Social housing supplement Retrofi t
Retrofi t & Replicate I: Mottingham, three-bed,
mid-terrace house, completed Dec 2008
Measure
Internal wall insulation
Floor insulation Roof insulation
Air leakage reduction strategy
Heat recovery ventilation
Windows and door
Effi cient heating system
Lighting
Solar thermal collectors and storage
Photovoltaics
Auxiliary electricity use
Totals
R&R1: Existing SAP = 60; proposed SAP = 94
* Figures based on modelling – results of post-occupation analysis awaited
Retrofi t & Replicate II: Eltham, 1915 end-of-terrace,
two-bed house, retrofi t starts June 2010
Measure
Internal wall insulation
Description
100mm wood fi bre plus lime plaster fi nish
Floor insulation Wood fi bre between and over joists
Roof insulation
Air leakage reduction strategy
Heat recovery ventilation
Windows and door
Effi cient heating system
Lighting Photovoltaics
Appliances
Totals
Blown cellulose insulation
Wet lime plaster, fl oor panels, OSB ceiling, proprietary tapes and loft hatch
Envirovent Energivent Q modular system plus ducting
Legacy vacuum-glazed, timber casements from Jeld-Wen
Baxi Ecogen micro-CHP boiler plus rads plus Wattbox controller
Antares LED
0.85 kWp polycrystalline array at 40-degree pitch
A++ rated
R&R2: Existing SAP = 42; proposed SAP = 90
* Projected fi gures
Performance (U-value, etc)*
0.20 W/sq m K 0.10 W/sq m K
Min 3.0 q50, down from 9.4 q50
86% effi cient heat recovery, sfp = 0.74 W/l/s
Uw, 1.55 W/sq m K 0.488 tonnes/yr £18,323
85% combined effi ciency
3.7W per lamp
1,146 kWh per annum predicted
1.249 tonnes/yr £9,241
0.125 tonnes/yr £3,355 0.484 tonnes/yr £12,642
0.134 tonnes/yr £2,308
6.273 tonnes/yr* £69,191
0.746 tonnes/yr £10,384
CO2 Reduction* Installed Cost
0.33 W/sq m K 3.047 tonnes/yr £12,938
Description
80mm phenolic board added to extg cavity fi ll
Phenolic boards btwn joists
PUR boards plus TLX Gold multifoil
Roof membranes, wet plaster, mastic and foam seals.
Vaillant ecoVAIR 275 plus ducting and diffusers
Triple-glazed, argon-fi ll, warm edge, alu-clad timber/PUR frame
Vaillant ecoTEC system boiler plus rads
Antares LED
3.68 sq m dual-facing Kingspan fl at plate collectors plus 250 litre hot water cylinder
1.36kWp polycrystalline array at fi ve-degree pitch
Pumps, fans etc
Performance (U-value, etc)*
0.20 W/sq m K 0.10 W/sq m K
5.6 q50, down from 9.2 q50
85% effi cient heat recovery, sfp = 0.85 W/l/s
Uw, 0.7 W/sq m K
91% effi cient, 40mg/kWh NOx emissions
3.7W per lamp, 180W total
1,240 kWh predicted
1,200 kWh per annum predicted
n/a 0.266 tonnes/yr £9,640 0.930 tonnes/yr £5,000 0.177 tonnes/yr £2,505 0.378 tonnes/yr £5,300
>
0.664 tonnes/yr £3,200
Mark Elton (right) with former science minister Lord Drayson.
simple more/less heat toggle for instant adjustment. The regulated electrical load of the property will be reduced through the employment of LED lighting technology, building on our experience with supplier GreenLED from the Mottingham project, which had a maximum lighting load for the house of 180 watts. A Schüco PV light array integrated fl ush with the roof tiles on the rear of the property is the only contribution from renewables in this scheme. Many lessons learnt during R&R 1 are being applied
0.177 tonnes/yr £4,950 -0.086 tonnes/yr incl
3.678 tonnes/yr* £39,495
to the follow-up project. There is a greater emphasis on airtight refurbishment techniques, a more co-ordinated approach to the mechanical and electrical layouts, more intuitive technologies and far simpler controls for the occupier. We have found that the tenant at Mottingham was reluctant to engage with the boiler programmer and the ventilation settings – the risk is that tenants will simply turn the systems off and resort to opening windows in winter, as the Mottingham family have tended to do. Mears also has a better understanding of the logistics of working with multiple systems in a single dwelling, although a workshop following the Mottingham project determined that the high calibre of site work supervision needed was only economical when retrofi t is undertaken on a larger scale. Modelled emissions for the Eltham retrofi t amount
to 18kgCO2/sq m/yr, an ambitious reduction in emissions of 87 per cent. The Mottingham modelling indicated a carbon saving of around 83 per cent, but this was against a starting SAP modelling tool rating of 60. The cost of the innovations in the Eltham project is higher however, with an installed cost for the low carbon measures of around £87,200 compared to £40,000 for the previous project. Following occupation, the performance of the property is being monitored for two years via fuel bills and room sensors measuring internal temperatures, relative humidity levels and internal CO2 levels. The Wattbox will gather this data and send it to the Energy Saving Trust, which has responsibility for collating and ultimately disseminating the feedback. It will also carry out post- occupancy interviews to obtain fi rst-hand accounts of living in a low-carbon retrofi t. ●
Mark Elton is the head of sustainability at ECD Architects (energy conscious design) in London.
CO2 Reduction*
Installed Cost
0.15 W/sq m K 1.196 tonnes/yr £8,900
18 CIBSE Journal June 2010
www.cibsejournal.com
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