Glazed facades and large windows have long been popular in commercial building design, but the move to contemporary, unfussy windows is now firmly on-trend in the domestic market.

Windows continue to grow in size while frames, often in a dark tone, diminish, with glazing units offering large unobstructed views. The style is unashamedly modern while the shapes remain traditional – just much bigger.

With regional and national house-builders now embracing large apertures, often for selective and prestigious developments, it’s a trend that looks set to stay.

Yet, with consumers demanding more glass, less frame and bigger and better windows, this must be balanced with budget and feasibility.

Structural requirements

It’s no surprise that large windows and doors require extra structural support. This is something that has to be factored in at the design stage and is vital for a precise fit and long-term performance. We would recommend that architects and specifiers get on board with their window supplier as early as possible to capitalise on their expertise. By working together, a viable and budget-conscious solution can be achieved, without compromising on structural integrity.

The supplier should be aware of everything. We often work with architects to assess the site before the specification is finalised. This allows us to head-off any potential issues early in the design process.

A typical site assessment would include the location, altitude, position in relation to the coast, wind speed, building height and frame/glazing size required. The wind load is also calculated, allowing the most appropriate profile and glass to be selected.

Practicalities of installing big windows

One of the challenges of large glazed units is the risk associated with handling and installation. For manual lifting, the Health & Safety Executive states: “The law does not identify a maximum weight limit. It places duties on employers to manage or control risk; measures to take to meet this duty will vary depending on the circumstances of the task. There is no universally safe maximum weight for any load; however, there are varying degrees of risk”.

Mechanical versus manual lifting is; therefore, determined by the size and weight of the glazed product, and at the discretion of the client, contractor or supplier/installer. For example, a Sky-Frame horizontal sliding window measures 3.2 x 4m (larger on request) and weighs around 640kg, so mechanical lifting equipment would be required by the fitting team. A nominal figure of £1000 should be budgeted for the hire of mechanical lifting equipment.

The weather is also a critical factor, especially wind speeds. A risk assessment would be advisable prior to the installation, to determine how and if the lift should go ahead.

Solar gain

When specifying windows for large apertures, solar gain must be factored in. This is a particular consideration for glass on south-facing elevations. Most window fabricators control solar gain through high-performance glazing, with glass manufacturers offering a wide selection of glass options including coated and uncoated. Solar control glass, for example, can help retain heat in cooler months.

When specifying solar control glass, consider the g-value – the measure (in percentage terms) of how much solar heat is allowed in through a building material or product, e.g. a window. The g-value of standard double glazing is typically 64%, whereas certain types of solar control glass can reduce the solar gain down to 28%.

While specialist glass is one solution, architects and designers can also address solar gains by considering the location and orientation of the building during the planning stage, especially the shading benefits of neighbouring buildings and trees.

The right information

For an efficient and positive build, relevant and accurate information should be shared early in the design process. Window manufacturers benefit from detailed and precise section drawings of what is to be constructed. This isn’t a requirement as this can be picked up later in a site survey, but good construction drawings certainly lead to the best finish and results, on site.

Elevations or plans of the basic system or style required is essential for generating a detailed quotation. This is particularly important for those working to a specific budget.

Many window companies will offer support at the design stage, often providing full technical drawings showing the product integrated into the building.