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Energy Efficiency & Ventilation

Energy Efficient uPVC Sash Windows

In the pursuit of a more energy-efficient home, the choice of windows and their energy efficiency rating plays a crucial role. Traditional sash windows were historically made with single panes of glass that provide a very poor insulation, making them the main cause of heat loss.

The energy efficiency of a window can be classified in two ways: WER energy ratings and u-values.

energy rating A sash windows
a rated sash windows standard

A Rated Sash Windows As Standard

WER energy ratings are very similar to the energy ratings you see on electrical appliances. It’s an A to E scale, with A providing the best performance and E the worst. U-values provide a specific measure for the efficiency of a window and are given as a number. The lower the number, the better the energy efficiency. U-values are particularly important for new builds and extensions, as they are specified as part of building regulations.

Using the latest technology and manufacturing methods, Rose Collection sash windows come A rated as standard, providing a significant improvement to the energy efficiency of your home. This increase in window performance will reduce your overall heating bills in the winter whilst also helping to keep your home cool in the summer. The standard u-value of any Rose Collection is 1.5 W/m2k, although this can be improved to 1.4 W/m2k with an optional upgrade to the glass.

Achieve U-Values As Low 1.2 with ThermoVFlex

Until recently, the only way to reduce the u-value of a sash window below 1.4 W/m2k was by using triple glazing or vacuum glass. Both methods come with serious limitations, including high costs and limited practicality in their choice of glass options and design options, such as astragal bars.


ThermoVFlex - thermal sash windows insulation
ultra modern energy efficient windows

Ultra Modern Energy Efficient Windows

Ultimate Rose & Heritage Rose sash windows can now achieve a certified 1.2 W/m2k u-value with our latest innovation: ThermoVFlex. This patented technology improves the window’s u-value through profile enhancements, rather than relying on specialised glass. This optional upgrade is far more cost-effective than triple or vacuum glazing and overcomes all of their limitations. Best of all, visually ThermoVFlex has no effect whatsoever on the window, so you still get all the authentic charm of Rose Collection sash windows but with ultra-modern energy efficiency built-in.

Trickle Vent Regulations

In 2022 significant changes were made to building regulations via Approved Document F: Ventilation. These changes required an increase to passive ventilation that flows through a property, both on new and replacement windows. Effectively this means that most window replacement projects must include trickle vents unless an alternative approved method is in place (e.g. mechanical ventilation).

Eclipse trickle vents sash windows
home renovation ideas in 2024

Remain Authentic with The Rose Collection's Trickle Vents

Adding trickle vents can seem like a hinderance to the charming aesthetics of a traditional sash window. That is why The Rose Collection provides multiple options when a trickle vent is required. The best option to maintaining the look of your heritage windows is with our Eclipse trickle vent system. Eclipse is a full width vent cover that can matched to the same foil finish as the window, completely masking the presence of a trickle vent from the outside.

Trickle Vent Options


Eclipse trickle vents sash windows



overhead trickle vent on sashes



trickle vent in sash window frames



trickle vent in sash windows