Window replacement in old buildings: planning, costs, and funding opportunities

Why is window replacement so important in older buildings?

Windows play a key role in energy efficiency and quality of living in older buildings. Many existing buildings still have windows from the 1970s, 1980s, or early 1990s, whose thermal insulation no longer meets today's requirements. While old glazing is often the weak point of a facade in terms of energy efficiency, modern systems function as high-performance components.

A professionally planned window replacement in an old building results in:

• Reduced heat loss: Old windows (often still with single glazing) have U-values of over 2.0 W/(m²K). Modern triple glazing achieves values of 0.5 to 0.9 W/(m²K). This not only significantly reduces heating energy requirements, but also protects the environment through lower CO₂ emissions.

• Greater living comfort: Drafts caused by worn seals disappear. The surface temperatures on the inside of the panes increase significantly, making unpleasant “cold radiation” and the formation of cold air pools on the floor a thing of the past.

• Improved sound insulation: Especially in inner-city locations or on busy roads, old buildings benefit enormously from modern soundproof glazing. Different glass thicknesses and special composite films massively reduce ambient noise.

• Increased burglary protection: Old windows in older buildings can often be pried open in seconds. New models offer a contemporary security standard thanks to mushroom head locks, impact-resistant glazing, and lockable handles (resistance classes such as RC2).

• Prevention of moisture damage: Professional installation in accordance with RAL guidelines ensures that the connection joints are airtight. In combination with a coordinated ventilation concept, this prevents condensation and mold in the reveal area.

• Increased property value: Replacing windows in old buildings improves energy efficiency class in the energy performance certificate and increases the long-term attractiveness of the building – both for owner-occupancy and for rental or sale.

What needs to be considered when planning a window replacement in an old building?

Replacing windows in old buildings differs fundamentally from doing so in new buildings. Existing wall structures, uneven reveals, and varying insulation standards require careful coordination. The basis of any window replacement guide is an energy assessment of the existing building. If the U-value of the existing windows is above 2.0 W/(m²K), replacement is almost always advisable from an energy and economic perspective.

Key aspects to consider when planning:

• Check subsidy options: Window replacement is often eligible for substantial subsidies. Important: The subsidy application must be submitted before commissioning the craftsman

• Coordinating windows and walls: The insulation value of the window should be optimally matched to the exterior wall. If the window is “too tight” for an uninsulated wall, the dew point shifts, which increases the risk of condensation and mold on the walls.

• Consider ventilation concept: Unlike older models, modern windows close hermetically. A well-designed ventilation concept (e.g., using window rebate ventilators or a decentralized ventilation system) is essential for removing moisture.

• Installation according to RAL standard: In older buildings, sealing the joints to the masonry is critical. The principle of “inner sealing tighter than outer sealing” applies here to prevent warm indoor air from penetrating the structure and condensing there.

• Material selection and monument protection: In historic buildings, monument protection requirements (e.g., narrow profiles, genuine glazing bars) often have to be observed. Modern wood or wood-aluminum windows offer the best combination of aesthetics and technology.

• Involvement of an energy consultant: A certified expert analyzes the overall situation. This is not only technically advisable, but also mandatory if government subsidies (e.g., from BAFA or KfW) are to be claimed.

Step by step: How to plan window replacement in an old building correctly?

A structured process helps to avoid mistakes and implement the renovation efficiently. Especially in existing buildings, details determine the long-term success of the measure:

Step 1: Inventory analysis and consultation

Before replacing windows, the age, condition, and insulation values of the existing windows should be determined. Windows built before 1995 are generally outdated in terms of energy efficiency. An energy consultant can check whether replacing the windows as a single measure is sufficient or whether it makes more sense to do so as part of a package (e.g., with facade insulation).

Step 2: Choose the right window type and material

Old buildings offer creative freedom – the choice of material influences the appearance, maintenance requirements, and price:

• Wooden windows: Ideal for preserving the historic character, but require intensive maintenance.

• Wood-aluminum windows: Combine the warm appearance of wood on the inside with maximum weather resistance thanks to an aluminum shell on the outside.

• Plastic windows: Offer high energy efficiency at an attractive price-performance ratio and are particularly easy to maintain.

• Special solutions for listed buildings: Listed properties often require narrow face widths or special fittings.

Step 3: Assess mold risks and ventilation

Replacing windows in old buildings significantly improves airtightness. Without adjusted ventilation behavior, humidity increases.

• Ventilation concept: A specialist should check whether window rebate ventilators or decentralized ventilation with heat recovery need to be integrated.

• Dew point check: It must be ensured that the wall reveal does not become the coldest point where moisture condenses.

Step 4: Obtain quotes and secure funding

Before signing the contract, you should obtain comparative quotes:

• Important: If you want to receive government subsidies (e.g., 15% plus a 5% bonus for renovation roadmaps), you must submit the funding application together with an energy efficiency expert (EEE) before hiring the tradespeople.

Step 5: Measurements and professional installation

Precision measurements are crucial in old buildings, as walls are often not exactly straight:

• RAL installation: According to the Building Energy Act (GEG), an airtight window connection joint is mandatory. Installation is carried out according to the principle of “inside tighter than outside” to prevent moisture from penetrating the insulation layer of the joint.

What costs can you expect when replacing windows in an old building?

The costs for replacing windows in an old building are made up of several factors. Unlike in new buildings, they vary greatly depending on the condition of the existing masonry, the accessibility of the construction site, and the energy requirements.

Every project is unique, especially in existing buildings. The age of the building, the facade structure, existing connection situations, and the desired level of equipment have a significant influence on the investment amount. Flat-rate price quotes are therefore only of limited use.

The most important factors influencing the investment:

• Frame material: Plastic systems are considered an economical solution with very good insulation values. Wood or wood-aluminum systems are more complex in terms of construction and offer additional design and technical features, which has a corresponding effect on the investment.

• Glazing: Modern triple thermal insulation glazing significantly improves the energy efficiency of the building. Additional functions such as soundproofing or sun protection glazing increase the technical performance and change the system structure.

• Installation effort: In old buildings, existing windows often have to be carefully removed from the masonry without damaging adjacent components. Depending on the condition of the building, additional work on reveals, plaster, or facades may be necessary. The amount of craftsmanship required is therefore usually higher than in new buildings.

• Additional functions: Increased burglary protection, special sound insulation solutions, integrated insect screens, or special comfort features influence the quality of the fittings and thus the overall investment.

Individual budget planning for older buildings

The investment required for window replacement depends heavily on the condition of the building, window size, level of fittings, and regional conditions. Large elements, solutions that comply with historic preservation requirements, or complex facade connections increase the technical and craftsmanship effort involved.

For realistic budget planning, it is therefore advisable to seek individual advice from a qualified specialist company. This is the only way to sensibly coordinate energy requirements, structural features, and design preferences.

Subsidies for window replacement in older buildings: making good use of funding opportunities

The government provides targeted support for energy-efficient renovations, as modern windows make a significant contribution to climate protection. Attractive subsidy programs are also available for window replacement in old buildings, which significantly reduce the actual financial burden.

There are three main subsidy options:

• BAFA subsidies: Through the Federal Office of Economics and Export Control, you can receive subsidies of 15% for individual measures on the building envelope. If the window replacement is included in an individual renovation roadmap (iSFP), the subsidy even increases to 20%. Since the costs in older buildings are often higher due to installation, this option is particularly worthwhile: if the windows achieve a U-value of 0.95 W/(m²K) or better, you will receive a subsidy for the total costs, including installation.

• KfW programs: The Kreditanstalt für Wiederaufbau (KfW) offers low-interest loans and supplementary loans, especially if the renovation achieves a certain energy efficiency standard.

• Tax incentives: As an alternative to direct payment, you can deduct up to 20% of the costs over three years, provided you do not claim any other subsidies.

  Important: To ensure you do not lose out on any money, it is essential that you submit your subsidy application before commissioning the window manufacturer. In most cases, it is also mandatory to involve a certified energy consultant to ensure technical accuracy and eligibility for subsidies.

Which windows are suitable for window replacement in old buildings?

When replacing windows in old buildings, choosing the right windows plays a decisive role in the success of the renovation project. The new windows should not only increase the energy efficiency of the building, but also match the architectural character of the old building. Various factors need to be taken into account, from thermal insulation and soundproofing to appearance and choice of materials. The choice of window type should always be tailored to your individual needs and the condition of the building. Make sure that the new windows meet energy requirements while preserving the charm of the old building.

• Wooden windows: Wooden windows impress with their traditional appearance, good thermal insulation, and high sustainability. As a natural material, wood blends harmoniously into historic facades and enhances the original character of a building. Suitable for: Listed buildings and historic old buildings.

• Wood-aluminum windows: These systems combine the warm appearance and insulating properties of wood on the inside with a weather-resistant aluminum shell on the outside. This creates a durable, low-maintenance solution with high resistance to environmental influences.

• Suitable for: Old buildings with high comfort requirements and a focus on durability.

• PVC windows: PVCwindows offer very good insulation values, are easy to maintain, and are technically sophisticated. They enable economical modernization while meeting high energy requirements. Suitable for: energy optimization and projects with a clear focus on investment efficiency.

• PVC-aluminum windows: This variant combines the good thermal insulation properties of plastic profiles with a robust aluminum outer shell. The result is a modern look combined with high durability. Suitable for: older buildings where a modern design mix is desired.

• Aluminum windows: Aluminum windows are characterized by extreme stability and particularly filigree profile views. They are ideal for large glass surfaces and clear, minimalist facade designs. Suitable for: modernized old buildings with minimalist architecture and large window openings.

Replacing windows in old buildings with Salamander myWindow

To ensure that a renovation preserves the charm of an old building while also meeting modern energy standards, the window solutions must be flexible and high-performance. Salamander myWindow offers specialized systems that have been specifically developed for the challenges posed by existing buildings – from historic preservation to rigorous energy-efficient renovation.

Salamander myWindow window solutions stand for:

• C3 principle: customized system selection through analysis of location, building type, and orientation

• Window configurator: find the ideal window in just a few steps – tailored to the existing structures, aesthetics, and energy requirements of your old building

• Bionic insulation: maximum thermal insulation with minimal construction depth thanks to proEvolution – ideal for preventing mold growth in old buildings

• evoCore core: stable recycled core instead of heavy steel for lighter windows and insulation values at passive house level

• Sound and burglary protection: modern upgrade to up to 48 dB sound reduction and security classes up to RC3

• Design variety: narrow profiles for maximum light incidence, combinable with authentic surfaces such as Greta® or realMaterial

• Genuine sustainability: resource-saving renovation with systems made from up to 100% recycled materials

• Digital simulation: advance check of energy effects directly on the property via the myWindow_App

FAQ – Answers to your questions about window replacement in old buildings

Do you still have questions about window replacement in existing buildings? We provide informative answers to the most frequently asked questions to ensure that your renovation project in an old building is a complete success!