Is there a draught from the windows, do the panes mist up between the glass layers, or do you struggle with condensation on the inside every winter? Old windows are one of the biggest heat thieves in Danish houses. Yet window replacement is one of the renovations people put off longest — because the cost seems daunting.
Here is a realistic overview of what new windows cost and when it makes sense to replace them.
What do new windows cost?
Prices depend on material, size and glass type. All prices are indicative including installation and flashings for standard sizes:
Timber/aluminium windows: 5,000–12,000 DKK each The most popular solution in Denmark. The timber core inside gives warmth; the aluminium cladding outside provides weather protection. Lasts 30–50 years with minimal maintenance. Available in almost all colours and profiles.
Timber windows: 4,000–9,000 DKK each Classic choice for older houses and listed buildings. Requires painting every 8–12 years. Lasts 30–60 years with good maintenance.
Composite windows: 6,000–14,000 DKK each Newer material with high insulating capacity and low maintenance. More expensive to buy, but no surface treatment required. Still limited range of profiles.
Aluminium windows: 7,000–15,000 DKK each Slim profiles, maximum light transmission. Primarily used in modern construction and extensions. High durability, but poorer insulating capacity than timber/aluminium unless profiles with a thermal break are used.
What affects the price?
Glass type. Modern energy glazing (triple glazing with low-emissivity coating) costs more than standard triple glazing, but significantly reduces heat loss. Energy-rated windows in class A or B give the best performance.
Size and type. A small bathroom window costs 3,000–5,000 DKK. A large facade window or double patio door can cost 15,000–30,000 DKK. Non-standard sizes are 20–40% more expensive than standard.
Number of windows. When replacing all windows in a house, most suppliers offer a volume discount. A typical detached house with 12–15 windows costs 80,000–160,000 DKK in total.
Flashings and adaptation. If the new windows fit in the existing openings, it is simplest. If the openings need to be enlarged or infilled, the price increases by 2,000–5,000 DKK per window.
Scaffolding. For windows on the first floor or gable end, scaffolding is often required — typically 10,000–25,000 DKK for a detached house.
When should windows be replaced?
Not all old windows need replacing. But there are clear signs that the time has come:
- Failed sealed units. Misting between the panes means the seal has broken. The unit no longer insulates.
- Rot in the frames. When the timber is soft and porous — especially in the bottom rail — the window’s lifespan is over.
- Single or double glazing. Windows from before 1980 with only one or two panes of glass lose enormous amounts of heat. Replacement with triple energy glazing can halve the heat loss through the windows.
- Air leakage and draughts. If you can feel air around the frame even with the window closed, the weatherstripping is worn — and the frame may have warped.
- Condensation on the inside. This indicates that the inner glass surface is too cold. Modern energy glazing has a warm inner surface that minimises condensation.
What do you save on the heating bill?
Windows typically account for 20–30% of a house’s total heat loss. Replacing older sealed units (1970–90) with modern triple glazing, you can expect:
- 15–25% lower heating consumption according to the Danish Energy Agency
- A detached house with gas heating typically saves 3,000–6,000 DKK/year
- A house with district heating saves 2,000–5,000 DKK/year
The payback period is long — 15–25 years in isolation. But new windows simultaneously provide better comfort, less noise and higher property value. And if you replace windows as part of a comprehensive energy renovation, the overall payback period falls.
Which homes are most at risk?
Detached houses from 1960–80. Many still have the original sealed units with double glazing and a narrow spacer bar. The frames are often in poor condition after 40–50 years.
Brick villas from 1920–40. Beautiful original windows, but often with single glazing. Secondary glazing is an alternative here that preserves the original look.
Terraced houses from 1970–90. Typically with large glazed sections facing south, losing a lot of heat. Replacement gives a noticeable effect on both heating bill and comfort.
Listed or conservation-designated houses. If your house is listed or conservation-designated, there may be requirements for window type and profile. Contact the municipality before ordering.
Energy rating and requirements
New windows must today comply with the requirements of BR18. This means a U-value of no more than 1.2 W/m²K for the whole window (frame + glass). The best energy windows on the market achieve around 0.7–0.8 W/m²K.
Windows are rated with an energy label from A to F — just like refrigerators and washing machines. An A-rated window actually contributes more energy through solar gain than it loses. This is particularly relevant for south-facing windows, where winter sunshine contributes to heating.
When choosing windows, ask for the whole window U-value — not just the glass. The frame and sash typically account for 20–30% of the window’s area and insulate significantly worse than the glass.
Repair as an alternative
Not everything requires replacement. Three things can extend the lifespan of windows:
- New weatherstripping. Costs 200–500 DKK per window and can be done yourself. Eliminates draughts and saves heat.
- Putty and painting. For windows with intact timber — typically 1,500–3,000 DKK per window by a tradesperson.
- Energy glazing in existing frames. If the frames are sound, the glass itself can be replaced with energy glazing for 2,000–5,000 DKK per unit.
How to move forward
Window replacement is one of those projects where it pays to think about the house as a whole. If you replace windows, it makes sense to insulate the facade at the same time — and vice versa. A comprehensive plan gives a better result and often a lower cost per measure.
Get an overview of your home’s condition and possibilities before getting quotes.
If you experience condensation on windows, it may indicate that the windows have reached the end of their lifespan — or that indoor humidity is too high. New windows combine well with insulation and facade renovation.
Sources: Bolius — window prices, Danish Energy Agency, Bygge.dk