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We offer our customers an advanced range of internally beaded double glazed windows incorporating a wide range of styles, designs and options from modern to traditional – and all with the same high specification as standard. A selection of colours and woodgrain effect finishes are available across all of our window ranges and we only install quality products from trusted names such as Rehau and Kömmerling uPVC casement windows, Ultimate Rose, Quickslide and EcoSliders box sash windows, Evolution Storm and Flush timber replacement windows, Aluk and Origin aluminium windows, and Bereco timber windows. Both our standard uPVC casement windows and our Evolution Flush and Storm Windows are all rated A+.

Window ranges installed by Harp

Click on the options below to discover more detail about our different window ranges, features, styles and colours and download PDF Brochures from our Brochures and Videos page.

Quality and security as standard, plus energy efficient

Our Rehau and Kömmerling uPVC casement window range offers better security features, more style choices and exceptional energy efficiency. Every product is tested, certified and manufactured to the very highest standards for proven quality and peace of mind. With a BSI-certified quality manufacturing system and approved security features as standard, we take quality further. With exclusive designs, a wider style range and more additional options, we take choice even further too.


Rehau white uPVC windows with feature rectangle leads.

The outward appearance of most replacement windows and doors can be almost identical, but don’t be fooled into thinking that all uPVC products are more or less the same! The quality of the materials, construction, overall design, locking and weather proofing systems can vary immensely from manufacturer to manufacturer. To help make you aware of the features you should consider when buying replacement uPVC windows, we’ve listed the main points to consider:

  • Fully reinforced 70mm frame depth with a 3mm wall thickness
    Reinforced with aluminium, for a stronger, improved thermal and acoustic performance.
  • Fully reinforced load bearing bay poles that can take a six ton workload
  • Fully welded system that is watertight
    Our casements incorporate a double sealed system with a neoprene seal, both on the outer frame and the vent.
  • Fully internally glazed
    All windows are internally glazed with a stylish ovolo bead so the units cannot be removed from the outside. 28mm overall sealed units in energy efficient low E glass such as Pilkington K or Planitherm Softcoat Total.
  • Low level integrated gasket
    Much less visible and obtrusive, our integrated gasket gives the window a much cleaner appearance, in addition to providing an effective weather-proof barrier.
  • Concealed drainage system
  • Insurance rated multi-point locking system
    Locking in nine places around the window frame, incorporating an espagnolette shoot-bolt locking system with a claw lock and locking wedges. Casements have a secondary locking system where windows can be locked in a semi-closed position, aiding ventilation.
  • Energy efficient A+ rated windows as standard
    In addition to our standard energy efficient glass sealed units, we can provide sealed units with warm edged spacer bars and argon filled units to increase thermal efficiency and improve your carbon footprint.

All these benefits are standard on our uPVC casement windows.

Colours and finishes that stand the test of time

Fancy a change from white windows? Irish oak perhaps? Or maybe a sleek and contemporary anthracite grey? Our standard uPVC casement windows are available in a combination of smooth colours and woodgrain effect foils, all of which are durable, scratch resistant, can be easily cleaned and offer high performance and longevity in all types of weather conditions. We have profile examples of different standard colours available in our Watford showroom. Other non-standard colours are also available on request but would require a longer lead time. Download our colour brochure here >>


Rehau uPVC windows and doors in light oak and anthracite finish.

Vuelta Flush windows from Visage

We’re excited to introduce the Vuelta Flush window, offering all the benefits of modern performance, with the classic, authentic look and feel of a traditional timber window. The casements fit flush within the frame and the clean lines capture the finish of real wood. Vuelta flush sash windows add character to both contemporary and traditional style properties.

A huge range of trending and traditional colour finishes, optional astragal bars plus a choice of heritage, classic or modern handle designs, means that you can truly personalise Vuelta to suit your home and style.

Vuelta flush windows in pebble grey with matching feature astragal Georgian bar.

For more information on our Vuelta Flush uPVC windows download the Vuelta brochure here.

The Ultimate and Heritage Rose sash window

Our Ultimate Rose and Heritage Rose sash windows have been carefully designed with authentic sash details and the result is a class-leading window with woodgrain finishes, industry-leading slim sightlines, putty-effect glass lines, timber style mechanical joints and fully run-through sash horns. Features like these make all the difference, and many find it hard to spot the difference between the Ultimate Rose sash window and a traditional timber sash. As well as being virtually indistinguishable from real timber, the Rose Collection offers many advantages over timber, including increased thermal and acoustic performance, ease of operation, and low maintenance.

Ultimate Rose box sash windows installed by Harp.

Ultimate Rose box sash windows installed by Harp.

Ultimate Rose box sash windows installed by Harp.

Ultimate Rose box sash windows installed by Harp.

The Quickslide Legacy uPVC sash window

The Legacy uPVC sliding sash windows carry all the beauty of a traditional design, coupled with all the benefits of modern materials that enable us to offer a cost effective, low maintenance window that doesn’t compromise on aesthetics. From near-invisible joints, the elegance of the run-through sash horn to the curvy ovolo frame shape and an authentic deep bottom rail, these are just a handful of the many clever details that work together to create a most graceful and advanced sash window.

Quickslide Legacy sash windows in Chartwell green

Quickslide Legacy sash windows in Chartwell green.

With our Legacy sash windows, you can respect the traditions, admire the woodworker’s art, and enjoy modern advances that can make your home warm and secure. You can choose from a wide range of colours and authentic looking woodgrains (we even offer a bespoke colour bonding service, whereby we can produce windows in almost any conceivable hue), styles, features, and hardware options to complement your home.

Quickslide Legacy sash windows

Quickslide Legacy sash windows.

Find out more about both our Ultimate Rose and Quickslide Legacy sash windows on our Brochures and Videos page.

Two top of the range profiles to choose from – Storm or Flush fitting

Our top of the range windows, these are truly innovative, maintaining the look and feel of traditional wood but with all the advantages of state-of-the-art modern window technology. Handcrafted and tailor-made from only the finest materials, they offer outstanding energy saving, exceptional weather proofing and unequalled low maintenance. Two specifications of Evolution window are available – STORM 2 and the FLUSH system, designed to look just like a flush fitting timber window.

HOUSE Storm 2 & Ballingdon front door agate grey 750

Evolution Storm windows and Evolution Ballingdon front door in Agate Grey wood effect.

FLUSH white wood casements with leaded fanlights 750

Evolution Flush casement windows with feature leaded fanlights in white wood effect.

The Evolution Storm range successfully merges high-tech production values with hand-finished craftsmanship producing beautiful windows every time. A+ rated for energy efficiency, it’s this attention to detail that is applied to every single aspect of your Evolution window that makes it different from the rest:

  • Unique timber style jointing system, new timber-look joints (no more weld marks!) and slimline proportions combined with an unparalleled attention to detail; you will find it hard to believe it isn’t wood!
  • An authentic “putty line” finish or Ovolo finish to Georgian bars ensures that your windows suit the style of your home to perfection;
  • Distinctive finishing touches such as feature period handles and working peg stays to add traditional style and elegance to your window;
  • The only manufacturer to offer windows designed to truly match the grace and refinement of genuine Tudor homes with their distinctive black and white elegance;
  • Accepted in conservation areas by a number of local authorities, Evolution windows have already won acclaim from the Heritage Association;
  • A comprehensive locking system with shoot bolts top and bottom and silver-finished steel bolts throughout the security systems for absolute consistency and effectiveness;
  • Quality that can only come from hand finished construction. You simply don’t get this on a standard uPVC window.
WIN EVO storm interior

Interior view of an Evolution window profile. Mechanical joints create a much more realistic timber-like look than a standard uPVC window.

Evolution colours and finishes

If you are feeling creative, the Storm 2 and FLUSH windows are available in a vast array of colours and with the exclusive ‘Kolorbond’ system we can create or match any colour you have in mind, the only restriction is your imagination!

If your tastes are more traditional, you can choose one of our popular wood-effect finishes in black wood, white wood, Tudor (black and white wood) natural wood, oak and cream. For more information why not download our range of Evolution brochures available on the brochures and videos page .

WIN EVO light oak flush

Evolution FLUSH profile in a light oak finish with single horizontal ovolo-putty external Georgian bar.

Enjoying a recent revival in popularity, aluminium windows have continued to be an attractive choice for replacement windows and doors. Harp Windows manufacture and install direct fix aluminium windows and doors, available in a choice of three main standard colours; white, black and brown, and up to 500 RAL colours available to order.

  • Thermally broken maintenance free, strong, durable and tough and fitted direct to brickwork just like uPVC;
  • The tough, protective, polyester powder paint gloss finish is guaranteed to maintain its good looks for many years to come and will only require an occasional wash down;
  • The slimmest and flattest possible sight lines coupled with clean, neat, elegant styling;
  • Will not warp, rust or need painting and are particularly suitable for bay windows where strong sections are essential;
  • Fully weather tested to a category C pass (severe) rating to BS6375 part 1, 2 and 3.

Harp Windows is proud to be an Aluk Approved Quality Fabricator of aluminium windows and doors, and our comprehensive and versatile Aluk product range is designed to provide solutions for all market sectors. You can download our latest Aluk brochure here >>

Crittal replacement aluminium windows and bifold doors in anthracite grey, installed by Harp.

Aluk Crittal replacement aluminium windows and Origin bifold doors in anthracite grey, installed by Harp.

WIN ALI rear elevation house

Aluk white aluminium windows and Origin bifold aluminium doors installed by Harp.

Origin Aluminium Windows

For the ultimate aluminium windows, choose from our premium range by market leaders Origin Global. This is an industry-unique internal and external flush casement. Achieved through combining traditional design, advanced manufacturing and versatile premium grade aluminium, the Origin Casement Window offers high levels of security and thermal efficiency while complementing any type of build. With unrivalled good looks, security and thermal performance, the Origin Window also offers the added benefits of being maintenance free and manufactured from a premium grade aluminium for long-term reliability. The Origin Window can be manufactured in over 150 different RAL shades. From the subtle to the slightly outrageous, you can guarantee there will be a colour to suit every Origin Home, including a dual colour option.

Two styles of window to choose from:

The OW-70 Slimline casement window offers ultra-slim sightlines of just 65mm from sash to frame with an external flush fitting. High security Nemesis locking system which is PAS 24:2016 certified.

OW-70 Slimline window

The OW-80 Premium casement window offers slim sightlines of 91mm from sash to frame with both internal and external flush fitting. High security Yale Encloser Locking system which is PAS 24:2016 certified.

OW-80 Premium window

Thermal efficiency: Able to accommodate both double and triple glazing, Origin windows include a sophisticated polyamide thermal break that’s built into the frame and prevents heat transfer from the inside to outside and vice versa. OW-80 windows can even go the extra mile to achieve a U-Value as low as 0.9 when using Aerogel technology – the same material that’s used in space suits and space shuttles. You can view our Aluminium Installations gallery to see examples of our Origin installations.

750 origin windows & gables

Download the latest Origin Windows brochure on our Brochures and Videos page.

Bereco Timber Windows

Quality and service are the heart of Bereco; only the finest quality sustainably sourced engineered softwood and hardwood goes into the manufacture of Bereco wooden windows, using the most advanced coating systems and the finest architectural ironmongery with extensive warranties. Wood not only has a natural beauty but is a natural insulator ensuring that your home is kept snug and warm. Bereco engineered timber is known to be 60% stronger than its solid timber counterparts, resulting in a low maintenance window with an impressive 60 year lifespan.

Our beautifully crafted timber casement windows are available in both flush and lipped (stormproof) designs. They are internally glazed with easy-clean friction hinges and home insurance approved multi-point locking mechanisms, making them the pinnacle of home security.

Bereco casement windows

Bereco casement windows

Bespoke timber windows from Bereco can be tailored to suit the style and design of your home. Choose from a wide range of mouldings and bar designs, and stylish monkeytail or bulb-end handles and stays available in a range of 10 colours. With factory applied paint or stain finishes including dual colour options, we guarantee that your new Bereco windows will totally transform your home. Download the Bereco brochure from our brochures and videos page.

Energy saving glass

Energy efficient glass products use a special coating to reflect heat from domestic heat sources back into the room, rather than allowing it to escape through the windows. At the same time, this coating allows free heat and light from the sun to pass through the glass, warming the room and further contributing to the energy efficiency of the windows and helping to reduce your energy bills.

For over two decades Pilkington K Glass™ has been the UK’s best known energy efficient glass, in both trade and consumer markets. Now with Pilkington K Glass™ S, the latest soft coat option, the range offers more choice than ever. Pilkington K Glass™ S is a high performance, low-emissivity soft coated product which offers excellent thermal insulation when incorporated within an Insulating Glass Unit (IGU). Pilkington K Glass™ S has a highly neutral appearance with optimal solar heat gain, thermal insulation and light transmission to provide the highest Window Energy Rating (WER) performance.

Helps save money on heating bills through energy saving.
Suitable for use in uPVC, timber and aluminium profiles – both in new and replacement glass windows.
This energy-efficient glass can be toughened, laminated and glazed in the same way as float glass.

You can find out more about Pilkington K S in our PDF brochure.

NOTE: Pilkington K sealed units are now installed in our products as standard. However if you would prefer Planitherm glass this is still available but should be specifically requested.

Endorsements & Reviews

Watch Our Videos

Window unit replacement to a sash

10 Verified Review

Fantastic service from beginning to end. Local showroom in Watford with a super variety of windows and doors The fitment of the sash for my son's bedroom, best decision. Quality window and beautiful finish Paul and Miles are polite and friendly. Paul is a master at his job and Miles is super when finishing and completion. Thanks guys and thank you Harp Windows

Location: WD25September 2023

Replacement front door

10 Verified Review

All appointments on time. Advice useful when choosing design. Fitted in less time than expected.

Location: WD23August 2023

Bay Window Replacement

10 Verified Review

I have to say I have been impressed with HARP from start to finish. I was guaranteed the best price from John at the beginning, There was no hard sell or tricks, Just simple and honest. I ordered 1 window to replace my old bay which I was advised would take 6 weeks from ordering. My window arrived slightly earlier than anticipated and was fitted without delay. The fitting team worked in a clean and tidy manner, were punctual and had a great attention to detail.

Location: WD24July 2023

Supply rear door.

10 Verified Review

Excellent service, most helpful and friendly. Highly recommend.

Location: BH10May 2023

2 x casement windows

10 Verified Review

Very pleased with product and workmanship. All done with no fuss and no mess. Brilliant job. Billy even hoovered up afterwards !

Location: WD18May 2023

New windows and doors

10 Verified Review

Excellent service from both the showroom staff and the fitting team . Quality of the windows and doors is very good , and would highly recommend this company

Location: WD24April 2023

Read all 250 reviews

  • Harp Windows (Watford) Ltd
  • 91-93 St Albans Road
  • Watford
  • Hertfordshire
  • WD17 1UL



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