Footprint

61 Warwall, another of the Technology Strategy Board’s Retrofit for the Future projects is a mid terrace, two storey, three bedroom house on the Windsor Park Estate, London Docklands.

The house was originally built in 1992, with masonry cavity walls, double glazing and a pitched roof with loft insulation. Penoyre & Prasad have now made the necessary changes to meet the target of an eighty percent reduction in carbon emissions from 1990 standards.

Residents remained in place throughout the build process creating various challenges. Work had to be programmed carefully with provision for movement and storage of the residents’ possessions.

The architects aimed for minimal demolition and removal of waste from site. The existing ground floor construction was retained and insulation was added. The solid ground floor was overlaid with vacuum insulation panels. These provided a high level of thermal efficiency for a minimal 25mm increase in floor level.

The light well has also provided a space for clothes drying

Rooflights in the light well are part of the natural ventilation strategy

One of the largest changes to the house has been the introduction of a light well. This brings natural light into the previously dark centre of the house whilst providing natural ventilation. An opening rooflight at the top of the light well provides the exhaust for stale warm air.

The natural ventilation strategy

Ventilating panels within the windows

Fresh air enters the house through ventilating panels by the new triple glazed windows. Security louvres to the front of the panels allow the residents to leave them open even when the house is not occupied, providing daytime ventilation. These panels have been developed specifically for this project through collaboration between the architects and Nordan. The natural ventilation strategy for the house also incorporates the use of a real time monitoring system, giving the tenants information on whether the windows and louvres should be opened or closed. The monitoring system will be linked to CO2 and internal and external temperature sensors to ensure that comfort is optimised without excessive heat loss.

The project features a breathing roof, designed to future proof the project. Should the residents decide not to use the natural ventilation; this breathing roof will allow moisture to be dispersed preventing condensation. Natural insulation products, hemp and wood fibre, were chosen for their properties of high thermal mass, moisture permeability and low embodied CO2. An additional 125mm of insulation has been incorporated between the joists with 350mm above, giving an increased u-value of 0.1W/m2K.

Building facts:

• Floor area: 83.7m2
• Annual space heating demand: 40kWh/m2/yr
• Annual CO2 emissions: 16.6KgCO2/m2/yr
• Primary energy requirement offset by renewable energy: 88kWh/m2/yr
• Annual CO2 emissions offset by renewable energy: 17Kg/m2/yr
• Existing air permeability: 5.62m3/hr/m2 @ 50pa
• Target air permeability: 3.0m3/hr/m2 @ 50pa
• External wall u-value: 0.15W/m2K
• Ground floor u-value: 0.15W/m2K
• Roof u-value: 0.1W/m2K
• Glazing u-value: 0.76W/m2K
• Door u-value: 1.0W/m2K

Energy use before retrofit:

• Electricity: 3303kWh/yr
• Gas: 11983kWh/yr
• Primary energy requirement: 263kWh/m2/yr

Predicted energy use after retrofit:

• Electricity: 1455kWh/yr
• Gas: 4756kWh/yr
• Primary energy requirement: 109kWh/m2/yr

Estimated project costs:

• Building works: £72,570
• Energy and environmental monitoring: £9,650
• Total: £82,220

Project team:

• Client: East Thames Housing Association
• Architect: Penoyre & Prasad
• Mechanical and electrical consultant: XCO2 Energy
• Structural engineer: Osborne Edwards
• Contractor: Lakehouse
• Monitoring consultant: Professor Rajat Gupta of Oxford Brookes University

Read more about this project, here.

See another article on Footprint about a recent talk on Retrofit for the Future, here.

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