Hvac Systems: Reducing Air Pollution, Improving Air Quality

Poor indoor air quality (IAQ) can have a significant impact on health and productivity, causing symptoms such as headaches, itchy eyes, and irritation of the nose, throat and lungs. In some cases, it can even lead to the development of illnesses such as cancer, stroke and diabetes. As people spend approximately 90% of their time indoors, it is crucial to address IAQ issues. HVAC systems play a vital role in maintaining good IAQ by controlling temperature, humidity and air quality. While air conditioners do not directly purify the air, they can improve IAQ by circulating and filtering indoor air, maintaining humidity levels, and providing adequate ventilation. Additionally, newer HVAC technologies, such as UV-emitting lights and HEPA filters, can further enhance IAQ by reducing bacteria, mould and other fine particles.

Air purification technology

Ultraviolet (UV) Technology:

• UV-emitting lights, specifically UVC lights, are effective in destroying contaminants on surfaces and killing microbes.
• UVC lights installed within HVAC systems help keep the equipment free of pathogens and reduce the risk of spreading them throughout a building.
• UVC technology is commonly used in healthcare facilities and is increasingly adopted in schools, senior living facilities, and public transit systems.

High-Efficiency Particulate Air (HEPA) Filters:

• HEPA filters are designed to trap a high percentage of particles in the air, including dust, pollen, and smoke.
• These filters are rated using the Minimum Efficiency Reporting Value (MERV) scale, with higher ratings indicating better particle-blocking capabilities.
• HEPA filters are recognised by organisations like OSHA and the EPA for their effectiveness in removing airborne particles.

Oxidation and Ionization Technology:

• Oxidation and ionization air purifiers go beyond surface contamination by destroying particles in the air, both within the HVAC system and throughout the indoor space.
• This technology converts oxygen molecules into charged atoms that cluster around and deactivate harmful substances like mould, bacteria, allergens, and viruses.
• Commonly used in healthcare facilities and food processing plants, these purifiers can significantly enhance indoor air quality in various spaces.

Variable Refrigerant/Refrigerant Flow (VRF) Systems:

• VRF systems offer the ability to create different climate "zones" within a building, allowing for precise humidity and temperature control in each area.
• By maintaining optimal humidity levels, VRF systems help reduce indoor air pollution as high humidity can promote mould growth, and low humidity can favour virus survival.

Demand-Controlled Ventilation (DCV):

• DCV utilises carbon dioxide (CO2) sensors to estimate occupancy levels in a space by measuring CO2 concentrations.
• Based on occupancy, DCV adjusts the amount of air supplied to the space, reducing energy consumption in unoccupied rooms.
• This technology not only saves energy but also ensures that building occupants are not exposed to elevated CO2 levels.

Good ventilation design

For instance, exhaust fans can help to remove fumes from manufacturing activities, as well as the use of chemicals or other materials. They can also reduce the concentration of virus particles that may be present in the air.

There are a few ways to improve ventilation:

• Relocating intakes
• Moving ductwork
• Adding HVAC technology, such as make-up air units for restaurant kitchens

A make-up air unit is usually installed on the roof or in a mechanical room. It replaces the air that has been pulled out by the kitchen's exhaust hood. The make-up unit pulls in fresh air from outside, heats or cools it to the indoor temperature, and supplies it to the kitchen. This prevents back drafting, avoids big swings in restaurant temperature, and eliminates negative air pressure.

In buildings, air comes in through three ways:

• Infiltration, which occurs as a result of the building structure and design. Air can enter via chimneys, joints, cracks and openings where parts of the building connect, including floors and walls, and around windows and pipes.
• Natural ventilation, which provides airflow through natural forces, such as opening doors and windows.
• Mechanical ventilation, which relies on fans and mechanical systems to move air.

It is important to note that increasing ventilation can increase energy costs. Therefore, it is recommended to pair ventilation with keeping known sources of air pollution out of the building.

HEPA filters

HEPA stands for high-efficiency particulate air. HEPA filters are a highly effective way to improve indoor air quality by removing dust, pollen, pet dander, mould, bacteria, and other airborne particles from the air. They are especially beneficial for people with allergies or chronic illnesses, as they can reduce indoor air pollution that may make it difficult for them to breathe.

It is important to note that HEPA filters restrict airflow, which can impact the performance of HVAC systems and strain the system. As a result, many HVAC systems require retrofitting to accommodate HEPA filters. Additionally, HEPA filters must be cleaned or replaced regularly to maintain their effectiveness.

When choosing a HEPA filter, it is important to consider the size of the room and the specific pollutants you want to filter out. Some HEPA filters are designed for specific purposes, such as filtering out pet dander and odours, or purifying the air in large spaces. It is also crucial to ensure that the HEPA filter is non-ozone-producing and non-ionizing, as recommended by the Environmental Protection Agency (EPA).

By combining a HEPA filter with a well-maintained HVAC system, individuals can significantly improve indoor air quality and reduce potential health risks associated with indoor air pollution.

Clean ductwork

Duct cleaning is a good idea if there is visible mould growth, or if the ducts are infested with pests or clogged with dust and debris. If you or someone in your household suffers from allergies or asthma, you may want to consider cleaning your ducts.

Ducts normally build up dust, pet hair, dirt, and pollen over time. They can also develop mould, or trap larger items like construction debris, vermin, or insects.

If your ducts are clogged, a simple inspection can tell you if dust, mould spores, pollen, pet dander, or other airborne materials are building up. These contaminants can contribute to health issues, especially for people with asthma, allergies, or other breathing problems.

Having trained specialists clean clogged ducts not only improves air quality but also helps to improve HVAC system efficiency and prevent breakdowns.

If you decide to clean your ducts yourself, be sure to wear a dust mask, as removing dust can trigger allergies. You will also need a shop vacuum with an extension hose, a dryer vent cleaning brush with an extender, an electric drill, and a replacement HVAC filter.

• Turn off the HVAC system at the thermostat or by shutting off the circuit breaker.
• Remove the supply vent grilles and the return vent grilles.
• Clean the supply grilles with warm water, mild detergent, and a soft brush in the kitchen sink.
• Prepare the cleaning brush by screwing the flexible nylon rods together to form a pole, then screwing the cleaning head onto the end of the rods.
• Examine the supply ducts by looking inside with a flashlight to see the duct's configuration.
• Dislodge the contaminants in the supply ducts by forcing the cleaning head into the duct and turning it with the drill.
• Clean the end of the supply vent by sucking up the contaminants with the shop vacuum.
• Prepare the vacuum hose by adding the extension hose to the shop vacuum and securing it with duct tape if needed.
• Clean the supply duct by turning on the shop vacuum and forcing the hose into the duct, then slowly drawing it back out while jostling it up and down.
• Dislodge the contaminants in the return duct by forcing the cleaning brush and rods into the duct and drawing it back slowly while rotating it with the drill.
• Clean the return duct by pushing the extended shop vacuum hose into the duct to vacuum out debris.
• Replace the grilles and vents once they are dry.
• Turn the HVAC system back on and let it run for about 20 minutes, then shut it off and check the filter.

If you decide to hire a professional to clean your ducts, expect to pay between $450 and $1,000, depending on the size of the system, the number of vents, the level of contamination, and the accessibility of the system.

Variable refrigerant flow systems

Variable refrigerant flow (VRF) systems are an HVAC technology invented by Daikin Industries in 1982. VRF systems are unique in that they rely on refrigerant alone, without a water-based cooling system, to provide a quick, responsive, and adaptive heating and cooling solution.

VRF systems use inverter compressors, which allow the compressor motor to run at variable speeds to save energy. They are also ductless, meaning that different rooms or spaces are equipped with a wall or ceiling-mounted indoor unit to distribute air. This allows users to make specific heating and cooling decisions based on the room or space.

VRF systems can be air or water-cooled. Air-cooled VRF systems are exposed to outside air and may be placed outdoors, while water-cooled systems are placed indoors and are cooled with water by a closed-type or circuit cooling tower or dry cooler.

VRF systems come in two formats: two-pipe and three-pipe systems. In a two-pipe heat pump system, all zones must be in either cooling or heating mode. In contrast, heat recovery systems can simultaneously heat certain zones while cooling others, usually through a three-pipe design.

VRF systems are ideal for customers looking for increased energy savings of up to 55% and room-to-room HVAC customization. They are also more energy-efficient than conventional HVAC systems, with an energy efficiency ratio (EER) of 15 to 20 and an integrated energy efficiency ratio (IEER) of 17 to 25.

Some advantages of VRF systems include increased energy efficiency, zoning capabilities, and individual temperature control. However, there are also some disadvantages, such as the need for a dedicated ventilation system to deliver outside air to various zones and the potential for refrigerant leakage due to long refrigerant lines and a large number of branch connections.

Frequently asked questions