Cyril Sweett was commissioned by English Partnerships and the Housing Corporation in August 2006 to produce a report* considering the implications of moving from EcoHomes Very Good to the Code for Sustainable Homes (the Code).

They wanted to examine how compliance with Ecohomes Very Good is typically achieved and the performance of these homes in terms of water and energy efficiency and the extra-over costs and impact on environmental performance of housing complying with the Code rather than EcoHomes.

Costs and savings

The environmental savings expected from moving from Ecohomes ‘Very Good’ to Code Level 3 equate to a 25% reduction in carbon emissions per house and 21 litres per person per day.

The report says there is a cost premium associated with achieving Code Level 3 in comparison to EcoHomes Very Good. The major reductions in carbon dioxide emissions and water consumption account for the majority of this additional cost.

These costs vary depending on the house type and the feasibility of using different carbon saving technologies (e.g. micro-wind turbines). The assessment therefore looked at six generic house types and considered a wide variety of technological solutions for achieving improved performance.

The house types considered were:

• Detached house (gross internal floor area of 116m²)
  
• End terrace / semi-detached house (gross internal floor area of 101 m²)
  
• Low rise apartment (net unit area of 59 m²)
  
• Medium / high rise apartment (net unit area of 75 m²)
  
• Two homes built using modern methods of construction and compliant with the requirements of English Partnerships’ Design for Manufacture (DfM) competition
  
• An end of terrace house (76.5 m2); based upon the Weber Haus product
  
• A mid terrace house incorporating a centralised CHP system (76.5 m2); referred to in this report as the ‘SixtyK House’

Scenarios

The central concern on getting to Code Level 3 is reducing the carbon emissions associated with energy use. Four scenarios were considered for reaching the required energy levels.

These scenarios represent only a selection of the multitude of different possible approaches. This report does not advocate any particular solution and the most suitable approach will need to be determined on a project specific basis.

• Scenario 1 – Initial energy efficiency measures followed by use of solar thermal technology and then photovoltaics and biomass systems.
  
• Scenario 2 – Initial energy efficiency measures initially followed by use of small scale wind turbines and then biomass systems
  
• Scenario 3 – Development with shared energy services, such as combined heat and power (CHP). For this scenario costs per unit are averaged for different infrastructure options for a theoretical 200 unit development.
  
• Scenario 4 – Achievement of Code Level 3 without recourse to renewable energies through the use of a whole house mechanical ventilation system with heat recovery and by assuming the use of proprietary construction details .
  

Analysis of the results shows that costs are lowest where it is possible to use wind energy or site wide CHP. However, not every location will be able to make use of these technologies. For example, some urban locations may not have sufficient consistent wind speed to generate appreciable quantities of wind energy.

Correlation between Code Level and costs

For the traditional house types, the costs for achieving the mandatory performance standards for energy can be summarised as:

• Code Level 1 – relatively little additional cost is incurred as this level of performance improvement can be achieved through simple measures such enhanced building controls. The only exception is for the high rise apartment where a cost of around £2,800 per dwelling is incurred to install a communal heating system
  
• Code Level 2 – at this level the costs begin to be influenced by the approach taken to efficiency measures (i.e. improved insulation, wind turbines or CHP) costs range from around £1,000 to £1,800 per home.
  
• Code Level 3 – again costs are variable depending on the carbon reduction scenario followed. Costs range from around £1,600 (where wind turbines are used) to over £4,400 where mechanical ventilation is used) for the high rise apartment the costs vary substantially from nearly £6,000 (where solar water heating is used) to as low as £1,700 where the apartments are included within a site wide CHP system.
  
• Code Level 4 – At this level costs increase to between £5,000 and £16,000 per home depending on whether a wind turbine or photovoltaics are used to achieve carbon savings. Achieving Code Level 4 compliance if no wind energy can be used requires substantial use of photovoltaics (1 kW). The use of a site wide CHP system should also enable the level of performance to be achieved more cost effectively.
  
• Code Level 5 – At this level the costs of vary between £14,000 and £30,000 depending on house type. However, for the houses and low rise apartment the enhancements required to achieve Code Level 5 (i.e. biomass heating systems) result in an over 100% improvement on TER (sufficient for Code Level 6).
  

Code Level 3 compliance could be achieved more cost effectively for housing through the use of micro CHP systems. However, the report says these are not currently widely available in the UK and it is not expected that they will be available in significant numbers until 2008.

For the DfM, house types it is estimated that both house types could achieve the energy standards for Code Level 3 at no additional cost, while the SixtyK House could achieve the Level 4 standard at no cost. The DfM homes have substantially lower costs of compliance because their base specifications are already highly thermally efficient, and in the case of SixtyK House include the use of renewable and low carbon technologies.

Mandatory water standards

It is possible to achieve reductions in water consumption to 105l per bedspace per day (38m3 per year) at very little or no additional cost. This requires the use of:

• Dual flush toilets (6/4l)
  
• Aerated taps
  
• Smaller ‘shaped’ baths
  
• Flow controlled showers (to between 6-9l per minute)
  

This level of water efficiency is sufficient for compliance with Code Levels 1 to 4. To achieve further reductions beyond 105l per bedspace per day (38m3 per year) there is a need for at least one of the following:

• Use of ultra low flow showers and very low flush toilets. These options are not significantly more expensive but might impact the marketability of homes
  
• Installation of water efficient white goods (washing machine and dishwasher)
  
• Installation of greywater recycling or rainwater harvesting systems, or both.
  

For levels below 105l per day (Code Levels 5 and 6) costs are approximately £2,520 for houses and £640 for apartments. In houses it should still be possible to reduce the costs of greywater and rainwater systems by around 50% by the use of shared infrastructure.

Cost and performance of Code relative to EcoHomes 2006

The mandatory performance standards in Code mean that the costs of compliance are higher at every level although this becomes most noticeable at Code Levels 3 and 4 (equivalent to Ecohomes Very Good and Excellent ratings).

The energy requirements associated with Code Level 3 are such that the costs of achieving this standard are between 1% and 6.2% of the base cost of a home higher than for EcoHomes Very Good. Costs are critically dependant on the approach taken to achieving the energy component of the Code. Where it is not possible to use site wide CHP or wind turbines then the additional cost of Code Level 3 over EcoHomes Very Good is 3% to 6.2%.

Potential of site wide approaches to reduce the costs of compliance

Analysis of the costs of site wide technologies for a 200 unit development scenario suggest that higher energy and water performance standards can be achieved more cost effectively using site wide approaches.

In particular, the use of an ESCO can help to substantially offset the costs associated with meeting carbon reduction targets. In the case of the SixtyK house the Code Level 4 standard for energy/carbon should be achieved by ‘outsourcing’ the energy services aspect of the development to an ESCO.

In this instance the developer expects the involvement of an ESCO to enable the capital cost of the installation to be fully offset. Where the scale of development is appropriate the involvement of an ESCOs could offset all or a large proportion of the additional capital expenditure associated with the use of low carbon technologies.

However ESCO’s are only likely to be viable in relatively large schemes (+350 units) and would need appropriate development phasing and densities.

Evidence suggests that all of the technologies likely to be needed to deliver Code Level 3 are likely to reduce in cost over the next 2 to 5 years. This would result from the increased demand associated with the adoption of the Code and also from other initiatives such as PPS22 that are encouraging the use of renewable energies.

However, further work would be required to assess more quantitatively the likely scale of price reductions.

Solutions which are currently emerging and other factors that might lead to cost reductions are:

• Innovation in design and specification within the housing sector
  
• Emergence and development of new technologies / construction methods better suited to meeting the required performance standards
  
• The impact of the £80m set aside for grants and bulk purchase agreements of micro generation by the Department for Trade and Industry
  
• The involvement of an Energy Services Company (ESCO) in a development
  
• Reduction in cost of existing products arising from their widespread adoption
  
• Bulk purchasing of products
  

Further cost reductions may also arise in the medium term from the use of technologies still at a relatively early stage of development, such as thin film PV and vertical axis wind turbines.

The report points out that carbon emissions reduction is a relatively recent focus for the sector.

Once the collective intelligence of the construction industry is applied to the issue of meeting the required targets it is likely that more efficient / innovative solutions might be adopted that achieve the same performance at lower cost.

* A cost review of the Code for Sustainable Homes

Table 1: Energy and water performance standards in EcoHomes and the Code

	EcoHomes	Proposed levels in the Code for Sustainable Homes
		1	2	3	4	5	6
Energy (% improvement over ADL1 2006)	0%	10%	18%	25%	44%	69%	100%
Water (l per bedspace per day)	126l	120l	120l	105l	105l	80l	80l

Table 2: Additional cost for Code Level 3 over EcoHomes Very Good

	Tradiotional detached house	Traditional terraced house	Low rise apartment	High rise apartment
Scenario 1	£4,525 (4.8%)	£4,373(5.7%)	£2,579 (3.2%)	£4,900 (3.8%)
Scenario 2	£2,852 (2.9%)	£2,786 (3.5%)	£1,498 (1.9%)	£2,699 (2.0%)
Scenario 3	£3,131 (3.2%)	£3,165 (4.1%)	£946 (1.2%)	£643 (0.4%)
Scenario 4	£5,090 (5.4%)	£4,748 (6.2%)		£3,942 (3.0%)