The wind under the roof: Why do we need under-roof ventilation and how to organize it properly?

One of the most important tasks in the individual construction – arrangement of properly working underlay ventilation. Many homeowners do not give proper importance and sometimes are unaware of its necessity. As a general rule, any pitched roof must be ventilated, and this issue is addressed in the design and construction of the house. It is important not only formal compliance with this condition, but also the correct calculation of ventilation to ensure maximum efficiency and longevity of the roof as a whole.

Why do you need under-roof ventilation?

The main purpose is to increase the longevity of the roof and maintain a comfortable microclimate in the living areas. It performs several important functions: it blows out from under the roof accumulated there warm relative to street air and water vapor rising from the living space.

Autumn

Summer

Winter

If this does not happen, the warm air heats the roof covering, which leads in winter to the formation of ice and icicles on the roof, and in summer during the heat – to overheat the roof and living space.

The air is ventilated in such a way that the insulation is constantly ventilated and stays dry. This folds its main ability to retain heat and eliminates the formation of condensation, moisture and mold in building structures.

In the absence of ventilation, the service life of insulation, roofing and supporting structures is reduced, and the rooms in the upper floor or attic becomes damp and cold.

Facts and figures: a 5% increase in the humidity of insulation, its ability to retain heat decreases by half.

How does the underlay ventilation

Movement of air under the roof is due to the natural circulation of air – convection warm air, compared to the cold, is lighter and goes upwards . This factor creates a bottom-up draft: from the bottom edge of the roof to the top from the eaves to the roof ridge .

In order for ventilation to work efficiently, you need to create the conditions for sufficient air flow under the roof along the eaves and prevent the accumulation of heated air at the top point of the roof, ie.e. let it out under the ridge. To do this along the eaves are made inflows, and in the upper part under the ridge – exhaust.

Insertion:

Elena Seregina, head of the technical department of Tegola, one of the world’s leading manufacturers of roofing, waterproofing and geosynthetics systems for industrial and civil construction:

“The indispensable companions of any living space are water vapour, which contains moisture that can turn into condensate dew. Through ventilation, heat and condensation accumulated in the underlay area, naturally derived from the structure of the roof, thereby prolonging the life of the structure as a whole. To create efficient circulation of air flow within the roof structure will need:

–

Provide a gap between the insulation and the base of the roof the height of the gap is determined depending on the slope and the length of the roof slopes and must be at least 5 cm

–

Arrange the inflow of air on the eaves and exhaust ports at the top of the roof

–

Ensure unobstructed flow of air through the entire underlay area.

“Cold” and “warm” roof

A dwelling house requires thermal insulation. The design of the roof pie depends on whether you plan to build a house with a cold attic or insulated attic. In a house with a cold attic insulation is placed directly on the attic floor above a cold floor can be laid , and in the case of the attic insulated its ceiling. In both cases, and insulation, and the underlay area attic or dwelling attic must be ventilated.

Scheme of the ventilation of the “cold attic”

In the first case, the whole space in the attic is ventilated, which somewhat simplifies the task. For example, to create horizontal draught through ventilation can be used attic windows t.n. “attic” .

Figures and facts: For attic ventilation, the total cross-sectional area of inlet and outlet openings should be at least 1/300 of the area of the attic floor.

Diagram of ventilation “living attic”

If there is a residential attic under the roof, then between the insulation and the base of the roof covering leave a ventilation gap. In the design of the house is important to correctly calculate its necessary height, which allows to create sufficient draft for efficient air exchange. In addition, the ventilation gap should not be interrupted. This means that in the way of the air flow must not be placed any transverse elements that prevent the flow of air from the eaves to the roof top.

Figures and facts: for a “living attic” the minimum height of the ventilation gap should be at least 5 cm. In this case the total cross-sectional area of inlets on the eaves should be – not less than 200cm²/m, and outlets on the ridge – not less than 100cm²/m

Elements of under-roof ventilation

AQUASYSTEM soffit panels

Air flow in the eaves of the roof can be performed in various ways. The most common are soffit linings, which combines decorative with functional. The most attractive and durable are made of metal – galvanized steel or aluminum with a polymer coating of different colors, copper. With these soffits can be decorated both horizontal and vertical surfaces eaves trim roofs, gazebos, terraces and facades .

Inset:

“For inlets it is important to ensure free access to air. Therefore, special attention should be paid to the materials used for filing eaves. It should not be deaf elements, preventing the free movement of air. For example, metal soffits AQUASYSTEM has a special perforation that prevents debris or insects from getting under the roof, but free pass air. Depending on the task you can use soffits with central or full perforation,

– adds Elena Seregina Tegola .

Scheme of a ventilating ridge

1 – timber 2 – base under the roof 3 – insulation

4 – protective grid 5 – protective strip

At the top of the slopes of the roof is most effective to arrange an outlet for air flow with a ventilated ridge – a kind of second “roofing”, built along the ridge and raised above the main roof. In this case, all the air rising up to the ridge, will be secured to the outside.

Soffit eaves filing

Roofing with ventilation aerators

Structurally complex roof shapes may require other additional ventilation devices such as aerators, rotary turbines, roof gutters or ventilators.

Roof ventilation – one of the most important functional elements of the house, the importance of which should not be forgotten. Effective ventilation allows the roof to create a comfortable living environment in the living room, guarantees the owner longevity of roof structures and energy savings.