Development of price index models for architectural and environmental quality for residential developments in Hong Kong

Abstract

Residential property prices in Hong Kong are affected by property-specific characteristics. However, despite Hong Kong people spend a large amount of their incomes on housing, they have not been given the information to enable an objective and continuous evaluation of the property-specific quality of a residential unit and the price for that. Architectural and environmental attributes are the two major categories of property-specific characteristics. Amongst the two categories, architectural attributes including floor area, building form, floor level, window area, orientation, etc. can easily be measured. But this is not the case for environmental attributes which include indoor air quality, acoustic environment, quality of view, daylight performance, and natural ventilation performance. The reason is that there is no suitable tool for homebuyers to assess their performance. This thesis presents the use of field measurements, site visits, computer simulations and statistical analysis for the development of simple indicators for easy and yet scientific quantification of the environmental performance of residential units. Based upon the simple indicators, and by the use of the hedonic price approach, the influences of architectural and environmental attributes on the residential properties market price are identified. A series of noise level and PM₁₀ concentration measurements were conducted at roadsides of two busy roads in Hong Kong and at ten carefully selected residential units located nearby. Regression analysis on the measurement results indicated that both the traffic-induced noise and the PM₁₀ concentrations at the units studied exhibited a linear correlation with the logarithm of their corresponding distance from road (log R). The result concluded that "log R" could be adopted as a performance indicator for evaluating the combined impact of road traffic on the noise and air quality of a residential unit. In developing a simple indicator for assessing daylight performance and view obstruction, simulations for generations of mean shading mask values (SMK); site visits for ascertaining actual view obstructions; and calculations of the average angle of unobstructed sky (θ) were conducted for a large number of residential units. Through correlation analysis between SMK and θ of 708 residential units, the use of θ as a simple indicator for assessing daylight performance and view obstruction of residential units was confirmed. The influence of different parameters on natural ventilation performance of a hypothetical living room was evaluated. The hypothetical living room was formulated based on an extensive survey of characteristics of living rooms in a representative estate in Hong Kong. The evaluation took into account the living room area, window type, window area, window orientation, and ventilation mode. A total of 224 CFD simulation cases were conducted and the corresponding mean age of air (MAA) values were determined. Through regression analysis, it was found that MAA was most affected by the ventilation mode adopted (VENT) and thus it was selected as the performance indicator for natural ventilation performance. The last part of study focused on the development of the price index models for identifying the willingness-to-pay (WTP) for better architectural and environmental attributes of residential units. The five attribute characteristics, i.e. LogR, θ, VENT, floor area (FLA) and living room window orientation (ORI) were adopted for a price analysis by hedonic price approach. Based upon the 2005 transaction records, the price index models for two residential estates of different homebuyer groups were developed. Three performance indicators (LogR, θ, and VENT) are developed in this study. They enable an objective and continuous evaluation of the environmental quality of a residential unit. Moreover, the WTP information will encourage building developers constructing for better environmental quality; and help homebuyers making home purchase decisions.