An Introduction to the HVAC Engineers' Role in Sustainable Design, Implementation and Operations
From the design concept to construction and from construction to the operation of buildings, mechanical engineers play a vital role in creating sustainable buildings. They do so by putting together the most feasible systems that work in coordination with other disciplines to meet projects' requirements within the client's budget.
Sustainable building designs have become essential and need to be taken into consideration sooner than later. Investments in green building designs shall lead to a very positive impact in the near future for everyone, be its occupants, the environment, utility providers (Government /Private) as well as for the client or real estate owners.
Education and realization by taking timely decisions at the right time is the key to initiate; however, up gradation of existing buildings into green buildings is also achievable but with certain limitations.
Valuable energy resources could be saved or well utilized if like-minded team of engineers, work with due diligence by paying adequate attention to detail as they explore and implement the relevant techniques to achieve a common sustainable goal.
Seamless integration of the functions along with aesthetics, without compromising the building services features (especially the sustainable aspect of it) are among certain challenges often faced by architects, however, overcoming them would be worth the effort.
Critical Roles of an HVAC Engineer
Although it is a broad topic, let's briefly touch upon few critical points governed by the Local Energy Code in place of project as well as International Codes & Standards whichever more stringent shall be followed:
- HVAC Engineers have various responsibilities that are not just limited to calculations.
- HVAC engineers can contribute to enhance the quality of indoor air that we breathe in, save energy, improve building operations and design buildings that are more smart, environment friendly and energy-efficient.
In summary, making the most of the available natural resources in the best possible manner is about doing justice towards the preservation of the environment.
HVAC Engineers in Healthcare Project
For instance, one of the services that HVAC engineers take care of is designing healthcare facility, supervising its construction and ensure intended operations.
Such facilities require sophisticated coordination and special attention by adhering to safety codes and standards for the well-being of medical staff, patients and visitors.
HVAC engineer shall in particular check following:
- Pressure requirements (positive or negative)
For areas with pressure requirement to have fully ducted return or exhaust provision, use of venture-valves for more accuracy;
- Thermal comfort and air changes requirements
May require re-heating to achieve both of above;
Filter banks, Use of HEPA or ULPA filters;
- Ultra-Violet (UV) germicidal light;
- Appropriate service access doors
for routine service and maintenance;
- Following hygiene standards and air-velocities on patient bed in operation theatre (OT), use of laminar flow diffusers where applicable;
- Outside air and exhaust requirements;
- Indoor temperature and relative humidity;
- Design controls to monitor and ensure required pressures maintenance under all conditions (especially for Operation Theatre (+)VE, Airborne Infectious Isolation (AII) Rooms (-)VE, Use of hygienic ducts and use anti-microbial coatings.
- Fulfilling other Medical Equipment requirements from equipment datasheets such as Laboratories hood and Radiology MRI requirements etc.
It is preferred to select high heat-generating hospital equipment to be with water-cooled condensers to save fan energy. Or equipment with remote condensers located in the outdoors where the condenser entering air shall be taken into consideration as per local ambient conditions.
HVAC Engineers in Kitchen / Laundry/ Fire / Smoke and Acoustics Design
The design and ventilation requirements would vary for different facilities such as kitchens and laundries. The HVAC engineer would need to work with the kitchen and laundry consultants to understand the following:
- the hood requirements;
- kitchen ecology unit inter-locks;
- Systems sequence of operation;
- smoke Management systems;
- Dampers on firewalls or combination of motorized fire and dampers to serve designed smoke management system; and
- Acoustics issues and their solutions,
The HVAC engineer must know how to place the units in the right location to minimize airborne noise or use sound attenuators or acoustic linings or in acoustic enclosure or box, acoustical louvers. The Designs shall comply with both energy and fire/smoke code compliance.
The examples mentioned above prove that the role of HVAC engineers is vital for different types of projects. Thus, knowing high-rise towers or hotel requirements (Mid floor mechanical floor with Plate heat exchanger for break pressure), commercial malls, residential, industrial and special projects will have unique requirements that will differ from one project to another.
Optimizing the Building Envelope
Architects and HVAC engineers must work together on the building envelope's optimization to select a combination of wall layers with lower heat transfer coefficients (also referred to as U-value) or by simulations to determine the most energy-efficient envelope load. The lower the U-value, the lower the heat shall transmit into the building. As a consequence, the building will need smaller HVAC plants to meet the cooling or heating requirements.
From the HVAC point of view, more fenestration is preferred on northern exposure and least towards the south as it brings indirect Sun and solar radiation. If fenestration is a must on the south-facing facade, multiple solutions can apply to minimize the heat gains and have an energy-efficient building envelope such as:
- Using overhangs to consider shading
- Applying transparent coatings to the glass to reduce or reflect solar radiations
- Using triple or at least double glazing on areas where the window to wall ratio is higher
- Considering the landscape design of the surrounding area as trees and other shading devices may help
- Using an HVAC plant of variable speed drive compressors with inverter or chiller with variable speed drive compressor, and variable flow chilled water pumps with pressure independent control valves modulating as per load requirements.
- Use of thermal energy storage and cooling towers with variable frequency drive fans;
- Using CO2 based demand control ventilation with motorized dampers connected to Air Handling / Fan Coil Units return for energy savings;
- Use of ECM (Electronically Commutated Motors) that consumes less power' and finally
- Use of TES (Thermal Energy Storage) water for cooling towers to save potable water all these small bits added can also make a big difference.
Applying these solutions will demonstrate a significant improvement in the energy savings of a building. According to the ancient Chinese Proverb, "A Journey of a thousand miles begins with a single step".
Indoor Air Quality to Humans
As fish live and breathe in the ocean. Likewise, as human beings, we live in an ocean of air all around us. Therefore, the quality of air that we breathe in is very crucial and as has tremendous effects on the overall performance at the workplace and health.
Using proven indoor air cleaning plants would further help in reducing the pollutants from the air stream. Filtered and dehumidified air should meet the ASHRAE 62.1 2019 or other relevant standards to meet outside air requirements. Recovering the Exhaust air is also essential and can be achieved by using Heat pipes, thermal wheels, run around the coil, plate heat exchanger whichever most suitable for the project. The recovered energy shall pre-cool the incoming air, which will reduce the load on the cooling coil; hence, the cooling plant. During dehumidification, using the condensate water from cooling coils for irrigation purposes or other useful purposes is an option. Finally, controls are of equal importance; there comes in BMS (Building Management Systems).
Applying Controls Using BMS
Fresh air handling units fan shall be modulated to give constant supply when filters become dirty to overcome resistance until filters in dirty alarm status to monitor airflow (Airflow measuring station) shall be installed. During off working hours, units shall operate at 50 %, thus lowering the operational cost by saving energy. Installing Occupancy sensors in meeting rooms interlocked with fresh air motorized dampers to Fan Coil Unit / Air-Handling Unit Return can also help regulate the supply.
The building shall be maintained under slightly, positive pressure to avoid infiltration of outside hot and humid air. CO sensors can be installed in the car service area if the concentration of gas exceeds certain limits. Fans can operate to dilute the air until it becomes within the acceptable range limit to protect workers from being exposed to hazardous gases, Refrigerant leakage detection (RLD) system.
Additionally, HVAC engineers need to take measures to the exhaust air not to add pollution, let it be air pollution or noise pollution. Noise related briefly already discussed above. Air shall be exhausted in a manner where it does not return to the building ventilation system and use carbon, grease filters, Kitchen Ecology Unit or HEPA / ULPA filters for isolation rooms or as necessary.
The BMS shall give an alarm and identify the unit with a dirty filter, so the maintenance team may attend it at the earliest ensuring clean, free of dust and pollen supply of air to the occupants.
World and companies around the globe are striving to be pioneers and come up with solutions that are greener than their predecessors. Like exploring the use of Refrigerant Ref-32 in chillers in the future as it has lower GWP (Global warming potential) and ozone depletion potential (ODP). Moreover, the heat from Air-conditioners condensers can be used to heat water.
In conclusion, the above article provided descriptive information on the role of an HVAC engineer in achieving a sustainable building. This shows that a lot can be done as an individual and in a collective effort to leave a better and sustainable future for the coming generations.