Lifetime Housing using Generative Design tools
The research proposes the building of half a house akin to historic ‘back-to-back’ housing, with the remaining ‘half’ built over the remaining lifetime of the owner, providing versatile and adaptable room and spaces for the life changes of the owner. The method is based on a unique Autodesk Generative Design definition providing a multi-objective design generation algorithm for creating design iterations for the unbuilt future ‘half’. Each homeowner is able to then navigate the thousands of design options generated to evaluate the potential cost of changes to the fabric (linked to the SPONS cost guide) of the house based on their individual lifetime changes; marriage, children, illness, dementia etc, to improve financial forward planning. The work goes on to evaluate the effectiveness of the algorithm output through a series of comparisons with established ‘lifetime home’ case studies.
Keywords: generative, housing, modular, lifetime, planning, automated, algorithm, costing, house
The UK population is growing older– now almost 20 million households are over the 55-year bracket, and those aged 85 and over are predicted to double in the next 20 years. In parallel with an ageing population, the affordability of housing has led to a growing crisis for first time buyers, with those in full time employment typically spending 7.8 times their workplace annual earnings purchasing a home [1]. There are 1.6 million renters who are able to buy, but are unable at present due to the prohibitive cost of large housing deposits [2]. As a result, levels of homeownership have fallen in England from 71% in 2001 to around 63% today. This has particularly affected young people: in 2001, 55% of 25-34-year olds were homeowners in the UK. That figure now stands at 35% and for the next age bracket (35-44), there has been a reduction in homeownership rates from 73% to 61% [3].
The desire to live affordably and inter-generationally needs to be met by appropriate housing options. Choice implies addressing crucial barriers: inadequate space and insufficient options were named in a survey of 2,000 adults as one of the biggest barriers to intergenerational living. Additional issues encompassed uncertainty about future health and employment status and changes to family unit sizes. To address these problems, this research proposes the building of ‘half a house’, akin to one half of traditional back-to-back housing. The unbuilt ‘half’ can then be designed through generative optioning of layouts to explore potential costs with a view to forward financial planning.
To evaluate the methodology, the project considered the design of a UK street in Holbeck, Leeds adjacent to existing streets of back-to-back housing. The method proposed the contextual imitation of the existing structure and tectonic of the back-to-back streets, constructing just one ‘half’, with the other left ‘open’ and unbuilt to provide for future lifetime changes or intergenerational living through financial investment. The advantage of this method is that home owners need to raise a much smaller initial deposit and mortgage. The additional land allows space for expansion, and the generative method can help determine the visual, spatial and financial implication of future life style changes.
This approach is described in the image below where the ‘green’ future phase indicates how a home owner might choose to build on the existing ‘base build’ to provide a larger living room, two additional bedrooms and a roof terrace. The method allows the user to index contemporary and projected financial costs against quantities for any iterative layout change through the generative software and cost databases.
The project utilises Autodesk’s Dynamo and Generative Design integration with Revit. Dynamo was chosen over Rhino’s Grasshopper due to its improved integration of full building systems through Autodesk’s comprehensive Building Information Model (BIM) system. This allowed for a detailed take-off of quantities of materials for cross reference with SPONS financial data providing an agile and visual interface.
In order to begin the process optioning iterations of house layout, multiple layouts across three storeys were created in AutoCAD. Each floor plan would need to provide compliant vertical circulation and services e.g. aligned structure and stairs, and to ensure that access is provided to all rooms regardless of room arrangement. This led to the creation of the following numbers of room iterations: ground floor 71 possible iterations of layouts, first floor 84 possible iterations of layouts, second floor 71 possible iterations of layouts. In combination, this provides 423,444 possible layouts, but it is worth noting that some of these may not be useful on the basis of repetition across multiple floors e.g. bedrooms on all floors (Figure 3).
The research provides a methodology that successfully automates a multi-objective design generation algorithm for creating design iterations for multi-generational lifetime homes. Each homeowner was able to navigate design options generated to evaluate the potential cost of changes to the house based on their individual lifetime changes in order to improve financial forward planning. The work goes on to evaluate the effectiveness of the algorithm output by testing against the briefing requirements of a diverse multigenerational set of families across six houses. The results confirm that the method provides automated plan designs leading to improved outcomes for forward financial planning. User evaluation of the script demonstrates the method has potential to deliver an innovative and architecturally successful outcome for first-time homeowners who wish to plan for a lifetime home.