low-energy
performance target.

Assessment of thermal comfort near a glazed exterior wall

In many highly glazed buildings, the thermal comfort of the occupants will tend to be related to the incoming solar energy and the solar heat gain coefficient of the glazing. Many real buildings tend to be deep relative their height and therefore, areas close to the facade receive a much greater amount of the incoming energy than those farther from it. In turn, this imbalance leads to occupants near the facade experiencing a high dissatisfaction with their thermal environment (near-facade zone). This study experimentally examines the thermal environment of occupants near the facade of a glazed building wall. It presents results for Fangers’ predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD) and explores some options for improving the thermal environment in this near-facade zone.

Designing for thermal comfort near a glazed exterior wall

In many highly glazed buildings, the thermal comfort of the occupants will tend to be related to the incoming solar energy and the heat transfer behaviour of the glazing. In this study, several glazing systems were designed using the software tools VISION 3 (University of Waterloo 1992) and WINDOW-6 (Lawrence Berkeley National Laboratory 2011), with a view to improving thermal environment of occupants near the glazed wall of a commercial office. The systems were fabricated and experimentally tested to validate the software modelling results. Subsequently, the glazing systems were retro-fitted to the office and tested in situ for a summer month. Results of this testing, in the form of Fangers’ predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD), are presented, and some options for improving the thermal environment in this near-façade zone are discussed.

Developing a facility for glass façade performance testing

This research aims to investigate whether real spaces can support legitimate measurements on glazing energy and thermal comfort analysis. This paper presents the development of a research facility for doing this. It will test simple to complex glazing and shading systems in a real (occupied) interior office environment. The purpose of this research project is to compare measured results with those being simulated with existing software and to discover discrepancies between simulation and real measured results. What parameters characterize a glazing system, whether simple or complex? Can these parameters be used to predict the energy transfer and comfort in the space? One must begin with simple glazing systems and verify measured with readily known simulated results. It is, at present, very difficult to use geometric based software with thermal based software to predict the performance of complex glazing systems. However, if we can characterize glazing systems with a set of reliable measurements, we can provide the data necessary for predicting performance in a live space. Specifically, the Solar Heat Gain Coefficient (SHGC) is a variable parameter based upon solar incident angle to a glazing system and is intended to be measured in its integral components: solar transmittance and inward-flowing fraction (radiative/convective) heat gain. A new instrumental approach through variable surface coated heat flux meters is being investigated to provide the measurement of interior glazing surface radiative and convective heat gain. The results suggest that this instrumentation may support be a viable method of testing inward-flowing heat gains from the interior glass surface. The test set-up also considers the application of a well-known B&K 1221 Comfort Meter for determining thermal comfort responses in the ‘perimeter zone’ on the interior side of a façade. This work requires further investigation, but is intended to be used in conjunction with solar pyranometers measuring transmittance as well as the heat flux meter and surface temperature instrumentation.

Disaggregation of household energy consumption patterns in Australian

Improving energy efficiency is an important target to be achieved in residential building development and household behaviour. The aim of this research is to help building professionals and policy makers understand the current housing situations and householders’ behaviour regarding energy consumption. The results of a survey of energy consumption, including house situations and householder behaviour, of 504 households in New South Wales Australia are reported. Twelve features affecting household energy consumption are investigated. These features included cooking appliances, refrigerators, laundry appliances, televisions, computers, gaming consoles, hot water systems, space cooling and heating systems, glazing, insulation, lighting, and other major energy consumption facilities. The differences of these features across different households with different physical characteristics, social-demographic features and geographical areas are analyzed. Based on the disaggregate study, it is found that mandatory policy, geographical and socio-economic factors can significantly affect the selection of fixtures and appliances in the households. It is also found that the positive effect of the government’s mandatory policy implementation on household energy consumption behaviour is evidenced. The findings will be of use in sustainable residential building development policy-making, and tailoring the regulations and standards with consideration of the various geographical and socio-economic factors.

Thermal evaluation of a greenhouse in a remote high altitude area of Nepal

Remote communities in the high altitude areas of Nepal suffer both chronic and acute malnutrition. This is due to a shortage of arable land and a harsh climate. For seven months of the year, the harvesting of fresh vegetables is almost impossible. Greenhouse technology, if appropriate for the location and its community, can extend the growing season considerably. Experience in the Ladakh region of India indicates that year-round cropping is possible in greenhouses in cold mountainous areas. A simple 50-m2 greenhouse has been constructed in Simikot, the main town of Humla, northwest Nepal. This paper describes the evaluation of the thermal performance of that greenhouse. Both measurement and simulation were used in the evaluation. Measurements during the winter of 2006-7 indicate that the existing design is capable of producing adequate growing conditions for some vegetable crops, but that improvements are required if crops like tomatoes are to be grown successfully. Options to improve the thermal performance of the greenhouse have been investigated by simulation. Improvements to the building envelope such as wall insulation, double-glazing and using a thermal screen were simulated with a validated TRNSYS model. The impact of the addition of nighttime heat from internal passive solar water collectors was also predicted. The simulations indicate that the passive solar water collectors would raise the average greenhouse air temperature by 2.5°C and the overnight air temperature would increase by 4.0°C. When used in combination, overnight temperatures are predicted to by almost 7°C higher.

Sub-lethal UV-C radiation induces callose, hydrogen peroxide and defence-related gene expression in Arabidopsis thaliana

Exposure of plants to UV-C irradiation induces gene expression and cellular responses that are commonly associated with wounding and pathogen defence, and in some cases can lead to increased resistance against pathogen infection. We examined, at a physiological, molecular and biochemical level, the effects of and responses to, sub-lethal UV-C exposure on Arabidopsis plants when irradiated with increasing dosages of UV-C radiation. Following UV-C exposure plants had reduced leaf areas over time, with the severity of reduction increasing with dosage. Severe morphological changes that included leaf glazing, bronzing and curling were found to occur in plants treated with the 1000 J·m(-2) dosage. Extensive damage to the mesophyll was observed, and cell death occurred in both a dosage- and time-dependent manner. Analysis of H2 O2 activity and the pathogen defence marker genes PR1 and PDF1.2 demonstrated induction of these defence-related responses at each UV-C dosage tested. Interestingly, in response to UV-C irradiation the production of callose (β-1,3-glucan) was identified at all dosages examined. Together, these results show plant responses to UV-C irradiation at much lower doses than have previously been reported, and that there is potential for the use of UV-C as an inducer of plant defence.