Il rapporto di controllo di efficienza energetica riguarda l'impianto termico.

This is very common in formal Italian. Di often links nouns together, a bit like of in English.

Here:

• rapporto = report
• di controllo = of inspection / for checking
• di efficienza energetica = of energy efficiency

So the whole noun phrase is built step by step:

• rapporto
• rapporto di controllo
• rapporto di controllo di efficienza energetica

In more natural English, you would usually restructure it rather than translate each di literally.

Yes, rapporto can mean relationship in some contexts, but not here.

In this sentence, rapporto means report, especially a formal or technical report. Italian often uses one word in several meanings, so context matters.

Examples:

• un rapporto tra due persone = a relationship between two people
• un rapporto tecnico = a technical report

Here, because of words like controllo and efficienza energetica, it clearly means a formal document.

Because impianto begins with a vowel, il becomes l' before it.

So:

• il libro
• il controllo
• l'impianto

This shortening is called elision. It is very common in Italian with singular articles before vowels.

Impianto termico is a technical expression. It usually refers to a heating system or thermal system in a building.

• impianto = system, installation, plant
• termico = thermal, related to heat

In everyday practical use, it often means the system used for heating, and sometimes hot water, depending on the context.

Because the subject of the sentence is singular: Il rapporto.

The verb must agree with the subject:

• Il rapporto riguarda... = The report concerns...
• I rapporti riguardano... = The reports concern...

Even though the subject is a long noun phrase, the main noun is still rapporto, which is singular.

Riguardare means to concern, to refer to, or to be about, depending on context.

In this sentence, riguarda means something like:

• concerns
• relates to
• is about

So Il rapporto ... riguarda l'impianto termico means that the report is about or concerns the heating system.

Because energetica agrees with efficienza, which is feminine singular.

• efficienza = feminine singular
• adjective must match it
• so: energetica

Compare:

• efficienza energetica = energy efficiency
• consumo energetico = energy consumption

Here, energetica describes efficienza, not controllo or rapporto.

Italian often omits the article in noun chains like this, especially in formal or technical language.

So:

• controllo di efficienza energetica = energy-efficiency inspection/check

If you added an article, the meaning or tone could change slightly, and it would sound less like a fixed technical label.

This article omission is common in set phrases:

• certificato di nascita
• permesso di soggiorno
• rapporto di prova

It is grammatical and natural, but it sounds formal, technical, and bureaucratic.

A native speaker would expect this kind of sentence in:

• official documents
• maintenance reports
• regulations
• technical paperwork

In casual speech, someone might simplify it a lot.

Yes, but this order is the most standard for formal written Italian.

For example, you could say:

• L'impianto termico è oggetto del rapporto di controllo di efficienza energetica.

But that sounds even more formal.

The original sentence is straightforward because:

• first comes the document: Il rapporto...
• then the verb: riguarda
• then what it concerns: l'impianto termico

That is a very normal structure in Italian.

A common mistake would be to translate each word too literally and end up with something awkward like:

The report of control of energetic efficiency concerns the thermal system.

That sounds unnatural in English. The learner should understand the Italian structure, but not copy it directly into English.

A more natural English version would usually be something like:

• The energy efficiency inspection report concerns the heating system.
• The report on the energy efficiency check refers to the heating system.

So one important lesson here is: Italian noun phrases often use repeated di, while English usually compresses or reshapes them.

Yes, it works like a technical set phrase. In contexts involving boilers, heating systems, and building maintenance, controllo di efficienza energetica is a standard expression for an energy-efficiency check or inspection.

That is why the whole sentence feels specialized. A learner should probably treat:

• rapporto di controllo di efficienza energetica and
• impianto termico

as chunks, not just as separate words.