1. The three parts of the definition
According to institutional sources an emission-free, or zero-emission, building is defined by three features. The definition is set in the directive.
| Part | Content |
|---|---|
| 1 | very high energy performance, the building requiring zero or a very small amount of energy |
| 2 | generates no on-site carbon emissions from fossil fuels |
| 3 | generates no emissions, or only a very small amount |
The second part is the most concrete and the most binding: on-site combustion of fossil fuels is excluded. In practice this means a fossil-fuel boiler does not belong in a zero-emission building whatever its efficiency.
2. How the limit is tied to the nearly zero-energy building
The relationship is defined as a percentage rather than an absolute value, which links the two levels. The percentage is relative to a reference.
According to professional sources the maximum limit for an emission-free building must be at least 10 per cent lower than the total primary energy use limit set for a nearly zero-energy building. The limit differs between member states.
According to professional sources the annex to the directive sets out, for the first time, numerical limit values for zero-emission buildings which national requirements may not exceed. Estonian requirements therefore cannot be more lenient than the directive's, though they may be stricter, and the specific values must be taken from the Estonian legislation in force, not from the directive or from commentary.
3. What the requirement actually consists of
One sentence resolves most of the confusion, and it concerns the balance. The requirement is balance-based.
According to professional sources, in a zero-emission building the delivered energy must be offset by renewable energy: the building consumes energy, but that energy is covered from renewable sources. According to professional sources, appliances and, in residential buildings, lighting are not counted within delivered energy.
The requirement is therefore balance-based rather than a zeroing of consumption, from which it follows that the share of renewable energy becomes even more decisive than for a nearly zero-energy building. A building may consume where the balance is covered.
4. What distinguishes it from the current level
Three differences, and the third is technically the most important. They separate zero-emission from nearly zero-energy.
| Difference | Content |
|---|---|
| Stricter limit | at least 10 % lower |
| Exclusion of on-site fossil fuel emissions | a new condition, not open to compensation |
| Basis of calculation | the draft uses total primary energy, whereas the ETA rests on non-renewable primary energy |
The third is also the most contested, as covered by the article on what remains unsettled. A change of calculation basis means results are not directly comparable with the current energy performance value.
5. What it means for choosing solutions
Three consequences are already visible today, before the requirement enters into force. They concern design and investment.
Solutions based on fossil fuels become risky in terms of future-proofing, and the volume of on-site renewable generation becomes more decisive. Efficient district heating may take on a larger role, because it is not on-site combustion of fossil fuels, though this depends on the composition of the district heating network, whose conditions are defined in the regulation in force.
Summary and four practical rules
A zero-emission building is a building of very high energy performance that generates no on-site carbon emissions from fossil fuels and whose emissions are absent or very small. The limit is defined as a relationship: at least ten per cent below the total primary energy limit for a nearly zero-energy building. The requirement is balance-based, since delivered energy is offset by renewable energy, and the basis of calculation differs from the current energy performance value, so results are not directly comparable.
Four rules: do not read the name literally, zero emissions does not mean zero consumption. Avoid an on-site fossil-fuel solution in a long-lived project. Follow the change in the basis of calculation, since it affects every result. Take the values from Estonian legislation in force, not from the directive.
This article offers professional orientation as at the date of verification. It replaces neither the regulations in force nor the assessment of a competent specialist.