SITE – Small mature garden with many trees , which  required a detailed tree survey to determine  the location , height and spread of each tree , this data had to be inputted into PHPP software to ascertain the impact on the design in terms of solar  gain /shading .

BRIEF-  5 Bed  two storey house  to Certified Passive Standard


Site analysis  ( trees) and sun path determined   the orientation of the house  , the primary aim being to keep north facing windows to a minimum, and locating all the main living spaces to south west to enjoy the optimum benefits of solar gain. A large canopy roof was used to act as a ‘brise soleil’ to counteract overheating but also to provide a covered patio area accessed directly off the kitchen / living spaces .

The design solution is two linear shallow plan blocks one two storey and one single storey , staggered  to create a front entrance between blocks , with car port and garage , porch entrance hall ,kitchen/dining space , playroom , bootroom , cloakroom located at ground level of single storey block ,living room ,  guest bedroom with en-suite  , utility room  and services room are located on  ground floor  of two storey block . The first floor contains master en suite , 3 bedrooms and family bathroom .

The two blocks have monopitched roofs with slate finish on the two storey block & sedum ‘living roof’ on the single storey block . Sedum is a very sustainable  roof finish  as it retards rainwater runoff but also acts as a habitat for birds etc . In addition , it changes colour with the seasons giving a  different appearance to the house at different  times of the year.

Material palette was completed with white self finished  external wall insulation system , and timber cladding  , aluclad triple glazed windows .


The following performance  targets are required in order to meet the PH Design Criteria;-

  • Heating Energy Demand -QH = < 15kWh/(m2a)
  • Primary Energy Demand- QP= <120kWh/(m2a) (Includes all necessary energy applications  for heating , cooling , domestic hot water, auxillary electricity, lighting & other electricity uses).
  • Building Airtightness – n50<0.6/h
  • Excess Temperature Frequency ( overheating ) – <10% /year  ( >25 Deg C)
  • Heat Protection –  U<0.15W/m2K (floors , walls , roof )
  • Windows – Uw-<0.8W/m2K , Ug- <0.8W/m2K ( g value 50-55%)
  • Linear Thermal Bridging – Linear Thermal Bridge Free
  • Ventilation –  with min 75% heat recovery  +Electricity demand Max 0.45w/h/m3

All relevant data is inputted into a spreadsheet  ( PHPP ) which is used as a design tool  that has approximately 600-700  data inputs in order to calculate the Energy Balance and  verify that the energy performance targets are achieved . The design of the house may need to be tweaked & data inputs revised  to achieve the required target figures .

Any design changes made after design sign off (ie window size or location)  may  result in non compliance  as the energy balance is  so finely tuned


The verified result for  Primary  Energy Demand  is the critical  figure for compliance with current Building Regulations  which at present is  45kWh/m2a nZeb ( Nearly  Zero Energy Building )  or A2 BER .  Certified Passive Haus standard is  15kWh/m2a  A1 BER which surpasses the current Building Regulation standard.

ENERPHit  ( Certified Retrofit Standard )

For Energy Retrofit upgrade of existing buildings  there is a slightly lesser Certified Passive Haus Retrofit standard  termed ENERPHit .

The lesser performance target figure  is based on not being able to  create thermal bridge free design of floor/ wall  junction at ground floor of existing buildings.


The following performance  targets are required in order to meet the PH Enerphit Retrofit  design criteria;-

Heating Energy Demand -QH = < 25kWh/(m2a)

Primary Energy Demand- QP= <132kWh/(m2a) + (QH  < 15kWh/(m2a) * 1.2)

Includes all necessary energy applications  for heating , cooling , domestic hot water , auxillary electricity , lighting  & other  electricity uses.