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On the job discovery

Sunand Prasad

On the job research provides valuable data. Sunand Prasad describes Penoyre and Prasad’s Retrofit for the Future project that reworked a 1990s house

The low energy strategy for Penoyre and Prasad’s retrofit house includes automatic roof vent and both PV and solar water heating panels.
The low energy strategy for Penoyre and Prasad’s retrofit house includes automatic roof vent and both PV and solar water heating panels.

How can we get going a real market in ‘green’ goods and services with a much bigger total worth than the present low billions? This is the hardest nut to crack if we are to reduce carbon emissions by 80% by 2050. The government is not going to invest at a sufficient scale to pump prime, let alone create, such a market. So the best bet lies in generating consumer demand while creating supply lines that inspire confidence and offer attractive ‘green’ products.

It is often pointed out that the existing stock is the biggest challenge. However it is not readily understood just how different are the operational issues of retrofitting existing buildings, and especially houses, compared to new buildings and infrastructure projects both new and upgrade. The technical issues in retrofit are different from new-build but the bigger issues are in project finance, consumer culture and the regulatory environment. Domestic retrofit relies on individuals wanting to make the changes, deciding it’s worth it, having confidence in the payback on investment, finding the money, and accepting the inevitable disruption.

Money and aesthetics
The Technology Strategy Board’s Retrofit for the Future programme has been a very welcome initiative aimed at prototype development, rare in our industry. Its main focus is to implement and monitor carbon lowering technologies in homes, both through energy efficiency and renewables. It has made available around £150,000 per house split about equally between implementation and monitoring. If that sounds a lot, consider the costs of prototype development in manufacturing. A single car for sale at £10,000 may well have a few hundred million spent on development – several hundred times its market price. We need to retrofit around 25 million homes at a ‘deep retrofit’ cost of £15-25,000 and need to invest in finding tested, workable solutions.

In our Retrofit for the Future project at 61 Warwall in Becton, east London, carried out with East Thames Housing Group (ETHG), we explored the financial and cultural dimensions of retrofit and used innovative low carbon technologies. We wanted to see what value could be generated through retrofit in addition to the savings on utility bills. People invest in their kitchens and bathrooms for the increased pleasure in living in the home. They invite their neighbours round and discuss the fine points of extractors and lighting. It is unlikely anyone will be asking neighbours round to show off their insulation or mechanical ventilation heat recovery, not least because there is little to see. However, passive energy efficiency measures can have a big impact on space and natural light. We wanted to use such design propositions to make the home more delightful to live in.

After talking at length to the residents at 61, getting an understanding of their lifestyle and details such the extensive use of a tumble dryer, we proposed that the space above the centrally placed stair be opened up and given a large remotely openable roof-light. A new ‘left foot right foot’ stair takes you up to a new attic level and, despite the original trussed rafter construction, creates a great deal of storage or play space as well as a new landing for home study and a space for drying clothes. The ambience of the house is transformed making it feel more generous and comfortable. 

Sustainable technologies
‘Green’ technology features strongly in the design. High levels of external wall and roof insulation were installed. Because the planners wanted no alterations to the appearance of the house from the street, we could not insulate the front externally and had to minimise raising the profile of the roof, despite 200mm of insulation in the roof line and solar panels. A number of external wall and roof insulation options was researched. The chosen solution has external insulation and render at the back and internal insulation and plaster at the front (necessitating a kitchen refit, which the ETHG decided to fund separately).

A triple glazed openable roof-light provides natural ventilation through passive stack effect at the centre of the house.  The roof-light operates automatically according to temperature and humidity and closes automatically when it rains, although there is also a manual override. However, should the tenants not use the natural ventilation, there is also an innovative ‘breathing’ roof designed to dissipate moisture and avoid condensation.
Natural insulation products, wood fibre slab and hemp fibre quilt were used, which have excellent moisture permeability, good thermal mass and low embodied CO2. An ‘intelligent’ vapour control membrane provides allows moisture driven inward by the weather to dry as well as the more usual outward migrating moisture.
Floors are insulated with UK manufactured vacuum insulation panels. These give ultra high thermal performance for only minimal (25mm) rise in floor level, and avoid the disruption of removing floor screed. The installation includes puncture protection.

New triple-glazed windows incorporate opening ventilation panels with security louvres and fixed lights.  This integrated solution to the problem of combining ventilation with security is a new product developed in collaboration between Penoyre & Prasad and window manufacturer Nordan.

Photovoltaic panels are placed on the front roof and direct solar water heating panels on the rear roof. White goods have been upgraded.

Cutting costs, adding value
These measures are projected to reduce total CO2 emissions by 80% compared to the 1990 Buildings Regulations baseline, down to 17kg/m2.
The design team produced an illustrated user guide explaining the principles and operation of all the energy saving features and equipment and used it for the induction of the residents.  The project is undergoing two years of energy and environmental monitoring with four post-occupancy evaluations to be carried out over the period by Oxford Brookes University.

The residents of 61 Warwall stayed put through out the works and have been delighted not only by the lower bills but also their lighter, brighter, airier home. At the same time it is estimated that the value of the house (disregarding the impacts of location) has increased by £20-25,000, helping to offset some of the cost of the works. We are now working on how the project can lead to a bigger programme across the estate. 

A Dutch airer instead of a tumble drier in the new attic level gives an immediate saving in running costs.
A Dutch airer instead of a tumble drier in the new attic level gives an immediate saving in running costs.

Sunand Prasad is past president of the RIBA and co-founder and senior partner of Penoyre and Prasad. 


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