Energy report for a renovation – when does a renovation need one, and what does the law really require?

A housing company’s board is planning a window renovation, or a detached house owner is considering extra insulation on the facade and a new heating method. At some point the question comes up: does the renovation need an energy report, and does the whole house now have to reach new-building level? The reassuring answer first: the energy efficiency requirements apply only to the parts you renovate – the whole house does not have to be raised to class A. In this article we go through when a renovation brings energy requirements with it, what the law really requires, and how the requirements are met. The same topic from the point of view of someone building a new house is covered in the article energy report for a building permit.

When does a renovation need an energy report?

Energy efficiency requirements only come into play when the repair or alteration work requires a building permit (rakentamislupa) or when the building’s use changes. Under the Building Act (rakentamislaki), a permit is always required if repair or alteration work on the building envelope or technical systems can significantly affect the building’s energy efficiency. The envelope means the external walls, the roof structure (yläpohja), the base floor, the windows and the external doors; technical systems include, for example, heating and ventilation. A permit is also always required for drilling an energy well.

Typical projects in which a permit and energy requirements come up:

replacing the windows and external doors throughout the building
renewing the facade or adding insulation to it
adding insulation to the roof structure as part of a roof renovation
changing the heating method, for example from oil to ground source heat
renewing the ventilation system
a change of use, for example converting an attic into a dwelling.

The need for a permit is always decided by the municipal building control authority, and practices vary between municipalities, so ask them at the planning stage. Since the start of 2026, an energy report is no longer a mandatory attachment to every permit application: building control can request it based on the nature and scope of the project. The measures that improve energy efficiency must nevertheless be presented as part of the design work needed for the permit – in practice, that is exactly what an energy report for a renovation is. The current Building Act is available on Finlex.

What does the law really require when an old building is renovated?

In plain language, the Building Act says: when a building is repaired or altered under a permit, its energy efficiency must be improved if this is technically, functionally and economically feasible. The detailed rules are in the Decree of the Ministry of the Environment on improving the energy performance of buildings undergoing renovation or alteration (4/13, amended by Decree 2/17), which is still in force. The decree defines feasibility as follows:

A technically feasible solution does not weaken the building’s properties, such as the moisture performance of the structures, compared with the existing solution.
A functionally feasible solution does not prevent the building from being used for its purpose.
An economically feasible solution is cost-effective. The review period is 30 years for residential buildings and 20 years for other buildings, unless the normal life cycle of the building part or system is shorter.

Most importantly, the requirements apply to the building parts and systems that are repaired, renewed or new. If you replace the windows, the windows must meet the requirements – the walls do not have to be insulated at the same time. If a measure is left undone in whole or in part, this can be compensated by doing other measures better than required. In an extensive renovation, where the costs related to the envelope or technical systems exceed 25 per cent of the value of the building, it must also be shown that the chosen measures are at a cost-optimal level. The value of the plot is not included in the building’s value.

The obligation does not apply to all buildings. The law excludes, among others, buildings under 50 m², holiday homes used for less than four months a year, and buildings used for worship. For a protected building, the requirements do not apply to the extent that they would change its character or appearance in an unacceptable way – protection alone is therefore not a blanket exemption.

Three ways to meet the requirements

The party carrying out the project may choose which of three ways it uses to show the improvement in energy efficiency:

Way	Typical renovation	What is shown
1. By building part	A single renovation, for example replacing the windows or adding insulation to the facade	The renovated parts meet the decree's part-specific requirements¹. No calculation for the whole building is needed.
2. Energy consumption by building type	An extensive renovation in which several parts and systems are renewed	The building's calculated energy consumption with standardised use is below the limit set for the building type².
3. Reducing the E-value	A change of heating method or a renovation programme carried out in stages	The building's E-value falls by the amount the decree requires from its own calculated baseline³.

In ways 2 and 3, a plan is drawn up showing how the combined effect of the repairs improves energy efficiency, and it is submitted to building control with the permit application. The measures in the plan can be carried out in stages as several separate projects, which fits well with a housing company’s long-term maintenance plan. Earlier repairs that improved energy efficiency without a permit can also be credited in a later permit application, when reports on them are submitted.

Technical systems also have their own requirements, which apply whichever way is chosen: when ventilation or heating is renewed, the new system must meet minimum levels for, for example, heat recovery, the electricity use of the ventilation and the efficiency of the heating system.

The decree’s numerical values:

External wall: original U-value × 0.5, however at most 0.17 W/(m²K). Roof structure: original U-value × 0.5, however at most 0.09 W/(m²K). Base floor: energy efficiency is improved where possible. New windows and external doors: U-value 1.0 W/(m²K) or better; when old ones are repaired, their thermal insulation is improved where possible. The U-value tells you how much heat escapes through the structure – lower is better.
For example, small, terraced and linked houses at most 180 kWh/m² and blocks of flats at most 130 kWh/m² per year. The limit is calculated with the decree’s own calculation rules, so it cannot be compared directly with the E-value of an energy certificate.
Small, terraced and linked houses: E-required ≤ 0.8 × E-calculated, i.e. the E-value after the renovation is at most 80 per cent of the calculated baseline. Blocks of flats: E-required ≤ 0.85 × E-calculated (85 per cent).

Examples by renovation

Windows. The U-value of new windows and external doors must be 1.0 or better – check the value in the window supplier’s quote. Remember the ventilation: when the envelope is made more airtight, the supply of replacement air and the functioning of the ventilation must be ensured. After replacing windows or adding insulation to the envelope, the functioning of the heating and ventilation systems must be verified and the systems balanced and adjusted where necessary, and the verification is presented to building control at the final inspection.

Facade. In additional insulation, the most important thing is the moisture performance of the structure: the decree requires that the thermal, acoustic and moisture performance and the fire safety of the structures are ensured, and that the insulation layers are protected from air flows. If the facade is protected, the requirements do not apply to it to the extent that they would change the facade in an unacceptable way. Any remaining shortfall can be compensated with other measures.

Roof structure. In a roof renovation, adding insulation to the roof structure is a natural step, because the structure is open anyway.

Heating method. When the heating system is renewed, the decree sets efficiency requirements for the new system, and a heat pump has its own minimum level based on its seasonal performance factor (SPF). A change of heating method is also a typical project in which way 3, reducing the E-value, is a natural choice, because the change shows directly in the E-value. An energy well always requires a building permit. We explain how a change of heating method affects the energy class in the article how a house’s energy class is calculated.

What does the report include and what does it cost?

An energy report for a renovation is built around the project. It typically includes:

the starting point: the current data of the structures and systems being renovated, such as the original U-values
the chosen way of meeting the requirements and the reasons for it
calculations: U-value calculations by building part, or an E-value calculation for the whole building before and after the renovation
in ways 2 and 3, the plan for the combined effect
how the requirements for technical systems are met
where necessary, the justification if a measure is not technically, functionally or economically feasible.

The price depends on the scope: a review of one building part is lighter than an E-value calculation for the whole building and a plan for the combined effect. That is why there is no fixed price for renovation reports; we give the price in our quote.

Note that a renovation project does not in itself oblige you to have a new energy certificate drawn up. A new certificate is still often worthwhile so that the improved class shows in sales and rentals – and in a project receiving a Varke grant it is a condition of payment. If you want to plan the whole house’s energy solutions at once, see energy design; broader background on the content of the report is in the article energy report.

Can you get a grant for the renovation?

A housing company can get an energy grant from Varke (the Housing Construction Centre of the Finnish State) for an energy renovation in 2026–2027. The grant conditions are separate from the building control requirements: to qualify for the grant, the E-value must improve by at least 23 per cent in a block of flats and by at least 28 per cent in a small or terraced house, compared with the level at the time the building was built. The application requires, among other things, calculations of the E-value at the time of construction and after the repairs, and a cost estimate itemised by measure. The same starting data serves both the permit and the grant, so it pays to have the calculations done at the same time. We have collected the conditions and stages in the article Varke’s energy grant and the course of the project in the article housing company energy renovation. You can ask us directly for the E-value calculations for the grant application and payment with a request for a quote.

There is no state energy grant for a detached house owner, but the household expenses credit (kotitalousvähennys) can be claimed for the labour share of the renovation – see energy renovation and energy saving.

The requirements for renovation are also changing: a decree to replace Decree 4/13 is being prepared because of the EU Energy Performance of Buildings Directive. New requirements apply only once they have entered into force, and at the time of writing the rules described in this article apply. More about the directive in the article Energy Performance of Buildings Directive EPBD.

Check the starting point

A good starting point is the building’s current energy certificate. Check with our energy certificate check tool whether the building has a valid certificate in the register. For data protection reasons, certificates of detached houses do not appear in the public search, so choose “Add your own energy certificate” in the tool and enter the key data of your certificate. How to read an old certificate is explained in the article is an old energy certificate still valid.

How to proceed

Find out whether a permit is needed from the municipal building control authority already at the project planning stage.
Gather the starting data: the original drawings and structural data, the current energy certificate and, in a housing company, the condition assessment or condition surveys.
Choose the way to meet the requirements together with the designer and the author of the energy report – for a small renovation, a review by building part is often enough.
Attach the report to the permit application if building control asks for it. If the housing company is applying for a grant, check Varke’s guidance for the stage at which the application must be submitted.
At the final inspection, after improvements to the envelope or windows, the verification of the heating and ventilation system adjustments is presented. Order a new energy certificate at the same time, so that the improved class shows.

We prepare energy reports for renovation projects for housing companies and detached houses. Request a quote: housing company renovation project or detached house renovation. If you first want to find out which measures pay off, ask about an energy efficiency improvement study.

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