Rooms of modern airtight homes require a high flow of air for a healthy and fresh indoor environment.
Ventilation is the most effective way to get rid of contaminated air trapped indoors but how could we maintain an optimal airflow in a room? In short, by using both natural and mechanical ventilation in a smart and efficient way.
Every ventilation technique has some pros and cons and should be applied with much care and planning.
Why High Flow of Air is Required in a Room?
The air inside the rooms contains impurities and pollutants depending upon the type of city and place you are living in. Even if the room is closed and has no interaction with the outdoor environment, the air gets contaminated with moisture content during cooking, smoke, and some other indoor pollutants. The high flow of air in such rooms regulates the impurities and improves the air quality for a healthy and fresh environment of the room.
When there are a lot of people in a room like at school or work, the room will become hot and humid rapidly. In such situations, more air will be needed to flow through the room for a comfortable environment. Moreover, humans bear a cooler temperature if the air is flowing at higher speeds due to the evaporative cooling effect. This fact decreases the load of air conditioning and saves electricity cost.
A room with not enough flow of air is a perfect space for the growth of bacteria and fungi. Which would lead to several health issues including Asthma, Allergies and Rashes. Higher ventilation in the rooms prevents the growth of these microorganisms and keeps the room fresh and healthy all the time.
Some geographical locations are affected by radioactive radon gas formed during the decay of uranium and radiated by Earth. Radon is a colorless and odorless gas that can cause lung cancer. This is especially important for homes with basements.
Other than radon gas, there are up to 900 chemicals that have been found in the indoor air of the rooms that do not have an adequate flow of air. These chemicals in the air have a negative effect on human health. Stale air may also damage paints and other surfaces of furniture and cause health issues. Therefore, it is necessary to have a proper flow of air and ventilation for healthy and safe living.
How do I Increase the Airflow in a Room?
So, how do you increase airflow in a room?
Opening the doors and windows of the rooms is the simplest and quick way of getting fresh air where strong or enough wind is available. On the other hand, where strong wind is not available, exhaust fans and window mounted fans can do the trick. These fans increase the driving force for the wind to blow into the room and replace the stale air of the room with fresh and cool air from outside.
Rooms of tall buildings may have a chimney effect in which stale air gets hot and escapes from the top opening and fresh air enters the room from an opening near the floor level. Air conditioning and HVAC systems provide a variable required flow rate of air at specific places with an increased installation and running cost.
Natural Ways to Increase the Flow of Air in a Room
Natural methods are those methods of increasing the flow rate of air that runs entirely on their own without any type of mechanical aid. Natural methods have no running cost and negligible maintenance cost. Natural ventilations work best in the areas of cool night and breeze.
Natural ventilation saves 10%-30% of energy utilization in a building. Natural ventilation uses outside cool air and pressure difference to ventilate the house. The cool breeze from outside takes away the heat and stale air from inside the room and replaces it with fresh and cool air to effectively cool the space. The natural flow of air works best during summer nights.
The following are the two most common natural ways to increase the airflow in a room.
Opening the Doors and Windows
Doors and windows in opposite walls of the room result in cross-ventilation letting air enter through one side and exit through the other side. In this way, cross ventilation quickly replaces the stale air in the room with the fresh air from the outside.
However, opening the doors and windows in a polluted area may result in the accumulation of dust particles and other pollutants as well. In such cases, regular cleaning of the room becomes very critical to keep the air in a room fresh and clean.
The flow rate of air through open doors and windows depends on several factors. These factors may include wind speed, wind direction, the surrounding environment of the building, outside temperature, humidity and the size of windows. Higher wind speed at a location will allow a higher airflow rate through the room.
The Flow of Air due to the Stack Effect
Warm air produced in the rooms or buildings always goes upwards due to its low density. You can allow this warm air to escape from the top of the building through a constructed ventilator channel. Likewise, cool air should enter the room through the wall opening at the lower portion of the room or building. This type of natural ventilation is driven by density differences between warm and cool air and is also called buoyancy-driven ventilation.
Natural ventilation using chimneys or the Stack effect is the most effective ventilation technique for tall industrial buildings that produces a greater difference in temperature of air for its proper flow rate. A high flow of air is possible in stack effect when the path of air is long. You can further increase the flow of air by using smaller openings at the inlet of air and larger openings for the exit of air.
Furthermore, the wind speed is an irrelevant factor for the effectiveness of the buoyancy-driven ventilation that allows chimneys to work evenly throughout the year.
Mechanical Ways to Increase the Flow of Air in a Room
Mechanical methods are those methods in which air is forced to flow into or out of the room using a mechanical aid or electricity. Electricity is used to provide rotation to the blower or fans to create a movement of air inside or out of the room.
Here are some of the most effective mechanical ways to increase the airflow in a room.
Running a simple ceiling fan inside the room increases the flow rate of air by creating a pressure difference in the room. The increased flow rate of air leads to evaporative cooling by causing the evaporation of moisture content of the body. Running a fan dilutes the pollutants and other impurities in the room by spacing them evenly in the room but it does not improve the indoor air quality. Do not forget to run off the ceiling fan when no one is in the room because the high flow rate of air only cools down the people and not the places.
As warm air rises in the room, installing an exhaust fan at high levels of the room leads to the exit of hot air from the top. Along with an exhaust fan, the installation of box mounted window fans for cool air to enter the room will increase the flow rate of air in the room. In contrast to the ceiling fan, an exhaust fan improves indoor air quality by removing the stuffy air from the room.
An evaporative cooler works in the same way as a simple portable fan does but due to the evaporation of water inside it, it provides much colder air in the room. After running the evaporative cooler for an adequate amount of time air will be humid and leaving the door open for some time will be a good option to circulate the air in the room and to decrease the humidity level.
Air conditioning or HVAC systems have also been in use for regulating the air inside the room. The HVAC system provides cool or warm air to the room through the installed ducts in the room. Fresh air is supplied into the room and stuffy air exits the room through a return duct. For a better flow rate of air, you can use HVAC systems with 2 or more return ducts.
HVAC systems are expensive to install and have high running costs, but they would provide better control of airflow rate in a room. A specified flow rate of air would be provided to a specific place inside the building that offers better control of the flow of air.
Air is provided to the room using Air Handling Units that use different sets of filters. These filters often have an efficiency of 95%. Since air is being filtered before being provided to the room, therefore, HVAC systems can be installed in any location without the concern of outdoor air quality. HVAC systems are designed to remove moisture, odors, smoke, heat, dust and bacteria from the air.
Air Flow in a Room with No Windows
- An extractor fan is a large size fan that can be installed in the center of a room with no window. Extractor fans are mostly used in the kitchen where the air gets smoky and humid due to cooking. This air can damage the paint and other utensils if you do not remove it quickly. To remove smoke and oily particles from indoor places, the high flow rate of air is required and an extractor fan can do this job easily.
- In a room with a lot of furniture but no window, air cannot circulate at high flow rates even if the ceiling fan is running. Thus, to provide adequate ventilation and proper flow rate of air in rooms with no windows, furniture in the room should be as minimal as possible.
- Porous building materials are available in the form of bricks or air bricks that provide a sufficient flow rate of air inside the room. These porous materials will be of great benefit and provide a solution of airflow in a room with a lack of windows or no windows at all.
- Mechanical HVAC or air conditioning systems would provide a good solution for these rooms to provide airflow at any required rate.
Does a high flow of air reduce the risk of COVID-19 and other viruses at home and work?
Novel coronavirus spreads by large particles called droplets and small particles called aerosols, much like most viruses. These aerosol particles have the ability to remain suspended in the air for a longer period of time. This suspension may lead to a higher number of viral cases in the concerned buildings. Increasing the ventilation of indoor air and replacing the air with outdoor fresh air reduce the risk.
How much ventilation do I need in my home to improve indoor air quality?
Indoor Air Quality (IAQ) measures the quality of air inside rooms and other indoor places. More incoming air from outside improves the indoor air quality and less incoming air deteriorates the air quality. ASHRAE standards have a definite set of rules for indoor air quality. The rate at which indoor air is being replaced by outdoor air is called the air exchange rate. ASHRAE recommends 0.35 air change per hour for homes, and it must not be less than 15 cubic feet per min for a person. Different places require different air exchange rates for better indoor air quality. Therefore, we cannot determine an exact optimal level of ventilation for every room.