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What is the difference between Deep Retrofit and a Shallow retrofit?

A deep retrofit of a home is a whole house system approach where a number of energy saving measures are done at the same time to radically reduce energy use by between 30 and 70% and to increase comfort. A plan is created to make sure the house performs as one system and reaches the best possible performance targets. With deep retrofit, all aspects of the house from the fabric to ventilation and heating systems are considered within the same plan rather than treated separately. A deep retrofit is the best option for reducing CO2 emissions and living a sustainable lifestyle.

A shallow retrofit is a small-scale alteration where one or two energy saving measures are taken. This can include single measures such as insulation around pipes, changing boiler, changing windows or installing insulation in different parts of the home. A shallow retrofit can initially seem cost effective, although it can actually be less beneficial in the long run and more costly, if you have to redo the work in order to achieve further energy reductions which will be required by 2050. Therefore any single measure should form part of a long term plan for the home that can build step by step towards a deep energy retrofit without having to redo previous steps. It is worth getting advice on how you can do this from a qualified renovation advisor.

In a deep retrofit, tests are carried out before and after the retrofit works to show the improved performance of the home and improved Building Energy Rating (BER) of A or B.
From a carbon and energy perspective, a deep retrofit is the best action you can take. Increased thermal comfort, indoor air quality, sunlight and daylight, and acoustic comfort will also contribute to improving the comfortability as well as value of your home.

The overall work may take between 8 – 12 weeks and can be disruptive if the floors or walls are insulated. Deep retrofit works can also be phased to suit budget and time constraints. However a Deep retrofit must be planned to ensure that works are done in the right sequence and do not obstruct or prevent future upgrades. The costs for a deep retrofit can be high if all the work is done at once – between €30,000 – €60,000. However you can do a deep retrofit in phases, over a number of years so the costs are spread out. Now SEAI are offering up to 50% grant cover if you apply through a registered one-stop shop grant. SEAI have also improved the value of their single measure grants. For more information about One Stop Shops and how they work please click this link.

A deep retrofit involves a Fabric First approach by reducing the level of heat loss by insulating some or all of your home including your walls, roof and floor and making sure the building is airtight. This can also involve upgrading windows and doors. A mechanical ventilation heat recovery [MVHR] system should be installed alongside the insulation to maintain good indoor air quality providing a healthy environment and preventing mould.

Renewable energy technologies such as solar water heating or solar photovoltaic panels may be appropriate for your home after carrying out deep retrofit.

If your budget allows, a deep retrofit in one go is advantageous because your house is approached holistically, as an overall system of interdependent parts. Performance will be significantly improved and you will feel the difference in warmth, comfort and healthy indoor air quality. Alternatively, if you cannot afford to pay for it all in one go, a phased plan could be created so you can do it step by step according to the overall plan.

Here’s a short video explaining what deep retrofit is, the process, and how the homeowners felt when they moved in after it was done

Home for Life(Home Deep Retrofit) EE17 EP2


Here’s a 20 minute video explaining why deep retrofit is the best option. Start watching at 3.12.

This video explains what deep retrofit is, why it is the better option over shallow retrofit as well as the most common mistakes in building that lead to energy inefficient homes and how to avoid that. It uses a real life case study to show what results can be achieved.


A shallow retrofit is where small improvements are made to different parts of the house over time.

Shallow retrofit may include:

  • insulating hot water pipes
  • putting an insulating jacket on your boiler
  • pumping insulation into the cavity wall
  • upgrading the attic insulation
  • upgrading the boiler to a more efficient one
  • adding a heating control system

Shallow retrofit measures can be implemented a step at a time but it is better to do them according to an overall plan developed by a renovation adviser. The level of energy savings will depend on the measure. For example if your home is very draughty and poorly insulated it may be currently impossible to heat it properly no matter how much energy you use as the heat goes straight out the walls, windows and roof. Initial measures such as insulation, draft stopping, attic insulation may just help increase your level of comfort without making significant energy savings. As you carry out subsequent measures you will start to see energy savings also.

The costs depend on the work done, for example replacing the boiler could cost approximately €2500 – €4000, and an insulating jacket on the hot water tank costs about €30.

If you want to make small changes but are not quite sure where to start, you can go to your local library and get a Home Energy Savings Kit created by Codema, Dublin’s Energy Agency. You can use this kit to see where some of the issues are and make small changes immediately. Please visit their website to find out where you can get it and how the kit works. https://www.codema.ie/think-energy-home-hub/the-home-energy-saving-kit/

Planning your overall retrofit ensures you invest sustainably and will not need to remove work in the future, for example, addressing building fabric performance and ventilation together. Or if you’re installing external wall insulation do your windows and doors at the same time or vice versa. If the fabric of your house has been brought up a good level of insulation it is worth looking at installing a heat pump rather than installing a new boiler which may need to be replaced to get you to the next level of efficiency.

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