Increasing building energy performance has become an obligatory objective in many countries. Thermal bridge is a major cause of poor energy performance, durability, and indoor air quality of buildings. This paper starts with a review of thermal bridges and their negative impacts on building energy efficiency. Based on published literatures, various types of building thermal bridges are discussed in this paper, including the most effective solutions to diminish their impacts. In addition, various numerical and experimental studies on the balcony thermal bridge are explored. Results show that among all types of thermal bridges, the exposed balcony slab produces the most challenging thermal bridging problem where an integrated thermal and structural design is required. Using low thermal conductivity materials in building construction could help in reducing the impact of thermal bridges. Finally, further investigations are needed to develop more innovative and effective solutions for the balcony thermal bridge.
Driven by updated building energy codes and green building initiatives across the world, vacuum insulation panel, also known as VIP, has become a desired insulation product for building envelope constructions. VIP has initial center-of-panel thermal conductivity of 0.004 W/mK or lower, and integration of VIP in building envelopes can reduce CO2 emissions and contribute towards ‘net-zero’ or ‘near-net-zero’ building constructions. Although VIPs have been applied in real-world constructions across the world, primarily in Asia, Europe and North America, it is still a novel building product under investigation. This overview paper is a summary of fundamentals, constituents, constructions and performances of VIPs. The paper shows there exists many advantages and challenges associated with the integration of VIPs in building envelope constructions. The speed at which VIPs will be integrated in building envelope construction in the coming years remains unclear; nevertheless, it is evident that vacuum technology is the promising way forward for sustainable building envelope constructions in the 21st century.
Buildings are the largest consumers of energy, accounting for nearly 40% of all energy used. Therefore, an effective method of reducing energy consumption is to create and design more efficient buildings. In this paper details of a sustainable and green building design for a small residential home are presented. This design is unique in that it is built to Passive house standards, and using shipping containers. The structure will use four 20 ft. (6.1 m) high and one 40 ft. (12.2 m) high cube containers, with the four 20 ft. (6.1 m) making up the main floor and the 40 ft. (12.2 m) forming the second floor. The size is a modest 820 sq. ft. (76.2 m2) designed for a family with one or two children.
The goal for the building is to be as self-sufficient as possible which makes it ideally suited to an ‘off-grid’ rural setting. However, it can be adapted to be ‘on-grid’ as well. Solar energy will provide all the electricity needs through a photovoltaic battery system, and warm water with a solar water heater. The site will be water neutral by utilising rainwater harvesting and on site waste water treatment. The results from energy modelling, using HOT2000, are presented, as well as an in-depth analysis on different insulation types and strategies. Finally, a cost estimate exercise is conducted and results compared to other passive houses and traditional code compliance buildings.
Authors:J.-F. Masson, S. Bundalo-Perc and P. Mukhopadhyaya
The rise in energy prices, the need to conserve energy and the pressure to protect the environment promote the development of innovative eco-friendly thermal insulating foams for building applications. In this quest, a rapid and accurate method to measure the thermal conductivity of new foams is required during the research and product development stage. Temperature-modulated differential scanning calorimetry (MDSC) provides thermal conductivity values from heat capacity measurements on cylindrical samples less than about 20 mg in weight. This method is the basis of the ASTM E1952 standard method “Thermal Conductivity and Thermal Diffusivity by Modulated Differential Scanning Calorimetry”. In this work, the MDSC and the ASTM E1952 test methods are applied to thermal insulating foams used in construction applications. Measurements on polystyrene, polyurethane, and polyisocyanurate insulations demonstrate that MDSC possesses excellent repeatability, but its application through ASTM E 1952 provides inaccurate thermal conductivity values. Two sources of errors were identified, 1) the use of nitrogen as a purge gas, and 2) the use of an equation that inaccurately relates the measured heat capacity to thermal conductivity. Methods around these difficulties exist, but they remain untested with insulating foams.
Thermal bridging caused by exposed concrete balcony slab is a major source of heat loss through energy efficient building envelopes. Moreover, thermal bridging can also create moisture management and indoor comfort challenges. Numerous investigations have been carried out to reduce heat transmittance through exterior building envelopes and minimize the energy use in buildings. The most effective way to minimize heat transmittance of exposed concrete balcony slabs is to thermally separate the exterior structure from the interior structure using thermal breaks. To enhance thermal separation, this paper investigates the effects of replacing high conductive materials such as reinforced concrete or structural steel with a multilayer composition of high-performance hybrid insulating systems. Reinforcing bars, such as fiber reinforced plastics (FRPs), having lower thermal conductivity than steel are used to connect interior to exterior and transfer loads. Numerical simulation tool THERM is used to study the effects of thermal breaks on energy performance of the concrete slab balcony joints. Simulation results indicate significant thermal performance improvement while high-performance hybrid insulating systems were used for exposed concrete balcony slab constructions, compared to traditional insulating systems used in similar constructions
Authors:K. Tiwana, P. Mukhopadhyaya, E. Zalok, D. Van Reenen, C. Copeland and P. Newman
This paper discusses the results of a research project which aimed at determining the hygrothermal (i.e. thermal and moisture) performance of the Canadian wood-frame building envelope construction in the city of Shanghai in China. The performance assessments of the wood-frame walls were conducted using the two-dimensional hygrothermal simulation tool called hygIRC-2D. In this study an in-fill type wall was considered and hygrothermal simulations were carried out for the weather conditions of Shanghai. Investigations were conducted to determine the influence of the vapour barrier, exterior stucco cladding material and different types of sheathing boards on the moisture performance of in-fill walls. Additional simulations were carried out to determine the influence of air leakage on the moisture performance of in-fill walls. The outputs from the simulations were analysed with the help of a hygrothermal response indicator called RHT index. It was concluded that the design of the in-fill wall including a rain screen but omitting a vapour barrier is expected to lead to the maximum reduction in hygrothermal loading when exposed to the weather conditions of Shanghai, China.