Breathable materials

Monomur Thermopierre by Xella, the only construction system officially approved for the air permeability of housing

Committed for several years to an ecological approach, Xella, the world's leading manufacturer of cellular concrete, has just obtained approval for the air permeability of housing, under Annex VII of RT 2005. Xella thus becomes the first manufacturer of structural materials approved by the Ministry of Ecology, Energy, Sustainable Development and the Sea (ref. RT2005-A7-008) for its Thermopierre single-wall. Thanks to this recognition, project owners benefit, for their projects built with the Thermopierre single-wall (blocks 25 to 50 cm thick), from an air permeability value equal to the reference value of RT 2005, i.e.:

• 0,8 m3/(h.m²) for individual houses,
• 1,2 m3/(h.m²) for collective housing.

An integral part of the thermal study of constructions, This air permeability value is a "key" to obtaining the HPE* and THPE** labels, as well as the BBC-Effinergie label. To strictly comply with the conditions of the approval, Xella has defined a precise Quality Plan, committing it reciprocally with the project owner.

If Xella already intervened well upstream of construction sites, in particular with the training of masons, the cellular concrete manufacturer now wishes strengthen its partnerships with professionals in order to support them in their efforts and in their quality guarantees.

Air permeability of housing: for a healthier and more economical home

A determining factor in the energy performance of housing, building insulation has a direct impact on heating consumption. According to RT 2005 reports, walls alone are responsible for 20% of heat loss in a new individual house and parasitic air inlets between 5 and 10%.To avoid this waste and ensure the effective operation of air management systems, proper sealing of the building envelope is essential. Furthermore, a building that is not airtight leads to a deterioration in air quality and occupant comfort, as well as an increased risk of condensation.



To ensure the quality of a building's envelope, RT 2005 sets specific objectives. Without on-site measurements being taken when the building is finished, default permeability values are taken (in m3 per hour and per m² of surface area): 1,3 m3/(h.m²) for individual houses and 1,7 m3/(h.m²) for collective housing.

Thermopierre single-wall: the only construction system approved for air permeability in housing

The world's leading manufacturer of cellular concrete, Xella offers construction materials with high thermal performance, high inertia and enabling the construction of buildings with excellent airtightness. The Thermopierre single-wall system is the only construction system which, from 25 cm thick, allows performance to be achieved beyond the requirements of RT 2005..

The Thermopierre single-wall is therefore particularly recommended for ensuring excellent airtightness in buildings: when a traditional double-walled wall lets through up to 2,5 m3 of air per hour, the Thermopierre single wall is crossed by only 0,6 m3 per hour.

This last thus allows compliance with the reference values of RT 2005 and a saving of 5 to 15 kWh/m² depending on the energy source used.

This control of air permeability eliminates the entry of parasitic air which has negative effects on:

• Hygiene and health: the air passing through the walls can become loaded with pollutants (dust, mold, volatile organic compounds, etc.) before entering the home.




• Thermal and acoustic comfort occupants: infiltration of parasitic air is a source of unpleasant sensations (cold drafts, temperature fluctuations, or even an inability to heat properly) and degrades acoustic insulation against outside noise.




• The energy bill : additional heating requirements resulting from parasitic airflows can significantly increase the energy costs of the home.




• Building conservation : condensation in the wall reduces the quality of the insulation and can cause mold.

Xella's commitment: a Quality Plan at all stages of construction

Thanks to its official approval on the air permeability of housing, Xella allows project owners building with Thermopierre single-wall (blocks 25 to 50 cm thick) no longer having to put together a file: you just need to adopt the Quality Plan proposed by Xella to benefit from the reference value for RT 2005The application of this Quality Plan is subject to the prior signing of a reciprocal commitment between the project owner and Xella.

The project owner undertakes to:

• compliance with the Air Permeability Quality standard and its application by project management, companies and their subcontractors;
• the integration of the requirements of the Quality reference system into the specifications of specific technical clauses of companies;
• the definition of responsibilities for on-site verification;
• the organization of the quality system implementation meeting;
• the implementation of third-party measures when they prove necessary (e.g.: BBC-Effinergie label).

In return, Xella ensures:

• training of construction companies and site managers;
• raising awareness among other service providers during the meeting to implement the process;
• assistance to the project management team;
• technical assistance during construction and participation in inspections;
• intermediate and pre-delivery or pre-third-party control measures;
• support for the implementation of corrective actions;
• the final review of the quality system (with the project owner and the project management).

Respect for the environment and users

From manufacturing to transport, on site and until its end of life, the Thermopierre single wall respects the environment, as well as the health of occupants and users.

Manufacturing: Aerated concrete is manufactured in an autoclave, from 100% natural and non-polluting components, using a process developed by Xella. The process consists of imitating a naturally occurring mineral material: tobermorite (hydrated calcium silicate).

During the construction phase: the installation of the Thermopierre single wall requires very light tools.

The easy cutting of the blocks and the precision of the cuts facilitate the reuse of offcuts in masonry and reduce waste. Finally, the quantity of water required is low: the block assembly system, with a thin joint, considerably reduces the water requirement for the preparation of the adhesive and minimizes the impact of cleaning the equipment at the end of the day.