Frequently Asked Questions

Double-glazing (dg) units comprise two panes of glass, separated round the edges by spacer bars, which have a gap between them, filled with gas (usually Argon, sometimes Krypton). These gases, denser than air, reduce heat conductivity between the panes, as do the spacer bars, thus helping to improve energy efficiency and preventing warm air from escaping from inside your home. Good quality units help reduce sound transmission and add strength to your window/door, keeping your home quieter and more secure, as well as reduce the possibility of condensation and frost.

Glass: apart from standard 4mm, other choices include toughened (required by Building Regulations below 800mm), laminated (good for additional sound-proofing and security), anti-UV and anti-glare, and self-cleaning (usually only used on glass roofs or difficult access windows). Most standard dg units are 4/20/4 (28mm) for uPVC and aluminium, although 4/16/4 (24mm) are standard for timber. Units as slim as 12mm can be used in timber products for Listed Buildings.

Spacer Bars: made from various materials such as aluminium or composite materials. Metal conducts heat, so composite are  used in better quality products.

Gas: Argon is the standard in the UK, is 38% denser than air, and is cheaper than Krypton. Optimum spacing between the panes is 16-20mm. Argon does not expand and contract, but glass and spacer bars do, so cheaply constructed units can fail.

Krypton, common in Scandinavian countries, is about 2.8 times denser than air and therefore provides more insulation, but it is more expensive. It is suitable for slimmer glazing units with gaps less than 16mm. This makes it useful for replacement windows in some listed buildings where, say, a 12mm dg unit is allowed (depending on the local planning department), or for use in triple glazing units to keep the thickness of the overall unit as slim as possible.

Low-e: good dg units are usually supplied with an invisible 'soft-coated' layer of tin oxide or silver on the inside of the outer pane, which significantly improves the thermal performance of the window.

Double & triple glazing myths

"Triple glazing is warmer than double": It can be, but only marginally, and some cheaper products perform worse than good quality double. A good tg unit will help iron out 'cold spots' in your home a little more than a dg unit, as the internal surface temperature of the inner glass is slightly less than a good double. Unless you insist, we would suggest that triple glazing is not necessary in the UK climate.

"Triple glazing is quieter": We would recommend a good dg unit fitted with laminate glass in one pane, as this will usually be quieter (and cheaper) than a triple glazed unit.

"New windows will save you money":  good quality windows and doors will usually help reduce your annual fuel bills, but the investment should be viewed as a choice made for aesthetic, security and comfort reasons, rather than thinking your new products will pay for themselves. Having said that, if you have rickety timber single glazed windows and you replace them with a good quality modern product, they may possibly "pay for themselves" over several decades.

"This glass is A-rated": Windows Energy Ratings (WER) are applied by the British Fenestration Rating Council to whole-window tested units (usually submitted by the manufacturer, not the installer). So a complete window can be certified as having a C (minimum required by building regulations), B, A or even an A+ rating. You can check if a particular product has been tested here:

The components of the window, e.g. the frame, the spacer bars, glass etc, have their own U-values - the lower the value, the better the thermal performance. However, the actual performance of an A+ window will drop if it is badly fitted.

All our recommended aluminium, composite and uPVC window products, including our sliding sashes, are A rated or above. Due to the bespoke nature of timber products, they are often not tested by the BFRC. Our timber ranges comprise of some of the lowest U-value components, e.g. standard glazing units only 1.2 (building regulations require a minimum of 1.7).

These days you get what you pay for. And we all have the choice to buy cheap home-assembled furniture, or something that will last us a lifetime. If cost is the only consideration, there is always someone who will do it cheaper. That's why more than 100s of home improvement companies go out of business EVERY MONTH. They are spiralling down to the bottom to get your business. It may appear cheaper to you in the short term, but the cheaper they go, the poorer the product. Let's focus on a mass market product, what we call 'shiny white' uPVC:

"One white uPVC window looks much like another, doesn't it?" Superficially, yes. But so many parts go into one window:

Frames: these are made of lengths of hollow profiles (extrusions) which usually have upwards of 3 cavities. More cavities = better performance, more rigidity, but they also cost more to manufacture. Cheap windows will have 3 empty cavities, better quality will have more cavities with strengtheners in them. TIP: look for wide windows in bungalows. If there is a slight downward bow in the top horizontal frame section, this indicates a cheap product with no reinforcement. 

Glazing units: cheap standard glazing with metal spacer bars and a poor u-value can be significantly cheaper than high quality, thermally efficient low-e glass with composite spacers. A 1.6 u-value is the minimum required by building regulations and therefore the most commonly offered. (In our products our standard glazing is 1.2 u-value, with upgrades to 0.8). TIP:cheap glass doesn't reflect the light evenly and can appear 'wobbly', whereas a good quality glazing unit appears flat and to reflect evenly. TIP: check the product guarantee small print. Glazing units may not have the same guarantee. NB: this is quite usual if your windows require glazing units slimmer than 24mm (e.g. for listed buildings).

Weather Seals: cheap rubber seals can split, harden, flatten and fall out over time, thus allowing the elements in. Good quality composite seals lose little of their shape and efficiency.

Glazing Seals (non-timber): see weather seals above.

Glazing Seals (timber): in timber windows, poor quality is indicated by the use of silicone around the glazing units. This can look unsightly, even on new products. Over time the silicone will not only collect dirt and look worse, but it will degrade, shrink and allow water ingress. Better quality windows incorporate the use of glazing tapes to install the glazing units, although as with most components, glazing tapes vary in quality.

Friction Hinges, Espagnolette locks etc: cheap alloy hardware can literally snap if forced. Otherwise they simply bend and loosen with use, making the window difficult to operate. High quality stainless steel fittings are robust and can frustrate even the most insistent would-be crow-bar intruder. And keep the integrity of the window structure intact for much longer. TIP:look for a greenish tinge to the finish on cheap fittings. Also, see if there is a brand stamp on them (e.g. Maco).

Handles: like the hardware above, handle prices vary dramatically from a few pounds upwards, with guarantees and life expectancy to match. TIP: check the product guarantee small print. A 12 month caveat is common for handles.

Manufacturing: this is a complex subject and varies from one product material to another.

uPVC & aluminium: there are very few product systems out there, but almost anyone can fabricate them (i.e. put them together). Even some of the most reputable non-timber product developers don't care who manufactures their windows and doors. It is more likely that someone making windows in his garage will be cheaper than a large reputable manufacturer who invests hundreds of thousands in state of the art machinery. It may be cheaper, but you will get the quality, durability and guarantees to match.

Timber - specialist window and door manufacturers: these are almost non-existent now in the UK, and are limited to a handful of dedicated manufacturers. Even some very large players in the industry do not advertise the fact that they no longer manufacture, but import 'their' products from other countries (see below). Some actively give the impression they ARE manufacturers via their marketing. The 'production manager' of a major 'manufacturer' works from a laptop 200 miles from the 'workshop'!

Timber - imports: these products have become one of the fastest growing in the sector - not a good development for the consumer. The majority of imported timber product quality varies from the average to less than poor. One installer of imports from Eastern Europe not only fobs off unsuspecting customers with untreated softwood doors (doors should be made of hardwood - at a minimum), but a whole house installation completed in 2011 was rotting away within 6 years - every window and door!

Timber - local joinery companies: specialist manufacturers undoubtedly make the best products. But there are many smaller joinery firms that will make windows and doors as well as a range of other products such as staircases & kitchens. However, product quality will partly be dictated by their use of largely standard profiles of frames, casements, sashes and door leafs, hardware and glazing etc. For example, in 2016, upon arriving at a prospective Clients' home, they had to shout "we'll let you in through the garage!" because their beautiful 5 year old locally made oak front door wouldn't open. The unsophisticated standard profile door and frame made no allowance for the natural movement in the timber and in the damp weather it had swelled jammed shut!

Installation: again, almost anyone can call themselves an installer, and we have seen the evidence. Poor installation can lead to compromised thermal performance and security, reduction in product life and increased likelihood of product failure. Certified installation training is somewhat monopolised by a limited number of courses in a few locations in the UK. This training however, is also limited in its scope, only focussing on uPVC and in relatively controlled conditions. The installers we use cost more because they have wide experience of all types of products and know how to deal with issues which may arise during the project installation.

CONCLUSION: There's lots to think about! You can spend a few hundred pounds per plastic window (+ installation + VAT), or invest properly in your most valuable asset, your home.

A common claim is 'yes'. But the short honest answer is: no. HOWEVER, high quality installations may get you a better sale price.

Estate agents pay little attention to the quality of your windows and doors. If your house value is close to a stamp duty threshold, beautiful new quality products will not take it over that threshold. However, it's common when moving home to have to carry out some home improvements, so when buyers look around your home and see there is less to do when they move, their offer may be higher. So theoretically, your home improvements, carried out sympathetically, could pay for themselves. Additionally, a guarantee which passes to the buyer (e.g. 40 years remaining on an anti-rot, fungal and insect attack warranty on Accoya wood) is a great selling point. TIP: watch out for guarantees which are NON-TRANSFERABLE.

The simple answer is "you get what you pay for". See above for "How much will my new windows and doors cost?" for information on the different quality components that are used in different ranges. For example, pay £900 for a single 'composite' entrance door with a foam core and thin GRP skin which can easily be cut through with a knife and padsaw, or a poor quality handle and lock which can be broken in seconds. Pay double this for a robust solid timber core door with a strong durable handle and a virtually impregnable 3* Diamond lock barrel.

Most colours are now available for timber, aluminium and some uPVC windows.

Timber choices are the most comprehensive with manufacturers being able to match up to RAL numbers, British Standard codes and Farrow and Ball colour ranges. Dual colour products, i.e. different internal and external colours will incur an additional cost to single colour.

For aluminium and some uPVC ranges, there are 150 RAL numbers and these can be selected at point of order. Some ranges have more popular standard colours (e.g. white, grey, cream etc.) in stock, whilst other colours are subject to special order and will cost more. Also, some dual colours, i.e. different internal and external colour combinations, will command an additional cost. Availability, manufacturing timescales and costings vary depending on the manufacturer.

Yes. There is very little that cannot be achieved with regard to design, especially with timber.

Standard period and contemporary styles are available in all materials, but anything out of the ordinary with regard to design or size will have to be manufactured in timber. Some properties have timber and metal windows and doors of varying originality of design and intricacy. All these can be replicated but usually come with a price tag to match.

If you have a home of particular architectural interest, sometimes changing the design or simplifying your requirements may help you to make savings, as long as the changes are sympathetic and acceptable (i.e. to your local planning office, if applicable).

Whoever you are considering for your project - before signing, always read the small print!

Guarantees/warranties vary, and sometimes you will not know what is guaranteed for what period of time until after you have signed on the dotted line. For example, we have seen products with a '10-YEAR GUARANTEE' all over the company's website, whose paperwork has caveats such as: "glazing units 5 years", "paint finishes 5 years", "handles 12 months". Beware 'lifetime' guarantees - check the terms and conditions to ensure they are not so onerous as to make them worthless.

Whilst a 12 month handle guarantee is not uncommon, we believe the way a product is marketed should not be misleading.

What about your guarantees?

All our premium products* and installations come with a minimum 10-year insurance-backed guarantee**, and some have the following additional manufacturer's guarantees:

  • Accoya wood - 50 years (timber: anti-rot, fungal and insect attack)
  • Engineered Sapele/Mahogany & European Redwood - 30 years (timber: anti-rot)
  • Aluminium windows & doors - 20 years (frames & hardware)
  • Aluminium windows & doors - 25 years (finish)
  • uPVC sliding sash windows - 12 years

*Please note that non-premium product guarantees may vary. For example, handles on some ranges may be guaranteed for 12 months.**Timber paint finishes are guaranteed for 10 years, stain finishes 6 years.

Planning permission for new windows and doors should not be required as long as they’re similar in appearance to those already in the house. Replacement windows and doors will have minimal impact on the surrounding properties so you shouldn’t have a problem. If you're unsure, contact your local authority's planning department to check whether you require planning permission. 

You may need planning permission under the following circumstances:

  • You live in a conservation area
  • Your home is listed
  • You live in an apartment
  • Your home is under an Article 4 Direction

CONSERVATION AREAS: sometimes what can be officially enforced does not match what you are told you have to comply with. If you want to replace your timber windows but have a non-timber budget, our premium non-timber sliding sash and casement windows are of a design which is often accepted where others are refused.


Aesthetics are more important than materials, and some planners can be unaware of the non-timber options that are now available, so may try to insist on timber. If in doubt, check with a local independent planning consultant.

Listed buildings are covered by the Planning (Listed Buildings and Conservation Areas) Act 1990 which is intended to protect both the interior and exterior fabric of the building. You must apply for listed building consent when:

  • you want to replace the original windows with replicas of the existing
  • You want to install a new style of window
  • the replacement frames will be made of a different material
  • you intend to change the glass or upgrade from single to double glazing
  • you wish to decorate your windows and use a different colour to the existing

Planning rules for listed building are not universal. For example, some authorities may rule out replacements if they consider your windows to be of historic interest, not just because of the way they look but also because they want you to retain the original materials. Some may allow you to change the windows but they will have to match the existing ones exactly, although you may be able to install modern thermal measures. Some may accept replacement, and allow slimline double-glazed units. There appears to be no hard and fast rule.

If you are unable to have double glazing in your home, secondary glazing is an option which is not usually subject to planning permission, whilst giving many of the of the benefits of double glazing.