Energy performance certificate

What the letter class measures

An assessor models the dwelling: the walls, the roof, the glazing, the orientation, the airtightness, the heating and cooling equipment, the hot water system, the ventilation and any generation on site. From that model comes the energy the dwelling is calculated to need over a year for each square metre of floor area. The figure is then placed on a lettered scale, best class at the top, worst at the bottom.

Because the calculation uses a standard pattern of occupation, the class describes the building rather than the people in it. The same flat keeps its letter whether the owner spends the winter there or leaves it empty. The scale is also relative to a national reference and to a climate zone, so a flat on the Costa Blanca and a flat in Vilnius carrying the same letter are not insulated to the same standard; each was measured against its own benchmark.

Spanish certificates usually show two scales, one for primary non-renewable energy and one for carbon emissions, and a dwelling can sit a class apart on each. When a letter is quoted to you in an advertisement, ask which of the two it refers to.

Why it is required to sell or let

The requirement comes from the European directive on the energy performance of buildings and is written into national law in every member state, Spain and Lithuania included. A valid certificate has to exist before a dwelling is advertised for sale or for letting, the class has to appear in the advertisement, and the document itself is handed to the buyer or the tenant and referred to in the deed or the lease.

Only an assessor with the qualification set by national rules may issue one, and the certificate is lodged in a public register held by the region or the state. Each certificate has a maximum period of validity after which it has to be renewed; the period is set nationally, so check the expiry printed on the document itself rather than assuming. Marketing a property without a valid certificate is a breach that carries a fine.

Two practical consequences for a buyer. A certificate that expires before you complete is of no use at the deed, and an existing dwelling that has been refurbished may carry a certificate describing the building as it was. Ask when the assessment was made and what was changed afterwards.

What it says about running costs

The letter compares dwellings. It does not predict an invoice, because the invoice depends on tariffs, on the weather and on how the occupant lives. What makes the certificate worth reading is the detail behind the letter: the demand for heating and the demand for cooling given separately, the equipment the model assumed, and the list of improvements the assessor recommends with their expected effect.

Climate decides which of those numbers to look at first. On the Mediterranean coast the cooling demand, the shading of the south and west glazing and the way the building sheds summer heat govern the bills. In the Baltic the heating demand, the insulation thickness and whether the ventilation recovers heat matter more. A good class reached through fabric and heat recovery behaves differently from the same class reached largely through a photovoltaic array on the roof, which produces most when demand is lowest.

The class has begun to carry weight outside the utility bill as well. Lenders in several countries price mortgages partly on it, and rules limiting the letting of the poorest classes are being tightened across the EU. This area is moving quickly, and what applies in Spain is not what applies in Lithuania. A local adviser or your notary can say what is in force where you are buying.

What a new building normally reaches

EU rules require new buildings to be close to zero energy, and national building codes implement that through minimum insulation, airtightness, efficient equipment and a share of renewable generation. A dwelling built to a current code therefore lands in the upper classes. The exact letter depends on the national reference, the climate zone and what is generated on the plot, which is why a specific letter promised before the final assessment is a promise about something not yet measured.

Most of the class is decided on the drawing board: the compactness of the building, where the glazing faces, how it is shaded, where the thermal bridges are. Equipment installed later can compensate only in part. SAVO runs the energy calculation alongside the design of its residential projects, and the certificate issued at completion forms part of the document set handed to the buyer.

If you are buying before completion, ask for the design-stage calculation while the building is going up and for the issued certificate at handover, then read one against the other. Where they differ, ask what changed on site and whether anything was substituted.