A series of levels throughout the scheme make use of the natural gradient of the site to identify a hierarchy of private and public spaces. The levels echo the terraced landscape of its immediate context. These levels and the tower provide key features for the natural ventilation strategy, described in section 3.5.

The shift of the residential block off the orthogonal axis softens the formality of the courtyard, and leans it towards the contours of the site. The arrangement of the buildings avoids all but two of the existing trees in an effort not to disturb their fragile ecological context.

The approach to sustainability, described in more detail in section 2, has three driving principles:

1. Minimise energy demand.
2. Provide energy from low-impact, reliable, easily available sources.
3. Keep it low-tech and simple.

The scheme further aims to sympathise with its locale through the materials used. A material datum at first floor level provides a plinth of indigenous stone emerging from the hillside, above which locally sourced adobe, reinforced with cement, forms the upper levels. These materials, whilst key to the architecture, also lend themselves to the functional intentions of the scheme, helping provide a heavyweight building which assists the passive design. Landslide protection is provided by soil-filled steel drums; a simple technology that recycles locally-available material.

2. Sustainability Statement

The building is designed with this strategy:

1. Minimise energy demand.
2. Provide energy from low-impact, reliable, easily available sources.
3. Keep it low-tech and simple.

2.1 Minimising energy demand

All through the year the external environment is capable of supplying useful free energy to a building in the form of light, heat, and coolth. The building skin is used as a filter or moderator of free energy exchange between the internal and the external environment, thus reducing the overall energy needs of the building.

Summer: The window orientation is designed to minimise summer solar gain. The building will be constructed with an exposed high thermal-mass structure. An undergound air inlet further increases the thermal inertia of the building. Secure and weatherproof ventilation openings at low and high level use the buoyancy of hot air to drive airflows that purge heat during a summer night. This will allow the structure to absorb heat through the day, which maintains cool internal conditions without mechanical cooling.

Winter: The external envelope is highly thermally resistant, and is well sealed to minimise heat loss by air infiltration. A trombe wall collects & stores winter solar radiation. The warm air off the computer server is passed around the building. The casual gains from people and equipment bring the rooms upto comfortable temperature without the need for active heating. A small wood burning stove is provided for rare extreme cold snaps.

All lighting is low energy fluorescent, which is commonly available in Nepal.

2.2 Provide energy from low-impact, reliable, easily available sources.

Cooling: No mechanical cooling is required.

Heat: Wood is easily available, but it is a resource under strain in Nepal. The minimal space heating is provided by a wood burning stove. Hot water is provided by solar thermal panels on the roof. Solar thermal panels can be constructed by local builders.

Electricity: The client has already purchased a generator so it is sensible to use this when grid electricity is not available. On the Hub site, wind turbines or PV panels will not provide enough electricity to justify their cost. The WiFi repeater stations have a very low power demand, so PV panels are suitable here.

2.3 Keep it low-tech and simple

Construction: The building and its services are constructed from locally available materials and constructed using tried-and-tested methods to a durable quality finish. It will therefore be cheap to build and easy to maintain. The high technology is limited to the ICT systems.

In use: Air flows into, out of and around the building are controlled simply by opening and closing shutters. The trombe wall is again controlled by opening shutters. The arrangement of the solar thermal panels and thermal store will negate the need for a pump. The woodburning stoves, diesel generator & rainwater storage systems are all commonplace in Nepal so maintenance will be simple.

3. Outline of services

3.1 Drainage

Image 1740_supplementalimage_3 illustrates the drainage strategy. Monsoon rainfall runs off the roof into large tanks just uphill from the centre. This provides the centre with water throughout the year. Overflow is directed away from the centre to a soakaway. Drains from the kitchen and bathrooms run to a small reed bed, and then to the soakaway. The latrines are the Ventilated Improved Pit (VIP) type: these are ventilated using direct solar energy; waste is stored in a pit below from where the liquid filters directly into the ground and the solid waste is removed by hand after about a year, once it has become inert. This design gives hygenic control of waste and odour without requiring energy or water.

3.2 Water services

A gravity-fed system provides water from the uphill rainwater storage tanks, through sand filters, to serve the accommodation block and the latrines. The tanks are insulated and shaded from the sun. Hot water is heated by locally constructed solar thermal panels, made from copper or UPVC pipes painted black and mounted on the roof of the accommodation block in a glass-fronted box. The panels are orientated due south and tilted at 30º for maximum solar potential. A pipe connection runs to a large insulated cylinder up the hill. The hot water in the panels flows, by convection, up to the store; a pump is not required. When there is insufficient sun, hot water is heated on the stove.

3.3 Space Heating

The highly insulating building fabric, coupled with optimised use of internal and solar gains minimises the additional space heating required. In the computer lab block, heat is drawn from the server and IT rooms into the adjacent occupied spaces in winter. The accommodation block is orientated to maximise the passive solar gain. A trombe wall on the south façade of the accommodation block stores heat from solar gain during the day, and releases it at night, the main time when the block is occupied. In particularly cold weather, wood-burning stoves in the community room and the kitchen supplement the internal and solar gains to maintain comfortable internal temperatures in each block. The rooms in the third block are glazed to benefit from passive solar gain in the winter months; as these spaces are not regularly occupied there is no supplementary heating provision.

3.4 Cooling

The heavyweight building fabric, use of natural ventilation to reject heat at source and external shading to obscure summer sun allows comfortable internal temperatures without the use of mechanical cooling.

3.5 Ventilation

The sloping site and the transmitter tower allow key features of the natural ventilation strategy - underground air intake ducts and a ventilation stack - to be integrated neatly into the building form. Intake ventilation ducts run beneath the computer lab and accommodation blocks with large air inlets at the front of the building. Fresh air is supplied to each space by individual openings from the below ground duct. The transmitter tower forms a stack to collectively exhaust air from the computer lab block spaces. Air is exhausted from the rooms of the accommodation block by individual roof cowls. A separate upstand on the roof above the server room allows heat to be extracted directly from the servers in the summer without unnecessarily heating the adjacent occupied spaces. In winter this upstand is closed and the tower stack is used to draw warm air from the servers into the adjacent spaces. The rooms in the third block are individually naturally ventilated by low and high level openings in the façade. All ventilation openings comprise simple, insulated flaps that are adjusted manually.

3.6 Refrigeration

A space has been allotted in the third block to the north of the site to house the refrigerators. This room is built into the hill and is well shaded and insulated to ensure that energy required for refrigeration is minimised.

3.7 Electricity generation

Grid electricity is used when available. As a diesel generator has already been purchased, it is sensible to use this as the back up. The local wind speeds are not bountiful enough to provide cost effective wind-generated electricity for this building, whilst the cost of a solar photovoltaic (PV) installation would be prohibitive. Should further funding become available it is recommended that the installation of a micro-hydro turbine on a local fast-flowing stream is investigated as a means to supply the site with cost effective, renewable-based electricity. The WiFi repeater aerials have a low energy demand, so these are suitable for a small local PV panel and battery.

3.8 Small power & lighting

Electricity is provided to all three buildings. Fluorescent lighting is provided to all areas. Small power is provided only to the computer lab block, and to the consultation room in the third block.

3.9 Data and comms

Image 1740_supplementalimage_3 illustrates the data and comms strategy. Data flow is integral to the design of the telemedicine hub building. Internet connection to the hub is provided by CDMA signal. WiFi aerials are mounted on the chimney at 10m above ground level. A WiFi network is provided around the hub. A directional WiFi beam connects the hub to the clinic in the valley. This beam is of course earthquake, landslide and flood proof, unlike a telephone line. The WiFi connection is directed to repeater aerials across the valley. These aerials provide local WiFi connectivity for the community health workers (CHW) in remote villages. As the aerials are self-powering and have a battery pack, they can be used by the CHWs to recharge their laptops and voice-over-internet-protocol (VOIP) mobile phones. In this manner the CHWs can have a very wide range of access, and can remain in the field for long periods whilst still remaining in close contact with their colleagues at the hub and across the world.

4. MATERIALS USED

The different building elements are identified below, with the materials used:

4.1 Foundations: Concrete to the north, east and west perimeters as a retaining wall, to provide structural stability. Local stone build up elsewhere.

4.2 External walls: Local stone at ground floor, traditional mud blocks at first floor.

4.3 Internal walls: Local stone at ground floor, traditional mud blocks at first floor. Tiled walls to ceiling height in sanitary areas for ease of cleaning; lined with render and painted in other areas.

4.4 Internal floor - ground and upper levels: Locally sourced timber. Ceramic tile surface finish floors in sanitary areas for ease of cleaning; sanded smooth timber in other areas. Ground floor to be insulated with insulation batts on the underside.

4.5 Roof: Timber with natural wool insulation batts above and a tin top protective layer.

4.6 Insulation material: Natural wool insulation batts, using locally sourced sheep or yak wool.

4.7 Thermal mass elements in basement air intake: Water-filled containers will rest in the basement air intake.

4.8 External glazing: 6mm standard single glazing.

4.9 Window frames: Hardwood or treated timber, locally sourced.

4.10 Internal doors: Locally sourced timber.

4.11 External doors: Locally sourced hardwood or treated timber.

4.12 Landslide prevention structure: Soil filled steel drums, partially submerged.

4.13 Water pipe to connect to local supply: uPVC pipework.

4.14 Sewage storage: Stone soakaway tank.

4.15 Water storage tanks: uPVC water tanks.

4.16 External courtyard and steps: Local stone

4.17 Solar thermal panels: Copper or uPVC pipework, painted black, in a glass-fronted box: no moving parts