Understanding Window Film and Blackout Blinds as Thermal Solutions
Every winter, millions of UK homeowners feel the chill radiating off their windows and wonder whether there is a practical, affordable way to stop the cold creeping in without replacing their glazing entirely. Two products come up repeatedly in this conversation — thermal window film and blackout or thermal blinds — and both deserve a proper, honest explanation before you spend any money.
Both thermal window film and thermal blackout blinds genuinely help keep heat in during winter, though neither fully matches the performance of modern double or triple glazing. Thermal window film costs roughly £5 to £15 per square metre and works by reflecting infrared heat back into the room using a low-emissivity coating applied directly to the glass. Quality honeycomb thermal blinds cost £40 to £150 per window and trap a layer of still air to prevent cold transfer from the glass surface. For the best results, particularly on single-glazed or older double-glazed windows, combining both products delivers the most meaningful heat retention improvement and can reduce heat loss through the glass by up to 45 percent — a worthwhile upgrade for most UK homes before considering the far greater expense of full window replacement.
- Choose thermal window film specifically labelled as low-emissivity or heat-retaining — decorative, UV or privacy films do not meaningfully improve winter heat retention
- Fit thermal or honeycomb blackout blinds as close to the window recess as possible to maximise the still-air insulation pocket and prevent cold draughts falling into the room
- Budget roughly £5 to £15 per square metre for DIY thermal window film and £40 to £150 per blind for a quality thermal blackout blind with honeycomb lining
- Combine both products on single-glazed or older double-glazed windows for the greatest improvement — film on the glass and a well-fitted thermal blind over the top
- Check whether your local authority or energy supplier offers insulation vouchers or ECO4 scheme support before purchasing, as some households qualify for funded draught-proofing and window measures
- Measure window recesses precisely before ordering thermal blinds — a poor fit with gaps at the sides removes most of the insulating benefit
- Neither product replaces professionally installed modern double or triple glazing, but both deliver measurable heat retention improvements at a fraction of full window replacement costs
- Understanding Window Film and Blackout Blinds as Thermal Solutions
- How Much Heat Is Actually Lost Through Windows in a UK Home
- How Thermal Window Film Works on Glass
- How Blackout Blinds and Thermal Lined Curtains Keep Heat In
- What to Look For When Choosing Between Film and Blinds
- What These Products Actually Cost in 2026
- Are There Any Grants or Schemes That Cover These Products in 2026
- Combining Film and Blinds for Maximum Winter Performance
Thermal window film and well-fitted blackout or thermal blinds both genuinely help keep heat in during winter, but they work in different ways and deliver different levels of improvement. Window film works directly on the glass surface, reflecting heat back into the room, while thermal blinds create a pocket of insulating still air between the glass and the living space. Neither product fully replicates the performance of professionally installed modern double glazing, but both offer measurable, meaningful improvements — particularly for homes with single-glazed or older double-glazed windows — at a fraction of the cost of full window replacement.
Thermal window film is a thin adhesive or static-cling polyester layer applied directly to the surface of the glass. It works by incorporating a low-emissivity coating that reflects long-wave infrared radiation — the type of heat your radiators produce — back into the room rather than allowing it to pass through the glass and escape outside. This is distinct from purely decorative films, UV-blocking window tints, or privacy films, which do not meaningfully address heat retention.
Blackout blinds, in the context of winter heat retention, are heavy, tightly fitted window coverings — frequently incorporating a thermal lining or honeycomb cell structure — designed to block both light and cold air from entering a room. Their insulating mechanism relies on trapping a layer of still air between the cold glass and the warmer room interior. Still air is a surprisingly effective insulator; the challenge is keeping it genuinely still and contained, which is why fit matters enormously.
The key distinction between the two products is the mechanism of action. Window film works on the glass itself, altering its thermal properties at the surface level. Blinds work in front of the glass, using an air buffer zone to slow the transfer of heat from the room to the cold glass surface. Both approaches reduce heat loss, but they are not interchangeable — and for many homeowners, using both together will produce better results than either alone.
In 2026, with UK energy bills remaining elevated following years of price cap volatility, these products have moved from niche interest to genuine mainstream consideration. Homeowners with pre-1980s terraced houses, Victorian semis, or any property with original single glazing are the primary audience — but even owners of older double-glazed properties with dated, underperforming units can benefit.
Practical tip — before purchasing either product, stand close to your windows on a cold evening with the heating on. If you can feel cold radiating from the glass or a draught around the frame, you have a meaningful heat loss problem that both of these products can help address.
How Much Heat Is Actually Lost Through Windows in a UK Home
Windows are one of the most significant sources of heat loss in a typical UK home, accounting for a substantial share of your total heating energy. According to the Energy Saving Trust, windows can be responsible for around 10 to 25 per cent of a home’s total heat loss, depending on the type of glazing installed and the age of the property. In a typical three-bedroom semi-detached house heated by gas, that could represent a considerable portion of your annual heating bill escaping through the glass.
To understand why this matters practically, it helps to understand the U-value — a measurement of how quickly heat passes through a material. The lower the U-value, the better the material is at retaining heat. Single-glazed windows, which are still found in a significant number of pre-1980s UK properties, have a U-value of approximately 5.0 to 5.8 W/m²K. Standard double glazing sits around 2.8 to 3.1 W/m²K. Modern low-emissivity double glazing — the type required in new builds and replacement windows under current Building Regulations — performs at around 1.2 to 1.8 W/m²K. The gap between single glazing and modern low-E double glazing is enormous, and it shows up directly on your heating bills.
Thermal window film and well-fitted thermal blinds cannot close that gap completely, but they can nudge performance meaningfully towards the better end of the range. A quality thermal film applied to single glazing can improve its effective U-value by reducing radiant heat loss, with some manufacturers claiming improvements that bring single-glazed performance closer to that of basic double glazing. Thermal cellular blinds, when properly fitted with minimal air gaps, can add a further layer of resistance that reduces heat loss through the overall window assembly.
The honest answer to whether these products work is yes — both thermal window film and well-fitted blackout or thermal blinds do reduce heat loss through windows in measurable ways. They are best understood as meaningful, cost-effective improvements that make a genuine difference to comfort and running costs, not as permanent solutions equivalent to a full glazing upgrade. For a home with single glazing across multiple rooms, the cumulative effect of treating every window can be quite significant.
Practical tip — if you are unsure what type of glazing you have, check the edge of the glass unit in a corner of the window. Single glazing will show just one pane. Double glazing will show two panes with a visible gap; older units often have aluminium spacer bars, while modern units use warmer-edge spacers. The age and condition of the spacer bar is also a clue to how well your double glazing is still performing — failed seals and misted units lose much of their insulating value.
How Thermal Window Film Works on Glass
Thermal window film operates at the level of the glass surface itself, making it one of the most direct interventions available for improving a window’s heat retention without replacing the unit. Understanding how it works helps you choose the right product and set realistic expectations.
There are two main types available to UK homeowners. Self-adhesive films bond directly to the glass using a thin layer of adhesive and are intended as a semi-permanent or permanent installation. They are typically more durable and offer better optical clarity than the removable alternative. Static-cling films use electrostatic adhesion rather than glue, meaning they can be applied and removed without leaving residue — a significant advantage for renters or anyone who does not want to make permanent changes to their glazing.
The thermal benefit comes from a low-emissivity metallic coating embedded within the film. This coating works by reflecting long-wave infrared radiation — the heat energy emitted by warm objects and surfaces inside your home — back towards the room rather than allowing it to pass through the glass and be lost outside. This is the same principle behind the low-E coatings applied to modern double-glazed units during manufacture, scaled down to a retrofit product.
A third category is worth mentioning separately because it works quite differently — the secondary glazing film kit, sometimes called a stretch-and-shrink window insulation kit. These kits consist of a thin transparent plastic film that is stretched across the entire window frame and then heated with a hair dryer to shrink it taut. This creates a sealed air gap between the film and the existing glass, replicating the basic principle of secondary glazing at very low cost. These kits do not improve the glass surface itself; instead, they add a new layer of still air in front of the window. They are particularly effective on draughty or poorly sealed older windows and are widely available from major DIY retailers across the UK.
On the question of summer and winter performance, many thermal films are marketed as year-round products. In winter, the low-E coating helps retain heat. In summer, the same coating can reduce solar heat gain coming through the glass, potentially keeping rooms cooler. However, homeowners should read the specific product data carefully — some heat-retention films may slightly reduce visible light transmission, which could be a drawback in north-facing rooms that already receive limited natural light. Always check whether the product’s specification includes both a U-value improvement figure and a solar heat gain coefficient before purchasing.
Practical tip — when applying self-adhesive window film, clean the glass thoroughly with a solution of water and a small amount of washing-up liquid before installation. The cleaning solution also acts as a slip agent during application, allowing you to reposition the film before it bonds. Squeegee out any air bubbles from the centre outwards. A careful installation makes a significant difference to both appearance and performance.
How Blackout Blinds and Thermal Lined Curtains Keep Heat In
Blackout blinds and thermal curtains address window heat loss from a different angle entirely — rather than modifying the glass, they create a physical barrier of trapped air between the cold window surface and the warm room. This air buffer slows the rate at which heat moves from the room to the glass and then escapes outside, working on the same basic principle as cavity wall insulation or a double-skin sleeping bag.
The critical word here is still. Still air is an excellent insulator; moving air carries heat away rapidly. The insulating benefit of a blind or curtain depends almost entirely on its ability to trap a genuinely still pocket of air in front of the glass. This is why fit is the single most important factor when choosing and installing these products. A blind or curtain that leaves significant gaps at the sides, top, or bottom will allow cold air to circulate in a convection loop — cold air falls from the glass, flows along the floor, and is replaced by warm room air, which then cools against the glass and falls again. This process, sometimes called cold air downdraughts, can make a room feel significantly colder even when the heating is running.
Not all blackout blinds are created equal from a thermal perspective. Standard blackout blinds are primarily designed to block light, and while their additional layer does provide some insulating benefit, it is modest compared to products specifically engineered for thermal performance. Cellular or honeycomb blinds are the standout performers in this category — their distinctive structure incorporates multiple air pockets within the blind fabric itself, each pocket adding a layer of insulation. These products are well established in the UK market and can deliver meaningful U-value improvements when correctly fitted within the window recess.
Thermal-lined curtains work on the same principle of trapped air, and the Energy Saving Trust acknowledges that drawing curtains at dusk can measurably reduce heat loss through windows, particularly in older homes. The heavier the curtain and the better the lining, the greater the effect. Floor-length curtains that sit close to the sill or extend slightly beyond it perform better than shorter curtains that leave a gap at the bottom through which cold air can circulate. Adding a pelmet across the top of the curtain rail — even a simple fabric or timber pelmet — prevents warm room air from being drawn behind the curtain at the top, significantly improving the overall insulating performance of the installation.
For rooms where aesthetics are important and light control matters, a combination approach often works well — thermal roller blinds fitted close within the recess, combined with lined curtains drawn over them in the evenings. This layered approach can deliver noticeably better comfort than either product alone.
Practical tip — if you are retrofitting blinds to an existing window, measure the recess depth carefully before ordering. A recess-fit blind sits inside the window reveal and creates a much tighter seal than a face-fit blind mounted on the wall above the window. The extra few centimetres of overlap on each side makes a real difference to how much cold air can bypass the blind and circulate in the room.
What to Look For When Choosing Between Film and Blinds
Choosing between thermal window film and thermal blinds — or deciding to use both — depends on several practical factors specific to your home, your tenancy situation, and your budget. The following steps will help you make a well-informed decision rather than simply buying the cheapest available product.
- Assess your window type first. Single-glazed windows benefit most substantially from both products, and any investment here is likely to deliver noticeable comfort improvements. If you already have modern low-emissivity double glazing installed within the last decade, the marginal thermal gain from adding film or upgraded blinds will be smaller — worth considering for comfort reasons, but unlikely to produce dramatic changes to your heating bills.
- Check your tenancy situation before committing to any adhesive product. Renters should favour static-cling removable film, which leaves no permanent marks on the glass, or tension-fitted blinds that use no fixings at all. Always review your tenancy agreement and, if in doubt, ask your landlord in writing before making any changes to windows or fittings. Some landlords are receptive to tenant-funded improvements, particularly if they are fully reversible.
- Measure the window recess carefully before ordering blinds. A recess-fit blind installed within the window reveal creates a far more effective air seal than a face-fit blind mounted on the surrounding wall. Measure the recess width at the top, middle, and bottom — older UK properties often have reveals that are not perfectly square — and order to the smallest measurement to ensure a proper fit. For film, measure the glass area to calculate how much film you need, allowing a small overlap at the edges.
- Look for independently tested thermal performance data. For window film, check whether the product’s specification includes a published U-value improvement figure or a solar heat gain coefficient. For blinds, look for products tested to BS EN 14501, the European standard for the thermal and visual comfort performance of blinds and shutters. Reputable manufacturers will publish this data; if a product listing does not include it, treat the thermal claims with caution.
- Consider the room’s existing ventilation arrangements. In rooms that are already prone to condensation — often kitchens, bathrooms, or bedrooms in poorly ventilated properties — significantly reducing air movement around windows can worsen moisture problems. If your window frames show existing signs of condensation or mould, address background ventilation first. Trickle vents (the small adjustable slots built into many modern window frames) should be left open to allow a controlled exchange of air. Sealing windows tightly with film kits while also blocking airflow can push condensation into wall cavities or behind furniture.
- Budget realistically and compare the cost-per-window across your whole home. Film is generally the cheaper option per window and can be applied across an entire house for a modest outlay. High-quality thermal cellular blinds cost considerably more per window but may deliver greater long-term comfort and require less maintenance. See the cost section below for detailed figures. For most homeowners, a combination approach — film on the most heat-leaking windows and premium blinds in the most-used living spaces — often represents the best balance of cost and benefit.
Practical tip — take photographs of each window before installation, including measurements, and keep receipts for all products purchased. If you later decide to sell the property or are a tenant moving out, this documentation demonstrates that any changes were carefully made and reversible where required.
What These Products Actually Cost in 2026
One of the most compelling arguments for thermal window film and thermal blinds is their affordability relative to full window replacement. In 2026, replacing all the windows in a typical three-bedroom semi-detached house with A-rated double glazing costs in the region of £5,000 to £10,000 depending on the installer, the window style, and the region of the UK. By contrast, treating the same windows with a combination of thermal film and upgraded blinds could be achieved for a few hundred pounds — a fraction of the cost, with a meaningful (if smaller) improvement in thermal performance.
The following table provides indicative 2026 retail and installation costs for the main products discussed in this article. These figures are based on publicly available retail pricing and are intended as a guide; actual costs will vary by retailer, window size, and location across the UK.
| Product Type | Approximate DIY Cost | Approximate Professional or Premium Cost | Estimated Thermal Benefit | Ease of Installation | Suitable for Renters |
|---|---|---|---|---|---|
| Self-adhesive thermal window film (per m²) | £5 to £20 per m² | £30 to £80 per window professionally applied | Moderate improvement on single glazing; reduces radiant heat loss | Moderate — requires clean glass and patience | No (permanent adhesive) — check tenancy agreement |
| Static-cling removable thermal film (per m²) | £8 to £25 per m² | Not typically professionally installed | Slight to moderate improvement; less durable than adhesive films | Easy — fully removable | Yes |
| Secondary glazing stretch-and-shrink film kit (per window) | £5 to £15 per kit | Not typically professionally installed | Moderate to good on draughty or single-glazed windows; creates an air gap | Easy — requires only a hair dryer | Yes — fully removable |
| Budget blackout roller blind (standard size) | £20 to £60 per blind | N/A — usually DIY installed | Slight improvement; primarily light-blocking rather than thermally engineered | Easy to moderate | Depends on fixing method |
| Mid-range thermal roller or Roman blind | £60 to £150 per blind | £100 to £200 including measuring and fitting | Moderate improvement, particularly when recess-fitted | Moderate | Tension-fit versions suitable for renters |
| Premium cellular or honeycomb thermal blind | £150 to £350+ per blind | £200 to £450 including professional fitting | Good — engineered air pockets deliver best blind-category performance | Moderate — precise measuring essential | Some models available with no-drill fittings |
| Ready-made thermal lined curtains (per pair) | £30 to £100 per pair | Made-to-measure from £150 to £400+ per pair | Moderate — effectiveness depends heavily on fit and length | Easy | Yes — fully removable |
For a typical three-bedroom semi-detached house with eight to ten windows, treating every window with mid-range secondary glazing film kits would cost approximately £50 to £150 in materials and an afternoon of time. Upgrading to mid-range thermal blinds throughout would cost approximately £600 to £1,500 depending on window sizes. A combined approach — film on all windows, premium thermal blinds in the main living room and bedrooms — might come to £400 to £900 in total, still well under a tenth of the cost of full window replacement.
The following table compares these solutions against basic window replacement as a quick cost reference.
| Solution | Typical Cost for a 3-Bed Semi | Thermal Improvement Level | Disruption Level |
|---|---|---|---|
| Secondary glazing film kits throughout | £50 to £150 | Moderate — best on single glazing | Minimal |
| Thermal film and thermal blinds throughout | £400 to £900 | Good — particularly on single or older double glazing | Minimal |
| Secondary glazing (professionally installed panels) | £3,000 to £6,000 | Very good — approaches double glazing performance | Low to moderate |
| Full double glazing replacement (A-rated units) | £5,000 to £10,000 | Excellent — Building Regulations compliant | Moderate to high |
Practical tip — always obtain at least three quotes for any professionally fitted product, including made-to-measure thermal blinds or professionally applied window film. Prices vary considerably by region and by company, and some installers offer meaningful discounts for whole-house commissions compared to single-window pricing.
Are There Any Grants or Schemes That Cover These Products in 2026
It is worth understanding clearly which government schemes are and are not relevant to thermal window film and blinds, because there is sometimes genuine confusion among homeowners about what financial support is available for window-related improvements.
The ECO4 scheme (Energy Company Obligation 4) is a government-backed programme administered through energy suppliers that funds insulation and heating improvements for low-income and vulnerable households. ECO4 focuses primarily on solid wall insulation, loft insulation, cavity wall insulation, and heating upgrades. Thermal window film and blinds are not listed measures under ECO4. However, if your household qualifies for ECO4, it is worth asking your energy supplier whether a full glazing upgrade — secondary glazing or full window replacement — might be fundable under the scheme’s broader fabric improvement provisions. Eligibility depends on your household income, benefit status, and the current energy efficiency rating of your home.
The Great British Insulation Scheme (GBIS) offers support for a single insulation improvement to a broader range of households than ECO4, with less restrictive income thresholds. Again, thermal film and blinds are not listed measures. The scheme is focused on loft and wall insulation. However, homeowners who qualify for GBIS should explore whether secondary glazing or a window upgrade might be available, as the scheme’s scope is subject to ongoing review by the Department for Energy Security and Net Zero (DESNZ).
The Boiler Upgrade Scheme (BUS) is not relevant to window products of any kind. It covers the installation of air source heat pumps, ground source heat pumps, and biomass boilers only, offering £7,500 towards the cost of a qualifying heat pump installation. It is mentioned here only to prevent the confusion that some homeowners experience when researching energy efficiency grants — BUS is specifically and exclusively for low-carbon heating systems. Any installer registered under the Microgeneration Certification Scheme (MCS) can install a qualifying heat pump; you can verify MCS registration at the official MCS register at mcscertified.com.
Some local authorities and energy suppliers operate their own smaller grant and incentive programmes that may cover a broader range of energy efficiency measures, including draught-proofing, secondary glazing, and occasionally window film or blinds under micro-grant schemes. The Simple Energy Advice (SEA) service, operated on behalf of the government, is a useful starting point for checking what support may be available in your area — it can be accessed at simpleenergyadvice.org.uk. It is also worth contacting your energy supplier directly, as several major suppliers operate their own home energy improvement programmes with varying eligibility criteria.
The honest summary for most UK homeowners in 2026 is that thermal window film and blackout or thermal blinds are not currently covered under the main national energy efficiency grant programmes. They are best approached as affordable, self-funded improvements that deliver real comfort benefits and modest reductions in heating costs — investments that pay for themselves relatively quickly given the low initial outlay, without requiring any application process or eligibility assessment.
For homeowners who do qualify for ECO4 or GBIS, the right approach is to pursue those schemes for the larger, more impactful measures — wall and loft insulation, heating upgrades — and to use self-funded film and blinds as a complementary, lower-cost addition to the overall thermal improvement of the home.
Practical tip — when contacting the Simple Energy Advice service or your local council, be specific about your property type, glazing situation, and household income. The more detail you provide, the more accurately an advisor can identify whether any available schemes apply to your circumstances. Always ask whether secondary glazing — a more substantial intervention than film or blinds — is a qualifying measure, as it sits in a grey area between full glazing replacement and minor draught-proofing in many schemes’ definitions.
Combining Film and Blinds for Maximum Winter Performance
For homeowners who want to get the most from these products without investing in a full glazing upgrade, a layered approach — combining thermal window film on the glass with well-fitted thermal blinds or curtains in front — delivers the best overall result. This combination addresses heat loss through two separate mechanisms simultaneously, and the cumulative effect is greater than either product alone.
The film improves the thermal performance of the glass itself by reducing radiant heat loss. The blinds or curtains then reduce the convective heat loss that occurs when warm room air contacts the cold glass surface and flows downward as a cold draught. Together, they address the two main pathways through which a window loses heat in winter.
In a typical draughty Victorian terrace with single-glazed sash windows — a very common scenario in older UK cities — the combination of a secondary glazing film kit and a well-fitted cellular blind can make a room feel substantially warmer and less draughty without a single structural change to the building. For homeowners in this situation, particularly those living in listed buildings or conservation areas where full window replacement may require planning consent or face restrictions, these products represent a genuinely useful and accessible solution.
It is also worth acknowledging what these products cannot do. They will not resolve the issue of failed or misted double-glazed units, where the sealed air gap between the panes has been compromised and moisture has entered. They will not address significant structural draughts around window frames caused by failed putty, cracked beads, or poorly fitted frames — those issues require direct repair or replacement. And they will not bring an older window’s thermal performance up to the standard required by current Building Regulations for replacement glazing, which is relevant if you are planning a major extension or renovation that triggers a full thermal compliance assessment.
Used appropriately, with realistic expectations, thermal window film and thermal blinds are honest, practical tools for improving winter comfort in UK homes. They are low-risk, low-cost, and available to almost everyone — including renters — making them one of the more accessible entries in the energy efficiency toolkit for ordinary homeowners who are not yet ready, or not yet able, to invest in a full glazing upgrade.
Practical tip — if you live in a listed building or a property within a conservation area and are considering secondary glazing as a step up from film, contact your local planning authority before proceeding. In many cases, secondary glazing that is not visible from outside the building does not require listed building consent, but this varies by local authority and it is always better to confirm in writing before spending money on installation. secondary glazing options for listed buildings and conservation areas
draughtproofing windows and doors — a complete guide for UK homeowners
single glazing vs double glazing — is it worth upgrading in 2026
how to improve an older home's energy efficiency without major renovation
ECO4 and Great British Insulation Scheme — what UK homeowners can claim in 2026
Frequently Asked Questions
does window film actually keep heat in during winter uk
Yes, low-emissivity thermal window film reflects infrared heat back into a room rather than letting it escape through the glass. Quality thermal films applied to single-glazed windows can reduce heat loss through the glass by roughly 30 to 50 percent. DIY kits cost approximately £5 to £15 per square metre from UK retailers such as B&Q or specialist glazing suppliers.
what is the difference between thermal blinds and blackout blinds for insulation
Standard blackout blinds block light but offer limited thermal benefit unless they also feature a thermal lining or a honeycomb cell structure. Honeycomb or cellular thermal blinds trap still air in their cells, significantly reducing cold transfer from the glass. Expect to pay £40 to £150 per blind for a genuinely insulating thermal blackout blind from UK suppliers — budget blackout blinds under £20 typically provide very little winter heat retention.
how much can thermal window film reduce heating bills uk
Independent assessments suggest well-applied low-emissivity window film on single-glazed windows can cut heat loss through the glass by up to 45 percent, which for a draughty Victorian terrace with many single-glazed panes could contribute a saving of £50 to £150 per year on heating bills. Savings vary considerably depending on the number of windows treated, the existing glazing type, and your current energy tariff.
can i get any grants or funding for window insulation measures in the uk in 2026
The ECO4 scheme, administered by Ofgem, provides funded energy efficiency improvements for eligible low-income and fuel-poor households, though it primarily covers insulation and heating upgrades rather than window film specifically. Some local authority Flexible Eligibility schemes and energy supplier obligations do cover secondary glazing and draught-proofing measures — contact your local council or check the Simple Energy Advice service to assess eligibility.
is window film or thermal blinds better for older double glazed windows
For older double-glazed windows that have lost their argon gas fill or developed seal failures, thermal blinds generally deliver a more noticeable improvement because they add an entirely new insulating layer over the degraded unit. Window film still helps by reducing radiative heat loss through the glass itself. Using both together on aged double glazing is the most cost-effective upgrade short of full window replacement, which averages £400 to £900 per casement window in the UK.
