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German renovation duties after the 2026 GEG reform

Updated: 2026-10-11 · Reading time: 13 min · ImmoLens editorial team

The Gebäudeenergiegesetz (German buildings energy act), renamed Gebäudemodernisierungsgesetz (GModG) on 29 July 2026, obliges new owners to carry out certain energy retrofits. The reform removed the best-known of them: old boilers no longer have to be replaced after a purchase. Two obligations remain, and you should know them, because they pass to you with the purchase and come with a deadline. This guide explains what applies since the reform, who can rely on grandfathering, and what it means for your price negotiation.

1. Who is affected?

The two retrofit obligations do not apply to every owner. There is an exemption that protected many older houses for decades, and this exemption ends with the sale.

Under § 35 GModG (top-floor ceiling) and § 69 (3) GModG (pipes): residential buildings with no more than two dwellings, one of which the owner lived in on 1 February 2002, are exempt. Someone who has lived in their own house since the nineties therefore does not have to insulate the ceiling or the pipes.

This exemption is, however, tied to the person, not to the building. It does not pass to the buyer. The law sets the deadline precisely: the new owner must meet the obligations within two years of the first transfer of ownership after 1 February 2002.

2. Scrapped: the mandatory boiler replacement

Until 28 July 2026, oil and gas Konstanttemperaturkessel (constant-temperature boilers) could run for at most 30 years under § 72 GEG, and a buyer had to replace such a boiler within two years of the purchase. This obligation no longer exists. The Gebäudemodernisierungsgesetz deleted §§ 71 to 73, and with them the end date of 31 December 2044 for fossil heating. An old boiler may keep running as long as it works and the usual operating duties (maintenance, flue-gas values, chimney sweep) are met.

That does not make an old boiler free. It burns noticeably more fuel than a modern system, spare parts get scarce, and if it fails in winter you have to decide under time pressure. For the purchase decision, the heating has turned from a legal issue into a cost issue: if the boiler is older than 20 to 25 years, budget for a replacement in the coming years, but not as a legally enforced expense.

3. Obligation 1: Insulating the top-floor ceiling (§ 35 GModG)

The top-floor ceiling, i.e. the ceiling below an unheated loft, must be insulated so that its thermal transmittance does not exceed 0.24 W/(m²·K). Depending on the material, that means roughly 14 to 20 centimetres of insulation. Deadline after a change of ownership: two years (see section 1). Until July 2026 the same rule stood in § 47 GEG.

The obligation is also met if the roof above is insulated accordingly instead of the ceiling, or if the roof meets the minimum thermal insulation under DIN 4108-2. If you have a converted, insulated loft, you do not need to do anything.

4. Obligation 2: Insulating the pipes (§ 69 GModG)

The second obligation is the least known and the cheapest. Under § 69 (2) GModG, previously uninsulated, accessible heat distribution and hot-water pipes that do not run through heated rooms must be insulated. This means the pipes that typically run along the cellar ceiling. New since July 2026: buyers get the same two-year rule as for the ceiling (§ 69 (3) and (4)), including the misunderstanding from section 1.

The required thickness is set out in Annex 8 and depends on the pipe's inner diameter (based on an insulating material with 0.035 W/(m·K)):

Material and effort are small: pre-slit insulating sleeves from a DIY store cost around €5–15 per running metre if you fit them yourself. For a typical cellar that adds up to €200 to €500. Hardly any other obligation can be dealt with so quickly and cheaply.

5. If you replace the heating: what applies now

If you need to replace the heating at some point, you have a free choice since 29 July 2026: heat pump, district heating, biomass, a hybrid system, or another gas or oil boiler (§ 42 GModG). The former 65 percent rule and its link to municipal heat planning no longer exist.

A new gas or oil boiler installed after 29 July 2026 is, however, subject to the Bio-Treppe (§ 43 GModG): a rising share of the heat must come from carbon-neutral fuels such as biomethane, bio heating oil or green hydrogen.

Carbon-neutral fuels cost more than natural gas and heating oil, so the running costs of a new fossil boiler rise with every step. If you replace the heating today, compare it against a heat pump. Important for funding: the KfW heating grant (KfW 458) is still only available for systems with at least 65 percent renewable heat. Since the reform, what the law allows and what gets funded are two different questions.

6. No obligation: facade, windows, cellar

Contrary to a widespread belief, a change of ownership does not trigger any duty to insulate the facade, replace the windows or insulate the cellar. If you buy a house with windows from 1985, you may keep them as long as you like.

Requirements only arise when you renew the component anyway. Then § 36 GModG (formerly § 48 GEG) applies: the new component must meet the maximum values in Annex 7. The de minimis threshold in the same section matters: changes affecting no more than 10 percent of the total area of the component group are exempt. Replacing two out of twenty windows therefore triggers no requirement. Reglazing the entire south side does.

7. Enforcement, fines and exemptions

Compliance is checked by the authorised district chimney sweep, who visits for the regular inspection anyway. If they find a breach, they set a deadline for remedying it. If nothing happens, the case goes to the responsible authority.

§ 108 GModG treats breaches as an administrative offence subject to a fine. For the ceiling (§ 35 (1)) and the pipes (§ 69) the range goes up to €50,000. That is the legal maximum, not the norm: in practice, fines for a single family home are considerably lower. Do not rely on that, though, because the fine does not replace the obligation, it comes on top.

There are two ways out. § 102 GModG allows an exemption in cases of hardship if the requirements lead to unreasonable effort or undue hardship in the individual case. The application goes to the responsible state authority, usually the lower building authority. In addition, § 35 itself contains an economic viability exception: the insulation duty does not apply if the expenditure cannot be recouped through the resulting savings within a reasonable period. Both are case-by-case decisions, not a free pass.

8. Retrofit obligations and heating age in the price negotiation

Since the reform, the legally enforced costs of buying a house are small: ceiling and pipes together usually cost a few thousand euros. The bigger topic is the heating, not as an obligation but as a foreseeable expense. A 30-year-old oil boiler no longer has to go, but in all likelihood it will in the next few years, and that belongs in the negotiation.

A solid negotiating position rests on three figures: the cost, the maximum achievable funding and your remaining share. For the obligations, the deadline also counts; for the heating, its age and condition, documented by the chimney sweep's report. Both belong on the table, ideally with two contractor quotes. For a major refurbishment to efficiency house standard, KfW programme 261 also offers a loan of up to €150,000 per dwelling; since the BEG reform of 21 July 2026 the repayment grant is 0 to 10 % depending on the level, plus bonuses for worst performing buildings and serial refurbishment.

Sources and status

Status: 11 October 2026. Checked against the promulgated text in the Federal Law Gazette 2026 I No. 226 (act of 23 July 2026; Article 1 in force since 29 July 2026, Article 2 from 1 January 2027), in particular Article 1 No. 15 (§§ 46, 47 become §§ 34, 35), No. 30 (§ 69 (3) and (4)), No. 32 (deletion of §§ 71 to 73) and No. 51 (§ 108). An overview is available on the federal government's GModG portal . Only the promulgated text is binding.