Ventilation of the under-roof space for warm and cold roofs. On the proper ventilation of the under-roof space The need for under-roof ventilation

The roof is one of the most important and critical parts of the building, which is affected by many adverse factors both outside and inside the building. If with various natural phenomena, such as rain, snow, hail and gusty winds, everything is obviously clear, then about internal impact on a roofing pie it is worth telling in more detail. Special attention in construction pitched roofs ventilation of the under-roof space should be given. It is the properly organized ventilation of the under-roof space in the roof structure that contributes to the long-term operation of the building and improves the microclimate in the house. Consider 2 main tasks of under-roof ventilation:

Removal of water and household vapors, condensate falling under the roof from the interior;
alignment temperature regime roof space.

These tasks underlie the construction of pitched roofs. To understand the definition of under-roof ventilation, let's first consider the methods of roof insulation, depending on their purpose. According to the type of insulation, roofs are divided into mansard and attic.

In the case of mansard roofs, the insulation is located in the body of the rafters (along the slopes of the roof), Fig. 1

Attic insulation

In the case of a cold attic space, the ceiling is insulated (horizontal insulation), Fig. 2

Attic floor insulation

It is also worth noting that there is also a variant with combined insulation. This option contains both attic and attic parts of the roof (Fig. 3)

A distinctive feature in the ventilation of the under-roof space of the attic and attic space is the following. In design attic insulation there is a ventilation gap between the main roofing and the insulation.

Ventilation mansard roof through the ventilation gap (Fig. 4)

Attic ventilation through dormer windows (free ventilation) (Fig. 5)

The size of the ventilation gap is determined by the height of the crate bar. The minimum recommended ventilation gap for pitched roofs when installing attics is 40 mm.

The main requirements for ventilation are reflected in SP 17.13330.2011 (“ROOFING” Updated version of SNiP II-26-76):

4.4 Roofs made of corrugated sheets, including profiled, metal sheets, piece materials (tiles, tiles) on insulated combined coatings should be provided as ventilated with the formation of a gap between the thermal insulation layer and the roof ( ventilation duct), which communicates with the outside air in the eaves, ridge and ridge sections, and along the thermal insulation made of fibrous materials - a wind-hydroprotective membrane.
In order to avoid the formation of condensate from the side of the cold attic on the surfaces of the above roofs, natural ventilation of the attic should be provided through openings in the roof (ridges, ridges, cornices, dormer windows, exhaust pipes, etc.), the total area of which is assumed to be at least 1/300 area of the horizontal projection of the roof.

4.5 The height of the ventilated ducts and the dimensions of the inlet and outlet ventilation openings of the duct depend on the slope, the area of the roof and the humidity of the inner layers of the roof.

Roof slope, hail (%)	Height of the ventilation duct for removing vaporous moisture, mm	The height of the ventilation duct for the removal of vaporous and building moisture, mm	Channel inlet size	Channel outlet size

5 - less than 25 (9 - less than 47)
25 – 45 (47 – 100)

Notes: The height of the ventilation duct is taken for a slope length of not more than 10 m; with a longer slope, the height of the channel is increased by 10% m, or the installation of exhaust devices (aeration pipes) is additionally provided. The minimum size of the channel inlets (at the eaves section) is 200 cm 2 /m. 3 The minimum size of the channel outlets (on the ridge) is 100 cm 2 / m

Thus, in order to ensure sufficient ventilation of the under-roof space, it is necessary to provide for unhindered air inlet in the eaves and air outlet in upper parts roofs, as well as in all "dead" zones and unventilated pockets. For air inlet through the eaves of the roof, either open air access is provided (Fig. 6) or air access through the filing of the roof overhangs. Air access can be carried out both through the perforated decorative lining of the cornice overhang, and through specially provided technological holes or gratings (Fig. 7.1, 7.2, 7.3).

Rice. 6

Fig.7.1, 7.2, 7.3

The air outlet must be carried out through special roofing elements. For example, to ensure ventilation of the ridge during the device soft roof ridge ventilation element RidgeMaster is used (Fig. 8)

To improve ventilation in the ridge area, depending on the type roofing use special deflectors, penetrations and ventilation outlets. They are placed as close as possible to the ridge, no further than 0.5 m from the axis of the ridge.

When installing soft roofs, a prerequisite is also the device of a sparse crate to form a single ventilation chamber (ventilation plane) over the entire surface of the roof, as well as slots in the valley crate to exclude air pockets.

On the hip slopes, as well as in front of the pipes, skylights and in front of direct connections, it is also recommended to install point ventilation elements for air release.

Neglecting ventilation elements during installation, as well as not realizing the scale of the consequences in the future, can give a very sad picture, up to a complete restructuring of the roof. The fact is that insufficient ventilation or its complete absence causes stagnation of air in the under-roof space and, as a result, a number of possible problems:

the formation and accumulation of condensate in the ventilation chamber, damage to the wooden structures of the roof by bioorganisms, reduction in service life and reduction in the bearing capacity of the roof up to its collapse;
roof leaks, the formation of mold and fungi in the interior;
overheating of the interior during the warm season; air conditioning costs;
melting snow on the roof in winter and the formation of ice in the eaves with the collapse of gutters and significant damage to the roof;
the most sad phenomenon may be the wetting of the insulation, its sliding down and subsidence, the formation of "cold bridges" and large gaps for the penetration of cold air masses; heating costs;

As an example, we can cite many photographs of objects that have suffered precisely from non-compliance with the technology and norms for roof ventilation.

Examples:

Rotting wooden structures

Rotting of OSB plywood (lack of ventilation in the ridge zone)

The formation of icicles in the attic room, the formation of mold

Formation of frost at negative ambient temperatures, collapse of gutters.

The durability and reliability of the roof is affected by a large number of various factors, including the material from which it is made, the quality of the fasteners, and much more. Great importance also has the organization of ventilation of the under-roof space. It is proper ventilation that protects the space under the roof from moisture, thereby preventing the roof from becoming unusable ahead of time.

Roof space needs proper ventilation

Why is such a system needed?

Regardless of what materials your roof is made of and how well it is made, condensation will inevitably form on the inside of it. This is due to exposure to low temperatures, rain, snow and other natural factors and leads first to the formation of drops, and then to others. negative consequences. As a result of constant humidity, fungus or mold can form under the roof, which will slowly but surely spoil the roofing materials.

In order to prevent this from happening, ventilation of the under-roof space is necessary. It is a complex system that must be installed at the planning stage of the roof. The main purpose of under-roof ventilation is to protect against condensate, and the secondary one is to remove vapors from the room. In addition, such ventilation can act as additional thermal insulation, which will prevent the roof from overcooling or overheating. All of this extends the life of your roof.

Roof ventilation also performs a number of important functions.

Removes steam that can seep into lofts or attics from living spaces, thereby reducing moisture levels in your attic or attic.
It stabilizes the temperature along the length of the slope, due to which ice and icicles on the eaves are less likely to form in winter.
Reduces the effect of direct sunlight on the roof. If the under-roof air exchange is organized correctly, then the roof will heat up much less: the interior will not heat up either. This way you can save on air conditioning in your home.

There are natural and forced under-roof ventilation, each of these options has its own characteristics.

Air flow under the roof

How to make under-roof ventilation of a natural type

With natural under-roof ventilation, air circulates under the roof due to temperature changes. For under roof ventilation naturally you need to do the following:

a small free space is designed between the lower layer of waterproofing and the upper layer of the roof;
mount a uniform roof frame from a counter-lattice and a batten between these two surfaces;
ensure complete freedom of passage of air masses under the roof: the ventilation gap for this must be continuous;
make upper and lower ventilation vents in the circuit: the first are made in the cornice overhang, the second - in the area of \u200b\u200bthe upper slope.

Natural ventilation works as follows: the air under the roof is heated under the influence of sunlight and rises to the vents in the ridge area, through which it exits. The air in the gap becomes rarefied, and colder streams penetrate through the cornice vents. Due to this, a constant movement of cooled air masses is formed, which prevents the formation of condensate.

It is worth remembering that in winter, the vents in the roof ridge can clog the fallen snow, due to which the natural ventilation will stop working.

To prevent this from happening, pipes can be installed in the under-roof space, the height of which must necessarily be greater than the height of the proposed snow cover.

The advantages of natural under-roof ventilation of a private house are the simplicity of its installation and the possibility of organizing almost any configuration on the roof.

Forced ventilation under roof type

Not every roof design allows for natural convective airflow. For example, in flat roofs make it impossible. Especially for such options, there is a scheme for forced ventilation of the under-roof space.

This option differs from natural ventilation in that an electric fan is built into the ridge vents. It pulls warm air out, thus creating a circulation of air masses. Instead, you can also install special deflectors that will enhance the air flow, as well as ventilation turbines.

Forced ventilation of the under-roof space has its pros and cons. The pluses include the fact that for efficient air outflow with the help of a fan, fewer ventilation holes are needed in the upper part of the roof. And the disadvantages include the increased fire hazard of such a scheme, as well as the consumption of electricity.

For the attic

It is somewhat more difficult to organize under-roof ventilation of a mansard roof than in a private house. The difficulty lies in the fact that the attic prevents free circulation of air under the roof, occupying all the space under the roof. Therefore, air ventilation is organized between the roofing and the waterproofing or heat-insulating layer.

For soft roof

Soft types include roofs made of bitumen-tile, as well as roll materials. All of these options have one big drawback - complete airtightness.

Because of this, condensation forms under a soft roof faster than under other types, which negatively affects the crate, rafters and insulation.

Only under-roof type ventilation for a soft roof in private or apartment buildings. There are several options for such structures.

Use of aerators on a soft roof

An aerator is a special technical device designed for forced ventilation. In order for air to penetrate under the soft roof, aerators are installed on its surface at a certain distance from each other. There are two main types of such mechanisms:

small - set to 60 square meters roofing;
large - installed on 100-120 square meters of roofing.

The distance between two adjacent aerators should not be more than 12 meters, and the devices themselves should be placed evenly. In addition, the aerator can be built into the general house ventilation system or have its own fan.

Aerator for forced ventilation

Ridge ventilation soft roof

Ridge under roof ventilation is more efficient than aerators and is better suited for large areas. The ridge element is a special design in the form of a corner, which is installed on the ridge beam. Features of the installation of such a system are as follows:

the lining carpet on the side of the roof ridge during installation must necessarily protrude from under the tiles by at least 15 cm;
the protruding edge of the ridge element must be bent onto the tiled floor;
the plastic part is covered with tiles, but in such a way that the perforated walls remain open;
a skate is installed on the bent edge.

Ventilation with two gaps

This is the easiest way to organize ventilation of the under-roof space of a soft roof. It consists in the fact that special ventilation gaps are made in the lower and upper parts of the roof, the size of which starts from 5 cm. The lower gap serves for the influx of fresh air, the upper one for heated exhaust.

Ventilation with valves

The roof valve is a special design that cuts directly into the roof of any type. Roof valves are good because they are equipped with a protective mesh that prevents insects and rodents from penetrating into the inter-roofing space.

Also, with the help of valves, gaps and ridges, forced and natural ventilation of the under-roofing roof type from corrugated board and other materials can be carried out.

Roof valve integrated directly into the roof

If you organize ventilation under the roof with your own hands, then a number of important points should be considered.

If you want the effect of the movement of air masses to be stronger, then you should use hydro and steam barriers placed under the crate. They are special meshes that allow air to pass freely, but do not allow moisture and steam to pass through.
To ensure under-roof ventilation, a simple pitched roof a small number of vents located in the upper and lower parts of the roof in the same number is sufficient.
If you install a fan for air circulation in a building that is located in an area with high humidity, then the fan must also be characterized by increased power.
Fans must be installed simultaneously with the construction of the roof.

As can be seen from the above, organizing under-roof ventilation with your own hands for a roof of any type is not so difficult, and such a design has a large number of positive effects.

Reliability, operational life of the roof, as well as its cost-effectiveness is determined by the constituent elements of the structure, whether it be layers of a roofing pie, a coating or a supporting structure. Any of the design errors or violation of technology is fraught with deformation of the roof and the entire structure.

One can only welcome the attention paid by the developers to the device of heat, waterproofing and wind protection. Unfortunately, at the same time, they quite often do not attach due importance to such important element as ventilation of the under-roof space.

It would seem that it is so necessary? At first glance, especially from the standpoint of a simple layman, nothing. Indeed, it is difficult to imagine that moisture can form under the roof of a dry, newly built or renovated house. In addition, there was a time when roof ventilation was carried out practically at the expense of. Yes and in suburban construction until recently, there was no particular need for this, since, unlike modern hermetic houses, air circulated freely through the gaps in the roofing pie and its walls.

What threatens the lack of under-roof ventilation

In accordance with the laws of physics, warm air rises up into the attic or attic and is concentrated at the very top of the structure - under the roof. Thus, on cold winter days, snow that has settled on warm areas of the roof melts. As a result, the following processes take place:

When the thermometer drops below zero, problems begin on the inside too - due to the difference between the outside and inside temperatures, the moisture contained in the air condenses on the cold surface. The resulting moisture flows into the roofing cake, reinforcing structures, as well as beam ceilings. Alternating cycles of "freeze-thaw" gradually destroy them, reduce the effectiveness of thermal insulation, create a favorable environment for the formation of fungal mold.

The lack of ventilation of the under-roof space of the metal tile causes corrosion of the roof. First of all, areas where the factory coating was damaged during installation or operation begin to corrode.

The summer period is also associated with negative phenomena, for example, overheating of the roof, which, together with UV radiation, reduces the operational life of the roof, and the use of the attic room becomes problematic.

The traditional use of a dormer for air ventilation is generally ineffective. As for the ventilation of the under-roof space of the attic, such a solution is generally not applicable here.

The consequences of insufficient ventilation can show up quite early after about 5-6 months in the form of unsightly streaks and stains that appear on the finish from the inside.

Attention!
As metal structures corrode and wooden structures rot, the question arises of premature repair or complete replacement of the roof.

Most Important Functions

Modern ventilation is organized on the basis of the following provisions:
- access of cold air should be from below, and it should come out from above;
- maximum efficiency is ensured by the movement of air in the entire under-roof space.
It is aimed at the following tasks:
- remove residual steam that penetrates into the under the roof from the living quarters located below;
- stabilize the temperature over the entire area of the roof, thanks to which it is possible to exclude such undesirable consequences as frost and icicles formed in the area of cornices and overhangs;
- prevents from the inside of the roof;
- reduces the impact of ultraviolet radiation on the roof covering, in other words, the temperature in the rooms decreases, thereby reducing the overall cost of air conditioning at home.
Device

With a cold roof

This is the simplest case for solving the problem, since it allows large volumes of air to move freely. Vents located under the cornices, under the ridge bar, in the gables allow air masses to circulate due to natural convection:
- cold air is drawn into the attic from the outside through the cornice vents;
- warm air rises from the ceiling of the dwelling up under the roof and exits through the ridge vents.
Of course, in this way it is impossible to completely level the temperature difference between the roof surface from the outside and the inside, however, usually it is not enough to form condensate from the inside of the attic.

As a rule, the number of vents located along the top and bottom of the slope of pitched roofs of a simple configuration is the same. The only condition under which normal circulation of the air flow is ensured is that the total area of the vents should be about 0.33% or ⅟300 of the area of \u200b\u200bthe slope.

For a warm roof

Ventilation is a little more difficult. In such a design, air cannot circulate freely, since it is almost entirely occupied by attic rooms.

Air circulation in the residential attic, located in the under-roof space, is provided by a convective flow directed from the eaves towards the ridge. In order for it to pass this path without hindrance, additional space is created in the roofing pie between the layers of heat and waterproofing, using a counter-lattice and a crate. The gap must be at least 5 cm high.

Then, in the space under the roof, a ventilated circuit is formed, that is, they provide air inflow, as well as its exit with vapors:
- inflow: cornice overhang along the bottom of the roof, further, attic windows (above them), valley or others where the contour is interrupted;
- exit: ridge, attic windows (under them), junctions, that is, where they need to be made on purpose.
Attention!
It is important to ensure the continuity of the circuit in order to exclude the formation of "stagnant zones", places of possible accumulation of condensate.

How to ensure air circulation and continuity of the ventilated circuit

The market for roofing materials offers builders special elements that increase the efficiency of the system. Some of them increase the intensity of the air flow, others form an inlet / outlet for it. They are called aerators or air elements.

Roof ventilation

EXCESSIVE MOISTURE IS THE MAIN ENEMY OF YOUR ROOF

The roof of any house needs to breathe. With properly equipped ventilation, the life of the roof is significantly increased. An important caveat must be made - we are talking about a classic attic, when an insulated living space is placed under the roof and the space of the house is used as efficiently as possible, and not a cold attic.

In almost any roof structure, humidity is always increased. This happens for two reasons:

Due to the temperature difference between indoors and outdoors (especially during the cold season), there is a "dew point" - the temperature at which the moisture in the air begins to condense.
Warm air, as you know, rises. We are accustomed to living in warmth, so in our house this warm air tends to escape through the roof. There it collides with cold air, resulting in condensation.

From increased humidity in the roof space suffer wooden structures roofs, insulation, and as a result, the entire roof as a whole. Wet insulation reduces its thermal insulation characteristics by several times, and wooden structures are subject to decay, mold and fungi, which significantly reduces the life of the roof and can adversely affect the health of the residents of the house.

Ventilation

At correct device roofing pie, the vapor barrier prevents the penetration of water vapor from the room, and the diffusion membrane closes the insulation from the outside, not letting water through from above and allowing water vapor to escape from the insulation to the outside.

The classic design of the combined attic

1. Wooden truss system. 2. TECHNONICOL vapor barrier film. 3. Stone wool slabs TECHNOLIGHT EXTRA. 4. TECHNONICOL superdiffusion optima membrane. 5. Counterbar for creating ventilation ducts. 6. Sparse crate. 7. Wooden flooring (OSB-3; FSF). 8. Lining carpet ANDEREP PROF. 9. Multilayer tile TECHNONICOL SHINGLAS. 10. Step crate for insulation.11. Attic filing

It is in order to divert these water vapor from the space between diffusion membrane and wooden deck from OSP-3 or FSF (see figure), secure the roof structure and insulation, ventilation of the under-roof space is needed. It is required to provide air access on the cornice overhangs and its exit on the ridge parts of the roof. And if the first does not present any difficulties, then it is not so easy to release air where it is necessary to ensure complete tightness of the roofing. It is for the solution of these issues that the elements of under-roof ventilation are used.

Ventilation

Under-roof ventilation allows cold air to enter from below and exit from above. At this moment, air movement occurs in the entire under-roof space.

Ventilation removes residual steam from the premises of the building, stabilizes the temperature over the entire roof area, preventing the formation of condensate on the inside of the roof and the appearance of ice, icicles, and on a sunny day reduces the temperature in the premises when the roofing is heated from the sun's rays.

Ventilation

MOLD CAN CAUSE BREATHING PROBLEMS

It is known where there is excessive moisture, mold appears very quickly, which is dangerous to human health due to the mycotoxins that it releases. Mold spores move freely through the air and enter the human body when breathing. Exposure to mold can cause breathing problems, allergies or asthma. Mucous membranes after exposure to mold easily become inflamed, which can later lead to sinusitis, bronchitis, and even pneumonia.

by the most the best way to prevent the growth of bacteria and mold in the roof, and subsequently throughout the house, is to keep the building structures dry and properly organized ventilation system.

No need to save on high-quality ventilation. Its cost relative to the cost of the entire roof is unlikely to take more than a few percent. But repairing a roof due to its incorrect or poor-quality device will cost much more.

For the correct ventilation device, everything must be correctly calculated and installed, otherwise improperly equipped under-roof ventilation or its complete absence will lead to damage by fungus and mold to the supporting structures of the building, starting from truss system.

REASONS (typical errors)

CONSEQUENCE (typical problems)

At first glance, it seems that it is difficult to understand the huge number of elements intended for under-roof ventilation, it is not clear what for. And do you even need to install them all? But it's not. Modern under-roof ventilation systems are so easy to install that anyone can handle them.

One of the optimal solutions for ventilation devices now is plastic under-roof ventilation by TECHNONICOL. It allows the roof to "breathe" freely.

TECHNONICOL Corporation for the installation of a ventilation under-roofing system has developed, having adapted to the climatic conditions of Russia, the following elements:

Solid ridge aerator;
Ventilation outlet;
Ventilation outlet insulated D125/160;
Aeroelement PILOT;
Aeroelement KTV;
Roofing valve SKAT;
Valve SKAT Monterrey;
Passing element SKAT roofing;
Pass-through element SKAT Monterrey;
Passing element;
Cap D110/D160;
Adapter;
Sealants for antennas and pipes universal D 10-70;
Sealants for antennas and pipes universal D 90-175;
Aeroelement KTV - alpha;
Base deflector.

Consider the elements of under-roof ventilation in more detail.

Solid ridge aerator

Used for ventilation roof structures and attic spaces, to remove excess moisture from the under-roof space and serves as the main element of ventilation. For the correct operation of the aerator, it is necessary to first organize the flow of air through the cornice overhang, as well as the channel through which the air will flow to the aerator and organize a cut in a solid base 5-8 cm wide at the installation site of the element.

The aerator is installed on the roof ridge of flexible tiles, fixed mechanically. It is covered with ridge-cornice tiles. Two or more elements are connected at the ends into a lock. The ventilated area of the under-roof space is 25 m2.

Ventilation outlet D110

designed for ventilation sewer system summer houses and to remove all odors and fumes generated during cooking. It is installed on the roof and connected directly to the sewer riser using branch pipes and couplings. Characteristics: D of an exit of 110 mm, H of a pipe of 500 mm.

Ventilation outlet D110

Ventilation outlet isolated, D125/160 (H 500 / H 700)

It is also used to provide ventilation of the sewer system, but is recommended for installation in houses with year-round living. The insulated ventilation outlet is installed on the roof and, using a system of branch pipes and couplings, is connected directly to the sewer riser, which ensures the removal of odors. The insulated ventilation outlet is made of innovative materials that are not subject to icing even during prolonged frosts. (characteristics: D pipes 125 mm, D pipes external 160 mm, H pipes 500 mm and 700 mm).

Ventilation outlet isolated, D125/160 (H 500 / H 700)

Aeroelement KTV

It is used to remove excess moisture from the under-roof space of roofs made of flexible tiles with a missing roof ridge or when ridge ventilation is not enough. The pressure drop created by the air element sets air flows in motion, thus facilitating the removal of moisture evaporating from the insulation from the under-roof space. The recommended installation location for the air element is 0.5–0.8 m from the roof ridge, while air flow is provided on the overhangs. One aerator provides ventilation of 10 m 2 of the roof, provided that the height of the ventilated under-roof space is 5 cm.

Consumption: 1 air element ~ per 10 m 2 . Size: D exit 110 mm.

Each of the elements has its own functionality in the under-roof ventilation device.

Fast installation. It is simple to calculate the required number of elements and it is easy to carry out their installation.
Reduces heating costs. The level of humidity in the room remains under control, which allows you to significantly save on heating
Long service life. The TECHNONICOL company provides a 15-year guarantee for under-roof ventilation elements, while the service life is more than 30 years.
Eco-friendly roofing. safe for humans and environment materials allow you to create a comfortable indoor climate
Large operating temperature range. Retains its properties at extremely low and high temperatures from -50 to +90°C.
Wide color palette. The ventilation system is available in red, brown, green, gray, blue and black, which allows you to match it to the color of the tiles and realize any bold ideas of the architect.

No modern house today can do without under-roof ventilation.

High-quality under-roof ventilation with the right device will ensure a long service life of the roof and the entire building as a whole and will significantly save on energy consumption.

The strength, reliability and durability of the roof is determined by many different components. And builders try to take into account all these components in order to prevent fatal mistakes.

But such a component as ventilation of the under-roof space, as practice shows, is sometimes given insufficient attention. Meanwhile, not only the service life of the building, but also the comfort for those who live in it, depends on how carefully the under-roof space is protected from moisture.

But, even understanding the importance of this element of home improvement, many non-specialists, deciding to build on their own, do not always know exactly what and how to ventilate.

But when moisture appears in a constructed building from nowhere, it may be too late to redo something. Therefore, it makes sense to consider specifically some of the features of this problem.

Why is roof ventilation necessary?

Some non-professionals mistakenly believe that the "cooler" brand of roofing, the louder the name of its manufacturer and the higher its price, the less it lets moisture through. But the reputation of any product, including building materials of the highest standard, cannot ignore the laws of nature.

No matter how good the roofing material that was laid on the roof is and how well it was laid, in low ambient temperatures, water condensation can form on the inside. Leaks may occur during strong winds or rain. It is also impossible to exclude the ingress of water into the under-roof space through the gaps in the holes in the places where the roof is attached to the roof sheathing.

If ventilation is not provided at all or is poorly arranged, the load-bearing rafters, attic structures made of bricks and the heat-insulating layer will be affected.

The negative impact of moisture begins with the formation of drops of condensate, then mold and fungus appear, which begin to corrode any material. As a result, if urgent measures are not taken, wooden, stone and metal constructions will steadily collapse, reducing the life of the entire building.

To avoid this, a well-thought-out ventilation system is needed, and it should be done at the planning stage of the roofing. At the same time, it should not only eliminate the possibility of condensation, but also help to remove vapors from the interior of the building, and also serve as a kind of heat-insulating layer that prevents both hypothermia of the under-roof space and its overheating as a result of intense exposure to sunlight.

Summing up all the options for such ventilation, we can distinguish two of its main types - natural and forced.

Back to index

Natural ventilation device

Natural ventilation involves the creation of conditions for the emergence of a convective (due to the natural temperature difference between heated and cooled air masses) flow. To do this, it is necessary to design a small under-roofing space between the lower waterproofing layer and the upper roof layer - the actual roofing material.

The gap between these surfaces is created by mounting a uniform roof frame from the battens and counter battens. The dimensions of the wooden blanks for this frame must be selected in such a way that a free space with a thickness of at least 5 cm is formed under the roof.

In addition, in order to avoid the occurrence of stagnant zones that are dead ends for the air flow (condensate can accumulate here), it is necessary to ensure complete freedom of air passage under the roof and the continuity of the ventilation gap (ventilated circuit). Only such a circuit will provide maximum ventilation.

ridge knot attic floor roofs with aerator and soft roofing.

However, a constant supply of fresh air and its circulation through a ventilated circuit is impossible without the creation of special ventilation openings (vents). It is necessary to provide at least two types of technological holes - lower (cornice) and upper (ridge). The first ones are made in the area of the cornice overhang or along the ridge of the roof, the second ones - in the area of \u200b\u200bthe upper junction of the roof slopes.

In accordance with the laws of air flow, the air under the roof is constantly heated and rises to the ridge vents, leaving through them. Colder air flows by gravity into the space thus rarefied from the street through the cornice vents. Thanks to this constant movement, condensate does not form on the roof and in the rooms under the roof (attic, attic).

Meanwhile, in winter, ridge vents can become clogged with fallen snow, due to which the convective ventilation of the under-roof space can be disrupted. To eliminate this danger, which primarily concerns buildings with slightly sloped roofs, special pipes can be installed. With their height, greater than the thickness of the expected snow cover, they guarantee continuous ventilation.

The great advantage of the natural type of ventilation is its very wide applicability in construction. It provides effective ventilation of the gap under the roof of almost any complexity of the roof configuration.

Back to index

Creating forced ventilation

The development of building technologies and new approaches in architecture, involving the construction of buildings with flat roofs, forced specialists to develop options for forced ventilation of the subroofing layer. As you might guess, in such roofs it is almost impossible to create a convective air flow based on the independent movement of air from the bottom up when heated.

Therefore, in structures with flat roofs, forced ventilation is often resorted to. This method is also used in cases where, for some reason, it turns out to be too difficult to make a sufficient number of vents intended for natural ventilation.

Forced air flow is provided by the inclusion of a roofing electric fan in the ventilation circuit. It is installed in the upper (ridge) outlet. When turned on, this device draws heated air out from under the roof layer.

It should be noted that this method has its advantages and disadvantages. In particular, due to the presence of a fan in the top outlet, there is no need for in large numbers ventilation holes. At the same time, this device requires a separate power supply to it, which creates certain risks in terms of fire safety.

Another option for forced air draft is the installation of special deflectors in the ventilated circuit, which, due to the section of their design, enhance the natural air flow, as well as ventilation turbines. At the same time, in their lower part, these devices pass through the lower waterproofing layer of the roof. Air is blown into the under-roof space from a warm attic or attic.