Thermal bridges between floor and wall

As an insulation specialist, HIRSCH Insulation advises you on solutions for the treatment of these thermal bridges and guarantee a high-performance envelope. Discover our solutions for a sustainable and healthy building.

The essential in 3 points

With regard to the overall losses of a building, the treatment of thermal bridges between the floor and wall may sometimes seem secondary, but it is a quick and simple operation which, in addition to being a regulatory obligation, offers many benefits for the durability of the building, the thermal performance and the comfort of the inhabitants.

Integrated thermal bridges

Integrated thermal bridges

thermal bridges

Thermal Bridges

1. What is a thermal bridge?

A thermal bridge is a discontinuity in insulation causing energy loss. There are two main types: integrated thermal bridges and connecting thermal bridges.

Integrated thermal bridges

Integrated thermal bridges are created in a wall by elements with a higher thermal conductivity, e.g. a rail or a metal support. They may also be due to a defect in the installation or assembly causing a mismatch between the insulating elements. These thermal bridges are not to be neglected as they can lead to a strong increase in wall losses, even doubling them!

Thermal bridge connections

Thermal bridges are found at the interfaces between two walls, typically between a slab and a wall, around window frames or at the level of balconies. The heat loss due to the discontinuity of insulation results in a flow of heat from the heated room to the outside or to an unheated room. This is called a linear thermal bridge. This value Ψ (psi) is expressed in W / (m.K) and varies from 0 (no thermal bridge) to 1.5.

Why treat thermal bridges?

A regulatory obligation

In an uninsulated building, the share of thermal bridges in the overall heat loss will be low (about 5%) because the heat loss will be mainly from the walls. On the other hand, on a building with a highly insulated envelope, the proportion of losses due to thermal bridges will logically increase and may represent between 10 and 40% of total losses depending on the type of building.

Since the first thermal regulation of 1974, faced with an increasingly better insulated envelope, the share of thermal bridges in the building's losses has therefore continued to increase, until the 2012 RT. The latter has integrated two safeguards relating to the treatment of thermal bridges for new buildings:

  • A limit value for the Ψ between the intermediate floor and the outside wall of 0.6 W / (m.K).
  • An overall limit value for all the thermal bridges of the building (relative to its surface area) set at 0.28 W / (m²SHON RT.K), which allows a certain flexibility in the constructive choices by allowing compensation between the different thermal bridges.

By defining these guardrails while leaving the choice of the constructive solution to the client, RT 2012 has thus imposed the treatment of thermal bridges and has been a real accelerator in their systematic treatment on new constructions.

Since the first thermal regulations of 1974, the share of thermal bridges in the building's heat loss has been steadily increasing.

Distribution of the losses of an uninsulated building with impact of thermal bridges

Failure to treat the thermal bridges of intermediate floors can increase a building's energy consumption by 5 to 25%.

A way to reduce energy consumption

Reducing energy loss, yes, but to what end?

  • As the cheapest energy is the energy that is not consumed, reducing waste will reduce energy consumption and therefore reduce the energy bill for the building's occupants.

Failure to treat the thermal bridges of intermediate floors can increase a building's energy consumption by 5 to 25%, depending on the construction methods used and the type of energy used. This impact on energy consumption can also be observed in terms of environmental performance and greenhouse gas emissions: over-consumption due to untreated thermal bridges represents 11% of consumption in the Building Life Cycle Analysis, as well as Greenhouse Gas Emissions of 60 kgeqCO2/m² over the 50-year operating life.

  • In single-family homes, the use of thermal bridge breakers will make it possible to gain around 8 points of Cep - the primary energy consumption of the building in kW per m² per year, including heating, domestic hot water production, air conditioning, lighting and auxiliaries. This is a significant gain in view of the low cost of these products and their ease of use.

Failure to treat thermal bridges therefore significantly degrades the environmental impact of the building and significantly increases energy consumption and greenhouse gas emissions.

A question of durability and comfort

Beyond the issues of performance and savings, the treatment of thermal bridges is crucial for the building's durability over its entire life cycle.

This operation will be carried out during the construction of the structure, from the structural work, and will guarantee a high-performance building in the long term. Indeed, unlike equipment that can be improved over time and technical developments, thermal bridges cannot be treated afterwards: not treating them means leaving several generations of inhabitants with a defective building that is a source of pathologies.

One of these pathologies is the formation of mould, which is most often found at the junctions of interior walls or around joinery.
In these areas, if the thermal bridge has not been treated, the surface temperature of the wall can be much lower than that of the heated room, creating condensation that can lead to the appearance of mould. Mould can have a significant impact on indoor air quality and thus on the health of the occupants.

Feelings of cold floors (near the junctions with the walls), cold walls or rising damp in crawl spaces are other adverse effects on the comfort of the inhabitants that can occur if thermal bridges are not treated.

Appearance of mould at the corners of the floor-wall connections in case of insulation discontinuity. A cold zone is created on the surface and encourages the appearance of condensation and, eventually, mould.

Thermal bridges with and without ITE

Insulation from the outside is an effective means of eliminating thermal bridges between the floor and wall by adding insulation that is fixed or glued to the wall.

3. What solutions for the treatment of thermal bridges?

The treatment methods will vary according to the construction method chosen, the materials used, the type of insulation envisaged and the connection considered. There is therefore no standard way to treat a thermal bridge, as regulations leave the client free to choose the appropriate solution.

Cellomur® range: the solution for external insulation

Insulation from the outside is an effective means of eliminating thermal bridges between the floor and wall by adding insulation that is fixed or glued to the wall.

This technique also has the advantage that it can be used for both new construction and renovation.

The Cellomur® range offers a complete solution for the insulation of facades under thin plaster. White or graphite polystyrene panels with high thermal performance, glued or anchored to the wall, have exceptional dimensional stability (no settling over time or shrinkage of the insulation), flatness and durability.

To find out more about the Cellomur® range and the Hirsch offer for ITE, find our guide for external thermal insulation.

Installation of external thermal insulation in renovation with Cellomur Ultra

Thermal insulation from the outside in single-family house renovation with Cellomur® Ultra panels.

The Epsilon® System: breakers and accessories for joist floors

Beam floors are the construction method of reference in single-family houses, whether on crawl space or intermediate floor. This constructive solution presents, in case of insulation from the inside, a thermal bridge at the connection of the compression slab with the load-bearing wall, especially when using concrete spacers (or slabs). Another thermal bridge is located at the level of the splitting walls.

The Epsilon® System is a combination of expanded polystyrene insulation pads and thermal bridge breakers. It is used to insulate floors with joists in the running part and to treat linear losses using thermal bridge breakers.

Several product combinations are possible, depending on the flooring and the level of insulation and thermal bridge treatment required:

  • The Hourdissimo® or Voutissimo® insulation pads

Used alone, they act as partial breakers by reducing the concrete thickness of the slab. Their tabs also cover the underside of the joists to treat this thermal bridge integrated into the floors.

  • The Hourdissimo® or Voutissimo® Coffrant

They will also serve as partial breakers, without providing insulation on the undersides of the beams. Due to their reduced weight and their partly running insulation, they are an advantageous replacement for concrete slabs for the construction of intermediate floors or under roof terraces.

  • For maximum performance, these units should be coupled with Rupsilon® TLR , Rupsilon® PI or Rupsilon® PI Protect switches. The use of these breakers allows an efficient treatment of thermal bridges at a reduced cost and time of implementation.
  • Finally, the most effective solution in terms of reducing the thermal bridges in the floor is the use of an insulation under screed that complements the polystyrene interiors: the "Duo" floor.

Applied after the walls have been insulated, insulation under a floating screed using a Solichape®, Maxisol®, Maxissimo®, Solissimo® Heating or Solissimo® Silence panel will reduce the linear thermal bridge by up to 70%.

To learn more about the Epsilon® System, find our guide in the Documentation.

treatment of the thermal bridge of slitting with the Rupsilon TLR breaker

Insulation of the floor shear wall with Rupsilon® TLR panel and Omega fastener.

Voutissimo joist floor insulation

Insulation of a floor with prestressed beams with Voutissimo® entrevous.

Floor design duo floor between you insulation and insulation under screed

Duo flooring with insulated between you and additional insulation under screed.

Focus on thermal bridge breakers

Thermal bridge breakers are insulating elements that allow the connections between the walls of a building to be treated. Placed at the end of a slab, they ensure the continuity of the insulation from the inside and reduce losses.

In addition to their thermal role, breakers must guarantee the structural stability of the structures in which they are integrated - particularly in seismic risk zones - as well as the fire resistance of these structures. They also have an acoustic role in the transmission of noise between rooms.

Switching systems available on the market must have a Technical Opinion from the CSTB. The HIRSCH Insulation system is covered by the ETCA No. 3.1/16-888.

Floor range page - Rupsilon PI

Thermal bridge breaker Rupsilon® PI.