In 2017 the residential sector accounted for 22.1% of final energy demand in Ireland. The Deep Retrofit programme is helping 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.

Future Case Studies and Data Sharing

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. We will include costs associated (including on a regional basis) and post-works energy performance data of the homes retrofitted. We will continue to provide updates on an ongoing basis, within the constraints of data privacy and GDPR.

Number of homes that received a deep retrofit

To date, 250 homes have participated in the Deep Retrofit pilot programme. All have achieved a BER A rating.

  • 14 have achieve an A1 rating (< 25 kW/m2/yr),
  • 68 have achieved an A2 rating (25-50 kWh/m2/yr) and
  • 168 have achieved an A3 rating (50-75 kW/m2/yr).

Energy Savings

The total energy savings from the 250 homes is 9.16 GWh/year and the total CO2 savings are 2.56 tonnes of CO2/year. These figures are calculated based on the pre-works BER (carried out before the work started) and the post-works BER.

No. of homes1468168

Profile of homes

Age profile

Of the 250 homes that underwent a deep retrofit, the largest proportion were built 20-25 years ago. The average pre-works BER of those homes was an E1.

35% of the homes were built across two age bands between 1967 and 1982. The average BER across all of these homes was G, indicating a very poor energy performance.

 Pre 19001900-19291930-19491950-19661967-19771978-19821983-19931994-19992000-2004
Age of homes15811181710291

House type

71.2% of the homes completed are detached or semi-detached. The number of mid- and end-of-terrace homes is 19.6%.

House type33388119

Construction type

70% of the homes completed had a cavity wall construction. These made up a significant proportion of the homes in the age bands from 1967-1977.

86% of the concrete hollow block homes were located in the east of the country (Dublin, Kildare, Meath and Wicklow).

50% of the solid mass concrete homes were built in the period 1950-1966 with another 36% built in the period 1930-1949.

58% 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 type7084144

BER Profile


27% of the homes upgraded to an A rating were G-rated before work commenced. 43% of these were built before 1967 with 34% built in the period 1967-1977.

The average BER rating across the 820,000+ homes with a BER is a D-rating and close to a D2 rating in line with the largest cohort of the pre-work BERs.

Pre works BER47262071027

BER Uplift

  • The average BER value across the 250 homes was in the middle of the F rated band (415 kWh/m2/yr).
  • As part of the application process, the proposed post-works BER for all homes was submitted. The average proposed BER was an A3 (60 kWh/m2/yr).
  • The actual post-works BER across all homes achieved A3 (54 kWh/m2/yr). This is significantly inside the A3 rating band and close to an A2.
 BeforeProposed afterAfter
BER uplift4156054

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 250 pilot homes was 9.9 m3/hr/m2. The average post-works airtightness across the entire 250 homes is now 3.9 m3/hr/m2, a 61% 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 70%.
  • 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.


250 homes have completed deep retrofits under SEAI’s pilot programme to date. The average cost to upgrade a home from an average BER rating of F rating to an average A3 rating is €48,417

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.

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 the 250 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.