Thermal insulation from the outside in roof: light or heavy?

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17/11/2022
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Batirama.com 06/29/20200

ITE processes are still under heavy and poorly understood work.Yet solutions exist to lighten their implementation as their carbon footprint.

"The ite represents less than 5 % of the market and for two thirds in new," informs Éric Barnasson, product marketing manager and systems at Saint-Gobain ISOVER."But, this segment remains growing and with high added value, since it is a question of completely redoing a roof".

The fact remains that "for this ite to be mature, it would be necessary that professionals recommend it more often.They fear the additional cost when it is anecdotal, especially when you activate the EEC mechanism ".In the meantime, if private customers remain unrecognized, manufacturers deploy their greener solutions.

Biosourcé for mechanical resistance

The future re 2020 introduces the concept of carbon impact, the ite is.With a push in favor of the biosourcé.Like the majority sarking on this market which added to the polyurethane, and to the rock wool, the wood fiber."It is less the ecological dimension than the mechanical constraint that will push this bio -based material in front of rock wool, which is favored for strong thermal resistances", specifies Éric Barnass.

This sarking also attracts favors in front of a experienced box, "difficult to handle in renovation".But that is without counting on another roof panel which intends to surf its featherweight for easier renovation, and the RE 2020 to win.

The carbon footprint could boost lightness

Continuous insulation, abolished thermal bridges, air waterproofing ... The sandwich panel is noted by point in the RT 2012 requirements.But he still has to fight."For many, its lightness means that it is not solid," notes Gilles Rattin, commercial director at Quickciel.While waiting for the end of preconceived ideas, it also argues roof panels, a more favorable "carbon footprint than a experienced box.The latter's strength was his center distance, but today they are less good than those of a sandwich panel, "said Quickciel leader.

"Like its thermal resistance, which requires reporting an insulation to reach an effective and controlled 6 R of 6" when that of a sandwich panel can reach an R of 9 ... alone.In addition, he advances a made in France, "and a pre-user tailor-made solution that limits construction waste-the falls are recycled at the factory-knowing that our panels already enhance oil waste".

Isolation thermique par l’extérieur en toiture : légère ou lourde ?

A reduced carbon assessment associated with performance that could boost this ultra light items?Provided that professionals are starting to take an interest in it ...

Solution 1: Sarking: the most common

In renovation, sarking is an ideal solution when it is necessary to keep the volume of the attic and isolate the roof without touching the interior finish.The Sarking technique remains reserved for traditional frames in accordance with all DTUs in the 40 series, Eurocodes and the mountain climate coverage guide, if applicable.

The nesting profile is particularly effective against thermal bridges and facilitates the implementation.This market sees the emergence of new insulating panels.Like those in ultra light XPS when resistance to humidity is expected or in phenolic, light foam, with higher thermal performance than the polyurethane leader and resistance properties for combustion.Little used technology that requires checking technical opinions, if applicable.

Mixed materials

The other emerging trend on this market: the mix of wood and polyurethane fiber materials.Synonymous with more lightness but above all less substantial roof raising for a preserved aesthetic.

Of Biosourcée RE 2020 requires, wood fiber contributes to summer comfort thanks to its strong phase shift for four -season insulation.In addition to the thermal complement and its complementary mechanical rigidity, this wood fiber brings implementation and acoustic comforts, it softens the drum skin effect in the rain that a PU only propagates.

Advantages

: adaptée à toutes les pentes et à tous types de couverture ; technique connue ; isolation continue ; ponts thermiques et étanchéité à l’air maîtrisés ; solutions existantes avec FDES.

Disadvantages

: non porteurs, mettre un platelage bois pour éviter les chutes dès que possible ; attention au dimensionnement des vis entre chevrons à respecter selon les préconisations des fabricants ; vérifier l’existence d’avis techniques.

Solution 2: Box: the most seasoned roof panels

Using experienced boxes allows you to make a roof in only two operations - installation of boxes or panels, then cover - by reducing working time.80 % of the roof panel market with integrated insulation to maintain an apparent frame (traditional, in solid wood or glued laminated), create living space or even saving square meters are made in an experienced box.

Insulating system cover support on ventilated air blade, it consists of fixed solid wood rafters and treated in the factory, (two or three depending on the industrialists) solidarity with an underside panel that constitutes the ceiling.The experienced boxes attach directly to the frame, on a number of reduced breakdowns substituting traditional rafters.

In a single operation, experienced boxes make it possible to make the insulation, the renovation of the roof and the interior decoration of the ceiling in a wide choice of decorative finishes.Note that in 95 % of cases, the insulation which completes this system is either polyurethane, or expanded polystyrene.

Advantages

: solution finie, apporte des réponses mécaniques et techniques notamment au niveau du traitement des points singulier ; gain sur la mise en oeuvre.

Disadvantages

: difficile à manipuler ; nécessite de rapporter un complément d’isolation pour atteindre un R de 6 avec du coup rehausse de toiture ; chevrons dans l’isolant créant un rupture thermique ; plus adapté en neuf qu’en rénovation.

Solution 3: Sandwich panel: continuous insulation

Light (18 to 20 kg/m2) authorizing a laying on long litters, sandwich panels are synonymous with performance and continuous insulation.Sandwich panels are also synonymous with habitable volume optimized in particular at the attic level.They must rest directly on the breakdowns of the frame in order to cover the roof with a single holder.They therefore require renovation to delete rafters.Rhyme with absence of thermal bridge, high thermal resistance (up to R = 9 (m2.K)/w), waterproofing and ventilation of the cover elements ensured, once the roof is deposited, it is again out of water and out of air in 24 hours.

These sandwich panels are also available with integrated metal rafters for all types of slope.To make convertible attic roofs, isolated roofs under farmhouse, or to be installed in renovation with an exterior installation directly on the existing frame.Self -supporting, robust and resistant, they display a high mechanical resistance, hence an interest in mountain roofs, and the possibility of making long lengths on request.

Advantages

: pas de rupture de l’isolant pour une continuité thermique et de l’étanchéité à l’air, zéro déchet si pans traditionnels, moins coûteux, performance acoustique.

Limits

: nécessite des prises de cotes précises, , peu économique si traitement de points singuliers tels que l’intégration de fenêtre de toit.

Solution 4: Roofing of roofing

The roofing of roof, the heaviest ite, nevertheless displays the highest performance with thermal resistance capable of reaching an R of 12.This system with pillars meets several requirements, BBC, BEPOS and provides a level of weakening much higher than the requirements of the acoustic regulations in force.It’s the Rolls Royce of the ite.

During the enhancement with metallic pillars, the mechanical constraint is taken up precisely by the pillars, and the over-housing implemented.The insulation no longer has a mechanical function to perform.It can therefore simply be efficient glass wool.This solution makes it possible to offer the highest thermal resistances since it is possible to interpose up to three layers of insulation: between rafters, on the rafters, and between the over-chevrons until the outcrop of the sur-Chevronage run by metal pillars.

A solution under technical advice, intended for trained companies capable of carrying out load recovery calculations from the abaccs provided in technical opinions.But this very heavy solution considerably increases the roof height.If it has the advantage of being able to put three layers of insulation for optimal performance, this total roofing repair is generally the most expensive.So the least often posed.