Sustainable Design in Mechanical Engineering

Image: The Grand Rapids Art Museum is the first LEED Gold Certified Art Museum in the world. Our team has also helped GRAM plan for carbon neutrality.

For over 60 years, Progressive Companies has been committed to innovative and sustainable designs that benefit our clients and communities. In this blog series leading up to Earth Day, we’ll share knowledge and best practices we’ve learned along the way. 

everyday technologies and equipment that can be applied to multiple types of buildings without stretching the budget or requiringThis installment will focus on best practices for limiting operational carbon produced through mechanical systems like heating, cooling, and plumbing.  

Systems 

We want to discuss some of the tried and true, everyday technologies and equipment that can be applied to multiple types of buildings without stretching the budget or require an advanced degree to run and maintain.   

HVAC 

When it comes to reducing operational carbon in the HVAC system, we need to focus on reducing energy use. The best way to start is to focus on having an extremely efficient building envelope so that the energy required to heat and cool the building has been minimized. An efficient envelope means analyzing the optimal combination of insulation, solar orientation, and glazing types and locations. At PAE, the design team uses an early energy modeling tool, cove.tool, to compare different iterations of the building throughout the design process. So, at the point where HVAC systems selection occurs, the building envelope has been optimized based on the site constraints, architectural design, and heating and cooling demands. 

Once we’ve done everything we can with the envelope, there are a number of strategies we can use to improve the efficiency of heating, cooling, and ventilation systems.  

One of these systems is called variable refrigerant flow or VRF. VRF has become more popular over the last decade due to its energy efficiency but also its temperature control for several spaces. While there is a cooling-only or heating-only version, heat recovery VRF is the more efficient of these system types. Heat recovery VRF essentially uses the heat rejected in one room (say, a conference room during a meeting) to heat a cold corner office and so on throughout the building. This trade-off of heating and cooling between rooms avoids the need to use additional energy to create or reject heat. Instead of one large air handler, a VRF system uses many smaller units throughout the building that respond to the needs of the space and provide both heating and cooling. Although the cost of VRF is higher upfront than, say, a competitive furnace and condenser system, it can provide up to 50% energy savings.   

There is also a push within our industry for refrigerants to be more climate-friendly. Newer refrigerants not only meet the requirement for ozone depletion potential, they also significantly reduce the global warming potential as well. As HVAC manufacturers are phasing out the banned refrigerants, existing equipment can be retrofitted with new refrigerants (at some loss of capacity) or replaced in kind.  

Another sustainability strategy we can use in HVAC is known as displacement ventilation. Displacement ventilation supplies air at low velocities from low points in the room. The cool air is delivered right where people are rather than traditional overhead supply systems. This allows us to supply slightly warmer air due to both comfort and the buoyancy effect, reducing the energy required to cool the air. This can be especially effective when using passive systems for reheating after dehumidification. This system also lowers the amount of outside air required for the space due to distribution right to the breathing zone, reducing the energy spent conditioning the outside air. A good tool to pair with this is an economizer, which allows you to use more unconditioned outside air when conditions are good. We recently used this strategy at Frederik Meijer Gardens’ new welcome center. 

We can also save energy with an airside recovery system such as an air-to-air desiccant energy wheel or core. These systems capture conditioned air that would normally be exhausted from the building and use it for preconditioning the outside air transferring the heat from one airstream to the other.    

Controls 

In addition to the system itself, the way a system is controlled also affects its efficiency. Well-written controls systems can prevent wasting energy with simultaneous heating and cooling or running equipment when the building is unoccupied. We mentioned using an economizer, which allows us to utilize the colder ambient temperatures for cooling rather than mechanically cooling. Another control option is demand control ventilation. Sensors track CO2 or other air contaminants or occupancy and adjust the amount of outside air in relation to the contaminant level in the space. This prevents the system from bringing in excess outside air and eliminates the associated costs of treating it.  

In a recent healthcare project, we linked the occupancy sensor provided by the lighting control panel to the HVAC system. If there is no occupant in the space, it will adjust the temperature and set the terminal unit to minimum airflow to avoid cooling an empty room which will save energy usage.  

Electrification 

Electrification refers to the move towards electrically powered mechanical systems in an effort to reduce reliance on fossil fuels. Some of the ways we can achieve this are through wind, solar, or geothermal energy (we’ll explore these more in-depth in our next installment on electrical engineering). 

A building’s heat pump is a good example of something that can be powered electrically. A ground source heat pump system provides the best efficiency when properly implemented, although it may not be practical in every scenario. Water or air source heat pumps are a less efficient but also less expensive alternative that can be implemented regardless of climate and soil conditions. Our team works alongside each client to select the system that makes sense according to their budget, site, and sustainability goals. 

Plumbing & Water Management 

Low-flow plumbing fixtures have become standard practice, which you will see in most new constructions and remodels, but we have other ways of saving and reusing water as well.  

Rainwater cisterns, condensate collection, and graywater systems are other ways to reclaim and reuse water that would otherwise go to waste. These systems can supply non-potable water for irrigation, toilet flushing, and cooling tower make-up water.  

Hot water recirculation routed as close to the plumbing fixture as possible (especially in healthcare) is becoming a necessity, where hot water is circulated on a closed loop rather than being constantly heated from cold. Not only does this save energy costs, but it prevents bacteria growth within the system and allows instant access to hot water rather than having to run the faucet until there is hot water.  

Our team is always looking at creative ways to reduce our environmental impact and we love helping clients meet their sustainability goals. Contact us if you’d like to talk with one of our design experts about your project.