Good ventilation of the attic space is an essential design step. It is the ventilation system that allows you to regulate heat exchange in the attic, and, accordingly, in the premises of the house, since the roof during the summer period can heat up more than 100C °. In the cold season, ventilation prevents the accumulation of moisture and freezing of the rafters.
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In the off-season, moisture and condensation collects on the insulation structures of the attic, quickly deteriorating them and destroys them completely. As you can see, ventilation of the attic in a private house is important at any time of the year, regardless of whether this space is used as a living or technical room.
The need for ventilation in the attic
Rotting rafters due to high humidity
The ventilation system is created in order to maintain the required parameters of the air environment in the attic room.
These include air temperature and humidity, the speed of movement of air masses, and their gas composition.
The measure will allow:
- provide the required indoor climate;
- prevent the appearance of condensation that occurs due to a significant difference in temperature indoors and outdoors during the cold season;
- maintain a certain level of humidity and temperature;
- create a constant air exchange, which eliminates the appearance of mold and fungal spores on building structures.
The service life of a private residential building, its comfort largely depend on the device of the attic ventilation system. It must meet the requirements of building codes and regulations.
Ventilation of warm attics
If a warm attic is planned in a private house, then the roof should be covered with ventilated material. If you want to cover with shingles or sheet metal, you need to provide space for air circulation. To achieve such an effect is simple, it is enough to additionally install counter-rails on the rafters. Metallic materials require the use of a windscreen.
The slate coating does not require additional ventilation devices. After all, air can circulate through the hem and the ridge on the roof. Ventilation of a warm attic should be similar to ventilation of a room. Therefore, it is advisable to provide for the presence of windows. It is desirable that all aspects of the ventilation systems be provided for in the design scheme of the house.
It is recommended to think over the ventilation system of the attic even at the design stage of the house.
What is attic ventilation
In fact, the ventilation of the attic is an engineering system that provides free movement of air flows inside it. They come from outside through special devices such as dormers, ventilation grilles and openings.
The main functional purpose of the attic air exchange system is the constant supply of the required volume of fresh air and the removal of stagnant air.
If it is improperly designed, then the microclimate in the premises is disturbed. This entails damage to the rafter structure and its destruction.
In order for ventilation to work flawlessly, you must follow the rules:
- cold air should come from the bottom of the attic space, and exit from the top;
- air masses must move freely over the entire area of the room.
In the most problematic places of the roof, point ventilation is done if the angle of inclination of the slope is 450, for example, in the places where valleys and hips are installed. For this, aerators are used, mechanisms of forced induction of air movement - inertial turbines.
Cold attic ventilation device
In a cold attic, air flows freely through special openings, due to which natural ventilation occurs. The design features of the system are determined by the shape of the roof and the type of material used for the roof.
When installing ventilation ducts, the following conditions must be observed:
- the air flow should move freely over the surface of the ceiling, without rising to the ridge;
- ventilation ducts should be equipped with valves to regulate the intensity of the ventilation process.
If the roof is gable, then in the attic you can put skylights on opposite gables or arrange vents with ventilation grilles.
They must be covered with nets to protect other insects from mosquitoes. A horizontal air flow will be organized in the room.
With a hip shape, gaps should be provided on the eaves of the eaves, through which air will freely enter the attic room. For its withdrawal, holes should be made at the ridge.
If the angle of inclination of the roof is 450 or more, then the room is ventilated due to the difference between the outside and inside temperatures.
At small angles of inclination, the ventilation system can be reinforced with electric fans or inertial turbines.
Ventilation holes must be located at an equal distance from each other around the entire perimeter of the house. But the stitching of wooden overhangs must be made loose.
Otherwise, holes are drilled in the outer walls. The total area of the ventilation ducts should be 0.2% of the area of the house.
Ventilation can be omitted if ondulin or slate is used for the roof. Air moves freely between the waves of material.
Warm attic ventilation device
The space between the ceiling and the roof can be used as an additional area for permanent living.
It is recognized as residential if it meets the requirements for living quarters with sanitary and hygienic rules and regulations.
If an attic is provided, then the ventilation design of the attic should be carefully considered and the best option should be chosen.
Features of the system depending on the type of roof:
- galvanized metal sheet - creating a ventilated area by patching a counter-rail on the rafter structure;
- metal tile - it is necessary to lay a vapor barrier layer from a polymer film on the crate;
- slate, ondulin - free flow of cold air from the lower part of the roof and removal of warm air through waves of material.
In modern houses, special aerators are used to remove exhaust air from the ceiling of the attic. The devices prevent the formation of condensation and its penetration into the dwelling.
Ventilation arrangement schemes:
- installation on the roof of a pipe equipped with a deflector;
- the use of frontal ventilation grilles or nets;
- device of a heat-insulated ventilation duct through an opening located in the upper part of the roof or outer wall.
Why are many people afraid to insulate a cold attic
- The first myth - because of ventilation, the rooms of a private house are cooled. In fact, the heat is lost due to poor-quality thermal insulation of the walls and ceiling, and the ventilation of the cold attic has absolutely nothing to do with it.
- The second myth - it is necessary to ventilate the attic space only in the summer in order to save the living quarters of the house from stuffiness. This is fundamentally wrong, since it is in winter that moisture passing through the ceiling and accumulating in the cold attic will turn it into an “impenetrable forest” filled with icicles.
- The third myth is that the ventilation of a cold attic is already carried out through natural cracks in the construction of the gables. In fact, in order for the ventilation of the premises to be sufficient, air vents should be made, the size and quantity of which is strictly calculated.
Correctly organized ventilation of the attic in a private house allows you to preserve the roof structure for a long time, saves significant money on heating and air conditioning of residential premises, and also prevents the accumulation of snow and icing on the roof in the cold season.
The most common type of ventilation in attics is eaves and ridge ventilation. Convection air movement is created through holes along the entire perimeter of the eaves and exhaust holes, along the ridge of the structure. Despite the fact that the design of such a cold attic ventilation system seems very simple, it requires correct execution and accurate calculations.
Ventilation calculation
The air flow, in accordance with the standards, should bypass the attic room 2 times in 1 hour. In order for the ventilation of the attic to function normally, the ratio of the area of the room and the area of the holes should be adhered to - 1: 400.
The area of the cornice vents should be 12-15% less than the area of the ridge and pitched ones. The calculation of the elements of the ventilation system is carried out taking into account:
- attic area;
- type of material of the insulating layer;
- the volume of warm air that enters the attic from the living quarters.
It is not allowed to reduce or increase the area of holes, vents. If there are not enough of them, then the air will not flow in the required volume.
Otherwise, the necessary protection of the premises from the penetration of snow flakes and rain drops will not be provided.
Sequence of calculations:
- measuring the area of the attic;
- determination of the size of ventilation openings.
If the area of the attic room is significant, then several air vents can be arranged. The same applies to the dormer, ventilation window - instead of one, you can install 2 smaller ones.
The calculation of ventilation for a house with an attic is carried out taking into account its volume and the number of people in it at a time.
The norm is laid down in the SNiP "Heating, Ventilation and Air Conditioning", which regulate the issues of the system design, regardless of the type of roof. In the calculations, the air exchange rate is used.
General recommendations for arranging ventilation
A ventilation system installed in a cold attic will function correctly if the following conditions are met:
- ensuring the strength of the fastening of the ventilation grill, aerator;
- timely cleaning of airflows from contamination, dust and small debris at the same time ensuring their protection from icing;
- installation of dampers on aerators, exhaust pipes and ventilation grilles;
- the location of the holes at the upper joint of the roof close to the ridge;
- installation on soffits mounted on the eaves of the roof, aluminum or plastic nets;
- insulation of ventilation ducts in the attic and under the roof in order to prevent the formation of condensation;
- installation of ventilation ducts with an area of 400-500 cm2 / m2. This indicator corresponds to a hole height of 40-50 mm;
- preventing the insulation from getting wet by cleaning the dust blown by the wind into the ventilation holes, channels;
- ensuring the protection of the installation sites of the valley, the cornice from falling leaves, debris into them by installing special devices.
When installing ventilation elements, it is necessary to strive to ensure that they are strong and stable. This measure will allow to withstand sudden weather changes and strong winds.
If done correctly, then unforeseen situations with unpredictable consequences can be avoided.
The quality of the ventilation system is affected by:
- significant length of the roof covering, therefore, it must be strengthened by installing additional auxiliary structural elements;
- significant increase in the height of the holes - air exchange decreases due to the occurrence of turbulence in the air mass.
Creation of the required microclimate
Ventilation scheme
The need for ventilation in the attic is primarily due to the need to create a certain microclimate within the spaces they occupy. This means that if the roof heats up in the summer, it is necessary to make sure that the heat does not penetrate from the attic into the residential floors located below.
The simplest way to solve such a problem is the ventilation we considered above with simultaneous cooling of the stagnant air masses. On frosty winter days, the flow of cold air into the under-roof space, on the contrary, can be limited.
Note! The natural ventilation system of the attic must have a mechanism for blocking the inflow and outflow of air, that is, it must be regulated with the help of special dampers.
Attic ventilation methods
The best option for natural ventilation for a cold attic is to install air vents and openings on the cornice. They are interconnected by channels through which the air flow moves.
In a house with an attic, deflectors can be arranged that create forced mechanical traction. This measure will ensure the normal functioning of the system in all weather conditions, regardless of the season of the year.
The main purpose of these devices is to remove warm air vapors and excess moisture, which lead to the loss of insulation qualities of the insulation.
Ventilation of the attic directly depends on its features:
- the area of the room;
- roof shapes;
- type of roof;
- type of building materials.
For example, if ondulin or slate, metal tiles are used, then a ridge is arranged, which is a classic option. With a soft or ceramic roof, a special valve is used.
Ventilation window
The most common method of ventilation in the attic of a private house is to install a window. In addition to ensuring the movement of air, it is used to inspect the elements of the ventilation system and the chimney.
With a gable roof, the windows are placed on the pediment on both sides for better entry of cold air masses and the removal of stagnant ones.
General installation rules:
- location of windows at a distance of at least 1 m from each other;
- maintaining an equal distance between the windows and the cornice, the ends of the house, the ridge;
- the overall concept of the appearance of the house should be combined with the design of the window.
Dormer windows
As a rule, dormer windows are used as ventilation in the attic in private houses with medium-sized rooms.
Their minimum size should be 60 × 80 cm to prevent air stagnation in the room.
The wooden frame is attached to the rafters with racks, after which the roof sheathing is carried out. The glass unit is inserted into it last.
There should be no gaps at the junction of the roof and dormer window. It should not be placed close to the ridge and eaves.
Dormer windows are made in the form of a rectangle, triangle and semicircle. Windows are installed at a distance of one meter or more.
The lower mark should be at a height of no more than one meter from the floor level, and the upper mark at 1.9 m.
Ventilation vents
If it is not possible to install skylights, then regardless of the type of attic, a ventilation method is used by means of vents covered with a mesh.
They are located on the roof of the house to ensure the normal exchange of cold and warm air.
The main types of these elements:
- slotted - located on both sides of the cornices. The gap should be 2 cm wide;
- point - presented in the form of holes, the size of which in width or diameter is no more than 2.5 cm;
- ridge vents - used on roofs made of shingles. Their width should not exceed 5 cm. They are installed, stepping back one row from the ridge of the house.
Aerators
When installing ventilation in a cold attic, you can use aerators. The devices are made in the form of a pipe covered with a head, or a plate with holes.
Their installation is carried out on the roof slope in the area of the ridge. It is in this place that intensive air movement occurs due to the difference in temperature and atmospheric pressure.
Aerators do a great job:
- with condensation that appears with excessive humidity. This prevents the appearance of dampness in the attic;
- with stale air, preventing it from overheating;
- with ice and icicles that form in the winter season.
This prevents premature wear of the truss structure.
The choice of the type of fixture is determined by the type of roof of the house. For example, for bituminous pavements, ridge aerators are the best option. For manufacturing, plastic and galvanized metal, resistant to corrosion, are used.
