Guide to Timber Windows

If you want attractive, functional and efficient fenestration for your home, then using timber units could be the ideal choice
by Anna-Marie DeSouza
16th February 2016

From dramatic full height glazing to characterful vertically-sliding sashes, the windows you choose for your self-build or renovation will have a huge bearing on the overall aesthetic of your home, both inside and out.

Your choice will affect energy efficiency and internal comfort levels, too, which means you need to consider your property’s sustainability requirements – and how the glazing fits into the picture – right at the start of the design process.

Producing beautiful units that are eco friendly and durable to boot, timber has always been a popular choice for high-quality windows. In this article, we’ll be looking at the various options available to help you select the right product for your bespoke home building project.

Sustainability & maintenance

Around 25% of the heat lost from most homes escapes through the windows, so it’s easy to understand why the sensible choice is to opt for the most efficient units you can afford. All windows – including timber products – are energy rated on an A+ to E scale (with A+ being at the top end). This scoring system is designed to help you make an informed decision during the selection process, but most self-builders and renovators like to delve a little deeper.

The current Building Regulations require windows for new dwellings to have a U-value (a measure of efficiency) of no more than 2.0 W/m2K. Wood is a natural insulator, so when specified alongside the right glass, it should easily meet or surpass this requirement.

Many standard double-glazed timber units, fitted with low-E glass or argon gas fillings, will hit a U-value of 1.6 W/m2K or better. Upgrades such as triple glazing and krypton gas (rather than argon) will improve efficiency even further, but come at an extra cost. See our article on energy efficient windows for more advice.

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.

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.

Design decisions

Whether you are creating a modern or heritage-style 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.

Mumford & Wood sliding sash window

This made-to-order double-glazed sash window, part of the Conservation range, is factory-finished with three coats of water-based microporous paint. Available in sustainably-sourced engineered larch or Douglas fir as standard, it achieves a whole window U-value of 1.3 W/m2K. From £2,085 for the example shown, Mumford & Wood

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.

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.

Timber window costs

It’s hard to measure the cost of timber units against PVCu, for example, and get a realistic comparison. 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.

Softwood is typically the most affordable option, although it will require more maintenance than hardwoods. Most softwood units are made from larch or Douglas fir and a standard double-glazed unit at around 600mm (W) x 1,200mm (H) is likely to cost £400. This can easily rise if you’re going for high-spec glazing and other extras.

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. You can expect to pay £550-£850 for a standard 600m (W) x 1,200mm (H) unit.

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