Basic and detailed assessment under BRL 9500

A basic assessment is the assessment an EP advisor carries out when the detailed data about the building is missing. A detailed assessment is the assessment when that data is available. Both follow the assessment protocol in ISSO publication 82.1 (the ISSO assessment protocol), which the assessment guideline BRL 9500-W from InstallQ (the Dutch certification body) refers to.

The difference lies in what is measured, who may do it, and how much data is entered. Which assessment you need depends mainly on the building and the situation. You find the rules for that on the page about dwellings or non-residential buildings. The energy label itself is calculated with software certified under NTA 8800. See also the RVO page about EP-Online .

What is a basic assessment?

The basic assessment is the light version. The advisor only records what can be seen visually, or what can be found out in a simple way. Think of the orientation of the home, the number of rooms and the type of heating.

Many details are then missing. For those details, the software uses a fixed value. The guideline calls this ‘unknown’. The advisor chooses that option when he cannot see or trace a characteristic. The software then calculates with a standard value.

What is a detailed assessment?

The detailed assessment is the heavy version. The advisor collects more data on constructions, glazing, installations and thermal bridges. He enters that data and does the calculations himself. With detailed drawings and installation schemes, he can record many of those values instead of estimating them.

The authorisation is also different. A basic assessment may be carried out by an EP-W/B advisor. A detailed assessment may only be carried out by an EP-W/D advisor. An EP-W/D advisor automatically meets the requirements for a basic assessment.

The difference at a glance

Item	Basic assessment	Detailed assessment
When	When detailed input data is missing	When detailed data is available
Who may do it	EP-W/B or EP-W/D advisor	EP-W/D advisor only
Data	What is visually visible or easy to find out	More data, plus own calculations
Unknown values	The ‘unknown’ option may be used, with a standard value	Fewer estimates, because more data is entered
Time and cost	Shorter and usually cheaper	Longer and usually more expensive

The guideline does not mention prices. The difference in time follows from the amount of data you need to collect. Ask for the type of assessment in every quote, so you compare like with like. You can read more about prices on the costs and timeline page.

When must you do a detailed assessment?

In some situations, a detailed assessment is mandatory. The guideline names these cases, among others:

A calculation to show that a new dwelling meets the legal requirements.
Replacement after demolition, where only the foundation and floor remain and the outer shell is new.
A full renovation of a dwelling for which new insulation or renewable energy requirements apply after 1 January 2021.
A new dwelling with a handover date after 1 January 2021.
An application for an energy performance allowance, or proof that an improvement meets a BENG requirement (nearly zero-energy building requirement).
A dwelling that was previously registered with a detailed assessment.

At handover, a detailed assessment is always mandatory, even if the assessment takes place later. For existing dwellings, the advisor may choose a basic assessment if a detailed assessment is not mandatory. If none of these situations applies, the client makes the choice.

An example: the same dwelling, two situations

Take a fictional terraced house from 1975 that owner Marit Dekker wants to sell. When an existing dwelling is sold, it must have an energy label. Advisor Thijs Koster (EP-W/B) visits. The meter cupboard is visible, and so is the roof insulation. He has no papers for the type of glazing or the cavity wall insulation. He does a basic assessment and uses the ‘unknown’ option for those two unknown values.

Now suppose Marit demolishes the house and builds a new one, handed over in 2027. A detailed assessment is then required, because the handover date is after 1 January 2021. An EP-W/D advisor carries it out. He measures the constructions on site and enters the actual values. The label result is then more precise, but the assessment takes more time.

An EP advisor who registers a detailed assessment as a basic assessment receives a deviation. The guideline gives this as an example of incorrect registration. If an advisor receives a critical deviation caused by such an error in two consecutive years, InstallQ may withdraw his competence. See internal and external inspections.

What does it mean for accuracy?

With a basic assessment, the software uses standard values for everything that is unknown. That is not wrong, but it is an estimate. With a detailed assessment, there are fewer estimates, because the advisor has entered more data.

That is why the energy label can differ depending on the type of assessment. A dwelling assessed first with a basic assessment and later with a detailed assessment can receive a different label. That does not mean either one is ‘wrong’. It does mean the detailed assessment is the sharper measurement.

Frequently asked questions

May I carry out a basic assessment on a dwelling that was previously registered with a detailed assessment?

No, not if the dwelling was previously registered with a detailed assessment. The guideline makes this a requirement in that situation. Ask your advisor which type of assessment the earlier registration used.

Who decides whether I need a basic or detailed assessment?

That depends first on the situation. If the dwelling falls into a category where a detailed assessment is mandatory, that choice has already been made. In all other cases, the client chooses. The advisor can help you, but cannot make the choice for you.

Is a basic assessment always cheaper?

Usually, because the advisor collects and enters less data. But a cheap basic assessment is not always the best choice. If you want to improve the energy performance of the dwelling later, a detailed assessment can give you more guidance. Ask for both prices and compare what you get for them.