Construction technology includes more than a dozen engineering solutions related to construction. The comfort of residents depends entirely on how well and competently it is done. All the power of the elements - rain, wind, and hail - falls, first of all, on the roof, so its design should be very carefully thought out.
Special requirements for roof construction are imposed in regions with high humidity, frequent rain or fog. Exposure to moisture significantly reduces the service life of wooden structures and roofing pie, even despite treatment with special compounds and installation. However, it is quite possible to minimize the problem of dampness; installing a ventilated roof will help with this.
The design of a ventilated roof has been developed quite a long time ago, its high efficiency has been proven by many years of practice. The popularity of this technology is due to the following advantages:
- high degree of protection of all layers of the roofing cake from getting wet;
- no swelling of the roof covering;
- possibility of using organic;
- economical due to the possibility of installation on top of an old roof.
If a ventilated roof is built on top of an old structure, then the latter “comes back to life”: the wooden elements become dry again, moisture is removed from the materials of the roofing pie. As a result, the roof appears to be double, its resistance to adverse weather conditions increases, and the whole house becomes truly warm and cozy.
The design of a ventilated roof provides for air circulation:
- between layers of insulation and waterproofing;
- between waterproofing and roofing material;
- in the attic space (as part of the general ventilation of the house).
Thus, the entire roof structure is very well ventilated, due to which it is not only possible to get rid of excess moisture, but also maintain an optimal temperature regime. In this case, competent installation of the sheathing plays a decisive role.
The ventilated roof design has a number of varieties, which are related to the purpose of the building. For garages or outbuildings, use a non-insulated option, which consists of the following components:
- rafter system;
- lathing made of wooden slats;
- waterproofing;
- roofing covering.
Polyethylene film is used as waterproofing, which is attached to the rafter legs on slats.
For heated buildings Slab insulation and anti-condensation film are added to the roof structure, which protects wooden elements from condensing moisture. In general, the order of layers in such a roof is as follows:
- two layers of laminated film;
- non-woven material with high moisture absorption capacity;
- polypropylene fabric.
An important part of this type of roof is the vents located in the lower part of the eaves, as well as the ventilated ridge.
Project development procedure
During design work on the installation of a ventilated roof, it is necessary to provide for the following:
- Proper drainage. The roof structure must be such that water flows freely from its surface. This is especially true for flat roofs, where, due to improper installation, depressions often form in the covering in which water accumulates.
- Steam removal exclusively through the roof.
Contrary to traditional concepts, the walls of a house with a ventilated roof should not breathe. For this purpose, their design contains a reinforced vapor barrier layer.
Such roofs began to be built in the 80s of the last century. It was during this period that it became possible to install a heat insulator with ventilation ducts to remove excess moisture. Roofs of this type were most widespread during the construction of apartment buildings. The roof structure consists of the following layers:
- reinforced concrete floor slab, which is also the basis for the roofing pie;
- vapor barrier;
- a slab heat insulator made of mineral wool, inside of which there is the head of an aerator - a ventilation pipe (excess moisture is removed through this pipe);
- screed made of cement-sand mortar;
- waterproofing based on bituminous materials;
- polyurethane;
- a layer of polyurethane-based mastic;
- roofing material
The roof structure is complemented side parapets, which are separated from the roofing pie by bulk or sprayed material. In modern construction polyurethane foam plays this role, providing high insulation and sealing. It is also used to insulate the terminals of aerators.
The advantage of a flat roof is its low cost and the possibility of quick installation. Disadvantages: the need for frequent repairs and poor thermal insulation.
Pitched roofs
The design of this type of roof provides excellent air circulation, which penetrates into the under-roof space through the lower overhangs and exits through the ridge. In this way, it is possible to avoid the accumulation of dampness, which causes rotting or the appearance of fungus on the parts of the rafter system and roofing materials.
In some cases, a forced ventilation device is required. For this purpose, roof fans are installed on the roof.
As a covering Mostly lightweight materials with a wavy surface are used. A pitched roof can be either cold or insulated. The difference between these two options is the presence of an insulating layer. Mineral wool boards are usually used as an insulator.. Insulation with this material provides the following advantages:
- ease of installation;
- insulated coating;
- absence of cold “bridges”.
The list of roof installation operations is as follows:
- Preparing the base. At this stage, work is carried out to level the surface, eliminate cracks, chips and potholes. A screed made of cement-sand mortar or asphalting floor slabs is best suited for this purpose. The result should be a smooth surface with a slope of 2-3 degrees.
- Laying vapor barrier film and insulation. These layers must be laid in a continuous mass; cracks or breaks are not allowed.
- Installation of a waterproofing layer and cement-sand screed.
- Laying roofing. For flat roofs, fused rolled materials are used as a covering.
During installation, the bitumen included in the coating is melted using a gas burner, after which the coating sheet is firmly glued to the base. The rolls are laid in a direction transverse to the slope with an overlap of 80 - 100 mm. During installation, it is necessary to clearly mark the outlets of the ventilation ducts for their subsequent insulation.
The influence of condensation is especially strong in the off-season, when the ambient temperature drops. During this period, warm air, which contains moisture, rises from the living space and, in contact with the cold surface of the roof, condenses. A roof ventilation device prevents the negative consequences of the damaging effects of high humidity and helps create a comfortable microclimate not only in the under-roof space, but throughout the entire room.
How to arrange a ventilation outlet for metal tiles
To ensure that accumulated air along with moisture escapes from under the roof, it is necessary to provide a constant supply of fresh air from the street. Thanks to such a circulation device, the following tasks are performed:
- The surface of the metal tile is cooled. As a result of this, the snow does not melt on it, and ice does not form, and there will be no icicles on the eaves.
- During the hot season, the under-roof space and roof do not overheat.
Considering that steam has a high penetrating ability, a ventilation gap should be created between the roof and the insulation (usually 50 mm).
In order for the space to be ventilated naturally, ventilation outlets are used, consisting of a metal pipe, which is placed in a plastic casing and insulated with polyurethane. A deflector cap is installed at the top of the pipe to protect against precipitation from entering it. Structurally, the deflector is designed in such a way that it can enhance air draft.
A natural ventilation system will be effective only if the ventilation outlets are placed strictly in the prescribed order, taking into account the structural features of the roof and the direction of prevailing winds in the area. Otherwise, the opposite effect may occur when air is drawn into the room.
One of the main technological issues when installing a ventilation outlet is ensuring the tightness of its connection to the roof covering. This task can be achieved by using internal and external seals and a pass-through element for metal tiles. Various ventilation and sewer pipes, antenna penetrations and others can be used in this capacity. When ventilation outlets and fans are installed, roof penetrations are also used. They help achieve the required level of tightness on any type of roof.
How to install ventilation elements
To install penetrations through the roof covering, it is necessary:
- Mark and then cut a hole for the pipe in the metal tile using a template.
- Use self-tapping screws to secure the passage element in it, before applying sealant to it.
- An outlet (sewer, ventilation, etc.) is inserted into the passage element and, using a level, is set strictly vertically, followed by securing the outlet with self-tapping screws.
- The exhaust outlet is connected to the air duct located inside the house through a corrugated pipe. It is pulled through the vapor barrier, waterproofing and insulation. All passage points are sealed with adhesive tapes, a sealant for closing hydro- and vapor barriers, and sealant.
High-quality penetration can withstand vibration, precipitation pressure, and the effects of temperature changes. In most cases, the material for the manufacture of this element is silicone or rubber. They do not corrode, do not melt in the sun, fit tightly to the roof surface, serve as a reliable barrier against the ingress of moisture and debris and, thereby, help protect the rafter system from destruction.
Passage elements are selected in accordance with the type of roofing material and the diameter of the object being displayed on it.
When installing ventilation, special attention should be paid to arranging the passage through the roof structure of the shaft. A special device called a ventilation passage through the roof is installed in this place. There are several varieties of them, differing in the installation method. The choice of any of them depends on what type of ventilation pipes will be installed: sewer, smoke or antenna. Holes for pipes in metal tiles can also be processed in different ways.
In most cases, the installation of air ducts is carried out on reinforced concrete glasses, and they are fixed with nuts and anchor bolts. Such units can be used to transport air with a humidity of no more than 60% and a temperature of 80°C or less. The units are unified, their technical characteristics comply with the requirements of GOST-15150.
Metal roof ventilation
When the roof slope is 1:3 or even less, a ventilation pipe for metal tiles is installed. Its height in this case is 0.5 m, and the required quantity is determined based on the fact that for 60 m 2 of roof it is necessary to install one pipe.
Plastic ventilation pipes are most often used. They have an aesthetic appearance, long service life, meet sanitary and environmental requirements, and are easy to install. Due to their advantages, they are increasingly replacing traditional galvanized metal counterparts.
When the roof slopes are more than 6 meters long and the roof has a gentle slope, and ventilation pipes cannot be installed, ventilation connections are used. Their height relative to the roof must be no less than 400 mm.
For climatic zones where there is a possibility of heavy snowfall, the height of the ventilation pipe should be 650 mm. This helps prevent snow from covering it.
When building a new house, it is very important to follow the technology for installing the roof ventilation system. The desire to save on such an important element will cause serious problems in the near future. If you want your roof to last for decades without additional repairs, be sure to install roof ventilation.
Metal roof ventilation device
Ventilation of the under-roof space creates a favorable microclimate and affects the service life of wooden roof structures and metal tiles.
A well-designed ventilation system ensures a constant flow of air in and out, saving the home owner from many problems.
Lack of air movement causes increased humidity in the attic or attic space, mold on the walls and structural elements of the roof, their rotting and corrosion.
In the under-roof space, to one degree or another, there is always condensation and wet vapors formed due to the difference between the warm air in the house and the cold air outside, thermal insulation defects, and leaks in vapor barrier coatings.
Functional purpose
- removal of condensate and moisture from the under-roof space;
- ventilation of the roofing pie;
- removal of warm air when heating the tiles.
Ventilation of a metal tile roof ensures the constant removal of moisture-saturated air, keeping the elements of the rafter system and insulation (if any) dry.
Ventilation of the roofing cake removes moisture vapor from the insulation and preserves its thermal insulation properties. To do this, a ventilation gap is made between the layers, which ensures constant air circulation and drying of the insulation.
In summer, metal tiles get quite hot and to maintain a comfortable temperature, constant air exchange and removal of hot air from under the roof is necessary.
In winter, warm air under the roof causes the formation of ice and icicles, so its timely removal is no less important. Read how the roofing pie for metal tiles works.
Design methods
The organization of a ventilation system in a house begins at the design stage. Most often, continuous and spot ventilation is used.
Continuous system– provides air access through vent holes located under the eaves (covered with soffits) and its release through the ridge.
This is an effective scheme for simple gable roofs, the under-roof space of which has no obstacles to air circulation. When properly organized, a natural draft is created, like a stove draft. It provides continuous natural air flow.
It is important to ensure a balance between the volume of incoming and outgoing air. If the system malfunctions, moist air remains under the roof. This leads to negative consequences: mold, mildew, rust.
Spot ventilation (aerators)– used in addition to a continuous system, on roofs of complex shapes and in the presence of roof windows.
Metal or plastic aerators are installed on metal roofing in the form of a pipe with a cap (to protect against precipitation). To install them to metal tiles, pass-through elements are used to ensure a sealed exit of the pipe through the roofing.
The frequency of installation of aerators is calculated individually, depending on the complexity of the roof structure and the presence of roof windows.
Summarize
For simple gable roofs, continuous supply and exhaust ventilation is an ideal option that works almost without failure.
If the roof has a complex shape and there are skylights, many obstacles arise in the under-roof space for the free passage of air, and “stagnant” places appear. In this case, it is recommended to combine continuous ventilation with spot ventilation by installing aerators.
It is important to correctly design and install ventilation systems - the service life of the roof and the comfort of living in the building depend on their correct operation.
Ventilation outlet for metal tiles: installation instructions
Obviously, the roof over the house is built to last for decades, and a properly designed ventilation outlet for metal tiles will be the key to its high-quality and long-term functioning.
This can prevent the development of undesirable processes that can subsequently damage the materials of the roofing structure.
Why is it necessary to ventilate the roof?
Ventilation outlet for metal tiles
The correct ratio of temperature and air humidity in the under-roof space is the main task of the roof ventilation system, the presence of which will ensure the correct operation of the roof as a single complex.
It is known that warm air masses rise upward, carrying with them moisture in a vapor state. If the ventilation of metal tiles is not equipped, or it does not function correctly, moisture, having no way out, accumulates in a confined space and, reaching the dew point, condenses on the elements of the roofing structure.
In this regard, the following threats arise:
- Condensation settling on a wooden roof truss structure can cause the appearance of fungus and its rotting, which will subsequently lead to premature destruction.
- Condensation settled on the metal elements of the roof provokes corrosion, which over time leads to the loss of their load-bearing capacity and integrity.
- Moisture is well absorbed into brick or concrete elements of roofing structures, which can provoke an increase in their thermal conductivity and in the future lead to their destruction;
- Condensed moisture quickly saturates the roofing insulation, as a result of which it completely loses its properties, transforming from a heat insulator into a heat conductor. As a consequence, there is an increase in the costs of heating and air conditioning the building during the corresponding seasonal periods.
The problem described in the last paragraph is one of the key ones, and can appear in the shortest possible time.
How to arrange ventilation for a pitched roof - basic principles
Ventilation outlet installation diagram
In order to release the air masses accumulated in the under-roof space, and with them the moisture, it is necessary to ensure the supply of fresh street air.
Ventilation pipes for metal tiles are designed to perform this task. In the lower part of the metal tile roof, special vents are installed, through which cold street air enters the under-roof space, pushing out the accumulated moist air through exits in the ridge area of the metal tile roof.
This air circulation performs the following tasks:
- The accumulated water vapor that penetrates into the under-roof space from the residential part of the house is removed;
- The surface of the metal tile is cooled, which allows you to avoid melting snow and the formation of ice and icicles in the area of the roof eaves in winter;
- Overheating of the roof and under-roof space from solar radiation in the summer is excluded.
In addition to ventilation outlets, exits from the under-roof space are provided separately for ventilation ducts from the kitchen, bathroom and other rooms of the building. An outlet for ventilation of the sewer riser is also individually mounted.
Operating principle of continuous ventilation outlets
Ventilation outlets on the roof surface can be of two types:
- Point outputs– installed in the area of the roof ridge with a certain step from each other. In appearance they resemble a mushroom. They are also called roof aerators. Also, they can be equipped with forced fans.
- Continuous outputs– are mounted along the entire length of the ridge and are unnoticeable, since they are painted in the color of the metal tile and, unlike point exits, do not protrude above its surface.
To avoid direct rain, the exits are covered from above with decorative caps made of metal or durable plastic, and painted in the color of the metal tile.
How to properly install a ventilation outlet in a metal tile roof
To install the exits, it is necessary to make a hole in the metal tile sheet through which the ventilation duct will be brought out. To prevent rainwater from leaking in these places, it is necessary to use special blanks (pass-through elements), which are supplied in the color of the metal tile by suppliers of roofing materials and components.
Ventilation outlet installation method
The ventilation outlet for metal tiles is installed according to the following algorithm:
- Required number of outputs– at the rate of one per 60 sq. m. roof surface.
- The ventilation outlet must be located at a distance no lower than 60 cm from the ridge.
- If the roof structure is complex, with a large number of kinks and intersections, the number of output elements must be increased.
- The delivery set includes a template for marking the planned hole for the ventilation element.
- After the hole is made in the metal tile, it is necessary to paint over the end part of the metal to avoid the occurrence of a corrosion center.
- A rubber sealing ring is placed on the silicone, after which it is additionally attached to the roof with screws.
- After the sealant has dried, the pass-through element can be installed in its place.
It is also secured with screws. When installing a pass-through ventilation element, use only the specially designed screws included in the delivery package.
- On the under-roof side, it is necessary to ensure a reliable connection between the waterproofing and vapor barrier films.
To prevent moisture from getting into the sealant layer, it is necessary to additionally apply silicone sealant at the junctions of the waterproofing and vapor barrier to the ventilation pipe.
You should not save on arranging proper ventilation of the under-roof space. After all, its cost is negligible compared to the costs that may be required for restoration work covering a roof with metal tiles in the future if you do not protect your roof from condensation in time. High-quality components and responsible contractors who adhere to the correct technology for installing roof ventilation - all this together will significantly extend the life of your home.
Ventilation of a metal roof - installation of a ventilation outlet
Even the best roofing material, a perfectly assembled rafter system and strict adherence to all basic installation operations do not guarantee that the roof will reliably protect your home for a long time. The functionality of the roof largely depends on how the hydro- and vapor barrier layers work, as well as the ventilation system. Excellent ventilation systems are made by Vilpe, Aquasystem and Ridge Master.
Roof ventilation
Everyone knows why good ventilation is necessary, for example, in rooms. But not everyone knows that good roof ventilation is one of the main conditions for maintaining an optimal level of humidity inside the house and in the under-roof space.
Ventilated roofs last much longer due to the fact that the roofing material is not subject to the destructive effects of water, which accumulates in the form of condensation on any (wooden, brick or metal) surfaces. A constant flow of air from outside protects the attic from fumes resulting from temperature changes.
Ventilation protects wooden roof elements from rotting and metal tiles from corrosion, prevents the formation of ice and icicles on the eaves on the roof surface, and prevents the insulation from getting wet (that is, it helps to avoid heat loss). In summer, ventilated roofs do not overheat. From all of the above, we can conclude that the roof needs an efficient ventilation system.
Roofing pie and its structure
One of the elements of general roof ventilation is ventilation gaps in the “roofing pie”, which consists of:
- Vapor barrier layer;
- A layer (or several layers) of insulation;
- Waterproofing layer;
- Counter-lattices and battens;
- Roofing covering (metal tiles, etc.).
Ventilation system for insulated and non-insulated roofs
Gaps (voids) are arranged on both sides of the insulation (it should not come into contact with adjacent layers, there should be a free distance of about 5 cm between them and the insulation). They prevent steam, which has a high penetrating ability, from reaching the insulation and allow the roof to “breathe” (provide free access of air to the vents in the ridge).
Ventilation device in the under-roof space
Ventilation of a cold attic or attic involves the construction of a system of holes and gaps through which constant air exchange will take place. The most effective ventilation outlets will be in the eaves (under the roof overhang) and in the ridges. In this case, air circulates throughout the entire roof area under the roofing carpet from the eaves to the ridge.
Ridge and cornice vents can be point-shaped (round) or have an oblong shape. In skates, vents are often made in the form of a slot along the entire length of the skate. To ensure normal air circulation, the total area of the ventilation openings should be 0.3-0.5% of the entire roof area. Moreover, the area of the ventilation holes on the ridge and slopes should be 10-15 percent larger than the area of the eaves vents.
Elements of under-roof ventilation
Metal roofing includes ridge and eaves elements with ready-made ventilation holes, which are sold complete with the roofing.
Ventilation hoods are installed not only as openings in the ridge, but also as separate elements. Aerators are designed to remove fumes from the under-roof space. They are suitable for almost all types of roofs.
The number of these devices depends on the following factors:
- Purpose of the building and its design features.
- Roof configurations.
- Roof area.
- Roofing covering.
Point aerators usually have the shape of a mushroom and are installed on slopes, not far from the ridge. In addition to passive aerators, if necessary, ventilation turbines and deflectors are installed on the roof. These devices create forced draft, which significantly accelerates the movement of air in the under-roof space.
Installation of ventilation outlet in metal tiles
Natural ventilation of the under-roof space is ensured using ventilation outlets, which are metal pipes in a plastic casing. A deflector cap is installed on top of the aerator, enhancing traction and protecting the pipe from precipitation. The installation of this element of the system must be done with special care so as not to damage the tightness of the roof. Sequence of operations:
- Marking is made for the hole in the metal tile sheet.
- A hole is cut with metal scissors.
- The cut is painted over with a special protective paint using a brush or aerosol.
- Part of the “roofing pie” is carefully removed so that the passage element fits into the hole.
- A passage element is inserted into the hole, sealed with silicone sealant and secured with self-tapping screws.
- The ventilation outlet is installed and, using a building level, is installed strictly vertically. Fastened with self-tapping screws.
- All joints are glued with adhesive tape and sealed with sealant.
Carrying out installation work
If the slope has a slight slope, special ventilation pipes are installed, the height of which is at least 50 cm (above the roofing). Ventilation pipes are installed at the rate of one pipe per 60 square meters. m. of roofing. Nowadays, plastic pipes are increasingly being installed on metal tile roofs. They are durable, easy to install and look good.
A roof covered with metal tiles can easily last for half a century. And its service life directly depends on how efficiently the ventilation system operates. By providing the roof of your home with a constant flow of fresh air, you can breathe freely and forget about problems with your roof for several decades.
Metal roof ventilation device
Ventilation of a metal roof allows you to avoid many problems that arise due to the accumulation of condensation on the inside of the roof. Metal is a reliable material, but a roof made of it does not allow air to pass through, so ventilation for metal tiles becomes the only optimal solution. During construction, further arrangement and construction of ventilation outlets on the roof are taken into account.
Why is metal roof ventilation needed?
The main reason for the accumulation of moisture on metal tiles and a layer of thermal insulation material can be called temperature differences. During the off-season period, warm vapors from living areas, kitchens and bathrooms rise up to the roof. There they enter colder airspace, as a result of which the resulting condensation tends to settle on walls and windows.
As vapors accumulate inside the building without the necessary external outlet, excess moisture appears on the metal roof. A ventilated roof serves to prevent dampness, as well as eliminate drops of water and snow that are blown under the roof by the wind.
For metal roofing, high humidity is especially dangerous. This is a factor leading to the destruction of roofing parts and damage to the integrity of the roof. As a result, the following negative changes are observed:
- The insulation loses its insulating properties and does not perform its functions. If the layer is saturated with moisture by just a few percent, the material accumulates internal heat and conducts cold, despite complete drying.
- Wooden parts are subject to deformation, rafters and sheathing are gradually destroyed. If wooden structural elements have not been pre-treated with antiseptic substances, they are at risk of mold growth and rotting.
- The accumulation of moisture leads to the formation of additional load on the roof rafters in the form of ice and icicles, their partial and complete sagging.
The installation of a ventilated roof restores the circulation of air masses on the metal roofing and under it. The ventilation outlet for metal tiles provides an influx of cold air, normalizes the temperature, preventing the snow from melting. During the hot season, a ventilated roof saves the roof and the space underneath from overheating. For this purpose, builders leave free space between the roof and the insulating layer of thermal insulation. The gap size should be at least 5 cm.
What is a ventilation system?
Effective ventilation of a metal roof is achieved through air exchange. The passage of ventilation through a metal tile roof when installing ventilation outlets is mandatory if there is an exhaust hood in the house.
The ventilation outlet for metal tiles is a long plastic or metal pipe. The diameter of the device ranges from 30 to 105 mm, the maximum height is 50 cm. The higher the ventilation pipe, the stronger the draft.
The universal device is mounted at a short distance from the roof ridge, no more than half a meter. This provides hot air with free access to the street from the building. Only a small part of the pipe goes up, resistant to gusts of wind.
The pipe is produced with a protective reflector on the head and is most suitable as an air duct for large sheets of metal tiles. The sheets are stitched together and sealed during installation. The complete set consists of the following ventilation elements:
When planning the design of a ventilated roof, specialists take into account the surface area and slope angles. For a roof of about 50 square meters with a slope of up to thirty degrees, one ventilation outlet is sufficient. The slopes are steep and large and may require additional pipes.
Exits through metal tiles are divided into point exits, which are ventilation fungi, and continuous exits, which are placed along the entire ridge. They are painted the same color as the metal tiles, so they are practically invisible.
Types of ventilation for metal tiles
When building a cottage, channels are provided inside the brick walls to ensure a natural flow of fresh air into the building. This system can be supplemented with an aerator, although in most cases a special pipe connected to the roof is sufficient.
There are two types of forced roof ventilation and are carried out according to the following schemes:
- Roofing. Optimizes temperature and humidity in the roof gap, preventing the appearance of dampness. Installation of a ventilation outlet on the roof is carried out using a pipe with a plastic penetration and a deflector that reaches the rafters. A ventilated roof can structurally solve the problem of loss of thermal insulation and destruction of the wooden parts of the roof.
- Through. A more expensive type of installation work, which involves the arrangement of exits passing through the entire multi-layer “roofing pie” into the attic space. For this purpose, holes are drilled, and the tightness is maintained thanks to standard passage elements with a diameter of 110 mm. The parts ensure installation of pipes and fans on the roof and are equipped with a rubber seal on the inside of the flange. They repeat the profile of the roof and are securely attached to the metal tiles. For ventilation under the roof, a deflector is used - a low-pressure fan.
Such a necessary measure as installing ventilation on metal tiles does not cost more than one tenth of the construction costs, but allows you to save a lot of money by significantly extending the service life of materials. The device is easily mounted on any type of metal tile, allowing you to bring channels to the roof of the house.
Almost every person who builds a house should know what a ventilated roof is?
It consists of three main ventilation circuits:
- ventilation of the space, which is located between the waterproofing layer and the coating, and also covers almost all planes, despite the degree of complexity of the roofs;
- ventilation of the space directly under the roof, which is considered one of the elements of the home ventilation system;
- ventilation of the space located between the waterproofing layer and insulation, in which stagnant zones are absolutely excluded.
Ventilation design and installation
For many decades, with imperfect technologies and building materials, houses were built that breathed through brick, wood, cracks in windows, in doors, masonry, in cracks between layers of rolled materials - roofing felt, glassine, in which all three ventilation circuits were united.
As a result of these technologies, the house had constant drafts, increased heating costs and some restrictions on the finishing of the premises. Quite often dampness and fungus appeared in some places. Ventilation ducts in houses were installed only in kitchens and bathrooms.
Modern building materials for roofing were able to solve this issue at a high level.
For your attention! When designing your home, you should pay special attention to the ventilation system.
For those who want to independently examine the project, there are two basic rules for a warm roofer:
- Steam always rushes upward
- Water always flows down.
The consequences of these rules are as follows:
When installing a vapor barrier, there is little overlap of roofing materials on each other, on the load-bearing elements and walls of the structure, the joints are taped with a special tape;
When there is no indoor ventilation, sometimes even gluing cannot prevent moisture from penetrating into the insulation if the vapor pressure is high. Ventilation allows “steam to escape from the boiler.”
The walls of the house should not “breathe”, since moisture, which is retained in the outer layers of the walls, often leads to delamination when frozen and easily penetrates through the walls into the “roofing pie”.
Advice!You should pay attention to the ventilation of small rooms and spaces.
Installation of vapor barrier should be carried out closer to the interior of the house.
If errors occur during the installation of waterproofing, then it is necessary to dismantle the roof covering, correct the errors, and provide access from inside the house to the vapor barrier.
Roofing device
Roof ventilation prevents the formation of ice crust on the ridge and roof ledges.
The influx of fresh air provides a ventilated space, and in the summer, when the roof heats up, the air picks up moisture and removes it outside. For such a system to work well, it is necessary to carefully think through the sheathing on which the ventilated roof is applied.
If the rafter system has already been installed, then it is worth thinking about choosing a roof. If you are building premises such as a garage or warehouse that are not heated, then the ventilation in them will be natural and the service life of this building will be limited by the service life of the selected materials.
In order for the building to last for a long time, it is necessary to arrange forced ventilation and insulate the room.
An uninsulated roof consists of the following elements:
- rafters;
- lathing;
- roofing material;
- waterproofing films.
The waterproofing film is fixed to the rafters using slats. Even when the roofing covering wears out, it protects against moisture from entering the building and has a long service life.
This material will be indispensable, even if you are building a small country house covered with slate; this film will last more than 50 years.
In private homes, a special “” device is required.
In addition to insulation, a diffusion waterproofing film is applied for ventilation. This film does not allow moisture to pass into the under-roof structures and ensures the passage of steam through the smallest pores of the material.
It also reliably protects the structure from the wind, having excellent waterproofing properties.
Only when installing gaps between the heat-insulating structure, roofing and film, good ventilation is ensured by the use of diffusion film for waterproofing. Otherwise, it will not allow water vapor to pass through.
You can use anti-condensation film for waterproofing.
It will prevent the formation of condensation well and is used for constructing a ventilated roof when using any roofing covering.
The structure of this material consists of 4 layers:
- ultraviolet resistant polypropylene fabric;
- non-woven moisture-absorbing material;
- laminated film - 2 layers.
Anti-condensation film protects not only from the penetration of moisture into the room, but also from the accumulation of dust and the formation of soot.
In a ventilated roof, vents are left to achieve a good effect, and also holes and ventilated ridges are installed in the lower part of the eaves, which well connects the ventilated gaps of the roof with the atmosphere.
The ventilated roof structure consists of finishing material and roof insulation. The steam that leaves the room reaches the insulation, which, absorbing moisture, loses its thermal insulation qualities.
The moisture that has accumulated in the thermal insulation layer mainly penetrates back into the room and appears in the form of drops on the ceiling and walls.
And in the summer it heats up very quickly and the heat enters the room through the roof structure. To avoid this, this is why a ventilated roof is installed.
Today, the requirements for modern roofing materials are very stringent. They should protect the room from penetration of moisture into the layer, and if this happens, then facilitate the rapid removal of moisture to the outside.
Therefore, a ventilated roof must be well insulated.
Despite the hype around some roofing materials, the comfort and warmth in the house is influenced not so much by them as by competent installation of the roof. If the construction was carried out professionally, observing existing standards, then any coating will be a reliable barrier to nature’s surprises, be it cheap slate or expensive metal tiles, and the entire roofing structure will save heat in the house and eliminate excess moisture. But the presence of condensation and high humidity “hints” that not everything is going smoothly with your roof. Well, to be more specific: during installation, the roof ventilation was created incorrectly (if it was created at all!).
And there are several reasons: either the roof was laid by non-professionals, or vapor barrier or waterproofing films were applied incorrectly, or the ventilation system was created without taking into account the type of roofing. There is only one result: you will have to disassemble the roofing pie and reinstall it.
What layers should a roof ventilation system be made of?
Roof ventilation consists of three components, each with its own function:
- Ventilation between the roofing and the waterproofing layer. Its task is to remove condensation from the roof that forms on the back side of the coating.
- Ventilation between waterproofing and insulation. It is needed so that moisture that has entered the insulation from the air has the opportunity to leave the roof. If this layer is not created, the insulation can absorb water as a result of roof leaks or during the rainy season and cease to function as a heat insulator.
- Ventilation of the internal under-roof space. This layer is responsible for removing vapors from the premises and preventing them from settling as condensation on the inside of the roof.
In this roof, the ventilation of the under-roof space is not thought out, so there is a lot of condensation on the roof
What laws of physics should be taken into account when installing ventilation?
Steam and water will seep into the roofing pie from both sides. The ventilation system should either prevent this from happening, or, if it gets in, allow the moisture to evaporate. It should be remembered: the steam does not flow perpendicularly upward, but slightly deviating to the side. The water does not flow perpendicularly downwards, but also deviates slightly.
This deviation is not always taken into account when forming a roofing pie, and the following installation errors are made:
Ventilation of the under-roof space. Errors in ventilation installation will lead to destruction of the roof structure
Mistakes in using vapor barrier and waterproofing films
Even if all the necessary air gaps are created in the roofing pie, ventilation will not be able to ventilate all the moisture if the waterproofing or vapor barrier films were installed incorrectly. They are often confused due to their external similarity. But these films have different tasks, and, accordingly, a completely different structure.
Let's consider what problems will fall on the head of the owner who has confused the purpose of the insulating materials:
- If you laid a vapor barrier film instead of a waterproofing film. The vapor barrier film completely eliminates the ingress of moisture from both sides. If you lay it on top of the insulation, then the moisture that gets from the air into the heat-insulating material (and it will definitely get in, especially during seasons of high humidity!) will remain in it, because it will not find a way out. As a result, every year the insulation will become more and more moistened until it finally loses its properties completely, and the owners will be faced with high heat losses.
- If you laid a waterproofing film instead of a vapor barrier. Waterproofing films (also called diffusion membranes) have special properties: one side “breathes”, and the other is waterproof. They are laid under the roofing, turning the breathable side towards the heat-insulating layer. In this case, there should be a ventilation vent between the layers. Then the moisture from the insulation will partially escape through the air gap, and the rest will seep through the funnel-shaped holes of the film under the roof and evaporate. If water accidentally gets through the roofing (as a result of leaks, through cracks, etc.), it will settle on the film and will not be able to penetrate deeper. And in the same way as moisture from the insulation, it will go home.
If you correctly fix the waterproofing material on the ridge, the steam will not find a way out
When installing a waterproofing film, it is the other way around, i.e. on the “breathing side” of the insulation, water and moisture entering from the outside will easily enter the insulation through the funnels, and will no longer be able to get out. As a result, the entire design of the roofing pie loses its meaning.
Another option is to lay a waterproofing film instead of a vapor barrier film. If you place it with funnels inside the house, then all the steam will instantly seep into the insulation, if on the contrary, then the moisture from the insulation will return back into the under-roof space, although not much.
Errors in a ventilation system created without taking into account roofing material
Some owners, out of ignorance, create not as many ventilation layers in the pie as a certain roofing requires. For example, metal tiles and euro slate are afraid of condensation on the back side, so a ventilation gap must be provided between them and the waterproofing layer. Those. They fill not a solid sheathing, but a lumber one, leaving gaps for air to circulate. If water gets under the roof from the outside, then with the help of this layer of ventilation it will be able to evaporate through the ridge.
The grille paired with the counter-lattice will create an air gap sufficient for condensation to find its way out
At the same time, anti-condensation films are used as waterproofing, which do not release vapors from the insulation under the roof, thereby relieving the roofing of additional condensation. But here is the second point: where will the moisture go from the heat-insulating material if it is not released under the roof? To do this, create a second layer of ventilation, leaving an air “cushion” between the insulation and the anti-condensation film.
You cannot lay diffusion and superdiffusion membranes as waterproofing, because they are designed to allow steam to pass under the roof, and in such roofs this can lead to corrosion of the metal tiles.
Only a properly created ventilated roof will retain heat and remove excess moisture from the house.
In the roof pie, the waterproofing material is surrounded by a double ventilation gap
Soft tile roofs
And these roofs are not afraid of condensation, so they do not require a serious air gap between the coating and the waterproofing. A continuous sheathing of plywood, boards, etc. is installed under them. Wooden materials themselves allow air to pass through well, so natural ventilation will work in any case.
Creating an air gap between the waterproofing and insulation will depend on which film you choose:
- Anti-condensation films are not installed on soft roofs. Diffusion membranes are used here. But to prevent the funnels from becoming clogged with insulation particles, an air gap must be left.
- If you plan to lay a superdiffusion membrane, then it does not need an air gap. The level of moisture passage is high and allows you to do without a ventilation layer. Such a membrane is laid directly on the heat-insulating material.
In this cake, the waterproofing layer is created using a superdiffusion membrane. It does not require a ventilation gap, but lies directly on the insulation
Having created all the necessary ventilation gaps, it should be remembered that steam will tend upward and water downwards only when there is air movement. Don’t forget to make a ventilated underlayment and install aerators on the upper edge of the roof or on the ridge. Otherwise, the roof will not be properly ventilated.
Condensation formed on the elements of the roof structure can cause premature destruction. This problem is especially relevant during the heating season, when there is a significant difference between the temperature outside and inside the building. In this case, the insulation experiences a serious load, the range of values can reach tens of degrees, as a result of which drops of moisture settle on it, blocking the thermal insulation properties of the material.
The best way to resolve the issue is to install a house roof with ventilation. In winter, it will ensure effective thermal insulation, and in summer it will reduce discomfort due to heat, preventing the flow of heated air. The costs of arranging the roof will increase slightly, but already in the first years of its operation they are guaranteed to pay off.
Ventilated roof design
The main goal when designing a ventilated roof is the choice of building materials. Other important points will need to be taken into account: the number of gaps for air passage, the pitch of the lathing, the type of waterproofing film and other nuances. Thus, when using materials with polymers, the ventilation space must be larger than when installing natural roofing.
The main task of a ventilated roof is to ensure air circulation and prevent the formation of condensation. The design contains three circuits that ensure the movement of air flows in the following spaces:
- between waterproofing and roofing;
- directly under the roofing;
- between hydro- and thermal insulation.
By design, there are two main types of ventilated roofing:
- non-insulated, main scope of application – utility and industrial buildings;
- insulated - used at all facilities where people stay for a long time: housing, commercial and administrative buildings, and other buildings.
Main elements of a ventilated roof:
- rafter system;
- sheathing;
- waterproofing;
- insulation (not on all objects);
- roofing covering.
Advantages of a ventilated roof
An important feature of such roofs is the presence of vents and special gaps in the ridge through which air circulates. One of the options for ventilating a roofing pie is to use thermal insulation material with channels for air flow. It does not matter whether you are installing a copper roof, with metal tiles or bitumen, you will need to designate the exit areas of the ventilation ducts.
The use of a ventilated roof can significantly improve the thermal insulation properties of the roof with virtually no additional costs. There are many advantages to this design:
- the formation of rot, fungi and other microorganisms is practically excluded;
- the risk of swelling of the roofing cake is minimal;
- the coating’s resistance to most external factors increases: precipitation, extremely low or high temperatures, rotting and others.
Using a ventilated roof is one way to extend the life of the roof covering, avoid the formation of condensation and increase the energy efficiency of the structure. When developing a project, you will need to take into account many nuances, so you will have to take a responsible approach to choosing a company that can be entrusted with such work.