Understanding exterior wall insulation: 3 Forms, 3 Systems, and 6 Core Materials, Summarized Perfectly!

Setting the insulation layer on the outside of the building's exterior wall forms a composite structure of "exterior wall + insulation layer + decorative layer."

(1) Advantages

Excellent thermal insulation: The insulation layer covers the entire exterior wall, effectively blocking thermal bridges (such as beams and columns) to prevent heat loss, reducing indoor and outdoor heat exchange, and achieving high energy efficiency.

Protect the main structure: The insulation layer is located on the outside, which can isolate the direct impact of external temperature changes and rain and snow erosion on the wall, thereby extending the building's lifespan.

Does not occupy indoor space: The insulation layer is on the outside of the wall, which does not compress the indoor usable area, making it especially suitable for small apartments.

Improve the indoor thermal environment: Ensure uniform indoor temperature distribution to avoid local low-temperature issues caused by "thermal bridges" commonly found in internal insulation.

(2) Disadvantages

The construction difficulty is relatively high: it requires high-altitude operations and has strict requirements for construction techniques and processes (such as insulation layer adhesion, anchoring, crack resistance treatment, etc.), resulting in relatively high costs.

Susceptible to external environmental influences: Long-term exposure may lead to cracking and detachment due to material aging and thermal expansion and contraction. Later maintenance requires high-altitude operations, which are costly.

The thickness of the insulation layer (usually 5-10cm) may alter the original facade design of the building, and needs to be coordinated with the decorative layer for unified planning.

(1) Advantages

Easy construction: No need for high-altitude work, can be done indoors, with a short construction period and low cost, suitable for renovation of existing buildings (such as old house refurbishments).

No impact on building appearance: does not alter the original structure and facade design of the exterior walls, suitable for historic buildings or buildings with strict appearance restrictions.

Easy maintenance: In case of issues, repairs can be conducted indoors without the need for external scaffolding.

(2) Disadvantages

Poor insulation effect: Thermal bridges (such as the connections between walls and floors, beams, and columns) cannot be completely blocked, leading to localized heat loss, and may cause wall condensation and mold in winter.

Occupying indoor space: The thickness of the insulation layer (usually 3-8 cm) can reduce the usable indoor area, affecting furniture placement and space layout.

Temperature difference cracks are likely to occur: The temperature difference between indoor and outdoor can cause deformation cracks between the wall and the insulation layer, affecting aesthetics and durability.

Affect interior decoration: Decorative treatment is required on the surface of the insulation layer (such as tiling, painting), which may limit the style of decoration.

(1) Advantages

Insulation combined with structure: The insulation layer is wrapped by wall materials, providing good protection and strong durability, suitable for the integrated design of new buildings.

Reducing thermal bridge impact: The insulation layer is continuously distributed within the wall, which can partially block the thermal bridge. Its insulation performance is between external insulation and internal insulation.

High construction efficiency: Can be achieved through prefabricated wall panels or on-site casting, suitable for industrial construction.

(2) Disadvantages

Increased wall thickness: requires inner and outer layers of wall materials plus insulation layer, resulting in a larger wall thickness that may reduce the building's usable area.

The insulation layer is prone to moisture: if not properly sealed during construction, moisture can easily enter the insulation layer, leading to dampness, reduced insulation performance, and difficult repairs (requiring wall dismantling).

High construction precision is required: internal and external wall materials need to be constructed simultaneously. If the joints are not tight, it can easily lead to thermal bridges and structural issues.

Limited applicability: Mainly used for new buildings, difficult and costly to retrofit existing buildings.

Considering factors such as construction cost and thermal insulation performance, the main form of exterior wall insulation currently is external wall insulation.

The core definition is an exterior wall insulation system with an anti-crack mortar layer thickness of 3-7mm. The most common types are rock wool board thin plaster exterior wall insulation system and expanded polystyrene (EPS) thin plaster insulation system. It consists of a polymer adhesive layer, a board-type insulation layer, a thin anti-crack mortar layer, and a finish coating. The insulation board is fixed to the base wall (concrete or masonry structure, which needs to be smooth, clean, and free from hollowing and looseness) using adhesive. The thin plaster layer should be fully covered with alkali-resistant coated fiberglass mesh to enhance crack resistance and impact resistance. This system features thermal insulation, fire resistance, and easy construction, and is widely used in energy-saving renovation and new construction projects of various residential and industrial buildings.

The fire resistance rating of the material is determined by the nature of the board.

Exterior wall insulation thin plaster system

By using prefabricated insulation formwork as the outer mold for cast-in-place concrete exterior walls, a permanent composite insulation layer is formed with the structural wall after pouring, providing both structural load-bearing and thermal insulation functions. The insulation formwork is completed simultaneously with the cast-in-place concrete as the outer formwork, reducing construction procedures, shortening the construction period, and avoiding the risk of insulation layer detachment later. The insulation layer and the wall form an integral structure through concrete interlocking and mechanical anchoring (some systems have connectors), offering better wind resistance and seismic performance than traditional adhesive insulation methods.

The system uses an integrated design of "structure-insulation-protection" to address the issue of the lifespan mismatch between traditional external insulation and the wall. This is an important development direction in recent years for building energy conservation and structural integration technology.

The insulation materials include extruded polystyrene board (XPS), expanded polystyrene board (EPS), graphite polystyrene board (SEPS), rigid polyurethane foam (PIR), rock wool, etc. The fire rating can be determined according to the insulation core material.

Composite External Formwork Cast-in-Place Concrete Insulation System

Insulation and decoration integrated board insulation system

Rock wool board

EPS molded polystyrene board

XPS extruded polystyrene board is a rigid foam plastic board manufactured using polystyrene resin as the main raw material, supplemented with other additives and polymers, heated and mixed while injecting a catalyst, and then extruded and molded. It features a closed-cell honeycomb structure, high density, and uniform voids. Its thermal conductivity is 0.028-0.034W/(m·K), with a density of 30-35kg/m³, and it is classified as B-level fireproof.

XPS extruded polystyrene board

SXPS Graphite Extruded Polystyrene Board

SEPS Graphite Molded Polystyrene Board

Graphene thermal insulation non-combustible board