What are the different methods of Ventilation?
In the past, natural
ventilation in building was the most common way to let fresh air from outside into a home. Today, it's not usually the best way to get air into a room, especially in homes that have been properly air sealed to save
energy. Natural ventilation also frequently doesn't offer proper moisture
management.

Natural ventilation in buildings happens when air moves through cracks and small holes in a home without being controlled. These are the same cracks and holes you want to seal up to make your home more energy efficient. Opening
windows and
doors is another way to let in fresh air. Most people don't open their windows and doors as often as they used to, though, because they have central heating and
cooling. Because of this, air infiltration has become the main way that homes get
natural ventilation.
The rate of a home's natural ventilation is unpredictable and can't be controlled, so you can't count on it to keep the house evenly ventilated. How well a home
breathes naturally depends on how airtight it is, the temperature and wind outside, and other things. So, during mild weather, some homes may not have enough natural ventilation to get rid of pollutants. On the other hand, homes that are tightly sealed may not have enough natural ventilation most of the time, and homes that let in a lot of air may have high energy costs.
Spot ventilation can be used to make natural ventilation work better. But if both spot ventilation and natural ventilation don't meet the ventilation needs of your home, you should think about a whole-house ventilation plan.
Spot ventilation helps natural and whole-house ventilation work better by getting rid of indoor air pollutants and/or moisture at their source. Spot ventilation is when you use localized
exhaust fans, like the ones you find above stoves and in
bathrooms, to move air out of a room.
Experts says that instead of opening windows (natural ventilation in building), bathrooms and kitchens should have 50 or 20 cubic feet per minute of intermittent or continuous ventilation, and 100 or 25 cubic feet per minute, respectively.
Spot ventilation helps natural and whole-house ventilation work better by getting rid of indoor air pollutants and/or moisture at their source. Spot ventilation is when you use localized exhaust fans, like the ones you find above stoves and in bathrooms, to move air out of a room.
Experts says that instead of opening windows (natural ventilation), bathrooms and
kitchens should have 50 or 20 cubic feet per minute of intermittent or continuous ventilation, and 100 or 25 cubic feet per minute, respectively.
All of a home's fans, vents, and other ventilation equipment work together as a "
ventilation system" to move air from inside to outside without wasting energy. There are four types of ventilation systems:
exhaust, supply, balanced, and heat-recovery. The right ventilation system for a house depends on where it's located and what it needs.
In cold climates, exhaust ventilation systems are better because they are less likely to bring in moist air. On the other hand, supply ventilation systems are better at controlling moisture in warmer climates. Balanced ventilation systems work in both cold and warm climates, but they cost more to install. Heat-recovery systems switch the air inside with air from outside.
The EERE made the following information and diagrams to help people understand how these systems are different.
Ventilation system types

Exhaust Ventilation Systems
The way exhaust ventilation systems in UAE work is by making the
building less pressurized. By making the air pressure inside the house lower than the air pressure outside, they pull air out of the house. New air comes in through cracks in the building shell and passive vents.
Most exhaust ventilation in building are used in places where it is cold. In places where summers are hot and humid, depressurization can pull moist air into the
walls of buildings, where it can condense and cause damage.
exhaust ventilation installation is easy and doesn't cost much. Most of the time, an exhaust ventilation system is just one fan connected to a single exhaust point in the middle of the house.
exhaust ventilation installation is easy and doesn't cost much. Most of the time, an exhaust ventilation system is just one fan connected to a single exhaust point in the middle of the house.
Connecting the fan to ducts from several rooms is a better idea (especially rooms where pollutants tend to be generated, such as bathrooms). Instead of relying on leaks in the building
envelope, fresh air can be brought in through windows or walls with passive vents that can be changed. But passive vents may not work because they may need bigger pressure differences than what the ventilation fan creates to work.
- Spot ventilation exhaust fans in the bathroom that run all the time are the simplest form of an exhaust ventilation system.
- One worry about exhaust ventilation systems is that they may bring dirty air into the house along with fresh air. For example, besides drawing in fresh air from outside, they may also draw in:
- Radon and molds from a crawlspace. Dust from an attic. Fumes from an attached garage. Flue gases from a fireplace or water heater and furnace that use fossil fuels.
This can be especially dangerous when bath fans, range fans, and clothes dryers, which also lower the home's pressure while they work, are used with an exhaust ventilation system.
When compared to energy recovery ventilation systems, exhaust ventilation systems can also cause higher heating and cooling costs. This is because exhaust systems do not cool or remove moisture from the make-up air before it goes into the house.

Ventilation and Supply Systems
Pressurizing the building is how supply ventilation systems work. They use a fan to bring air from outside into the building, while air leaks out of the building through holes in the
shell, ducts for bath and range fans, and vents that were put there on purpose.
Supply ventilation installation is easy and doesn't cost much. are easy and inexpensive to set up, just like exhaust ventilation systems. A typical system has a
fan and ducts that bring fresh air into at least one, but preferably more, of the rooms that people spend the most time in (for example, bedrooms, living room, kitchen). In other rooms, this system could have window or wall vents that can be changed.
Supply ventilation systems in UAE let you control the air that comes into your home better than exhaust ventilation systems. By making the house pressurized, these systems stop pollutants from coming in from the outside and keep combustion gases from fireplaces and
appliances from coming back into the house. They also let the air that comes into the house be filtered to get rid of pollen and dust and/or dry out.
The best climates for supply ventilation systems are hot or mixed. Because they add pressure to the house, they could lead to problems with moisture in cold places.
In the winter, the supply ventilation system lets warm air from the inside of the building escape through random holes in the outside walls and
ceilings. If the air inside is humid enough, water may condense in the attic or on parts of the outside walls, which can lead to mold, mildew, and rot.
Like exhaust ventilation systems, supply ventilation systems don't change the air or get rid of moisture before it goes into the house. So, compared to energy recovery ventilation systems, they may cause heating and cooling costs to go up. Because air comes into the house from different places, it may be necessary to mix outdoor air with indoor air before delivering it to avoid cold air drafts in the winter. Another option is to use an in-line duct heater, but this will raise the cost of operation.
Balanced Systems for Ventilation
Balanced ventilation systems don't make or take away pressure from a house if they are built and put in the right way. Instead, they bring in and let out about the same amount of clean air from the outside and dirty air from the inside. Most of the time, a balanced ventilation system has two fans and two sets of ducts. It makes it easier to get fresh air everywhere by putting intake and exhaust vents in the right places.
A typical balanced ventilation system in UAE is made to bring fresh air to the rooms where people spend the most time, like bedrooms and living rooms. It also let’s air out of rooms like the
kitchen, bathroom, and laundry room where there is a lot of moisture and pollution.
Balanced ventilation systems, like supply and exhaust systems, don't cool or dry the air before it comes into the house.
Before letting outside air into the house, they do use filters to remove dust and pollen.
Also, like with supply ventilation systems, outdoor air may need to be mixed with indoor air before delivery to prevent cold air drafts in the winter. This could cause heating and cooling costs to go up.
Balanced ventilation systems work in all
climates. However, they are usually more expensive to install and run than supply or exhaust systems because they need two sets of ducts and fans.

Energy Recovery Systems
Most of the time, it costs more to install an energy recovery ventilation system than any other type of ventilation system in UAE. In general, keeping things simple is the key to a cheap installation. Many systems use ductwork that is already there to save money on installation.
Complex systems not only cost more to set up, but they also tend to be harder to maintain and use more
electricity. Most homes won't be able to afford the extra cost of trying to get all the energy out of the exhaust air. Also, these kinds of ventilation systems are not used that often yet. Only a small number of HVAC
contractors have the technical know-how and experience to put them in.
In general, you want to have a supply and return duct for each bedroom and each common living area. As much as possible, duct runs should be short and straight. To keep pressure drops in the system to a minimum and improve performance, you need a duct that is the right size. Insulate ducts in places that aren't heated and use duct mastic to seal all joints.
Also, energy recovery ventilation systems in UAE that are used in cold climates need to have devices that keep them from freezing or getting
frost on them. If the air coming in is very cold, frost can form on the heat exchanger, which can damage it. Frost also makes it harder for air to move through a room.
Energy recovery ventilation systems also need to be cleaned regularly to keep the ventilation rates and heat recovery from getting worse and to keep mold and bacteria from growing on the surfaces of the heat exchangers.