Passive systems include building form and geometry, courtyards on south and north sides, small and large windows opening for natural ventilation, mechanically assisted fans for hybrid ventilation, water fountain in the south courtyard for evaporation effect, double-shell wall and roof systems, shading systems that use canvas, date palm tree shading screens, bio-green wall, and the greenery landscape that modifies the microclimate of the house. The passive systems have largely helped in reducing the impact of the outside aggressive and harsh hot climate on indoor environment. Since they consume energy and require continuous maintenance, installations of complementary active systems were minimized at the SQU Eco-house. Mini-split air conditioning systems are provided in each space for extreme control flexibility.
Mist Spray System
Evaporative cooling using mist spray has been known for reducing the ambient air in hot climates. Although Muscat’s climate is known to be humid in summer, evaporative cooling can potentially be used in some summer months. Mist spray system is proposed and installed in the east and west cavity areas inside the double shell wall and in the south and north courtyards. This system is intended to reduce the ambient air temperature through evaporation process.
Air conditioning (AC) Systems
The SQU Eco-house is divided into 10 thermal zones based on many factors such as the occupant’s activity, orientation, the level of system control. Each zone is equipped with 1.0 Ton split system except the family room at ground floor where 1.5 tons of air conditioning is used.
Using the free outside cooled air has an impact on thermal comfort, energy consumption and indoor air quality. The SQU Eco-house provides a variety of passive and active means for full harvesting of outside cooled air for cooling purposes, maintaining the thermal comfort and providing an acceptable indoor air quality.
The SQU’s Eco-house, natural ventilation can be achieved using windows and doors that are located in strategic locations. Cross natural ventilation is promoted due to differential pressure between windward and leeward sides that can be created by closing and opening windows and doors at ground and first floor. Lessons are learned from traditional Omani architecture in which natural ventilation was achieved by long vertical windows that contained lower openings to inlet.
Mechanically Assisted Ventilation
When the outside air can’t be driven naturally using passive means, the Eco-house has 5 ventilation fans on the first floor to promote air flow. These fans are mainly installed to drive the air flow in the family area located in the ground floor.
Water Fountain Heat Exchanger
Heat exchanger water fountain is located in South courtyard. It has a deep water reservoir that dissipates heat from water to deep soil. The cooled water is pumped up to the fountain to cool air that flows into lower inlets of the house.
External surfaces of buildings get heated due to the combination of air temperature and solar radiation. Conventional design concepts are to shade window to prevent sun rays from penetration through glass, while the concept double-shell system is to shade all the building. A secondary light shell wraps around the house providing full shade of all external surfaces (i.e., roof and walls). It intercepts solar radiation and removes its thermal load before it reaches the building. The outer shell must be of light weight material, and air currents in the interim space are maximized to avoid stagnation of hot air.
Artificial lighting Systems (LED)
LED lights are selected as a source of light. They are installed indoor and outdoor to minimize the power consumption, yet at higher lighting output.
Daylighting can better be introduced to the indoor space in a diffuse form. No shading is provided on north side of the house allowing the diffuse north light to enter the spaces on this side easily. On other sides of the house, the double skin façade of the SQU’s Eco-house is rationally designed to block all direct sunlight. The shading systems attached to the double skin façade (vertical, horizontal canvas, GRC screens, bio-wall, and date palm screens) allow the direct and diffuse light to penetrate into the south courtyard, east and west cavities.
BUILDING ACOUSTICAL SYSTEMS AND NOISE CONTROL
The Eco-house is designed with interior walls that are composed of 200 mm hollow block. In addition, thick wooden doors are used in interior spaces. Inside the rooms, wide closets are attached to the exterior walls providing another means for noise mitigation. Double skin façade in the SQU Eco-house is also a helpful design feature to mitigate the propagation of exterior noise. Climbing trees and the soft canvas on the exterior side of the double-shell can absorb significant amount of noise. In addition, the Eco-house is surrounded by a concrete block fence of a 2 m height. This fence is helpful to reduce the noise that comes from the nearby road. Tall trees are planted in the landscape of the Eco-house. These trees will absorb significant amount of noise that comes from exterior environment.