Glow-worm prides itself in the manufacture of a wide range of user-friendly domestic heating appliances, which have been built with the typical UK home in mind to support the demands of our modern lifestyles. Glow-worm is the sister brand of the leading internationally renowned Vaillant Group. Both Vaillant and Glow Worm Boilers come highly recommended by both installers and home users alike, and when combined they form the most top rated condensing boiler manufacturer of the UK.