Purpose - The focus of this paper is to investigate the cost side of “green” building construction and if increased investment cost are profitable taking the reduction in operating cost into account. The investment viability is approached by comparing investment in conventional and “green” residential building, particularly low-energy building, using real construction and post-occupancy condition.

Design/methodology/approach - The key data was obtained by surveys and personal interviews. First survey was directed to the companies which had experience of building lowenergy housing and the second survey to the housing companies that actively manage operation of low-energy houses.

Findings - Findings indicate that low-energy buildings are considered as interesting and good business opportunity and life cycle cost analysis suggests that low energy building (particularly passive house) is a better investment than conventional residential building. At the same time government initiative and the construction regulations are found to have strong motivation power towards development of “green” buildings.

Originality/ value – This paper provides insights to the investment decisions and contributes to understanding of the construction and operation of energy-efficient residential buildings.

A fundamental goal for buildings is to deliver safe shelter and good indoor climate for the occupants. Creating the thermal comfort begins with modelling, which is based on mathematical descriptions of the designing building, its surroundings, and regional climate. The post-occupancy evaluation that includes occupant feedback can be used as a control measure to verify these calculations and an important link in closing the learning loop for investor, designer and builder. The evaluation and observations given by residents and housing managers are significant for designing and constructing good quality buildings, suited to occupant needs and expectations.

The aim of the paper was to attempt a buildings assessment based on occupant feedback and housing manager observations. To investigate indoor climate in energy-efficient housing, three low-energy multi-family residential buildings and a control group of three conventional multi-family buildings were carefully selected. The objective of this multi-case study was to investigate thermal comfort and capture the circumstances and conditions specific to passive multi-family housing.

The results indicate that the low-energy profile of a building had a limited influence on the decision to rent the apartment, however residents were generally proud to live in environmentally friendly buildings. Moreover, tenants also suggested that living in the energy-efficient buildings increased their environmental awareness, making their behaviour more environmentally friendly. Residents of low-energy houses gave better rating for indoor climate than that in conventional houses, which suggests higher satisfaction with the product; however, tenant feedback identified some problems with ventilation system and space heating.

Findings indicate that there no significant difference in operation and management of  owenergy buildings, however information and communication activities are absolutely crucial in successful management of low-energy buildings. Moreover the low energy buildings requires the same amount or less adjustments than in conventional houses, which brings further evidence that in the life cycle perspective low energy houses are a better investment.