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12 March 2020

The true cost of NZEB in practice

The background to NZEB 

The EU Energy Performance of Buildings Directive which affirmed that all new building constructed in member states will be near zero energy buildings (NZEB) by December 31, 2020, and all new buildings owned and occupied by public authorities must be NZEB-compliant after December 31, 2018 has now been incorporated into Part L Building Regulations.

The key parameters for measuring NZEB compliance are the maximum permitted energy performance coefficient (MPEPC), renewable energy ratio (RER) and maximum carbon performance coefficient (MPCPC). Each method within the NEAP framework will calculate the EPC and CPC of the building being assessed, and clearly indicate whether compliance with regulations has been achieved:

  • Where the MPEPC of 1.0 and MPCPC of 1.15 is achieved, an RER of 0.2 or 20% represents a very significant level of energy provision from renewable energy technologies
  • Where the MPEPC of 0.9 and MPCPC of 1.04 is achieved, an RER of 0.1 or 10% represents a very significant level of energy provision from renewable energy technologies

Meeting NZEB 

Commercial schemes 

Since the revised Part L regulations have been introduced, Linesight has been involved in numerous commercial and residential projects, and the uplift to M&E installations is circa. 7-10% when benchmarked against historical projects. Ultimately, these new regulations are adding capital costs to developers.

In commercial office buildings in Ireland, there are numerous items to be undertaken to ensure compliance is achieved:

  • Use of renewable sources – photovoltaics (PVs), air source heat pumps (ASHP) etc.
  • Fabric insulation and reducing thermal bridging
  • Enhanced building controls
  • Limiting air infiltration
  • Enhanced commissioning
  • Specific fan power reduced for various systems

At Linesight, we are seeing the above having impacts across the mechanical installation in a standard four-pipe FCU CAT A development, and these include the following:

  • Upsizing of FCUs to enable lower temperatures from ASHP
  • Upsizing of pipework to enable lower temperatures
  • Costs associated with specific fan power across all plant items
  • Ductwork leakage testing mandatory on high-pressure ductwork
  • Increase in costs of BMS to cater for additional building controls
  • Increase in commissioning requirements to meet minimum standards

In most commercial office projects in city centre locations, it may be difficult to meet the RER 0.2 by changes to the above systems due to site constraints, so it is also advised to make the façade as efficient as possible, as this reduces the energy loss of the building. There is no one way to gain compliance with regulations, however. Whichever approach is taken, the M&E systems are affected and generally, when our benchmarks are looked at, the M&E element is increasing in cost by circa. 7-10%, as referenced earlier.

Residential projects:

Linesight is also involved in numerous large-scale apartment schemes, whereby various technologies are being used in order to meet the new NZEB requirements. 

Where a building contains more than one dwelling, like a block of apartments, it has to be shown that every individual dwelling has an EPC and CPC no greater than the MEEPC and MPCPC respectively. Alternatively, it must be shown that the average EPC and CPC for all dwellings in the building is no greater than the MPEPC and MPCPC respectively.

The Part L regulation standards must be achieved for both apartment and landlord areas. The key client decision to make is the mechanical system to be installed, which can be summarised as follows:

  1. EAHP (exhaust air heat pump) in each apartment for water heating, MVHR unit for ventilation requirements, electric heaters for space heating, PV required on roof
  2. EAHP for space, water heating and ventilation requirements, minimal PV panels required
  3. District heating (ASHP) to HIU in each apartment for space and water heating, MVHR unit in each apartment, PV required on roof

Currently in the Irish market, the most common solution is the EAHP as a one-stop solution in each apartment for space, water heating and ventilation requirements. However, the most cost-effective solution to meet NZEB requirements is option 1 above, utilising electrical heaters, around which there remains a stigma, meaning that developers and agents are slow to commit to them.


In summary, the new NZEB regulations have a distinct impact on the clients developing Grade A commercial space and large-scale residential apartments, as it increases the cost of construction projects, so the developer may feel that they are not seeing a sufficient yield to warrant this additional cost.

However, the flip side of the coin is that the developer is getting a higher quality building with a reduction in running costs, and also a higher specification of building services. This is down to the increased commissioning requirements, as well as the quality increase in monitoring and building management systems.


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