Westcott House

Victorian country house renovated using Passivhaus principles

Domestic Passivhaus Renovation Dartmoor
Restoration and refurbishment of a large house on the moors to EnerPHit standard

A holistic passive design strategy allows the existing property to be upgraded to a level of energy efficiency such that a conventional heating system will only be required in times of extreme winter conditions. At the same time, it will avoid overheating in summer and aims to have minimal environmental impact.

Sustainable and Environmental Design Strategy:


  • Thermal mass: provided in the load bearing ground floor construction using solid internal walls and floor slabs. Thermal mass reduces internal temperature fluctuations and helps reduce energy use.
  • Super Insulated Building Envelope: masonry walls are externally insulated and rendered to achieve high insulation levels and a U-value of no greater than 0.15W/m2K. An insulated slated roof construction and insulated floor construction achieve U-values of no greater than 0.10W/m2K. All windows and doors are high-performance, triple glazed timber units achieving a minimum U-value of 0.7W/m2K. Combined, these high insulation values minimise heat loss through the building fabric and significantly reduce energy use.
  • Minimal thermal bridging: ensuring continuity of the insulation around the building through careful detailing reduces heat loss and also prevents mould growth by eliminating cold spots.
  • Mechanical ventilation with high efficiency heat recovery: minimising ventilation heat losses through controlled ventilation, ensuring better indoor air quality and reduced heating requirements by retaining energy from exhaust air.
  • High levels of airtightness: draught-proofing and sealing all parts of the construction beyond best practice levels to achieve 1.5 air changes per hour (at 50Pa), further reducing heat loss and therefore reducing energy use.
  • Daylight design: is optimised where possible to reduce reliance on artificial light and utilise solar gain, which supplements internal heating levels and again reduces energy use.
  • Low water use strategies: using rain water harvesting, flow regulators, low flush WCs, aerated taps and low-water-use showers significantly reduces mains water use and costs.
  • Low carbon technologies and on-site renewables: solar hot water panels provide energy-efficient hot water. This technology is classified as low-carbon technology and will continue to reduce the building’s overall carbon footprint by at least 15%.
  • Rainwater collection: these systems recycle rainwater for garden usage and flushing toilets.
  • Efficient appliances: energy efficient lighting and controls further reduce energy use.


Material Selection and Healthy Buildings:


  • Natural / recycled materials where practical.
  • Organic paints, waxes and stains throughout.
  • Specification of timber from sustainably managed woodlands (e.g. FSC certified).
  • Reduction of the use of composite timber panel products.
  • Avoiding the use of PVC by careful product selection (e.g. LSF electrical cabling; clay underground pipe-work; ABS water pipes; timber fascias, soffits and bargeboards; timber windows and doors).
  • Reduced use of heavy metals (e.g. Stainless steel or zinc flashing instead of lead).
  • Electrical wiring in bedrooms is radial to lessen the impact of electromagnetic fields (EMFs).
  • Use of sustainably sourced materials to ISO14001.
  • Use of materials with low embodied energy, where appropriate.
  • Locally sourced materials, wherever possible.
  • Prevention of dust-mite infestation by specification of easily cleanable surfaces.