Lime Tree Lodge

Construction of a single two bed mono pitched bungalow built to Passivhaus standards in Swaffham, Norfolk

Construction on the bungalow took 28 weeks to compete with the inner aircrete shell going up in three weeks.

Aircrete products were selected for this project due to the Aircretes high thermal performance properties which helps meet Passivhaus standards. Passivhaus is achieved by the application of high levels of insulation, avoidance of thermal bridging within the structure, and low levels of air leakage, all of which are qualities addressed with the use of Aircrete blocks.

The contractors offered a design and build package utilising a local architect. This was the first Passivhaus project for the team with Aircrete specified for the internal leaf. Having looked at other alternatives, to meet the stringent Passivhaus standards, the contractors opted for Aircrete due to the delivery time, speed of construction, stability, thermal mass and the contractors experience with Aircrete blocks. 

Faced with both brick and timber the bungalow has an external U-value of 0.096 W/m2K for the timber faced walls and 0.098W/m2K for the brick faced walls. Aircretes was a key contributor to achieving these results with a thermal conductivity of 0.15W/m2K 

Wall construction: 140mm and 100mm Aircrete Block Standard Grade 3.6N with a thermal conductivity of 0.15W/m2K used in an effort to reach Passivhaus standards. Brick faced walls with a U-value of 0.098W/m2K and timber faced walls with a 0.096 W/m2K 300mm cavity fully filled with EPS insulation.

Architects comments: “Compared to a timber frame solution Aircrete products allowed for a faster build process, enhanced stability and better thermal mass qualities allowing us to reach Passivhaus standards. This was the preferred building material for the contractors too due to previous experience and now desire to again build using Aircrete.”

APA comments: “The developments energy efficiency rating and environmental assessment was a primary concern.  By using Aircrete blocks with a conductivity value of 0.15W/m2K they were able to achieve the Passivhaus standards they were aiming for. Aircrete has the advantage of having an inherent thermal efficiency which helps achieve low fabric U-values. Further benefit is gained with reduced heat loss from thermal bridges and hence reduced energy demand to provide heat in winter”


  • Easily meets or exceed Part L and Part E of the Building Regulations
  • Simplifies the construction process
  • Aircrete products use up to 80% recycled material
  • Achieves A+ rating in the BRE Green guide


  • Blockwork is highly adaptable, easily allowing for any last-minute design changes
  • Aircrete achieves an air permeability of 0.12m³/hr/m²
  • Aircrete has excellent fire resistance with a Class 0 rating for surface spread of flame


  • Internal and external leaf in cavity wall construction
  • Solid walls
  • Separating / party walls
  • Flanking walls
  • Partitions
  • Multi-storey
  • Foundations

Aircrete is an excellent all round commercial and industrial building material. Used in partitions and external walls (both solid wall and cavity wall construction), fire walls and as infill to steel and concrete framed buildings it provides durability, fire resistance and superb thermal and acoustic insulation.

Aircrete has exceptional sustainability credentials: not only does it provide excellent thermal and acoustic insulation and contributes to airtightness but, being manufactured from up to 80% recycled materials, it is sustainable both in manufacture and in use.