Advanced industrialized construction methods enable complex building components and systems to be built with high precision and quality. This manufacturing technique has an advantage to provide cost-competitive and high energy efficient building components and systems for both retrofits and new construction. This document gives an overview of the use of prefabricated panels in building Net Zero Energy Ready wood-frame multi-unit residential buildings (MURBs) in Edmonton.
The airtightness of building must be measured for the evaluation of building energy performance. To make up the reference airtightness value of wooden houses built in Korea, blower door test was carried out in the 36 houses. And, during the test, the causes of air leakage were inspected simultaneously. The result showed that the average of ACH50((air change per hour at air pressure difference 50Pa) measured from light timber frame houses was 3.5 h-1 and the post-beam construction was 5.1h-1. And, insulation with form of foams was advantageous in ensuring building airtightness than glass fiber batt. And, values below 1.5 h-1 of ACH50, threshold for application of artificial air change equipment, had appeared after 2010s. Also, the values varied according to who managed the building construction field. Although only one measurement of CLT(cross laminated timber) residential building could be obtained in 2016, the result showed good airtightness of building with 0.7 h-1.
A balanced combination of heat flows creates suitable conditions for thermal comfort—a factor contributing to the quality of the internal environment of buildings. The presented analysis of selected thermal-technical parameters is up-to-date and suitable for verifying the parameters of building constructions. The research also applied a methodology for examining the acoustic parameters of structural parts of buildings in laboratory conditions. In this research, selected variant solutions of perimeter walls based on prefab cross laminated timber were investigated in terms of acoustic and thermal-technical properties. The variants structures were investigated in laboratory but also in model conditions. The results of the analyses show significant differences between the theoretical or declared parameters and the values measured in laboratory conditions. The deviations of experimental measurements from the calculated or declared parameters were not as significant for variant B as they were for variant A. These findings show that for these analyzed sandwich structures based on wood, it is not always possible to reliably declare calculated values of thermal-technical and acoustic parameters. It is necessary to thoroughly examine such design variants, which would contribute to the knowledge in this field of research of construction systems based on wood.
Australian Life Cycle Assessment Society conference
The use of timber construction products and their environmental impacts is growing in Europe. This paper examines the LCA approach adopted in the European CEN/TC350 standards, which are expected to improve the comparability and availability of Environmental Product Declarations (EPDs). The embodied energy and carbon (EE and EC) of timber products is discussed quantitatively, with a case study of the Forte building illustrating the significance of End-of-Life (EoL) impacts. The relative importance of timber in the context of all construction materials is analysed using a new LCA tool, Butterfly. The tool calculates EE and EC at each life cycle stage, and results show that timber products are likely to account for the bulk of the EoL impacts for a typical UK domestic building.
This literature review aims to provide a general picture of retrofit needs, markets, and commonly used strategies and measures to reduce building energy consumption, and is primarily focused on energy retrofit of the building envelope. Improving airtightness and thermal performance are the two key aspects for improving energy performance of the building envelope and subsequently reducing the energy required for space heating or cooling. This report focuses on the retrofit of single family houses and wood-frame buildings and covers potential use of wood-based systems in retrofitting the building envelope of concrete and steel buildings.
Air sealing is typically the first step and also one of the most cost-effective measures to improving energy performance of the building envelope. Airtightness can be achieved through sealing gaps in the existing air barrier, such as polyethylene or drywall, depending on the air barrier approach; or often more effectively, through installing a new air barrier, such as an airtight exterior sheathing membrane or continuous exterior insulation during retrofit. Interface detailing is always important to achieve continuity and effectiveness of an air barrier. For an airtight building, mechanical ventilation is needed to ensure good indoor air quality and heat recovery ventilators are typically required for an energy efficient building.
Improving thermal resistance of the building envelope is the other key strategy to improve building energy efficiency during retrofit. This can be achieved by: 1. blowing or injecting insulation into an existing wall or a roof; 2. building extra framing, for example, by creating double-stud exterior walls to accommodate more thermal insulation; or, 3. by installing continuous insulation, typically on the exterior. Adding exterior insulation is a major solution to improving thermal performance of the building envelope, particularly for large buildings. When highly insulated building envelope assemblies are built, more attention is required to ensure good moisture performance. An increased level of thermal insulation generally increases moisture risk due to increased vapour condensation potential but reduced drying ability. Adding exterior insulation can make exterior structural components warmer and consequently reduce vapour condensation risk in a heating climate. However, the vapour permeance of exterior insulation may also affect the drying ability and should be taken into account in design.
Overall energy retrofit remains a tremendous potential market since the majority of existing buildings were built prior to implementation of any energy requirement and have large room available for improving energy performance. However, significant barriers exist, mostly associated with retrofit cost. Improving energy performance of the building envelope typically has a long payback time depending on the building, climate, target performance, and measures taken. Use of wood-based products during energy retrofit also needs to be further identified and developed.
This paper aims to develop an artificial neural network (ANN) to predict the energy consumption and cost of cross laminated timber (CLT) office buildings in severe cold regions during the early stage of architectural design. Eleven variables were selected as input variables including building form and construction variables, and the values of input variables were determined by local building standards and surveys. ANNs were trained by the simulation data and Latin hypercube sampling (LHS) method was used to select training datasets for the ANN training. The best ANN was obtained by analyzing the output variables and the number of hidden layer neurons. The results showed that the ANN with multiple outputs presented better prediction performance than the ANN with single output. Moreover, the number of hidden layer neurons in ANN should be greater than five and preferably 10, and the best mean square error (MSE) value was 1.957 × 103. In addition, it was found that the time of predicting building energy consumption and cost by ANN was 80% shorter than that of traditional building energy consumption simulation and cost calculation method.
Timber building has gained more and more attention worldwide due to it being a generic renewable material and having low environmental impact. It is widely accepted that the use of timber may be able to reduce the embodied energy of a building. However, the development of timber buildings in China is not as rapid as in some other countries. This may be because of the limitations of building regulations and technological development. Several new policies have been or are being implemented in China in order to encourage the use of timber in building construction and this could lead to a revolutionary change in the building industry in China. This paper is the first one to examine the feasibility of using Cross Laminated Timber (CLT) as an alternative solution to concrete by means of a cradle-to-grave life-cycle assessment in China. A seven-storey reference concrete building in Xi’an was selected as a case study in comparison with a redesigned CLT building. Two cities in China, in cold and severe cold regions (Xi’an and Harbin), were selected for this research. The assessment includes three different stages of the life span of a building: materialisation, operation, and end-of-life. The inventory data used in the materialisation stage was mostly local, in order to ensure that the assessment appropriately reflects the situation in China. Energy consumption in the operation stage was obtained from simulation by commercialised software IESTM, and different scenarios for recycling of timber material in the end-of-life are discussed in this paper. The results from this paper show that using CLT to replace conventional carbon intensive material would reduce energy consumption by more than 30% and reduce CO2 emission by more than 40% in both cities. This paper supports, and has shown the potential of, CLT being used in cold regions with proper detailing to minimise environmental impact.
This research evaluates the operational heating and cooling energy consumption of cross-laminated timber (CLT) office buildings in China. The evaluations involve a comparison of the energy consumption of a reference RC structure and CLT system office buildings. Computational simulation results are based on IES-VE 2019 and show that the estimated heating energy saving ratio of CLT buildings in Harbin, Beijing, Shanghai, and Kunming to the reference structure are 11.97%, 22.11%, 30.94%, and 23.30% respectively. However, the CLT buildings consume more energy for cooling in the summer. The results of the research show significantly higher heating energy reductions for CLT buildings in the Cold Region and Severe Cold Regions of China. Thus, the application of the CLT system is better suited to northern China than southern China. The results of the research can be used in further assessment of the use of CLT systems in different climatic regions in China.
The aims of the paper were to clarify whether office buildings in the severe cold and cold regions are overheating, especially those with natural ventilation, and whether potential overheating is related to the building materials. The severe cold and cold regions of China were considered to be cool regions during summer. However, with global warming, improvements in the thermal performance of the building envelope and the urban heat island effect, office buildings in these regions are showing different degrees of overheating during summer. Two office building materials commonly used in this area, cross laminated timber (CLT) and concrete block, were simulated in this study. With reference to the overheating standard, the degree of overheating in six cities in the severe cold and cold regions was quantitatively analysed and the extent of overheating for the two building materials was compared. Finally, the influence of thermal insulation on building overheating is discussed, and some suggestions are put forward to improve the relevant national regulations in China. The results show that office buildings in the severe cold and cold regions experience overheating during summer, and CLT buildings are more prone to overheating than concrete buildings during summer. This is attributable to the different thermal mass of the materials. Thick insulation does increase the risk of building overheating, and the effect on concrete buildings is more pronounced. Concrete buildings with an insulation layer can experience overheating for 27–71 h more than buildings without an insulation layer. Insulation on CLT buildings only results in an increase of 11–37 h. When considering the current situation with summer overheating in the severe cold and cold regions, relevant codes should also be modified and improved accordingly to guide building design, so as to achieve low-carbon and energy-saving goals.
There has been no research to date exploring whether timber products can provide effective thermal capacitance in residential or commercial construction. This research is exploring the use of unique mass-timber products to provide a new form of thermal performance capacitance within the built fabric of new and existing homes. The development of mass timber products is a new paradigm in material and building science research in Australia, requiring the accounting for carbon emissions, carbon sequestration, material embodied energy and material thermal properties for this renewable resource. This paper focuses on the results from preliminary building simulation studies encompassing house energy rating simulations and a comparative analysis of embodied energy and carbon storage for a series of house plans in Australia.