Thermal Insulation → Thermal Insulation Materials

In order for a material to be a thermal insulation material, its thermal conductivity coefficient (λ) has to be less than 0.065 W/mK according to ISO and CEN standards. The smaller the thermal conductivity coefficient of the insulation material is, the higher the resistance to heat transfer is. Thermal conductivity calculation values (λh) in TS 825 standard (Turkish standard) are the thermal conductivity values determined at 23 ° C temperature and 80% relative humidity.

 

An important feature in thermal insulation materials is water vapour diffusion resistance factor (μ). Water vapour that occurs indoors has a potential to damage buildings. Water vapour, due to the pressure difference, moves in the same direction as the heat flow, passes through the pores of the construction element and tries to reach the external environment. During this transition of water vapour within the structural element, in case of saturation or contact with a surface at a lower temperature, some of the vapour condenses into water. This condensation is undesirable for the carrier system of the structure. In such a case, it damages the concrete and reinforcement. It is an issue to be considered in the selection and calculation of the thickness of thermal insulation materials.

 

 

Table 1. Thermal conductivity calculation values of various building materials

Material Thermal Conductivity Coefficient Value (λ) W/(m.K) Metals 35,0 – 384,0 Reinforced concrete 2,20-2,50 Concrete 1,65-2,10 Brick 0,19 – 1,40 Aerated concrete 0,11 – 0,29 Batting, EPS, XPS, polyurethane and Polyisocyanurate foam 0,020- 0,045

 

Table 2. Water vapor diffusion resistance factors of various building materials

Material Water vapor diffusion resistance factors (μ), [-] Glass wool and Stone wool 1,0 EPS 20-100 XPS 80-250 Polymer bitumen sheeting 20.000 Polyethylene foil 80.000 Glass 1.000.000 Metals 1.000.000

 

Extruded Polystyrene Foam (XPS)

The material is derived through by melting and extrusion (rolling) of polystyrene raw material. It has a homogeneous closed-cell structure. It is produced in the form of boards and is used for thermal insulation. The boards have smooth or rough surface. They can have different densities (≥25 kg/m3). Thermal conductivity calculation value is 0.030-0.040 W/mK. Fire reaction class is D or E.

 

 

 

 

Expanded Polystyrene Foam (EPS)

It is made through expansion of small particles of polystyrene. It is produced in moulds in the form of blocks through vacuuming and pre-blowing of the expanded particles at a given temperature during which process the particles are glued to one another. Then the blocks are cut into plates with desirable width.

In order for EPS boards to be used for thermal insulation on facades, they should possess given indicators of solidity and specific properties. Usually, this is done at density between 15-25 kg/m3. The EPS plates consist of 98% of still air and 2% polystyrene.

Thermal conductivity calculation value ranges between 0.035-0.040 W/mK. Reaction to fire class is E (it can rarely be fire class D).

 

 

 

 

Glass wool

It is an open porous material formed by melting silica sand at temperatures ranging from 1200° C to 1250° C under high pressure. In order to turn into fibre, the material passes through fine sieves. It is produced in different densities (14-100 kg/m3) in the form of mattresses, sheets or rolls with or without coating.

Thermal conductivity calculation value is 0.035-0.050 W/mK. Glass wool is an A1 or A2 class non-combustible material.

 

 

 

 

 

Stone Wool

It is an open-porous material formed by passing basalt and diabase stones through fine sieves at temperatures between 1350° C and 1400° C in order to turn into fibres. They can be produced in the form of mattresses, sheets or rolls with different coating materials at different densities (30-200 kg/m3) with or without different coating on one or both surfaces.

Thermal conductivity calculation value is 0.035-0.050 W/mK. Stone wool is an A1 or A2 class non-combustible material.

 

 

 

 

 

Hard Polyurethane Foam (PUR)

Polyurethane foams consist of a mixture of polyol system and isocyanate in certain proportions and expanded additive. Polyurethane can be expanded up to 100 times to its liquid volume.

Thermal conductivity calculation value is from 0.025 to 0.040 W/mK. Fire reaction class is D, E or F.

 

 

 

 

 

 

Cellular glass (CG)

Glass foam is produced from waste broken glass pieces combined with cellular filling material. These two components are placed in a furnace and heated up to about 510° C. As a result of the decomposition of the material, the mixture expands and fills the mould. The densities of glass foam vary from 100 to 150 (kg/m3).

Thermal conductivity calculation value is 0.045-0.060 W/mK. It is a class A non-combustible material.

 

 

 

 

 

 

 

Steps for applying exterior combined thermal insulation system with coating:

1. Inspecting and preparing the plaster base/Inspection and preparation of the plaster base (application surface)

• The base has to be levelled well (maximum deviations from the plain up to 1-2 cm)
• Old, crumbling or peeling plasters are removed/scraped and patched
• The facade should be cleaned and dusted
• Moisture and water permeability should be checked
• The system can be directly applied on the masonry in new buildings
• Before the thermal insulation application starts, all wet construction on the interior of the building should be completed; the roofing construction should be finished (hydro insulation application); windows and doors installation should be completed

2. Gluing/adhesion of insulation boards

• Gluing is performed from bottom to top (starting from the bottom plate) in horizontal direction across the width of the facade
• First, a thin layer /film of glue (around 1 mm) is applied on the glass mineral wool boards in order to have a better bond with the main layer of glue
• When positioning the boards, their joints should be ½ joint apart
• The joints between the boards should not be a continuation of the edges of the channels across the facade
• Only whole boards or boards cut in half are placed/positioned along the edges of the building (secure them so that they don’t run continuously)
• The edges are trimmed after the glue has hardened
• In order to avoid thermal bridges, open joints or joints filled with glue must not be left between the the boards. However, if that happens, the joints are filled with pieces/strips of thermal insulation material or unexpanded polyurethane foam
• Spread the glue along the edge surface of the board in lines around 5 cm wide by 1-2 cm thick and add three medium balls in the centre (“edges and balls” method). Leave a small gap in the glue spread with EPS boards so that the air is released immediately after the board is pressed towards the wall. This will enable better adhesion and levelling. This is not necessary with mineral wool boards because air passes freely through them
• The layer of glue should comprise minimum 40% of the whole area of the boards
• When the base is smooth enough, the boards can be glued through the brush and trowel adhesive application method (10 mm)
• Only boards with good mechanical properties, vapour and water permeability and fire protection are used for the insulation of facades

 

Figure 1. Expanded Polystyrene Foam (EPS) plates/boards

 

Figure 2. Attaching the plates/boards to the facade (method of spreading the glue/adhesive – “edges and balls” method)

 

Figure 3. Attaching the plates/boards to the facade (overlapping in the corners; applying boards around openings)

 

3. Thermal Insulation Rawlplugging/wall plugging

• Dowels are always used for mounting thermal insulation plates/boards on:

– Concrete surfaces
– Plastered surfaces
– Mineral wool MW-PT

• Rawlplugging follows a specially designed working scheme. The recommendable number of dowels for buildings up to 50 m in height and wind speed up to 135 km/h is 6 pieces/m²
• It is obligatory to calculate the number of dowels along the edges of the application surface, as well as when the acting tensile load is higher/in areas with higher density; then the number can reach 10-12 pieces /m²
• The anchorage depth depends on the type of the dowel and the type of the concrete base (≥ 25-35 mm)
• Use a drill star with a diameter matching the rawlplug
• Injecting with a power drill shall be done only with plain concrete or common thick bricks. With cavity bricks or hollow concrete material masonry dowels shall be used
• Mineral wool boards are injected with unthreaded screws
• The anchoring embedment depth is equal to the length of the dowel stem plus 10-15 mm
• Rawlplugging shall be done through the adhesive layer, i.e. where the board/plate is glued to the wall
• Dowels shall be inserted only after the adhesive has completely cured (the minimum required curing time is 24 hours after the adhesion with cement-based glues)
• Depending on the type of dowel, the pin is either lightly hammered or screwed. Check if the dowel holds firmly to the surface. Damaged or not well-injected dowels/plugs are removed and replaced with new ones that are inserted some distance away from the old ones. The holes are filled with the same thermal insulation material
• When hammered, the head of the dowel/plug needs to dip into the board/plate and later be either plastered or covered with a top from the same thermal insulation material

 

Figure 4. Dowels – types and usage

 

Figure 5. Plugging scheme: T-scheme (EPS XPS plates.boards) and W-scheme (mineral wool plates)

 

Figure 6. Plug length (examples, rough calculation)

 

4. Shaping of angles, joints, additional reinforcement mesh

• Additional operations are performed before applying the top coat siding, which determine the exterior appearance of the facade
• Exposed to the direct influence of the sun rays for more than 4 or 5 days, the Expanded Polystyrene facade boards (EPS-F) form a layer of patina. This film formed on the material is yellowish in colour and is an obstacle for the formation of a strong bond with the next layer of plaster. These boards should re-sanded in order to remove the patina and the dust
• It is recommended as well to sand the boards in order to smoothen edges and projections across the surface
• With mineral wool plates/boards, before applying the top coating, a thin layer of material is applied to make the surface smoother
• Subbasement profiles, corner profiles, dripstone profiles, etc. are used
• Diagonal reinforcement mesh (strips of fiberglass textile material 30 х 50 cm) is used along the edges of window and door frames, etc. in order to bare the tangential stress/shear stress in these areas

 

Figure 7. Corner Profile with mesh: It is made from plastic or aluminum; it protects the outer edges of the facade of the building

 

Figure 8. Dripstone Profile with plaster mesh (for open or hidden installation): It is a profile made from plastic. It protects bay windows, balconies, window frames and doors from rain.

 

 

Figure 9. Subbasement Profile with dripstone: It is made from aluminum; protects the bottom plate of the facade from rain water when the facade surface protrudes over the bottom plate. Dripstone Profile with plaster mesh for installation over subbasement profile: it is made from plastic with self-adhesive band/tape for attaching to aluminium profile

 

Figure 10. Window profiles with plastic mesh (installed to the window frame): it is a plastic profile with polyurethane insulation strip for increasing the degree of freedom between the thermal insulation and the window frame (with a possibility to absorb temperature deformations) and a plastic bead mold with adhesive tape for protection from dirt during the building process

 

Figure 11. Deformation joints profiles with plastic mesh: it is a plastic profile with UV-stable strip for absorbing construction deformations between separate sections of the building (up to certain values, usually up to 5-10 cm)

 

Figure 12. Diagonal fiberglass textile mesh strips: for reinforcement of edges around openings on the facade with dimensions 50 cm x 30 cm

 

Figure 13. Details for thermal insulation applications around windows and doors when the external surfaces of the frame and the wall fit together.

 

5. Applying thermal reinforced insulation plastering

• Plastering is applied with a trowel to comb vertically the setting materials (10 mm)
• Fiberglass mesh, which is resistant to tensile stress (and does not permit cracking), is integrated into the plaster. Usually, the mesh gap dimensions are 4×4.5 or 5×5 mm and the tensile strength is at least 2000 N/сm²
• The mesh is spread from top to bottom into vertical strips and is then straightened. The overlap between the strips has to be minimum 10 cm. The minimum distance between the overlapping strips is 10 mm
• The mesh is pressed so that the plastering mixture squirts through the gaps, after which the surface is combed to become smooth. If necessary, an additional quantity of material is added
• The mesh should occupy the centre or the outer third of the reinforced plastering layer. After combing the plaster, the mesh should not be visible
• The surface/base is left to dry for 5 to 7 days depending on the weather conditions

 

Figure 14. Fibreglass reinforcing mesh (to be integrated into the thermal insulation plastering)

6. Applying the basecoat layer and the final layer – paste-based render

• The primer is usually applied 24 hours before applying the render in order to equalize the absorbency of the base, to bond left dust particles (if any) and increase the bold between the render and the plastering layer
• In order to increase the tensile strength of the plaster against hail and other mechanical impacts, the minimum thickness of the paste-based plaster/render should be 1.5 mm. The maximum thickness vary up to 3 mm or more. Plasters differ from one another not only in their thickness, but also in their structure (the most commonly used in practice ones are the so called scratched and combed plasters)
• The main properties of final plasters are: 1) strong and elastic; 2) waterproof; 3) age resistant, following the requirements of unified European standards/guide books
• The application of paste-based renders is performed with a steel trowel with thickness equal to the diameter of biggest grain; it is rendered with a plastic trowel
• It is applied evenly from edge to edge (or inner corner) of the facade
• In order to prevent contingent defects, the weather conditions should be taken into consideration (direct sun light, rain, wind, humidity, low temperatures) while applying the plasters and during the first 2-3 days as well

 

Figure 15. Reinforced plaster priming (applied after the plaster has completely dried)

Figure 16. Applying (with steel trowel) and rendering (with plastic trowel) of a thin coat render