Choosing windows for warmth and noise reduction

Why windows matter so much here

Edinburgh and the Lothians throw a lot at a window. You have the west wind coming off the Forth, driving rain in coastal spots like Portobello and Musselburgh, and tenement flats where one wall of glass faces a busy road. Add the traffic on corridors such as Gorgie Road, Leith Walk, Morningside Road and the A90 approach, and a single-glazed sash becomes both a heat leak and a loudspeaker.

Most homes here still have original sash and case windows, and many are lovely. They were built for a different era of coal fires and cheap fuel, though. If you are cold in the front room and can hear every bus from the back bedroom, upgrading the glazing is usually the single most effective improvement you can make. The good news is that you do not need to rip out good timber to get results — but you do need to know what you are buying.

The numbers worth knowing before you shop

Two figures do most of the work when comparing windows. The first is the U-value, which measures heat loss. Lower is better, and it applies to the whole window, not just the glass. A typical modern double-glazed unit sits around 1.2 to 1.6 W/m²K; good triple glazing can reach 0.8 to 1.0. A single-glazed sash is closer to 5.

The second is Rw, the weighted sound reduction index, measured in decibels. It is not intuitive. An improvement of 3 dB is barely noticeable, 5 dB is clearly audible, and 10 dB sounds roughly like halving the noise. A standard double-glazed unit gives you around 28 to 32 dB. Acoustic units can reach 35 to 40 dB, and well-fitted secondary glazing can match or beat that.

Bear in mind that these laboratory figures assume a perfect seal. In the real world, a gap under a sash or an unfilled cavity around the frame will undo much of the benefit. Fitting quality matters as much as the spec sheet.

Choosing for warmth

• Double vs triple. Triple glazing performs better and feels warmer next to the glass, but the units are heavier and thicker, which can mean wider frames and more work in older reveals. In a tenement, deep reveals often suit triple well; in a slim Victorian sash, it may not fit without altering the frame.
• Gas fill and spacers. Argon or krypton between the panes cuts heat loss. A warm-edge spacer — the strip separating the panes at the edges — reduces the cold bridge where condensation tends to form. Cheap units skimp here.
• Frame material. Timber has natural insulating value; uPVC and aluminium need internal thermal breaks to compete. Aluminium is durable and slim but conducts heat unless properly broken.
• Do not overlook the edges. Heavy lined curtains, thermal blinds and repaired shutters add real comfort on winter evenings, especially in rooms you only use occasionally.

Cutting traffic noise

Soundproofing works on two principles: mass and separation. More mass in the glass, and more air or a different medium between the panes, means more noise stopped.

• Laminated glass. A plastic interlayer between two sheets of glass is far better at blocking road noise than ordinary glass of the same thickness. Ask specifically for acoustic laminate.
• Mismatched pane thicknesses. Using 4 mm on one side and 6 mm or 8 mm on the other avoids the point where both panes vibrate at the same frequency and let a particular tone through.
• Air gap. Around 16 to 20 mm works well for standard units. Very wide gaps behave differently again, which is why secondary glazing with a 100 mm gap is so effective.
• Seals. Compression seals on the opening sash, brush seals on sliding sashes and draught-proofing on the meeting rail are where many installations fail. If you can feel air, you can hear noise.
• Ventilation. Every home needs background ventilation, and trickle vents are the usual weak point. Acoustic trickle vents exist and are worth specifying on a noisy elevation.

Old buildings, listed status and conservation areas

Much of central Edinburgh sits within the World Heritage Site, and there are conservation areas across the city and into East, Mid and West Lothian. Listed buildings normally need listed building consent for window alterations, and conservation areas can require permission for certain changes, particularly to uPVC or to the external appearance of a frontage.

In practice, the accepted route for historic sashes is usually: repair and draught-proof the existing frame, then add slim-profile double glazing or well-made secondary glazing inside. This keeps the external character, retains the original glass where it matters, and delivers most of the thermal and acoustic gain. Speak to the council's planning team before you order anything — a short conversation early saves a great deal of money later. If you share a tenement close, remember that common repairs and mutual walls may mean involving neighbours and your factoring arrangements.

Getting the installation right

The best windows in the world will underperform if they are fitted badly. Watch for these during the work:

• The gap between frame and masonry is insulated and sealed, not just covered with trim.
• Sills drain properly and water runs away from the wall.
• Opening lights close with even compression all round, not just at the handle.
• Any making good is done before the final seal, so nothing is bridged or left open.

Ask about certification schemes covering the installer, and about guarantees — ten years or more, ideally insurance-backed. Get at least three itemised quotes and make sure the U-value and Rw figures are written into them, along with the glass make-up. If budget is tight, a very sensible strategy is acoustic double glazing on the noisy, road-facing elevation and standard triple or good double elsewhere. That way your money lands where you will actually notice it, every cold morning and every rush hour.