Modern building materials and technologies, such as plastic windows and sealed doors, reliably protect our homes from drafts and street noise, but they also have a side effect: they completely block natural ventilation. As a result, moisture, carbon dioxide, and harmful substances from finishing materials and furniture accumulate in the rooms, leading to stuffiness, condensation on windows, and, in the worst cases, mold and mildew on the walls.
A properly designed and installed ventilation system isn't a luxury, but a necessity for maintaining a healthy indoor climate in a private home. Hiring specialized companies is the right choice, but it comes with significant financial costs. If you're looking to save money and are willing to understand the process, creating a functional ventilation system yourself is entirely feasible. This article will help you understand the operating principles of different systems, perform basic calculations, and choose the optimal design for your home.
Natural ventilation: operating principle and installation details
This is the oldest and most energy-independent method of ventilation, based on simple physical laws: warm air is lighter than cold air and rises. In the classic design, vertical ventilation ducts lead from "dirty" rooms (kitchen, bathroom, boiler room) to the roof. Warm, exhaust air rises through them and exits, creating a vacuum that draws in fresh air through air intakes or leaks in the building envelope. For natural ventilation to be effective, the duct cross-section must be properly sized.
Typically, the main riser (from the bathroom) is 140x140 mm in diameter (built in brick), while the branches to the kitchen and bathroom are 100-130 mm in diameter. It's crucial that the exhaust pipe rises above the roof ridge, otherwise the wind will create a backdraft, blowing air back into the room. The brick channel walls should be at least one and a half bricks thick to prevent the air from cooling too quickly in winter.
The main advantage of a natural system is its complete silence and lack of operating costs. However, its operation is highly dependent on weather conditions: in warm, windless weather, the draft is virtually nonexistent, while in winter, on the contrary, it can be excessively strong, chilling the house. Furthermore, such a system does not allow for control of the supply air volume or heating during the cold season.
Forced and combined ventilation: when nature's power is not enough
To compensate for the shortcomings of a natural system, mechanical ventilation is used. Forced ventilation uses electric fans that reliably move a set volume of air, regardless of the season or wind strength. It is divided into two main types: centralized and localized. A centralized system is a single network of air ducts converging on a supply and exhaust unit, typically located in the attic or utility room. Such a unit can not only move air but also heat, filter, and, in advanced models, cool and humidify it. This is the most effective solution, but also the most expensive and difficult to install.
A local system is a simple and cost-effective option. It involves installing separate exhaust fans in the bathrooms and kitchen, while air intake is provided by either reliable ventilators or special wall or window air inlets. The latter are discreet devices built into the wall that allow for the regulation of incoming air and are sound- and heat-insulated. A combined system is a happy medium. It features forced exhaust (by fans in "dirty" areas) and natural air intake (through valves in "clean" rooms—the bedroom and living room). This option is the most popular for DIY installations, as it combines sufficient efficiency, reasonable cost, and relative ease of installation.
Features of ventilation in key rooms of the house
Different rooms in the house have different airflow needs, and this must be taken into account when designing the system.
Kitchen ventilation: combating odors and moisture
The kitchen is a major source of odors, moisture, and heat. Natural ventilation alone is almost always insufficient. A range hood over the stove is essential. It can operate in two modes: exhaust (extracts air directly into the ventilation duct) and recirculation (pulls air through carbon filters and returns it back into the room). The former mode is more effective but requires a separate ventilation duct. If one is not available, you can use recirculation mode or install a separate, powerful exhaust fan in a wall or window. It's important to remember that any range hood requires airflow; otherwise, a vacuum will develop in the room, and draft will drop sharply.
Ventilation in the bathroom and toilet: eliminating excess moisture
These rooms are characterized by extreme humidity, which is an ideal environment for mold growth. Natural air flow is usually limited (by a gap under the door or a special door grille), so forced ventilation is necessary. A wall-mounted axial fan is installed, which can be connected to a light switch (operates when the light is on) or have a separate switch. There are models with a timer that continues to run for a set time after you leave, or with a humidity sensor—they turn on automatically when the humidity level exceeds a preset threshold. This is very convenient and energy-efficient.
Basement ventilation: protection from dampness
A cold and often damp basement without ventilation is a guaranteed problem with mold and a musty odor that will permeate living spaces. The simplest solution is to create vents (holes) in the foundation plinth on opposite sides of the house and cover them with rodent screens. This will ensure natural air circulation. For large or warm basements (for example, a boiler room or workshop), this may not be enough. In this case, a supply and exhaust ventilation system is installed using two pipes. The supply pipe descends to the basement floor (30-50 cm above it), and the exhaust pipe extends to the ceiling. Both pipes are vented to the outside. The difference in elevation creates a draft, and air circulates. A fan can be installed in the exhaust pipe to enhance circulation during the warmer months.
Boiler room ventilation: combustion safety and efficiency
A room with a gas or solid fuel boiler requires a special approach. For efficient combustion and occupant safety, a constant and substantial supply of fresh air is essential. Standards require three air changes per hour. A separate supply duct leading directly to the boiler is most often installed, with a cross-section of at least 150-200 cm². The exhaust system must also be powerful. A combination system is often used here: natural exhaust is backed up by forced exhaust. Air ducts should be as straight and vertical as possible, without elbows, to avoid creating additional resistance.
Practical steps for creating your own ventilation system
Before you even get your tools in, you need to create at least a basic diagram. On the house plan, mark the locations of the air supply units (in living rooms) and exhaust points (in the kitchen, bathroom, toilet, and boiler room). Calculate the required air exchange rate. A simplified estimate can be based on a standard of 30 m³/hour per person or on the air exchange rate (1-2 times per hour for living rooms, 6-8 times per hour for the kitchen).
For air ducts, use plastic or galvanized pipes of round or rectangular cross-section. Assemble the system, starting with the fans, carefully sealing all connections. Ducts running through unheated attics must be insulated to prevent condensation. Install air intake valves in the walls or windows. After installation, check the draft on all exhaust grilles. Proper ventilation is the key to fresh air, the health of your family, and the longevity of your home.