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Insulating walls from the inside is the easiest and most economical way to improve the thermal performance of a home. The choice of a thermo-acoustic glass wool also makes it possible to protect external noises. Here are the steps of laying on metal frame.

Thermo-acoustic glass wool thermal insulation

Necessary material

Difficulty: 2/4
Cost: about 550 € (18 m2)
Time: 3 days (including siding)
Equipment: meter, spirit level, cutter, puncher, screwdriver, nibbler or shear, crimper, woolen knife, putty gun, handsaw, plasterer saw, hole saw, electrician's tool, trough, gloves and mask protection…
The plan of this realization "thermal doubling on metal frame" on

Since they can not isolate their house from the outside (cost, moldings, etc.), the owners of this house opted for thermal insulation from the inside. For this, they chose a doubling made of glass wool and wood fibers (Isoduo 36 d'Isover, thickness 120 mm), completed with an airtight membrane (Vario Xtra d'Isover) on the insulation before fixing the siding.

Find the right compromise

The thermal regulation (RT) applicable to renovation depends on a decree of May 3, 2007. Among other provisions, this text sets a minimum thermal resistance (R) of 2.3 m2.K / W for walls in contact with the outside. The ideal is to approach the values ​​recommended by RT 2012, a coefficient R ≥ 4 (value in nine and heavy rehabilitation).
To achieve the minimum value required by the 2007 RT on masonry walls, only 90 to 100 mm of mineral wool is required. However, to obtain a coefficient R ≥ 4, it takes 150 to 160 mm of insulation. The trick is to find the right balance between thermal efficiency and the least penalizing dimensions (especially in terms of loss of internal surface).
Note that the insulating complexes (Calibel d'Isover, Labelrock Rockwool, Panelplac Reno Ultra Knauf...) can reduce the thickness, but on perfectly flat and regular walls.
Another important point is the acoustic treatment. The performance of an insulator is characterized by its sound reduction index (Rw).

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Glass wool panel: acoustics and more

The higher the value of the index, the more the material attenuates the sounds. This data obviously varies depending on the nature of the walls (reinforced concrete, brick, blockwork...). The index is then accompanied by the terms "C" or "Ctr", the first concerning the isolation vis-à-vis the noise in the high frequencies (neighborhood, industrial activities, airport...), the second is linked to the low frequencies (in particular noise from road traffic).

Glass wool: laying of an insulating lining on metal frame: wool

Learn more about this theme?
Find a special file in System D n° 858 (July 2017)
Check it out

Insulation: laying intermediate supports of the frame

furs for metal structures

The walls receive two horizontal furs, spaced 80 to 100 cm from the ground and between them.
They allow the clipping of the supports of the studs.

insulation: cut the furs of a metal frame

Measure the lengths of furs to ask.
Mark the cuts on the profiles and use a good sheet metal shear to cut them as cleanly as possible.

screw the furs of the metal frame

Draw the laying axes to the ruler and the spirit level.
Pre-pierce the furs and postpone the anchors on the walls.
Drill and peel the wall, then screw the furs.

insulation: wife of a metal frame around a windows

Mark the locations of the insulation support pads every 60 cm.
Along the windows, take into account the thickness to be reserved for the dressing of the frame.

thermal doubling: laying of supports of the metal frame

Clip the supports in the furs with a rocking motion.
If necessary, rectify their spacing before placing the spacers, then the jumpers.

Practical tip

nest foldable connectors to ensure furring of the furs by clipping

For singular points such as the inner jamb of the windows, fit folding connectors (Connector Optima Isover) to ensure the assembly of furs by clipping.
Arrange them every 30 to 40 cm maximum to ensure a good rigidity of the angles.

Fixing the framework frame of the thermal lining

doubling: lay the high arm on the metal furs

To align smooth, start by clipping the furs on the intermediate supports.
Check the alignment and plumb, then snap the top smooth over the furs and slide them against the ceiling.

doubling: laying the rails of a metal frame

Secure the rails with self-drilling screws in the false ceiling frame (previously doubled).

doubling: how to slide an extension in metal furs

Here the ceiling height is 260 cm.
The fur being shorter, slide a splint (extension) into the furs and pull it to clip it into the rail.

doubling: how to screw a smooth floor

After clipping each splint into the rail, check the plumb of each fur again, then screw the rail straight into the floor with the same screws.

fix a metal frame around a window

Under the window, fix an amount (M48) then a fur below.
Place the supports and extend the frame.
To style furs cut with a smooth.

laying a thermal doubling frame around a window

The section of the upright (depth 35 mm) provides a better support for the coating.
Control the horizontality, verticality and alignment of the elements.

Slide the semi-rigid insulation panels into the studs

The spacing between the frame and the wall was calculated according to the thickness of the insulation ("Isoduo36" of Isover, thickness 120 mm).
Wear gloves and a mask, then slide the insulation boards behind the frame.
If necessary, cut in length with a woolen knife, and continue laying, always from bottom to top.

Info +

adapt the length of the thread to the different thicknesses of insulation

Designed in two parts, the parts of the support are joined by a thread.
It is easily cut using a cutting tool to adapt its length to different thicknesses of insulation.

Application of the waterproofing membrane of the insulation

thermal doubling on frame: laying of a waterproof membrane

The insulation is covered with an airtight membrane (Vario Xtra d'Isover).
It is laid using a double-sided adhesive glued on the whole frame (furs and smooth).

lining: laying overlay of a flexible membrane

The strips are covered by covering 15 to 20 cm.
Cut the lé by adding 2 cm to the ground (they will be masked by the thickness of the facing and the plinth).

grout the flexible membranes

Place the lé on the double face and join it to that already present under the support of window posed beforehand.
The total sealing of the joints is ensured by a special adhesive (Varion KP1 or Vario Multitape Isover).

Glass wool: laying of an insulating lining on metal frame: lining

The peripheral fixation is reinforced by a bead of sealant provided.
Extrude the putty and rub with your finger.

Glass wool: laying of an insulating lining on metal frame: wool

At future plugs and switches, cut the membrane crosswise to the cutter.
Glue an airtight rubber eyelet and pass the electrical sheath.



Alternative to plasterboard for window sill: a solid wood board that you attach to the frame from underneath (after placing a le). Apply two coats of varnish by peeling the support between each layer (120 grit sandpaper).

Screwing the facing of the thermal lining

plasterboard cladding

The plasterboard cladding starts from the sides of the bay.
Use a drop of plasterboard to measure the exact width of the strips to be laid on either side.

Glass wool: laying of an insulating lining on metal frame: lining

Position the band without securing it.
As it comes face-to-face, it is best to cover the adjacent wall first.

how to screw a placo plate

To make screwing easier, draw pins on the furrows and screw them on, then fix the band.


cut the plasterboard

You can cut the plasterboard conventionally (cutter, handsaw) or use a special tool, type "BladeRunner".
Composed of two magnetic bodies, it allows to cut both sides at the same time.

Knauf plasterboard installation BRA13

Dress the window sill and continue laying plasterboard (here BRA13 from Knauf).
Equalize visible cuts with plasterboard.

locating the location of drywall installation boxes

Before placing the plates, locate the location of the drywall installation boxes and drill their housing with a hole saw.

to pass the electric cables in placo

Remove the cover at the bottom of the flush-mounting box, route the cables and insert the box.
Check the level (put the tool on the fixing screws) and tighten the clamps.

grout the placo plates

Recap the screw heads and grout the plates by embedding a strip of paper into the plaster.
Protect sharp edges with strips of reinforced paper.

Insulation board: mini thickness, max performance

Intended for the soundproofing of partitions and ceilings, this doubling complex (Placo Phonique Rénomince) provides up to 16 dB of acoustic improvement on common hollow materials: plaster bricks, cellular plaster tiles...
Composed of 20 mm thick glass wool laminated to a specific BA13 plate, its overall dimensions do not exceed 50 mm thick.

lay the placo plates

• Fix the furs horizontally, up to about 10 cm from the floor and ceiling. Observe a center distance of 67.5 to 73 cm.
Place the first plate against the framework.

screw the Placo Phonique Rénince insulation plates

• Using small wedges, provide a 5 mm peripheral clearance.
Check the plumb, then screw in the furs every 15 cm.

thermal lining: joint with acrylic sealant

• Once the wall is covered, fill the peripheral set with acrylic caulk.


• Galvanized steel frame (smooth and fur)
• Locking jumpers
• Anchors, screws
• Insulating panels
• Airtightness membrane
• Double-sided adhesive, insulation adhesive
• Sealant
• Plasterboard
• Self-drilling screws
• Built-in boxes for drywall
• Joint band
• Joint plaster

Video Instruction: Thermal acoustic insulation NATUR: suspended ceiling