Case Study: Generation Homes - Woodfields

Short Description

The project, undertaken with the support of the Energy Savings Trust, was to demonstrate how a minimum 60% reduction in household CO2 emission post refurbishment can be achieved by employing a systematic package of energy efficiency measures to a small neighbourhood of homes.

The six 1950s off gas network homes, 3 x 3 bed two storey semi and 3 x 2 bed semi bungalows, were in 2007, the first grouping of homes refurbished to meet the ‘Generation Homes’ standard in UK.

The package of measures employed to each dwelling comprised:

- Ground Source Heat Pumps;
- Photovoltaic array;
- Waste water heat recovery (3 x houses only);
- Heat recovery ventilation;
- Improved insulation and air tightness following pressure testing results.

This package of measures collectively resulted in annual household CO2 emissions being slashed from 9.8 to 2.4 tonnes, a 75% reduction.

Key Elements

Certification

NHER (standard energy modelling software) was applied to the baseline case - before work - and again on completion to assess the impact of the measures employed.

Project Management

This was found to be challenging as there were often many different contractors / specialist sub contractors on site simultaneously.

Asset Management

Radian’s stock condition survey data and asset management strategy was used to identify the candidate properties. SAP ratings for the homes, located off the gas network and formerly reliant on solid fuel and electric heating, were very poor.

Capacity Building

A primary objective for the completed scheme was to raise awareness of the scale of the retrofit challenge in the UK through effective dissemination in order to start to build capacity. Over 500 delegates have visited the homes and more than 1,500 have been addressed via seminars and conferences in two years.

Consultant support and strategic direction was essential for our first whole house retrofit project. Collaboration took place with energy suppliers in relation to CERT funding and assisting residents with PV electrical export. Local Authority partnership support was highly successful. Very high levels of interest from policy / strategy and research type establishments post completion.

Work with Residents

Close liaison with residents was necessary in order to explain optimum operation of the innovation / technologies installed.

Simple to use instructions were produced for residents together with a series of face to face briefings and performance in use reviews. A full two year independent performance review is currently in progress.

Funding

The project was traditionally financed predominantly using Radian’s own funds supplemented by capital grant receipts via LCBP, CERT funding and a contribution from the Energy Savings Trust which also covered consultants fees.

Thermal Insulation

Traditional materials, upgraded to increased thickness only.

Air Tightness

Air pressure testing on completion was in the range of q5-6 a result that was better than expected.

Ventilation

Heat recovery ventilation to bathrooms added to existing natural ventilation strategy.

Heating and Hot Water

Ground source heat pumps are means of primary heating. Waste water heat recovery units were installed (not renewable). Coiled copper heat exchanger inserted to replace vertical waste pipe serving shower / bath and basin waste in the 3 two storey houses. This energy efficiency measure recovers 60% of heat otherwise lost down the drain and recycles for re use.

Solar Photovoltaic

1 kWp array per dwelling installed. Over roof system.

Water Saving

Low energy lighting provided.

Main Results

The project has been successful in raising awareness of the need for greater retrofit activity in the UK and has helped motivate other organisations to undertake exemplar retrofit projects.

A review of the project has commenced and will be based on two years worth of data that has been collected from the sophisticated monitoring that was installed. In addition to looking at the energy and running cost savings obtained, this will also look at social aspects through interviews with residents to ascertain satisfaction levels, ease of use of technology and the like.

The full findings of the detailed review will be published in an updated case study. Provisional findings suggest that carbon savings achieved have been in the range of 49-83% against modelling of 75% and that running cost savings are in the range of nil – 50%. It is believed that the reasons for these lower than expected initial outcomes can be explained in part by residents taking up some of the benefit of the new heating systems in improved thermal comfort. The early findings would also suggest that further work regarding user behaviour change and operation of the technology would benefit the residents.

Some residents were more enthusiastic regarding the project and its aims than others. Reducing running costs rather than climate change emissions was the greater motivator for residents. Overall, notwithstanding the interviews to be conducted as referred to above, resident satisfaction levels are believed to be more positive than negative.

The cost of the refurbishment was on average a total of £30,000 per property (33,000euro) towards which 50% grant funding was obtained from the various sources referred to above (LCBP, CERT & EST).

Lessons learned

The need for effective liaison and an ongoing dialogue with residents at all stages of the process from conceptual design through to monitoring cannot be understated.

Project management was found to be challenging and even more so because the works were undertaken while residents remained in their homes. Numerous different contractors were involved in the refurbishment process making the programming of works operations critical.

Of the technologies installed, the Ground Source Heat Pumps produced the greatest number of issues to be addressed. Initially, the ground conditions were found not to be the most conducive to drilling boreholes. The soft wet sand strata led to frequent collapse of the boreholes and meaning they had to be sleeved for their length. The design depth of boreholes was 80m and as a result of difficulties with drilling, the contractor opted for two shorter boreholes at 40m depth each connected in series and spaced out 5m apart. Some minor problems were experienced with operation of GSHP initially. This was followed by the need to undertake extensive resident briefing on optimum operation of the GSHP especially in relation to programming of heating and hot water. Despite the problems experienced with the GSHP, by and large, it was possible to satisfactorily resolve all the problems faced in full.

As the first large scale installation of domestic GSHP in the South East this was perhaps to be expected.

The waste water heat recovery units were an interesting technology to trial. The performance in use data gathered would, however, suggest that this type of innovation would be more appropriate in commercial applications e.g. sports centres or laundries for example where greater volumes of hot water is more constantly wasted.

The photovoltaic installations have been successful and did not produce any difficulties. Four of the six households have elected to enter into agreements with their energy supplier to export surplus electrical generation back to the grid for sale. On average approx 25-40% of generation is being exported to grid for which the residents obtain a small but welcome additional income.

Gathering data from the monitoring meters was time consuming and where possible remote monitoring using modems is recommended and will be considered for future use.

Following the energy design hierarchy, before considering the application of renewables, it was necessary to improve the basic energy efficiency measures first of all by improving insulation and air tightness.