Product Comparisons · 4 min read
Sliding Doors vs Bifold Doors
Sliding doors and bifold doors solve the same basic problem, a large glazed opening onto a garden, in two genuinely different ways. Neither is the automatically correct answer.
What Are the Best Windows for a Modern Extension?
Fewer, larger openings in one consistent system, with fixed glazing carrying the view and a small number of well-placed openers doing the ventilation.
3 min read
Written by Windows in the Lakes · A trading name of Home Glazing Ltd · Last reviewed 21 September 2026
Short answer
In short: a modern extension is usually best served by aluminium, by fewer and larger apertures rather than many small ones, and by a deliberate split between glass that is there for the view and glass that is there for air. Orientation then decides the glass specification.
Start with composition, not product names
The strongest contemporary extensions read as a small number of clear openings in a solid form. Before choosing a door type, decide where the building wants glass: a wide opening to the garden, a corner that catches light, a tall slot beside a chimney, a rooflight over the middle of a deep plan.
- Keep frame rhythm consistent — equal panel widths read as architecture, unequal ones read as an accident.
- Align heads across the elevation, even where widths differ.
- Use fixed glazing wherever ventilation is solved elsewhere; it is slimmer, cheaper and stronger.
- Decide whether the glazing is a hole in a wall or a wall made of glass, and commit to one.
Let orientation set the glass
| Orientation | Main risk | Usual response |
|---|---|---|
| South | Overheating and glare | Solar control glass, shading, a ventilation strategy |
| West | Low afternoon sun and heat build-up | Solar control, external shading where possible |
| North | Low daylight and heat loss | High-clarity glass, generous area, strong thermal specification |
| East | Morning glare only | Standard specification is usually sufficient |
The relationship with the original house
A contemporary extension does not have to match the house, but it does have to acknowledge it. The most reliable connection is a shared frame colour and a consistent window family carried through to any replacement windows in the original building, so the two parts read as one property with two dates.
Terms used in this guide
- Sightline
- The visible width of frame seen across a window or door — outer frame, meeting stile and any glazing bar. Slimmer sightlines mean more glass and more daylight for the same opening.
- Threshold
- The bottom section of a door frame that the door closes onto. A low or flush threshold removes most of the step but requires careful drainage and weathering detailing.
- U-value
- The rate at which heat passes through a building element, in W/m²K. A lower number means less heat loss. Window U-values may be quoted for the glass alone or for the whole window; the whole-window figure is the comparable one.
From a real Windows in the Lakes project
Near Keswick, North Lakes · Garden room extension · Two bifold runs, door and window set
A Garden Room Glazed on Three Sides
A rear extension on a terrace risks turning the original back rooms into a dark corridor, and a fully glazed box would have looked nothing like the Victorian brickwork it joins.
Brick piers and a tiled pitched roof keep the architecture in the same language as the house, while the spans between them are given over entirely to glazing. Rooflights carry daylight over the new roof and into the existing plan, and a single jet black finish across every frame, cill and handle ties the two builds together.
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