Case Study: nZEC - New construction of 10 dwellings in the residence Le Hameau de l’Esperance, La Brède, France
Name of organisation: Mésolia Habitat
Stage of development: completed
Year of finalization: 2010
Type of project: construction
Area: suburban
Scale: group of buildings
Type of building: group of terraced houses
Number of units/dwellings: 10
Tenure: social rental
Street: Avenue Charles de Gaulle
Postcode: 33650
City: La Brède
Region/ County: Aquitaine
Country: France
Last Update: 17.04.2015
Short Description
The Hameau de l'Espérance (Hamlet of Hope) consists in 10 semi-detached houses with private gardens and garages, build at the heart of a concerted development zone (ZAC - Zone d'Aménagement Concerté) with the aim to combine sustainable development, comfort and reduce energy costs for tenants.
Key Elements
Thermal Insulation
The external walls are composed of bricks with an external insulation. The separation walls between houses are composed of solid concrete blocks. The technique used for the structure is a parallel chord truss. For the ceilings under attic, the insulating material used is cellulose. Thanks to the high heat inertia, the dwellings benefit from a good summer comfort.
Work with Residents
A user booklet was distributed to the inhabitants.
Ventilation
A mechanical ventilation system with heat recovery was installed. This choice resulted from the necessity to comply with the levels of consumptions required to obtain the BBC Effinergie label. Moreover, this mechanical ventilation with heat recovery enables, through a high level of ventilation in summer, a cooling of the rooms.
Heating and Hot Water
The heating is ensured by individual gas boilers (12kW), these boilers also ensure the difference for the production of domestic hot water, which is uppermost produced thanks to solar thermal panels.
Water Saving
Rainwater is collected and water savings equipment was installed in the dwellings. Moreover, some advice in favour of electrical savings in the common parts of the buildings were given and the use of healthy material was favoured.
Partnership Working
Throughout the conception phase, architects were very involved in the project and worked closely with the energy engineering consultant company.
Funding
Costs | |
Statutory approvals | Rent-charge: 499€ without taxes / m² living area |
Design |
Intellectual services : 144€ without taxes / m² living area |
Construction overall | 1104€ without taxes /m² living area |
Low/zero carbon technologies | Extra investment cost of 3500€/dwelling for the solar thermal panels |
VAT | 5.5% |
Running costs | ENERGY EXPENSES Estimated and real expenses all taxes included per year and per dwelling Estimated energy expenses Maintenance (Heating+Ventilation+DHW): 168€ Consumption (Heating+DHW) : 144€ Subscription : 60€ Real energy expenses Maintenance (Heating+Ventilation+DHW): 206€ Consumption (Heating+DHW) : 240€ Subscription (including gas meters, electricity and DHW) : 180€
RENTS AND REAL EXPENSES (/m² living area.month) Rent + garage: 5.15 + 0.28 Energy subscritption + Energy maintenance : 0.37 Energy consumption: 0.23 Other expenses : 0.16 Total : 6.20 |
Maintenance – repairs and replacement | Extra maintenance costs related to solar energy and ventilation with heat recovery : 90€/dwelling for solar DHW |
Public financial assistance (loan/annuity/grant) | State + Regional + Departmental council fundings: 14% of the global cost Laureate of the contest Aliénor “Construction of low energy buildings” which implied a technical and financial support in return of a control of the performances. |
Main Results
- This project was one of the first BBC certified operation. As a consequence, the construction site was a pilot in terms of companies and craftsmen training related to energy performances.
- As a pilot, some of the technical solutions selected proved not to be adapted to the context and the global cost revealed to be 13% higher than regular operations. In the new projects, these solutions are now avoided. This is the case for example of the mechanical ventilation with heat recovery. Due to the costs (investment and maintenance) and the complexity of this system, this solution revealed not to be conclusive.
- In terms of performances expected, at the end of the first year, a gap appeared between the targeted consumptions and the real consumptions. As a consequence, the follow-up of these consumptions is very important to be able to react. Indeed, during that first year, due to the good insulation and the important solar inputs, the temperature in the dwellings appeared to be too high. A good acoustic quality was obtained thanks to the structure and the walls composition.
Lessons learned
- Among the weak points of the project, some of the technical solutions appeared not to be optimal, for example the mechanical ventilation (high costs, use and maintenance complexity) but also the solar thermal energy. As a matter of fact, the solar production (1600kWh/yr.dwelling) equals a gas consumption of 85€/ yr.dwelling.
- Considering the extra investment cost of 3500€/dwelling and the extra maintenance cost of 90€ (which does not include the cost of cleaning of the solar panels), the financial benefit is not reached. One of the reasons for these choices could be that the maintenance feedbacks were not considered during the conception phase. Some other solutions were studied in the pre-studies but were not selected (for example the ground-coupled heat exchanger).
- Among the strong points of the project, the joint work between the architects and the energy consultants enabled to reach a good level of performance. Even if all the solutions did not prove to be optimal, most of the technical choices were adapted to the context and took part in the global quality of the buildings.
Additional Information
Ms Carine Puyol
USH - The French Federation of Social Housing Providers
E-mail: carine.puyol@union-habitat.org
Web: www.union-habitat.org