DASATOP®

Retrofit Vapour Control Layer

Advantages

Airtightness installed from the outside
Specifically developed for roof restoration
Humidity-variable MVTR
No additional airtight joints required at the rafters
High tear resistance due to fleece reinforcement

Areas of application

DASATOP® is an air-resistive barrier for installation over rafters and across sarking in roof renovation projects. Installed from the outside, DASATOP® protects structures from rain wetting during construction while cladding is removed.

Planning and construction guidelines

Areas of application

The pro clima DASATOP vapour control (alternate term: vapour check) membrane, which can be subjected to outdoor exposure, can be used on refurbishment projects as follows:

This membrane is optimised for installation into the spaces between the rafters and over the rafters
On structures that are open to diffusion on the outside

‘Sub-and-top’ solution with DASATOP

Roofing underlay membrane, e.g. pro clima SOLITEX MENTO 3000
Reinforcement rafter
Fibrous insulation material
Continuous linear contact ensured, e.g. with DASATOP FIX mounting strips
DASATOP
Service cavity, if applicable
Inner lining e.g. Tongue and Groove board

Possible combinations of insulation materials

Optimal protection for building structures can be achieved with the DASATOP system if the following conditions are met:

External roof insulation with fibrous insulation material
Roofing underlay membranes that are open to diffusion on the outside (e.g. the SOLITEX MENTO series), also over roof sheathing, and
Wood-fibre

A combination with foam insulation materials should only be used as a covering if: - Drying out of the structure to the outside is ensured, and - This combination is installed in the pitched roof area, but not on uppermost ceilings/floors underneath unheated attic spaces

In general, pro clima DASATOP cannot be used on structures that have diffusion-tight component layers on the outside.

4 weeks of outdoor exposure

pro clima DASATOP can be subjected to outdoor exposure for up to 4 weeks to protect the building structure. Please note that DASATOP does not provide sealing that is equivalent to an emergency roof. Moisture can enter at staples or other perforations (nails, screws etc.). Drainage of water across adjacent building structures must be ensured. Additional covering with tarpaulins is recommended for buildings that people are still living in or that are particularly worthy of protection (e.g. historical or listed buildings).

Use of fibrous insulation materials

Fibrous insulation materials are ideal. Moisture must be able to penetrate as far as the vapour control membrane in order for the humidity-variable properties of DASATOP to have an impact. Diffusion-open insulation materials ensure that this is the case and are recommended for this reason.

If blown-in insulation is used, DASATOP must be in contact (supported) across the entire area of the inner cladding.
DASATOP can also be combined with fleece-laminated foam insulation materials as an additional insulation covering (for greater than 50 mm thickness) if the structure is open to diffusion to the outside. However, this is only possible in the pitched roof area, but not on uppermost ceilings/floors underneath unheated attic spaces. WUFI software check recommended.

Installation under reinforcement beams:
If the depth of the rafters is to be increased, it is recommended to first install DASATOP and then fit the reinforcement rafter. In this way, the airtightness layer is positioned on the warmer side of the structure, which is favourable from a construction physics viewpoint.

Use possible on structures that are open to diffusion on the outside

Diffusion-open roofing underlay membranes (e.g. SOLITEX roofing membranes) protect the structure during the construction phase and provide the required windtightness. They can also be installed onto solid-wood sheathing. Permeable insulation panels made of wood-based products can be added to any arbitrary thickness above the rafters (eg. Gutex wood fibre boards).

Inner lining

In principle, all inner lining typically used in construction are permitted. Excluded are building structures with additional external roof insulation with foam insulation materials (slow diffusion behaviour). In this case, no diffusion-inhibiting layers such as OSB or multi-layer wooden panels may be positioned on the inside of the insulation so as to ensure reliable drying out.

Increased indoor humidity

The diffusion resistance of pro clima DASATOP has been designed to ensure that there is a reliable vapour-controlling effect in the case of typical indoor humidities, even in bathrooms and kitchens.

Quality assurance

In the case of membrane installation on the exterior, efficient quality assurance can be carried out during the course of construction by means of differential pressure testing with overpressure and artificial fog. As part of this testing, fog is generated inside the building using a fog machine. In this way, the airtightness of detail features can be checked and rectified on the exterior. The membranes must be mechanically secured to a sufficient extent beforehand. For this reason, adhesive taping and all joints are to be implemented with particular care.

Detailed construction planning – particularly of joints at the eaves and gable ends and the implementation of these joints on roof refurbishment projects – is particularly important.

Optimal drying conditions

Protection thanks to a low MVTR: If sub-and-top membranes are not in ideal contact with the rafters, convection tunnels may be formed.
They can compromise the protection provided, but often cannot be avoided in practice.
Accordingly, it is important in the context of protection against damage to structures that membranes are extremely open to diffusion so that they can quickly transport larger quantities of moisture to the outside.

The variable diffusion resistance of DASATOP has been chosen to be ideal for quick sub-and-top installation.