2.1. The SOLENE-Microclimat Model
- LW radiation exchanges using the radiosity method;
- conduction heat transfer and thermal storage in walls and soil;
- airflow and convective exchanges through the coupling with a computational fluid dynamics (CFD) code.
- Evapotranspiration, i.e., latent heat flux due to transpiration and evaporation of water contained in both the plants and substrate.
- Radiation: the foliage layer modifies both short-wave (SW) and LW radiation; moreover, it reflects, absorbs and transmits a portion of the SW radiation to the shaded surface area. In covering the surface, this layer exchanges LW radiation with the surrounding surfaces, as well as with the surface being covered.
- Convection: the foliage layer is rough and modifies the near surface airflow, thus implying a modification to the heat transfer.
2.2. The Studied Urban District
2.3. The Studied Building
- constant air change rate: Qr = 0.3 vol·h−1;
- constant indoor heat gain: 30 kW.
2.4. Greening Scenario
- architectural greening: green roofs and walls;
- sustainable urban drainage systems using vegetation;
- vegetation in deep soil vs. a soilless culture.
- their management: extensive vs. intensive;
- their spatial distribution (city, district or building).
- foliar density: leaf area index (LAI) = 2;
- thickness: L = 0.2 m;
- extinction coefficient: ks = 0.8;
- transmissivity: τf = 0.2;
- an irrigation equal to potential evaporation (PTEc).
2.5. Adaptive Comfort
- high expectations, used solely for spaces occupied by very sensitive and fragile individuals;
- normal expectations, used for new buildings and renovated spaces;
- moderate expectations, used for existing buildings;
- expectation level for buildings outside the first 3 category levels. It is suggested that this category should be used for just a short period of the year.
3.1. Weather Conditions
- outdoor temperature (sensors/Vaisala HMP45C-L, Campbell Scientific, Logan, UT, USA);
- solar radiation (pyranometer Skye SKS 1110, Environmental Measurements Limited, North Shields, UK);
- infrared atmospheric flux (pyrgeometer Kipp&Zonen CGR3, Kipp & Zonen, Delft, The Netherlands);
- wind velocity and direction (wind monitor Young 05103, Young, Traverse City, MI, USA);
3.2. The Targeted Greening Strategies
- separating direct from indirect effects of the green envelopes;
- comparing the disposal rates.
- facades of the studied building;
- roof on the studied building;
- facades of the other buildings;
- roofs on the other buildings;
- the soil.
- the reference case, without vegetation, or Case (0);
- Cases (1)–(3) are dedicated to assessing the direct effects (only the surfaces on the studied building are greened), with Case (1) being the facades, Case (2) being the roof and Case (3) being both facades and roof;
- Cases (4)–(7) consider just the indirect effects of greening, with Case (4) focusing on the facades, Case (5) focusing on the roofs and Case (6) focusing on the lawns; both the facades and soil are greened in Case (7);
- In Case (8), the entire envelop of the studied building is covered with vegetation, as are the other buildings;
- Cases (0+), (3+), (4+) and (8+) are similar to Cases (0), (3), (4) and (8), respectively, yet with an insulated building; for this insulated building, 10 cm of mineral wool have been added to the internal surface of three walls and the roof.
|Effect||Reference||Direct||Indirect||Direct + indirect|
|Greening of the vicinity||Facades||-||-||-||-||-||-||X||X||-||-||X||X||X|
|+: with an insulated building||-||X||-||-||-||X||-||X||-||-||-||-||X|
- Perspective 1, the effects of vegetation on the thermal insulation level: Cases (0), (3), (4) and (8) for the non-insulated building and Cases (0+), (3+), (4+) and (8+) for the insulated building;
- Perspective 2, comparison of the direct and indirect effects from green walls: Cases (0), (3), (4) and (8);
- Perspective 3, study of the direct effects of green envelopes: Cases (0)–(3);
- Perspective 4, study of the indirect effects of urban green surfaces: Cases (4)–(7).
4.1. Perspective 1: Impact of Green Surfaces on the Thermal Insulation Level
4.2. Perspective 2: Comparison of Direct and Indirect Effects of Green Facades
- the reference case, i.e., without vegetation (0);
- green facades on just the studied building (3);
- green facades on the surrounding buildings, but not on the studied one (4);
- green facades on both the surrounding buildings and the studied one (8).
4.2.1. Indoor Air Temperature
4.2.2. Indoor Thermal Comfort
4.2.3. Water Balance
|Configuration||Total Quantity (L)||Footprint (m2)||Total Height of Evaporated Water (mm·m−2)||Evaporation Ratio (%)|
|Green walls on the studied building||2594||954||2.72||177|
|Green roof on the studied building||1723||954||1.80||118|
|Green walls and roof on the studied building||4317||954||4.53||195|
|Green walls in the urban environment||18,527||8012||2.31||151|
4.3. Perspective 3: Direct Effect of Green Envelopes
4.3.1. Variation of Temperature Inside the Building
- building without any vegetation;
- building with a green roof and green facades;
- an insulated building without vegetation.
4.3.2. Thermal Fluxes at the External Building Surface
4.4. Perspective 4: Indirect Effects of Vegetation
- To what extent do green roofs modify air temperature in the district and affect the thermal behavior of surrounding buildings?
- What are the impacts of lawns and green walls on the thermal behavior of surrounding buildings?
- Are the direct and indirect effects of these techniques comparable? In particular, what is the predominant effect: convective or radiative?
- the reference case, without vegetation (0);
- a green roof on the studied building (2);
- lawns on the uncovered ground (6);
- lawns and green facades on the studied building and surrounding buildings, (7) + (3).
4.4.1. Indoor Thermal Comfort
- The effect of green roofs is practically negligible;
- The effect of lawns and green walls leads to a decrease in indoor temperature, ranging from 1 °C to 2 °C. This difference slowly varied during the week, with some differences appearing between the configurations after 28 June.
4.4.2. Convective and Radiative Heat Fluxes
5. Discussion and Conclusions
Conflicts of Interest
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