LEDA developed an approach to “Lean Design” a few years ago at around the same time as the term “Lean Construction” got its first hearing. We were looking to highlight our way of developing a design strategy that offers good quality and energy efficiency at a cost our clients could afford. One of the often repeated waste reduction methods Toyota used was “Making only what is needed, when it is needed, and in the amount needed “. Translating this into a design principle means to us forsaking the traditional “belt and braces” approach to services design and adopting the following design criteria:
Making buildings work for themselves. Collaborating with the rest of the design team to create buildings that provide good natural ventilation, daylighting and comfortable internal climate with the minimum input from mechanical and electrical services. LEDA don’t pretend to be unique in this area – and David Cheshire made the same point in the WRAP supplement – but after nearly two decades of providing advice to design teams on creating low energy buildings I am still able to be surprised by the widespread lack of understanding in this area.
Establishing sensible design margins. We see lean design as meaning avoiding excess but not accepting under-performance. Although organisations such as CIBSE do provide a wealth of design criteria for engineers, some areas still retain an aura of “smoke and mirrors”. Diversity of use (whether electricity, heat, hot water or hot air) is one such area where LEDA have had to establish lean design by using standards from other countries and the knowledge of specialists with a working experience in particular fields. The design criteria for community and district heating systems is a good example of where assumptions about diversity play a key role in the design. We have used the Danish Standard DS439:2009 for residential schemes when using interface units with hot-water heat-exchangers for over fifteen years without any problems but have had this approach rejected by client’s consultants in the past because it has a “DS” rather than a “BS” prefix. Whilst using a diversity factor of 0.15 for simultaneous hot-water demand from a block of 50 flats may seem dangerously low, experience has shown it works well in practice. Conversely the use of more conservative diversity factors will lead to lower system efficiencies (due to larger pipework and boilers) as well as higher capital costs.
Other examples similar to those proposed by WRAP to improve resource efficiency, include avoiding a blanket 500lux approach lighting designs (“as much light as is needed , when it is needed, where it is needed.”) and making use of existing services where appropriate.
A couple of examples of community projects with limited budgets illustrate the lean design in practice:
HEART is a community owned and run enterprise and arts centre in Headingley. The client’s brief was to transform a disused Victorian primary school into a welcoming space for a wide variety of activities in the most environmentally sustainable way.
The building had to be refurbished to a very tight budget without compromising the functionality of the building. The design incorporated the use of a single boiler instead of 2 or more, and re-used a relatively new fire alarm and distribution boards . An effective passive ventilation strategy for the open plan offices was agreed with the architect that required little more extra expense than the addition of north-facing opening skylights, and this eliminated the need for air-conditioning.
The project was completed to a tight budget, and grant funding was obtained for photovoltaic panel and solar hot-water installations. Ongoing monitoring of the building shows good internal climate and below-benchmark energy use.
Unity House is a Grade 2 listed building in Wakefield built in 1867 for the Wakefield Co-operative Headquarters which has been mostly derelict for 10 years. Unity House (Wakefield) Limited have been campaigning to restore the building since 2011, and have attracted funds from various sources
The refurbishment project provides for a multi-use 600-seater hall, catering kitchen, offices, exhibition and meeting spaces
This was initially tendered as a Design and Build project mid-2013 and came in 50% over budget, with a best tender return over £900,000 for building services installations.
• LEDA were appointed to prepare re-tender documents to bring in the M&E costs to under £600,000, whilst retaining quality of design suitable to each type of area and still achieving BREEAM “very good”. The re-design included:
• Heating and Hot water: The original performance specification called for four boilers, two hot water cylinders and a standard hot-water secondary circulation system. This was changed to a twin-boiler installation with direct compensation for heating and point-of-use water heaters which eliminated the need for central hot-water plant and distribution pipework.
• Cold Water: A check on local mains water pressure showed that the cold water booster set and tank in the original specification was not really required.
• Ventilation: The main hall has the remains of a patented Victorian natural ventilation system, including original ductwork in the roof-void which is being re-used to create a passive-assisted extract ventilation system with additional dampers and fan.
• Electrical supply: The electrical supply requirements were paired down to the absolute essentials, with low energy catering equipment, lighting, fans and pumps, and the overall energy requirements for the building reduced. This, along with some sensible diversity calculations has reduced the electricity connection costs by 90% (by avoiding the cost of a substation), and is expected to reduce the contractor’s builders work requirement by a similar margin.
• Lighting: Clear specification of carefully selected quality lighting and lighting control, with detailed design and quantities shown on the drawings has halved the installed cost of the lighting, whilst retaining quality and energy efficiency.
More than one re-tender quotation for mechanical and electrical services cane back at below £600,000 and the refurbishment is now well underway. On a purely financial level, the deliberate reduction of risk elements and potential uncertainty in the performance specification helped contractors to price competitively.
Matthew Hill from Leeds Environmental Design Associates discusses the concept of Lean Design – published in CIBSE Journal June 2014.