Insulation techniques have been developed to make new and existing buildings more thermally efficient. Building structures have modern insulation applied to either internal or external walls to ensure they retain heat longer and achieve very good thermal values. Tim Smith from DuPont discusses how airtightness is integral to improving thermal efficiency.

The need to create more energy efficient buildings is forcing designers to develop a more holistic approach in order to achieve increasingly stringent targets. As we progress into the future with greater energy efficient and sustainable building methods we are becoming increasingly aware of the risk of air leakage.

Not only is the improvement in insulation values important, but so too is the airtightness performance. Heat loss by convection isn’t something that is highlighted in u-value calculations, but is a significant cause of energy loss and carbon emissions. By limiting this leakage from buildings it is possible to reduce energy consumption and costs.

The full capability of an insulation layer is only achieved when it is efficiently sealed and it has been proven that air leakage can account for nearly half of all heat loss in new constructions. The energy efficiency of a building can be significantly improved by making the inside of the construction airtight and vapour resistant.

Uncontrolled air leakage occurs through gaps and between insulation and hairline cracks in various linings within the wall and roof constructions. These generally occur when the building is drying out, but can also be caused by settlement and thermal movement during the lifetime of the building. Any layer in the building envelope where total continuity is not achieved is a potential weak point.

Air and vapour control layers (AVCLs) suitable for roofs, walls and floors not only help reduce convective heat loss but also provide highly engineered vapour control for breathing systems. By improving insulation values, the internal temperatures of constructions have increased thereby increasing the amount of moisture held in the habitable space. Thus a barrier is required not only to protect the performance of the insulation, but also to provide management for the movement of moisture through the building envelope.

When installed continuously with all laps and penetrations sealed, an AVCL will provide effective condensation control and airtightness for all building types. With an ever increasing requirement to conserve energy the portfolio of DuPont Tyvek products can help you to achieve these environmental goals in an economical way.

A correctly sealed installation will keep the insulation and wall structure dry from internally generated humidity and can help to reduce energy consumption. On top of choosing the right AVCL it is important to make the building envelope airtight and windtight by sealing gaps between and around insulation layers, AVCLs and breather membranes.

A windtight and watertight breather membrane is another element of crucial importance in a building envelope as it avoids water infiltration from outside and allows evaporation of eventual trapped humidity.

The adhesive tapes are specially designed for use with membranes to help reduce uncontrolled air leakage. The complete system works best when incorporated with an internal ventilation regime that allows a controlled flow of air into and out of the building thereby maintaining internal temperature in summer and winter and reducing energy costs and so the construction will adhere to the ‘build tight, ventilate right’ principle and guarantee long term durability.

As building systems develop as with designers, contractors need to offer their clients a holistic approach offering the right products, skill sets and a more detailed understanding that guarantees a robust installation designed to achieve the airtightness and moisture control required for any particular construction.

By taking ownership of the airtightness layer the contractor becomes the controlling partner in the build-up of the building envelope and starts to control other trades on site who could potentially damage the airtight membrane. By so doing the contractor’s importance, influence and potential for new and repeat business improves.

Tim Smith
DuPont Building Innovations