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The reflective package for habitable attics
Additional thermal insulation for habitable attics: Reflectiva Gold and Reflectiva Multistrat, with the sealed air layer between them, over the insulation you already have between the rafters.
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
Gold is fixed beneath the rafters once the insulation between them has been installed, and Multistrat is placed immediately before the plasterboard or timber panelling. Together with the sealed air between them, the two membranes form a thermal insulation section that makes the existing insulation more effective. They occupy only 1.5 cm and take the place of the interior vapour barrier membrane.
R = 2.09 m²K/W, measured
The Gold, 6 cm air and Multistrat assembly was measured on a Lambda-Meter EP500e, at 10 °C and 15 K: λ = 0.0358 W/mK over 7.5 cm. The package adds this thermal resistance regardless of the insulation you already have.
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 →λ (W/mK), thermal conductivity: how readily the material conducts heat; the lower it is, the better the material insulates. What it means →Only 1.5 cm
Together, the two membranes occupy 1.5 cm: Gold is 10 mm thick and Multistrat 5 mm.
You no longer need another membrane on the interior side
The interior reflective membranes also act as a vapour barrier, so the build-up must allow vapour to escape towards the exterior. If you have OSB or other layers with high diffusion resistance, the configuration is analysed before you select the system.
Emissivity 0.05
The surfaces reflect 95–97% of thermal radiation.
Emissivity: an emissivity of 0.05 means that the aluminium face radiates only 5% of the heat that a common surface would radiate, so it does not lose heat through radiation. The lower it is, the better. What it means →Approximately 176 kWh per m² per year
This is what you save with this package alone, without other insulation, compared with an uninsulated roof, under Romanian climatic conditions. Nevertheless, we do not recommend installation without other insulation: in a habitable attic, the package is combined with a minimum of 15 cm of insulation between the rafters.
kWh/m²/year: the energy saved in one year per m², calculated relative to an uninsulated roof. What it means →The space between the membranes serves two purposes
The building services are routed between the profiles or battens, while the insulation remains continuous and hermetically sealed. The zone becomes a thermos that preserves the indoor climate and temperature of the house.
It complements, it does not replace
The package is designed for habitable attics with less than 35 cm of insulation between the rafters, in order to complement what is already in place.
Installation steps
Click on the central image to enlarge it.
Products for this application
Warranty
- ✓Reflectiva Gold: 50-year warranty, service life of at least 50 years
- ✓Reflectiva Multistrat: 50-year warranty, service life of at least 50 years
Frequently asked questions
How much does the package add to the insulation between the rafters?
A thermal resistance of 2.09 m²K/W, measured on the Gold, 6 cm air and Multistrat assembly. With 10–15 cm of Wolle P1500 + P800 between the rafters, Gold and Multistrat form the System 10 Basic package: the Basic 10 variant – R = 5.08 m²·K/W (equivalent to 19 cm of conventional insulation with λ 0.038), the Basic 15 variant – R = 6.40 m²·K/W (24 cm).
Do I still need a vapour barrier on the interior side?
No. Gold and Multistrat also function as a vapour barrier. If the build-up includes OSB or other layers with high diffusion resistance, request an analysis before selecting the system.
Do the Gold strips overlap?
No. Lay them edge to edge and seal the joints with Power Tape.
How is Gold fixed to the rafters?
With 14–16 mm staples or 1.5 cm wood screws.
Can I install the package without any other insulation?
We do not recommend it. Each type of insulation has its own role in the system; in a habitable attic, the package is combined with a minimum of 15 cm of insulation between the rafters.