Energy-efficient house building – requirements and solutions 2026

An energy-efficient house is built from four parts: a well-insulated, airtight envelope; ventilation with heat recovery; heat-pump heating; and, increasingly, your own solar power. By regulation, new houses in Finland are already close to zero-energy buildings, and the great majority are completed in energy class B. Class A is within reach when all four areas are done better than the baseline.

What does the law require in 2026?

The Building Act 751/2023 (rakentamislaki) came into force at the start of 2025, but the energy-efficiency figures still come from the 2017 decrees, above all Decree 1010/2017. The key metric is the E-value: the calculated purchased energy weighted by energy-carrier factors. For a small house (50–150 m²) the E-value ceiling is 200 − 0.6 × heated net floor area, and for a 150–600 m² house 116 − 0.04 × net area. Solid log houses get a statutory concession: the limit may be exceeded by 10–20 per cent depending on the building type. For example, a 140 m² log house's limit is about 139 kWhE/(m²·a).

The climate assessment requirement that took effect at the start of 2026 does not apply to detached houses. A house builder therefore still concentrates on the E-value and the quality of the envelope.

The envelope: insulation and airtightness matter most

The U-value references for heated spaces are: external wall 0.17, log wall (structural thickness at least 180 mm) 0.40, roof 0.09, and windows and doors 1.0 W/(m²K). An individual element may be worse than the reference if the heat loss is compensated elsewhere – that is what the compensation calculation is for.

Airtightness matters at least as much. The air-leakage rate q50 may be at most 4.0 m³/(h·m²), but the energy calculation rewards tighter: without a measurement it assumes 2.0, and a better pressure-test result improves the E-value directly. For moisture safety, target q50 ≤ 1.0. Quality log houses have measured as low as 0.3 m³/(h·m²) – careful work at corners and joints shows in the results.

Heating and ventilation deliver the savings

The standard solution is a heat pump – ground source or air-to-water – with water-based underfloor heating; a low flow temperature keeps efficiency high. Ventilation heat recovery must cover at least 55 per cent of the ventilation heating demand, and good equipment reaches about 70 per cent annual efficiency in practice. Choose on SCOP and annual-efficiency figures, not purchase price.

What does a class A house look like?

The E-value weights purchased energy by energy-carrier factors: electricity 1.20, district heating and renewable fuels 0.50. A heat pump lowers it effectively by cutting purchased electricity. The class runs A–G, and most new small houses land in B. Class A requires a good, airtight envelope, efficient heat recovery, heat-pump heating and usually solar power.

The energy performance certificate is drawn up at the permit stage; a new house's certificate costs about €220 and the commissioning-stage update about €80. A holiday home not in year-round use needs no certificate at all – so most cabins fall outside the requirement.

Is solar power worth it in 2026?

Usually yes, if the roof slope faces roughly south and electricity is also used during the day. Turnkey prices in 2026 are typically €7,000–10,000 (5 kWp) and €11,000–15,000 (8 kWp). Yield in southern Finland is 900–1,100 kWh/kWp a year, and the payback period without a battery is typically 6–12 years. Surplus electricity sold to the grid fetches only about 4 cents/kWh while bought electricity costs about 13 cents/kWh – so size the system to your own consumption, not to the roof's maximum. Note that installation work on a new build does not qualify for the household expenses tax credit (kotitalousvähennys); it applies only to work on an existing house.

What changes next?

Implementation of the EU's Energy Performance of Buildings Directive tightens the requirements in stages: the zero-emission building requirement applies to new public buildings from 1 January 2028 and to all new buildings from 1 January 2030. Anyone building in 2026 still works to the current requirements. A house clearly better than the minimum is nonetheless a sensible goal: it holds its value as regulation tightens and trims the heating bill every year.

Checklist for energy-efficient building

• Commission the energy report and E-value calculation at the sketch stage – changes are cheap then.
• Invest first in the roof, windows and airtightness, and only then in extra technology.
• Put the airtightness test into the contract in writing and set a target of q50 ≤ 1.0.
• Choose the heat pump and heat-recovery unit on efficiency figures.
• Work out solar power's profitability with your own consumption profile before ordering.

• The E-value decides the permit: the limit for a 50–150 m² house is 200 − 0.6 × net area; a log house gets a 10–20% concession.
• U-value references: external wall 0.17, log wall ≥ 180 mm 0.40, roof 0.09, windows and doors 1.0 W/(m²K).
• Air-leakage rate q50 at most 4.0 – a good target is under 1.0, and a measured result improves the E-value.
• Heat recovery must cover at least 55% of ventilation heat demand; good units reach about 70%.
• A 5 kWp solar system costs about €7,000–10,000 in 2026, payback typically 6–12 years.
• Most new houses reach class B; class A demands an airtight envelope, a heat pump and usually solar power.