Construction Time: Eleven Months
Completion Date: October 2012
Gross Floor Area: 679m2
Contract Value: £389K + VAT
Build Rate: £523/m2 + VAT
‘U’ Values: Roof – 0.13W/m2K. Walls – 0.18W/m2K. Floor – 0.15W/m2K.
Heating: Gas condencing boilers
Carbon Impact: 40% reduction (anticipated)
Main Contractor: Westridge Construction Limited
As one of the first projects of the new eco-town of Bordon in East Hamphire, the former Ministry of Defense fire station which served the old garrison town was converted into a new eco-town headquarters where the emerging plans for the new developments can be directed and communicated. The new facility will include a multi-use exhibition space, a lecture theatre, community resource and meeting rooms and office spaces for the delivery team and commercial tenants. The 679 square metre Eco-Station will demonstrate how a redundant building can be brought back to life to serve a new purpose – as well as being refurbished to reduce its carbon footprint.
The refurbishment strategy will:
- Halve the carbon footprint of the building (carbon footprint is a measure of environmental impact)
- Reduce the energy required to heat the building by approximately 60%
The brief called for fully inclusive and accessible facilities to suit a range of users including visiting school children, those with limited mobility, community groups, the Whitehill Bordon Eco-Town delivery team and commercial organisations taking lettable office space. The building is flexible to accommodate evolving uses and users.
‘Make Good and Mend’
The project, which includes extensive new landscaping of the fore and rear courts, challenged the team to find the most cost effective eco-retrofit solutions to deliver the aspirational energy targets. The solution was to adopt a base level upgrade to the entire building with certain areas, which were deemed to be ‘change of use’, receiving extra thermal efficiency upgrades and implementing an upgrade strategy which would allow over time remaining areas of the building to be brought up to the full specification. The strategy also needed to identify ground floor areas which needed to be tackled in the first phase of work, in order to avoid decanting issues. The make good and mend strategy extended to working with/adapting existing pvc double glazing, heating and electrics as well. The cost of works to Eco-Station (less landscaping) is roughly £431K or about £639/m2.
External or Internal Insulation?
BBM stressed the need to properly evaluate a technically superior external insulated solution to the building fabric over the problematic internal lining proposition. In the end, and responding to community opinion, it was agreed the building’s outward appearance should be maintained and would be internally insulated. Luckily the structure had a cavity wall which allowed the entire outer perimeter to be afforded a basic standard of thermal efficiency and which would help to protect embedded intermediate floor joists from intersitial condensation.
The annual heating energy for both the existing and proposed building has been calculated with IES modelling. This requires the inputting of the thermal characteristics of the building’s walls, roof, floor and glazing along with the building’s orientation and design air temperatures. The calculation uses standard weather data for outdoor temperature and solar intensity on an hourly basis.
The existing building’s estimated carbon footprint is: 91kgCO2/m2/annum. The proposed building performance (whole building retrofit) would be: 47kgCO2/m2/annum (using gas heating) or 28kgCO2/m2/annum (using biomass). By improving the thermal standard of the building, the space heating energy can be reduced by 61%.
Site Waste Management Plan
The reduction of construction waste is a major concern of the industry with a hardening regulatory framework set in place to ensure that those involved in construction projects comply with their legal requirements. All projects over £300K in contract value need to adopt a Site Waste Minimisation Plan. In February 2011 the Client Team was approached by Waste Works which is a work experience programme run in conjunction with Ford Open Prison as a means of providing practical site training for inmates who are nearing the end of their custody. The proposition was that Waste Works would assist the main contractor in diverting the site waste away from landfill and either to be re-used in the building or to some off-site form of salvage. The data collected during the course of the build has indicated a pretty much ‘skip free’ status on the Eco-Station.
Overview of Sustainability Features
- High performance insulation materials to reduce energy use of the building from around 170kwh/m2/yr to about 65kwh/m2/yr
- Thermal upgrade strategy to allow a phased implementation when afforded without having to decant occupants;
- New solar thermal installation
- New space heating controls added to adapt the heating requirements of various spaces
- New energy efficient lighting
- Passive ventialtion to offices and new passive stack ventilation to AV Lecture Space to help reduce fan energy usage
- Incorporation of a waste minimisation strategy to divert maximum waste materials away from landfill
- The recycling and sorting on site will help Ford Open prison inmates acquire useful job skills
- Design for deconstruction strategy applied to new installations to maximise re-use and recycling of salvaged resources.