Thermal insulation in the mountains

Insulation at altitude: a key challenge for energy performance

In Briançon, the highest city in France, winters are long and temperatures frequently drop below -20 °C. Under these conditions, effective thermal insulation is not a luxury — it is a necessity. At Wood & Roof, we specialise in the insulation of roofs and loft spaces in mountain climates. Our on-the-ground knowledge, gained across dozens of projects between Serre-Chevalier, Monêtier-les-Bains and the Guisane valley, allows us to recommend the most appropriate solutions for each building configuration.

A poorly insulated roof accounts for up to 30 % of a home's heat losses. In the mountains, this figure can be even higher due to wind exposure, temperature swings and the snow cover that loads the structure. We work on both new timber frame builds and the renovation of traditional chalets or converted barns.

Sarking: external roof insulation

Sarking is the most effective external insulation technique for pitched roofs. It involves laying rigid wood fibre boards directly on the roof deck before the roof covering is applied. This method offers several decisive advantages in mountain conditions: it eliminates thermal bridges at rafter level, preserves the usable floor area of the loft and protects the roof structure from temperature fluctuations.

We use high-density wood fibre boards (such as Steico or Pavatex), whose thermal resistance reaches levels compatible with the requirements of RT 2020 and BBC labels. The thickness is calculated according to the altitude and orientation of the building. A chalet facing due north at 1,800 metres does not require the same thickness as a town house in central Briançon. Every project is subject to a precise thermal calculation.

Wood fibre and cellulose insulation: high-performance bio-based materials

We favour bio-based insulating materials for their thermal performance, their phase-shift capacity and their low environmental impact. Wood fibre, in semi-rigid boards or loose form, provides excellent summer comfort thanks to its thermal mass — a valuable asset in the Hautes-Alpes where summer days in the valley can exceed 35 °C. Its phase-shift coefficient, exceeding 10 hours for a standard thickness, protects loft spaces from overheating far more effectively than conventional mineral wool products.

Blown cellulose insulation is particularly well suited to insulating cold loft spaces and cavities in timber frame walls. Made from recycled newsprint, it has a very favourable carbon footprint and an insulating performance comparable to the best products on the market. We carry out the installation with professional blowing machines that guarantee a uniform density and no settling over time — a critical point for maintaining thermal performance in the long term.

HPV roofing underlay and moisture management

In the mountains, moisture management is just as important as the insulation itself. We systematically install an HPV underlay (highly vapour-permeable) that allows the roof structure to breathe while providing watertight and windproof protection. This component is essential in the Briançonnais, where freeze-thaw cycles, penetration by windblown powder snow and winter condensation can damage timbers if ventilation is not correctly sized.

Thermal comfort, energy savings and long-term durability

A well-installed roof insulation directly transforms the comfort of your home: less heat loss in winter, less overheating in summer, lighter heating bills, and a roof structure better protected from thermal shocks. In the Briançonnais, where temperature swings are large, this is the investment that changes daily life the most. We provide a detailed free quote for every insulation project, with no administrative middle-man: we focus our craft on installation quality and the long-term durability of the work.