Sustainable Design and Construction Measures
Their Costs and Benefits
| What Measures? |
A key part of the project has been to assess the costs and benefits of a range of sustainable design and construction measures to try and identify those that should be given priority by planners when preparing development briefs or when reviewing submissions. The list should also help developers and planners to prioritise those measures that lead to the greatest real benefit for the minimum cost. In order to prioritise the measures, we determined the additional capital costs to a developer of implementing them. We also assessed the benefits the measure will result in to the developer, the building occupier, the local authority and the wider environment to create a matrix of measures. This section describes how we have developed the Cost vs Benefit Measures Matrices for domestic and industrial scenarios.
We developed a list of sustainable design and construction measures which would be applicable to most schemes and which would represent an improvement over standard practice. These were drawn from measures included in BREEAM & Ecohomes, and other best practice guidance sources. We established a number of generic development scenarios intended to reflect current development practice and the type of development proposals that are likely to result from the Government’s Communities Plan. For each scenario we established a base case scheme to represent a development built to the minimum requirements of Building Regulations 2002 and which assumed the use construction methods typical of those in use at the present time. A quantity surveyor provided the additional costs that would be incurred for each sustainable design and construction measure. These costs are on a per unit basis. For measures applying across a scheme such as the provision of a wind turbine or community heating system, the costs were divided to arrive at a per unit cost. Housing The base schemes for housing were chosen to represent the range of housing types that might be expected to be promoted under the Communities Plan. Dense, large-scale urban development with low and medium rise housing Dwelling types including 2/3 storey terraces, 4/5 storey blocks and some high rise built to densities of between 50 and 200 dwellings per hectare. This would include a mix of approximately 35% affordable and 65% private housing. 2 bed apartments with a floor area of 65m2 would be the predominant dwelling type. Medium Density suburban development Dwelling types including 2/3 storey terraced housing, detached housing and 4/5 storey apartment blocks built to densities of between 30 and 50 dwellings per hectare. 3 bed units were assumed to be the predominant built form with typical floor areas of 85m2, 20% of housing would be 2 bed apartments with an area of 65m2 and 20% would be 4 bed units with an area of 100m2. In order to examine impact of economies of scale, costs were assessed for both a 50 unit scheme and for a 500 unit scheme for both.
The base cases for industrial are two types of building typical of those submitted for assessment under the BREEAM scheme for industrial units - a typical B1 factory unit and a larger warehouse distribution building. Typical B1 Factory Unit A 6000 m2 factory unit comprising 5000m2 production area and 1000m2 of office accommodation, with a 7m high steel portal frame with profiled metal cladding or composite panel cladding system. There is two storey office accommodation along one elevation which would be naturally ventilated and provided with a low pressure hot water (LPHW) central heating system with radiators. The production area has direct gas fired radiant heaters. Typical Warehouse Distribution Centre A single storey 16340m2 distribution warehouse unit of which 3340m2 is office accommodation arranged over two floors with a depth of 15m. The building has a steel frame with profiled metal cladding. Offices are naturally ventilated and provided with a LPHW central heating system with radiators. The production area has direct gas fired radiant heaters. Cost bands – low, medium and high The additional costs were banded to achieve a roughly even spread of measures in three cost categories - low, medium and high. Domestic Low cost: Less than, or equal to £100 / measure / unit Medium cost: Greater than £100 and less than £750 / measure / unit High cost: Equal to or greater than £750 / measure / unit Industrial Low cost: Less than, or equal to £2000 / measure / unit Medium cost: Greater than £2000 and less than £50,000 / measure / unit High cost: Equal to or greater than £50,000 / measure / unit IT MUST BE REMEMBERED THAT THE MATRIX IS TO BE USED AS A DISCUSSION TOOL AND IS INDICATIVE ONLY.
How did we assign benefits to the measures? All of the sustainable design and construction measures listed have positive benefits and in an ideal world would be included as standard in most developments. Some of the benefits can be quantified - such as carbon dioxide saved for energy efficiency measures and volume of water saved for water efficiency measures. However there are other benefits - such as positive impacts on health or amenity or biodiversity that cannot easily be quantified. From discussions with the project steering group we decided to identify the key groups to which benefits accrue. We identified four key beneficiaries of the measures in relation to our project audience. For each beneficiary we identified three categories of benefit that would allow us to score the benefits of a measure on a scale of 1 to 3. The three categories of benefit for each of the four beneficiaries are set out below, with one point available for each: LOCAL AUTHORITIES –
GLOBAL ENVIRONMENT
BUILDING OCCUPIER –
DEVELOPER
To assess the overall benefit of each measure, the project team, colleagues within FaberMaunsell’s sustainable development group and the project partners were asked to assign scores to each of the Sustainable Design and construction measures identified for our scenarios. While we recognise this is a subjective process it is felt that it provides some basis on which to classify the measures. It is should also be noted that while a SDC measure might be felt to have a positive impact on planning, there may well be other more basic issues that need to be taken into account as part of the planning process (such as affordable housing). The measure proposed must also be suitable for the site in question for it to be a possible positive impact on planning. The scores were averaged and assigned a benefit bracket:
The matrix was discussed at regional workshops held in March 2004 and groups of planners and developers were given the opportunity to discuss the matrix and move measures around the grid. 80% of the measures were not moved giving a reasonable degree of confidence in the matrix, however for those measures that were moved, there was very little agreement between the different groups as to where it should be moved. The FaberMaunsell project team have made some tweaks to the matrix, using their professional experience to adjust the ranking of those measures where benefits can be quantified, but it should be remembered that there is still a large degree of subjectivity in the ranking of the benefits and the main purpose of the matrix is as a discussion tool to introduce a range of practical measures for consideration. Due to the degree of subjectivity in comparing benefits, a separate information sheet has been prepared for each measure. This provides a brief description of the measure and the expected benefits that will arise to the occupant, developer, local authority and broader environment. By comparing these benefits against cost, the measures have been grouped into one of three categories: Fit as standard, exemplary, low priority. We have also indicated the difficulty of implementing the measure as an indication of the resistance there may be to including the measure in development proposals. See the Sustainable Design and Construction Measures Database for more details on the information sheets. IT MUST BE REMEMBERED THAT THE MATRIX IS TO BE USED AS A DISCUSSION TOOL AND IS INDICATIVE ONLY.
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