Travail de fin d'études / Projet de fin d'études : Comparison of the LCC of two timber construction technologies for single family dwellings

Abstract

This master thesis starts with environmental and economic observations. The first thing is that using timber construction systems is an excellent way to reduce the environmental impact of the construction sector. More than one house out of ten is built in timber in Belgium, and the number of Cross Laminated Timber (CLT) constructions is constantly increasing. The second thing is that the environmental impact is not the only matter for people aiming to build a house. Economic concerns are usually a top priority.

In this context, a widespread belief concerning timber construction is the origin of this thesis. It seems like people have this idea that CLT construction for residential buildings is way more expensive than stud-wall construction (which is the most used timber technique in Belgium). However, finding scientific studies proving that statement is quite complex. It appears that there is a lack of literature concerning the subject.

Therefore, the aim of the thesis is to run an economic comparison of two construction technologies for residential buildings: stud-wall construction and CLT system. The financial comparison is made through a Life Cycle Cost (LCC) analysis which is regulated by the ISO 15-686 standard. The costs that are evaluated include investment and periodic costs. The first ones represent the construction budget (materials, workforce), and the second ones correspond to the costs occurring during the life cycle of the building (energy fees, maintenance budget).

The LCC analysis is made on a real reference building (stud-wall construction) and a CLT alternative. The case study used in this thesis is a single-family passive house built with a stud-wall structure. It is representative of Belgian timber dwellings. The CLT alternative is defined with information coming from literature and discussion with experts. Only the wall configurations are changed. All other parameters are equal to those of the reference building. This way, the economic comparison concerns only the structure of the house, as intended.

The LCC is run on a 50 years lifespan. The results of the study prove that the construction of a house is more expensive with a CLT system than with a stud-wall structure. However, the study shows that there is only a 7 % difference between the two LCC. This is explained by the excellent energetic properties of the CLT system that leads to annual energy savings. Over decades, these annual economies make a significant difference.