Sustainable Design

GeoConcept Geothermal, HVAC and plumbing Consulatnts

Experts Conseil en Mécanique du Bâtiment

Protect and Conserve Water

 

In many parts of the United States and Canada, fresh water is an increasingly scarce resource. A sustainable building should use water efficiently, and reuse or recycle water for on-site use, when feasible. The effort to bring drinkable water to our household faucets consumes enormous energy resources in pumping, transport, and treatment. Often potentially toxic chemicals are used to make water potable. The environmental and financial costs of sewage treatment are significant.

What is Sustainable Design?

Building construction and operations can have extensive direct and indirect impacts on the environment (Energy Efficiency), society, and economy, which are commonly referred to as the 3 P's ('People', 'Planet', 'Pocketbook'). The field of sustainable design seeks to balance the needs of these areas by using an integrated approach to create win-win-win design solutions.

 

The main objectives of sustainable design are to reduce, or completely avoid, depletion of critical resources like energy, water, and raw materials; prevent environmental degradation caused by facilities and infrastructure throughout their life cycle; and create built environments that are livable, comfortable, safe, and productive.

 

Buildings use resources (energy, water, raw materials, and etc.), generate waste (occupant, construction and demolition), and emit potentially harmful atmospheric emissions. Building owners, designers, and builders face a unique challenge to meet demands for new and renovated facilities that are accessible, secure, healthy, and productive while minimizing any negative impacts on society, the environment, and the economy. Ideally, building designs should result in net-positive benefits to all three areas.

 

While the definition of sustainable building design is constantly changing, four fundamental mechancal principles persist:

  1. Optimize energy Use.
  2. Protect and conserve water.
  3. Enhance Indoor Environmental Quality.
  4. Optimize Operational and Maintenace Practices.

Optimize Energy Use | Energy Efficiency

 

With continually increasing demand on the world's fossil fuel resources, concerns for energy independence and security are increasing, and the impacts of global climate change are becoming more evident, it is essential to find ways to reduce energy load, increase efficiency, and maximize the use of renewable energy sources in facilities. Improving the energy performance of existing buildings is important to increasing our energy independence. Government and private sector organizations are increasingly committing to building and operating net zero energy buildings as a way to significantly reduce our dependence on fossil fuel-derived energy.

Enhance Indoor Environmental Quality (IEQ)

 

The indoor environmental quality (IEQ) of a building has a significant impact on occupant health, comfort, and productivity. Among other attributes, a sustainable building maximizes daylighting, has appropriate ventilation and moisture control, optimizes acoustic performance, and avoids the use of materials with high-VOC emissions. Principles of IEQ also emphasize occupant control over systems such as lighting and temperature.

Optimize Operational and Maintenance Practices

 

Considering a building's operating and maintenance issues during the preliminary design phase of a facility will contribute to improved working environments, higher productivity, reduced energy and resource costs, and prevented system failures. Encourage building operators and maintenance personnel to participate in the design and development phases to ensure optimal operations and maintenance of the building. Designers can specify materials and systems that simplify and reduce maintenance requirements; require less water, energy, and toxic chemicals and cleaners to maintain; and are cost-effective and reduce life-cycle costs. Additionally, design facilities to include meters in order to track the progress of sustainability initiatives, including reductions in energy and water use and waste generation, in the facility and on site.

 

Geothermal Heat Pump System - Horizontal and Vertical Closed Loop System

Geothermal heat pumps (GHPs), sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps use the constant temperature of the earth as the exchange medium instead of the outside air temperature.

 

Depending on latitude, ground temperatures in major Canadian cities range from 46.4°F (6°C) to 50°F (10°C). Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.

 

As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some North American models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Japanese models of Geothermal systems (such as Mitsubishi and Daikin) are available with Variable Refrigerant Volume (VRV) compressors and Variable Fans for the best comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.

 

Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5 to 10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. Payback Period varies from Canadian City to another depending on the utiliy company billing scheme and average soil thermal conductivity.

 

As a rule of thumb:

  1. Payback is the highest in the province of Quebec where electricity is cheap compared to other provinces (around 10 years for commercial buildings and around 12 to 14 for residential buildings) and the lowest in Ontario (around 5 to 10 years).
  2. A Closed Loop Geothermal Heat pump reduces Building's Enveloppe Heating/Cooling energy demand by two third.

 

Sustainable Design Ideas

Indoor Living Wall

A living wall is a vertical arrangement of green plants having their roots in a wet growth synthetic media. The more sophisticated version of a Living Wall is having an air plenum behind the growth media that is either connected to the return air of the space HVAC system or or equipped with its proper fans sending filtered and humidifed air into the air space ceiling.

 

The negative pressure in the Living Wall's aluminum air plenum forces the air surrounding the wall to pass through the following consecutive layers:

  1. Plants act as a biofilter and oxygen generator which improves the indoor air quality .
  2. Wet synthetic growth material where air is humidified by a continuous water flow from top to bottom. Water (minus the portion absorbed by air flowing through the living wall) is recuperated in the catch basin and recirculated thorough the living wall (pumped up to the top of the wall).
  3. Aluminum air plenum holes where humidified air is channeled to the air-handling unit return air duct or to the ceiling of the surrounding air space .

 

In general, Air flows thorugh green wall at an avereage of 20 Cubic Feet of Air per minute. Relative Humidity gain thourgh Living Wall varies between 18% and 25% .

 

Humidifcation process through living wall is an adiabatic process, which means that air enthalply is the same at the entrance and exit of the living wall. Unlike Steam Humidifiers, living wall's humidifcation process, consumes zero net energy . The Heat present in the dry air when passing through living wall is released to vaporize water in wet growth media. Air abosorbs vaporized water and its temperature drops between 7 to 8°F .

 

Heat released by dry air has to be compensated by Air Handling Unit Heating Coil in winter. In summer, the temperature decrease contribute to the free sensible cooling of air but increases Air hanling Unit Latent Cooling Load.

As an example a 22.3 m² living wall adds 12 KW of heating load to the space air handling unit heating demand, which will increase space humidity by 18.7% (from 12% to 30.7%). Generating the same amount of water vapour, using a steam humidifier, to produce the same relative humidity increase requires 22.2 KW of heating load.

in light of the above, a 22.3 m² Living Wall's energy saving in Winter is 22.2-12 = 10.2KW.

For more Info about living wall, please refer to this ASHRAE - April 2017 Article that was authored by one of our associates