"This is a calculation of the proportion of total window area which is double or triple glazed. This should include any windows which have permanent secondary glazing fitted, temporary secondary glazing, such as removable secondary glazing or cling film, should be discounted from this calculation.""The new rules will force landlords to upgrade the energy efficiency of hundreds of thousands of homes currently rated F and G to a minimum of E by 1 April 2018 - or face being unable to let them until they improve the rating," added James. Secondary glazing is a tried and tested solution for properties, many period or Listed, looking to insulate against rising energy bills, especially pertinent given that anywhere between 15 and 25% of heat is lost through windows in single glazed dwellings. "That could equate to around a 25% cut in quarterly, like-for-like, energy bills. It frequently does," explained John Feely, a founding director of Ecoease, "In fact many secondary glazing customers report higher reductions." "We are developing a hinged version that adheres to EPC recommendations and we're already seeing interest from landlords particularly within urban environments." "When you're looking for proven environmental performance and an almost immediate and very measurable return on investment, there's few better 'insulations' against the elements than secondary glazing," he added. Costing from around 15% of a typical double glazing installation, secondary glazing panels are generally manufactured from clear plastics such as acrylic, polycarbonate or PET, known as polyester and used in aircraft windows and pop bottles. In terms of independent fire tests PET comes out top. Currently only supplied by Ecoease, PET crystalises when burnt to act as a virtual fire retardant whilst other plastics act like firelighters and expel toxic fumes. Amy Biddell, Rural Practice Surveyor with Leicestershire-based chartered surveyors Mather Jamie, operates on behalf of the Harpur Crewe LLC and she outlined their approach. "The Estate properties are a combination of terraced, semi-detached and detached cottages and barn conversions. Many of the cottages on the Estate are believed to have been built in the 1800s." "We currently have around 95% occupancy as we are in the process of refurbishing several cottages which have recently been vacated." "Due to the number of residential properties on the Estate we have decided to start the programme of energy improvements ahead of the 2018 EPC changes." The Harpur Crewe LLC’s aim is to also provide a better, more thermally efficient standard of accommodation to new and existing tenants in the hope of reducing tenants energy bills. "Installing secondary glazing is an easy way to improve the thermal efficiency of a property without causing much upheaval for residing tenants." Ecoease is not only easier to install than glass secondary glazing, it is also significantly cheaper and we have also been advised by our EPC assessor that it is more thermally efficient than glass. "A full time Clerk of Works, employed on the Estate, fits the Ecoease glazing within the Estate cottages and can usually install within an entire property in one to two days." "As well as installing secondary glazing the LLC is also incorporating loft insulation, upgrading heating systems, boilers and low energy lighting. "The Harpur Crewe LLC strives to provide a good standard of properties for its tenants and is always looking for new ways and products like Ecoease to assist in achieving this. The Estate owners view the new EPC regulations as a good way to improve the cottages for the benefit of their tenants to a bench mark standard." "The Ecoease secondary glazing has had a positive impact on the energy performance of the Estate Cottages and in many cases, along with loft insulation and low energy light, has enabled us to move many properties EPC ratings into band E and above," concluded Amy.