In 2018, the residential sector accounted for 22.6% of final energy demand in Ireland. The Deep Retrofit Pilot Programme was launched to helps us to understand how to make our homes more energy efficient and reduce this overall demand. Check out our results to date.


There are approximately one million homes in Ireland with poor insulation and inefficient heating systems. As a result, a lot of heat is lost when we heat our homes. We need to keep the heat on longer in order to feel comfortable. In short, we are using too much energy to heat our homes.

In 2017, SEAI launched the Deep Retrofit Pilot Programme to address this very problem. The findings to date are informing our approach towards a large scale deep retrofit of our housing stock.

SEAI is committed to sharing learnings from the pilot programme. We will publish case studies of projects completed and provide access to more detailed information on suites of upgrades and technologies delivered.

Number of homes that received a deep retrofit

All homes completed through the Deep Retrofit pilot programme have achieved a BER A rating.

  • 7% have achieve an A1 rating (< 25 kW/m2/yr),
  • 34% have achieved an A2 rating (25-50 kWh/m2/yr) and
  • 59% have achieved an A3 rating (50-75 kW/m2/yr).
% of homes73459

Profile of homes

Age profile

Of the homes that underwent a deep retrofit:

  • 22% were built prior to 1950 - average pre-works BER of G (median: G)
  • 47% between 1950 and 1982  - average pre-works BER of F (median: F)
  • 31% between 1983 and 2005 - average pre-works BER of D2 (median: D2)
 Pre 19001900-19291930-19491950-19661967-19771978-19821983-19931994-19992000-2004
Age of homes291114 23 1114133

Breakdown of House Types

Deep Retrofit Pilot Programme vs National BER database

Deep Retrofit Pilot5030596
National BER Database282781419

Floor area by house type

Floor area by house type for Deep Retrofit Pilot vs National BER Database

Deep Retrofit Pilot (m2)16197818556
National BER Database (m2)159108949068

79.9% of the homes completed are detached or semi-detached. The number of mid- and end-of-terrace homes is 14.0% with apartments making up 6.1%.

Compared with the BER database, there is a higher proportion of detached homes in the Deep Retrofit Pilot Programme (50% vs 28%).

Note: for the purposes of direct comparison, the dwelling types 'maisonette', 'basement dwelling' and 'house' have been excluded from the BER database figures. The other dwelling types total in excess of 980,000 dwellings

Construction type

56% of the homes completed had a cavity wall construction. 87% of these homes were constructed between 1967 and 1999.

85% of the concrete hollow block homes were located in the east of the country (Dublin, Kildare, Meath and Wicklow), which is in line with what would be expected given the age profile of these homes.

52% of the solid mass concrete homes were built prior to 1950 with another 40% built in the period 1950-1966.

82% of the stone wall and solid block homes were built prior to 1930. All but one of these homes was built before 1950.

 Cavity wallConcrete hollow blockSolid block wallSolid mass concreteStone wall
Construction type58146149

BER Profile


29% of the homes upgraded to an A rating were G-rated before work commenced. 57% of these were built before 1967 with 24% built in the period 1967-1977.

  • 11% of homes were F-rated
  • 27% of homes were of E-rated
  • 30% of homes were D-rated

The average BER rating across the National BER Database is a D1 rating.

Pre works BER413152091128

BER Uplift

  • The average pre-works BER value across the homes was in the middle of the F rated band (417 kWh/m2/yr). The median value is 337 kWh/m2/yr, which is an E1 and only 3 kWh/m2/yr from being an E2
  • The post-works BER across all homes achieved A3 (52 kWh/m2/yr). This is significantly inside the A3 rating band and only 2 kWh/m2/yr from being an A2.
  • The average (and median) improvement in the BER value is 85% across all homes
  • As part of the application process, the designed post-works BER was provided to demonstrate achieving the A rating. The average post-works design BER at application was 59 kWh/m2/yr.

Air Tightness

  • Improving airtightness is an important element of delivering a high-performance home. Where airtightness is poor, heat may be lost through gaps in the house that are not visible. Poor airtightness is equivalent to having a large hole in your wall, even if the wall is well insulated.
  • Improving airtightness may significantly reduce the size of that hole. This will help reduce heat loss and draughts in the home, increase comfort and will also improve the performance of your heating system.
  • The average pre-works airtightness for the pilot homes was 10.1 m3/hr/m2. The average post-works airtightness across the entire homes is now 3.8 m3/hr/m2, a 63% improvement.
  • After the initial phase of the Pilot, we brought in a requirement that all homes must achieve an airtightness of ≤ 5 m3/hr/m2 and we provided a financial incentive for achieving ≤ 3 m3/hr/m2. Since that requirement was put in place, the average airtightness improved by 67% with 35% achieving ≤ 3 m3/hr/m2
  • This greater level of understanding of how to improve airtightness has resulted in the delivery of more energy efficient homes that are more comfortable to live in.
  • With increased airtightness, appropriate ventilation is necessary to ensure good indoor air quality. This is why SEAI require mechanical ventilation on all deep retrofit projects.

Pre-works Airtightness by Age

 Pre 19001900-19291930-19491950-19661967-19771978-19821983-19931994-19992000-20042005 onwards
Airtightness13.1311.4812.1810.92 9.40 11.788.938.8710.445.16

Airtightness (pre and post) by house type

House TypePre-Works Airtightness(m3/hr/m2)Post-Works Airtightness (m3/hr/m2)

Airtightness by wall type

Excluded timber frame and 'Unknown' due to small numbers

Wall ConstructionPre-Works PermeabilityPost-Works Air Permeability
Cavity Wall9.494.04
9" Hollow Block11.953.78
Solid brick12.533.79
Solid Mass Concrete9.913.15


The three main technologies installed on homes on the Deep Retrofit Pilot Programme are heat pumps, mechanical ventilation systems and soler photovoltaic systems to provide renewable electricity.

Heat Pumps

To date, all approved projects have air source heat pumps providing heating

Mechanical Ventilation

  • 83% of the mechanical ventilation systems installed have been Mechanical Extract Ventilation (MEV) or Demand Control Ventilation (DCV)
  • 17% of the systems installed have been Mechanical Ventilation with Heat Recovery (MVHR)
  • The average post-works airtightness of the homes with DCV is 4.1 m3/hr/m2  (pre-works airtightness: 10.1 m3/hr/m2)
  • The average post-works airtightness of the homes with MVHR is 3.1 m3/hr/m2  (pre-works airtightness: 9.8 m3/hr/m2)

Solar Photovoltaic (PV)

  • 69% of homes completed were aproved to have solar PV installed
  • 6% of the homes with solar PV installed have had a battery installed also.
  • The average solar PV approved where a battery was not included is 1.64kWp
  • The average solar PV approved where a battery was included is 3.14kWp


The average total capital cost to upgrade a home from an average BER rating of F rating to an average A3 rating is €60,814

Many people ask us how much it will cost to complete a deep retrofit on their home. This can be a tricky question to answer because it depends on many factors. Firstly you need to consider the the type of house, the size of the house, the age of the house, the starting BER and any works done since it was built. These will all influence the type of work required to bring it to an A rating.

Two significant drivers in the cost of an upgrade are the starting BER and the floor area of the house. The size is also an indirect function of age profile as the floor areas of the different house types change differently over time.

Early insights indicate that the degree to which these two variables impact on cost changes depends on the house type. For example, the correlation between cost per m2 and the pre-BER is much stronger for detached homes than semi-detached/end-of terrace or mid-terrace homes. The correlation between cost-per-m2 is strongest for mid-terraced homes. Further analysis is required to get more detail on the specifics driving the correlations but these are some of the trends and variables that will impact on cost at a high level.

The graph below below illustrates the difference between the level of improvement in the energy performance of Deep Retrofit Pilot projects and the improvement in the average BER in Ireland to the B2 target set for the retrofit of homes set in the Government’s Climate Action Plan.

In the very broadest terms, the wider the gap to target, the higher the costs are likely to be. 

In addition, Deep Retrofit Pilot projects also included mandatory elements such as mechanical ventilation and achieving airtightness targets.

The cost provided is an average cost across all homes completed to date, which includes a broad range of construction types, sizes of homes, starting BERs, etc. We will soon be publishing case studies of projects completed and provide more detailed costs for different house types etc. to give examples of different house types that have gone through a Deep Retrofit. The case studies will give details on the types of energy upgrades and the costs involved.

Case Studies

Below are some case studies of some homes from the Deep Retrofit Pilot Programme