By AOS Consulting Engineers
This prestigious hotel development won the Best Sustainable Project Award for the best project in Africa in 2016.
Based on the mechanical services implemented, the development was selected as the winner for the work completed on the building now named Ubumwe Grande Hotel of Umubano Industries Ltd, a 12-story high-rise building in Kigali, Rwanda.
AOS Consulting Engineers, in association with EES and a local partner Multikonsults provided the professional MEP engineering services for the development.
All performance criteria were agreed upon by role players for the defining of the project and various conceptual considerations were evaluated, as well as techno-commercial analysis conducted to motivate the selection of all technologies to the project.
The project, which included a hotel, retail and commercial facilities comprising 16 levels in total, required the provision of:
- a multi-level car park
- retail and conference spaces
- multi-levels of hotel suites (~134 guest rooms and 19 apartments)
- rooftop gym, swimming pool, kitchen, and outdoor dining areas
- service and general common areas
- external landscaping
The overall construction area is approximately 18 600m2 and the building is approximately 45m high. The development comprises of two basement levels, a lower-ground level, ground to 11th floor and rooftop gym, pool, and dining facilities on the 12th floor.
The requirements of this project were that the development be delivered to international standards incorporating best practice specifications, due attention to human safety, as well as energy efficient design.
Systems and technologies to be utilised should be “tried and tested” and applicable to the project location.
Serviceability and availability of technologies implemented needed to be considered and incorporated into the engineering services design and the development therefore needed to be designed in accordance with sustainability principles (but would not be sustainability-rated).
Specifications also needed to take under consideration productivity and health improvement through enhanced internal environmental quality (IEQ).
The choice of system was determined by the need for detailed recovery of air conditioning costs and the level of service desired. A comparison of chilled water, VRV, water source and tempered ventilation was proposed to the client. Tempered fresh air and chilled water only was recommended to meet requirements due to efficiency and reliability, and therefore the selected HVAC system for this project was a chilled water system that incorporated ducted fan coil units and a low profile air handling system. This selection met the technology criteria for each zone of the project.
- The scope of HVAC engineering services then included delivery of the following:
- Air conditioning to all hotel suites, retail zones, offices and client circulation areas (excluding the atrium).
- Fresh air to all occupied zones at a rate of approximately 7.5 litres per second per person.
- Extraction from all WCs, laundry, kitchen and change facilities.
- Mixed mode ventilation of the parking garage areas.
- Stair pressurisation to fire escapes as well as smoke ventilation to the atrium and all other areas over 500m2.
- For this project no heating provision was made as it was clear through simulations conducted and international weather data that it would not be needed.
- Tempered fresh air ventilation only was deemed acceptable for all of the back of house areas.
The system was designed using a central plant in a redundant arrangement; two-off chillers at 66% capacity each, and two-off pumps at 66% capacity each.
Heat recovery chillers were used to enable efficient heat recovery, while variable speed drives on pumps (with manual bypass) were installed for reliability and efficiency. The manual bypasses provided would maximise operator usability and ensure robustness of the design.
Conditioning via above ceiling hideaway units with ducted discharge and diffusers was used as far as possible. The project did not make use of cassettes, midwall or split units, as well as conventional air handling units were avoided to maximise all useable area.
Fan coils were ordered complete with valve and control packages to simplify site installation works. Air diffusion included linear diffusers in high visibility areas, swirl diffusers in offices, and typical round disk and square plated diffusers in general areas. All air diffusion units were electro-galvanised steel or aluminium and were lay-in grilles for ease of replacement and ceiling access when required.
The chiller heat recovery was used to incorporate into the hot water generation system where a heat pump was selected as the optimum choice to meet compliance and space requirements, as well as overall cost of ownership formulated into cost per unit. For the project, energy efficiency interventions in water heating were essential in order to reduce operational costs and improve overall sustainability performance.
Other incorporated services to the project
The scope of plumbing and drainage engineering services above the water heating then included the provision of the water storage at 14 500 litres which equated to approximately 4 days of supply, a water filtration and treatment system of chlorination/UV treatment of stored water (and filtration of incoming water to the site), supply and waste reticulation, and on-site sewerage treatment plant.
The project also included the supply of several electronics engineering services. This provision included the below items:
BMS & security systems – operated by centralised supervisory, control, automation, decision and alarming capability all provided by a network accessible building management system. This system is security and HVAC dominated.
Server and data provisions, the electronics engineers also co-ordinated the building provisions to ensure data reliability and suitability throughout the development, conference and office requirements were anticipated and provided.
Fire detection, smoke, rate of heat rise, and beam detectors were utilised to quickly detect and alarm fire conditions. The quick alarming and actioning of fire scenarios is key to the maintenance of the building in event of fire.
A public address and audio-visual system (fire rated) was installed to enable full audio control of the site.
A security room, control room and data centre would be the hub of monitoring for all services.
Dual redundant dedicated air conditioning was provided via heat pump splits.
Fire engineering services were also included in the project that comprised hydrants and hose reels to the full coverage of the building with 30m length reels, one hydrant per 1000m2 (90m coverage), sprinkler system as the building is over 30m in height the US, British and South African standards thus require sprinklers, water storage and pumping including controls thereof, and fire protection equipment.
The fire system bulk plant allocations for this project, located below the car park ramp and in adjacent parking at level B2, included the sprinkler tank (sectional steel/concrete) with a 196 000 litre (partitioned) capacity, hydrant & hose reel tank (sectional steel/concrete) with a 25 000 litre (partitioned) capacity, and a valve chamber 1m x 5m.