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STUDY OF HOME RENOVATION FROM THE CONSTRUCTION HISTORY
Abstract
The analysis of the history and of the renovation costs in a wooden detached house clarified the following : A home renovation tends to occur after about 12 or 30 years after the house was built. The residents don't always use the same builders. They make decisions for the renovation by themselves. There are very few cases that an architect joins in a renovation. The house renovation costs are generally related to extension scale and its age. To continue living, preserving the renovation history and making a system that a professional should be involved in the renovation are needed.
Investigating architecture statistics with consideration of construction and building period, this paper shows that the renovation cost of housing and non-housing per order decreased by half between 2008 and 2017 while the number of orders increased, and that the average renovation cost between 2008 and 2017 of housing built before about between 20 and 55 years per unit area is the highest. This paper also evaluated the renovation costs for 30 years and 60 years. Compared with the other estimation and the other paper, these previous estimations are respectively about 3 times and 9 times higher than this paper.
We analyzed a survey of remodelers of detached houses in urban areas. The survey found that remodelers were diverse, with distinctive characteristics depending on the type of business. Remodelers respond to customer concerns and provide consultation. Some collaborate with other industries to distribute used homes. However long-term relationships with residents have not been established, and there are issues such as quality control systems, clarification of prices and contracts, and labor shortages. Systems are needed to establish the remodeler's awareness of housing management as a professional business and to properly evaluate the asset value of houses.
We analyzed a questionnaire survey of urban detached house residents who had remodeled their houses, and obtained knowledge for housing policies on housing management. 1) Mechanisms for evaluating the effectiveness of performance improvement and good management conditions. There are many residents with low management awareness, but those with high awareness are in a virtuous cycle. 2) Building diagnosis at 30 years old. There are different issues after 30 years than before, and individual support is needed. 3) Certification and operation of experts in the management of detached houses, including relationships with remodeling contractors.
Compared to western countries, Japan still has a large number of new housing starts while vacant stocks have been increased over time. A possible explanation is that effective age of houses is short in housing market: existing housing stock becomes economically obsolete once new housing equipment emerge among newly built houses. Although reform and renovation take place to update part of the equipment, some may be difficult to be inserted through renewal, and thus, newly built houses play a crucial role to update housing quality to the contemporary needs.
The purpose of this paper is to measure (i) the degree of economic obsolescence of properties from lacking emerging housing equipment and (ii) effect of renewal activities on improving housing quality, price, and depreciation. To capture such a market mechanism, which has been ignored in architectural literature, we employ a novel dataset on resale transactions of detached houses in the Tokyo metropolitan area with details on their housing equipment and renewal activities.
First, we investigate relations between diffusion rate of housing equipment and renewal activity. For sanitary equipment, diffusion rate has been increased over time, and even for old houses, the equipment is inserted through renewal. For equipment relating to building structure, on the other hand, such a renewal adjustment is not so common.
Second, we investigate the degree of economic obsolescence from lacking emerging housing equipment, employing a hedonic regression technique. Old houses without the up-to-date housing equipment exhibit lower price premium among their age cohort, suggesting economic obsolescence.
Third, we investigate the effect of reform and renovation on property price and depreciation speed, through similar estimations. Although renewal activities are positively reflected in transaction price for old houses, renovation that fundamentally update the quality of a house rarely occurs. Alternatively, make-up inner-reform is common, which is unable to slow down depreciation.
Fourth, subsample analyses are conducted on the locational heterogeneity within the Tokyo metropolitan area. In outer suburbs (far away from the center), diffusion rate of housing equipment tends to be low, renovation rarely takes place, and most of the renewal activities remain to be make-up inner reform. Therefore, the economic obsolescence from lacking sanitary equipment and depreciation tend to be severe, while renewal, if taken place, has a large effect on slowing these down.
The above results imply that old houses face a mismatch between their poor housing equipment and contemporary needs for living, and that reconstruction may play a role to fundamentally update the housing quality because of the difficulty in updating through renewal.
This research is based on the questionnaire survey of residents in remodeled detached houses that were built after 1981. Analyzing satisfaction and implementation details in terms of two aspects – different cost ranges of remodeling, and whether the remodeling projects had been carried out with / without enhanced thermal insulation – we found the following points.
First, from the analysis of difference according the cost ranges, three points become clear: 1) regardless of the cost ranges, many respondents carried out remodeling triggered by “turning point of repairing” or “aged deterioration or breakdown of facilities”, on the other hand, the percentage of people who triggered by “changes in family structure and life stage” grows in higher cost ranges; 2) remodeling contents are not often added to the initial considerations, but the final cost often exceeds the initial budget, especially for high-priced remodeling; 3) the group that carried out high-priced remodeling had been dissatisfied with the housing performance before the remodeling, and the importance at remodeling was high for many items of housing performance. Furthermore, after remodeling, the degree of satisfaction was increased. It is considered that they are realizing the improvement effect by remodeling.
Second, from the analysis of remodeling with / without enhanced thermal insulation, the three points become clear: 1) About 20% of the group that carried out enhanced thermal insulation added “enhancing heat insulation of windows or frames” to the initial considerations, based on their own requests during the process or on proposal from their contractor. The amount of cost increase compared to initial budget is also larger than the group that didn’t carry out enhanced thermal insulation; 2) the group that carried out enhanced thermal insulation had been dissatisfied with the thermal / energy performance before the remodeling, and the importance at remodeling was high. After remodeling, the degree of satisfaction was increased, especially in “warmth in winter”. It is considered that they are realizing the improvement of thermal environment by remodeling; 3) more than 20% of the group that didn’t carry out enhanced thermal insulation is eager to carry out “enhancing heat insulation of windows or frames” in the future. In addition, after remodeling, there are a certain number of respondents who are dissatisfied with thermal environment in winter, and we have concluded that their motivation of thermal insulation remodeling can be improved by appropriate suggestions.
In order to promote the implementation of thermal insulation remodeling in the future, an information provision method that encourages proactive proposals by contractors is necessary.
From case studies, we estimated repair costs of long-term dwelling houses and then examined how to manage and maintain the residence effectively. The average repair cost of the target houses is about 16,400yen/month, which would be a rough indication for house maintenance. Subsidy systems become effective incentives to improve the dwelling performance. To maintain and manage houses, long-term plans are important. At the time of periodic inspections and renovation, diagnosis and advice by experts such as architects are needed. Experts such as builders who related with residents continuously in small repairs are important, too.
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