Airtight seals form the zipper of a building

AIRtight RENOVATION: not invasive, but energy efficient

Worldwide has begun a "major rebuild" to meet the sustainability goals of the Paris Climate Agreement. An important agreement is that by 2050 as many as 7 million Dutch homes and 1 million buildings must be rid of natural gas. In accordance with the "trias energetica," we must insulate our homes in such a way that the demand for heat is reduced to a minimum. The remaining heat demand must also be generated as sustainably as possible. As a first step, 1.5 million existing homes must be made sustainable by 2030. Airtight renovation plays a key role in this, as the measures are not only easy to implement, but also pay for themselves very quickly. Both in terms of cost and comfort.

Nick Haring, business developer at Bostik, likes to compare airtight renovation to putting on a good ski jacket. "The well-insulating lining of a ski jacket is both airtight and breathable," he explains. "This allows excess body moisture to be discharged in a controlled manner. A function that only works well when the jacket's zipper is closed. If the zipper is open, you immediately experience annoying and cold drafts and lose unnecessary heat. A well-insulated building envelope works exactly the same way, with airtight seals forming the zipper. Precisely this zipper is one of Bostik's specializations."

Seals unwanted cracks and seams

Bostik's Zwaluw® Airtight Building product range is all about creating a durable and efficient zipper seal, he says. "With our products, all unwanted gaps and seams in a home or building can be sealed, with the aim of preventing uncontrolled airflow. Thanks to the right measures, cold outside air can no longer enter our warm rooms undesirably, preventing cold and draft complaints. Also, no more unwanted heat is lost from the inside to the outside, resulting in substantial savings on energy bills and increasing thermal comfort. Good functional connections and a watertight barrier on the outside of the building also prevent vapor or moisture from entering the structure. As an added bonus, insulating measures keep out noise from outside to inside."

Airtight solutions

Each liter of air leakage costs approximately 1 m³ gas per year, Herring knows. "There are three places in a home where the risk of air leaks is greatest: the floor, the window frames and the roof. That's why it makes sense to address these places first." This approach is best started with a thorough inventory. "Airtight renovation always involves customization. It is necessary to examine which measures can be implemented practically, effectively and with minimal structural modifications for each house. Bostik can support this with an extensive site survey. We also have specific airtight solutions available for each detail of the house. For more information about airtight renovation, an extensive whitepaper can be found on our website."

Facade

A compression band makes the joint between the frame and the wall impact rainproof. This keeps the primary water load out as much as possible. "A compression band is breathable, so any moisture does get out and does not accumulate in the structure," Haring said. "With pre-cast concrete and masonry, expansion and connection joints occur. You finish these joints with a hybrid sealant, which stops the primary water load. To achieve the right ratio of joint depth to joint width, you can use a back filler."

Floor and roof

For airtight, waterproof and vapor-open connections between facade elements and support structures, Bostik offers airtight self-adhesive tapes. "These technical tapes are airtight and vapor-impermeable for the interior, while the exterior grade is both airtight, vapor-open and watertight," said Haring. "You seal the wall plate by using a flexible PUR on two sides. On the inside you finish this PUR with a Zwaluw Hybriseal® 306 coating." 

You can also use flexible PUR foam or a good compression tape in the ridge connection. "For the roof/wall connection, an Airtight Tape Interior is additionally used. This tape is airtight and vapor-inhibiting and can be plastered over well, without primers. A polyurethane foam (PU foam) is suitable for air sealing and thermal insulation of joints around window frames and building structures among themselves, such as the joint between ceiling and wall."

Frame frames

The airtight sealing of a structural frame can be done in several ways, says Haring. "The gap between the structural frame and the structure can be filled with Zwaluw Elast-O-Foam to repair the insulation break. This flexible PUR foam also provides noise reduction on the frame. Then there are several options for a good air seal, such as Zwaluw Hybriseal® 306 coating, Zwaluw Airtight Tape (vapor-open for the outside) or Zwaluw Airtight Tape Interior (vapor-inhibiting for the inside). For complex window frames like sliding doors there is the airtight, vapor-open, waterproof and thermally insulating Zwaluw Airtight Foam Tape. With these products you make joints easily impact rainproof and cold air can no longer enter warm living spaces."

Glazing

Herring recommends that the joints between the windows and frames also be sealed airtight. For example, with a hybrid sealant. "This prevents cold air from accessing the warm rooms and allows for even more comfortable, pleasant and energy-efficient living."