The engineering team approached the design of LEAFHouse systems with the goal of reducing the impact of the building on the environment while creating a comfortable, responsive living environment and merging the systems seamlessly with the architectural design.
In an effort to fuse sustainability and livability, the University of Maryland LEAFHouse utilizes a wide range of unique engineering techniques. With its blending of biological sensitivity and cutting-edge technology LEAFHouse creates a living experience like no other. The LEAF House was designed not only to cater to its inhabitants but also to minimize the footprint on its own environment. Through the hard work of many, the LEAFHouse is proud to present unique methods of powering, heating, and controlling your home.
The building’s skin is made up of wood, glass, vegetation, and corrugated metal applied to 2x6 wood stud walls filled with soy based spray foam insulation. There is a twenty-two foot, four-panel sliding glass door system which allows the sun and the environment to enter the household. There is also a translucent polycarbonate skylight running the full length of the ridge of the house in order to provide diffuse light into the house.
One of the most unique aspects of LEAFHouse is the application of its desiccant dehumidification. In order to decrease the normal electrical load associated with traditional dehumidifiers , LEAFHouse utilizes a liquid desiccant dehumidifier. This system uses very little electricity and is a highlight of the indoor décor. The desiccant that is used in LEAFHouse is a Calcium Chloride solution that is a safe, odorless chemical that naturally absorbs moisture. When moisture is absorbed from the air, the compound heats up and is pumped to a reservoir near the roof of the house. Here it releases its heat and regenerates around 170 F (76.6 C). The desiccant dehumidification system is located in the living room of the house and is the focal point of the room.
In order to control the environment of the house, LEAFHouse is equipped with a Smart House Adaptive Control System. This system gives the occupants the ability to interact with the house and track the house’s conditions from a web based interface. The conditions can be viewed in real time and adjustments can be made in order to optimize energy use, humidity, light, and water consumption. SHAC allows the house to be maintained efficiently and economically through its automated control system that performs tasks and monitors the house based on collected data.
LEAFHouse uses radiant heating to control the temperature in the house. It has heating panels in the floor in order to take advantage of heat rising. This system uses Cross-Linked Polyethelene (PEX) tubing grooved into Medium Density Fiberboard (MDF) panels. This system enables efficient heating of the house at a low cost and takes advantage of thermodynamics to control the living environment. The house is cooled by a ductless mini-split system. This system is set up as an auxiliary heat pump, which utilizes refrigerant lines and a fan to cool or heat the air. It will be set for 74 degrees Fahrenheit, causing it to heat or cool the air when necessary. The ductless mini-split system is run off of ozone friendly refrigerant, R410a. There are two fans, one in the bedroom and one on the south facing wall of the kitchen.
The key to the success of LEAFHouse lies in the photovoltaic (PV) cells that convert solar energy into electricity. To make LEAFHouse fully self-sustainable the design maximizes the effectiveness of the solar arrays. Thirty-four solar panels are arranged on racks across the roof in three independent circuits. The panels on the east side form one circuit, the panels in the middle form another, and the panels on the west form the third circuit. The division of panels maximizes power production during sunrise and sunset when the intensity of light on one side of the roof will be much higher than the far side. The design calls for thirty-four panels, each rated to produce a maximum output power of 205 watts. Each panel weighs 31 pounds and produces a maximum open circuit voltage of 68.7 Volts. The panels are rated for an overall efficiency of 17% making them sufficient for LEAFHouse‘s needs and budget requirements. Batteries and Inverters comprise two other key elements to the electrical system. LEAF House has 48 twelve volt batteries stored under the deck that are capable of powering everything in the house for four full days. The sealed lead acid batteries are divided into groups of four, connected in series, to produce a total voltage of 48 volts, thereby maximizing the efficiency of the inverters. Thirteen of these groups of four are wired together in parallel strings to increase the amount of current that can be drawn by the system at any time. LEAFHouse’s have a low hydrogen leakage and can each steadily produce 250 Amps for 20 hours. PV cells and batteries produce and store electricity as direct current, but almost all appliances are designed to run on alternating current. LEAFHouse uses four Flexware 100 power inverters to provide the appliances with usable alternating current. The inverters are compatible with fully off-grid systems as well as grid integrated systems.
The highlight of LEAFHouse plumbing includes the greywater and rainwater collection systems. Rainwater is collected and re-circulated through a series is vertical and horizontal rain gardens. These gardens filter and retain the grey water which reduces the waste produced by the LEAF House. LEAFHouse is focused and committed to the retention and collection of rainwater and greywater on site. Greywater from the house is used for irrigation in a grey water garden. Runoff from the roof is plumbed in to the vertical green wall, a prominent feature on the house’s south façade.