Engineering a net positive energy building

A330 Multi-Role Tanker Transport Hangar

The Republic of Singapore Air Force (RSAF) has unveiled the A330 Multi-Role Tanker Transport (MRTT) hangar which took two years to build and was completed in March 2020. This A330 MRTT Hangar is the RSAF’s first net positive energy building and can generate 30% more electricity than consumed.

As the Civil & Structural (C&S) Engineer, KTP Consultants, a member of Surbana Jurong Group, employed a sophisticated and robust structural system for the project. Kevin Nair, KTP’s Senior Executive Engineer (C&S), who worked on the project from conceptualisation to completion, shares some insights.

• To achieve a clear span of up to 90m and commit to the lower tonnage of the roof, KTP employed a modular steel truss system supported on laced strut columns. This allowed KTP to have a large column-free span without compromising the robustness of the building.
• During the erection, working space and height were constrained by adjacent buildings as well as restrictions by the Civil Aviation Authority of Singapore. As it was not feasible to mobilise the tower crane, KTP worked closely with the main contractor and jacking specialist to use their proprietary strand jacking system to lift the entire roof from three meters above ground to its final height of about 30 meters in less than two days.
• The hangar also comes with a paneled fabric door installed with translucent material that allows sunlight to permeate through, reducing the need for excessive lighting. The large front opening to accommodate the fabric door support posed a challenge to the lateral stability on the building’s minor axis. KTP had to work around the available space within the fabric door support to employ a truss rigid enough to resist the lateral force.

KTP’s engineering solutions contributed to the project attaining the Building and Construction Authority Green Mark Platinum (Positive Energy) Award.

Sustainable Features

Solar panels installed on its roof will generate 1,225,000 kilowatt-hours of electricity a year – enough to power 273 four-room HDB flats. The additional energy will be directed to other facilities within Changi Air Base (East) where the hangar is located.

The building is positioned in a north-south orientation to optimise airflow for natural ventilation. The building was also designed to maximise natural ventilation to create a cool working environment for the maintenance crew. This was achieved by the large front door opening with panelled vertical lift fabric door, and large-span louvres at the rear of the hangar. This means the hangar does not need to have as many fans, reducing the energy it consumes.

Large-span louvres allow for natural ventilation

The office annex attached to the hangar also has a green roof with carpet grass that insulates the building against heat. The moist soil under the grass acts as an insulation layer against the heat, reducing the need for excessive air-conditioning in the rooms. The LED lighting and air-conditioning used are also energy efficient.

The MRTT hangar features a green roof which acts as an insulation layer to keep the hangar cool.

Rainwater is harvested and recycled for general washing, flushing of toilets and auto-irrigation of the hangar’s green roof. MINDEF estimates that, together with water-efficient fittings, the building will save an amount of water equivalent to the consumption of 28 four-room HDB households each year.

The A330 MRTT hangar, located in Changi Air Base, is equipped with rainwater harvesting features (water tank in foreground).

Watch this video to view the building’s sustainable features.

Credits for all images: MINDEF, Singapore