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Energy retrofit design
I design energy retrofits for existing houses in Abruzzo: what to insulate, what to replace and in what order, decided on the building in front of us and on the bills it actually produces.
What an energy retrofit design covers
An energy retrofit design sets out which measures to carry out on an existing building, in what order and to what performance: wall insulation inside or out — in Italy an external system is called a cappotto — replacement windows, insulation of the roof and of the floors over unheated space, heat generation and distribution, ventilation, and the treatment of thermal bridges. Ivan Nozzi is an Ingegnere, an engineer registered in Italy with the Ordine degli Ingegneri della Provincia di Chieti under no. 2489, Sezione A, civil and environmental sector, practising from Torrevecchia Teatina (CH) in Abruzzo.
The APE, Italy's energy performance certificate, is not issued by me. It is signed by a certifier accredited on the regional register, who is a different person from the designer of the works. I produce the calculations, the drawings and the technical documentation, and I coordinate with that certifier. Saying so at the outset avoids the most common confusion in this market, where an APE is sometimes sold as though it were a retrofit plan. It is not: it is a rating of the building.
Sequence matters more than product choice. On an existing house you first reduce demand — roof, walls, windows, air-tightness — and only then size the heat generator against that reduced demand. Doing it the other way round produces an oversized system that spends the next twenty years heating the losses you never fixed.
Not every measure repays on every building. A stone farmhouse with thick walls, a 1970s villetta and a flat in a condominio lose heat in different places, and the same money spent in different places buys very different results. So the design compares alternative packages of works against estimated cost, expected saving and payback, and states the assumptions the comparison rests on rather than hiding them.
Method
What the design work actually involves
Retrofit design starts with a survey of the building as it stands and ends with the documents a contractor builds from and prices against. These are the steps.
- Survey of the existing envelope: geometry, wall build-ups, roof, floors over cellars and unheated lofts, the type and condition of every window and external door.
- Survey of the systems: heat generator, emitters, distribution, domestic hot water, any cooling, controls and metering.
- Reading the last few years of energy bills, so measured consumption can be set against calculated demand and the gaps between the model and the house become visible.
- Comparison of alternative packages of works: estimated cost, expected saving and payback for each, with the assumptions written down.
- Thermal calculations and the Legge 10 technical report where the type of intervention requires it, prepared on the statutory forms and filed with the building application.
- Thermal bridge and interstitial condensation checks at the details that decide the outcome: window reveals and sills, ground junctions, eaves, balconies and terraces.
- Coordination with structural works where the retrofit touches floors, roofs or loadbearing masonry, so the two sets of works do not obstruct one another.
- Drawings, a window schedule, a performance specification and a priced bill of quantities, so the tenders you receive from contractors can genuinely be compared.
- The technical documentation required by the building application and by the tax relief formalities, produced alongside the design rather than assembled afterwards.
Comparison
Which measures pay, and when they do not
Each measure has a field of application and a set of interferences with the rest of the job. This table also says when a measure, taken on its own, does not repay.
| Measure | What it does | When it makes sense | What it interacts with |
|---|---|---|---|
| External wall insulation (cappotto) | Cuts heat loss through the walls and, where the junction details are resolved in the design, softens the thermal bridges. | On uninsulated walls, where the facade is not subject to a heritage constraint and has not just been rendered. | Windows and frames, sills, gutters and downpipes, balconies, boundary distances and the facade line. |
| Roof and loft insulation | Removes the loss upwards, usually the largest single one, and cuts summer overheating in the rooms below the tiles. | Almost always first, and unarguably first if the covering has to be relaid anyway: euro for euro it generally returns more than the walls. | Re-roofing, flashings and gutters, any strengthening of the roof timbers. |
| Replacement windows | Improves the glazing and, more decisively, the air-tightness of the openings and the comfort of sitting near them. | Where the glass is single or the frames no longer close. On a house that is otherwise uninsulated, new windows alone change little. | Wall insulation at reveals and lintels, and ventilation: a sealed window can move condensation onto the walls. |
| Heat pump | Replaces the boiler and makes heat from electricity, efficiently only at low flow temperatures. | After the fabric is insulated and with emitters that work at low temperature. Fitted to an uninsulated house with small radiators, running costs can rise rather than fall. | Contracted electrical power and the consumer unit, emitters, outdoor unit position and noise, photovoltaic. |
| Solar thermal and photovoltaic | Produce domestic hot water and on-site electricity respectively. | Where a roof pitch has the exposure and some consumption falls within the hours of production; photovoltaic pairs naturally with a heat pump. | Roof structure and covering, electrical panel and meter, battery storage if any. |
| Mechanical ventilation with heat recovery | Provides controlled air change with heat recovery once the building has been made airtight. | On deep retrofits. On a partial renovation that leaves old windows elsewhere in the house, it does not repay. | Ceiling voids and duct routes, available depth, periodic filter maintenance. |
No row in this table is a recommendation. The answer depends on the building, its exposure, how you use it and the budget, and the comparison has to be redone on the numbers of the specific case.
Tax relief
Tax relief, and how it is handled in the design
Renovation and energy efficiency works in Italy attract deductions against income tax. The rates, the spending ceilings, the eligible properties and the technical requirements are set by the annual Legge di Bilancio and change from one year to the next, which is why you will find no percentage anywhere on this site. Treat any figure quoted to you before the works calendar is known as decoration.
The regime that applies is the one in force when the works begin and the costs are incurred. It has to be checked at that moment, against the technical requirements in force then, because a scheme designed to rules that have since changed loses the relief even when the building work is faultless.
The technical half is mine. Performance thresholds to be met, calculations, product data sheets, the sworn technical statements the rules require, and a documented trail from what was designed to what was built: all of it belongs to the design rather than to a scramble at the end. The fiscal half — your tax capacity, payment methods, how the deduction is spread, any alternative to claiming it directly — belongs with your Italian accountant. I do not give tax advice.
Questions
Common questions about retrofitting a house in Italy
Who issues the APE energy certificate in Italy?
The APE is issued by a certifier accredited on the regional register, who must be a different professional from the designer of the works. I design the retrofit, produce the calculations and the technical documentation and coordinate with the certifier, but the certificate does not carry my signature. If you do not already have a certifier, I will explain how to find one who is properly registered.
Should I insulate first, or replace the heating first?
On almost every existing house, insulate first. Insulating the roof and the walls lowers demand, and the heat generator is then sized against that lower demand, so it is smaller and works in better conditions. The reverse order leaves you with an oversized system heating the losses. The exception is a boiler that has already failed: replace it now, choosing something compatible with the insulation planned later.
Will a heat pump work in an old stone house in Abruzzo?
It will run, but running costs can exceed those of the boiler it replaced. A heat pump is efficient at low flow temperatures, and an uninsulated house with radiators sized for very hot water keeps it in unfavourable conditions for most of the season. Reduce demand and check the emitters first; then the change of generator becomes a good decision rather than an expensive one.
Do I need permission to add external wall insulation in Italy?
In almost every case, yes. External insulation changes the thickness and the appearance of the facade and, depending on the comune and the works, needs a CILA or a SCIA, together with checks on boundary distances, projections over public land and, in a condominio, the building regulations. The application is filed before work starts and I prepare it alongside the design.
Can this be organised while I am abroad?
Yes. The survey happens on site, the planning history is obtained from the comune, and the drawings, the comparison of options and the written report reach you by email. You are welcome to write in English or German: enquiries in those languages are read and answered. The report itself is drawn up in Italian, the language that carries legal effect in Italy, and meetings and calls are held in Italian, so where a live conversation with the comune or the contractor is needed, plan for someone to interpret — or I can suggest someone locally.
Start with the building
Send me the address, photographs of the outside and of the plant, and the last two years of energy bills. I will tell you what is worth checking first and how I would set the design up.