Inhabit: A Case Study Prefabricated Modular Apartment Living
Moshe Safdie and Associates, Habitat ‘67
Beyond the Prototype Prefabricated buildings are not a new concept. Kit houses were manufactured and marketed by Sears, Roebuck, & Co. in the early 1900’s. High-end single family prefabricated homes have been available for years. Prefabrication construction techniques have also been employed in multifamily applications, but the vast majority of these projects are in a suburban or pastoral context.
Matti Suuronen, Single Family Prefab Home
Our design collective wanted to explore the implications of using prefab construction to change the economic, environmental, and social factors of urban multifamily real estate.
Urban Testing To determine if prefab was a viable urban development model, the design collective performed a schematic cost analysis of site built construction vs. wood frame factory built construction vs. adaptive reuse of steel cargo containers. Both the cost analysis results and the close proximity of a factory prompted the team to explore wood frame factory construction as the best option.
The design collective designed and built two modular prototypes to explore assembly and transportation techniques, to develop a design language, and to gain experience with local and state permitting challenges. The prototypes are prominently displayed on a roof plaza in downtown Seattle and tours of the units are offered to solicit public response to this new model of living.
Prototype Modules | Seattle, Washington
“Done right, modular construction is an inherently more sustainable way of building.” Robert Leykam, AIA Architect
Construction A large part of the appeal of this construction process to the urban workforce market is the incorporation of many sustainable design ideals:
Carbon Cost of Construction: Though the process uses large trucks, escorts and cranes to deliver the units, the delivery and setting process takes just one day.
Reduction of waste: Most construction sites can waste up to 30% of their materials through weather damage & off cuts. Construction in a factory offers manufacturers the opportunity to buy items in exact lengths, reducing waste from the onset. The automated machinery anticipates the ‘waste’ of one module and can catalog and store those materials for use in the next module.
The reduced construction time means less neighborhood disruption at the site. Also, most factories also employ local labor which greatly reduces the many miles driven to the construction site by multiple trades.
Strength: Because the units will be shipped on trucks, they do need to be structurally stronger, but they use just 10% more materials for that added strength. With a savings of up to 30% on waste reduction, the modules are still 20% more efficient than site built construction. Construction in a controlled environment: Factory built structures can be built year round without weather delays. Once units arrive at the site, the application of exterior cladding can take just a few days so the building isn’t sitting for an extended time vulnerable to rain or weather.
Interior Innovation The clean architectural language, including floor to ceiling glass and smooth monochromatic surfaces, was conceived to create a breathable and customizable space. The generous glazing provides ample natural light and takes advantage of cross ventilation as a natural cooling strategy. The minimally detailed, white surfaces provide a sophisticated backdrop for the tenants to express their own personal style.
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Prototype Plan Diagram: Upper Unit
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Prototype Plan Diagram: Lower Unit
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Principles of Modular Construction in an Urban Fabric During the transition from the prototype to the site application, the design collective realized that we needed to develop a strategic tool kit. If urban prefabricated modular apartments were going to be viable and appealing, we needed a set of strategies that would allow the architecture to respond to the particular context of each site: size, orientation, and diversity of unit types. The dimensional restrictions, replicablility, and ‘boxiness’ of prefabricated modular architecture is both a benefit and a drawback. These are the qualities that make the project economically viable, but they are also the qualities that make an appropriate and specific architectural site response challenging.
1. Congruent Simple design parameter based on standard module width Limited possibilities for unit type diversity and module arrangements More, shorter modules is inherently inefficient Efficiency can be increased in the congruent (twin) model by combining two dwelling units ‘end-to-end’ in one module Best suited for single family/low density models or sites with limited craning maneuverability
Step 1: Individual Module
Step 3: Module Stack
Module
Step 2: Module Array
Step 4: Site-built Circulation
Dwelling Unit
2. Barbell Allows for unit type variety based on unit width and depth Maximizes possible module length Integrated circulation is inherently economical Model has been used primarily for economy structures (Holiday Inn Express), but has potential for limited building mass modulation
Step 1: Individual Module
Step 2: Module Array
Module
Step 3: Module Stack
Dwelling Unit
3. Crosscut Allows for unit type variety based on unit width Maximizes possible module length Organization into wet and dry modules affect factory work flow Site-built circulation is inherently inefficient
Step 1: Individual Module
Step 3: Module Stack
Module
Step 2: Module Array
Step 4: Site-built Circulation
Dwelling Unit
Site The urban site selected by the development team has a commercial component zoning requirement. The zoning restrictions and sloped topography of the site lent itself to the design of a podium building. The first floor contains live/work lofts, an entry lobby, bicycle storage, and a parking garage of concrete and steel construction. This concrete podium is the base for five floors of stacked wood frame modules that serve as the residential dwelling units.
Site Built Construction
2nd Floor Modules
3rd Floor Modules
4th Floor Modules
5th Floor Modules
6th Floor Modules
Developed for Unico Properties in partnership with HyBrid Architecture
SEATTLE
Pier 56 1201 Alaskan Way, #200 Seattle, WA 98101
SAN FRANCISCO
660 Market Street, #300 San Francisco, CA 94104
mithun.com