In the energy performance certificate, energy efficiency class (Energieeffizienzklasse) H stands for the worst rating a residential building can receive. Houses in this class consume a lot of energy, cause high heating costs and are increasingly in the focus of buyers and banks when sold. Anyone who owns or inherits such a house quickly asks what an energy-efficiency renovation costs and what improvement is realistically achievable. In Düsseldorf and throughout North Rhine-Westphalia, we have supported owners with their property for over 60 years and regularly value renovated as well as unrenovated objects. This guide explains what class H means, which measures come into consideration, what cost ranges you should expect, what obligations the Buildings Energy Act (GEG) provides for, and how a renovation affects the value.
What Energy Efficiency Class H Means
The energy performance certificate classifies residential buildings into classes from A+ to H. According to Annex 10 of the Buildings Energy Act (GEG), the decisive factor is the final energy demand or final energy consumption in kilowatt-hours per square metre of usable building area per year.
Class H is the worst level. It begins at a value of more than 250 kWh/(m²·a) and is open-ended. By way of comparison: a new build often reaches class A or B with less than 75 kWh/(m²·a). A class H house therefore consumes many times more energy.
- A+: up to 30 kWh/(m²·a)
- A: up to 50
- B: up to 75
- C: up to 100
- D: up to 130
- E: up to 160
- F: up to 200
- G: up to 250
- H: over 250
Class H typically applies to older buildings that have never been modernised in energy terms, such as unrenovated single- and two-family houses from the period before the first Thermal Insulation Ordinance of 1977. Uninsulated exterior walls, old windows, an inadequately insulated roof and an outdated heating system often come together here.
Why Class H Houses Cause High Costs
The high energy demand of a class H house is directly reflected in the running costs. In winter, a lot of heat is lost through uninsulated components, so the heating system has to work harder permanently. Depending on the energy source and market price, the annual heating costs can therefore be significantly higher than for a renovated house of comparable size.
In addition, there is the need to renovate the building fabric itself. Where little has been invested over decades, several components are often at the end of their service life at the same time. Typical weak points are:
- uninsulated or only thinly insulated exterior walls
- single- or double-glazed windows with leaky frames
- an uninsulated roof or an uninsulated top-floor ceiling
- an uninsulated basement ceiling
- an old, fossil-fuelled heating system with low efficiency
These factors are interdependent: a new heating system alone achieves little if the heat escapes through the building envelope. An effective improvement of class H is therefore generally achieved through a coordinated package of measures.
Typical Measures for Improvement
An energy-efficiency renovation addresses the building envelope and the building services. Which measures make sense depends on the condition of the individual building. The following combination is common:
- Facade insulation: usually as a thermal insulation composite system, alternatively as a rear-ventilated curtain facade. The greatest lever in the heat transition through the wall.
- Insulation of the roof or top-floor ceiling: reduces upward losses, often the most economical single measure.
- Insulation of the basement ceiling: lowers downward losses and improves comfort on the ground floor.
- Window replacement: modern triple glazing replaces old windows and closes thermal bridges.
- Heating replacement: replacement of the old fossil heating system, often by a heat pump (Wärmepumpe), provided insulation and heating surfaces are suitable.
- Ventilation with heat recovery: ensures air exchange after insulation and prevents moisture damage.
The order is not arbitrary. It usually makes sense to upgrade the envelope first and then size the heating system accordingly. An individual renovation roadmap helps to coordinate the steps with one another.
Cost Benchmarks: Individually and for a Single-Family House
The following ranges are benchmarks for a detached single-family house and vary considerably depending on size, condition, region and execution. They do not replace a specific quotation.
- Facade insulation (thermal insulation composite system): around 100 to 250 euros per square metre; for a single-family house often roughly 15,000 to 40,000 euros
- Roof or top-floor ceiling: about 50 to 150 euros per square metre, with the non-accessible top-floor ceiling at the lower end
- Basement ceiling: around 25 to 80 euros per square metre
- Window replacement (triple glazing): roughly 500 to 800 euros per window including installation, depending on size and frame material
- Heat pump (air-to-water) including installation: about 15,000 to 35,000 euros, depending on building and heating surfaces
- Ventilation system with heat recovery: around 8,000 to 20,000 euros, depending on a central or decentralised system
For a comprehensive energy-efficiency renovation of an unrenovated class H single-family house, these measures often add up to an order of magnitude of about 50,000 to 150,000 euros. With a very poor starting condition or high comfort requirements, the amount can be higher. If several trades are bundled, scaffolding, planning and travel can be used jointly.
Realistic Class Jumps
How much the efficiency class can be improved depends on the scope of the measures. Individual steps usually raise the building by one or two classes; a coordinated overall package can enable the jump from H into the middle range.
- A single measure such as roof insulation or window replacement: improves the value noticeably, but often raises the class by only one level.
- Envelope plus heating replacement in combination: a clear jump is possible, often towards classes D to C.
- Renovation to efficiency-house standard with high-quality insulation, heat pump and ventilation: classes B or A are achievable, but require the greatest effort.
The class actually achieved can only be calculated reliably after a survey by an energy consultancy, since it depends on the interplay of all components. Blanket promises about a particular class jump are not possible.
GEG Obligations and Funding
The Buildings Energy Act contains requirements that become relevant precisely for old class H houses. On a change of ownership, certain retrofitting obligations apply to single- and two-family houses, which generally have to be met within two years. These include insulation of the top-floor ceiling or the roof, provided minimum thermal protection is not met, and insulation of accessible heating and hot-water pipes in unheated rooms.
For heating systems, GEG § 47 sets an operating ban for certain old constant-temperature boilers, which as a rule may not be operated for longer than 30 years. GEG § 71 requires that newly installed heating systems be operated with at least 65 percent renewable energy; the deadlines for existing buildings depend on municipal heat planning.
For funding, the Federal Funding for Efficient Buildings (BEG) is available. As of mid-2026, the following serve as reference points:
- Single measures on the building envelope (BAFA): 15 percent basic funding, with an iSFP bonus from an individual renovation roadmap a further 5 percentage points. The eligible costs rise with the iSFP from 30,000 to up to 60,000 euros per residential unit.
- Heating replacement (KfW grant 458): 30 percent basic funding, supplemented by possible bonuses; in total up to 70 percent is achievable, with eligible costs of up to 30,000 euros for the first residential unit.
- Loan for efficiency-house renovation (KfW 261): low-interest loan with a repayment subsidy depending on the efficiency-house level achieved.
Funding programmes are budget-dependent and are adjusted regularly. The current guidelines of BAFA and KfW are always decisive and should be checked shortly before applying. Applications generally have to be submitted before the measure begins.
Economic Viability and Effect on Value
Whether a renovation pays off depends on several factors: the energy costs saved, the funding used, the condition of the components and whether repairs are due anyway. Insulation of the top-floor ceiling often amortises faster than complete facade insulation, because it is inexpensive and effective. Measures that replace work that is due anyway are generally more economical than purely energy-motivated interventions.
Beyond energy costs, the efficiency class increasingly affects the market value. Today, buyers factor in the expected heating costs and the need for renovation. A class H house can be sold, but is often traded with a price discount because the buyer has to take on the renovation. A renovation carried out or a well-documented possible renovation can improve the negotiating position.
Whether a renovation before the sale is worthwhile, or whether selling in the current condition makes more sense, can only be assessed for the specific property. Both paths are possible, and the market in Düsseldorf and North Rhine-Westphalia values location and fabric differently. A factual assessment of the value before and after a renovation provides the basis for the decision.
