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Performance, value, and when to choose them

Most of the conversation on our website centres on aluminium-clad timber windows. If you've been exploring Norrsken's range, you've probably encountered those products first: the dual-colour options, low external maintenance and contemporary sightlines. There's a good reason they are our flagship specification for most projects.

But all-timber windows and doors are a strong specification choice in their own right, and in some projects they are the better one. This guide covers what timber windows can actually do: thermally, aesthetically, and in the context of heritage or planning-constrained sites.

 

Key Takeaways

  • Thermal performance between equivalent timber and aluminium-clad timber products is near-identical at the same glazing specification
  • Triple-glazed timber windows can achieve whole-window Uw values around 0.75-0.80 W/m²K, meeting the PHI certified window threshold
  • Timber has lower embodied carbon than aluminium-clad equivalents - a meaningful advantage for low-carbon specifications
  • Timber is typically lower cost than its aluminium-clad equivalent, like-for-like
  • All-timber windows are often the only compliant specification in conservation areas and heritage projects, but that constraint rarely means a performance compromise
  • All-timber windows are available in any RAL colour and a range of stains, with a durable, multi-coat, factory-applied finish 

 

 

Rear elevation view of triple-glazed features in a traditional new build.

How do all-timber windows perform compared to aluminium-clad?

The thermal performance of all-timber and aluminium-clad timber windows is virtually identical in like-for-like glazing specifications.

Both use the same precision-engineered laminated timber core - slow-grown Nordic pine, dense and dimensionally stable - as the structural and insulating base. The external aluminium cladding on our composite products adds durability and protects the timber from the elements; it doesn't contribute directly to thermal performance.

Our P31T all-timber triple-glazed outward-opening window and its aluminium-clad equivalent, the P31A, both achieve a whole-window Uw around 0.75 W/m²K, well within the typical Passive House threshold of 0.80 W/m²K, and a credible specification for low-energy and Passive House builds. The performance difference between them is negligible at equivalent glazing specification.

To put that in practical terms: for the vast majority of projects, including certified Passivhaus new builds, all-timber triple glazed windows can fully meet your thermal specification.

Detail view of a double-glazed timber corner in a cricket heritage restoration.

Are timber windows suitable for Passivhaus and low-energy projects?

Yes. The Passivhaus standard requires a specific space heating demand of ≤15 kWh/m²/yr, primary energy demand of ≤60 kWh/m²/yr, and airtightness of ≤0.6 ACH50.

None of these criteria mandate aluminium-clad frames. What they require is appropriately specified glazing with sufficiently low whole-window Uw values, which all-timber triple-glazed windows can deliver.

Do timber windows require more maintenance than aluminium-clad?

All-timber windows require periodic external and hardware maintenance.

However, Norrsken's timber windows receive a multi-coat sprayed finish under controlled factory conditions, producing a smooth, durable surface that performs well over time. UV exposure is the greatest long-term threat to timber durability, which is why we don't offer a clear finish externally: our paint and stain options provide meaningful protection that a clear coat cannot.

The result is a finish that holds up far better than many customers expect, and periodic inspection and refreshing, typically every five to ten years depending on exposure, is all that's required to keep the window in excellent condition.

Hardware on both aluminium-clad and all-timber windows and doors should be inspected and lubricated at least twice annually. Well-maintained laminated timber windows and doors can last decades.



Internal view of a double-glazed timber outward-opening window in a cricket heritage restoration.

What does a timber window actually look like inside and out?

Norrsken's timber windows receive a multi-coat sprayed water-based paint finish in any RAL colour.

The external result is a smooth, premium surface and in practice, painted timber at this quality level is routinely mistaken for aluminium.

The finish is not rustic. It is not a painted timber aesthetic in the traditional sense: it is a precision factory finish.

Internally, the timber can be painted or simply stained to highlight the warmth, depth, and texture of natural wood. For projects pairing windows with oak flooring, stone, lime render, or painted joinery, the interior timber finish integrates in a way that contributes meaningfully to the overall aesthetic.

When are timber windows the right choice?

Planning-constrained and heritage projects

Timber windows are frequently the only specification that planning authorities will approve in conservation areas, listed buildings, and other heritage contexts.

This need not limit your options. The same bespoke choices available across Norrsken's range apply to all-timber products: any RAL colour, a range of natural stains, custom shapes and sizes. A sympathetic aesthetic does not mean a constrained one.

If you're working on a heritage renovation and anticipating a planning objection to aluminium-clad frames, an all-timber specification with a painted finish can achieve the visual character required while meeting current thermal performance standards. Clients working on listed properties have specified Norrsken on exactly this basis.

Budget-conscious high-performance projects

The powder-coated aluminium shell on an aluminium-clad window adds protection and longevity, but it also adds cost. Like-for-like, all-timber windows are the more accessible price point within the Norrsken range.

If you're committed to triple glazing and high thermal performance but working within a tighter budget, all-timber is a considered choice.

Low-carbon specifications

Timber has lower embodied carbon than aluminium and uPVC as a frame material.

Research comparing frame types on a whole-life basis consistently shows timber frames at lower embodied carbon than aluminium-clad equivalents, although whole-life comparison - thanks to the extra durability lent by protective aluminium cladding - does reduce the carbon cost of alu-clad timber over time.

Norrsken's timber is FSC and PEFC certified, and the manufacturing process uses timber sawdust for factory heating - a closed-loop approach to waste that further reduces production impact.

Which products are right for your project?

Take our short survey to discover the window and doors that differentiate developments.

Timber windows versus uPVC: is there a meaningful comparison?

uPVC windows have a lower upfront cost and require minimal external maintenance. Howeer, they also have a significantly shorter lifespan and cannot be repaired in the same way that timber windows can be.

When a uPVC frame is damaged or deteriorated, the whole unit typically needs replacing. A timber frame can be repaired, restained, or repainted, effectively resetting its surface condition without replacement of the structure.

On environmental credentials, there is no comparison. uPVC production relies on non-renewable petrochemicals and raises serious end-of-life concerns.

FSC-certified timber is a renewable material with significantly lower embodied carbon, is biodegradable at end of life, and stores carbon absorbed during the growth of the trees it came from.

Norrsken does not manufacture uPVC products. Our range begins at timber and extends to aluminium-clad timber - both engineered for long-term performance, both backed by our comprehensive customer care.

Choosing between timber and aluminium-clad windows: the honest guide

Neither specification is universally superior. The right answer depends on your project, your constraints, and your priorities.

All-timber is likely the right choice if:

  • The project is in a conservation area or involves a listed building
  • The budget does not stretch to aluminium-clad, but high performance is still required
  • Embodied carbon is a project priority
  • The external finish will be regularly maintained as part of a wider property care programme

Aluminium-clad timber is likely the right choice if:

  • Low external maintenance is a priority
  • The project aesthetics best suit aluminium external finishes
  • The site is exposed - coastal, elevated, or facing prevailing weather
  • A dual-colour finish (different colour externally and internally) is required
  • Lowest possible maintenance is desired

Both options use the same engineered timber core, carry Norrsken's 10-year warranty, and are available with a range of bespoke options - colour, stain, hardware, configuration - that define our approach. Browse the inspiration gallery to see how both specifications perform in finished projects.

If you're weighing up which product is right for your build, we're happy to talk through the specification in detail. Get in touch with the team, or read reviews from homeowners and architects on Trustpilot who've been through the same decision.

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