Property background:

Bertram Street Low Energy Victorian Terrace:
This house was retrofitted with energy efficiency measures to reduce CO2 emissions by 77%. These included a pioneering method of fitting internal wall insulation while the residents continued to live in the property. Sustainable features include vacuum glazing, MVHR, solar thermal and PV.

The property is a 3 storey Victorian (1880s) terrace, located in the Dartmouth Park Conservation area. In 2010 a consortium of Camden Council, the Sustainable Energy Academy, United House and Parity Projects won funding under the Retrofit for the Future competition to upgrade the property to reduce carbon emissions by 80%. The key feature of the upgrade was the technique (known as WHISCERS) of fitting internal wall insulation by using laser wall measurement and off site panel cutting to reduce mess, disruption and work time.

Project Partners
The Sustainable Energy Academy, United House, Parity Projects, Camden Council Housing Unit and the National Energy Foundation. The refurbishment was funded through the Technology Strategy Board’s Retrofit for the Future Programme.

Key changes made:

1) The heat demand of the house was reduced by cocooning the house in an envelope of insulation and advanced low energy glazing:
a) Internal wall insulation (100mm in most areas), reducing the U-value from 2.1 to 0.21, installed using the WHISCERS method
b) Vaccuum glazing in sashes, reducing the U-value from 4.5 to 1.8
2) The air flow through the house was controlled by draught stripping all windows, and providing mechanical ventilation and heat recovery in areas of high humidity (kitchen and bathroom)
3) Renewable solar energy was used to supply hot water and electricity (1.1 KWp) – over 1000 KWh of electricity generated in the first year of operation
4) The remaining energy demand was efficiently supplied using an “A” rated condensing boiler
5) Appliances were chosen to reduce electricity demand, and meters provide information and feedback to residents to enable them to reduce their energy consumption further.

Measures installed in detail:

• Windows – sashes remade with Pilkington Vacuum glass U-value=1.8, original boxes retained. Windows fully draught stripped.
• Internal wall insulation – 100mm Knauf Polyfoam (extruded polystyrene) in most areas, 50mm in stairwells due to restricted space.
• Loft insulation- 270mm mineral wool.
• Limited insulation added at joist ends within floors with additional sensors.
• Heat recover- MHRV Vent-axia HR25 units in kitchen, bathroom and cloakroom.
• Condensing boiler with TVRs and good controls.
• 8sqm flat plate solar thermal system, with twin coil cylinder for dual heating.
• 8sqm Photovoltaics – 1.1kWp.
• Megaman low energy lighting throughout house.
• A++ Fridge freezer 205kWh per year.
• Low flow shower head.
• External doors replaced with Front door- U value 2.2. Rear door U value 3.0.

Other Camden homes open to the public this September to view: St Augustine’s Road and Belsize Park Gardens

Benefits of work carried out:

Significant reductions in CO2 emissions and heating costs were achieved by:
1) Reducing heat loss through the building fabric – the walls, roof and windows – and cocooning the house in an envelope of insulation and advanced low energy glazing
2) Using renewable energy to supply hot water and electricity
3) Supplying the remaining energy efficiently
4) Addressing lifestyle choices and looking at how the occupant can make a difference.

Favourite feature:

The walls of the house are solid brick, and originally up to 40% of the heat lost from the building was lost through these. Because the house is located in a conservation area, external wall insulation was not allowed due to planning constraints. Therefore internal wall insulation was the only realistic option to reduce heat loss through the walls.

Internal wall insulation can be time consuming and disruptive, requiring the occupants to move out of the property while work is being done. The major innovation of this retrofit is in using the WHISCERS process for the internal wall insulation. WHISCERS uses laser measuring to record the shape of the walls, then the information is transferred to an off-site board cutter, the panels are brought to site and erected in typically 1-1.5 hrs per room. The reduced disruption, mess, noise and installation time allowed the residents (a family of five) to remain living in the house throughout the retrofit programme.

Common questions and answers for this SuperHome

What results did you get from monitoring moisture in the walls?+

100mm of polystyrene was used for internal wall insulation. The results from monitoring for interstitial condensation show that moisture levels are within acceptable limits.

• Membrane Brick: 7-14 (2011), rising to 9-16 (spiking to 19 g/m3) by Sept 2012 – Acceptable value
• Membrane – Plasterboard: 7-15 (2011), rising to 8-15 (spiking to 18 g/m3) – Acceptable value
• Floor, Insulation: 7.4-12.6 spiking to 15 g/m3 – Acceptable value
• Floor, Foam: 0.3-0.6, declining to 0.2-0.3 with spikes to 0.5 g/m3 – Acceptable value
• Floor, Space: 0.9 declining to 0.1 then vanishing from July 2011 to July 2012 and coming back at 0.1 g/m3 – Acceptable value

The monitoring at Bertram St was carried out from Jan 2011 – Dec 2012.

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