IntroductionClay carbon emissions embodied during construction and will only

IntroductionClay Field is an affordable housing development in Elmswell, Suffolk. In this case study, we will discuss the different strategies used for construction, energy use and the environmental considerations which have achieved a good amount of sustainability and low levels of embodied carbon emissions. There are 26 houses which include 13 two bedroom and nine three bedroom houses, plus four one bedroom flats and private gardens. The homes are grouped in threes around three communal gardens and parking courts with 42 car parking spaces.  There are a range of amenity spaces including allotments, a local play area, a large football pitch and swales to manage rainwater as part of a green space strategy. Rainwater is collected to flush toilets and to water the gardens. There are three gardens which have been incorporated with the existing village, a wild flower meadow, allotments and an orchard. As well as, a communal biomass heating system that is able to heat all properties from one boiler that is powered by woodchips from the local forestry. The aim of this project was to provide affordable homes that are energy efficient and sustainable whilst having a high quality design and provide green, eco-friendly public and private spaces. Every property has a very small amount of carbon emissions embodied during construction and will only need a small amount of energy use in its entire lifetime. A key factor in this achievement is the use of a material that consists of mixture of hemp and lime that is sprayed onto the building and captures carbon from the atmosphere. Many of the roofs are also covered in a recyclable, renewable resource which captures a further amount of carbon and reduces the loads of buildings.Environmental Strategies  Shelter from the elements   The layout of the site provides good shelter from the wind because these properties have been built in a flat area with little natural resistance to high winds but you can see the trees and arrangements of the property groupings would provide shelter to the enclosed areas that have been created.  Rainwater Harvesting  The rain is collected and used in a communal rainwater harvesting system. The total rainwater harvesting storage capacity on site is 26,000L. Each block of dwellings is supplied with a Rainsava 6,500L underground holding tank.   The rainwater that falls on the roof is collected to by guttering. In the pipework before the holding tank a vortex filter has been installed toensure no leaves and debris enter the water supply. In order to distribute the filtered water to the headertanks in each house, the holding tank has a submersed pump. The pressurization of the pump is monitored and controlled outside of the properties, by a unit in the landlord’s shed. To prevent the water level becoming too low, the control unit also connects the header tanks to a mains cold water top up facilityduring low rainfall. The header tank then distributes recycled rainwater to the bathrooms of each house, aswell as supplying garden taps.     Light (natural + artificial)   The layout and orientation of the site ensures that all properties receive maximum sunlight in different seasonal conditions despite the flat landscape. All houses face south, however the 2 storey terraces are not overshadowed by the 3 storey properties in the low angled winter sun. As a result, the houses have good daylighting. The 2-storey houses have a picture window within a deep reveal in the kitchens which gives the greatest passive solar gain. The type of artificial lighting used in these properties would align with the sustainability and energy efficiency of the rest of the project. Therefore, artificial lighting with low energy efficiency rating such as incandescent lamps would be replaced with LED or compact fluorescent lamp (CFL) lighting.    Heating & Cooling   Biomass Boiler  One biomass heating system is responsible for all 26 properties. The biomass which powers thiscommunal boiler is from the local forestry. It uses wood pellets and has a nominal 150 – 180 kw output, using a Twin Heat CS150i automatic biofuel boiler and holds around 3,500L of water. Heat exchangers have been placed in each house to control and distribute heating and hot water to the property. There are also metering facilities that are able to monitor the fuel consumption of each property remotely. Therecorded flow temperature is 80ºC with a return temperature of  60ºC.    Ventilation   The houses have been designed so that the stairwells can be used for passive stack ventilation strategy. The staggered floors have been incorporated so that the open stairwell running from the roof lights to the kitchen allows the homes can be naturally ventilated with a through-flow of air during the summer. An additional mechanical system is used during the winter which heats incoming air by using 80% of the heat from outgoing air.  A whole house ventilation system has also been designed to change all air within the property at least once every two hours. This is achieved using a network of ducts within the property which extracts stale air from the bathrooms and kitchen by using the heat recovery units inside the cooker hoods which also supplies fresh filtered air to the Living Room and Bedrooms.  Human Comfort  All of these environmental strategies have shown great consideration of human comfort. The properties provide warm, light and spacious homes with low running costs through use of passive solar gain in south facing glazing during cold weather and easy ventilation during summer. This also provides greater thermal comfort and less strain on the communal biomass boiler. Consideration of the east-west orientation of the site layout has helped to achieve minimal visual impact and overshadowing between the properties of different sizes.  As well as contributing to thermal comfort, the whole house and passive stack ventilation systems used provide fresh air throughout the house and creates a healthier home environment.    

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