Outside grounds work to improve comfort in summer.

Principle

Well landscaped grounds can limit heat gains in summer and reduce air conditioning needs by 20 to 100% at your hotel. Planting deciduous trees on the south-western and south-eastern sides of your hotel, for example, will reduce the need for air conditioning, and help maintain comfortable temperatures indoors.
Local shrub species can also be planted, or open-air basins and fountains created for the benefits of cooling by evaporation. The treatment of soils around the hotel also plays a significant role in summertime comfort.

Explanations

Leafy trees: intelligent sun protection in summer
• Well placed leafy trees will shade your building and help keep your hotel cool in summer. Another positive aspect is that the leaves fall in winter, and the building receives the sun from the east, south and west.
Planted walls: a solution to reduce heat in walls in summer (by as much as 10°C)
• In summer hot walls cause indoor building temperature to rise, increasing the need for air conditioning, and thus energy consumption. When walls are covered with moist soil and plants the surface temperature can be reduced by as much as 10°C, reducing the need for air conditioning inside the building.
Green roofs: a solution for thermal insulation that considerably reduces heat gain in summer
• Green roofs are also an option: they act as exterior insulation (in summer and in winter), and procure greater cooling than planted walls in summer. The insulating effect increases with humidity.
Plants and trees: many benefits.
• Plants and trees provide not only shade, they also provide cooling by evapotranspiration, eliminating heat by evaporation of water in leaves.
• Green spaces reduce the heat island effect and improve air quality.
• Plants and trees are major carbon sinks, and mitigate global climate change.
• Planting trees and shrubs to shade the exterior components of your air conditioning system can increase efficiency by as much as 10%. But be careful not to block air circulation around the equipment.
Vegetation around the hotel is also important.
• Plant cover in the area around the hotel affects heat radiation and reflection onto windows and walls. It is best to choose vegetation that prevents reverberation from the ground and keeps the soil cool, preventing re-emission of radiative heat. If grounds are pave on the south side of the hotel, for instance, permeable materials are recommended, or light-coloured permeable concrete. You can also plant trees and shrubs to shade the pavement, or cover it with wood.
Open-air water basins and fountains: cooling by evaporation
• Basins and fountains can increase summer comfort in the areas around the building. To obtain a cooling effect the water should be moving, as the mixture of air and water increases evaporation.
• The cooling potential of a fountain depends on the ambient conditions. Fountains on the north side of building walls are shaded from the sun, and will produce a greater cooling effect.

How should plants and trees be chosen?
• Plants require varying levels of care. Choose varieties that need little water and care, and will withstand the climate conditions in your location.
• Get advice from a local garden shop or landscape professional on trees and plants that grow well in your region, but do not require large amounts of water or other resources.
Where should trees be planted?
• Remember that reducing heat gains through the roof, and through east/west walls, calls for two different approaches!
• Do not plant trees due south of the hotel building, but rather to the south-west or the south-east. Even when their leaves have fallen, the bare branches of mature deciduous trees can block sun to your south-facing windows, and limit natural heat gains in winter.
• Procuring shade for your roof or using planted walls will have a greater cooler effect than installing sunshades on windows. Plant trees that grow tall with wide-spreading branches, to the south-east or south-west of the hotel building, so that the roof will be shaded when the trees are mature. Trees with branches closer to the ground are better for western exposures, where they will block sun at the end of the day.
• Landscape professionals can advise you on the best places for planting trees and obtaining optimal energy benefits.
What plants should be chosen for green walls?
• The plants used for green walls should not block the sun's heat in winter; recommended species are those with leaves that grow late in the spring, and fall early in the autumn.
• The efficiency of planted walls depends on the local climate and solar irradiation of the walls; it is best to consult a professional.
What sort of green roof should be chosen?
• There are two types of green roof, extensive or intensive. Extensive green roofs are the simpler solution; they require less soil and care. They are better suited to hotels.
• Given the complex requirements of green roofs, it is best to consult a professional.

Implementation

Costs

Approximate cost:
• Depends on the type of work.
• Extensive green roof ≈ €100/m² (installed)
• Intensive green roof ≈ €200/m² (installed)
Approximate payback time:
• Landscaping: can be under 8 years.
It should be noted that costs and payback times are highly dependent on the local setting and the initial situation of the hotel.

Examples

Benefits

Cost savings
Energy savings:
• Well landscaped grounds help keep buildings cool in summer, reducing the need for air conditioning in the hotel.

Comfort improvement
Greater comfort in summer:
• Planting trees will improve comfort in summer and help keep the building cool, reducing the need for air conditioning (which does not always offer the most comfortable form of cooling).
• Your customers will also appreciate walking under the trees in summer and will be happy to sit and relax outside.

Reduced CO2 emissions
• For a hotel of 1,000 m² that uses 37.5 kWh/m² of natural gas for cooling annually, and applying emission factors for France, a 30% savings in energy consumption represents:
0.63 t CO2 eq of avoided emissions each year
Emission factors for electricity in France: 84.3 g CO2 / kWh.
Emission factors for natural gas in France: 331 g CO2 / kWh (Source: ADEME).

Constraints

Implementation:
• Ease of implementation: Moderate (**).
• Best time for implementation: when work is planned on the grounds.
• Relevant initial situation: the hotel must be cooled in summer, and has private grounds.