Insulating older and solid-wall homes in Ireland

The essentials

Understand the house before choosing a wall system

Traditional stone, brick or earth walls manage moisture differently from modern construction. Age and a solid-looking wall are clues, not a complete survey.
Repair water entry and investigate damp before covering the building. Ask a professional experienced in traditional construction to plan the work.
The Traditional Homes Pilot supports a whole-house upgrade through a suitable One Stop Shop and a Traditional Building Professional. It does not require a final BER of B.
Check heritage and planning requirements with the council before agreeing the design. Grant approval does not replace any necessary permission.

Is your house traditionally constructed?

Many Irish homes built before the 1940s have solid stone, brick or earth walls, often with lime mortar and plaster. Mortar joins the masonry; render is the protective coating on the outside. These walls can absorb moisture and release it as conditions change. Adding insulation changes their temperature and drying behaviour.

Not every old house uses this construction. Early solid concrete walls, hollow concrete blocks and later cavity-wall extensions need their own assessment. Hollow blocks contain spaces within the blocks; they are not the continuous gap between two separate walls used for cavity insulation. One house may contain several wall types behind similar finishes.

Ask a conservation-experienced architect, engineer or building surveyor to identify the walls, roofs, floors and later alterations. Agree where they need to remove small areas of plaster or other finishes to inspect hidden construction, including any consent needed. Do not order cavity fill because drilling has found a void in rubble stonework.

The Department’s traditional-building guidance distinguishes this construction from modern solid concrete and cavity walls. Our internal and external wall guides explain those methods generally; a traditional home needs the additional checks here.

Start with water, condition and comfort

Tell the surveyor which rooms are cold, how you heat them, and where damp appears. Bring old drawings, repair records and dated photographs if you have them. An energy rating alone cannot show the condition of hidden timbers or diagnose a wet wall.

Ask for an inspection of roof coverings, gutters, downpipes, chimneys, external walls and ground levels. Leaks, wind-driven rain, plumbing faults and condensation can need different remedies. A damp patch is evidence to investigate, not proof of one cause or a reason to cover it immediately.

Have the professional specify repairs, suitable materials and sufficient drying time before insulation begins. Existing cement coatings or impermeable paints may affect drying; whether and how to remove them needs assessment, including the risk of damaging historic material. Do not strip finishes or inject a damp treatment solely on a sales recommendation.

Keep the upgrade goals concrete: warmer occupied rooms, reduced draughts, lower energy use and a manageable budget. Ask which improvements offer useful comfort with the least disturbance before committing to wall insulation. The SPAB’s solid-wall research found that assumed heat loss can overstate what old walls actually lose. That is a reason to assess the building, not a promise that every thick wall already performs well.

What does a suitable wall-insulation design consider?

“Breathable” generally means a material allows water vapour to pass through. It does not mean the room receives fresh air through the wall, or that any product carrying the label is suitable. Insulation, adhesives, plaster, render and paint must work together with the existing wall and the site’s weather exposure.

Ask the designer for a moisture-risk assessment of the proposed wall layers: how rain and indoor moisture enter, move and dry before and after work. They may need specialist calculations or modelling of heat and moisture over time. Ask what the assessment covers, what assumptions it uses and which risks remain. A product brochure or a simple insulation-thickness recommendation is not that assessment.

Insulation on the inside

Internal wall insulation leaves the exterior visible but uses room space and can cover historic plasterwork, shutters, skirting or decorative ceiling edges. It also leaves the original masonry colder. The design must address drying and timber ends embedded in the wall, such as the ends of floor-supporting beams.

Ask how insulation meets windows, doors, internal walls, ceilings and floors. Gaps at these connections can leave cold areas where condensation forms. Have drawings show the finished room dimensions, sockets and pipes, features being kept and reinstatement: finishes or fittings that must be repaired or put back after work. Do not assume a thin lining behind a radiator resolves the whole wall.

Wall section, outside left and room right. Brown hatching is the old wall; yellow is insulation. Moist room air entering an unsealed edge or socket can condense on the colder wall behind the lining (blue drops). The gap is exaggerated to show the air route. Ask for a moisture-risk design and sealing details for your wall. Schematic, not a construction detail.

Insulation on the outside

External insulation can keep the masonry warmer and preserve internal room space. It changes the façade, the outside face of the building, and may conceal stonework or decorative details. Its suitability depends on heritage value, weather exposure, moisture behaviour and permission as well as thermal performance.

Ask for details at roof edges, window sills, doors, pipes, ground level and adjoining properties. The complete system needs a compatible finish and water-shedding details. A sample of insulation board does not establish that those connections can be built safely or that changes beyond your boundary are agreed.

There is no universal winner between inside and outside. The designer may recommend different approaches for different parts of the house, or leaving a sensitive wall uninsulated while improving other areas. Ask them to explain the comfort benefit, risks and limitations of the chosen plan.

Coordinate the roof, floor and ventilation

Use our whole-house priorities guide to plan the sequence. A traditional-house plan should connect each job to the next, including:

Roof and attic: check roof condition, historic ceilings and the required airflow around timbers. Ask the designer to show how insulation and draught sealing will leave the roof’s required ventilation paths open. See the attic guide.
Floors: identify whether timber is suspended over a ventilated space, or the floor is solid. Plan timber repairs, retained finishes and moisture at the wall edges before excavation or new floor layers. See the floor guide.
Room air: specify deliberate fresh-air supply and extraction when draughts are sealed. Wall moisture permeability does not replace ventilation. Keep necessary air supplies for stoves and other fuel-burning appliances clear; coordinate any changes with the qualified appliance installer. See the ventilation guide.
Heating and controls: have the heating designer use the proposed finished house, rather than its current draughts, when assessing later equipment. Retaining a historic window may be compatible with repair, draught proofing or secondary glazing, an extra glazed panel inside the existing window; agree its suitability with the designer.

Ask your local council whether the property is a protected structure, proposed protected structure, or in an Architectural Conservation Area (ACA), an area with special architectural character. Check its current development plan and protected-structure record. Protection can affect internal features as well as the outside; an ordinary planning exemption cannot simply be assumed.

Take the proposed scope, photographs and drawings to the council’s architectural conservation officer or planning service early. Ask which permissions or written declarations are needed for these specific works, and obtain them before starting. Dublin City Council’s conservation service illustrates the advice available; owners elsewhere should contact their own council.

The designer should also establish the applicable building-regulation requirements. An energy grant is funding approval, not planning consent or a blanket exemption from building regulations.

Which SEAI grant route applies?

SEAI is the Sustainable Energy Authority of Ireland. Its individual-grant support page, section 2.5, lists attic insulation, heating controls, solar water-heating panels (solar thermal) and electricity-generating solar panels (solar PV) for traditional homes, subject to each grant’s conditions. It explicitly excludes traditional homes from the individual wall-insulation grant and directs wall-upgrade projects to the Traditional Homes Pilot. Do not apply the standard wall figures from an online calculator to your traditional house.

The Traditional Homes Pilot uses a One Stop Shop providing traditional-home services and a Traditional Building Professional: an architect, engineer or surveyor with the relevant conservation competence and upgrade experience. Ask about accreditation; a professional without conservation accreditation needs SEAI’s prior review of supporting qualifications and experience. The professional designs and oversees the appropriate work; the One Stop Shop manages the grant and project delivery with them.

The current pilot guide, version 3.0, requires a whole-house approach, rather than a single wall-insulation job. It does not require a final Building Energy Rating (BER) of B or better. Work already started is excluded, and the same measures cannot have previously received SEAI support. Have the provider confirm eligibility, supported measures and approval before work starts. Ask for the full price, grants deducted and remaining payment; our grant-route comparison explains the ordinary routes, whose conditions differ.

What should the quote and handover include?

Ask for a written scope showing the assessment and design fees, repairs and drying time, consent work, insulation system and finishes, ventilation, site access, reinstatement, VAT and exclusions. Separate funded work from repairs or professional costs you must pay yourself. Agree how hidden defects will be reported and priced before extra work proceeds.

Request examples of completed traditional-home work and speak to previous clients. SEAI registration for an insulation measure does not by itself demonstrate conservation expertise. Identify who is responsible for design, inspections, workmanship and defects, and when they will inspect work before it is concealed. Our contractor guide has a wider comparison checklist.

At completion, keep the agreed drawings, product and finish details, photographs of hidden work, inspection and completion records, ventilation instructions and warranty contacts. For pilot work, agree the before-and-after BER arrangements and grant declarations with the One Stop Shop and Traditional Building Professional. Ask what to monitor afterwards and whom to contact if damp, cracking or condensation appears.

Use the costs and grants checker for general insulation context. Its ordinary wall-grant figures do not confirm support or price a traditional-house project. A surveyed design and itemised provider quote are your next steps.

Common questions

Can a solid stone wall have cavity insulation?

A solid wall has no continuous cavity between inner and outer walls to fill. Gaps in rubble stonework are not that cavity. Have the construction surveyed, including extensions, before choosing a system. Internal or external insulation may be possible, but each needs a moisture and heritage assessment.

Does every pre-1940 home qualify for the Traditional Homes Pilot?

No. SEAI describes traditional construction as typically pre-1940, but age alone does not establish eligibility. The pilot requires a whole-house approach, a Traditional Building Professional and a One Stop Shop providing traditional-home services. Single-measure jobs, work already begun and previous support for the same measures affect eligibility. Confirm the proposed project with the provider before starting.

Must a traditional home reach BER B to receive pilot funding?

No. The current Traditional Homes Pilot guide says a post-work BER of B or better is not required. The plan must use appropriate measures in a whole-house approach that respects the construction and heritage value. This exception does not remove the ordinary One Stop Shop scheme's conditions for other homes.

Is internal insulation always the safer choice for an old house?

No. It can preserve the outside appearance but make the original wall colder and change how moisture dries. It also affects room space, internal features and timber ends inside walls. External insulation changes the outside and needs its own moisture, junction and consent checks. Ask the designer to compare suitable options for the actual building.

Sources and review

Sources were last checked on 30 October 2026. The review checks published guidance; ask a contractor to survey and design the work for your home.