Passivhaus Affiliate

Lime Tree Passivhaus nears completion

Lime Tree Passivhaus, a new build private dwelling located in Swaffham, Norfolk is due for completion next month.

The project team has a wealth of Passivhaus experience including 2014 UK Passivhaus Award winning practice Parsons + Whittley and ventilation expert Alan Clarke, but is a first Passivhaus build for contractors Grocott and Murfit.

The layout of the dwelling has been led by, and reflects the presence of, a dominant Lime tree on site. The presence of a deciduous tree can enhance Passivhaus design by providing shading in summer to avoid overheating, whilst allowing winter sun to penetrate and provide passive solar gain.

Having established the spread and root protection zones of the tree, the dwelling is designed as a annulus segment centred on the tree, spaced outwards so as to avoid the root protection area. The circular nature is then emphasised by three concentric segmental sections of outer brickwork, each shielding the main dwelling, associated smaller rooms and finally the rear wing and covered areas. These later two are roofed by a GRP flat roof to reduce the mass of the dwelling. The main dwelling is roofed by a single pitched zinc sheet roof falling towards the tree.

This shape presents a south facing gable which has been fully glazed both for the passive solar gain and also to provide views into and out of the garden. Finally the roof has been extended over this area to provide further solar shading as protection against overheating.

Smaller window openings on the north and eastern sides provide additional light whilst minimising heat loss.

Materials proposed consist of brickwork outer walls, although differing red and buff colours to emphasise the openings, with vertical timber cladding to the other faces which both facilitate the curved cladding and reflect the wooded nature of the site. The timber is generally used at the lower levels to facilitate maintenance, whereas the brickwork is used in the more inaccessible locations as a maintenance free material.


  • Wall: Brick and aircrete blockwork with 300mm cavity filled with EPS platinum bead insulation (U-value = 0.098w/m²k)
    Larch vertical timber cladding and two layers of aircrete blockwork with 300mm cavity filled with EPS platinum bead insulation (U-value = 0.096w/m²k)
  • Roof: Zinc seamed roof finish with 356mm I-beam fully filled with EPS platinum bead insulation with OSB and plasterboard layers (U-value = 0.087w/m²k)
  • Floor: Oak timber floor finish with 200mm PIR insulation (U-value = 1.000w/m²k)
  • Windows and doors: EcoHaus Internorm Home Pure HF310 triple glazed timber/ aluminium composite (Window u-value = 0.72w/m²k, door u-value = 0.90w/m²k, glazing g-value = 0.60w/m²k)

Predicted performance data:

  • Thermal energy demand: 15kWh/m2.yr
  • Energy load: 12W/m2
  • Primary energy demand: 98kWh/m2.yr

Project team:

  • Architect: Parsons + Whittley
  • Consultant: Alan Clarke
  • Contractor: Grocott & Murfit
  • Structural engineer: Plandescil Consulting Engineers
  • Certifier: MEAD

Further information:

Contractors Grocott & Murfit are providing regular photo updates of the project progress on their website.


All image credits: Grocott & Murfit.

13th July 2015

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