A landlord managing a period property, or a portfolio of them, faces a specific problem that owner-occupiers don’t. The property has to meet a minimum EPC rating to remain legally lettable, but the windows that are dragging that rating down are often original, sometimes listed, and rarely something a tenant or a conservation officer will accept being ripped out and replaced.
Secondary glazing addresses the EPC problem directly, without touching the primary window at all.
The Regulatory Pressure on Rented Property
The Minimum Energy Efficiency Standards (MEES) set the baseline EPC rating a residential or commercial property must achieve to be legally let. That baseline has tightened over recent years and is set to tighten further, with government policy signalling EPC Band C as the direction of travel for the rented sector, alongside the 2030 EPC targets already in place for social housing, covered in more detail in our guide to social housing energy efficiency and EPC compliance.
For landlords holding period stock, particularly Victorian, Georgian, or Edwardian properties with single-glazed sash or casement windows, the windows are frequently the largest single factor holding the EPC rating below the required band. Replacing them with new double glazing is the obvious response, and often the wrong one, for reasons that go beyond cost.
Why Window Replacement Isn’t Always an Option
Three constraints commonly rule out full window replacement for rented property:
Listed building or conservation area status. A significant proportion of the UK’s period rental stock sits within a conservation area or carries listed building status, where Listed Building Consent is required before original windows can be altered or replaced, and such consent is frequently refused where the windows contribute to the building’s character.
Cost across a portfolio. Replacing sash or casement windows across multiple units is a substantially larger capital outlay than fitting secondary glazing to the same windows, and the return on that additional spend, in EPC terms, is not proportionally larger.
Tenant disruption and voids. Window replacement is invasive, dusty work that typically requires the property to be vacant, creating a void period landlords cannot easily absorb across a portfolio on rolling tenancies.
How Secondary Glazing Improves EPC Rating
Secondary glazing adds an independent glazed layer behind the existing window, improving the thermal performance of the opening as a whole without altering or removing the original glass and frame. Granada’s Horizontal Sliding system, specified with 4mm Low-E glass and an 80mm air gap, achieves a U-value of 1.5 W/m²K, a substantial uplift from the U-values typical of single-glazed period windows. See our U-values guide for a full comparison across the range.
That uplift in U-value feeds directly into the SAP calculation behind the EPC assessment, moving the property toward, and often across, the band threshold that determines legal lettability.
Installation is markedly less disruptive than a window replacement. Secondary glazing fits from inside the room, over one to two days per property depending on the number of windows, without removing the original window or requiring extended access to the property’s exterior. For landlords managing tenanted stock, this reduces the void period to a fraction of what a full window replacement would require.
Specifying for Multiple Units
Landlords with several properties of similar construction, a terrace of Victorian houses, for example, benefit from a standardised specification across the portfolio rather than a bespoke quote per property. Horizontal Sliding and Balanced Vertical Slider cover the great majority of period sash and casement window configurations, with sizes up to 4,934mm wide (Horizontal Sliding) and 3,325mm tall (Balanced Vertical Slider), which accommodates the standard window dimensions found across most Victorian and Edwardian housing stock.
Granada’s trade partner network, covering 500-plus installers across the UK, supports landlords managing property outside their immediate area, with the online price generator giving an indicative cost per window before a formal survey is arranged.
A Note on Listed and Heritage Rental Property
For landlords holding listed rental stock specifically, secondary glazing carries an additional advantage beyond EPC improvement. Because the intervention is non-invasive and fully reversible, it is generally treated by conservation officers as compliant with Historic England guidance in a way that window replacement rarely is, removing the planning uncertainty that otherwise stalls EPC improvement work on listed rental property. See our guide to secondary glazing in conservation areas for the planning detail.
Frequently Asked Questions
Can secondary glazing alone move a property from EPC band D to C? Windows are one factor within the wider SAP calculation, alongside insulation, heating system, and other elements, so the exact impact depends on the property’s overall specification. For properties where windows are a significant contributing factor, the thermal improvement secondary glazing delivers can be a substantial part of closing that gap.
Is secondary glazing cheaper than window replacement across a portfolio? Generally, yes, both in the direct product and installation cost, and in the reduced void period compared with a full window replacement programme.
Do tenants need to move out during installation? No. Secondary glazing is fitted from inside the property without removing the original window, and most installations across a typical property complete within one to two days.
Does secondary glazing require planning permission on a listed rental property? Secondary glazing is generally treated as reversible and non-invasive, which typically places it outside the scope of Listed Building Consent, though this should be confirmed with the relevant conservation officer for the specific property.
What EPC improvement can secondary glazing typically deliver? The specific EPC point improvement depends on the property’s existing specification and the secondary glazing product and glass chosen. Granada’s Energy Saving Calculator provides an indicative estimate based on individual property details
