Green roofs and asset value

Rooftop and wall greening

1. Benefits of rooftop greening

The benefits of installing rooftop greenery to buildings are:

Prevents deterioration of the waterproof layer from ultraviolet rays and acid rain
Reduce deterioration caused by expansion and contraction of buildings
Preventing the spread of fire
Energy-saving effect

Such as it will be mentioned.
Furthermore, with recent redevelopment projects greening the rooftops and terrace spaces of large buildings, and real estate developers placing advertisements when selling condominiums, greenery has become an important option for increasing purchasing power. In addition to the application of the Urban Green Space Act and securing green space, emphasis is being placed on the ability of greenery to attract customers and to generate purchasing power, such as "green streets," "green living," and "health," and this is having a major impact on real estate value and rental income.

2. Rooftop greening and management

On the other hand, maintaining greenery is important and needs to be incorporated into long-term repair plans. The amount of greenery after construction and over time can vary greatly depending on the management method. At Ark Hills in Tokyo, it has been reported that the green coverage rate has increased from 23.3% to 42.1%, and the maintenance of greenery requires advice and estimates from experts. (Mori Building Co., Ltd. website:https://www.mori.co.jp/environment/urban_nature/coverage.html）
Furthermore, from the perspective of building preservation, maintaining waterproofing, cleaning drains, and inspecting and repairing equipment are essential, so when selecting a green roof system, it is important to select one that does not affect the waterproofing, and that is sustainable in terms of operating costs, such as one that is easy to remove during renovations and is recyclable.In particular, the selection of plants has a significant impact on management, so it is necessary to plan for plant growth over time, such as plantings that do not easily shed leaves and considering the use of underground supports to deal with fallen trees.
Furthermore, in light of recent trends such as carbon neutrality, environmental assessment of rooftop greening will require selecting a rooftop greening system that can be incorporated into the design layer from a management perspective.

3. Rooftop greening and service life

When considering rooftop greenery and asset value, the useful life of the rooftop greenery must also be taken into account.Rooftop greenery is classified as a "green facility" and is treated as a separate depreciable asset from the building.
"Greening facilities" refers to planted trees, lawns, etc. that are used for greening purposes as a whole, and also includes earthwork facilities such as sprinkler pipes and drainage ditches. In the case of rooftop greening, this also includes rooftop greening systems, root-resistant sheets, and secondary and subsequent irrigation equipment. The useful life is determined by the "Ministry Ordinance on the Useful Life of Depreciable Assets"

Factory greening facilities...7 years
Other green facilities...20 years

However, this period is the useful life under tax law, and it cannot be said that all greening facilities other than factories will last 20 years, so in reality it is important to consult with the rooftop greening manufacturer and draw up management and renovation plans.
In addition, with regard to fixed asset taxes on rooftop greenery, there are reduction measures in place from the national and local governments due to amendments to the Urban Green Space Conservation Act, so it is a good idea to consult with them.

4. Rooftop greening and asset value

As mentioned above, conservation and management plans will be implemented while taking into account the benefits of installing rooftop greenery. In addition to considering life cycle costs, investment in rooftop greenery also requires profit analysis, such as ROI.
ROI (Return On Investment) is an index used to measure the amount of profit generated in relation to the cost invested, and is an important index for increasing a company's profits. By systematically and strategically installing greenery in the common areas, rooftop greenery, and terraces of a building, users will feel "comfortable," staying longer and moving around the building, which will result in higher profits.
Namba Parks in Osaka has a large green area (5300 m²) is said to have increased the amount of purchases per user by 1 yen (*1223). Based on this figure, Nikkei Architecture estimates that "they are generating sales of 1 billion yen per year" (October 92, 2010 issue).
In this way, from the perspective of environmental assessment, CASBEE and the US LEED are used to rank environmental efforts, and the introduction of greenery increases social recognition as a way to attract customers. Also, as a corporate green space, with the recent trend of SDGs and ESG investment, creating high-quality green space is expected to have the effect of communicating to society and improving the company's image.

(*1 Survey conducted in 2009 by Shinji Kato, Senior Researcher at the Building Research Institute. Currently a professor at Tokyo Metropolitan University)