Case Study: nZEC - Energy refurbishment of 40 dwellings and new construction of 221 dwellings in Square Maïmat, Muret, France

Short Description

This large construction project that began in 2010 and will end in 2015 entails the following steps:

Global project:
- Demolition of a shopping center and 173 dwellings
- Construction of 221 dwelllings
- Retrofitting of 40 dwellings

South part:
Construction of 6 buildings composed of 148 dwellings: 66 dwellings in the buildings A, B and C and 82 dwellings in the buildings D, E and F

First part: Buildings A, B and C : 66 dwellings Completed in October 2012
Second part: Buildings E : 26 dwellings Completed in December 2013
Third part: Buildings D, F : 56 dwellings Completed in June 2014

Retrofitting of 40 dwellings in the residence “Monès”.
Expansion of the area dedicated to shops: from 300m² to 1720m² of commercial and associative premises and use of the ground floors of the buildings of the south part.
Creation of a square, a public park and an underground car park.

North part:
Construction of 3 buildings composed of 73 dwellings – In the planning stage

Total SHON (close to the Floor Area, including walls): 13 000m²

Key Elements

Work with Residents

Several consultation meetings were organized with tenants. An individualized follow-up of the tenants was also ensured as well as an empowerment of the proximity teams.

Moreover, the tenants can follow their energy consumptions on the web thanks to a web portal developed by a consulting firm. Regular participatory actions are organized by this firm with tenants on energy topics and good consumption practices. Lastly, a low consumption competition was organized.

Certification

BBC-Effinergie - certificate obtained for consumptions of primary energy lower than 50kWh/m².year for heating, adjusted according to the climatic conditions and altitude.

Qualitel by Cerqual - this certificate is related to the compliance with some commitments:

• Energy performances
• Water and Electricity savings
• Environmental management of the project
• Cleaned building site
• Choice of materials
  
  
  

Thermal Insulation

An innovative constructive principle is used, called Duomur. This constructive principle consists in two reinforced concrete panels connected together by composite connectors and including an insulating material.

These prefabricated panels are filled in with the insulating material once on-site. The benefits are the ones of an external insulation, an easy implementation but also the abolition of thermal bridges thanks to the use of self-supporting balconies.

Air Tightness

It is paid attention to the airtightness thanks to the use of concrete, the selection of performing windows and the use of airtight electric box.

Funding

Ventilation

A mechanical ventilation including water adjustable air vents is used.

Heating and Hot Water

Heating is ensured by individual condensing boilers. Radiators with thermostatic valves are installed in the dwellings.

Solar Thermal

Solar panels for the production of electricity are installed on the roof. Twelve fields of 3 polycrystalline silicon units (245 Watt peak each) are installed, which makes a total of 8820 watt peak for a surface of 60m². The profits are subtracted from the collective expenses.

Water Saving

Rainwater is collected. Wastewater is recycled thanks to sewage processing installations. Water saving equipment are used such as water saving flushes toilet.

Environmental Design

In terms of landscape planning, the terrain which was barren was made fertile on a depth of one meter. The management of water on-site was carefully addressed as well as the reuse of materials on-site (such as concrete and old trees).

Main Results

Construction:

• Before: 151 kWh primary energy/m².yr
• After: 29 to 33 kWh primary energy/m².yr

Retrofitting:

• Before: 182 kWh primary energy/m².yr
• After: 95 kWh primary energy/m².yr

A monthly monitoring of the gas, electricity and water consumptions was carried out during the first 7 months. This monitoring enabled to compare the consumptions with the expected consumptions and to take the corrective actions that were needed (correct use of the thermostatic valve by the tenants, change of the defective sensors). These first results show important savings.

Among the 64 dwellings, 30 dwellings reach the low consumption level. 34 dwellings consume more than expected. For these dwellings, several reasons can explain the situation: overconsumption of DHW in case of overcrowding, overconsumption of heating in case of inadequate use of systems, rebound effect due to the increase of comfort.

Lessons learned

The strong points of the project are the high energy performance, the optimization of volumes and the natural lighting.

Among the weak points, the choice of the thermostat should be oriented towards more performing systems (proportional action instead of bang-bang controller). It is also important to pay attention to the user-friendliness of the systems and to the support of the tenants.

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