If that’s your house, the maths probably feels unclear. Is upgrading worth the mess and cost, or does single glazing do the job well enough for another few winters?
We’ve fitted double glazing across Central Scotland since 1988. Weighing up glazing options usually comes down to four things: heat loss, noise, condensation and cost.
Single glazing and double glazed windows explained by Edinburgh glazing experts
What single glazing is
Single glazing means one pane of glass sitting in a window frame, with nothing else between the room and the outside air. Single glazing was standard in UK homes built before the 1970s, which is why older sash windows still rattle in a storm.
What double glazing is
Double glazing consists of two panes of glass sealed together, with a gap between them usually filled with argon or another inert gas. Double glazing uses that gas layer to slow heat transfer far more than a single pane, or even an unsealed air gap, ever could.
Good glazing provides more than warmth. It cuts noise and condensation too, covered in the sections below.
Most double-glazed windows fitted since the 1990s use this build. Today’s uPVC units go further, adding a low-emissivity coating that reflects warmth back into the room rather than losing it through the glass pane.
The type of glass used, not just the number of panes, affects how much heat and noise get through.
Double glazing vs single glazing for heat loss and energy bills
A single pane of glass has a U-value of around 5.7 W/m²K, four times higher than modern double glazing, so heat escapes faster through it.
Our standard uPVC double glazing achieves 1.4 W/m²K, dropping to 1.2 W/m²K with an upgraded spec.
Energy efficiency is where the two types of glazing differ most. The gap between 5.7 W/m²K and 1.4 W/m²K is what keeps a double glazed room noticeably warmer than a single glazed one. Your boiler runs less, and your energy bills drop with it.
Double glazing provides that improvement from the first cold snap of the year, and lower energy costs follow quickly after the switch. However you heat your home, single glazing makes the job harder for your boiler.
The saving is usually most noticeable in whichever room you heat hardest, since that’s the room losing the most heat through the glass beforehand.
Single vs double glazing for noise reduction
Single glazing does almost nothing to block outside noise. Sound passes through one thin pane of glass with barely any resistance. Traffic on a nearby road can sound like it’s coming from inside the room.
A single sheet of glass barely slows sound waves at all, but double glazing’s sealed gas gap disrupts them properly. You get a noticeable drop in noise, even without a specialist acoustic upgrade.
If road noise bothers you more than heat loss does, our windows built for noisy homes push that soundproofing further still.
Condensation on single glazed windows
Condensation forms when warm, moist air meets a cold surface, and a single pane of glass gets cold fast. Single glazed windows often stream with water on a cold morning, especially in a kitchen or bathroom.
Double glazed units keep the inner glass pane closer to room temperature, so condensation drops off considerably. It won’t disappear completely, since ventilation and humidity still matter, but the constant misting single glazing produces mostly goes away.
Left unchecked, that moisture soaks into timber frames and sills, and over time it causes rot in older single glazed windows.
What double glazing really costs vs single glazing
Single glazing costs nothing extra because it’s already there. Upgrading to double glazing means paying for the work upfront.
Compared to single glazing, the ongoing upkeep is minimal. Once fitted, double glazed windows are usually good for decades with nothing more than a seal or gasket check now and then. That holds whichever window types you’re comparing, since the U-value tells you most of what you need to know.
Our 0% finance options spread the cost rather than landing it in one lump. The cost savings from lower bills build up gradually rather than arriving all at once. The 15-year guarantee gives you peace of mind long after the invoice is paid.
If you want to go further, triple glazed units push the U-value down to 0.8 W/m²K. The jump from single glazing to standard double glazing already closes most of that gap, without the extra spend triple glazing needs.
Secondary glazing vs double glazing in older Scottish properties
Listed buildings and older tenements often fall under planning restrictions that rule out standard double glazed units on a street-facing sash window. This applies most to older buildings with original timber sash frames, since window glazing is often what earns a building its listed status.
Slim double glazing refers to a thinner profile built for exactly this problem. It fits into original timber frames without changing how the building looks from the pavement.
If your property falls into this category, the real decision is between slim double glazing and secondary glazing. Both can cut the heat loss a single glazed timber sash allows, so the right one depends on what planning will accept.
We work through this on every tenement double glazing project in Glasgow and Edinburgh, checking what the specific building allows before recommending a spec. Not every planning department treats it the same way, so it’s worth getting a straight answer before you commit either way.
Single or double glazing remains the best choice for your home
For almost every Scottish home, yes.
Single glazing offers next to no insulation, loses heat fast, does little for noise, and invites condensation that damages frames and sills over time. Double glazing solves all three, and the running costs alone usually justify the upfront price within a handful of winters.
Replacing single glazing also lifts kerb appeal, since fresh and clean uPVC frames read as newer and better kept than tired timber ones. A timber frame with flaking paint and swollen joints looks dated even when the rest of the property is well kept.
The best glazing choice still depends on how the space gets used. A low-use space, like a garden store or an unheated outbuilding, is the exception, since the investment doesn’t pay back the same way there.
Frequently asked questions
Is double glazing more expensive than single glazing?
Yes, upfront. Single glazing has no material cost because it’s already fitted. Double glazing costs more to install but pays that back through lower energy bills and a longer lifespan before replacement.
A typical quote bundles the frame, glass and fitting into one package, so there’s no separate labour charge to budget for.
What are the disadvantages of double glazing?
The main one is upfront cost, and an older sealed unit can eventually mist up between the panes if the seal fails. Beyond that, there’s little downside compared with single glazing.
Does single glazing devalue a home?
It can. A Home Report can flag single glazing as an area needing investment, and buyers sometimes use that to negotiate on price.
What’s the difference between double glazing and secondary glazing?
Secondary glazing adds a second internal window in front of the existing single glazed one, rather than replacing it. It’s often used where planning rules prevent replacing the original frame.
How much can you save by switching from single to double glazing?
It depends on the size and number of windows, your current heating use, and the specification you choose. A free survey gives you a figure specific to your property rather than a generic estimate.
How long does switching from single to double glazing take?
A straightforward home typically takes one to two days on site once the survey is done. Manufacturing the uPVC units usually takes several weeks before that, so the fitting itself is the quickest part of the process.
Get a free survey and see the difference for yourself
We’ve fitted windows across Central Scotland since 1988, and we’re rated 9.6 out of 10 on Trustpilot by more than 500 customers. Our uPVC double glazing carries a 15-year guarantee as standard.
We fit both double glazing and triple glazing windows to help increase energy efficiency of properties across the country.
Book a free home survey and we’ll measure the actual difference switching from single glazing would make to your home. There’s no obligation to book anything afterwards, and no charge for the visit either.
