Assessment of Zero Energy Prefabricated Accessory Dwelling Units in Support of New Zealand Housing Needs

<p>Problem statement: The demographics of New Zealand are changing and the country is getting older. The literature shows the housing needs of older people are different, and that many would prefer to stay in their existing neighbourhood and age in place. In addition to the shortage of houses, low residential densities, the fast growth of land and house costs over income, and an aging population are all current issues in New Zealand housing. Projections also show the shortage of energy resources and environmental pollution will affect the future of housing, as the housing industry is responsible for over one-third of global energy use and CO₂ emissions. Aim of the research: This thesis aims to design and evaluate the practicality and efficiency of a prefabricated Accessory Dwelling Units (ADU) as a partial response to New Zealand housing needs. Prefabrication was selected as the method of construction as it has been claimed to be more efficient in terms of energy and material use, as well as leading to a shorter construction time and lower environmental impacts. The use of ADUs could increase residential density and add to the housing stock by using existing developed land and infrastructure. ADUs also offer smaller houses within the existing social context, which the literature suggests is the main housing requirement of older people. As a result, the ADU in this research was designed to suit older residents, whilst recognising that it would also be suitable for small households of all ages. Methodology: This research used design as a tool with which to explore the potential of prefabricated ADUs as a contribution to New Zealand housing needs. The design was then tested against housing needs by using Life Cycle Analysis (LCA). This part of the research was conducted in the three phases of life-cycle energy, life-cycle cost, and life cycle CO₂ emissions of the ADU as designed. Results: While the transport limitations pushed the design to be narrow (the maximum allowed load width was 2.55m), the Lifemark accessibility standard asked for doors, corridors, and spaces wide enough to ease the movement of disabled people. Despite these difficulties, it was possible to design an ADU which could be manufactured in New Zealand and transported anywhere in the country without any need for over-dimension load permissions. However, the analysis in the last phase, looking at the ADU during its life span, showed there was no substantial difference between its performance and that traditionally made houses. The results of the analysis suggest that, despite the importance of the construction method, the building energy efficiency, CO₂ emissions and cost, the environmental impact of a house is more dependent on the choice of materials than the method of making it. Future research: The results suggest the importance of further investigation into the choice of materials used to make residential buildings and the effect such choices have on life-cycle impact. There is also a need to seek feedback on the ADU as designed from both potential users and potential manufacturers.</p>

Assessment of Zero Energy Prefabricated Accessory Dwelling Units in Support of New Zealand Housing Needs

<p>Problem statement: The demographics of New Zealand are changing and the country is getting older. The literature shows the housing needs of older people are different, and that many would prefer to stay in their existing neighbourhood and age in place. In addition to the shortage of houses, low residential densities, the fast growth of land and house costs over income, and an aging population are all current issues in New Zealand housing. Projections also show the shortage of energy resources and environmental pollution will affect the future of housing, as the housing industry is responsible for over one-third of global energy use and CO₂ emissions. Aim of the research: This thesis aims to design and evaluate the practicality and efficiency of a prefabricated Accessory Dwelling Units (ADU) as a partial response to New Zealand housing needs. Prefabrication was selected as the method of construction as it has been claimed to be more efficient in terms of energy and material use, as well as leading to a shorter construction time and lower environmental impacts. The use of ADUs could increase residential density and add to the housing stock by using existing developed land and infrastructure. ADUs also offer smaller houses within the existing social context, which the literature suggests is the main housing requirement of older people. As a result, the ADU in this research was designed to suit older residents, whilst recognising that it would also be suitable for small households of all ages. Methodology: This research used design as a tool with which to explore the potential of prefabricated ADUs as a contribution to New Zealand housing needs. The design was then tested against housing needs by using Life Cycle Analysis (LCA). This part of the research was conducted in the three phases of life-cycle energy, life-cycle cost, and life cycle CO₂ emissions of the ADU as designed. Results: While the transport limitations pushed the design to be narrow (the maximum allowed load width was 2.55m), the Lifemark accessibility standard asked for doors, corridors, and spaces wide enough to ease the movement of disabled people. Despite these difficulties, it was possible to design an ADU which could be manufactured in New Zealand and transported anywhere in the country without any need for over-dimension load permissions. However, the analysis in the last phase, looking at the ADU during its life span, showed there was no substantial difference between its performance and that traditionally made houses. The results of the analysis suggest that, despite the importance of the construction method, the building energy efficiency, CO₂ emissions and cost, the environmental impact of a house is more dependent on the choice of materials than the method of making it. Future research: The results suggest the importance of further investigation into the choice of materials used to make residential buildings and the effect such choices have on life-cycle impact. There is also a need to seek feedback on the ADU as designed from both potential users and potential manufacturers.</p>

Urban Compression: Incremental Strategies for Achieving Suburban Densification

<p>Background: Sprawling, car related development dominates and destroys natural landscapes and productive farm land at the edges of urban centres. Yet, suburbs continue to grow outwards to meet New Zealanders’ preferences for stand-alone housing and keep up with increasing housing demand, while existing dwellings are demolished to make way for new developments. Research objectives: This research aims to investigate the implications of building dwellings incrementally to achieve gradual densification within New Zealand suburbs, reducing the need for green field development, and slowing urban sprawl. The objective of this research is to determine how incremental housing strategies could enable suburbs to continue to grow, however in density rather than sprawl, through the design of accessory dwelling units that can be added to existing sites and developed over time. Research method: Built and proposed incremental housing projects are reviewed to determine existing strategies and their suitability for creating buildings that are able to grow over time. Literature is reviewed to identify current preferences and priorities for suburban living, strategies for sustainable suburban development and current provisions within district plans for achieving denser suburbs. Siteless and site responsive architectural strategies for incremental accessory dwelling units are developed through iterative massing and plan studies to generate a wide range of potential solutions at each stage of development, continually reflecting on and progressing with the most successful options. Potential Implications: The development of spatial strategies for incrementally built accessory dwelling units that could facilitate long term densification in the New Zealand suburban context while reducing the need for the demolition and redevelopment of existing residential sites.</p>

Urban Compression: Incremental Strategies for Achieving Suburban Densification

<p>Background: Sprawling, car related development dominates and destroys natural landscapes and productive farm land at the edges of urban centres. Yet, suburbs continue to grow outwards to meet New Zealanders’ preferences for stand-alone housing and keep up with increasing housing demand, while existing dwellings are demolished to make way for new developments. Research objectives: This research aims to investigate the implications of building dwellings incrementally to achieve gradual densification within New Zealand suburbs, reducing the need for green field development, and slowing urban sprawl. The objective of this research is to determine how incremental housing strategies could enable suburbs to continue to grow, however in density rather than sprawl, through the design of accessory dwelling units that can be added to existing sites and developed over time. Research method: Built and proposed incremental housing projects are reviewed to determine existing strategies and their suitability for creating buildings that are able to grow over time. Literature is reviewed to identify current preferences and priorities for suburban living, strategies for sustainable suburban development and current provisions within district plans for achieving denser suburbs. Siteless and site responsive architectural strategies for incremental accessory dwelling units are developed through iterative massing and plan studies to generate a wide range of potential solutions at each stage of development, continually reflecting on and progressing with the most successful options. Potential Implications: The development of spatial strategies for incrementally built accessory dwelling units that could facilitate long term densification in the New Zealand suburban context while reducing the need for the demolition and redevelopment of existing residential sites.</p>

Viewpoint: Turning streets into housing

I argue that wide residential streets in US cities are both a contributor to homelessness and a potential strategy to provide more affordable housing. In residential neighborhoods, subdivision ordinances typically set binding standards for street width, far in excess of what is economically optimal or what private developers and residents would likely prefer. These street width standards are one contributor to high housing costs and supply restrictions, which exacerbate the housing affordability crisis in high-cost cities. Planning for autonomous vehicles highlights the overprovision of streets in urban areas. Because they can evade municipal anti-camping restrictions that restrict the use of streets by unhoused people, autonomous camper vans have the ability to blur the distinction between land for housing and land for streets. I propose two strategies through which excess street space can accommodate housing in a formalized way. First, cities could permit camper van parking on the right-of-way, analogous to liveaboard canal boats that provide housing options in some UK cities. Second, extending private residential lots into the right-of-way would create space for front-yard accessory dwelling units.

A Comparison of Life Cycle Energy and Carbon Impacts for Passive Detached Accessory Dwelling Units and Their Design Implications

Detached accessory dwelling units are a building typology that, when built to passive design standards, can help reduce GHG emissions while addressing the socioeconomic pressures facing many housing markets. Energy performance metrics like those used in passive design standards are based on per unit of floor area and lead to a size-bias against smaller housing typologies. A life cycle assessment of cost-optimal passive house sizes ranging from 230 m² (2,500 ft²) to 30 m² (300 ft²) is performed to understand their total life cycle energy use and GHG emissions implications. Additionally, an analysis using BEopt examines operational energy use for 10 cost-optimal passive house sizes ranging from 230 m² (2,500 ft²) to 30 m² (300 ft²) across all 17 climate zones and examines how cost-optimal passive design changes with house size. The results show that per-occupant energy use and GHG emissions are similar or better for small house sizes and that cost-optimal passive design does not change significantly with house size.

A Comparison of Life Cycle Energy and Carbon Impacts for Passive Detached Accessory Dwelling Units and Their Design Implications

Detached accessory dwelling units are a building typology that, when built to passive design standards, can help reduce GHG emissions while addressing the socioeconomic pressures facing many housing markets. Energy performance metrics like those used in passive design standards are based on per unit of floor area and lead to a size-bias against smaller housing typologies. A life cycle assessment of cost-optimal passive house sizes ranging from 230 m² (2,500 ft²) to 30 m² (300 ft²) is performed to understand their total life cycle energy use and GHG emissions implications. Additionally, an analysis using BEopt examines operational energy use for 10 cost-optimal passive house sizes ranging from 230 m² (2,500 ft²) to 30 m² (300 ft²) across all 17 climate zones and examines how cost-optimal passive design changes with house size. The results show that per-occupant energy use and GHG emissions are similar or better for small house sizes and that cost-optimal passive design does not change significantly with house size.

AGING IN COMMUNITY: A LEGAL MAPPING ANALYSIS OF MASSACHUSETTS MUNICIPAL ACCESSORY DWELLING UNIT ZONING BYLAWS

Accessory-dwelling units (ADUs) are one alternative housing arrangement that enable older adults to remain in the home despite functional decline. Functional decline increases with age making older adults more susceptible to loosing independent housing. Involuntary relocation to institutional care can result in a decline of functional health, reduced life satisfaction, impairment of psychological well-being and increased mortality rate. The majority of older Americans (93%) wish to remain in their home for as long as possible. ADUs function to maintain, stimulate and support an older adult as a means to prevent relocation to an institution. The modified environment coupled with adaptable features maintains and supports activities of daily living (ADL) within a familiar place. Under Massachusetts law MGL c. 40A, the state gives authority to cities and towns to adopt ordinances and bylaws to regulate the use of land, buildings and structures. Restrictive zoning laws limit the ability to construct health-promoting built-environments to age-in-community. All 351 Massachusetts municipalities Accessory Dwelling Unit (ADU) zoning bylaws were coded using the ADU Friendliness Score. Once scored, the 351 municipalities were placed into four categories based off their ADU score; the four categories are poor (0-24), fair (25-49), good (50-74), and excellent (75-100). Eighty-nine municipalities (25%) are in the poor category; thirty municipalities (8.5%) are in the fair category; one hundred and eighty-five municipalities (53%) are in the good category; forty-seven municipalities (13.5%) are in the excellent category. These findings contributed to a model ADU bylaw specific for aging Americans for municipalities to adopt.