The Canadian buildings sector is responsible for 13% of greenhouse gas emissions in Canada. As such, mandatory and voluntary building codes are becoming increasingly stringent on requirements for highly insulated wall assemblies to reduce building heating loads, thereby reducing emissions. However, traditional means of insulating a wall significantly increase its thickness and in scenarios where the building's footprint is constrained this causes a decrease in indoor living space and a reduction in the home's market value. To address this, this thesis proposes thin, highly insulated wood-frame wall assemblies which incorporate highly performing insulation materials. A variety of such novel wall assembly designs are developed and modelled for thermal performance. Three of these designs are tested using the guarded hot box method described in ASTM C1363. It is found that the proposed wall assembly designs provide sufficient thermal performance with little increase in wall thickness compared to traditional wood-frame walls.