This report outlines strategies to help meet the demand for more homes in Fairfield County and more housing choice in neighborhoods that are largely comprised of single-family homes. We focus on two main options for tapping into new housing: accessory dwelling units and conversions (duplexes or triplexes). Currently there are approximately 8,450 single-family parcels with an ADU or a conversion in Fairfield County. These secondary or tertiary residences add up to 9,000 units in the county, approximately 4% of the total single-family housing stock (or 2.5% when considering multifamily buildings as part of the total supply).

ADUs and conversions can come in various shapes and sizes. Often, ADUs make use of existing structures in the yard of single-family homes such as detached garages and sheds. Attics, basements, or attached garages can also be retrofitted to create an ADU or an additional dwelling unit in the form of a duplex or triplex.

Legislative Overview

The recent passage of HB 6107 demonstrates growing recognition of the need to incentivize more housing choices in Connecticut and the role that housing policy must play in facilitating social and economic benefits.

Municipalities may opt out of this provision, but it is difficult to do so, requiring a two-thirds vote of both the zoning commission and legislative body before January 1, 2023. The restrictions documented below portray the regulations that could remain in place if municipalities choose to opt out of Public Act 21-29.

Zoning Restrictions on ADUs

New housing construction in Fairfield County and throughout most of the suburbs within the tri-state area has been greatly limited by low density and restrictive zoning regulations. The costs of overly-restrictive zoning are increasingly well-understood. These costs—all of which are present in Fairfield County— fall into five categories.

Restrictive Zoning:

1. makes housing less affordable
2. makes the economy less productive
3. exacerbates income and racial inequalities
4. imposes increased environmental harms
5. limits the types of housing available for different incomes and living arrangements, including at different stages of life

Prior to Public Act 21-29 almost 40% or 91,000 single-family residences in Fairfield County were regulated by a zoning district that prohibited ADUs. Depending on specific conditions, less than a third of single-family residences in the county were allowed to have an ADU as-of-right, and the remaining 28% were allowed by special permit only.

Scholars have known for years that there is more to zoning than simply number-of-unit requirements - or in the case of ADUs and conversions - making them legal or not. To provide more in depth analysis we factored ADU zoning variables - as compiled in Desegregate Connecticut’s Zoning Atlas.

Individual zoning districts in Fairfield County have combinations of variables regulating ADUs. These fall in three categories: permitting, occupancy, and physical requirements. To measure overall restrictions (prior to the enactment of Public Act 21-19) we aggregated the variables into a zoning index, where the level of ADU zoning restrictiveness is based on the cumulative number of requirements imposed by each district.

After combining the zoning variables into an index, we compared the level of restrictions imposed by each municipality. These restrictions portray the regulations that could remain in place if municipalities choose to opt out of Public Act 21-29. Given that Stamford fully prohibits ADUs entirely, it would lead the list in being the most restrictive. Based on the combination of permitting, occupancy, and physical requirements, the municipalities of Danbury, Bridgeport, and Stratford also rank high in the average restrictions score. Even though these municipalities allow ADUs in some instances, the vast majority of their single-family housing stock is regulated by restrictive zoning measures.

Although zoning in municipalities like Norwalk, Fairfield, and Greenwich allows for ADUs as-of-right on a significant share of single-family parcels (regulating over 10,000 units in each case and scoring a more average restrictions index), in practice, other zoning variables in these municipalities create significant barriers that often deter ADUs from actually being created.

Similar trends can also be observed in Trumbull, Stratford, and Newtown. These municipalities all allow ADUs on a significant share of their single-family parcels, but they are only allowed through special permits - adding time and costs to the process. Most localities also have ADU occupancy requirements, which means the owner of the primary residence must occupy the accessory unit. Norwalk, Fairfield, Greenwich, and Trumbull all have zoning restrictions that require owner occupancy for ADUs, regulating more than 10,000 single-family parcels per town. The exceptions to ADU owner occupancy requirements are in Newtown, Darien, New Canaan, and Weston. Finally, in terms of dimensional criteria most municipalities fully restrict ADUs to the primary structure (within the existing building envelope - with no outbuildings or detached structures allowed). Trumbull, Stratford, Shelton, Ridgefield, and Fairfield have the highest number of single-family parcels where ADUs are restricted to the primary structure. The main exceptions to this rule are in Norwalk, Greenwich, Westport, and Newtown.

Fairfield County is the most populous county in the state. Its population represents a little over 25% of Connecticut’s overall population, is one of its fastest-growing counties, and is closest to the center of the New York metropolitan area. The county contains four of the state’s largest cities–Bridgeport (1st), Stamford (3rd), Norwalk (6th), and Danbury (7th)–whose combined population of 433,368 is nearly half the county’s total population.

Land Use

96% of residential land in Fairfield County is classified as single-family.

Of the approximately 430 thousands acres of land in Fairfield County, almost 80%, or 338 thousand acres, is classified as some form of residential use. The largest cities contain the lion’s share of multifamily buildings and middle density housing (attached units or row houses), but these represent only 4% (13,000 acres) of the county’s overall residential land. The majority of residential land is classified as either large residential detached single-family houses (42% or 145,000 acres) or rural residential with some agricultural uses (43% or 145,000 acres). The prevalence of low density housing in the county is also reflected in land cover, where more than 72% of the land is undeveloped open space.

These land use patterns in Fairfield County suggest that public policy is encouraging and subsidizing sprawl, which - intentionally or not - has negative economic, social, and environmental impacts. Studies have found that the cost of building infrastructure and providing services is proportionate to how far apart homes are located. It has also been estimated that sprawl costs the U.S. economy more than $1 trillion each year.

Efficiencies compound in a favorable way when municipalities grow in more compact patterns. As more housing units are built along a road or sewer line, the capital cost of infrastructure and maintenance per household decreases. This has been demonstrated by calculating the costs of infrastructure per capita, and looking at the correlation between travel distances and the cost of providing services such as transportation, education, energy consumption, water, and solid waste, among others. Furthermore, recent evidence strongly suggests that increasing the density of major cities could help lower GreenHouse Gas (GHG) emissions that cause climate change.

Access to transit

Sustainable transport systems are crucial for underpinning the economic performance and prosperity of regions and nations in the 21st century. More compact development is dependent on the availability and access to public transportation. At the same time, more density enables and justifies greater investments in transit infrastructure. This virtuous cycle not only helps reduce dependency on private vehicles - a major source of pollution and environmental degradation - but is a key factor in enabling the economic and cultural success of metropolitan areas across the world, perhaps most notably the New York metro region.

While several municipalities in Fairfield County are underserved by transit options, there is a surprisingly high number of low density residential areas that are well served by transit: More than 105,000 single-family units are served by a combination of either rail or bus lines, and almost 33,000 units are served by both. Bridgeport ranks the highest in both share and total number of single-family residences served by transit with over 17,000 units, followed closely by Norwalk and Stamford, and to a lesser extent by Greenwich and Danbury.

Property Values

More than half of homes in the United States are currently selling above list price. The Case-Shiller US National Home Price Index has been steadily increasing over the past decade, and has been growing even more rapidly throughout the pandemic. At the national level there aren’t enough homes to meet the demand for would-be homeowners, and there aren’t enough homes to meet the demand for renters.

The housing market of the tri-state region, including Fairfield County, has experienced similar patterns. Throughout the previous decade and leading up to the pandemic, suburbs were building less housing, especially in southwestern Connecticut, Long Island, and the Hudson Valley. These places were also accommodating less of the metro area’s overall population, economic, and housing growth.

With less new construction, and now a decreasing supply of available housing for purchase, these suburban areas are less well equipped to accommodate current increases in demand. This is in turn exacerbating regional housing pressures and heightening the housing affordability crisis.

By the end of 2020, housing sales (a proxy for demand) in these areas accelerated sharply, prices were higher, and inventory was down year-on-year. Southwestern Connecticut in particular saw the greatest correlation in the region between a decreasing inventory, increasing sales, and a growing median list price.

With pandemic-induced demand these factors have greatly distorted the market value of single-family residences, with inequitable consequences. While rising home prices in Southwestern Connecticut can be viewed as an indicator of economic strength and market recovery, this ​“strong housing market” has further exacerbated the housing affordability crisis and put pressure on both the sales and rental markets. An increase in demand for housing together with a constrained supply has driven up both home prices and rents, making it even harder for lower income workers to afford housing in Fairfield County.

While the mean market value of a single-family property in Greenwich surpasses $1.5 million, almost half of the overall value is coming from the land, and the balance from physical improvements. Similar values and proportions are documented in Darien, New Cannan, and Westport, where the mean property values of single-family homes all surpass $1 million dollars, and in all cases almost half of the value is derived from the land. On the other hand, in municipalities like Newtown, Shelton, Sherman, and Bridgeport where mean property values are only a fraction of those in the stronger market areas (between $200,000 - $300,000), the value of the improvements constitutes the bulk, up to 70%, of the total property value.

The land to improvement ratio, defined as the assessed value of the land without improvements, divided by the total assessed market value (including physical improvements), can be used as an indicator to inform where and when it makes financial sense to provide assistance and subsidies to property owners seeking to build an ADU or a conversion, or incentivizing their construction based on the annual depreciation of single-family buildings. In weaker markets where the value of the improvements far exceeds the value of the land, financial incentives will be an important tool in stimulating creation of ADUs and conversions. In general terms, areas with high property values need subsidies for ADU creation less than areas with low property values.

The land to improvement ratio can also be used to inform land value capture mechanisms and tax property programs, aimed at funding future infrastructure and transit improvements.

The housing stock in Fairfield County reflects the zoning and land use patterns described above, and documented in greater detail in RPA’s Fairfield County Housing Needs Assessment. In this section we focus on the various types of single-family residences.

Single-family residences dominate the landscape throughout Fairfield County, representing nearly two-thirds of all the housing supply in the county. Most of these single-family units are classified as large detached homes on lots larger than 5,500 square feet. This typology includes over 206,000 units and constitutes 88% of the county’s total single-family housing stock (or approximately 56% of the total housing stock - including multifamily). Stamford, Norwalk, Fairfield, Greenwich, Bridgeport, Danbury, Stratford, and Trumbull have the largest share with more than 10,000 units of large single-family detached residences each.

Attached single-family residences are more common in the larger cities and towns in the form of historic row houses. These are found in Stamford, Bridgeport, Danbury, and Stratford (with 2-3,000 units in each municipality) and to a lesser extent in Norwalk, Greenwich, Fairfield, Westport, and Trumbull (each ranging a couple hundred to 1,700 units). However, taking the county as a whole, attached single-family units only account for 23,000 units, representing just 9% of the county’s total single-family stock.

Small single-family detached units (on lots smaller than 5,500 square feet) are present in some of the largest municipalities, but scarce throughout most of the county. Bridgeport has the largest concentration of single-family homes on small lots with 1,500 units, and is followed by Stamford, Norwalk, and Greenwich with a few hundred units each. This typology is infrequent throughout the rest of the county, rarely surpassing 100 units per municipality. Small single-family detached units only account for 5,000 units in total, representing just 2% of the county’s single-family housing stock.

Some parcels classified as single-family already have existing accessory dwellings, duplexes, and in some cases triplexes on them. These secondary residences account for 9,015 units in Fairfield County, which is approximately 4% of the total single-family stock (or 2.5% when considering multifamily buildings as part of the total supply). While these several thousand units represent only a small percentage of the County’s total single-family housing stock, they set a precedent and help demonstrate that ADUs and conversions can play a more significant role in the county’s housing supply mix.

Norwalk, Bridgeport, and Danbury have the highest number of single-family lots with secondary residences, each with over 1,000 units. In these same municipalities the average number of units per single-family parcel ranges between 2.03 and 2.12 units, suggesting that more than one accessory dwelling unit (or in some cases triplexes) exist on each lot. Secondary units in single-family lots are also present in Stamford, Fairfield, Stratford, and Greenwich, ranging from 590 to 975 secondary units in each municipality. The remaining secondary units are scattered throughout the county, with a couple hundred units within each municipality, and in some cases just a handful (Easton, Weston, and Sherman).

The lack of housing diversity points to the need for more housing that meets the needs of more people at different incomes, stages of life, and abilities, strategically targeted in ways that support the people who need it the most. However, the lack of standard accessible unit tracking and data makes it difficult to get a clear, comprehensive picture of the accessible housing supply in the state and county. This information gap is even greater for the housing typologies discussed in this report. While some sources report secondary dwellings, existing data does not make a distinction between ADUs and conversions, or the number of secondary units (duplexes or triplexes).

Aspirational Vision Scenario

This scenario would also help narrow the gap between the housing available in Fairfield County and the housing needed by the county’s changing demographics. ADUs and conversions created under this scenario would offer additional housing alternatives for a broader constituency including single young people, couples without children, people who work in communities where they cannot afford to live, the many empty-nested baby boomers, and others, all of whom make net contributions to a town’s tax base.

This scenario assumes that municipalities adopt the new minimum requirements legislated in Public Act 21-29 and where pertinent, additional zoning changes that go further to facilitate ADUs and conversions. Future zoning regulations and supporting programs offering financial and technical capacity would take into account the size of single-family residences, their proximity to transit, and their market values (including land and improvements) to inform necessary regulatory changes and creation of new programs.

In our analysis, we factored the availability of physical space by distinguishing single-family residences that have attached and detached structures, as well as by large and small single-family lots. In general, and absent arbitrary dimensional criteria, more available space means greater design and construction options to build a variety of ADU and conversion typologies.

This scenario assumes future zoning code amendments make clear that existing dimensional criteria and lot coverage for the principal dwelling on the parcel are substantially less than that required for the accessory dwelling. Similarly, it assumes dimensional criteria does not compound into the calculations used for the ADU or conversion.

This scenario also assumes that parking regulations - a major impediment to ADUs, conversions, and new housing in general - are relaxed in proportion to accessibility of transit modes. It assumes that in neighborhoods that are served by rail and bus services - and where single-family residences are the dominant housing typology - parking minimums will be further modified beyond the regulatory floor created by Public Act 21-29. These changes could include eliminating parking minimums and/or implementing on-street parking management and parking permit programs. In some other cases, towns should pursue strategies that go beyond satisfying parking demand by addressing access to other means of transportation besides cars. This assumption recognizes the need for parking, but encourages broader thinking around meeting parking needs and discourages over-parking, particularly in areas where alternative transportation modes are a feasible option.

Finally, the aspirational scenario assumes that the market value of single-family property and their corresponding physical improvements - not zoning - would largely determine what is considered an underdeveloped property.

Technical assistance and financial aid programs could be designed in ways that encourage property improvements in the form of ADUs or conversions. The land value ratio could be used as an indicator to inform where and when it makes financial sense to provide assistance and subsidies to property owners seeking to build an ADU or a conversion, or incentivizing their construction based on the annual depreciation of single-family buildings.

Alternative Scenario (Constrained)

The alternative to the aspirational vision is a scenario without zoning reform and lack of programs aimed at supporting new housing and ADUs. In this case, creation of ADUs and conversions - and the ability to meet housing demand with these housing typologies - would largely remain constrained. Such limited growth would also follow irregular patterns shaped by a patchwork of inconsistent regulations and a lack of supporting programs.

The net incremental increase in housing supplied would be approximately 16,000 additional units, less than half when compared to the projections estimated in the aspirational vision. This represents 4% over the existing housing stock or 6% over the number of single-family residences.

For this alternative scenario, we factored the same variables as the aspirational vision scenario, and incorporated current ADU zoning restrictions, as compiled by Desegregate Connecticut. In this scenario, the incremental increases in ADUs and conversions are dependent variables to the level of zoning restrictions summarized by the index. The incremental increase in housing units uses the unconstrained potential from the aspirational vision, but assumes an inverse proportion based on the level of restrictions as ranked by the ADU zoning index.

For more detailed documentation about methodologies used to develop these scenarios, please consult the technical appendices.

Analysis: Housing Potential and Housing Needs

The net increase in housing supplied under the aspirational vision is more than double when compared to the projections estimated in the constrained scenario.

Each municipality in Fairfield County is unique. Depending on local conditions, ADUs and conversions can play a significant role in fulfilling housing needs and meeting demand. While ADUs and conversions have potential to benefit all municipalities, based on their unique conditions, some will benefit more than others.

As the chart above indicates, the net increment in housing units (the difference between the aspirational and constrained scenarios) is typically greater for municipalities located along the coast and for those better served by transit corridors, particularly the Metro North New Haven Line.

These municipalities have the most to gain from ADUs and conversions, and the greatest responsibility to not only uphold Public Act 21-29, but to go beyond it with regulations, incentives and streamlined processes that make it easy to create ADUs and conversions.

On the other hand, more rural municipalities - typically with less transit accessibility and above average land improvement ratios - and despite having more availability of physical space - tend to have a marginal difference between each scenario. The municipalities of Sherman, Weston, Easton, and Redding all show a modest difference that does not surpass a net gain of more than 100 units per town. In such municipalities, the new regulatory floor created by Public Act 21-29 will only make a modest difference compared to current conditions. And even if these municipalities go beyond Public Act 21-29 to further stimulate ADUs and conversions, the net gains will not be as significant when compared to the larger and more transit oriented towns in Fairfield County.

In addition to the potential housing demand that can be met with ADUs and conversions, municipalities in Fairfield County should also consider how these housing typologies can help them meet housing needs in terms of demographics, inventory, and affordability. Regional Plan Association recently documented these conditions in detail in the recent Fairfield Housing Needs Assessment.

New housing created through ADUs and conversions could help satisfy needs in many localities.

But in most cases additional measures like equitable transit oriented development (TOD), middle density options, and multifamily buildings, should be put in place.

The chart above compares the potential net increase in housing against households that are cost burdened by town (for renters and owners, light and dark blue correspondingly). With this comparison - everything else remaining equal - we can observe the degree to which new housing created through ADUs and conversions can meet, and not meet, local needs.

However, closing these gaps will require calibration of variables incorporated into a needs assessment that evaluates demographics, household composition, and affordability levels. This type of technical assistance and coordination will demand significant resources that are typically not available at the local level, suggesting that there is a greater role for the state to play beyond Public Act 21-29.

While ADUs can and should be part of solving housing needs, they are only part of a larger set of potential tools. The existing housing needs of municipalities like Stamford, Bridgeport, and Danbury far exceed what could be met through ADUs and conversions alone. This suggests communities should continue exploring additional measures like equitable transit oriented development (TOD), middle density options, and multifamily buildings, among others.