Rensair: cloud-connected air filtration
Brothers Christian and Frederik Hendriksen founded Rensair in 2020. Christian grew up with asthma, and their father, an HVAC engineer, designed and built a portable air purifier, which the brothers updated and patented. Rensair makes cloud-connected air filtration that works with existing HVAC systems; its patented Smart Demand Controlled Ventilation technology can cut building ventilation energy use by 40%.
Rensair raised $7m in a Series A led by Hoxton Ventures. The NHS was its biggest client during COVID, and it works with Welltower, one of the world’s largest senior living real estate investment trusts.
Number 13 on the Startups 100 Index 2026.
Register details are live from Companies House; descriptions and services are each company’s own.
Registered as RENSAIR LIMITEDCompany 12749725Activesince 17 July 2020· London
Role: Founders
Rensair makes cloud-connected air filtration that works with existing HVAC systems and can cut ventilation energy use by 40%.
Description from the company’s Startups 100 profile.