Why the duct repair method matters

Airtightness, OVK, indoor air quality and circular economy – all in one decision

An HVAC duct is not just a technical pathway for air. It determines indoor air quality, energy efficiency and the scope of an entire renovation project. When a duct leaks or loses its airtightness, the consequences ripple from the system into the entire property – and the project budget.

The topic is especially relevant in Sweden, where OVK inspections (obligatorisk ventilationskontroll) assess not only ventilation performance and indoor climate adequacy, but also opportunities to improve energy efficiency. OVK approval is mandatory – and it cannot be obtained if the ductwork leaks and pressure and airflows are not in order.

A leak never stays in one place

A leaking duct system is a chain reaction. Pressure losses disrupt ventilation balance, force fans into overdrive and increase energy consumption – all while indoor air quality deteriorates. Leaking systems typically lose 15–30% of their airflow, which is reflected directly in both energy bills and indoor air quality.

These are exactly the practical problems – leaking ductwork, pressure losses, compromised indoor air and energy waste – that come up repeatedly in client discussions. The same logic is confirmed by official energy efficiency sources: poorly sealed ducts directly increase both energy costs and system malfunctions.

The most challenging sites require the smartest approach

The most demanding situations in renovation are never straightforward. Problems accumulate in tight spaces, horizontal duct runs, varying duct sizes and aging structures where demolition is not only a technical but also a financial and logistical challenge.

Particularly challenging sites include older buildings where HVAC ducts may contain asbestos. According to the WHO, the exposure risk persists for decades after the original installation. In these cases, the choice of repair method is also a workplace safety decision. TKR’s sealing compound has been tested and approved as an encapsulation layer against asbestos, among other hazards, enabling safe repair without demolition or full-scale remediation.

Cost efficiency that shows in the project budget

Internal duct sealing is an investment that pays for itself quickly. The cost of sealing is typically SEK 300,000–900,000, compared to SEK 1.5–4 million for complete duct replacement – a saving of up to 75%.

In addition, a sealed system generates estimated energy savings of SEK 50,000–150,000 per year, as lost airflow is brought back under control and fans can operate at their designed capacity. The method is non-invasive: it requires no cutting, no penetrations and no temporary relocation of residents.

✅ Sealing SEK 300–900k vs. replacement SEK 1.5–4M – savings up to 75%
✅ Energy savings SEK 50–150k per year
✅ No demolition, no penetrations, no resident relocation
✅ Bio-based, odourless and non-allergenic sealing compound

The repair method is a circular economy decision

The top principle in the Swedish Environmental Protection Agency’s waste hierarchy is clear: waste generation must be prevented above all else. Only after that come reuse, recycling and other recovery. The agency also emphasises that waste prevention reduces not only waste volumes but also the resource needs and emissions associated with manufacturing new products.

This is why extending the lifecycle of existing ductwork is, in many cases, the most responsible and cost-effective starting point – before resorting to demolition and rebuilding.

TKR’s perspective: seal first, replace only when necessary

TKR’s message is clear: an HVAC duct should not be viewed as the first component to demolish, but as a structure whose condition, airtightness and continued use should be carefully evaluated. The TKR system restores duct airtightness internally using a bio-based, odourless and non-allergenic sealing compound. The method covers the entire system – from ducts to intake chambers and fan rooms.

Approved OVK, energy savings, reduced disruption to occupants, lifecycle extension and better manageability in challenging sites – these are tangible benefits that are reflected in both the project budget and the quality of the end result.

TKR system’s Swedish partners: distribution is handled by AB Bioteknik & Ytbehandling and installations by Fluetec AB, ensuring local expertise and availability.

Nordbygg 2026: the right place for the right conversation

Nordbygg brings together exactly the professionals whose work involves HVAC duct repair decisions: property owners, facility managers, maintenance professionals, installers and project managers. These are the people making decisions where duct performance, OVK compliance, energy efficiency and sustainability matter.

The next time someone talks about an HVAC duct, it’s not just about the duct. It’s about OVK approval, indoor air quality, energy, building usability, renovation project management, demolition waste volumes and how far the lifecycle of an existing structure can reasonably be extended.

This is exactly what we are coming to discuss at the event.

What? Nordbygg 2026 – the largest construction and property industry trade fair in the Nordics
Where? Stockholm, Sweden
When? 21–24 April 2026

More information about the event: nordbygg.se

Come meet us at Nordbygg 2026 in Stockholm, 21–24 April. Let’s discuss what internal duct sealing could mean for your specific project.