Velux Window Prices: What Affects the Cost

Window size

Roof windows come in a range of standard sizes. Larger windows cost more and, if they are wider than the spacing between rafters, need the roof timbers trimming to make the opening.

Type of window

Centre-pivot windows are the most common. Top-hung windows, conservation-style windows with slim frames, and electric or solar-powered units all cost more. A fixed window that does not open is usually cheaper but gives no ventilation.

Glazing

Standard double glazing is the baseline. Triple glazing, noise-reducing glass, or laminated safety glass for a bathroom or a window over a stairwell all add to the price.

Flashing kit and roof covering

Each window needs a flashing kit to seal it to the roof. Kits for slate are different from those for profiled tiles, and recessed installations need specific kits. Fitting into a slate roof often takes a little longer because the slates are cut and dressed around the frame.

Replacing or adding a new opening

Replacing an existing roof window of the same size is usually the simplest job. The old unit comes out and the new one goes in, with a new flashing kit.

Creating a new opening involves cutting into the roof, trimming rafters, fitting the frame and forming the inside lining and plaster reveals. That is more work and costs more. Planning rules may apply in some cases.

Planning permission and building regulations

Interior finishing

Inside, the opening needs lining, insulating and plastering, and sometimes decorating. Some quotes include this and some do not, so check what is included.

Accessories

Blinds, shutters and remote controls are extras. Blackout blinds are popular for bedrooms, and heat-protection blinds help in rooms that face the sun.

Access

A window on a single-storey extension can often be fitted from a ladder or platform. One on a three-storey roof may need scaffolding. Access can make a large difference to the total.

Loft conversions

In a loft conversion, roof windows are often one part of a bigger project. Building regulations may require a window big enough to serve as an escape route, and minimum glazing for light and ventilation. Those requirements can influence the size and type of window, and so the price.

Number of windows

Fitting two or more windows at the same time is usually more efficient per window than fitting them separately, because access and set-up are shared. Coupled windows, side by side or one above the other, need combination flashing kits.

Roof condition

If the roof covering around the new window is in poor condition, there may be extra slates or tiles to replace. Fitting a roof window during a re-roof is often the most efficient time, because the covering is coming off anyway.

Electrics

Electric or solar windows are easier to open when out of reach. Electric versions need a power supply run to the window, which may need an electrician. Solar versions avoid wiring but cost more to buy.

What to check in a quote

Make sure the quote states the window size and type, the flashing kit, whether the opening is new or a replacement, interior finishing, blinds and access. Comparing those items side by side is the fairest way to judge quotes.

Planning and building regulations

Most roof windows on houses fall within permitted development, but flats, listed buildings and conservation areas are different. Building regulations may apply to new openings and loft rooms. Checking early avoids delays and extra costs later.

Ventilation and condensation

A roof window can help ventilate a loft room or bathroom. Choosing a window with a ventilation bar, or one that is easy to open, helps reduce condensation. That can influence the model chosen, and so the price. Our roof ventilation page explains more about airflow in roof spaces.

Finally, think about where the window will be most useful. A window positioned to light a staircase, a desk or a bathroom mirror often gives more value than a larger one in the wrong place, and the right position can sometimes avoid trimming extra rafters.

Roof ventilation

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