Solar Grid: net-zero multifamily design narrative

SOLAR GRID

UNIVERSITY OF MISSOURI, COLUMBIA

MULTIFAMILY EXHIBITION TEAM

EXISTING MARKET

ENGINEERING

EXISTING MARKET

Columbia, Missouri is a medium-sized town in the middle of the state, home to the university of Missouri. The downtown area is a growing community with a vibrant food, art and music scene with opportunities for employment. Douglass Park, just north of downtown Columbia, is a historic residential community with a diverse, yet aging, architectural language. The community has multiple schools within walking distance and a community park with basketball courts, a pool, and skate park. Douglass Park also has the highest density of those in need of low-income housing in Columbia.

A 2013 plan of action from the Columbia Housing Authority (CHA) reported a need for an additional 2,500 low-income housing units, with the scope of their plan centered around the Douglass Park area. Few new rental options exist for those looking for affordable housing, and none under the Low Income Housing Tax Credit (LIHTC) program exist in either the downtown or Douglass Park communities. This leaves people in need of affordable housing sitting on a wait-list for section 8 housing voucher applications at the mercy of fluctuating rents. Few options are also provided for single person households, with a majority of public housing being dedicated either to larger households or seniors.

However, a majority of project based voucher (PBV) applicants are single person households. Our team targets those single non-senior households who are under-represented in the public housing realm. That same plan identified several sites which could host new developments for affordable housing. However, these sites are either distant from the existing community, places of employment, or re-purpose beneficial green space within the community (one of the sites is Douglass Park itself).

According to the 2020 census the average household median income in Columbia is $57,463 and $32,784 per capita. As of March 2023, the average rent in Columbia for a one bedroom apartment is $800. This would consume at least 59% of a typical low-income individual’s (50% AMI) earnings through the year. Options in the $500-700 range only make up 10% of the town’s rent options. Affordable housing is still a luxury. Solar Grid will utilize the LIHTC to help fund the development, which ensures rents are fixed at an affordable rate for the first 15-20 years of occupancy. Of the options that do exist, many are outdated, run-down, and are energy inefficient, increasing utility demands on the tenant. Current tenants of CHA properties requested that future developments implement energy efficient design, better ventilation and HVAC, more storage, and outdoor spaces. Solar Grid’s thermal envelope and mechanical systems will contribute to a more comfortable option, with increased affordability through lower utility costs. The implementation of outdoor porch spaces and a shared semiprivate courtyard will provide occupants access to nature and enjoyable views. Co-op retail spaces, a career center, and an extension of the Columbia Housing Authority office will contribute towards aiding the upward mobility of the younger single person households that Solar Grid is targeting. Tenants have the opportunity to have a role in several businesses that contribute equally amongst its members.

fig. 1.2

CHA Development Scope

SITE AND SETTING

The 1.65 acre site is located at 701 East Ash St. in Columbia, MO. The site was selected for its adjacency to downtown Columbia and Douglass Park. The site is also shared by the Columbia Armory Recreation Center. The Armory contains a gym, a bike repair co-op, and community spaces. It also serves as a storm shelter in times of emergency for the nearby neighborhood. The location of this building was a large part of the site selection. Solar Grid will partner with the city of Columbia to help maintain the armory, and provide emergency water and energy in times of emergency or outages. In return, the Armory will lend its recreation services to the tenants of Solar Grid, reducing the sq. footage required for amenity spaces. The south of the site is bounded by the tall Boone County Courthouse. The North is occupied by single story residences, also owned by the Columbia Housing Authority. To the east is the North Village Arts district, a growing live-work community with a contemporary industrial architectural language.

The existing site contains only the Armory and a city parking lot. The parking lot covers almost the entire site, though is rarely at capacity. Three recycling collection bins are located south of the Armory as well. The site slopes down 12 feet from the south to the north, creating problems for flooding on the north end of the site. However, there is ample space to provide landscaping strategies to reduce the impact of storm-water runoff. Subterranean parking can cut into the slope of the site to create a level surface for the building itself. The site also presents shading problems; the courthouse has potential to

over-shade Solar Grid in the Winter, while the low-rise residences to the north are at equal risk from Solar Grid. The form steps down as it moves north to allow for a direct path of sunlight to reach these residences, while situated far away enough from the courtyard that its shadows will also be unfelt. The building uses a U-shape to maximize the amount of units that can exist on the site, while also ensuring all units receive at least four hours of sun a day while providing a shaded exterior spaces for tenants to enjoy nature during the hot summer days. The courtyard will reduce the urban heat island effect.

ColumbiaAuthorityHousing

Columbia College

Jefferson Middle School

Walgreens Pharmacy

Stephen’s College

Bus Farmer’sStation/Market

SITE

fig. 1.2

Neighborhood plan

CLIMATE

The site is located in a 4A Mixed-Humid climate, with cool to cold winters and long, hot and humid summers. The hot season lasts from late-May to early-September when temperatures average at least 79°F. The cold season lasts from lateNovember to late-February when temperatures average at most 49°F. The area has about 2700 Heating Degree Days and 2000 Cooling Degree Days each year. In the future these numbers may change due to global climate change. Researchers at the University of Missouri-Columbia have suggested that this climate may face less Heating Degree Days and more Cooling Degree Days down the line. Since Columbia is centrally located in the interior United States, the area often experiences drastic changes in temperature. The climate is affected by cool air coming from the Arctic and warm air coming from the Gulf of Mexico. The average max temperature in Columbia is 75.1°F while the average low is 50.9°F. July is the hottest month with an average temperature of 80.8°F while January is the coldest month with an average temperature of 43.8°F. The wet season lasts from mid-March to late October, with 27% chance of days being wet ones. The wettest month is may with an average of 4.4” of rain. The snowy period lasts from mid-November to mid-March, with an average high of 3.6” of snow in January. Humidity is high from May to September when conditions are uncomfortable

fig.

YEARLY TEMPERATURES (F°)

SEASONAL WIND

CLIMATE

Climate informed the design of Solar Grid through the implementation of passive strategies to improve the overall comfort and energy consumption of occupants. The site is oriented north-south, and so it was difficult to maximize solar gains for renewable energy collection and passive heating. The majority of units are placed on the south facade, though the U-shape of the building ensures that every unit receives at least four hours of direct sunlight a day. Pushbacks in the facade create shading opportunities during the cooling season. Consideration of precipitation data informed the rainwater collection design on the roof and courtyard, and the storm-water run-off mitigation strategies to the north. Graphite polystyrene (GPS) rigid insulation sheathes the building, creating a sufficient vapor barrier for Missouri’s high-moisture climate. Exposed single loaded circulation allows for passive ventilation from the heated side of the building to the courtyard. To account for potential winds entering the courtyard, existing coniferous trees will be relocated from the east boundary of the Armory (where they could not have grown with the new building) and planted along the exposed north boundary of the courtyard.

Site sun path fig. 1.5

CODES AND STANDARDS

Our design takes strives to meet multiple standards of efficient and equitable design, taking inspiration from the WELL building standard, LEED rating system, and the Columbia Climate Action and Adaption Plan (CAAP). These standards influenced our material selection to eliminate toxic VOCs. All apartments have equitable access to daylighting, views and nature. Our design takes several liberties with municipal code for the better function and visual characteristics of the neighborhood. We believe through an appeal process, the environmentally and historically minded city of Columbia would approve our decisions. Our building is set back further than the required distance to accommodate the visual characteristics of a historic location, as well as to increase walkability. Additionally, our retail ceiling-to-floor height is 10’-6”, 4’-6” below the minimum. This was to increase the potential for ground floor units, in which 15’-0” ceiling heights are significant and inefficient. The main entrance has an uninterrupted facade height of 21’-0” to compromise with the code. Additionally, we believe to best comply with Columbia’s climate goals as outlined in its Climate Action and Adaptation Plan (CAAP) of reducing greenhouse gas emissions by 100% in 2050, the use of 15’-0” ceilings is no longer efficient in its use of energy. Research has shown that despite energy use per capita is decreasing in municipal buildings, total energy use is stagnant. This will continue to be the case unless we design for better building energy

efficiency. We believe that because our building adds to the community by remaining respectful of its architectural language, and by pursuing the energy efficient strategies that the city itself advocates for, the city will approve our adjustment of its municipal regulations. All other components of height, parking, facade treatment, and other regulatory requirements of Solar Grid comply with municipal standards. Our building was designed in consideration of the accepted 2018 IBC, which is the adopted building code of Columbia. Our use of mass timber under Type III-B construction breaches several height and fire-related provisions in this code. However, we have numerous precedent of laboratory and field testing to demonstrate that an appeal process would be acceptable. Under the 2022 IBC, however, we would be able to construct Solar Grid under the TYPE IV-A construction without any changes. Columbia has a history of adopting the latest iteration of the code soon after it is accepted, so this route is acceptable.

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DESIGN GOALS

COMMUNITY INTEGRATION

Improve the neighboring community through improved walkability, economic opportunity, flooding mitigation, and disaster assistance. Connect the co-op retail spaces with the adjacent Columbia Armory and District Farmer’s Market. Reduce hardscape and implement low-impact development (LID) strategies to alleviate problems of storm-water run-off. Provide emergency water and power to the Columbia Armory, a neighborhood disaster shelter, in times of grid outages.

IMPROVED QUALITY OF LIFE

Use biophilic design strategies to improve the mental and physical health and well-being of occupants. Provide opportunities for employment, both in on-site retail and through a dedicated career center. Design spaces that transition smoothly from public, to semi-private, to private to provide a distinction between community and individuality. Utilize non-toxic materials and natural ventilation strategies to improve the indoor air quality for occupants.

SUSTAINABLE MATERIAL SELECTION

Select materials based on their embodied and operational carbon cost, without sacrificing one for the other, to reach CAAP emissions and global temperature goal. Use prefabricated mass timber assemblies to reduce carbon footprint and construction time. Pursue regional materials that tie the building to the vernacular, and reduce total carbon emissions from transporting materials.

AFFORDABILITY

Design an air-tight highly insulated thermal envelope to increase energy efficiency and reduce utility costs. Make energy and water consumption renewable through the use of photovoltaics and rainwater collection to reduce reliance on the city grid, and lower utility costs. Pursue local and national funding and incentive options for meeting up-front and operational costs, such as HOME funds, Community Block Development Grant, and the LIHTC. Provide a fixed affordable rate for tenants for the first 15-20 years of operation.

ARCHITECTURE

DESIGN PROCESS

The design process began with programming for equitable and energy efficient design. Aidan Kurtz and Hanbin Kim then worked with a clear design goal exploring modularity and mass timber in conjunction with the integration and rehabilitation of the Columbia Armory and Recreation Center. Iterations of form and unit-based design and material selection led us to the final submission for the 2023 Solar Decathlon competition. Specific attention was given to finding solutions for safety and comfort in the unit design, complimentary to the community in form, and low embodied carbon materiality in assemblies. Iterations began with passive strategies in mind, and evolved to optimization of the building through energy modeling as the competition drew nearer.

ARCHITECTURAL DESIGN

Solar Grid is composed of one and two-bedroom living modules interchangeably stacked six stories atop a subterranean parking lot and storm shelter. There are 48 underground parking spaces, with overflow street parking to the north of the site. Roughly 13,000 sq. ft. of co-op, retail, and amenity space occupy parts of the first and second floor. The double high lobby, leasing suite, and coop and rentable community spaces occupy the first floor. They open up to a large courtyard with a container garden at the northwest corner. The lobby mezzanine, a communal kitchen and laundry room, career suite, and community space are on the second floor. In conjunction with the city, a bridge will connect the Armory to the second floor, allowing

residents direct access to the recreation center for additional amenities. 54 total units with 69 beds are comprised of 39 one-bedroom and 15 two-bedroom units. Every story has residential units, and every unit is ADA accessible. The form steps down as the slope descends to the north, being conscious of the scale of the courthouse to the south, and the single story residences to the north. Our building plan is U-shaped to maximize the opportunity for passive design in a site that is oriented north-south. All units will receive direct sunlight in their space for at least four hours a day, reducing the need for electric lighting and heating demands in the winter. The shape also creates a natural space for a courtyard, and circulation that encourages connectivity and safety. These corridors are

LEVEL SIX

LEVEL FIVE

LEVEL FOUR

LEVEL THREE

LEVEL TWO

LEVEL ONE

six1-BR, two 2-BR

nine1-BR, two 2-BR

seven 1-BR, six 2-BR

ten 1-BR, three 2-BR

four 1-BR, three 2-BR

CHA branch office

career suite work suite

lobby community kitchen laundry

three 1-BR, one 2-BR

courtyard/community garden

co-op space

leasing suite

check-in/security

lobby

Commercial Living Unconditioned

fig. 1.2

ARCHITECTURE

left open to reduce energy costs for conditioning, and to allow natural ventilation through the units. Units can be accessed by a central elevator in the south, or by staircases that cap the ends of the “U.” Intermittent void cuts through the circulation respond to the staggered form of the facade, and create opportunities for vertical communication and patterns of light and shadow. The open corridors provide passive accountability and security, as residents can look out for each other from each side of the building. All commercial circulation is interior, while residential is exterior. To access the latter, one must pass through a secure entry for the privacy of residents. Roofs are left flat to complement the form, and account for the cantilevered solar array and rain collection systems. Commercial spaces on the first floor are set back 6’-0” from the main facade, providing passive shading and improved walkability. Setbacks in the individual units create a staggered checkerboard treatment along the facade, creating ledges and overhangs for planters and passive shading, respectively. Solar panels attached directly to the south facade give extra shading to the side of the building most directly affected by the sun. Our materials were selected for their vernacular characteristics and energy efficiency.

Brick cladding and the exposed mass-timber columns relate the first story to the surrounding area, while educating the public about alternative structural materials. Charcoal metal panels clad the rest of the building, tying it to the nearby contemporary industrial character of the North Village Arts District. Perforated panels surround exterior staircases to mitigate wind effects and provide a sense of security and visual consistency. Occupied alleys are a growing part of the downtown scene. The alleyway between the Armory and Solar Grid mimics the similar downtown pathways of the District. The stacking of the living modules and stepping down of the building form allows continuous refrigerant and duct lines from the roof to the individual units. This reduces material costs and improves efficiency by running shorter lines. Plumbing lines can be run through intertenancy walls to service two units at a time. The courtyard provides a semiprivate space that protrudes north of the west section of the form. This extension has a constant allowance of sunlight, creating ideal conditions for a container garden in which residents can grow and sell their own goods. Permeable pavers and low slopes in the sodding help slow and retain rainwater for reuse in greywater systems following storms.

ARCHITECTURE

LEVEL 1

LEVEL 2

fig. 1.6

fig. 1.4

fig. 1.5

ARCHITECTURE

INTERIOR DESIGN

Interiors are designed to improve the mental and physical well-being of occupants, while offering adaptability to tenants to make a space their own. Exposed wooden elements give the space a sense of calm, and improves their physical and mental well-being. Single bedroom units share the same floor plan for ease of construction. Casement and window trim match the exposed wood of the CLT to create a warm inviting environment. Natural lighting on the street-side facades open up the space and reduce energy consumption when using electrical lighting. An exposed concrete floor contrasts with the natural wooden elements, while cutting down on additional material costs and simplifying cleaning and maintenance. It also functions as a thermal mass in conjunction with the masstimber slab it rests on. Plenty of shelving and storage will allow users to display and organize their personal items and better identify with the unit. Lobby design includes more wooden elements to identify with the mass-timber structure and create a comfortable space. A green wall helps remove indoor pollutants and improve the mental well-being of users. Plenty of seating on the first floor and mezzanine allow residents to relax and interact with each other in a large open space. Decorative pendant fixtures give the lobby a sense of scale and interest, while large glazed facades on the southeast corner allow in plenty of natural lighting and passive heating.

Corian glacier white

Sherwin-Williams sunbleached

Structurlam southern pine

Interior single bedroom fig. 1.7 fig. 1.8

SINGLE BED APARTMENT

TWO

BEDROOM APARTMENT

fig. 2.1

fig. 2.2

ENGINEERING STRUCTURE

The selection of our structural system was and integral part of the early design process. We took the following into consideration when we were researching different options:

• The production of concrete and steel, typical components of a building’s structure, account for 21% of global CO2 emissions.

• Embodied carbon accounts for a greater volume of emitted carbon for the first 15 years after building construction than operational emissions.

We thus sought out a structural system that has a low embodied carbon in order to meet the goals of the Paris Climate Goals and CAAP goals of reducing emissions by 100% in 2050. We selected Mass Timber to replace the traditional steel and concrete structures of contemporary buildings. Mass timber sequesters carbon over its life-cycle, pulling CO2 from the atmosphere as the forests it sources from grow. Additionally, mass timber is much lighter than concrete with no loss of strength, reuiring less cost in transport and construction. Mass timber is also market-ready in our region, unlike innovative plant-based concrete systems that are emerging. We selected the company Structurlam, a crosslaminated timber (CLT) and glulam manufacturer as our provider. They are an FSC certified mass timber company who sustainably sources their wood from the Southern Pine forests of Arkansas. They precut our building components into a kit of parts before shipment so assembly on site is quick. By the 2018 IBC, all of their components are firerated without the additional need of cladding exposed elements. Using their model, we designed a post-beampanel structure as our skeleton on a 14’x15’ grid. To meet acoustic and vibration requirements, we added a thin poor of 2” low-carbon concrete on top of a cork acoustic mat on the CLT slabs. Additional soffits in the kitchen and bathrooms will help further insulate against acoustics. Foundation walls and floors will rely on the same low-carbon concrete.

GLULAM GRID ON LOW-CARBON CONCRETE FOUNDATION

Fire-rated glulam columns meet structural demands at less weight than steel or concrete. Modularity allows for ease of construction.

PREFABRICATED CLT SLAB WITH 2” CONCRETE FINISH

Acoustic-rated CLT pre-fab slab assembly allows for easy customization. Exposed ceilings and beams improve occupant comfort.

AIR-TIGHT HIGHLY INSULATED BUILDING ENVELOPE

R-40 walls wrap post-beam-panel structural grid, eliminating potential for thermal bridging. Glulam beams left exposed at ground level.

ENGINEERING PLUMBING

During our initial design process, we evaluated a variety of plumbing solutions to reduce flow rate, length of piping, and construction time. Defining the locations of necessary plumbing systems was critical during this process. The modularity of the building allowed common plumbing walls to reduce piping length and water heater distance. We decided to use a 40 gal Rheem hybrid water heater to supply two units at a time. The model has a 4.07 UEF score, significantly reducing energy costs compared to a typical water heater.

It has an ambient operating temperature range of 37145 °F, and has operational energy saving modes to reduce unnecessary usage. The toilets in each unit are the American Standard H2Option Dual Flush 2-piece WaterSense Toilet. The toilet uses 0.92 GPF (gallons-perflush) for liquids, and 1.28 GPF for solids. The showerhead used in the units is from Earth Luxe, with a flow rate of 1.25 gallons per minute. The sink faucets are from Delta, and have a max flow rate of 1.20 gallons per minute.

KITCHEN low flow fixtures

HVAC

Selection of our HVAC system was based on the following:

• Maximizing human comfort

• Easy usability for tenants

• Maximizing cost:efficiency

• Easy installation and maintenance

• Quiet system performance

Based on our climate and our financial goals, we decided an air source heat pump (ASHP) would be the best fit for Solar Grid. The Trane Mitsubishi hybrid VRF system that we have selected can simultaneously heat and cool up to 35 different zones at high efficiencies. Unlike previous VRF systems, the system we have selected can continue heating during defrosting, so occupants can remain comfortable. The stepping down of the roof form allows the vertical discharge from the condenser to not be impeded by the solar array overhead. VRF lines run vertically down a shared core of units, heating and cooling zones independently. The use of

rheem hybrid wh, ducted to outside

BATHROOM low flow fixtures

FRIDGE built-in energy-star rated

PLUMBING WALL common intertenancy wall

WATER HEATER

fig. 1.3

PLUMBING SYSTEM

fig. 1.4

HVRF System

ENGINEERING

a VRF conduit instead of ductwork reduces energy losses and material cost for excess MEP space. The hybrid branch controller reduces the amount of refrigerant needed by 20%, as the heating and cooling distribution switches to water lines. Heat recovery within the branch controller allows for consistent heating and cooling without significant energy loss. Pairing the system with a DOAS system with an ERV will modulate humidity and improve indoor air quality at high

efficiency. The condenser and DOAS systems will be placed on the roof directly overtop of the units it will heat an cool. Refrigerant/water lines and ductwork will be run vertically through courtyard facing MEP walls to reduce energy loss from solar heating. The conditioned air will be dispensed through ceiling soffits, with vents in the kitchen and bathroom. The indoor HVRF system operates at only 4 db, a decrease from the typical maximum of 55 db of other VRF systems.

HVRF Routing

MARKET ANALYSIS

EXISTING CHA PROPERTIES

The Columbia Housing Authority owns and operates 719 low-income housing units. Though some are relatively new and there are in-progress projects. Many of their properties are old and inefficient. A large majority of their properties were built prior to 1975, with expensive refurbishment projects occupying a large portion of their budget. Current properties currently are:

• outdated

• disconnected from the community

• far away from public transport

• energy inefficient

Solar Grid will provide a community integrated housing development, that has access to local bus lines, chances for upward-mobility, healthy contemporary interiors that can be personalized, energy efficient units to save on utility cost, and access to nature. Use of pre-fabricated mass-timber components will help reduce construction time and cost, providing units to the community at a faster rate. Renewable energy from a PV system, rainwater collection and greywater recycling, and an energy efficient envelope will help reduce costs.

FINANCING

Program

Low-Income Housing Tax Credit (LIHTC)

Community Block Development Grant (CBDG)

HOME funds allocation

Description

A 4% or 9% tax credit that deducts 9% of construction cost from taxes owed for 10 years, provided that all units within the construction cost are below the maximum rent.

A grant dedicated towards improving the community. In the context of our project, our rehabilitation and cooperation with the Columbia Armory Recreation Center, improvement of sidewalks, and stormwater runoff mitigation would qualify us for this grant.

Formula grant provided to states to fund the building, buying, and rehabilitation of low-income and affordable housing. Our project estimates that it could receive $4.5 million in funding from HOME funds based on recent Columbia developments and total HOME funds allocated to the state.

Impact

Long term savings

Up-front grant

Solar energy federal tax credit

Local and federal limited sustainable building tax credits

30% of panel costs, installation costs, and storage costs are all reduced from taxes until at least the year 2035.

Tax credits that cover things like the usage of heat pumps, efficient insulation, vehicle chargers etc. Small scope for our project, but savings nonetheless.

Up-front grant

Long term savings

Long term savings

fig. 1.1

fig. 1.2

fig. 1.3

MARKET ANALYSIS

BUILDING COST

Using RSMeans, we calculated that our new construction including excavation would gross $21.3million, at $218 per sq. ft and $308,700 per bed. However, factoring in the conservative HOME funds estimation that would cover the initial cost, this drops to $14.9 million gross, at $172 per sq. ft. and $243,478 per bed. Using the maximum rent allowed by the LIHTC calculation of $620, our building would have a complete return on investment within 30 years. With a lower rent of $507, the

building would pay itself back in 40 years. However, this discounts rentable community and retail space, which would generate a higher yearly rental income for the building. Using the average retail rental price per sq. ft. in Columbia, MO, and maintaining that at least two retail spaces would be reserved for the co-op, an additional $31,000 in annual revenue would be added. This would allow us to reduce rent for our residents to reach a broader demographic.

DURABILITY AND RESILIENCE

DISASTER AND EMERGENCY SUPPORT

Columbia, Missouri is at risk of seasonal flooding, tornadoes, earthquakes, and other severe weather. This is something we had to think about while conceptualizing our design because we faced the challenge of making the project affordable and efficient, but also resilient to these events. A tenant storm shelter will provide a collective solution to risk of disaster, while also providing space for storage. The space is located underground at the parking garage level and is designed to withstand the most severe disasters that are possible within Missouri. Missouri was home to one of the largest earthquakes in the United States (New Madrid, 1812) and one of the worst tornadoes in the U.S. (Joplin F-5, 2011), making natural disasters an important factor when designing. Placing the shelter completely underground in the southwest corner of our site, with thick concrete walls will help ensure the safety of tenants. The shelter is expected to survive a 7-magnitude earthquake and at least an F-3 tornado. Additionally, Solar Grid will help the broader contextual community in times of disaster. Though it will provide a storm shelter for its tenants only, Solar Grid will provide water and energy to the adjacent community storm shelter, the Columbia Armory and Recreation Center. The Armory was originally designed as a nuclear bomb shelter, and supports those in the vicinity who are at risk of disaster. Stored energy from the PV array and recycled storm water will help maintain both Solar Grid and the Armory in grid outage scenarios.

STORM-WATER HANDLING

To reduce reliance on the municipal grid reduce waste, water will be recycled for reuse in greywater systems. It can be recycled for use of toilet flushing, irrigation, and the fire fighting. Recycled gray water will be sourced from both fixtures (washbasins, showers, laundry etc.) as well as rainwater collection systems on the roof and courtyard. The large low-slope roof will have several drainage pipes that divert collected rain through filtration to two 15,000 gallon collection tanks. This would supply our building with nearly two weeks of recycled rainwater and greywater when full based on a 40 gal/day use of greywater per tenant. Similarly, low-slope landscaping in the courtyard will collect rainwater and deliver it to the same tank, while also creating visually pleasing interspersed retention ponds for tenants’ enjoyment. Missouri broke records for flash flooding this year, and hard landscaping only makes the problem worse. The north end of our site is a likely spot for flash flooding, with risk of damaging the single story residences adjacent to our plot. We will utilize low impact design strategies on the edges and north side of our site to mitigate storm-water runoff and the contamination of water and soil from hardscapes. Inclusion of rock and bioswales, xeriscaping, and permeable surfaces will slow and filter abundant rainwater. This will help reduce potential damages to the residential community to the north, and improve the health of the local flora from unpolluted water.

FILTRATION TANK & PUMP

OVERFLOW 30,000 gal distributed to ground

remove sediment

BIOSWALES slow & filter rainwater

INTEGRATED SYSTEMS

PASSIVE DESIGN

Exposed circulation gives tenants a place to relax outside in the shade, and enjoy an elevated view of north Columbia, while also creating a passive ventilation system. With strategically placed windows, air can naturally flow from one side of an apartment to the other. Operable windows placed closer to the ceiling on the sun-facing facades, and closer to the ground on the shaded courtyard facing facades pushes warm air though the space as it gets cooled. To prevent direct sunlight from entering a space, portions of the facade are set back, creating an overhang for rooms that ought to be cooler. These overhangs are shallow

enough that the lower winter sun will still be able to passively heat these rooms. The ledges created by these setbacks can be used as planters for local, low-maintenance seedums. Research has shown that views of nature reduce anxiety in occupants, and can lower blood pressure. These plants are low-no maintenance, and help cool apartments below them in the cooling season, while also contributing to the visual character of the exterior. PV panels will also be integrated into the southern facade, simultaneously powering the building and providing shade to the most heated side of the building.

Require

BUILDING STRUCTURE AND ENVELOPE

In climate 4A Mixed-Humid, the envelope must combat cool to cold winters and long hot humid summers. Exterior walls are constructed out of a 2x8 staggered stud with dense pack cellulose insulation. A graphite polystyrene insulation (GPS) vapor retardant layer keeps water and moisture out of a building, while allowing indoor moisture to pass through to the exterior, unlike most vapor retardants that are wrongfully paired with cellulose insulation. This assembly will help regulate indoor air temperature and humidity levels, without

allowing moisture buildup in between finishes. The masstimber structure allows for quick construction, and provides a rigid frame that can endure wind, fire, and earthquakes. A large portion of the CLT panels are left exposed in living areas. This allows for more natural daylighting to enter a space and make the room feel more open, while also contributing to the aesthetic appeal of interiors. Research has also shown that the exposure of wood and plant-life in a building improves occupant’s physical and mental well-being.

SUMMER SUN WINTER SUN

NATIVE MISSOURI SEEDUMS

little-no maintenance, sun, water. Reduce cooling demand during summer, biophilic design improves occupant wellness.

SOLAR SHADING

fig. 1.1

EMBODIED ENVIRONMENTAL IMPACT

Our material selections were heavily influenced by the CAAP and Paris Climate goals. Global emissions are behind the pace required to meet the 100% emissions reduction by 2050, and to avoid the 1.5°C temperature change from pre-industrialization. Therefore, we can no longer only prioritize a reduction in operational carbon costs at the expense of embodied carbon costs, which make up most of the emissions of a building’s life cycle for about the first 20 years. We selected materials with little to no cost in quality that emit far less carbon than traditional construction materials, or even recent energy efficient “green” materials.

STRUCTURE

A recent study has shown that using mass-timber in a mid-rise building can reduce life-cycle carbon emissions by 80-99% more than a traditional steel and concrete building, depending on end of life treatment. Our selection of a mass-timber structural system with glulam beams and columns and CLT panels will significantly reduce the total carbon emitted into the atmosphere, both in the sequestration that timber ensures in its own lifecycle, and in the reduced transport cost and construction time that comes with prefabrication. We were lucky enough that the innovative mass-timber company, Structurlam recently opened a manufacturing plant in Conway, Arkansas. Thus, our structural frame is locally sourced, tying the building into the region and significantly reducing transportation requirements. The foundation and 2” floor toppings will use EcoPact concrete which can reduce embodied emissions by up to 100%.

INTERIORS

To reduce total material cost, the 2” concrete pour on CLT can act as a finish material as well as a structural material. Offcuts from the prefrabrication process of the CLT panels can be re-used in built-in furniture within the units, reducing waste and potential release of carbon back into the atmosphere upon disposal.

WALL ASSEMBLY

Our use of dense pack cellulose has a significantly lower emitted carbon than other insulative materials. Though its R/inch value is slightly lower, we believe the added wall thickness to meet a total R-40 wall configuration is worth the cost. We also found a rigid sheathing board, Halo GPS, which reduces emissions 61% more than EPS and XPS insulation. Our exterior cladding selection is a metal panel that contains recycled metal, and can be completely recycled at the end of its lifecycle. Interior finishes use USG’s EcoSmart gypsum panel, which uses 20% less carbon than traditional boards, and weigh 22% less, making transportation demands less impactful.

193 kgCO2/m2

237 kgCO2/m2

-276 kgCO2/m2

fig. 1.1

Embodied carbon of Mass Timber vs. Concrete

Mass Timber Concrete

Sequestered carbon

fig. 1.2

OCCUPANT EXPERIENCE

Solar Grid was designed to provide a space of mental and physical well-being, and opportunities for upward mobility of residents. The ground level includes a lounge, a large courtyard with a container garden, a community space, and co-op retail spaces in which tenants can control and profit from their business. The garden can also help support the growing North Village Arts District farmers market just a block away. Small setbacks found intermittently create pockets of privacy and respite. The second story features a laundry room and communal kitchen with a gathering room to complement the both of them. There is also a career suite where tenants can find jobs and work remotely. In the wake of COVID-19, private and outdoor working spaces are also provided. The building is designed to provide residents a transition from public, to semiprivate, to private. They move from the street to the exterior circulation in which they can communicate with other residences of the building and finally to their own residence. Void cuts in the circulation give residents the ability to communicate with one another on the upper levels of the building, creating a sense of community. The U-shape promotes accountability, allowing tenants to feel secure outside since other residents can see if something is amiss. Setbacks in the resident walls give residents a sense of privacy in their dwelling, as well as creating more outdoor space to relax. On the interior, natural exposed wood can relax users, and provide a brighter warmer feeling to the room. Plenty of shelving allows users to display their collections and truly make the space their own, with additional closed storage in the unit to take care of the rest. The concrete flooring gives tenants the opportunity to decorate the floor, as well.

THERMOSTAT

Mitsubishi provides an intuitive zoned system control that can control units from a central system (for commercial) or from a personal app (for residential). For centrally controlled commercial spaces, the smart ME controller can manage 16 thermal zones, while saving energy with an occupancy sensor. If no movement is detected in the room, the system will automatically switch to energy saving mode. For residential, the Kumo Cloud app allows users to specify their own heating and cooling needs, giving them the opportunity to designate different temperatures per room in their apartment. The app automatically switches from cooling mode to heating mode and back to cooling mode after surveying each zone. Users also have the ability to set timers on a 7-day cycle to automatically turn the indoor units on and off, saving energy during unoccupied hours. Both controls also allow for the pairing of third party systems including HVAC and water heating, while also giving status updates about filter conditions and system errors. It is important that occupants are sufficiently educated about this system to properly save energy, while living comfortably.

LIGHTING & FIXTURES

Orientation of rooms to allow in plenty of sunlight means users can save energy by relying on natural daylighting. For spots that do require electric lighting, we have selected the CSL ECO 3” recessed LED downlight. The fixture has a small profile of 2.5”, reducing occupied soffit space, while providing 50,000 hours of lighting at a high efficacy. It has dimming from 0.1%-100% at color temperatures of 2700K, 3000K, 3500K, 4000K and warm dim, allowing users to set the desired light level and mood in their apartment. The driver is accessible from below the ceiling meaning maintenance is cheap and simple.

fig. 1.1

OCCUPANT EXPERIENCE

We have also selected the Aeratron FQ series 42” tri-blade fan to be installed in the living rooms of units. Their costcompetitive product is compact enough to match the scale of the living rooms, while providing excellent energy efficiency and thermal comfort. Winning Energy Star’s most efficient fan of 2023, their model is 6x quieter than traditional ceiling fans, something especially important in a mass-timber frame where acoustic quality is more difficult to achieve. Fans are remote controlled with six different speeds and a reverse operation, to cycle warm air back down during the heating season.

SECURITY

Occupants can feel secure in Solar Grid due to several active and passive strategies to make the building safe. The main entry in the lobby has a security room and checkin, where guests can check in, and unwanted guests can be vetted. All doors accessing the courtyard or exterior circulation have automated keycard access, so that only occupants may access it, or a building employee will supervise entry in special circumstances, like community events. The open U-shape of the building and vertical void cuts in the circulation allow occupants to see all sides of the building, creating a sense of accountability and community supervision. This employs the defensible space strategy that Oscar Newman championed at the building community level, without the consequences that result at a neighborhood level.

WATER HEATER

Our selection of a hybrid water heater saves 4x the amount of energy consumed by a traditional electric heater. Correct sizing allows us to service to units at once with just one heater, reducing total costs. Users can program the heater to match their needs throughout the day, coordinating higher production with higher use times in the day. A leak detection system prevents any more than 20 oz. of water escaping the tank. This system best complements the volatile weather of Columbia, which could be sunny and warm on one day, and snowing on the next.

PHANTOM PLUG LOADS

Our team decided to incorporate Bert plu load controllers and their associated softwares so that plug loads would be analyzed and automatically turned off when the space is vacant. The hardware can be used with HVAC and water heating, as well. Use of this system can improve energy efficiency by 50% with a payback in weeks. The design includes these in both the residential and the commercial spaces.

APPLIANCE SELECTION LAUNDRY

In order to conserve space, cost, and water and energy consumption, 6 washer and dryer units will be grouped together in one room on the second story. The area is adjacent to the elevator, so tenants do not have to haul their laundry down several flights of stairs. It is also located next to the communal kitchen and gathering area. Residents will be able to relax and engage with the other tenants while waiting for their laundry.

We selected appliances that were energy efficient, costeffective, and matched the scale and style of interior elements. The Forte 1 BR fridge can be built in with the casework, and consumes only 372 kWh/yr. Both Forte fridges are Energy-Star rated and use a lower-GWP refrigerant. The oven is cost-competitive and Energy-Star rated.

APPLIANCE SELECTION

Fridge (1 BR) Forte 9.2 ft3 built-in bottom freezer

Fridge (2 BR) Forte 17.5 ft3 counter-depth French door bottom freezer

Oven/Range GE 30” free-standing self-cleaning electric range

Forte fridge GE Oven

fig. 1.2 fig. 1.3

Aeratron tri-blade fan

COMFORT AND ENVIRONMENTAL QUALITY

INDOOR AIR QUALITY

Exposed single loaded corridors with strategically selected and placed windows allow air to pass naturally through residential units. Warm air on the street side is pushed through to the interior courtyard as it cools. The exterior circulation also serves as one large doormat where tenants shed many of the irritants that would otherwise enter their home. To ensure that indoor air quality remains healthy and comfortable in an airtight building, the Horizon DOAS system will be used to supply dehumidified outdoor air to interior spaces. Stale indoor air will be cycled out with fresh outdoor air with low moisture content. An integrated ERV will improve the overall energy efficiency of the system, recycling heat that passes through. The use of the Halo GPS sheathing allows whatever moisture is inside the building to flow to the exterior, preventing mold buildup. Typically, a vapor retardant would not be ideal with dense pack cellulose, however, Halo’s sheathing with a 5.0 perm rating allows moisture to exit the interior unlike other rigid board systems. At the same time, it repels moisture from the exterior into the envelope. This in conjunction with the DOAS system allows for an airtight, thermally comfortable interior.

DAYLIGHTING

The U-shape of the building allows every unit to receive, at minimum, 4 hours of direct sunlight a day. Daylighting will help make interiors feel more open, and lower energy usage of electric lighting. Setbacks in the facade creating shading opportunities, allowing in natural lighting but not too much direct daylighting. Interior blinds will help prevent glare when the sun is lower in the sky.

ELIMINATION OF TOXIC MATERIALS

To improve and maintain proper indoor air quality, our team mindfully selected interior materials and finishes. All wood products contain no formaldehyde content and all paints, adhesives, and coating contain low to no VOCs. The masstimber structure also reduces exposure to toxic materials during construction. As mentioned in the interior design section, our materials feature a number of verified certifications that also contribute to enhanced indoor air quality in the space. Our team also chose not to use carpet in the units because it can be a common source for asthma triggers. A green-wall in the lobby helps filter out unwanted materials in the indoor air.

ACOUSTIC CONTROL

Occupant’s privacy and relaxability were a large part of our design. One of the bigger challenges with mass-timber deal with acoustics. Because the system is so light, sound and vibrations easily pass through the structure and into

adjacent rooms. We found an assembly that meets both STC and IIC ratings at minimal material cost. Using the ECF cork underlayment with a 2” concrete pour will allow us to reach code minimums in both areas. An air cavity in between insulated inter-tenancy walls will prevent sound from transmitting horizontally from unit to unit. Fire-stopping in the stick framing and additional supplementation will prevent flanking sound from entering other units. We searched for appliances and HVAC systems that were quieter than their competitors. The Mitsubishi heat pump and Aeratron fan are signifacntly quieter than standard variations, and limit vibrations.

COMFORT AND ENVIRONMENTAL QUALITY

ENERGY PERFORMANCE OPTIMIZATION

We began by analyzing passive design strategies through sources like the “Passivhaus Detailing and Design Guide” and other passive design case studies. We used Autodesk’s Insight program in the early stages of development with a generalized building model to determine optimal placement of windows and shading to reduce our EUI. We then brought the model into cove. tool to calculate the whole building EUI under the conditions of AHRAE 2019 and the IECC 2021 energy code. After a careful selection of systems, operational hours and occupancies, we found our building to have an EUI of 27.83 kBtu/ft2/yr without PV. We then consulted with a local company, Dogwood Solar, on the type of panel we should use, and used the PVWatts tool

to determine the amount of surface area required for our array. Using the array originally sized for our roof and standard degradation rates, with a 20% irradiance loss in the winter months, we calculated that our array will generate an average of 576,946 kWh/yr, with a maximum output of 602,565 kWh/ yr. With inclusion of a PV array, our whole building EUI drops to -3.87 kBtu/ft2/yr, making Solar Grid not only a net-zero building but a net-positive building. Our EUI falls under the 4A multifamily target of 67 kBtu/ft2/yr, and under the Architecture 2030 target of 9.81 kBtu/ft2/yr. The positive energy generation can be reused to offset future energy bills with the city’s net metering program, and redistributed to help power the Armory.

Whole building EUI before PV

Whole building EUI after PV

fig. 1.1

fig. 1.2

ENERGY PERFORMANCE

PHOTOVOLTAIC ARRAY DESIGN

After consulting with Dogwood Solar, we found the most efficient panel they offered was the Maxeon 3 Commercial at 400W production and a 22.6% efficiency rate. 1080 panels gives an array surface area of 20,520 ft2, producing and average of 578,555 kWh/yr. Panels are on a fixed open rack system at a tilt of 20 degrees facing south. We chose the 20 degree tilt because it limited shading between panels and reduces vertical wind loads without a considerable loss in energy generation. The panels follow the shape of the roof, cantilevering 7 ft. on each edge to provide additional shade to the building and maximize panel placement. We raised our panels 10 ft. on a steel beam and post system attached in-line with the mass-timber structure beneath it. The steel system will support the aluminum rack system which the solar panels themselves will be fastened to. Some panels will need to be removed to accommodate the HVAC system’s air circulation requirements. The system saves approximately $58,000 a year on utilities, to the point that the building could make money using the net-metering program.

ENERGY STORAGE

Our solar array will be grid-tied with a backup battery system. A percentage of the excess energy will be diverted to a battery storage system to power the building when the PV generated energy is not enough to supply the whole building, or during a grid outage. The rest of the excess energy will be sold back to the grid and to power the neighboring armory.

DESIGN RENDERINGS

EXTERIOR EAST fig. 1.2

EXTERIOR WEST fig. 1.1

DESIGN RENDERINGS

COURTYARD fig. 1.3

MAIN LOBBY fig. 1.5

DESIGN RENDERINGS

SINGLE BEDROOM fig. 1.5