Students test the limits of sustainable construction with a tiny net-zero energy and water house
By Jillian MorganConstruction Green Technology HVAC Systems
The Northern Nomad claims a mere 220 square feet of Carleton University campus in Ottawa, ON. An emblem of sustainable construction, this tiny house is big on efficiency.
Built by a group of students to withstand the northern climate, the Nomad is designed to achieve three goals: annual net zero energy, on- and off-grid operation and water autonomy.
“The purpose of the project kind of shifted throughout the different phases. The original idea was to design a net-zero water and energy house,” said Seungyeon Hong, a graduate student managing the project. “That has been made the embodying goal but throughout we’ve been experimenting with different technologies and even building materials and equipment.”
In the fall of 2016, a group of five fourth-year engineering students dreamed up the Nomad as part of a fourth-year capstone project under the supervision of Scott Bucking, assistant professor in building information modeling.
Bucking recruited a number of students from various disciplines to bring the project to life, including architecture, architectural engineering, sustainable renewable energy engineering and civil engineering.
“It’s a very organic, non-structured design process because our experiences are limited,” Hong said. “Everybody brings in a bit of expertise from different fields.”
Construction started in the summer of 2017. The floors, walls and roof of the house were installed first, followed by electrical components, windows and doors. Vacuum insulated panels were placed in the roof, floor and parts of the walls. The home was then spray foamed with polyurethane insulation. Rigid extruded polystyrene insulation was installed on the exterior face of the house before the exterior finish was applied. Inside, the ceiling is composed of reclaimed barn board planks and the walls are pine.
“On the plumbing side, it’s the same idea as on-grid, off-grid that applies to energy,” Hong said. “You can imagine it as the same system as an RV, where you can hook up the city water and use city water pressure. Ours does not hook up to the city water, we have a small pump that will pressurize the house at 30 psi.”
DS Plumbing, based in Ottawa, helped the team install five rainwater tanks, totalling 900 litres of water storage. The tanks store water that has been filtered through an atmospheric water generator (AWG). Hong said AWG is a “fancy word for pulling moisture out of the air and filtering it to make it potable.”
“Instead of using rainwater capture, which is great, we wanted to produce water on demand, which helps with the building autonomy,” he added. “If you were to deploy this house somewhere, energy is taken care of, but what about water?”
For heating, Ottawa-based HVAC contractor ClimateWorks was enlisted to install a Mitsubishi Electric mini-split heat pump. Designed to run down to -25 C, the unit is “3.5 times more efficient than electric resistive heating,” Hong said. “The heat pump was essential for us to go completely sustainable,” Eric Ho, a fourth-year student in charge of mechanical systems and smart home features, said.
Ventilation, heating and cooling are all coordinated with an energy recovery ventilator through a smart thermostat. Another aspect of the heating and cooling system leverages building-integrated photovoltaics.
“In our house, our solar panels are the roof and there is a ventilation air gap underneath,” Hong said. “That air gap allows air to flow through and cools the solar panels. What that means for that air is that it is heated up. We can take advantage of that air, which is two degrees hotter than the ambient air inside the house, and we can save energy by using what you could call ‘free heating.’”
At night, the panels are cooler than the ambient air, meaning the air that flows under the panels can be used for cooling,
Now complete, the tiny house is equipped with more than 200 sensors, which will monitor temperature, humidity and pressure–among other measurements–to ensure it achieves net-zero status.
“We have software students who will coordinate these things and write the code for the control systems and what not,” Ho said. “There’s many different aspects of research made available by this project” <>