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Under the roof covering
Thermal insulation beneath the roof covering, the first protection zone of the house. This is where most of the radiant heat coming from the roof is stopped.
Technical content: Bogdan Ivănescu, graduate engineer, PhD candidate at the Technical University of Cluj-Napoca · updated on 16.10.2026
Heat, rejected upwards
The same sun, the same roof covering. Three build-ups, side by side.
Roof Pro + Silver or Bronze
The diffusion membrane on the roof boarding and the reflective shield between the counter-batten and the batten.
Radiation, reflected twice.
Silver or Bronze, beneath the roof covering, and Roof Pro, on the roof boarding, return most of the radiant heat upwards. Only part of it reaches the insulation.
The metal sheet remains dry on its underside.
The moisture that forms on the cold side of the insulation passes out through Roof Pro, and the air beneath Silver or Bronze carries it outside, at the ridge, before it reaches the metal sheet. Without condensation on the underside, the metal sheet does not rust from the inside.
Roof Pro only
The diffusion membrane with aluminium foil, without Silver or Bronze between the counter-batten and the batten.
Radiation, reflected once.
The radiant heat descends as far as Roof Pro, and the aluminium foil returns part of it upwards. More of it reaches the insulation than with the complete system.
The moisture comes closer to the metal sheet.
The air between the counter-battens carries the moisture towards the ridge, but nothing separates it from the underside of the metal sheet. On cold nights, part of it may condense on the metal sheet; most of the condensation drips back onto Roof Pro and drains towards the eaves.
A single conventional diffusion membrane
No aluminium foil, no shield between the battens and no warranty in years.
Radiation passes through the membrane.
The conventional membrane stops water and lets vapour escape, but radiant heat passes on into the roof boarding, the insulation and the habitable attic.
From year 3–4, the membrane begins to degrade.
The moisture reaches the underside of the metal sheet and condenses on it at night, and the metal sheet rusts from the inside. Most of the condensation drips back onto the membrane and drains towards the eaves. The conventional membrane carries no warranty and begins to degrade from year 3–4; once it has degraded, part of the water passes through it into the insulation.
Three zones, each with its own role
Two membranes work together: the diffusion membrane on the roof boarding and, optionally, a reflective shield between the battens. Minimum roof pitch: 15 degrees, so that water drains off.
Two functions
Roof Pro or Roof Optim
Both are diffusion membranes with integrated double-sided adhesive tapes and are installed in the same way. Roof Pro has aluminium foil and a reinforcing mesh, and therefore very high mechanical strength; it can also be installed without roof boarding. Roof Optim has an aluminised layer.
Silver or Bronze
An additional thermal shield. Together with the membrane on the roof boarding, they increase protection against the heat passing through the roof covering. Bronze is installed with the aluminium facing upwards; Silver has aluminium on both faces.
Installation steps
Nine steps, in order of execution: from the rafters to the roof covering.
Click on the central image to enlarge it.
Products for this application
Roof Pro
Diffusion membrane with aluminium foil, on the roof boarding.
See the product →
Roof Optim
Diffusion membrane with an aluminised layer, on the roof boarding.
See the product →
Reflectiva Silver
Thermal shield between the counter-batten and the batten, aluminium on both faces.
See the product →
Reflectiva Bronze
Thermal shield between the counter-batten and the batten, with the aluminium facing upwards.
See the product →Written warranty, on every membrane
Product warranty and service life, in accordance with the warranty certificates.
30 yearsRoof Pro
Service life of more than 50 years.
15 yearsRoof Optim
Service life of more than 30 years.
15 yearsSilver
On the exterior, between the batten and the counter-batten. Service life of more than 30 years.
10 yearsBronze
Service life of more than 20 years.
The quote for your roof
Select the products, enter the area and receive the material requirement and the quote by e-mail.