This article is a translation of the original Finnish article: E-luvun laskentaesimerkit
E-value calculation examples
· updated
These E-value (E-luku) calculation examples aim to explain, in simplified form, how a building’s E-value is determined and what is taken into account in the calculation. The energy efficiency class table in turn shows which energy efficiency class a building belongs to on the basis of its E-value. In reality, calculating the E-value is a fairly complex task, which is why energy performance certificate (energiatodistus) assessors generally use simulation and calculation software for it. In our own assignments we use, among others, the EcoMender calculation software.
These calculation examples present the factors that affect how a building’s E-value and energy efficiency class are determined, and which therefore make up one of the main contents of the energy certificate. A good energy class is reached with different E-values in different building types; for example, blocks of flats reach the best energy efficiency class, A, with an E-value of 75 or less. For office buildings the corresponding E-value limit is 80, and for hospitals 150. Further down in the article you will find the E-value calculation examples and the energy class tables.
E-value
Together with the energy efficiency class, the E-value is one of the two most important figures in the energy certificate. It expresses how much energy, weighted by energy carrier factors (energiamuotokertoimet), the building consumes per year per unit of floor area according to the calculation. The unit of the E-value is kWhE/(m² year). In calculating the E-value, the building’s purchased energy consumption is first determined by energy carrier on the basis of the calculation rules; energy carriers include electricity and district heating, for example. Once the building’s energy consumption by energy carrier is known, it is divided by the building’s heated net floor area. Finally, the energy consumption is multiplied by the energy carrier factors. The energy carrier factors for the different energy carriers are:
- electricity 1,2
- district heating 0,5
- district cooling 0,28
- fossil fuels 1
- renewable fuels used in the building 0,5
Small residential buildings (use category 1 a–c)
For small residential buildings, the energy class is determined by the energy efficiency class table below. Small residential buildings include, among others, detached houses, post-war veteran’s houses (rintamamiestalot) and semi-detached houses. The energy efficiency class limits for small residential buildings depend on the floor area of the building; you can read more about this, if needed, in the article E-value calculation examples.
E-value calculation example 1: Office buildings, use category 3
The building is heated with ground source heat, and electricity is the only energy carrier used. According to the E-value calculation rules, the electricity consumption of a 2000 m² commercial office building is 140 000 kWh/year. The energy carrier factor for electricity is 1,2, so the E-value is calculated as: (140 000 x 1,2) / 2000 = 84 kWhE/(m2 year).
According to the energy class table for office premises, an E-value of 84 falls into energy efficiency class B:
Office buildings (use category 3)
- Office building
- Health centre
| Energy efficiency class | E-value (kWhE/m²·year) |
|---|---|
| A | E-value ≤ 80 |
| B | 81 ≤ E-value ≤ 120 |
| C | 121 ≤ E-value ≤ 170 |
| D | 171 ≤ E-value ≤ 200 |
| E | 201 ≤ E-value ≤ 240 |
| F | 241 ≤ E-value ≤ 300 |
| G | 301 ≤ E-value |
E-value calculation example 2: Small residential buildings, use category 1 a–c.
According to the calculation, a 100 m² detached house consumes 7000 kWh of electricity and 8000 kWh of district heating a year. The E-value is calculated as (7000 x 1,2 + 8000 x 0,5) / 100 = 124 kWhE/(m² year).
The energy efficiency class limits for small residential buildings depend on the building’s floor area. A 100 m2 detached house is in energy efficiency class B when its E-value is over 90 but no more than 155. (110 – 0,2 x 100 = 90 and 215 – 0,6 x 100 = 155.) An E-value of 124 therefore puts it in energy class B.
Small residential buildings (use category 1 a–c)
- Single-dwelling house
- Two-dwelling house
- Building forming part of a linked house (ketjutalo) and other detached small house
50 m² ≤ Anetto ≤ 150 m², where Anetto is the building’s heated net floor area
| Energy efficiency class | E-value (kWhE/m²·year) |
|---|---|
| A | E-value ≤ 110 – 0,2 × Anetto |
| B | 110 – 0,2 × Anetto < E-value ≤ 215 – 0,6 × Anetto |
| C | 215 – 0,6 × Anetto < E-value ≤ 252 – 0,6 × Anetto |
| D | 252 – 0,6 × Anetto < E-value ≤ 332 – 0,6 × Anetto |
| E | 332 – 0,6 × Anetto < E-value ≤ 462 – 0,6 × Anetto |
| F | 462 – 0,6 × Anetto < E-value ≤ 532 – 0,6 × Anetto |
| G | 532 – 0,6 × Anetto < E-value |
E-value calculation example 3: Blocks of flats, use category 2
A block of flats heated with district heating, with the flats cooled in summer by district cooling. For a 1000 m² block of flats, the energy calculation gives district heating consumption of 45 000 kWh/yr, electricity consumption of 44 000 kWh/yr and district cooling consumption of 5000 kWh/yr. The E-value is calculated as: (45 000 x 0,5 + 44 000 x 1,2 + 5000 x 0,28) / 1000 = 76,7, which rounds to an E-value of 77.
With an E-value of 77, the block of flats is in energy efficiency class B:
Blocks of flats (use category 2)
- Block of flats with residential floors on at least three storeys
| Energy efficiency class | E-value (kWhE/m²·year) |
|---|---|
| A | E-value ≤ 75 |
| B | 76 ≤ E-value ≤ 100 |
| C | 101 ≤ E-value ≤ 130 |
| D | 131 ≤ E-value ≤ 160 |
| E | 161 ≤ E-value ≤ 190 |
| F | 191 ≤ E-value ≤ 240 |
| G | 241 ≤ E-value |
Energy certificate
The energy certificate is a document that shows, among other things, the building’s energy efficiency class, its E-value and the input values used to calculate it. Information used in calculating the E-value and recorded in the energy certificate includes:
- U-values of the walls, base floor and roof (the U-value describes thermal transmittance)
- Efficiency of heat recovery in the ventilation system (how efficiently the ventilation system transfers heat from the exhaust air to the supply air)
- q50 air leakage rate (how airtight the structures are), etc.
Energy efficiency class table
The energy class table, or energy efficiency class table, is different for different building types. The table sets out the limits for each energy class, which determine which energy efficiency class a building belongs to. The energy efficiency classes run from A to G, where A is the most energy-efficient and G the least energy-efficient rating. Building types are divided into 10 categories:
- Small residential buildings (use category 1 a–c)
- Terraced houses and two-storey blocks of flats (use category 1d)
- Blocks of flats (use category 2)
- Office buildings (use category 3)
- Commercial buildings (use category 4)
- Accommodation buildings (use category 5)
- Educational buildings and day care centres (use category 6)
- Sports halls, excluding swimming halls and ice rinks (use category 7)
- Hospitals (use category 8)
- Other buildings (use category 9)