Timber Windows Guide – How to Specify Timber Glazing for Your Project

Depending on specification, modern windows typically deliver U-values between 0.6 W/m²K (the best triple-glazed products) and 1.2 to 1.6 W/m²K for standard double glazing. Both can therefore comfortably meet current Building Regulations, so your choice will come down to the level of performance you require. Always check what quoted U-values refer to: you should focus on the whole-window U-value when specifying your project (not just the centre-pane figure). Wood is a natural insulator, so when specified alongside the right glass, it should easily meet or surpass this requirement.

How Should You Look After Timber Windows?

In terms of maintenance, timber units require little upkeep. The frames should only require washing down every 6-12 months, at which point it’s a good idea to lubricate the hardware, too. As a rule of thumb, factory-finished timber windows with an opaque coating won’t need repainting for about a decade.

Available in both an outward-opening side- or top-hung configuration, plus an inward-opening tilt and turn option, this stylish design from 21° is fully customisable. Ideal for creating a thermally efficient home, the triple-glazed option can reach U-values of 0.80 W/m²K. Part of the GBS78 range, costs start at £720

Lighter colours last longer than dark finishes as they provide better protection against UV rays. Weather conditions and aspect will have an impact, too. For instance, south-facing windows will need re-coating sooner than others due to increased exposure to the sun.

How Versatile Are Timber Windows?

Whether you are creating a modern house or renovating a period home, you’ll easily be able to find wood units to suit your scheme. One of the most popular characteristics of timber windows is that they give your home a warm and characterful feeling that’s difficult to match with synthetic materials. The sheer range of options available means that they’re versatile, too – you can select from a whole host of designs, finishes and colours.

With ultra-slim, unobtrusive frames, picture windows are a great way to maximise sightlines and the flow of natural light through your space. The P31A in a fixed pane model from Norrsken provides an eye-catching snapshot of the outdoors, with all the performance benefits of a timber frame. This model starts from £1,000 per m²

For those trying to create an authentic period-style home (or renovating one), timber is often the go-to choice. Sliding sashes are authentic to Georgian and Victorian houses, for example, and feature two independent units that move up and down to open. Some modern interpretations allow the top and bottom sashes to separately tilt inwards so they can easily be cleaned from inside.

For more contemporary projects, there are two popular designs that lead the way. Probably the most common is the outward opening casement (which can also be suited to chocolate-box cottages and other traditional homes). This can be hinged in a variety of ways to suit your requirements in terms of aesthetics and safety – top hung, top swing and side hung are the most popular.

Grabex’s sash windows expertly replicate the traditional design, using multi-layered engineered timber for excellent durability and modern performance values. Bespoke options and specialised solutions for listed buildings or conservation areas are available in a range of RAL colours and timber stains to suit your home’s unique requirements

Tilt and turn/inward opening windows are an easy-to-use alternative. With a simple twist of the handle, the window can be tipped inwards from the top for ventilation. A second turn allows you to open the window the whole way, hinged at the side. When it comes to cleaning, these units are great – the casement can be opened into the room, so both sides of the glass and the whole of the frame can be washed.

your guide to window opening styles

Which Species of Timber are Used for Glazing & Which is Best?

Finding the best timber windows for your build starts with selecting the right type of wood for the job. Remember that the material you specify will impact on the style and finish you want to achieve, as well as determining the relevant maintenance requirements.

Hardwood

Oak, walnut and maple are amongst the most common hardwoods. Typically, these have more complex structures, making them naturally dense and hardwearing. Their condensed structure makes hardwoods well equipped to face the elements. Many are also prized for their natural grains and classic, decorative finishes.

This bespoke option from Kloeber can be finished in any RAL colour of your choosing. The versatile design is available with double or triple glazing, offering excellent U-values down to 0.9W/m²k. The timber flush casement window starts from £1,415

Softwood

Pine, cedar and spruce are all conventional softwoods. Because these evergreens grow faster than hardwoods, they are less dense but generally more cost-effective. This also means that softwoods are more sustainable because they can be replenished much faster. Easier and cheaper to work with, softwoods are extremely versatile and, when treated, able to perform just as well as many hardwoods.

Modified timber

Ash, oak and pine are all widely available in modified variations. Thermally-treated timber undergoes a process to alter the cellular structure of the wood, making it more stable and less able to absorb moisture.

To solve the soft versus hardwood debate, Matt Higgs from Kloeber says, “avoid the trap of believing that all hardwoods are better and stronger than all softwoods. Laminated and engineered timbers will be more robust than solid, singular sections of timber, regardless of the species.”

How Much Do Timber Windows Cost?

The biggest differentiator when it comes to window prices is the material used for the frame. “In general, PVCu is the cheapest option, followed by aluminium, softwood, hardwoods and then alu-clad and steel at the top end,” says Matt Higgs from Kloeber. While plastic types will typically be 30% cheaper than wood, you must remember that this is just the outlay cost – there is no allowance here for service life. In general, factory finished timber window frames will have twice the life of PVCu, so overall they are usually better value.

These Norrsken P31A windows and S307A outward open framed doors are designed to meet your aesthetic and practical demands. Each opening is manufactured to operate smoothly throughout the lifecycle of the product. (The 2023 Build It Award-winning P31A window starts from £900 + VAT for a 1,150mm x 1,150mm top- hung unit)

Softwood, usually made from larch or Douglas fir, is typically the most affordable option, although it will require more maintenance than hardwoods. Hardwood costs more up front, but is denser and therefore more durable. Oak stands out as the preferred material, and is favoured among self builders for its natural character. The wood can be treated to preserve its original blond appearance, or can be left untreated to gradually weather to a silver grey.

The timber window costs below are based on a 1,200mm x 1,200mm double-glazed, double-opening casement window that would meet current Building Regulations. These benchmark prices are supply-only; installation would be an additional cost.

• A softwood timber window could cost £1,130 excluding VAT
• A hardwood timber window is likely to cost £1,220 excluding VAT
• An oak timber window will cost approximately £1,365 excluding VAT

You should budget around £35 for trickle vents per window, if required. Triple glazing is likely to add an additional £45 to each window’s cost.

FAQs

Nigel Jackson Nigel Jackson, director at Norrsken answers the key questions for specifying high-quality timber windows to complement your home. Norrsken manufacture high-performance glazing solutions, ideal for low-energy self builds and renovations.

When should you reach out to potential timber window suppliers?

On a self build project, it’s best to speak with expert providers during the planning phase – before breaking ground. Working out a feasible budget by comparing quotes and discussing your project’s needs with specialists is best done as soon as possible. Making important decisions about the details in your build such as set-backs, rebates for cills and junctions with the building’s exterior detailing, are just a few of the considerations that will alter certain window and door features, and shouldn’t be rushed or decided on the fly.

How can you ensure you’re making a sustainable choice when specifying timber windows?

Firstly, know that in choosing timber you’re making the most eco-conscious decision in terms of frame material. Production methods and waste matter is inherently more environmentally friendly than those made out of PVCu or aluminium. Plus, they have a much lower embodied carbon footprint than most PVCu options.

Look for products that use Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC) accredited timber. These are two internationally recognised systems for the certification of sustainable forestry management.

Thirdly, look for thermally-efficient options with low U-values that provide environmental benefits through energy savings in the home. Aim for whole window U-values of 1.2 W/m²K or less to meet the 2025 Future Homes Standard for new builds, or 0.8 W/m²K and below  to meet ultra-low Passivhaus requirements.

What species of wood are timber windows typically made from?

Various wood types have been used to manufacture windows and doors over time. Species pass in and out of popularity for cost, availability and performance reasons. Our windows are made from pine, spruce or oak depending on the specification and customer requirements. These are selected for their durability, aesthetics and thermal insulation properties.

Laminated or engineered timber enhances stability and durability, making the windows much less prone to movement. It’s an excellent insulator – approximately 1,000 times more effective than aluminium as a raw material – and, when engineered and encased in a protective layer of aluminium cladding, a timber window provides outstanding performance with minimal upkeep.

What should you expect to budget for a high-quality window setup? 

A range of factors affect the price of your product. Clients typically pay around 10-15% more for triple-glazed units than for the equivalent double-glazed model, but the 40-45% uplift in insulation performance leads many people to consider this a worthwhile investment.

The cost of windows varies from project to project, but as a general guide you should account for up to 10% of your overall budget in a typical domestic self build. The size and shape affects its cost: curved, angled or other non-standard setups generally increase the price of a unit, and, of course, larger windows will increase your spending significantly. Big, heavy units can also impact your installation costs, often requiring specialist support.