Replace Windows: Energy Efficiency, Costs and Subsidies

February 3, 2022
  1. How old are your windows?
  2. How to recognise old windows
  3. 60 instead of 5-10 per cent energy saving potential
  4. Wood, plastic or metal?
  5. The special case of the skylight
  6. The advantages of new windows
  7. How much do new windows cost?
  8. Are there subsidies for new windows?
  9. Here's how to apply for your funding

In an old house or a flat with poorly insulated windows, a lot of heat escapes. Especially in winter, when you heat your home expensively. Double-glazed windows have a U-value of around 3 watts per square metre Kelvin, triple-glazed windows 0.5 or 0.6 watts. Triple-glazed windows allow much less heat to pass through the glass and insulate just as well as a solidly insulated wall. Switching from double to triple glazed windows improves the thermal insulation value by around 80%. This is why new windows are one of the simplest and most effective measures to sustainably optimise the energy efficiency of old houses or flats. New windows (frames and panes) have an energy saving potential of 5 to 10 per cent.

Houzy Hint


If it is too hot in the house or flat in summer, you need sun protection from inside and/or outside. Read our related article "Sun Protection: How to Shade Your Home and Enjoy the Sun" .

How old are your windows?

Wooden windows have a lifespan from 20 to 40 years and need to be maintained every 10 years, while plastic and metal windows last longer but need to be maintained more often. If windows have never been renovated, they will become as old as the house or flat. If they have been renovated, the year of renovation should be indicated among other things with a sticker or metal plate on the window frame. Without evidence of window renovation, the age can be estimated based on the year the house was built:

  • From the late 1970s to the mid-1990s, windows were double-glazed with insulating glass, still without a layer between the two panels.
  • From the mid-1990s to the late 2000s, windows with insulating glass were double-glazed, with a layer between the two panels.
  • Since the late 2000s, windows have a standard triple glazing with insulating glass, with a layer between the individual panels.

Houzy Hint


Hold a candle close to the glass. If the flame is reflected in the window in different colours, the glass has been coated. If you see two flames, the window is double-glazed, and if you see three flames, the window is triple-glazed.

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How to recognise old windows

If your windows still look good but you are not sure how old they are, there are two clues to see if the windows are still sealed well enough or not:

  • Look for condensation on the inside of the window. Finding condensation is not unusual, especially in winter, but it can become problematic if the humidity is constantly too high. Mould can be felt at home in damp wooden windows and doors and endangers the structure of the building and your health.
  • Are you freezing or shivering even though you have warmed up? Perhaps heat is escaping uncontrollably into the atmosphere. Ask a window fitter to check your windows with a thermal imaging camera for weak spots. Where the thermal image turns red, warm air is escaping.

Replace windows: A craftsman replaces windows in an old family home
New windows have an energy saving potential of 5 to 10 per cent. With a complete renovation you can reduce electricity consumption even further.

60 instead of 5-10 per cent energy saving potential

A window renovation has an energy saving potential of 5 to 10 per cent. However, you can only exploit the full savings potential with a comprehensive energy renovation. With a new heating system, better external insulation and modern insulating windows with an energy efficiency class A, you save around 60 per cent of electricity. This saving is well worth it sooner rather than later, because you use less electricity for heating and surcharges or long, cold winters are less of a burden on your budget. Also, after a window renovation, humidity in the house increases without a complete renovation. Afterwards, you will have to ventilate the rooms more often than before to avoid mould. After a complete renovation, the risk of mould is almost zero because the individual energy measures are coordinated with each other.

Houzy Hint


With our energy calculator you can simulate the impact of energy renovations and find out, for example, how new windows improve energy efficiency and how much electricity you save.

Wood, plastic or metal?

The choice of frames depends on your budget, your taste and your home. These are the most important characteristics of different frames:

  • Wooden frames are more expensive and need more maintenance, especially on the outside. They last 20 to 40 years and need maintenance every 10 years. Wood regrows and therefore has the best environmental balance.
  • Plastic frames are cheap and easy to maintain. They last 30 to 50 years and need to be revised every 6 to 8 years. It is better to opt for frames made of recyclable PVC.
  • Wood-aluminium or plastic-aluminium frames are easy to maintain and state-of-the-art technology. Their surfaces or aluminium shells can be painted.
  • Metal frames are usually made of aluminium. They cost more than plastic frames and are durable. They also last 30 to 50 years and need to be serviced every 6 to 8 years.

Houzy Advice

Good to know

Minergie windows cost more, but the improved energy efficiency compensates for the additional costs. The space between the panes is filled with inert gas so that heat does not escape.

The special case of the skylight

Skylights are even more exposed to wind and weather than other windows. That's why you should regularly check them for cracks and frame damage, rotten wooden frames, cracks between frame components, tarnished glass and porous or missing seals. Roof windows last more/less than 25 years and should be revised every 6-8 years as they are subject to a lot of wear and tear.

Replace windows: Mansard with skylight
Skylights are subject to increasing wear and tear, which is why you should regularly check your windows for cracks and other weak points.

The advantages of new windows

A window renovation has numerous advantages. These are just the 7 most important ones: New windows ...

  1. reduce energy consumption,
  2. minimise CO2 emissions,
  3. optimise energy efficiency,
  4. protect your assets from break-ins,
  5. protect your night's rest,
  6. improve the indoor climate and thus the quality of life; and
  7. sustainably increase the value of your house or flat.

Houzy Advice

Good to know

If you replace the windows before a façade renovation, the window installers should definitely take into account the spacing for the subsequent insulation (inside or outside).

How much do new windows cost?

Simple wooden windows are the cheapest, wooden or plastic-aluminium windows are the most expensive. Triple-glazed windows cost more than double-glazed windows. And double-hung windows are more expensive than single-hung windows. Expect to pay 400 to 600 Swiss francs per square metre of surface area for a modern triple-glazed window. Extras such as tilt and turn hinges, improved sound insulation or safety glass cost more. The work of a window fitter costs between 100 and 150 francs per hour. Also take into account the time for the journey to and from the site and the disposal of the old windows.

Houzy Advice

Good to know

With so-called renovation windows, gaps sometimes occur when old windows are torn out and new windows are installed. Ask the window installers to take care of this or hire professionals to seal them.

Are there subsidies for new windows?

No, window replacement alone is not subsidised. Window renovation is relatively simple and inexpensive. That is why many homeowners want to replace old windows first. However, if only the windows are renovated in an uninsulated house, moisture rises and accumulates as dampness in the brickwork instead of condensation on the window. This leads to mould, which attacks the structure of the building. Therefore, subsidy programmes only finance new windows as part of a complete renovation.

Replace the window: A woman fills in an online form on the computer
You can apply for subsidies online from the federal and cantonal building programme.

Here's how to apply for your funding

The Buildings Programme provides subsidies for the renovation of windows as part of general renovations (measures M-10 to M-15) or for new buildings (M-16 and M-17). It is best to proceed step by step if you want to apply for financial support:

  1. Simulate the impact of energy renovations with our energy calculator and plan the overall renovation with an expert familiar with cantonal subsidy programmes. For window renovations, it is best to talk to a regional window fitter in our network.
  2. Use the renovation plan to apply for your subsidies through the federal and cantonal Building Programme. You can simply submit your application online and check the status at any time.
  3. As soon as your application has been approved, you can start with the restructuring measures. Subsidies are only paid after the restructuring is completed.

Would you like to talk to a window fitter about a window renovation before considering a general energy renovation? In our network of experts, you will find window manufacturers in your region that we can recommend to you. You can contact up to 3 experts with just a few clicks and request free quotes.

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