SLOPED EXTENSIVE HARPO SYSTEM FEATURES

The sloped extensive roof green system is considered as such when the roof on which work is to be done has a slope between 9° and 25°. It is possible to green a sloping roof with appropriate technical and design measures to avoid the sliding effect. Generally, low growing perennial plants are used, which, due to low maintenance, make management very easy while providing excellent performance and ecosystem benefits.

The Harpo verdepensile sloped extensive system adheres to the UNI 11235:2015 standard, ensuring and exceeding the minimum characteristics for both all individual elements and system performance. The main characteristics of the system are as follows:

• Versatile and lightweight: usually the total thickness of the system varies from 16 to 24 cm. The weight at maximum retention is low. Usually the thickness of the substrate ranges from 10 to 15 cm. The weight at maximum retention of the lower thickness system starts from 140 kg/sqm.
• Aesthetic value: perennial, evergreen plants are used in these systems; those resistant to frost and drought of limited height should be chosen, allowing for aesthetically pleasing effects, or the natural lawn.
• Management costs: maintenance is very low, in two or three interventions per year, mainly to remove weeds and replace some deadfall for perennials and one or two interventions for natural lawn. Maintenance safety devices should always be provided.
• Irrigation: irrigation is mainly for emergencies.
• Implementation costs: if interventions remain within the indicated slopes, system costs are slightly higher than an installation on a flat roof. The vegetation cost is in function of the solution chosen.
• Thermal resistance: the system contributes to energy savings with a thermal resistance that varies depending on water content but is not less than 1.63 (m2 * K)/W, with substrate thickness 12 cm, according to the NRC report for the BAS system.
• Runoff coefficient: variable depending on the substrate thickness, and the slope of the pitch as indicated in the relevant UNI 11235 standard.

It should be kept in mind that a sloped roof obviously needs different technical arrangements than a flat roof. The most important factors to consider are: the main focus goes to system containment at the edge of the roof, restraint from slippage of the critical system interface, and substrate erosion on very high inclinations.

For these reasons, it is always advisable to conduct the necessary technical checks. Below are two of the aspects that should be scrupulously evaluated:

The check, study and definition of appropriate and suitable solutions for the containment of the system along the pitch and in the eave zone. In this regard, Harpo verdepensile proposes, as an alternative to reinforced concrete or wooden curbs, drainage containment profiles of the PPDo PBD type, combined with appropriate thrust brackets. The perimeter edge profile will be much “lighter” and will allow the designer to study a perimeter eave line that is aesthetically less impactful and avoids out-of-scale ledges

The check, study and definition of eventual eave-breaker lines (size, position spacing to be provided by the design engineer) that will have to contain the thrust of the planned system stratigraphy and thus act as a support for the plant substrate retaining panels.

Therefore, please check the information and indications regarding the proposed solutions and products with our technicians to identify the correct stratigraphy for your specific case.