Core ADU

Attainable housing for aging in place

  • Type House,
  • Location Anywhere
  • Area 750 s.f (variable)
  • Status Prototype
  • Date 2023

The Core ADU is an adaptable prototype Accessory Dwelling Unit designed for aging in place, affordability, and energy efficiency. The concept and its adaptability foreground the diversity of family and household profiles, and lot types that make up American urban and suburban communities. The prototype features a fixed “core” containing an accessible bathroom, laundry, kitchen, and a utility attic, surrounded by accessible and flexible living spaces (living/dining, bedroom, entry, kitchen). The core design is fixed but the dimensions of surrounding spaces can vary allowing the concept to be configured for the available spaces on different lots.

The standard plan is a 750 gross square foot, one-bedroom dwelling with optional partition to create a second bedroom. Alternate configurations such as the “square plan” and “engaged core” are as small as 460 gsf, and possibly smaller. However, the prototype can easily be adapted to larger sizes where permitted (Actual Architecture Co. designed the Core ADU for Omaha, Nebraska zoning and codes but the prototype’s adaptability allows it to be configured for any jurisdiction that allows ADUs in established and new neighborhoods).

Plans for the Core ADU are available for purchase from Actual Architecture Co. Please contact us for details. Preapproval via the City of Omaha’s Fast Track process is pending.

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The Core ADU follows 3 design guidelines

1. Better Living Design Institute’s Age-Friendly Accessory Dwelling Unit (ADU) Design Criteria.

2. U.S. Department of Energy Advanced Wall Framing Technical Fact Sheet or the APA’s Advanced Framing Construction Guide.

3. Mandatory Minimum Design Requirements of the Nebraska Department of Energy & Environment’s Dollar and Energy Saving Loan Program. The NDEE standard also allows the homeowner to qualify for the Dollar and Energy Saving Loan Program with its very low interest rate mortgage.

An age-friendly accessible kitchen.

The dwelling is designed for accessibility, energy efficiency, low embodied carbon construction, and low maintenance. Affordability is a result of extreme efficiency and smart construction practices. The core, which contains the most intensive construction demands (kitchen, bathroom, and laundry) along with the storage elements, can be built off-site as a complete module or prefabricated as “flat-packed” components to be delivered and installed on site, thus limiting construction time and disruption to the existing neighborhood.

A generous Living–Dining Room with a high ceiling that opens to a covered patio.

The core separates public and private space without wasting space in single use corridors – all spaces serve a useful purpose for small dwelling inhabitation. In the standard plan, a rectangular configuration, an open living / dining room occupies one side of the core with a single bedroom on the other. A generous galley kitchen allows passage around the core on one of the narrow sides while an entry with bench or desk affords access around the opposite side – the core floats within the “loose” spaces of the home.

Numerous Possible Configurations

The standard plan is a 750 gross square foot, one-bedroom dwelling with optional partition to create a second bedroom. Alternate configurations such as the “square plan” and “engaged core” are as small as 460 gsf, and possibly smaller. The prototype can easily be adapted to larger sizes should the 750 gsf limit be changed.

Building Components

While the Core is the most important component, the prototype also features a long, adaptable Storage Wall and an additional (optional) Closet/Bench. The primary living areas open to a private, covered outdoor patio with garden. The primary entrance approach is from the street. The building is constructed with advanced wood framing techniques which increases energy efficiency, reduces material use and construction waste, and saves cost. The Core ADU is designed as a detached dwelling but can easily be adapted as an attached second until with an indoor connection to the Primary Dwelling Unit.

Interior Finishes

The finishes of the Core, Storage Wall and Closet/Bench become features for those desiring a more modern interior environment with diverse color and materiality. In the prototype design, the Core is clad in clear-sealed plywood or wood veneer paneling while the storage wall and closet are finished with a durable, colored lacquer. All materials and finishes are rated zero-VOC and selected for sustainable characteristics. Siding is painted fiber cement, but other materials are possible. We believe the diversity of configurations, forms, and material finishes will result in a more friendly and approachable neighborhood. The standard plan features a shed roof designed to accept a solar PV array, but other roof forms are possible to either reduce height or conform to neighborhood design standards if required.

Roof Form Options

Zoning

The Core ADU prototype is adaptable to different lot sizes, zoning requirements, access types, and Primary Dwelling Unit configurations. Actual Architecture Co. identified approximately 256 unique lot types in Omaha and our goal is for the Core ADU to be adaptable to all properties including those with parking access from the street or from the alley, single and double width lots, typical or corner lots. We tested alternate site and ADU configurations for the average single-width lot (width = 28’-60’ / depth = 100’-140’), the average double width lot (width = 60’-120’ / depth = 100’-140’) and corner lots ranging from typical lot size up to large square or rectangular areas with sides ranging from 100’-200’. Any ADU is clearly going to be easier to adapt to neighborhoods with predominantly 2-story homes and ample backyard space, but the Core ADU provides maximum flexibility for even challenging situations.

The Core ADU complies with all applicable Omaha Zoning Ordinances (Omaha Code of Ordinances > Chapter 55 - Zoning > Article XV. - Supplemental Use Regulations > Sec. 55-763. - Residential Use Types > (g) Accessory Dwelling Units) and applicable building codes.

Lot Setbacks (Omaha, Nebraska)

Building Systems & Performance

The home is sealed to a tightness (as measured by a certified HERS rater) to 400 cubic feet per minute at 50 pascals (CFM50) plus 100 CFM50 per 1000 square feet of floor area, or less and includes an ERV system installed with high velocity HVAC. The floor of the standard plan is an efficient concrete slab on grade. This may be upgraded with an optional hydronic in-floor heating system to improve conform and reduce indoor dust circulation caused by standard ducted HVAC, especially in winter indoor air quality can be challenging. Appliances are all Energy Star rated.

With certain upgrades the Core ADU can achieve net-zero energy use and built to Passivhaus standards.

Project Awards

3rd Place, An ADU for U design competition

Publications

Omaha World Herald, “Omaha could open entire city for small dwellings; winning architect firms have plans ready” but Marjie Ducey, November 21, 2023

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