Green Roofs - Living Architecture Monitor - Winter 2010 - (Page 26)

RESEARCH CURB APPPEAL By Ray Tomalty & Bartek Komorowski NEW RESEARCH EXPLORES WAYS TO VALUE GREEN ROOFS BY ESTIMATING THEIR IMPACT ON PROPERTY VALUES This article is drawn from a report prepared by the authors for the Canada Mortgage and Housing Corporation (CMHC), entitled The Monetary Value of the Soft Benefits of Green Roofs. The report, created with support from Green Roofs for Healthy Cities, developed methods for estimating those benefits that are often ignored when evaluating the impact of green roofs because of difficulties in measuring them. This article focuses on one of the seven benefits covered in the report, increased property values. reen infrastructure investments have been shown to positively affect the property value and marketability of nearby real estate. In the case of green roofs, this benefit accrues to the owner or owners of a building with a green roof and, to a lesser degree, to owners of surrounding properties. Selling prices for properties with various features can be used to estimate the value of those features. Such techniques (called hedonic valuation) have been used to measure the relationship between the selling price of a residence and its distance from an urban green space, park, community garden or wetland. For example, a home abutting on a park is usually considered to be worth more than an identical home without the park amenity. At present, there are no studies that have measured the potential of green roofs to increase the value of residential units in the same building or with a view onto the amenity. In the absence of hedonic pricing studies looking specifically at green roofs, we can use estimates of property value increases generated by other types of green infrastructure, e.g., an at-grade community garden or park. RECREATIONAL ROOFTOP GARDEN Assuming that having a recreational rooftop garden is tantamount to abutting an at-grade park, we propose that the value of the benefit accrued to the owner(s) of the building be estimated at 20 percent of the value of the property. This is based on Crompton’s (2005) suggestion of using 20 percent as the rule of thumb for the increased LIVING ARCHITECTURE MONITOR G value for properties abutting parks. We propose the increase in property value yielded by a recreational rooftop garden be estimated using the following formula: b = 0.2 • v WHERE: b = value of the benefit ($) v = value of the green roof host property ($) PRODUCTIVE ROOFTOP GARDEN Assuming that having a productive rooftop garden is tantamount to abutting an at-grade community garden, we propose that the value of the long-term benefit accrued to the owner of the property be estimated at seven percent of the value of the property. This is based on Voicu and Been’s (2008) finding that, on average, properties abutting typical community gardens increased in value by 7.4 percent within five years of the construction of the garden. As we do not know from these findings what the effect is in the longer term, we assume the value remains constant at the five-year level. We propose the increase in property value yielded by a private, productive rooftop garden be estimated using the following formula: If the productive rooftop garden is open to non-occupants of the building then it is likely that benefits will accrue to owners of neighboring properties. In this case, we assume that the rooftop garden behaves exactly like an at-grade community garden. In the long-term, the value of the benefit accrued to neighboring property owners is seven percent for owners in the building with the rooftop community garden and the immediate vicinity of the host building, five percent for those up to 500 feet away, and two percent for those up to 1,000 feet away. Again, the values are based on Voicu and Been (2008) and assumed to hold at their five-year level. We propose the increase in property value accrued to a neighboring property of a publicly accessible productive rooftop garden be estimated using the following formula: b=F•v WHERE: b = value of benefit ($) v = property value ($) d = distance from green roof host property (meters) F = distance factor (function of d) LET: F = 0.07 when 0 ≤ d ≤ 5 m F = 0.05 when 5 m < d ≤ 50 m F = 0.02 when 150 m 300 m b = 0.07 • v WHERE: b = value of the benefit ($) v = value of the green roof host property ($) WINTER 2010

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Winter 2010

Green Roofs - Living Architecture Monitor - Winter 2010
Contents
Laying Roots for Green Jobs
Outstanding Student Design
Passing of a Legend
New Federal Stormwater Guidelines From EPA
Partnering Science with Service
On the Roof with...Eden Brukman, Reg. Arch., LEED(R) AP
The Leaf Effect
Who Owns the Green Roof?
Planting the Federal Inventory
Curb Appeal
Maintenance Matters
Professional Development Update
Professional Calendar
Congratulations New GRPS
Welcome New Corporate Members
Green Roof Energy Calculator
Doing No Harm

Green Roofs - Living Architecture Monitor - Winter 2010