Thermo isolation

Building

In the field of the building, the thermo isolation makes it possible to reduce the heating losses related on the Chauffage or the Climatisation. The thermo isolation is the basic principle of the passive Maison. She imprisons heat inside in winter and guard the fresh house in summer.

The quality of the insulation is generally represented by the thermal Conductivité , is noted U, expressed out of W (m2. K).

The fight against the wasting of energy passes by the thermo isolation of the heated buildings, it is the precise regulation object dating of more than one about thirty years. The insulation of the new residences is obligatory but it is also effective means of reducing the expenditure of heating and air-conditioning (it also functions in summer!) while improving comfort.

Principles

One can regard a house as a bored container of various kinds of holes:

doors and windows,
ventilation,
roofs ceilings,
external walls.

One will thus may find it beneficial to clog simultaneously and in a balanced way each kind of hole. However an on-insulation can not prove to be profitable, as well by the cost of additional materials as by the place occupied by the insulation.

Sources of escape from heat

The sources of escape from heat are the following ones:

the walls external 25%
the floor 20%
the roof 15%
windows and doors external 15%
systems of renewal of air 15%
the remainder 10%

Insulation of the walls

In spite of its reassuring thickness, a stone wall of 70 cm thickness is equivalent 1 centimetre from glass wool in the field of the thermo isolation, the thermal Conductivité of the stone being much higher than that of the air imprisoned between glass fibers. A wall not isolated is cold and will support the Condensation steam, therefore the development of moulds.

Methods of insulation of the walls

There exists 3 principles to carry out the thermo isolation of a wall, they differ by the projected use of the dwelling:

1. the interior insulation and partitions of doubling. This solution, most widespread, is also easiest to put in oeuvre.

The interior insulation will be selected in the case of restorations in the apartments (because it is difficult to intervene on the outside of the building) and for the second home. In this last case, the intermittent occupation does not make it possible to durably heat the thermal mass of the walls. The interior insulation thus leaves the wall outside the isolated zone and allows a rise in fast heating adapted to a temporaire.
use It with the advantage (which is also a disadvantage in certain cases) of not presenting thermal inertia. The counterpart of the interior insulation is a reduction of interior space and the presence of many cold bridges remaining to be treated. The quality of an interior insulation can decrease with time (compressing of wools behind the plasterboards, holes of mouse in polystyrene, etc.)

2. the external insulation and boardings. This solution, often more expensive generally requires a thickness of insulator more faible.

The external insulation is adapted to the insulation of the main homes. It makes it possible to preserve the thermal mass of the wall inside the isolated envelope. The dwelling, heated uninterrupted, goes up in temperature slowly in all its mass but cools slightly when it is inoccupée.
The external insulation is on the other hand difficult to implement on certain old buildings (apparent stone, worked frontages) and almost always requires the intervention of qualified professionals. This last solution will be chosen if the expenditure of heating is important because the insulation obtained is strong. An external insulation is interesting because it does not encroach on the livable field. Its thickness, therefore its effectiveness, can hardly exceed 15 cm but it removes easily the cold bridges (butts of floors,…) except on the level of the foundations. A 10 cm thickness of an insulator external is equivalent to 20 to 25 cm of same interior insulator. One uses it mainly in restoration.

3. The insulation integrated into carrying material. This solution uses materials which integrate an insulator in their structure: gas Concrete, Brick of hemp, terra cotta brick with insulating heart…).

The integrated insulation is generally used in new building. This solution is powerful and durable. The cost of a wall gas monolith of concrete or bricks monomur is appreciably the same one as that of a breeze block added with an insulator and a plasterboard

Insulation of the floors

By Plancher one understands the ground on which one circule : pave in Béton, or floor on Solive S. the ceiling of a level corresponds obviously to the floor of the upper floor. The thermo isolation of the floors is important for comfort (by keeping the feet with the heat) and for the energy saving in the case of a heating flagstone.

The insulation of the floors fights two causes of losses thermiques :

losses towards the lower stage not heated (underfloor basement, Space, quay level…),
losses by cold bridges (see this section).

Owing to the fact that the hot air tends to accumulate with the ceiling and that the difference in temperature between basement and livable volume is less important in winter than between outside and livable volume, the thickness of the insulation necessary is lower (about 6 cm in floor compared to 10 with 20 cm in the roofs).

To isolate to a floor one peut :

either to isolate the under-face from this one by fixing slabs insulating at the ceiling of the lower level or by using a flagstone with insulating hollow blocks,
or to carry out an insulating cover (Concrete with insulating aggregates), a floating flagstone on expanded polystyrene with high density (case of the heating flagstone), a floor on Tie bar S separated by glass wool…

Insulation under the roofs

As the hot air goes up by Convection, the temperature is higher with the ceiling and it is thus logical to place a thicker layer of insulator in the roofs than on the walls. Under the roof the air intake must be more especially treated because there is no sealing of the walls. The layer of insulator must be protected from the intrusions from the Fouine, while closing using a netting firmly fixed space between the rafters at the level of the Sablière.

Several solutions are possible for the insulation under the roof, according to desired thermal resistance and of space disponible :

little space and weak insulation - reflective film fixed under the rafters, expensive and of low effectiveness in practice,
little space and average insulation - rollers Glass wool or wool of hemp fastened between the rafters, of implementation delicate because spacing between rafters is seldom regular,
space available and insulation forte : double thickness of panels of or glass Rockwool or wool of hemp fixed inside a structure out of boxes, between the breakdowns. The structure supports also the plasterboards, of the panels of agglomerate, the plank of pine…

The insulation is installation after the installation of the flues and the windows of roof. To envisage the passage of the ventilation ducts, the cables of Television, the electric sheaths…

N.B. : Note that glass wool and rock can more or less replace good of other materials " écologiques" , that is to say the wood wool, the cellulose (recycled paper), the flax, hemp, the wool of sheep, etc

Insulation of the doors and windows

The glazed openings are the weak points of the total insulation of construction. To limit the surface of these openings is a solution to reduce the losses, to avoid the openings to north and side of the wind (often in the west). This solution however involves a reduction of the illumination of the parts and a degradation of the confort.
One will thus choose preferably the solutions suivantes :

to use the double-glazing with low emissivity 24 mm total thickness minimum (RT 2005),
to choose thick door frames of wood or PVC of good quality,
to avoid the aluminum door frames or to choose the sections with rupture of the cold bridge,
to check the sealing of the joints, including in bottom of doors,
to install tight shutters, if possible with the right of the frontage to limit the effects of the wind. The travelling shutters out of PVC with double walls and external box (in the thickness of the wall) are one of the good solutions. On the other hand the travelling shutters with blades aluminum doubles foam polyurethane walls even injected present a less good thermo isolation. Indeed the blades aluminum support heat exchange with outside contrary to blades PVC
to install thick draw-curtains in front of doors and windows,
to remove the cold bridges on the level of the thresholds and windowsills.

The installation of double-windows is an excellent solution contre :

noise,
the air intake (boxes of travelling shutters, door frame old deformations, difficulty in posing joints).

On the other hand the operation and the maintenance of the double-windows are difficult, their debatable esthetics and their high cost.

The installation of survitrages is generally a cheap and not very effective solution but which can render service in restoration.

To reduce the Infra-red radiation penetrating by the southern glazings in summer, it is possible to stick a reflective film. This solution is rather effective but expensive. In full day, it also protects from the inquisitive eyes (case of the ground floors) if not to choose double glazings with the functions of solar control.

The vapor barrier \ wind-cutter

The interior face of the insulation (hot side) must be provided with a film tight with the air which fulfills two functions: that of vapor barrier and that of wind-cutter. This tight film thus functions in the two directions:

to prohibit with the hot air and charged with steam to penetrate in insulator and to cause condensation,
there to prevent the wind from infiltrating, through the insulation, in heated volume.

The electric raceways and other sheaths which cross the insulation should not support the passage of the drafts, it is necessary to immobilize them firmly and to surround them by Glass wool or foam of Polyuréthane (in the case of an insulation in expanded Polystyrène).

Thermal resistance

The thermal Résistance of a wall depends its thickness and also on the thermal conductivity of material used. In the case of a wall made up of several different materials, it will be necessary to add thermal resistances with each component. In practice it is the layer of insulator (Glass wool, Polystyrène…) who represents most of thermal resistance.

Insulating materials

Installation of insulator

The insulating materials containing or fiber glass fiber of rock are unpleasant to pose. To use gloves, a mask with dust, glasses of safety and a coverall to the collar and the tight wrists. To try to ventilate the room.

The insulation of the supports can be done using wool in roller provided with a vapor barrier which one fastens on the rafters. This solution is not possible that if the spacing of the rafters corresponds exactly to the width of the rollers. In practice the thickness of insulator will hardly exceed 8 cm, which is insufficient in the majority of the areas. It is certainly more practical to use panels cut out with the spacing of the rafters or to place insulator under-face.

To check that the recesses are filled of insulator, if necessary to stuff rock or glass wool in the least holes. To condemn all the openings where rodents could penetrate. One can use of the foam of Polyuréthane to stop the holes or to fill of the cells.

Insulation by outside

The insulation by outside is a solution better than the interior insulation. It allows, thickness equal insulation, to divide by 2 to 3 the losses of heat and to preserve during the summer, by decreasing the transfers of heat, the freshness of the night in the house.

Its advantages are:

removal of all the cold bridges of the flagstones of floor, the cross walls and other partitions,
the use of the inertia of the walls to recover the external contributions, the contributions domestic, and which become with an adequate heating of genuine radiators low temperature,
a better thermal comfort owing to the fact that the heavy walls and thus conducting thermics absorb best the heat radiated by the occupants of the places,
not of condensation in the walls which are at the same temperature as the interior ambient air.

not of harmful gas emanation of polystyrene and adhesive in the air of housing, not of problem of fixing of the pieces of furniture of kitchen and bathroom, and of the curtain rods, not of appearance of the bands of joining.

Its disadvantages:

the external boarding less resistant than a coating on breeze blocks,
a cost a little higher with thermal resistance equalizes which diminishes in two years on the economies of the heating, and on the comfort which one cannot quantify,
some difficulties of reflection to the design for the establishment of the roofs and the garage or basement,
a less accessible technology for the realizable autoconstructor but nevertheless.

Insulation of the drains

Warm water pipings must be isolated by measurement from economy and those from cool water to avoid freezing. The flows (gutters, sewers, drainages of waste water and water valves) should not be forgotten. For the pipes of low diameter (10 to 30 mm) there exist cylindrical sheaths foams about it which cut out easily and can be posed on drains in place. The taps and other accessories can be emmaillotés in glass wool maintained by a polyethylene thin film and adhesive tape. To locate well using a visible label the position and the role of the tap, it can be capital in the event of problem or at the time of the maintenance actions.

The glances external sheltering of the valves (even the meter of building site) must be isolated with expanded polystyrene if they are not sufficiently buried.

In connection with on-insulation

One can be tried to double the thickness of the insulation of the walls. It is not a bad thing but it is necessary to take account of the points suivants :

to double the thickness of glass wool costs 2 times more expensive and does not decrease (to the maximum) the losses only of half. However, the coefficient of thermo isolation (called R) will be doubled. For example, 10 cm of glass wool bring a coefficient R of 2.5, therefore 2 times 10 cm will bring a coefficient R of 5. A cross installation of the two layers will also make it possible to limit the losses.
the thickness of interior insulator is as much of place lost for space habitable : 10 cm of insulator on a circumference of 40 meters (stage of 10x10m) corresponds to 4m ² of lost surface.
to be optimized the insulation must be coherent. The efforts to insulate must be identical for the walls, the doors and windows, ventilation…

Cold bridges

The cold bridges, kinds of short-circuits in the interior insulation, must be reduced to the maximum. With this intention one can act as of the design by preferring a floor on Solive S, a firm interior rather than a Cross wall or more simply by building his wall with an insulating material (gas concrete, brick monomur, etc…). Another solution consists in insulating by outside with the disadvantage of leaving a cold bridge to the level of the foundations.

At the time of the realization one will be able to apply different solutions :

to detach the cross walls to be able to insert the layer of insulation between the end of the partition and the external wall.
to isolate the turn from flagstone using a hollow brick or planelle out of gas concrete.
to double the cross walls with a layer of insulator of a few centimetres
to pose an isolated false ceiling or to insulate the floors under-face
to carry out floating flagstones

The development of moulds on the walls betrays the presence of condensation, therefore of a cold zone caused by a cold bridge. As it is difficult to treat a cold bridge a posteriori , one can try to paper the walls concerned using a thin layer of insulator (a few millimetres) covered with a wallpaper or a wall lining (fabrics…).

Thermal inertia

In a part isolated by a layer from insulator and a light partition of doubling (interior insulation), thermal inertia is weak and it is enough to little time to heat the air of the part. This property is an advantage in the case of a heating programmed item by item.

On the other hand, in summer, the least sun ray will raise the temperature brutally and the latter will drop as quickly as it will have gone up when the sun disappears. The feeling of discomfort is clear.

The use of an external insulation or massive wall insulating out of gas concrete or alveolate brick makes it possible to thus increase thermal inertia the reduction of the temperature variations.

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