They told him his villa did not qualify for the tax deduction. The building logbook proved otherwise
A while ago the owner of a detached house got in touch with me to ask for something I am being asked for more and more often: a second opinion.
He wanted to replace the windows in his home and install a pellet stove, and his plan was to take advantage of the Spanish income tax (IRPF) deduction for energy efficiency works. But another assessor had already run the numbers, and the verdict was a bucket of cold water: with those works, his house would not reach the minimum 30 % improvement the deduction requires.
He had all but given up. He called me "just in case".
The requirement: 30 % less non-renewable primary energy
For a single-family house, the relevant deduction requires the works to cut non-renewable primary energy consumption by at least 30 %, or to bring the home up to an energy rating of A or B.
This is proven with two energy performance certificates: one before the works and one after. Comparing the two decides whether you get the deduction or not.
That is why a mistake in the starting certificate is not a technical detail: it can cost the owner thousands of euros.
Where the problem was
I reviewed the other assessor's calculation and quickly spotted something odd in the building envelope: the façade and the roof had been entered as if they had hardly any insulation.
It is an understandable mistake. You cannot see what is inside a wall from the outside, and when there is no information the tendency is to use default values or assume the worst. The problem is that those values completely change the model of the house.
In a villa in our area with little insulation, the software sends the summer cooling demand through the roof. And that part of the consumption is not improved by a pellet stove (which only provides heat), and only partly by new windows. Result: the calculated improvement fell short.
But the house was built in the early 2000s, so I asked him the key question: do you have the Libro del Edificio? That is the building logbook every new building in Spain has had to come with since the year 2000.
The building logbook had the answer
He had it tucked away in a drawer, unopened since he bought the house.
Everything was there: the construction report, the make-up of the walls and roof, the type and thickness of the insulation in the façade and the roof… The insulation was considerably better than had been assumed.
With that data I redid the starting certificate and the simulation of the improvements. The approximate figures were these:
| | Previous calculation | Calculation using the building logbook | |---|---|---| | Non-renewable primary energy before the works | ~196 kWh/m²·year | ~142 kWh/m²·year | | Expected consumption after the works | ~149 kWh/m²·year | ~92 kWh/m²·year | | Reduction | ~24 % | ~35 % |
With the envelope properly defined, heating made up a much larger share of total consumption. And that is where the pellet stove, which runs on biomass (a renewable energy source), makes the difference. Together with the new windows, the improvement comfortably exceeded 30 %.
The house had always met the requirement. It was the calculation that did not.
What I enjoyed most was the client's reaction. He was amazed to see that the logbook he had never opened answered every question about how his house was built: materials, insulation, installations… He told me he had no idea he owned "the instruction manual" for his home.
How much you can save: 40 % or 60 % off your income tax
He is now going ahead with the works and, with the certificate issued afterwards, he will claim the deduction. There are two possible deductions, and you cannot apply both to the same works:
- 40 % deduction: works that cut non-renewable primary energy consumption by at least 30 % (or reach A or B) in your main home or a rented home (or one about to be let). Maximum base of €7,500 a year. Extended for works carried out until 31 December 2026.
- 60 % deduction: energy refurbishment works in predominantly residential buildings, which include single-family houses, with the same 30 % requirement (or A or B). Maximum base of €5,000 a year and €15,000 in total, with any excess carried forward to the following years. Extended until 31 December 2027.
For a villa like this one, the 60 % deduction is usually the most attractive option. With an investment of around €14,000 for the windows and the stove, the deduction can come to around €8,400, spread over several tax returns. With the previous calculation, that money would have been lost.
Important: these are deductions in Spanish income tax (IRPF), so they are only available to Spanish tax residents. If you own a home in Spain but are not tax resident here, you pay non-resident income tax (IRNR) and cannot claim them. The deduction is applied in the tax year in which the post-works certificate is issued, and the starting certificate must be issued before the works begin. Always check with your tax adviser which deduction applies to you.
What I learnt from this case
1. Ask for a second opinion if you fall just short of the threshold. A 24 % result for works like these did not add up. When the result does not match the works, it is worth reviewing the calculation.
2. Look for the building logbook. If your home was built after 2000, it should have one. It is the best source for the real insulation, materials and installations, and it saves working from assumptions.
3. Default values penalise you. A certificate based on estimated data almost always comes out worse than reality. The more real documentation you provide (building logbook, technical data sheets, invoices), the more reliable the result.
Have you been told your renovation does not qualify for the deduction or for a grant? Get a price for your certificate and write to me: I will review your case and tell you whether the numbers have room to move.