EPC Rating and Windows: What Landlords Need to Know for 2026

If you're a landlord with period properties in London, energy efficiency is climbing the agenda fast. The government is pushing towards tougher minimum EPC (Energy Performance Certificate) standards for rental properties—and windows are often the biggest obstacle to compliance.

For owners of listed buildings and properties in conservation areas, the challenge is particularly acute. You can't simply rip out your Georgian sash windows and install UPVC double glazing. So what are your options?

The EPC Rules: Where Things Actually Stand

Important clarification: There is no law requiring rental properties to reach EPC band C in 2026 or 2027. The current legal minimum under the Minimum Energy Efficiency Standard (MEES) remains band E for most privately rented homes in England and Wales. The government's stated direction of travel is a higher band C standard, with proposals pointing towards new tenancies around 2028 and all tenancies by 2030. Always check the latest official MEES landlord guidance for confirmed dates, as these timelines have shifted before.

So why plan now, if band C isn't law yet? Because the direction of travel is clear, installation schedules for heritage-appropriate work fill up quickly, and a property sitting at E or F today has a long way to travel. Getting ahead of the curve protects your rental income and avoids a scramble once dates are confirmed.

Currently, a large share of English homes have an EPC rating of D or below. Period properties with single-glazed windows are particularly affected—many sit at E, F, or even G ratings.

Penalties for breaching MEES matter too. The current maximum civil penalty is up to £5,000 per property, but the government has proposed raising this substantially—up to £30,000—alongside the tighter standards. Either way, non-compliance is a false economy once void periods and lost rent are taken into account.

Why Windows Matter for EPC Ratings

Windows are one of the largest contributors to heat loss in any building. In a typical period property:

• Single-glazed windows lose 2-3 times more heat than insulated walls
• Windows can account for 20-30% of total heat loss
• Draughty windows add to this with uncontrolled ventilation

An EPC assessor will specifically examine your glazing type, frame material, and window area. Single glazing with timber frames scores poorly; double glazing scores well. But what if you can't install double glazing?

Secondary Glazing and EPC Improvements

Here's the good news: secondary glazing is recognised by EPC assessors as an energy efficiency improvement. When properly installed, it can:

• Improve your EPC rating by 5-15 points
• Reduce window heat loss by up to 65%
• Eliminate draughts (uncontrolled ventilation)
• Be recorded as "secondary glazing" in the EPC methodology

For a property currently rated D (score 55-68), good-quality secondary glazing combined with other improvements can often push it into the C band (score 69-80).

The Listed Building Advantage

There's an important exemption that many landlords don't know about. Properties where energy efficiency improvements would "unacceptably alter the character or appearance" of a listed building or building in a conservation area may qualify for an exemption.

However, this exemption requires you to demonstrate that you've explored all reasonable alternatives. Installing secondary glazing shows you've taken action to improve efficiency while respecting heritage constraints—strengthening any exemption application.

In practice, secondary glazing often negates the need for an exemption entirely by achieving sufficient EPC improvement.

What EPC Assessors Look For

When an EPC assessor visits your property, they'll examine:

1. Glazing type: Single, double, triple, or secondary
2. Frame material: Timber, UPVC, aluminium, or composite
3. Window area: Percentage of wall area that is glazed
4. Draught-proofing: Evidence of sealed frames and openings

Secondary glazing ticks multiple boxes: it counts as an additional glazing layer, and properly installed units eliminate draughts completely.

Specification Matters

Not all secondary glazing will deliver the same EPC improvement. For maximum benefit:

• Use low-E glass: Low-emissivity coatings reflect heat back into the room
• Ensure airtight seals: Brushes and seals must be properly fitted
• Maximise air gap: Larger gaps (100mm+) improve thermal performance
• Cover the full window: Gaps around frames compromise performance

Cheap magnetic or removable secondary glazing may not deliver the same benefits as professionally installed units with proper sealing.

Cost vs. Penalty Analysis

Let's be practical about the numbers:

Secondary Glazing Investment

For a typical London flat with 6-8 windows:

• Standard secondary glazing: £2,500-£4,000
• Premium specification: £4,000-£6,500

Non-Compliance Penalties

• Current fine for letting below minimum standard: up to £5,000 per property (proposed to rise to £30,000)
• Lost rental income during void periods: Variable
• Reduced property value if unlettable: Significant

The investment in secondary glazing pays for itself many times over compared to the cost of non-compliance.

Additional Benefits for Landlords

Beyond EPC compliance, secondary glazing offers landlords several advantages:

• Reduced tenant complaints: Warmer, quieter properties retain tenants longer
• Lower maintenance: Original windows are protected from condensation damage
• Premium rents: Well-insulated period properties command higher rents
• Preserved character: Original features maintained for property value

Step 1: Start with the EPC, not the window quote

Before spending money, obtain the property's current EPC and look beyond the letter grade.

A property rated D 68 is in a very different position from one rated E 45. The first may need a carefully targeted package to reach C. The second is likely to require improvements across the wider building.

Ask your energy assessor or retrofit adviser to identify:

• The property's current SAP score and EPC band
• Whether the windows are recorded as single, double or secondary glazing
• Which recommendations offer the best improvement for your budget
• Whether the property has insulation, heating or ventilation weaknesses
• How much improvement is likely to come from glazing alone

For existing homes, EPCs generally use the Reduced Data Standard Assessment Procedure (RdSAP). Secondary glazing can be recorded within this assessment, meaning it may contribute to the property's score. The improvement still needs to be assessed accurately; it is not automatically worth a fixed number of points.

The UK Parliament's written answer on secondary glazing and EPCs confirms that secondary glazing is recognised in the assessment methodology.

For the wider picture on how glazing affects compliance, see our guide to EPC ratings and windows for landlords.

Your EPC is a roadmap, not just a certificate. Use it to understand where your property is leaking energy before commissioning work.

Step 2: Improve the whole thermal envelope

Windows matter, but they are only one part of the building's thermal envelope.

If the roof is losing heat like a colander holding water, upgrading the windows alone will not deliver the result you need. Before selecting glazing, check whether the property needs:

• Loft insulation top-up
• Cavity wall or internal insulation where suitable
• Draught-proofing around doors and floorboards
• Boiler controls or a programmable thermostat
• Thermostatic radiator valves
• Efficient lighting and hot-water controls
• Repairs to leaking gutters or damp-prone areas

This does not mean you need to carry out every measure at once. It means you should prioritise intelligently.

For many landlords, the sensible sequence is to address low-cost, high-impact improvements first, then use thermal efficiency secondary glazing to tackle the original windows that remain cold, draughty or inefficient.

Secondary glazing is particularly useful where single-glazed windows form a significant part of the heat-loss problem. The sealed internal pane and air gap reduce heat transfer, helping the inner surface stay warmer and making rooms feel less like they are being cooled from the outside in.

Comfort is part of the business case. Warmer rooms can mean fewer tenant complaints, less condensation and better retention between tenancies.

Step 3: Target the right windows with the right specification

You do not necessarily need to glaze every window to make a meaningful improvement.

Begin with the rooms where tenants feel the problem most intensely:

• Bedrooms with rattly sash windows
• Living rooms with large single-glazed bays
• Front rooms exposed to traffic noise
• Kitchens and bathrooms affected by condensation
• Windows above radiators or in particularly cold rooms

The best configuration depends on how each window opens and how the room is used.

Existing window or priority	Suitable secondary glazing approach	Landlord benefit
Traditional sash window	Bespoke vertical slider	Retains sash operation and heritage appearance
Wide casement or bay	Horizontal slider or multi-panel system	Covers larger openings with access retained
Rarely opened landing window	Fixed or lift-out panel	Slim, discreet and cost-conscious
Bedroom near a busy road	Acoustic laminate glazing	Reduces external noise as well as heat loss
Window requiring frequent ventilation	Hinged or sliding unit	Maintains practical day-to-day access

For thermal improvement, standard glass may be appropriate. Where noise is also affecting tenant comfort, an acoustic specification may be more suitable. A laminated pane with a PVB interlayer helps dampen sound energy; combined with a properly designed air gap, it can reduce the rhythmic cocktail of traffic, sirens and late-night deliveries.

Do not assume the thickest glass is automatically best. The air gap, frame design, seals and relationship between the original window and the new pane all matter.

Read more about secondary glazing types, or explore the specialist options available for sash windows.

Step 5: Choose experienced secondary glazing installers and reassess

A product only performs as well as its survey and installation.

Period windows are rarely perfectly square. Sash boxes can be uneven, reveals may vary from room to room and old joinery can contain decades of paint, movement and repairs. An off-the-shelf panel may leave gaps around the edges, compromise operation or look conspicuous.

Experienced secondary glazing installers should measure every opening individually and recommend a specification based on the window, the building and the tenant's needs.

As a broad 2026 guide, the secondary glazing cost guide gives indicative prices of:

• £300–£800 per window for standard units
• £600–£1,200 per window for acoustic laminate
• £1,000–£2,200 per window for heritage or grid-matched units

These are starting points, not a promise. Size, access, opening style, finish and heritage detailing all affect the final secondary glazing cost.

After the work is complete:

1. Keep the invoice and product specification.
2. Photograph the installed units if helpful.
3. Show the assessor which windows have been upgraded.
4. Request a new EPC if the improvement is material.
5. Review the remaining recommendations before committing to further work.

We like to be honest: secondary glazing will not rescue rotten or structurally failing frames. If the original timber is decayed, repair or restoration comes first. It may also not be enough to move a low-rated E property all the way to C without insulation or heating improvements.

But for a property with sound original windows, especially one sitting close to the next EPC band, it can be a cost-effective, low-disruption part of the solution.

Is secondary glazing cheaper than replacing windows?

Often, yes, particularly in a period property.

Window replacement can include manufacture, removal, disposal, making good plaster, redecorating and possible specialist joinery. Heritage-appropriate double glazing may also be considerably more expensive than a standard modern replacement.

Secondary glazing keeps the original window where it is. That reduces disruption and can preserve both the building's character and the tenant's daily routine.

Consideration	Secondary glazing	Full window replacement
Original windows	Retained	Removed
External appearance	Usually unchanged	May change
Listed or conservation properties	Often more suitable	May be restricted
Installation disruption	Generally low	Higher
EPC contribution	Can improve performance when correctly recorded	Usually improves performance
Best fit	Period homes, noise issues, borderline EPCs	Unsound windows or unrestricted modern properties

The right answer depends on the EPC assessment, the condition of the frames and your long-term plans for the property.

Frequently asked questions

Can secondary glazing improve a rental property's EPC rating?

Yes. Secondary glazing can be recorded in the RdSAP assessment for existing homes and may improve the EPC score, particularly when upgrading single-glazed windows. The exact impact depends on the whole property and should be confirmed by a qualified assessor.

Is EPC band C legally required for landlords in 2026 or 2027?

In England and Wales, the current legal minimum remains band E for most privately rented homes. The government is working towards a higher band C standard, but landlords should check the latest official MEES guidance for current requirements and exemptions.

How much does secondary glazing cost?

Indicative 2026 prices range from around £300–£800 per standard window, £600–£1,200 for acoustic glazing and £1,000–£2,200 for heritage grid-matched units. A survey is needed for an accurate quote.

Will secondary glazing damage original sash windows?

A correctly designed and professionally installed system should be discreet, non-destructive and removable. The existing sash window remains in place, although its condition should be checked before installation.

Is secondary glazing enough to reach EPC C?

Sometimes, if the property is already close to band C. It is unlikely to be sufficient on its own for a poorly insulated E- or F-rated property. Treat it as part of a wider, fabric-first improvement plan.

Getting Started

If you're a landlord with period properties, now is the time to act. The 2026 deadline is approaching fast, and installation schedules fill up quickly as demand increases.

We recommend:

1. Get a current EPC assessment to understand your baseline
2. Identify which improvements will have the greatest impact
3. Request a survey for secondary glazing quotation
4. Plan installation during void periods if possible
5. Get a new EPC assessment after improvements

Our team has extensive experience helping landlords achieve EPC compliance while preserving heritage features. Call 020 7060 1572 to discuss your portfolio.