The Canterbury earthquakes in 2010 and 2011 caused significant damage to the Christchurch building stock. However, it is an opportunity to build more comfortable and energy efficient buildings. Previous research suggests a tendency to both under heat and spot heat, meaning that New Zealand dwellings are partly heated and winter indoor temperatures do not always meet the recommendations of the World Health Organization. Those issues are likely to be explained by design deficiency, poor thermal envelope, and limitations of heating systems.
In that context, the thesis investigates the feasibility of building an energy efficient and cost-competitive house in Christchurch. Although capital costs for an energy efficient house are inevitably higher, they are balanced with lower operating costs and improved thermal comfort. The work is supported by a residential building project using Cross Laminated Timber (CLT) panels. This atypical project is compared with a typical New Zealand house (reference building), regarding both energy efficiency and costs.
The current design of the CLT building is discussed according to passive design strategies, and a range of improvements for the building design is proposed. This final design proposal is determined by prioritizing investments in design options having the greatest effect on the building overall energy consumption. Building design features include windows efficiencies, insulation levels, optimized thermal mass, lighting fixture, as well as HVAC and domestic hot water systems options. The improved case for the CLT building is simulated having a total energy consumption of 4,860kWh/year, which corresponds to a remarkable 60% energy savings over the baseline.
The construction cost per floor area is slightly higher for the CLT building, about 2,900$/m² against
2,500$/m² for the timber framed house. But a life cycle cost analysis shows that decreased operating costs makes the CLT house cost-competitive over its lifetime. The thesis suggests that the life cycle cost of the CLT house is 14% less than that of the reference building, while the improved CLT design reaches about 22% costs savings.
Cross-laminated timbers (CLTs) are strong and lightweight structural building materials. CLTs are made from renewable wood resources and have significant economic potential as a new value-added product for the United States. However, market penetration has been obstructed by product affordability and lack of availability for use. Previous studies and projects have surveyed opinions of designers and contractors about the adoption of CLTs. No previous study was found that surveyed cost estimators, who serve the essential function of creating economic comparisons of alternative materials in commercial construction. CLTs are not included in these current cost estimation tools and software packages which may be limiting the potential use of CLT in construction.
The purpose of this study was to discover if cost estimation is being used to make structural decisions potentially affecting the marketability of CLT use in construction and building design because of the ability to estimate CLTs adequately. Through the use of a survey, the re-designing of a building, and discussions with subject matter experts, this study examined the knowledge level of cross-laminated timbers of under-surveyed building construction professions and the relationship between cost estimation and structural material choices. Their responses are demonstrating the need for better cost estimation tools for cross-laminated timbers such as inclusion in the Construction Specifications Institute's classification systems in order for CLTs to become a more competitive product. The study concluded that cost estimation is important for CLT market development, because it is being used extensively in the construction industry.
Most office building construction relies on steel and concrete for mid-high rise office building applications. The primary goal of this thesis is to understand the implications of CLT and mass timber construction systems for mid-high rise office buildings in Seattle by developing a prototypical office building located on a specific site. This research thesis will focus on comparing this prototypical mass timber office building design to the same/similar design using industry standard construction materials for Seattle. The criteria for comparison will include code, cost, schedule and greenhouse gas emissions.