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The four-layer reflective package
Additional thermal insulation for habitable attics: four reflective membranes installed beneath the rafters, for an additional R = 3.01 m²K/W.
Technical content: Bogdan Ivănescu, graduate engineer, PhD candidate at the Technical University of Cluj-Napoca · updated on 16.10.2026
Three zones, each with its own role
The four-layer variant is installed in the same position as the two-layer package, but the first phase receives two layers of Multistrat before Gold. The fourth layer, also Multistrat, is placed immediately before the finishing board. Together with the sealed air layer, the assembly adds R = 3.01 m²K/W to the insulation you already have between the rafters.
R (m²K/W), thermal resistance: the extent to which the layer or assembly resists the passage of heat; the higher it is, the better it insulates. What it means →R = 3.01 m²K/W is derived from INCD URBAN-INCERC test report no. 7039 / 18.10.2023. What it means →R = 3.01 m²K/W added
The thermal resistance of the membrane assembly, R = 3.01 m²K/W, is derived from INCD URBAN-INCERC test report no. 7039 / 18.10.2023. The value is added to what you already have between the rafters.
202 kWh per square metre, annually
The estimated annual saving is 202 kWh per square metre. The calculation is based on an uninsulated roof, under Romanian climatic conditions.
kWh/m²/year: the energy saved in one year per m², calculated relative to an uninsulated roof. What it means →How the required quantities are calculated
Measure the surface area to be insulated on the interior side. The two layers of Multistrat in the first phase are calculated on double the surface area, so a 30 m² roll covers 15 m² of habitable attic. Quantities are rounded to whole rolls.
If you are building or renovating the roof now
Roof Pro is installed over the rafters, beneath the battens. It adds a further 0.30 m²K/W, water protection and a radiant barrier at the top of the roof.
Installation steps
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Frequently asked questions
How does the four-layer variant differ from the two-layer variant?
The installation position is the same. The difference is that in the first phase two layers of Multistrat are installed before Gold, and the assembly reaches R = 3.01 m²K/W.
Why does a 30 m² roll of Multistrat cover only 15 m² in the first phase?
Because in the first phase Multistrat is installed in two layers, so the required quantity is calculated on double the surface area.
How do I measure the surface area?
Measure, on the interior side, the surface area you wish to insulate; quantities are rounded to whole rolls.