Bay Window Insulation

Bay windows are widely considered the weak point in a home's thermal envelope, often responsible for up to 50% of a room's total heat loss. Because they project outward, they act like a 'radiator in reverse,' draining warmth through thin walls and uninsulated roofs. This rapid heat loss creates dangerously cold internal surfaces where warm air condenses, often leading to severe damp and outbreaks of toxic black spot mould.

Retrofitting these areas with insulation boards creates an immediate thermal barrier that stops the cold penetrating the structure. When finished with a spray cork coating, the benefits are amplified: cork's natural elasticity prevents the cracking commonly seen on bay window render, while its breathability actively eliminates condensation. This combination eradicates the conditions that mould needs to grow, transforming a freezing, damp bay into a warm, healthy feature that lowers heating bills and protects the building fabric.

Applying spray cork to a bay window is a highly effective, space-saving solution for addressing the common issues of freezing cold temperatures, black mold, and dampness, particularly in older 1920s–1940s homes. As a thin internal wall insulation (TIWI), it is applied directly to interior walls or window reveals to create a seamless, breathable, and insulating barrier. 

Key Benefits for Bay Windows

• Drastic Temperature Rise: Reports indicate that internal surface temperatures on cold bay window walls can rise significantly, such as from 11°C to 19°C, immediately improving room comfort.

• Condensation & Mold Control: The material is breathable and helps regulate moisture, preventing the return of black mold by eliminating cold bridging.

• Space Saving: At a thickness of only 5-6mm, it provides insulation without significantly reducing the size of the room.

• Versatile Application: It can be applied directly to plasterboard, plaster, or masonry around the window reveals.

• Finish Options: After the spray cork is applied, it can be skimmed with 2mm of standard gypsum plaster to create a smooth, paintable surface. 

Application and Performance

• Installation: Typically applied in two layers, it covers gaps that traditional insulation might miss, especially in complex corner areas of a bay.

• Durability: The coating is durable, with a 25-year warranty offered by some, such as CorkSol approved applicators.

• Efficiency: It offers a 30% reduction in heat loss, helping to lower energy bills.

• Cost: While offering high performance, it can be more expensive than some traditional materials.