The outer pane takes the rain, the grit and the sun. It's ordinary annealed float glass unless you ask for toughened or laminated — which we'd recommend at low level, on doors, and anywhere a child could run into it.
Argon is denser and moves more slowly than air, so it carries less heat across the gap by convection. Sixteen millimetres is the sweet spot — go wider and the gas starts circulating, which undoes the benefit.
A soft-coat low-emissivity layer, a few atoms thick, sits on the cavity side of the inner pane. Short-wave solar radiation passes straight through it. Long-wave heat radiating off your radiators hits it and bounces back into the room.
An aluminium spacer would conduct cold straight round the edge of the unit and give you condensation on the corners. Ours are warm-edge composite, with a desiccant core that keeps the cavity dry and a dual butyl/polysulphide seal that keeps the argon in.
Style is mostly about the building. We'll tell you what suits a stone-built terrace and what suits a 1990s semi — and we won't upsell you a sash window your frontage doesn't want.
The workhorse. Side or top hung, opens outward on friction stays. Best seal of any style because the sash compresses into the frame as it locks.
The sash sits level with the frame instead of proud of it, so it reads like a painted timber window. The right answer for period and conservation-adjacent properties.
One handle, two actions: tilt in at the top for secure background ventilation, or swing fully inward to clean the outside from indoors. Ideal above ground floor.
Vertical sliders with spiral balances and tilt-in sashes for cleaning. Run-through horns and astragal bars available if you're matching a Victorian frontage.
Square, splayed or five-facet bow. We check the load path first — if the bay is carrying roof above it, it gets a structural pole, not a hope.
No sash, no hardware, the slimmest sightline available and the best thermal figure on the page. Pair one with an opener next to it for ventilation.
Two identical-looking windows can perform completely differently depending on what's between the panes. Ours is written on your quote.
Sealed units made to your survey
| Element | Specification |
|---|---|
| Profile | 70mm multi-chambered uPVC, galvanised steel reinforced |
| Sealed unit | 4mm / 16mm argon / 4mm low-E, warm-edge spacer |
| Energy rating | A rated as standard, A+ and A++ available |
| U-value | 1.2 W/m²K typical whole-window |
| Locking | Multi-point espagnolette, shootbolt, internally beaded |
| Hardware | Stainless friction stays, 20 year hardware cover |
| Finishes | White, cream, anthracite grey, black, Irish oak, rosewood |
| Guarantee | 20 years on frames, units and hardware |
