Over the last century or so, the design of building construction has undergone significant changes. The focus has shifted to energy–efficiency with multi-layered sealed doors and windows fitted with insulating material to avoid heat loss. Comfort on the levels of temperature and humidity has taken precedence over the fresh air ventilation requirements. Glass & steel building is a common part of urban landscape because of its aesthetics and visual appeal. Appropriate ventilation ensures that there is enough intake of fresh air inside the building to keep various kinds of respiratory ailments (Asthma, TB, Bronchitis, Sinus, Emphysema, COPD, etc.) and diseases away. Fresh air enters into our home in 4 different ways-
- Opened doors and windows
- Connecting points of building like joints, cracks and openings including walls and floors around windows and pipes.
- Mechanical systems in building that force air into and out of the structure.
- Spot ventilation including the use of exhaust fans in kitchens and bathrooms.
Why the need for a fresh air ventilation system in buildings?
With the progress in civilization and earning livelihood getting more organized, people spend more and more time inside buildings. As per an estimate, an average person spends up to 90% of their time inside. The number not only indicates sick, elderly and very young. It accounts for a majority of the population including both sleeping and waking hours. Indoor air quality can be 2-5 times more polluted than the outdoor air. Cleaning the indoor air becomes essential to maintain a healthy ambiance. Merely opening windows or taking a stroll is not enough to keep the air fresh and lively.
Although N95 masks have better efficiency and filter, the medical-grade masks should be reserved for only healthcare and frontline workers.
Poor Indoor ventilation can affect health and safety in many ways. Some of them are listed bellows-
- Airborne microbial spreads rapidly in a poorly ventilated space.
- Natural Contaminants like Mould, Fungus accumulates easily.
- In a poorly ventilated space, ineffective cleaning methods (vacuum cleaning) aggravate the problem of indoor air pollution.
- Too high or low moisture content in the air increases the risk of illness.
- Odours linger for a greater time in a closed space.
- Concentration of CO2 level keeps on increasing posing health hazards.
Treated Fresh Air Unit or Fresh Air handling Unit-
Making the provision for fresh air alone is not enough. Fresh air also needs to be treated before it enters our homes and offices for external pollutants (PM 2.5, dander, pollutants, chemical gases and other microbial.) Treated fresh air unit is also known as the fresh air handling unit. Unlike conventional Air Handling units which are used for recirculating the air in an enclosed space, TFA caters to fresh air flow using a combination of filters and condition it to some extent using an appropriate cooling system. TFA (Treated Fresh Air) has been gaining popularity in applications where the requirement is 100% fresh air without any recirculation of air or for feeding a number of AHU’s to fulfill the fresh air needs.
Two-stage Treated Fresh Air units offer a complete IAQ (Indoor Air Quality Solution) with additional features like heating, cooling, high-efficiency filtration, humidification, mixing and sound attenuation. TFA unit also provides heat recovery opportunities between incoming ambient air and exhaust air without any chance of cross-contamination. The heat exchanger can intake even kitchen and toilet exhaust for heat recovery that is not possible with traditional heat recovery wheels.
Mechanical Ventilation with Heat Recovery-
Modern houses are designed to keep pollutants and elements out. However, there is also the need for continuous intake of fresh air. The task becomes even more challenging with the airtight newly build homes that are constructed with double or even triple-glazed windows and superior insulation.
One of the feasible solutions is Mechanical Ventilation with Heat Recovery. An MVHR system provides an energy-efficient balance. The MVHR units can be fit in the house usually the loft or a utility room. Fresh air drawn from the atmosphere is filtered through the unit removing pollutants. Through a series of ducts, the clean air is dispersed around the house into living rooms and bedrooms via a ceiling valve. In the cleaning process, the stale, moist air is also extracted from wet areas like showers, bathrooms, kitchens and utility rooms. Moreover, the heat from the extracted air is transferred to the filtered incoming fresh air. The recovered heat can help in reducing energy costs and fuel bills.
Right amount of Fresh Air in your House-
It may seem repetitive but an open area with good ventilation ensures that there is a continuous supply of fresh air inside the living premises. Example, for an office, the ideal ventilation rate should be 20 CFM/person. CFM stands for Cubic Feet Minute. Well-ventilated space ensures that air is not stale which can be a breeding ground for harmful pollutants including some deadly microbial. Constant recirculation of air makes sure that pollutants do not remain at the same place for a long time. Ventilation is allotted least importance while making a building/offices/ residences. Air changes rate or air changes per hour are an important metrics while deciding on the ventilation level. The recommended air change rate per hour by ASHARE has been mentioned in the table below-
|Location||Air Changes per hour||Location||Air Changes per hour|
|Homes & Residences||1-2||Schools||5-6|
|Hotel Rooms||1-2||Sports Facilities||4-8|
|Retail Shops||2-3||Shopping Centres||6-10|
The formula to calculate minimum fresh air requirements have been mentioned below-
Method 1 – Air change rate
Quantity of fresh air required (L/s) = (Air change rate (changes per hour)*Room volume (m3)*1000)/3600
Note: 1000/3600 is required to bring m3/hour to L/s
Method 2- Known occupancy
Quantity of air (L/s) = Known occupancy rate*Rate/person (L/s)
Benefits of Fresh Ventilated Air-
- Reduce Absenteeism and Sick time: Poorly ventilation and air quality because of lack of fresh air is associated with sick building syndromes like eye and throat irritation, inflammation and difficulty in breathing. In the long term for offices, this results in reduced attendance of employees. The provision of fresh ventilated air improves the overall quality of air reducing absenteeism and sick time.
- Greater Comfort: Indoor air quality is greatly affected by the amount of fresh air coming in and out. It helps in maintaining the ambient temperature. People spend the majority of their times indoor. An environment with an ample amount of fresh air increases the comfort of inmates’ manifold.
- Reduces cross-contamination and spread of other contagious diseases: Fresh air circulation inside the building helps in mitigating the concentration of disease-causing pathogens including the deadly coronavirus. There is ample evidence to suggest that a poor ventilated space with limited fresh air coming in and out provides a breeding ground for disease-causing microbial(bacteria, viruses, mould, fungus, etc.).
- Reduces CO2 level boosting Immunity and Lungs: Constant circulation of fresh air helps in eliminating the build-up of CO2 level inside the buildings. A build-up of CO2 inside the buildings can affect the overall indoor air quality leading to reduce pulmonary function and lung damage in the long run. Fresh air intake increases the level of oxygen inside the building increasing overall vitality and freshness.