Vertical greening systems: social and private benefits and costs

Transcription

1 1 ST INTERNATIONAL CONFERENCE ON GREEN WALL September 4-5, 2014 Vertical greening systems: social and private benefits and costs Katia Perini, Paolo Rosasco Department of Architectural Science, University of Genoa (Italy)

2 Integration of vegetation in contemporary architecture to restore the environmental integrity of urban areas Several resarches determined economic costs and benefits of green roofs Can vertical greening systems systems be economically sustainable? Cost Benefit Analysis of green façades and living wall systems Installation, maintenance, and disposal costs compared with private and social benefits determining: Net Present Value (NPV) and Pay Back Period (PBP). Keywords: Green façade, living wall system, Cost benefit analysis, Life cycle costs, Economic sustainability, Social and personal benefits.

3 Vertical greening systems and cases analyzed 1. direct green façade 2. indirect green façade 3. indirect green façade 4. living wall system with a well grown with a well grown combined with HDPE based on a mat with an Hedera helix Hedera helix planter boxes with a aggregate mix and two supported by: well grown Hedera helix layers of geotextile A. plastic mesh (HDPE) supported by: B: steel mesh A: plastic mesh (HDPE) B: steel mesh

4 Virtual building located in Genoa, Italy (Mediterranean climate). four floors office building designed according to the local regulation and considering the most common characteristics and technologies: windows surface is 1/8 of total floor surface 2 façades surface: 225 m building envelope: double brick wall with air cavity and mineral wall (8 cm) Service life: 50 years

5 Personal costs Installation costs direct green façade: climbing plants (22 /meter) + dig at the base of the façade (520 /meter) indirect greening systems: climbing plants (22 /meter) + dig at the base of the façade (520 /meter) HDPE supporting system 36 /m 2 + installation 2 steel mesh 94 /m + installation indirect greening systems combined with planter boxes HDPE 100 /m 2 + irrigation and installation 2 steel 180 /m + irrigation and installation living wall system: 200 /m 2 + irrigation and installation Maintenance costs all the greening systems: pruning every year indirect greening system with planter boxes and LWS: water pipes + plant species substitution LWS: panels replacement Disposal costs systems disposal and cladding (plaster) renewal.

6 Personal benefits Property value vertical green is relevant to 3 real estate features determining the value of a property: building related to typology and aesthetic of the building pollution related to level of noise and air pollution perceptible inside the building green related to the presence of green Increases in annual rent 3-5% Energy saving simulation model - Termo Microsoftware energy saving for air conditioning: 10-20% ( /year; Ottelé, 2011; Mazzali et al., 2012) energy saving for heating: % ( /year; Perini et al., 2011) Longevity Vertical greening systems reduce the frequency of maintenance (from 35 to 50 years) + lower cost at the 50th year due to a better condition of the plaster (NOT for direct green façade) Tax reduction QUALITATIVE. incentives not provided in Italy All these benefits have been calculated depending on the plants growing speed, e.g. for the direct and indirect greening systems the benefits are calculated after 10 years from the installation.

7 Social (costs) and benefits The positive environmental effects of vertical greening systems have been considered in terms of costs savings for the society Air quality improvement The remove value assumed for vertical green is equal to 50% of the remove value assumed (Currie and Bass, 2008) for green roofs. Considering the nitrogen oxide (NOx) emission credit, NOx absorption results in a benefit for air -3-3 /m 2 /year. Carbon reduction Considering the carbon reduction tax as 20$/ton (Kyoto Protocol) the annual benefit in carbon reduction -3-3 /m 2 /year. Habitat creation QUALITATIVE. Not a common investment in many cities Aesthetic impact QUALITATIVE. Difficulty to assign a value to the positive impact of vegetation Urban heat island mitigation QUALITATIVE. Difficulty to estimate the effect of a single green façade Tax incentives QUALITATIVE

8 CBA Results Personal and social economic benefits considered, with a very small impact of social benefits. Scenarios: best, middle and worst. x A 2B 3A 3B Worst Middle Best 1. Direct green façade sustainable for all the scenarios assumed. 2A. Indirect green façade with HPDE mesh sustainable for middle and best scenarios. Net Present Value (NPV), i.e. the discounted value of the sum of costs and benefits that occur within the period of life considered. Economic sustainability is reached when the NPV is positive 2B. Indirect green façade with steel mesh sustainable for best scenarios. 3A. Indirect green façade with HDPE planter boxes minimum economic sustainability in the best scenario. 3B. Indirect green façade with steel planter boxes minimum economic sustainability in the best scenario. Type of green facade 1 2A 2B 3A 3B 4 Pay back period (PBP) (number of years) Worst Middle Best > >50 >50 16 >50 >50 >50 4. Living wall system not economically sustainable Pay Back Period (PBP), i.e. the number of years from which the total revenue equals for the first time the total costs.

9 Conclusions Vertical greening systems provide personal and social benefits. Installation and maintenance services costs play a fundamental role on the economic sustainability. For some of the systems analysed in this study the benefits can not pay back the costs. The most relevant benefits calculated in this CBA are connected with the real estate and the energy savings for air conditioning. Social benefits have a very small influence on the CBA, since only the benefits connected to air quality improvement and carbon reduction have been quantified. However also the benefits mainly related to macro scale can be considered as additional social benefits. Economic incentives (tax reduction) could reduce personal initial cost allowing a wider diffusion of greening systems to reduce environmental issues in dense urban areas. Perini K., Rosasco P., Cost Benefit Analysis for green façades and living wall systems. Building and Environment 70 (2013) Imprint: ELSEVIER.