Clare Cottage, Kinsale Retrofit (BER F to B1-Rated)
Advisory role for a self-build energy upgrade
 

Project overview

This project involved the energy retrofit of a late 19th-century stone dwelling in Kinsale. The building comprised an original low-ceilinged front house and a converted agricultural structure to the rear, opening onto a terraced garden.

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RUA Architects acted in an advisory capacity, supporting a self-builder client with limited construction experience. The ambition was clear but challenging: to achieve an A-rated home while retaining the character of the building and maintaining cost control.

 

Strategic approach

Given the constraints of a traditional stone structure—particularly the absence of any viable external insulation strategy—the focus was placed on optimising the building envelope from within.

The approach prioritised:

• reduction of overall heat loss

• moisture-safe upgrading of the fabric

• retention of breathability in the existing construction

• targeted intervention rather than wholesale replacement

Particular attention was paid to the hierarchy of heat loss: roof, walls, windows/doors, and finally floor.

 

Fabric and moisture strategy

Walls

The external walls were finished in sand and cement, preventing outward drying. As a result, all internal insulation strategies needed to allow inward vapour permeability.

A breathable internal insulation system was adopted, using wood fibre boards (Steico and Gutex Thermaroom), each assessed through WUFI hygrothermal modelling by specialist suppliers. Both systems achieved a U-value of approximately 0.33 W/m²K within acceptable interstitial condensation risk parameters.

The build-up included:

• removal of internal finishes back to stone/lime substrate

• levelling scratch coat

• 100mm wood fibre insulation

• internal lime plaster finish (approx. 20mm)

Different wall conditions required nuanced responses. For example, areas such as first-floor bathrooms introduced higher internal moisture loads and were treated accordingly.

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Roof

The roof represented the most effective opportunity for heat loss reduction.

Measures included:

• repair of tiles, ridge detailing, and chimney flashings

• replacement of rainwater goods

• installation of 325mm blown cellulose insulation

Cellulose was selected for its hygroscopic properties and reduced risk of summer overheating compared to petrochemical alternatives.

Pitch in converted shed hadled with PIR and Ecocel in the flat roof. 

Critical junctions—particularly where pitched roofs met flat sections—were carefully detailed to maintain continuity of insulation.

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Windows and doors

Existing PVC windows were replaced with heritage-style triple-glazed timber sash units. These improved both thermal performance and acoustic comfort while maintaining architectural character.

Installation strategy included:

• insulated reveals (Bosig/Skamowall, approx. 30mm)

• airtightness taping internally and externally

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Floor

As is common in Kinsale, the existing floor presented significant complexity and risk. A decision was made not to intervene thermally at floor level, prioritising stability and cost control.

Building services and performance

A technical assessment by Energylads confirmed that, with the upgraded fabric, the dwelling was capable of achieving an A rating when combined with:

• air-to-water heat pump

• solar PV system

Given the absence of underfloor heating, heat distribution relied on high-output column radiators.

Mechanical ventilation with heat recovery (MVHR), installed by Pro-Air, was a key component of the strategy. While representing an additional capital cost (~€10,000), it significantly reduced moisture risk associated with internal insulation and improved indoor air quality.

 

Construction process

The works were carried out between late 2024 and early 2026 by the client, coordinating a series of approved subcontractors.

The self-build model, while slower, enabled:

• iterative decision-making

• close inspection of existing conditions

• tailored responses to unforeseen issues

As is typical in buildings of this age, a range of historic interventions and poor-quality construction required ongoing adaptation of the design strategy.

 

Outcome

The completed project represents a careful balance between conservation and performance:

• substantial reduction in heat loss

• improved comfort and indoor air quality

• retention of the building’s material character

• achievement of an A-rated energy target (design stage verified)

The interior finish—lime plaster, timber detailing, and crafted joinery—delivers a warm, breathable environment with a contemporary layer of refinement introduced by the client.

 

Key lessons

• Internal insulation in traditional buildings demands a moisture-first approach

• WUFI analysis is essential where risk profiles are complex

• Not all elements need intervention—strategic omission (e.g. floors) can be appropriate

• MVHR is highly beneficial in low-permeability retrofit scenarios

• Self-build projects benefit from structured professional guidance, even in an advisory capacity