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LILAC (Low Impact Living Affordable Community): Co-housing project using sustainable construction methods with straw bales

Wyróżniony Przypadek February 2015
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LILAC (Low Impact Living Affordable Community) is the UK's first affordable, ecological cohousing project with a pioneering methodology:

  • Encourage living as lightly on the earth as possible
  • Address the need for affordable housing
  • Have a positive impact on the surrounding community


This project comprises a community of 20 households and a common area/house located on an old school site in Bramley, West Leeds. The design of LILAC mixes private dwellings and shared facilities. The common house will include shared facilities like a kitchen and dining area, laundry, multi-purpose room, guest room and workshop. The buildings have been made with a prefabricated straw bale construction system assembled by the LILAC members using locally sourced straw. The excellent insulation properties of straw, combined with airtight construction, triple glazing and heat recovery ventilation, reduce energy and CO2 emissions to a minimum.  The community owns a solar thermal and photovoltaic system which also reduces their energy consumption and CO2 emissions further. A sustainable urban drainage system is available to minimise water use and the surface runoff is used for irrigation in the garden areas as well as a source of water for a nature pond.


Project management

LILAC Mutual Home Ownership Society Ltd.



Main contractor: Lindum Group

Architect: White Design Associates Ltd.

Thermal Consultant: ProGETIC SCP


LILAC's sustainable objectives

  • Reduce impact on the environment:  LILAC aims to make each home carbon negative meaning that they able to return to the national grid as much power (and more) as they use over the course of a year. The overall ecological footprint of the neighbourhood has created positive changes in the way the residents live by using shared facilities in the common house which reduces energy use and saves money for residents.   


  • Respond to the housing crisis in the UK:  A new affordability model has been created in the form of a Mutual Home Ownership Society (MHOS) which is an equity based leaseholder scheme. The MHOS will ensure that the cost of the homes remains permanently affordable and doesn’t follow the extremes of the housing market. The cost of the project is divided into equity shares. These are owned by members and financed by the payments members make each month, which is equivalent to 35% of their net household income. After some deductions, members can take their equity with them on leaving. A financial assessment and payment of a deposit is needed to join the Society.


  • Make a positive contribution to the surrounding community:  The site design is based around a car-free home zone, communal gardens, green spaces, areas for growing food and ample cycle storage. There will be limited on-site parking.


Time schedule

Pioneering preparation: December 2006 preliminary plans made to start a cohousing group

Design: 2009 - 2010

Construction: 2011 - 2012

Delivery: March 2012


Surface areas and use

0,77 Ha total site - 1692 m2 total constructed area :

1476 m2 usable floor area in flats and houses: 20 units located in a variety of types and sizes of buildings:

  • Block of flats A1 (1 bedroom 2 person flat): 6 flats of 48 m2
  • Block of flats A2 (2 bedroom 4 person flat): 6 flats of 71 m2
  • Block of houses B1 (3 bedroom 5-6 person house): 6 houses of 90 m2
  • Block of houses B2 (4 bedroom 6-8 person house): 2 houses of 111 m2


125 m2 usable floor area in the commons house next to the main entrance

Common area (house) and gardens

Private garden areas and cultivation plots

2 car parks (5 each)

3 bike sheds (40 spaces)


Construction and exploitation costs

Land cost: 700.000 €

Renewable energy system cost: 38.471 €

Estimated cost for works: 4.130.000 €

  • Reference estimated cost to construct a straw bale house: 1288 €/m2
  • Reference estimated cost to construct a straw bale house by self-build: 981 €/m2

Households pay approximately 35% of their yearly net income (based on equity shares).

  • Funding: Lenders can support the project in a simple way for the members of the community (loanstock). Each loanstock is placed within the co-operative for a fixed period of time with carried  interest. The lender is not able to make any decisions in the organisation, it is only a form of a loan which is repayable in full on its ‘closing date’.


Energy consumption

  • Primary energy need: 62,78 kWh PE/m2y
  • Final Energy: 104,95 kWh FE/m2y (
  • GHG in use: 10,60 KgCO2/m2y - In contrast to a newbuild home (according to report 'New Tricks With Old Bricks' from the Empty House Agency) which produces around 50 tonnes of CO2, a home built using straw bale as insulation can store up to 12.25 tonnes of CO2 (citation:


Envelope performance

U-Value wall: 0.19 W.m-2.K-1

U-Value roof: 0.15 W.m-2.K-1.


  • U-values improve the current building regulation requirements in the UK for walls at 0.35 and roofs at 0.25. The airtightness of the panels is also very good. The combination of high levels of insulation, airtightness and triple glazing is the key to a significantly reduced energy consumption and this has been demonstrated in the results A 90% reduction in energy consumption has been achieved and reflected in the bill.  The energy consumption is that compared to a local single house.


  • The prefabricated panel system (ModCell) has been used in the construction. They are load bearing, storey height, glulam timber framed panels which are filled with locally sourced straw bales (2,5 tonnes per each panel). These panels are not manufactured in a conventional factory. The barns of local farmers which are referred to as ¨flying factories¨ are used to produce them. This also includes baling the straw. An important consideration is that they are preferably as near to the construction site as possible.  This concept benefits the local economy as well as reduces emissions. The panels have been lime rendered on both sides, providing the internal and external finish. After 10 days, the lime render has cured, therefore making it possible to transport them.  The panels are then installed on-site.  Once assembled, a cedar cladding is applied to cover the outdoor structural frame elements, floor and roof levels.


System performance

  • Heating system: Gas boiler
  • DHW system: Gas boiler integrated with solar thermal system
  • Cooling system: No cooling system
  • Ventilation system: Double flow heat exchanger
  • Renewable systems: Solar photovoltaic and thermal systems
  • Renewable energy production:  30%


Awards won

  • 2degrees Champions Awards 2014: Shortlisted and commended in the category of Building or Property Project.
  • Green Building Solution Awards 2014: Winner in the category of Materials & Building Systems due to Modcell, the strawbale insulation panel.  Second in the category of Efficient Building due to their project.
  • 25th Leeds Architecture Awards 2013: Commendations - Young People's Review 2013 for new building and to Landscape categories.
  • Place Making Awards 2013: Finalist in the contest.
  • Build It Awards 2013: Winner in the category of Best Community or Group Self Build Initiative
  • LABC Building Excellence Awards 2013: Finalist in the contest.
  • Constructing Excellence Awards 2013: Winner in the category of Legacy Award. 


The LILAC homes have received UK Energy Performance Certification (EPC), according the SAP 2009 assessment procedure.

(Cost data includes the specific construction costs of the homes + fees & site preparation, excluding parking and urban sewerage).




Lessons learnt

The overall ecological footprint of the neighbourhood has created positive changes in the way the residents live by using shared facilities in the common house which reduces energy use and saves money for residents.

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