Ton Pentre Terraced House

The Building

Building post-intervention

The property is a typical late Victorian two-up, two-down mid-terrace in social ownership. It had previously been extensively altered, some efficiency upgrades installed, and substantial repairs were required prior to retrofit.

The Solution

Solution pre-intervention

Solution post-intervention

What is the Solution?

The insulation solution for Ton Pentre was innovative, focusing on moisture control and thermal performance. External render and aerogel lime plaster IWI system were used. WUFI modelling confirmed low moisture risk. Target U-value was 0.70W/m²K, but achieved 0.53W/m²K, a 24% improvement. Original U-value c. 1.7, so overall an improvement of c. 70%. Various application methods were explored, including manual 'harling' and industrial render pumps. Contractor feedback highlighted the importance of product knowledge. Overall, the approach balances efficiency and preservation, laying groundwork for potential future deployments.

Why Does it work?

The solution for insulating Ton Pentre's solid walls was chosen to address moisture control and enhance thermal performance. It integrates external render and aerogel lime plaster IWI, validated by WUFI modelling. Achieving a U-value of 0.53W/m²K, surpassing the targeted 0.70W/m²K, demonstrates technical effectiveness. Application methods like 'harling' and hand plastering ensure compatibility with the building's heritage context, while contractor expertise ensures successful implementation. External airlime render designed to keep wall dry. Limewash finish to act as sacrificial layer for protection of render.

PROS

Good thermal, comfort, and air-tightness performance without sacrificing historic details nor changing the underlying technical performance of the building. External airlime render designed to keep wall dry. Limewash finish to act as sacrificial layer for protection of render.

CONS

Aerogel aggregate plaster more expensive than many plasters. Need for breathable paint on inside and limewash on external. This needs to be maintained / stipulated by social landlord rather than tenants, so an element of control required over this.

Insulation material

Aerogel Lime Plaster

Insulation thickness

Thermal conductivity

0.02

Health issue

Care required as aerogel plaster is very fine and so breathing apparatus is essential to wear. Lime is caustic and so hand protection required for all applications.

Technical drawings

Wall015_Technical_Drawings_1.png

Additional documentation

Ton-Pentre-Solid-Wall-Insulation-Case-Study-2023.pdf

Installation Method

IWI plaster trowelled on, External render pumped and harled on.

Moisture Management and Technical Compatibility

External render designed as an airlime with porous limestone aggregate with limewash finish should act as an osmotic layer to draw moisture out of wall and keep it dry. Internal finish was Auro natural paint that is moisture open, but scrubbable.

Airtightness

Airtight due to plaster / render finish