Moxon Street

 

Reduction, Not Production :

Sustainability lies at the core of this building, but rather than relying on the 'eco-bling' of energy-production products such as expensive photovoltaic panels, it concentrates more on energy-reduction through a holistic integration of design, materials and services. It is an attempt to showcase the subtle balances required in the design of truly sustainable buildings – airtightness vs indoor air quality; solar gain vs overheating; natural daylighting vs glare; high performance materials vs embodied energy...

Moxon Street Postgraduate College and Nursery

Form :

The form arises largely from digital 3D modelling in Ecotect of solar energy available on the site. This showed that solar gain increased with height, up towards the Northeast corner of the site. The building is therefore stepped back to make the best use of solar gains.  The atria allow diffused daylight from the north to penetrate into the depths of the building via a glazed corridor, which also serves as a 'street' within the building. The overall mass is able to retain the city block format of the surrounding streets, but rotating 30 degrees 'off-grid' allows southerly facades to face towards the southwest, the direction of maximum solar gain.


The Winter Garden, inspired by the Millennium Gardens in Sheffield, is a green public space and a traffic-free access through the site, providing an inclusive welcome to the wider community and also separating the nursery from the main college. This unheated space attenuates the external climate, reducing overall thermal losses in winter in the same way as a domestic porch. A timber portal frame is faced in translucent Kalwall panels, allowing control of solar gain to the facing classrooms without the need for separate brise-soleils on the vertical faces. By careful design and maintenance of tree-planting, it is possible both to provide natural shading (deciduous trees shade out summer sun but allow through the winter sun), and to remove carbon dioxide and other pollutants from the air, acting therefore as both a natural pre-heat and pre-filter for air used in ventilation. This fresh, warmed air circulates along the internal street, drawn throughout the building by the stack effect, to a heat exchanger above the Atrium.


Most of the glazing is concentrated to the southwest-facing external facades, and to the internal, north-lit 'street'. The East elevation is largely windowless because of the traffic, loading noise and general ugliness of the building opposite. Seven 'fins' allow daylight from the south into this elevation, but cut off views both into and out of the college. Fenestration to the north and northwest corner mirrors the proportions of the Victorian buildings opposite. On the West elevation, windows are skewed to the main street axis, reducing the sense of 'overlooking' to and from the public house and adjacent buildings.


This form, with outdoor green space on the roof terraces, with the maximum solar facade and with the fins providing a screen at roof level, provides a range of surfaces on which the students could run experiments on materials, solar energy etc.


Structure :

The load-bearing structure is a framework of recycled steel columns and beams on thermo-active pile foundations. Walls, both internal and external, become then a series of non-structural panels, allowing future re-modelling and adaptation to different needs and increasing the building's useful life-span.


The floors provide the main thermal mass. By ventilating in summer to the cool night air and 'dumping' excess heat built up during the day, the thermal lag effect of the dense concrete allows the building to be cooled naturally, without the need for energy-hungry Air Conditioning. This effect is further enhanced by the internal vegetation. In addition to providing thermal mass, the concrete floors also act as acoustic mass, providing effective sound insulation between floors within the busy building.


Materials :

Since the walls are non-structural, the materials used can be specified for a particular performance or effect – eg. internal walls may require additional acoustic mass or diffused daylighting. A range of interesting materials,  both re-used and recycled, are mixed with newer, experimental cladding materials inspired by the main precedents.


These materials can be classified by their thickness – the thicker, heavier materials at ground and basement levels for solidity or sound insulation, and thinner materials as cladding for the timber-frame pre-fabricated panels, insulated with cellulose insulation from recycled newspapers.


These materials comprise :

ThickGabions containing clean recycled concrete from demolition ; Recycled Tyres/rammed earth ; Wine bottle walls/windows ; Strawbales ; Sandbags (weak concrete mix) ; Drinks cans in lime mortar – empty = insulation; water-filled = thermal/acoustic mass.


Medium ThicknessClay bricks, recycled ; Green living walls.


Thin/CladdingTimber – native, durable eg. larch, oak, sweet chestnut – Vertical, horizontal etc. ; Metals – copper, zinc, aluminium sheeting (recyclable) ; Corrugated Galvanised steel ; Shingles – recycled rubber slates, sitka spruce, larch, crushed cans, car body panels ; Lime render on mesh, Heraklith etc. ; Recycled clay tiles, slates etc. ; Silicone-faced fibreglass fabric


Heating/Cooling :

Space heating requirements are minimised by control over solar gain and via the use of high levels of insulation, airtightness etc. The heating is provided by a Ground Source Heat Pump driving underfloor piped heating within the floor screeds, thermoactive piles being the source of low-grade heat for the process. Heat requirements are further minimised by recycling the heat in stale ventilated air through a Heat Recovery and Ventilation (HRV) System. Most of the water heating is provided by a bank of Evacuated Tube Solar Heating panels situated on the internal faces of the 'fins', with backup from electric immersion heaters.Cooling is provided by a combination of the high thermal mass, stack ventilation and HRV, negating any requirement for refrigerated air conditioning.


Precedents :

The main precedents/inspiration for the project are the Strawbale House and Heathfield Children's Centre & Nursery, by Sarah Wigglesworth Architects; The Stephen Lawrence Centre, by David Adjaye, and by the work on Earthships by Mike Reynolds in New Mexico.


Rather than focussing on architectural form, the  'low-tech, hi-spec' technologies exemplified by these precedents have influenced the college design in terms of performance, the use of materials, and in its overall sustainable ethos.


 

Concept 1

Concept 2

Detailed Section 1

Detailed Section 2