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All About Retrofitting

All About Retrofitting

By the end of last year, close to 27,000 homes were upgraded with grant supports from SEAI following the launch of the SEAI National Housing Retrofit Scheme in February 2022. Studies show that improving your home's Building Energy Requirement (BER) adds value to your property and that advancing by a single level, from C2 to C1, for example, equates to a 1% increase in property value.

Even with the increased Sustainable Energy Authority of Ireland (SEAI) grants to cushion the cost, the decision to retrofit the house you have been living in for years is a significant undertaking.

A deep retrofit encompasses everything from attic and wall insulation; new windows and doors; conversion of heating system from gas/ oil to a heat pump; advanced ventilation and photovoltaic (PV) solar panels for electricity generation. It places substantial demand on homeowners who must decide whether they can afford both the financial outlay and the domestic upheaval of a deep retrofit. It is hugely inconvenient to have to vacate your home for four to eight weeks while the project is being undertaken. However, increasing numbers of people living in damp, cold homes which are expensive to run, are willing to accept temporary hardship in return for a warm, comfortable, energy-efficient home that is healthier and significantly cheaper to run.

A deep retrofit that raises a home’s comfort and energy performance to a minimum B2 BER standard or better can be achieved by selecting a ‘One Stop Shop’ service which provides a range of energy-focused improvements overseen by a single contractor who manages the entire project from start to finish, including the grant application. This makes the whole process relatively trouble- free for the homeowner, who also benefits from getting the grant paid to them upfront, deducted from the cost of works. The One Stop Shop then claims the grant back from SEAI on completion of works.

In cases where the required work is prohibitive to undertake in a single, stand-alone project, homeowners can pursue the individual grant option, allowing them to pursue incremental improvements as time and budget permits. This option provides flexibility and enables homeowners to make steady progress on achieving their domestic energy efficiency goals.

Regardless of the solution decided upon, the first step on your retrofit journey is to have an energy assessment of your home. This assessment, which costs between €400-€700, is carried out by an independent assessor and includes a full technical assessment of the fabric of the house as well as tests for air tightness and heat loss. An assessment of the current BER rating and what measures will be required to bring the home to a BER of B2 is also included. A grant of €350 is available for this purpose from the SEAI.

A comfortable BER of B2 (125 kWh/m2/yr) is the broadly accepted baseline for completing a deep domestic retrofit.

About 60% of the energy in our homes is used for heating to keep it warm and comfortable and we use about three times more energy to heat our homes than we do to power our appliances, mainly because of the prevalence of low-quality housing in Ireland which leak a large amount of heat. A significant impact can be made by reducing the amount of energy required to keep homes warm and moving towards using non-fossil fuel based energy sources.

In a typical home, most of the heat is lost through walls and the roof, so these areas are generally the first focus of an energy retrofit: improve the insulation of walls, roof and floor; upgrade windows and weather strip the doors and windows. Once the house has been fully insulated and sealed, the next step is to replace fossil fuel-based heating systems with more sustainable heating, renewable technologies and heating controls.

Finally, with the building more tightly sealed, managed ventilation, mechanical and passive, can be installed to ensure that the air is guarded against excess humidity.



Insulation is the first and most crucial step of the retrofitting process. Regardless of the insulation type you choose, research shows that you will feel an improvement in comfort and heat loss will reduce significantly. In a study of nine lower to upper-middle income Irish homes, cavity insulation reduced heat loss through walls by up to 66% and external insulation by up to 77%, with all participants reporting excellent comfort levels.

The attic is one of the biggest areas of heat loss in the home. Retrofitting and insulating your attic pays substantial dividends. When attic spaces are insulated, heat is kept below the ceiling and circulates inside the rooms. Proper attic insulation is the best way to prevent heat losses in the winter and retain cool air in the summer.

Current building regulations and SEAI guidelines recommend a minimum of 300mm of insulation on rafters above ceilings, or 150/200mm of open-cell insulation spray foam between rafters.

In the majority of homes, a thick layer of insulating material, such as a blanket material, will be rolled out between and over ceiling joists. For large roof spaces, spray foam insulation, which delivers greatly improved airtightness and can be sprayed between rafters (roof uprights) once a suitable breather card is fitted. Another technique involves the use of loose-fill insulation. Loose-fill insulation is a good choice for insulating attics with very little headroom as well as multiple obstructions, such as vents and cross-beams. Loose-fill insulation can also be blown over existing insulation and is available in fibreglass, cellulose, and mineral wool form.

With new attic insulation, proper ventilation is required to reduce the risk of condensation build-up in the attic space, which, if left unchecked, can harm the effectiveness of your insulation and cause damage to the roof structure. It is also important to ensure that pipes and tanks are properly lagged to prevent freezing and leaks.

About 35% of a home’s heat is usually lost via external walls. Any extent of insulation- related heat loss can essentially be eliminated by insulating the walls so that more heat is retained within a home. There are various ways of insulating a home’s walls and you first have to decide whether you are opting for external, internal or cavity wall insulation.

Cavity wall and ceiling insulation are the cheapest and least disruptive solutions, with the shortest payback period. A series of small holes are drilled in the wall, at regular intervals, on the outside of your home. The insulation is then pumped through these holes to cover the cavity and the holes are filled in to match the rest of the wall. Cavity wall insulation ensures that heat is not lost through the cavities present on the walls.

If your home doesn’t have cavity walls, you will need to insulate internally (also known as dry lining) or externally. The internal option can also be used in addition to cavity wall insulation to further improve the performance of a home’s external walls. External wall insulation usually involves wrapping a layer of stable and rigid insulation around your home and embedding a mesh into it to provide extra strength. Such insulation can also be covered with a render to provide weather resistance.

External insulation costs about twice as much as internal insulation, but in terms of its thermal benefits, it is generally the best option if the cost falls within your budget. It is also much less disruptive, but you need to bear in mind that it can only be carried out after new windows and doors have been installed.

Meanwhile, internal wall insulation can be applied when your home has solid or cavity block walls. In this case, it means that external wall insulation is either not possible or not considered the best solution. This insulation process usually involves fixing insulation boards to the inside of the external walls and covering them with a distinct vapour control layer.

Walls can also be covered with plasterboard, skimmed and new paint to make the wall aesthetically appealing. Since boards are installed on the inside of a house, there will be a loss of space in the rooms. Dry-lining applied to internal walls is much more intrusive as everything will have to be removed from the walls before the job can be started, and it will take two to three days to dry-line each room, depending on its size.

SEAI offers generous grants (for example, €6,000 for a detached house) towards insulation upgrades.

Another frequent culprit for heat loss in the house is the floor, usually because it hasn’t been adequately insulated or is badly fitted. Your contractor will advise you on whether you need to take up the floor and insulate the slab, and you might also consider installing an electric underfloor heating system under the laminate floor that can be wired back into your house.



Homeowners embarking on a retrofit should be aware that windows and doors are in high demand and it can take up to 12 weeks for them to be delivered to site. This time frame has to be factored in, as external insulation and heat pump installation cannot be done until the new windows and doors are in.

Doors and windows are one of the most common areas where heat is lost in the home. While replacing your windows might entail a significant upfront cost, it will result in immediate energy savings and improved comfort. If you cannot afford to acquire the best windows, then consider choosing a more affordable option on the market that is not as good as the best quality available, but improves your home. Depending on the age and condition of your window frames you could  consider a glazing only upgrade. This would entail removing existing glass and replacing it with the latest low-emissivity (Low E) glass, which has special coatings and gas filled units that are very effective for retaining heat with little or no decoration required afterwards.

For doors, the most efficient have steel frames with a foam insulation core. Steel doors are cost-effective as well as safe and greatly reduce actual consumption levels in a home.

Sliding doors usually have higher air leakage rates even when weatherstripping methods are applied. Generally, hinged doors are more efficient than sliding doors, but if you happen to prefer sliding doors to protect your home from the elements, choose the ones with metal frames and a thermal break for maximum efficiency. A thermal break is a plastic insulator between the exterior and interior parts of the frame.


Usually, heating and cooling systems can be responsible for as much as half of the energy consumed in a given home and it is a significant energy expense for many Irish homes. Renewable energy systems provide heat or electricity to your home without burning fossil fuel and are a staple requirement of a deep retrofit. There are a wide range of renewable energy systems available on the market, including heat pumps, solar water heating panels and solar photovoltaic panels.

Older gas and oil-fired boilers waste energy and are costly to run due to the amount of fuel they need to maintain comfort levels and hot water in the home. By replacing an older gas or oil boiler with a heat pump system you can transform comfort levels and create a healthier home, while also reducing energy usage and eradicating oil and gas bills.

The most common heat pump systems extract heat from external air, using an outside unit. These heat pump systems do not need underground piping to source heat. This means they can be cheaper and easier to install compared to ground source heat pump systems.

The most popular heat pumps are air to water heat pumps which distribute heat through radiators or underfloor heating and also produce hot water while a ground-source heat pump system uses the earth as a source of renewable heat and extracts heat from the ground through a collector pipework and transfers it to the heat pump. Meanwhile, water source heat pump systems use open water, such as lakes, rivers or streams as a heat source.

To install a heat pump system, you must ensure your home is well insulated and that you have good double or triple glazed windows. In this way your heat pump system will perform well, and your electricity bills will be lower.

Most heat pump systems have integrated heating controls, helping you to accurately match your space heating and hot water schedules to the working and living patterns in your home, so when heat and hot water are required, it is there; and when it is not required, it is turned off. Using the heating controls in your heat pump system will typically reduce your energy usage by up to 20%.

It takes between two to three days to install air-to-water heat pumps. These units - which look like air conditioning units - have replaced the ground-source-to-water heat pumps, which take longer to install and are more disruptive because of the need for underground works.


There is also a €700 grant available through the SEAI Home Energy Grants programme to help homeowners improve their home heating system by installing heating controls.

Home heating systems without heating controls can be wasteful of energy and costly to run because there is little to no control of the amount of heat being used to heat your home and your hot water. Adding modern heating controls can help you to accurately match your space heating and hot water schedules to the working and living patterns in your home, so when heat and hot water are required, it is on and when it is not required, it is turned off.

Thermostats usually monitor temperature fluctuations  and  communicate  with the heating and cooling systems. They communicate when to turn the temperature system on, or off. A good thermostat will eliminate broad swings in room temperatures and moderate the flow of heat efficiently and reliably to your own preference. 

A programmable thermostat will allow you to set the desired temperatures and the heating and cooling processes will take place automatically. A high-end electronic or smart thermostat may cost more than electromechanical thermostats, but it will offer better gains in the long run.


Even in Ireland’s climate, solar energy can contribute to your home’s energy needs and can be used to generate electricity or heat your water. Sustainable Energy Authority of Ireland offers grants of €1,800 for the first two solar panels installed, and an additional €300 per solar panel after that up to a maximum of €2,400.

A domestic solar PV system consists of several solar panels mounted to your roof (or in your garden) and connected into the electrical loads within your building. The solar panels generate DC (direct current – similar to a battery) electricity, which is then converted in an inverter to AC (alternating current – the electricity in your domestic socket). Solar PV systems are rated in kilowatts (kW). A 1kW solar PV system would require 3 or 4 solar panels on your roof.

Any excess electricity produced can be stored in a battery, or other storage solutions such as  a hot water immersion tank. The excess can also be exported from your house into the electrical network on your street.

There are two types of solar panels available: Solar photovoltaic (PV) which generate renewable electricity from the sun and can power all electrical devices in your home; the second being Solar thermal collectors, which use the sun’s energy to heat your hot water.

It is advisable to maximise the amount of solar electricity you use in your home. The size of the solar PV system you purchase will depend on several factors, including the amount of electricity you use in your home, the time of day you are at home and the orientation of your roof. Your selected installer should discuss all of the above factors with you and will also check your current and past electricity consumption to calculate the appropriate system size.

According to ESB Networks (ESBN), in the first eleven months of 2022, 16,946 solar PV systems were installed and they are anticipating a further increase in 2023 due to the new tariff provided for selling power back to the grid (MSS) and the removal of planning restrictions for domestic arrays, however this restriction only took effect in the final quarter of last year and ESBN are currently averaging over 300 new applications every week.

It takes about a day to install solar PV panels and most homeowners will opt to install six panels to contribute to their electricity needs.

With the rise in kWh unit prices from suppliers, the payback period for PV is now more favourable and is estimated seven to ten years for a moderately sized system of 3kW - 4kW. There are design and positioning considerations around the installation that are obligatory conditions to release the SEAI grant aid and the SEAI will carry out a site visit as an audit before the grant is released.

According to the SEAI, other works such as attic and roof installation and cavity wall insulation can pay for themselves through reduced energy bills in as little as one to two years.

The cost of a whole house retrofit depends on many factors, including the size and age of the house, the type of walls and what measures have already been completed. Costs range from €25,000 for a typical house built since the year 2000 to €75,000 or more for older, larger, or more complex homes.

The SEAI provides grants of up to 50% of the cost of a deep retrofits, up to a maximum payout of €25,000 and most of the main lenders, including Bank of Ireland, AIB, Credit Unions and An Post also offer preferential rates for retrofit work on your home.

However, a higher BER could add substantially to your home's value, which will also be significantly healthier and more comfortable and considerably less expensive to run - all good reasons for homeowners to consider taking the plunge.

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