CS06 Social semi-detached houses in Auby

Current status: 
Building Owner: 
SIA Habitat
Consulting EuroPHit Partner: 

LaMP - Contact person Simon Camal

Existing treated floor area (usable floor space): 
2 248.00 m²
Original situation: 

These semi-detached and mid terraced houses, 100 m² TFA each, were built in 1978 with standard concrete hollow block walls plus 7 cm interior insulation and 10 cm mineral wool between rafters. The concrete slab on grade is not insulated. Facades are oriented on an East-West axis, with a reduced overall window area. A garage is inserted between two adjacent dwellings. Heating and domestic hot water are supplied by gas boilers. There is limited space for insulating the slab from the inside. Reaching the EnerPHit level without modifying too much the existing solar aperture is quite difficult here. Another challenging task is to find a proper way to include the garages in the thermal envelope without compromising the quality of the airtightness.

Modernisation proposal: 

The owners want to build on their current maintenance scheme an EnerPHit step-by-step retrofit plan. The main steps decided by the owners for the period 2016 - 2018 are:

  • Roof insulation to a U-value of 0,10 W/(m²·K);
  • Airtightness n50 = 1 h-1 and Mechanical Ventilation with 88% effective heat recovery ratio;
  • Replacement of all windows and doors to passive house component quality. Average U-value of components installed of 0.85 W/(m²·K) with an overall positive energy balance in winter;

These steps will be mostly done while keeping tenants in situ.

Following steps will occur later:

  • External insulation of walls with an average U-value < 0.15 W/(m²·K)
  • Implementation of renewable energy sources for domestic hot water: solar thermal on south oriented pitched roofs.
Efficiency improvement: 
PHPP verification sheet before retrofit: 
after retrofit: 
Current situation: 

Detailed planning is currently ongoing for these 24 semi-detached houses. The first retrofit steps will include ceiling airtightness and insulation. A mechanical ventilation unit without heat recovery will be installed in the unheated attic. To get a more compact envelope and increase the useful surface, garages will be converted to additional rooms.The economic assessment has shown that the global annual cost of the EnerPHit refurbishment will be slightly lower than the cost of a minimal maintenance as initially scheduled (3200 €/(a.dwelling) versus 3500 €/(a.dwelling), excluding white goods). This means that an EnerPHit performance level can be attained in 2020 without additional costs. Operational costs for heat and anciliary will be reduced by 80%.

Challenges of the project: 
This building typology with small dwellings and scarce solar aperture is a challenging case for the EnerPHit standard, especially in the North of France where winters are long and cloudy. The heating demand criterion could be fulfilled without having to insulate slabs in the living areas (already moderately insulated) if the external insulation of the wall is continued into the ground until the bottom of the existing foundations. Another challenge here will be to get the approval of tenants as the retrofit plan will modify the use of their house and imply significant energy efficiency works
Connection details and thermal performance of the building (click to view gallery): 
59950 Auby