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Diamond Windows are a registered FENSA installers

We adhere to a strict code of quality. We notify FENSA whenever an installation has been completed.

Alitherm 800 windows are especially versatile, as they can be applied to commercial and residential properties alike. From contemporary windows for modern offices and homes to traditional casement windows for an elegant finish, the possibilities with Alitherm 800 are endless.

In addition to a stylish appearance, these windows effectively reduce thermal transmittance, as a result of the polyamide thermal break technology. This innovative technology forms a barrier between the warm air inside and the cold air inside, which ultimately enriches the product’s U Value. Consequently, the product is able to reach the standards of Document L 2010.

Speaking of standards, Alitherm 800 windows also adhere to the British Standard Kitemarked system KM 81580 KM 81543. It’s these unique features of this system that is responsible for the low U Value of the product. Therefore, these windows are able to achieve their ‘A’ energy rating in all manner of settings

Our aluminium casement window styles are a popular choice for homeowners because of their classic, chic appearance and ‘A’ energy rating, ensuring your home retains heat, saves you money, and looks good doing it.


Brand: Alitherm

NBS Available: Yes

Thermally Broken: Yes

Dual Colour: Yes

Material: Aluminium Polyamide


BS 4873: Yes

BS 7950:1997: Yes

BS 6375-1:2009: Yes

Kitemark: Yes

Document L Compliant: Yes

U Value: 1.3W/m²K (using correct glass unit)

WER Rating: A


Frame Depth (mm): 70mm

Glazing (mm): 24mm or 28mm double or triple glazed units

Top Hung Max Height (mm): 1300mm

Top Hung Max Width (mm): 1400mm

Side Hung Max Height (mm): 1400mm

Side Hung Max Width (mm): 700mm


Our collection of Alitherm 800 windows comes in a multitude of finishes, colours, and modifiable designs. Each of these windows has a polyester powder coat that can be applied in an anodised, textured, metallic, or coloured finish. In addition to the aesthetics of the frame, you can also opt for colour-coordinated hinges or handles for an effortlessly quality finish.

Alternative Styles

The beauty of Aluminium is that it's available in any single or dual RAL colour so you are sure to find the perfect colour for your home.


In addition to various finishing options, there is also a multitude of ways in which Alitherm 800 windows can be applied. For instance, you may opt for angled frames, top hung open out casements, side hung open out casements, or even fixed windows. Regardless of your property’s requirements, there’s an Alitherm 800 solution to suit.

10 Year Guarantee

All of our double-glazed casement windows are easy to maintain and keep looking like new, partly due to their durability and longevity. We’re so confident in our windows that we offer a ten-year guarantee as standard.

Shop Alitherm 800 Windows with Diamond Windows

When searching for double-glazing specialists in the West Midlands, you needn’t look further than Diamond Windows. We’re well equipped in supplying and installing windows, so please don’t hesitate to get in touch regarding your window needs. Our expert team will be more than happy to advise you about our Alitherm 800 range or any other window types.

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Contact us
Diamond Windows, Unit 22, Northstreet I.E, Droitwich,West Midlands, WR9 8JB
Company Reg: 5367399
Open Hours
Mon to Fri: 9am to 4.30pm
Sat: 9am-1pm
Sun: By appointment