Do Air Gaps Impact Insulation Performance Significantly?

Air Gap Impact on Insulation Performance

Air gaps can have a substantial impact on the thermal performance of insulation materials. When air gaps are present, they can reduce the thermal resistance of the insulation, allowing heat to transfer more easily. This is because air is a poor insulator, with a thermal conductivity of around 0.025 W/mK, compared to materials like sheep wool (0.035 W/mK) and hemp (0.040 W/mK).

Best Practices for Minimizing Air Gaps

To minimize the impact of air gaps on insulation performance, it’s essential to ensure a continuous layer of insulation material. This can be achieved by using a spray foam or liquid insulation to fill gaps and voids, or by installing a continuous layer of insulation material, such as cellulose or straw, that is designed to fit snugly into the space. A general rule of thumb is to maintain a maximum of 1 cm (0.4 inches) of air gap between insulation layers. For example, when installing a layer of 10 cm (4 inches) of straw insulation, it’s recommended to use a 9 cm (3.5 inches) thick layer of insulation material to minimize air gaps.

Material Selection for Air Gap Reduction

When selecting insulation materials, consider those with natural fibers that are designed to minimize air gaps. Materials like cork and hemp are often used in combination with other insulation materials to provide a high level of thermal resistance while minimizing air gaps. These materials have a higher density than other insulation materials, which helps to reduce air gaps and improve overall thermal performance. For example, a 10 cm (4 inches) thick layer of hemp insulation with a density of 100 kg/m3 can provide a thermal resistance of up to 20 m²K/W, compared to 15 m²K/W for a similar layer of straw insulation with a density of 50 kg/m3.