Box House Photographed by Alejandro Cartagena
During my co-op work term in Spring 2021, I had the opportunity to collaborate with Masonry Works and CCMPA on their research regarding the viability and integration of Concrete Masonry in Sustainable Building practices, with a specific focus on PassiveHouse and Net-Zero Energy. The primary objective of this research was to challenge the prevailing perception of concrete masonry in sustainable building design, considering its carbon emissions during the curing process, which has often led to its disfavor within the architecture community.
Under the supervision of Andrew Payne, Executive Director at Masonry Works and Executive Director Canadian Concrete Masonry Producers Association throughout my work term, I conducted comprehensive research on concrete masonry as a building material, examining its performance in five key aspects: Embodied Carbon, Thermal Mass, building envelope, building lifecycle, and durability. Armed with this knowledge, I embarked on designing a residential prototype and its building envelope, aiming to showcase the potential of Concrete Masonry Units (CMUs) in PassiveHouse residential construction.
To support my design proposal, I utilized energy calculation tools such as cove.tool and THERM to quantify the energy efficiency and performance of the CMU-based design. By combining theoretical research, practical design, and energy analysis, I aimed to contribute to the ongoing conversation surrounding sustainable building practices and highlight the potential of concrete masonry as a viable option for achieving energy-efficient and environmentally conscious structures.
Architectural Design
The illustrated design below showcases a prototype of a single-family house, catering to a family of 5 members. The primary concept focuses on creating open and unobstructed spaces that seamlessly blend with the surrounding environment. The design takes into consideration the residents' daily needs and activities, ensuring thoughtful accommodations. Moreover, it embraces flexibility, allowing for adaptability and accommodating potential changes in the future.
Excerpt from the published brochure on the design's location
Ground Floor: The main level, elevated 600 mm above the ground, includes essential living areas for the owners and guests. Upon entry from the north, a double-height foyer with a closet leads to a strategically placed guest powder-room serving the kitchen, dining, and living room areas. The open kitchen seamlessly connects with the dining area, and a spacious pantry connects to the laundry room. The south-facing living area maximizes natural sunlight and provides access to the backyard.
First Floor: At an elevation of 3600 mm, the upper floor offers private spaces for the homeowners. Ascending the U-shaped staircase, a sunlit corridor leads to west-facing bedrooms and a shared bathroom. On the south side, there is a primary suite and a master bedroom.
The Clerestory: The Clerestory level, occupying half the area of the floors beneath, features a recessed southern façade with eye-level windows. This clerestory design maximizes usable space, height, and natural light. The space serves as a solarium or sunroom with a cozy office and a bathroom, emphasizing flexibility and minimal walls.
Basement: The favorable soil condition in the geographical area allows for safe excavation and the inclusion of a basement floor in the design. The basement features a straightforward floor plan comprising an open space, storage area, and a mechanical room. This layout ensures flexibility to accommodate the homeowners' specific needs.
Roof Plan: The roof design incorporates a simple pitched roof with a 10% slope. A skylight positioned over the double-height foyer allows natural light to penetrate all the way down to the ground floor, enhancing the overall illumination of the space. Additionally, the south-facing section of the roof is equipped with inclined photovoltaic panels. These panels serve as the primary energy source for the house, aligning with the Net-Zero Energy goal and promoting sustainable energy generation.
Passive Strategies
Passive strategies harness the natural elements and features of a building site, such as sunlight, wind, orientation, insulation, and windows, to maintain comfortable indoor conditions without relying on purchased energy. By integrating these strategies into the architectural design, buildings can benefit from nature's provisions while minimizing energy consumption.
The building design incorporates key elements and strategies for enhanced energy efficiency and comfort. The overhang roof extends the pitched roof by 600 mm, providing shading and protecting the building facades from rainwater. This improves the durability of the materials.
A clerestory roof features higher windows to allow ambient light while minimizing direct sunlight. The operable windows promote fresh air circulation and contribute to passive design. Positioned in front of a thermal wall, it ensures interior thermal comfort.
A skylight on the north side reduces the need for artificial lighting, supporting energy efficiency.
Photovoltaic panels on the inclined roof take advantage of the primary sun path to the south. These panels serve as a cost-effective renewable energy source.
The design includes energy-aware strategies such as solar tempering, insulation, sealed building envelope, energy-efficient openings, VRF and Geothermal heating systems, fresh air circulation with ERV systems, and energy-efficient lighting, appliances, and electronics.
The open southern facade maximizes sunlight penetration, and recessed openings prevent discomfort and heat retention. These design choices promote sustainability and occupant comfort.
In summary, these design elements and strategies optimize energy efficiency and create sustainable buildings while ensuring a comfortable indoor environment.
Corresponding Openings
The direction of the prevailing wind in the project’s location is due west. Tall, floor-to-ceiling windows are placed on both east and west facades, correspondingly to allow a continuous current of air inside the house whenever windows are open. This design move helps keep the interior air fresh and circulating, also provides natural ventilation to spaces, reducing the dependency on energy-consuming systems.
The direction of the prevailing wind in the project’s location is due west. Tall, floor-to-ceiling windows are placed on both east and west facades, correspondingly to allow a continuous current of air inside the house whenever windows are open. This design move helps keep the interior air fresh and circulating, also provides natural ventilation to spaces, reducing the dependency on energy-consuming systems.
Thermal Walls
The CMU Envelope acts as a thermal wall in this proposal to expand on concrete masonry's thermal mass potentials. The material has unmatched thermal mass properties, giving it a significant edge against other building materials. Thermal mass helps maintain comfortable interior temperatures year-round. Concrete block absorbs heat from the sun during the day and radiate it out as the temperature drops in the afternoon throughout the evening. The thermal wall is continuous throughout the floors, from the attic, where it is exposed to sunlight from the clerestory to store heat, and goes all the way down the building's height, radiating heat into all the rooms throughout the levels. This material property is optimum for Passive House design, where it manages solar gain. (PassiveHouse Standard V)
Building Envelope
The building envelope is the enclosure that includes all the building components, separating the indoors from the outdoors. It includes the exterior walls, foundations, roof, windows, and doors.
The construction material chosen for this project is concrete block (CMU). Load-bearing walls consist of 6" CMU full blocks (6" x 8" x 16"). A self-adhered water, air, and vapor resistant membrane called BlueSkin is used as a weather barrier to protect the building from water infiltration. Continuous thermal insulation, achieved with 10-inch extruded polystyrene (XPS), is integrated into the wall assembly to meet Passive House standards and provide a high R-value.
Thermal Insulation: Continuous thermal insulation is a key requirement for Passive House standards and contributes significantly to achieving Net Zero Energy. By incorporating 10 inches of XPS insulation with an R-value of 27, energy usage and costs are reduced, and occupants enjoy enhanced comfort. Vermiculite is used to fill the CMUs, addressing thermal bridging caused by brick ties or shelf angles.
Air-Tightness: The building envelope is designed to be highly airtight, utilizing the BlueSkin membrane to securely wrap around the building, windows, and doors. This minimizes unintentional air leakage through the envelope.
Rainscreen: A double-façade rainscreen system is implemented to provide ventilation and mitigate water infiltration. The system includes a 30 mm air cavity to allow any water that enters through the exterior brick cladding to dry up before causing further damage to the envelope components.
Windows: High-performance triple-glazed windows with airtight and thermally broken frames, along with low-emissivity glass, are selected. These windows are estimated to save 20-30% of energy usage.
Exterior Cladding: Brick veneer is chosen as the exterior cladding material due to its durability and aesthetic appeal. Thermally broken metal ties are used to connect the bricks, repeating every other two bricks. A thermally broken shelf angle supports the weight of the cladding and transfers it to the building's foundation.
Roof: The unventilated roof has a 10% slope and is designed to withstand snow loads. It features double the insulation used in the walls, achieving an R-value of 60 for a tight envelope. BlueSkin membrane is applied twice to protect against air, water, and vapor penetration.
Assembly Details
The detailed drawings below illustrate how the floor and wall assemblies work together to provide an optimum enclosure as well as the installation of fenestration in the design.
Building Performance
A Brochure explaining the project and the outcomes was published by Masonry Works & CCMPA.