It cannot be simply said which one is better, because they are two different types of building materials with different natures and parts, playing different roles in the building insulation system.
The fundamental difference between function and position
Insulating glass curtain wall: It is the exterior envelope structure of a building, equivalent to the "skin" of the building. Its main functions are lighting, visibility, ventilation (if it can be turned on), and isolation from the outdoor environment (such as wind, rain, noise, and heat). Insulation is just one of its many functions.
Insulation board: It is an insulation material attached to the walls of buildings (such as concrete walls and block walls), equivalent to putting on a "down jacket" for the building. Its core and primary function is thermal insulation and heat preservation, followed by waterproofing and protection of the main structure, etc.
Performance analysis
From the perspective of the insulation capacity of the material itself: the thermal conductivity (λ value) of the insulation board is much lower than that of glass. This means that, at the same thickness, the insulation board has a much stronger ability to prevent heat transfer than glass.
From the perspective of the overall insulation performance of the components: For an exterior wall that adopts insulation boards, its overall heat transfer coefficient (K value) can easily reach 0.5 W/(m²·K) or even lower. Even for the current highest-performance glass curtain walls, its K value is hard to remain stably below 0.5. Therefore, the insulation performance of a complete insulated wall is usually better than that of a high-performance glass curtain wall.
Systematic Thinking: The "Barrel Effect"
The insulation performance of a building does not depend on its best part, but on its weakest part (the short plank of a wooden barrel).
The "shortcomings" of glass curtain walls:
The frame material: The metal frame (aluminum profile) of the glass curtain wall is a "thermal bridge", with extremely strong heat conduction performance, which will greatly reduce the insulation performance of the entire curtain wall system. Even with the "broken bridge insulation" technology, it cannot be completely eliminated.
Edge sealing: The edge sealing strip of insulated glass is also a relatively weak link.
The "shortcomings" of insulated walls:
The main aspect is the installation process, such as thermal Bridges of fasteners and splicing gaps, but the overall controllability is relatively high.
Conclusion and Summary
Different roles, irreplaceable: The insulated glass curtain wall is for lighting and viewing, while also taking into account insulation. The insulation board is for pure insulation. In architectural design, they are not an either-or relationship but rather complement each other.
Thermal insulation performance per unit area: Under the same area, a complete solid exterior wall with insulation boards usually has better thermal insulation performance than a high-performance insulating glass curtain wall.
Practical application: In modern energy-efficient buildings, the correct approach is:
In areas that require lighting and visibility, high-performance insulating glass curtain walls with the best possible thermal insulation performance (such as Low-E insulating glass, argon-filled glass, etc.) should be used.
For the solid wall sections that do not require lighting, wrap them with high-efficiency thick insulation boards.
The ultimate goal is to ensure that the insulation performance of the entire building's exterior envelope (including Windows, walls, and roofs) reaches a very high and balanced level, avoiding obvious "thermal defects".
So, next time you can understand it this way: Insulation boards are professional "thermal underwear", while insulated glass curtain walls are "windproof coats" that are both beautiful and have certain thermal insulation functions. To keep a building warm as a whole, both are needed, but the basic insulation function of "thermal underwear" is more fundamental and important.
