U-value

The U-value, or overall heat transfer coefficient, shows how well a building product conducts heat: the rate of heat transfer through a wall, floor or window, over a given area, under standard conditions. A lower U-value means slower heat flow and better insulation.

The page said Batty timber windows are hand finished, and that a low U-value rating comes from factory finishing. It claimed installing them improves energy efficiency, reduces carbon emissions and reduces energy costs, and invited people to call the team for a savings calculation.

Sustainability

The page argued timber windows and doors offer strong energy and sustainability ratings because timber is renewable, and said the factory uses little carbon emission compared with competitors. With maintenance, it said timber windows can last a lifetime and do not fade the way other materials can.

Related project, from the Scalby Lodge case study: traditional box sliding sash, stormproof casement and Yorkshire sliders designed to a U-value of 1.4, against a Building Regulations figure of 1.6 quoted on the site.