The best insulation for keeping walls thin while maintaining high thermal efficiency is typically high-performance rigid foam insulation. Rigid foam insulation offers excellent thermal resistance (high R-value) relative to its thickness, allowing for more efficient insulation in thinner wall assemblies. It comes in different types, with some of the most commonly used ones being:
Extruded Polystyrene (XPS): XPS insulation has a closed-cell structure that provides good moisture resistance and a high R-value per inch of thickness. It's commonly used in various building applications, including walls.
Polyisocyanurate (Polyiso): Polyiso insulation is known for its high R-value per inch, making it one of the most efficient insulation materials available. It's often used in commercial and residential construction to meet demanding energy codes.
Expanded Polystyrene (EPS): EPS insulation is lightweight and has a lower cost compared to XPS and polyiso. It has a good R-value per inch and is commonly used in walls, roofs, and foundations.
Vacuum Insulation Panels (VIP): VIPs are extremely thin and have an exceptionally high R-value. However, they are relatively expensive and are usually reserved for special applications or where space is a premium.
The choice of insulation material will depend on various factors, including your budget, local building codes, moisture conditions, and specific insulation requirements. Each type of rigid foam insulation has its advantages and limitations, so it's essential to consult with a professional architect, builder, or insulation expert to determine the best option for your particular project.
Additionally, keep in mind that while thinner walls can be achieved with high-performance insulation, there are other considerations related to building design, such as structural integrity and soundproofing, that may influence the overall wall thickness. Working with a knowledgeable team can help you strike the right balance between insulation performance, wall thickness, and other design requirements for your building project.