1. What the KEK rests on
The basis is measured rather than calculated, though that does not make it a sum of bills. Measured data depend on the occupants.
An energy certificate for an existing building is prepared on the basis of actual energy consumption data, and it is called weighted specific energy use. Weighting means that different energy carriers are counted with different factors, because their primary energy content differs.
The result is therefore measured consumption converted into a comparable indicator. Two buildings consuming the same number of kilowatt-hours from different energy carriers do not receive the same figure.
2. What the certificate contains
Under the regulation in force the certificate for an existing building consists of several parts, and one of them is underused. The parts are listed in the regulation.
| Part | Intended for |
|---|---|
| The certificate's summary information | general |
| The part to be displayed in a visible place for visitors | the visitor |
| The list of energy saving measures | the owner and the buyer |
| The input data needed for the calculation | the specialist |
The third part is the most useful from the client's point of view and the least used: it says what could be improved. Where a certificate is commissioned for a building, the list of saving measures is worth reading, not merely the class.
3. Why ten years is logical
The validity is five times longer than that of the calculated certificate, and the reason is substantive. Measured data change more slowly.
Actual consumption changes slowly where a building is not reconstructed, so a measured result retains its meaning for years. The calculated certificate, by contrast, describes a designed situation that loses meaning as soon as actual data exist.
Where a building is substantially reconstructed, a new calculated certificate is prepared and the cycle starts again: calculation, two years, then measurement. The old certificate then loses its meaning.
4. What it tells a buyer
Three things the calculated certificate does not say, and one advantage that is rarely used. They concern actual use.
| What the KEK says | Why it matters |
|---|---|
| How much is actually consumed in the building | not how much should be |
| Whether use matches the designed purpose | a divergence is a signal |
| Which improvement measures have already been identified | through the list of saving measures |
The register is public, which means a buyer can see these data before making an offer. This is one of the few places where an Estonian public register gives the buyer a substantive advantage, and it is rarely used.
5. What the KEK does not tell
Two limits are worth knowing, because ignoring them leads to the wrong comparison. They concern where the data come from.
The certificate does not say how efficiently the building was built: a very efficient building may house a large family that consumes a great deal. Nor does it say what the occupants' effect is, since consumption depends on behaviour and not on the building alone.
Comparing the KEK classes of two buildings therefore compares use, not construction alone. Understanding that limit matters as much as reading the certificate, and it is why both certificates are consulted when planning a reconstruction.
Summary and four practical rules
The certificate for an existing building rests on actual consumption data weighted by energy carrier and is valid for ten years, because actual consumption changes slowly. It consists of four parts, of which the list of energy saving measures is the most useful to the client and the least read. The KEK does not say how efficiently a building was built, since consumption also depends on the occupants, so comparing the classes of two buildings compares use rather than construction alone.
Four rules: use the KEK to describe an existing building, not to assess a future one. Read the list of saving measures, the certificate's most practical part. Explain to the client that the class also reflects use. Check the register before a purchase, since the data are public and free.
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.