Flat roof windows and light openings in flat roofs often have to fulfil several tasks. In addition to natural lighting of the interiors, they can also be used for ventilation or smoke extraction as part of a SHEV system. Especially in larger office, commercial and industrial buildings, light openings in flat roofs can be used to achieve natural lighting if the size of the room or the furnishings do not allow for sufficient window areas in the outer walls. But there are also interesting solutions for modern residential building architecture in terms of energy and appearance.
are numerous options for designing daylight openings in flat roofs. In addition to classic square rooflights, manufacturers offer many other solutions, such as round or triangular rooflights, glass pyramids, flat roof windows and continuous rooflights in a wide variety of shapes, from gable roofs to barrel roofs or free-forms.
planning sun protection: Measures must be taken, especially in the case of large continuous rooflights and glass roofs, to prevent the rooms below from overheating. This can be achieved by special sun protection glazing, external sun protection grilles or internal shading (not all systems are SHEV suitable here!). If the light opening also serves as an NRA (natural smoke extraction system), care must be taken to ensure that the shading control system is connected to the SHEV (smoke and heat extraction system) in the case of roller blinds or awnings that are freely stretched under the light opening, so that in the event of a fire, the shading is retracted in order to keep the opening free for the smoke extractor.
Fall-through protection: There are always (work) accidents in which people fall through closed or open flat roof openings. The light openings dealt with here are not generally suitable as accessible surfaces. Nevertheless, the workplace must be secured on a flat roof, for cleaning, renovation and maintenance work, but also during the construction phase itself.
According to DIN 4426 (Equipment for the maintenance of structural facilities - Safety requirements for workplaces and traffic routes - Planning and execution), a component is fall-through proof if a person who falls on it cannot fall through . However, this component is neither accessible nor accessible.
The planner can be held liable for damage and accidents caused by daylight elements that are not fall-through. Many manufacturers certify that their elements are fall-through resistant during installation (construction phase). However, further measures must be taken to ensure permanent fall-through protection in accordance with the test principles "GS BAU-18" (published by BG Bau).
There are three basic ways to ensure safety around roof openings on flat roofs: fall-through glazing, protective grilles or nets or securing options on the roof.
In addition to fall-through glazing, manufacturers offer various modules, most of which fulfil several functions, in order to upgrade daylight elements accordingly (also retroactively). Internal nets or grids offer fall-through protection when the elements are closed and fall-through protection when the elements are open, often even during the construction phase when they are mounted directly in the upstand . Thicker internal metal grilles can also meet the criteria for burglary protection according to DIN EN 1627 for resistance classes RC 2, RC 3 and RC 4.
External systems, such as a perforated aluminium sheet roofing or a fine steel mesh, are mounted directly on or at a distance above the glazing and thus offer fall-through protection, hail protection and sun protection.
Alternatively, the manufacturers offer special trailer systems for mounting on the upstands, into which a fall arrest and holding system of personal protective equipment (PPE) can be latched when working on the roof.
Shell opening - opening dimensions: Since most daylight openings in flat roofs are series products, the grid sizes of the manufacturers must be known for the planning of the shell construction. In the case of classic rooflight domes, the sizes of the individual manufacturers hardly differ, which means that the decision in favor of the manufacturer can be made even after the shell has been completed. However, there are differences in the assortment sizes and special shapes. It is therefore advisable to look through the manufacturers' assortment lists in advance to determine the exact opening sizes.
The sizes on the lists are always so-called nominal or order sizes and are the clear measurement on the lower edge of the upstand. To determine the required shell opening, the manufacturers provide information on permissible tolerances. In most cases, the shell dimensions correspond to the nominal size ± 1 cm. The light opening is usually about 18 cm smaller than the nominal size. At the individual manufacturers you can also find detailed tables about the individual elements, with the exact sizes for the incidence of light and ventilation area.
Renovation: Old or defective rooflights can usually be replaced without any problems, even across manufacturers. There are so-called renovation upstands that can be mounted on existing wreaths or upstands, which means that the roof waterproofing does not have to be damaged for replacement. If the insulation thickness on the roof is to be increased at a later date, special upstands are also offered to ensure the prescribed minimum connection height of the roof waterproofing. There are also complete solutions from various manufacturers for the renovation of old glass roofs and continuous rooflights.
Chimney sweeping work: Flat roof light openings can be used as an exit for chimney sweeping work. According to DIN 18160-5 (Flue systems part 5: Equipment for chimney sweeping work), the clear dimension of the access opening on a flat roof must be at least 60 x 80 cm.
System diversity: Daylight systems consist of a wide range of components that can be combined with each other. Rooflight domes, for example, can be opened with different drive types and mounted on different upstands. In addition, there is a huge selection of special solutions, e.g.:
exposure from the outside: According to the Model Building Code (MBO), roof windows, skylights and skylights must also be made of non-combustible building materials if a hard roof is prescribed for the roof. This does not apply to residential buildings or if there is no reason to fear a fire in the event of external fire exposure due to flying fires and radiant heat, or if precautions have been taken against this. Most manufacturers also offer products with plastic glazing, which are approved as hard roofing.
In addition, flat roof openings must be at least 1.25 m away from fire walls and from walls that are permissible in place of fire walls if these walls are not at least 30 cm above the roofing.
Further requirements can be found in the MBO § 32 Roofs or the respective state building code.
Fire protection of large roofs: The DIN 18234 series of standards deals with the fire protection of flat roofs of large dimensions, such as hall roofs for industrial buildings, sales and meeting places. The DIN 18234-3 and DIN 18234-4 standards deal with penetrations, connections and closures of roof surfaces. The protection objective of these standards is in particular the limitation of fire propagation into the roof structure or onto the surface of the roof in the event of fire stress on the underside. This is particularly relevant when using the roof opening as a smoke and heat extractor, as the aim is to prevent heat and smoke from flowing through the structure.
A distinction is made between
The following is a summary of the basic requirements from DIN 18234-3:
All terms and requirements are explained in more detail in DIN 18234-3. DIN 18234-4 is the directory for penetrations, connections and terminations that meet DIN 18234-3 and shows some connection examples. For all other penetrations, connections and terminations, suitability within the meaning of these standards must be tested and proven.
Smoke and heat exhaust ventilation systems: Most manufacturers of daylight systems for flat roofs offer smoke and heat exhaust ventilation systems (SHEV), consisting of natural smoke and heat exhaust ventilation devices (NSHEVs) - e.g. light domes or opening flaps in continuous rooflights, a SHEV control panel with emergency power supply, buttons for manual triggering and suitable supply air openings, e.g. supply air louvered fans for installation in the outer wall.
The opening mechanism of the NSHEV is operated either electronically, pneumatically or pyrotechnically, and they can also be equipped with wind deflectors that improve the flow coefficient and thus increase the aerodynamically effective smoke extraction area (= opening area). The measured and tested aerodynamically effective smoke extraction surfaces of the individual products are available from the respective manufacturers. The required aerodynamically effective smoke extraction area per fire compartment can be determined using DIN 18232-2 Table 3. In addition to the design bases and the design of the required aerodynamically effective smoke extraction surface, DIN 18232-2 also specifies rules for the installation of the NSHEVs and the condition of the supply air openings.
DIN EN 12101-2 specifies the requirements that an NSHEV must meet in order to be installed as part of a SHEV system. NSHEVs that meet these requirements bear a CE marking.
Rules for installation according to DIN 18232-2: DIN 18232-2 specifies rules for the installation of a natural smoke and heat exhaust ventilation device (NSHEV), the following is a
summary:
Stairwell smoke extraction: §35 of the MBO prescribes the possibility of smoke extraction from necessary stairwells. This is not a smoke extraction system according to DIN 18232-2 but smoke extraction to support the extinguishing work, which is regulated by the respective state building code (and any applicable special building regulations). In this case, the smoke extraction area is equal to the geometric opening area without a flow coefficient. The MBO requires an opening with a free cross-section ≥ 0.5 m² or a SHEV with a free cross-section ≥ 1 m² at the top point on each above-ground floor. This RWG must be able to be opened from the ground floor and from the top landing. In buildings of building class 5, this RWG is generally mandatory, but in buildings of building classes 4 and 5, further measures may be necessary to support the extinguishing work.
Heat extraction: Heat exhaust ventilation (VA) is necessary, for example, to reduce the fire resistance requirements of load-bearing or separating components, as the dissipated heat reduces the temperature of the components. According to DIN 18230-1, the heat exhaust factor for influencing the fire resistance is rated better for a heat recovery in the roof surface than for a heat recovery in the wall.
The model industrial building guideline also calls for the installation of heat exhaust surfaces. Minimum sizes and other requirements can be found in the tables of the guideline.
According to DIN 18230-1, the following openings can be counted as WA without verification:
In order to ensure that supply air flows in, additional ventilation openings ≥ 6 m² must be installed in the lower half of the wall, which must always be open or easily opened by the fire brigade.
Meltable surfaces: Rooflights and continuous rooflights are often used as heat extractors, as the thermoplastically melting plastic hoods also turn fixed roof openings into exhaust surfaces. This characteristic contradicts the requirement for hard roofing according to § 32 MBO. Most federal states have therefore set up additional regulations that allow soft roofing in partial areas, see also Usability of combustible translucent roofing.
The requirement for hard roofing according to § 32 para. 1 MBO does not apply to required smoke and heat exhaust surfaces of buildings in the area of application of the Model Industrial Construction Directive (MIndBauRL).
Some manufacturers also offer plastic sheets that meet both requirements, "hard roofing" according to DIN 4102-7 and "meltable area".
Usability of combustible translucent roofing: In addition, some federal states have published the following in the "List of Technical Building Regulations":
When applying the technical rules, it is important to note that DIN 4102-4 Section 8.7.1
:Combustible translucent roofing may be used if
Acceptance, testing and maintenance SHEV: A SHEV should generally be accepted jointly by the client and the contractor. Depending on the respective federal state, the specific intended use and the product, there are further requirements for acceptance as well as for tests before commissioning and after certain time intervals. The examination is carried out by state-recognised experts. Irrespective of this, the SHEV must be serviced regularly at certain prescribed intervals according to the manufacturer's instructions.
Construction site safety: Most construction site accidents occur due to falls from the roof. Openings in flat roofs pose an increased risk in the shell construction, which is why they must be secured by suitable construction parapets. As soon as an upstand is installed, an internal fall protection system can be installed on it, which also serves as fall-through protection for the lighting element after final assembly. However, this is not mandatory if the opening from the outside is sufficiently secured. Many manufacturers certify that their fully assembled elements are fall-through resistant during installation (construction phase). Further measures must be taken to ensure permanent fall-through protection in accordance with the test principles "GS BAU-18" (published by BG Bau). See also under Planning: Fall-through Protection
DIN 4102, Fire Behaviour of Building Materials and Components
DIN 4426, Equipment for the Maintenance of Structural Facilities - Safety Requirements for Workplaces and Traffic Routes - Planning and Execution
DIN 5034-6, Daylight indoors - Part 6: Simplified determination of appropriate dimensions of skylight openings in roof surfaces
DIN 18230-1, Structural fire protection in industrial buildings - Part 1: Mathematically required fire resistance period
DIN 18232-1, smoke and heat control - Part 1: Definitions, problem
DIN 18232-2, Smoke and heat control - Part 2: Natural smoke extraction systems (NRA); Design, Requirements and Installation
DIN 18234-3, Structural Fire Protection of Large Roofs, Fire Stress from Below, Part 3: Definitions, Requirements and Tests Penetrations, Connections and Closures of Roof Surfaces
DIN 18234-4, Structural Fire Protection of Large Roofs - Fire Exposure from Below - Part 4: List of Penetrations, Connections and Closures of Roof Surfaces That Meet the Requirements of DIN 18234-3 comply
withDIN EN 1627, Doors, windows, curtain walls, lattice elements and closures - Burglar resistance - Requirements and classification
DIN EN 1873, Prefabricated accessories for roofing - Plastic rooflights - Product specification and test methods
DIN EN 12101-2, Smoke and heat control - Part 2: Provisions for natural smoke and heat exhaust ventilation devices
Test Principles GS-BAU 18 published by BG-BAU
►FVTR Fachverband Tageslicht und Rauchschutz e.V.
Source: bauwion
