E2ReBuild Oulu Demonstrator

E2ReBuild was a European collaborative project aimed for industrial-scale energy efficient retrofitting of residential buildings in cold climates. The vision was to change the resource intensive construction sector to include innovative, energy efficient and modern practices, and to create added value to existing buildings. Europe has a large number of buildings built quickly and cost-effectively after World War II. Many of them are in need of substantial renovation. Energy efficiency is poor in many of these buildings, while demand for energy efficiency constantly grows. The E2ReBuild Demonstration Projects utilized results from research on innovative and sustainable renovation solutions. Specifically, the focus was on industrialised manufacturing of facade elements and standardised retrofit measures with high replication potential. Existing structures, such as concrete frames, were mostly left in place. On the other hand, changes were more substantial than usual in renovations. The outcome and lessons-learned of these Demonstrations were used as bottom-up feedback for further research. The Oulu Demonstrator aimed for the building to meet and exceed current standards for new buildings. The Demonstrator was a student apartment building consisting of 8 apartments. The building was originally completed in 1985. It had been built using the so-called BES, a Finnish industrialized system using prefabricated concrete elements, developed in the 1970's for residential buildings. The apartment interiors had become outdated and a complete renovation was needed. The Demonstrator aimed to meet the Passive House energy level. Targets for energy efficiency, insulation and airtightness were set based on the Finnish Passive House national recommendations. The aim was to reduce the building’s energy use to 30kWh/m2/y, encompassing heating, ventilation and hot water. A key objective was to apply modern industrialized wood construction techniques to retrofit existing buildings, using the TES (Timber-based Element System) Energy Facade. TES are large-scale, prefabricated, timber frame elements. The Oulu Demonstrator was a possibility to further develop the TES and monitor the results. Life cycle impacts were also considered, aiming for robust long-term solutions. Another objective for the Oulu Demonstrator was to change the layout of the apartments to something more suitable for student families. Thus property development with a strong social aspect was also involved. The retrofit included a renewal of the facade with the TES elements and a comprehensive renovation of indoor spaces. The ground floor slab was replaced with a well-insulated in-situ slab and new ground fill to reduce moisture risks. Detected air leaks in the existing concrete shell were grouted. The outer concrete layer of the existing facade elements, old insulation, doors and windows were removed. The inner concrete layer of the old elements was covered with TES elements, which contained a high degree of insulation - necessary in the very northern location. A total of 2000m2 TES elements were assembled on-site. The building received a new roof with added insulation. Old balconies were replaced. Shade to the south side was provided to reduce risk of overheating in summer. The building volume was simplified to reduce thermal transmission. Building services were entirely replaced: district heating renewed, water saving fixtures added, heat recovery ventilation installed and additional HVAC ducts fitted under the roof. Several different prefabricated structural materials were used, from timber-based facade elements to precast concrete and steel balconies, and modern doors and windows. The facade was clad with corrugated fibre cement cladding, usually used on roofs. This solution is robust, low-maintenance and protects the external thermal insulation from weather. Site drainage and ground frost insulation were improved. The interior was modified to house student families. This included adding saunas to the apartments and developing the layout of the apartments. Building automation was installed to track energy performance, indoor air quality, outdoor conditions, and building physics. The latter was given extra attention, as the performance of the prefabricated facade needed to be verified. Airtightness tests and thermal surveys were done, both prior to construction and in winter prior to completion. Experimental radar survey was tested to investigate concrete structures. Aalto University interviewed the tenants before and after the retrofit, inspected off-site production, documented the project progress, assisted with quality control, and collected a year’s worth of monitoring data (completed in March 2014). Construction was started in August 2012 and initially completed in February 2013. However, further air leaks were detected at the ground slab perimeter and ground floor apartments were vacated for correctional work during December 2013–March 2014. Success Indicators Targets for energy retrofitted houses with passive house components (EnerPHit) were achieved. The retrofit was one of eight nominees for the 2013 Wood Prize in Finland (Puupalkinto). Novelty The Demonstration was a broad-scale refurbishment. The focus was not solely on energy efficiency, but also included efficient retrofitting, collaboration, life cycle impacts, indoor air quality, tenant energy usage, building physics monitoring, combination of old and new components, and cost-effectiveness assessment. New ties and collaborations were created between universities and industry partners. The know-how of several parties was developed (the contractor, architects and planners, researchers and product development). Sustainability Impacts Occupant comfort levels were improved. The actual use of heat, electricity and warm water were analysed. Space heating demand and purchased district heat were both reduced by ~60%. Air tightness and the U-values (thermal transmittance) of exterior structures were all reduced significantly. However, the property’s electricity use was only reduced by about 15%, due to the new efficient ventilation using electricity. When well done, a similar refurbishment can reduce energy demand, enhance indoor comfort and rise property value of an existing building for several decades. Utilising existing structures and combining them with timber based components decreases the CO2 footprint of the refurbishment. Cost-effectiveness Analysis revealed that the costs for the interior renovation and the balconies were half of the total refurbishment costs. The facade renovation itself represented 16% of the costs - half of this was due to facade cladding and separately assembled windows and doors. Design, survey, contract and site costs were another 16%. This could have been proportionally smaller, if the refurbishment would have been done to all five buildings on the property. Improved design coordination and cost-effective off-site prefabrication can reduce on-site delays. The rest, 19 %, consisted of roof, ground slab and building services replacement as well as monitoring. The results and lessons-learned have been used as teaching material, in further research and development, and in scientific publications and dissemination of research results. The project supported product development. Other E2ReBuild Demonstrations utilising the TES system were Grüntenstraße in Augsburg, Germany; Sendling in Munich, Germany; Roosendaal in the Netherlands; and Thamesmead in UK. After the E2ReBuild-project ended, elements from the same local producer (Suomen Rakennustuote) have been used in new buildings. Similar TES elements have also been used in later projects in Germany, the Netherlands and Norway. Challenges and potential for further development The following topics or phases were identified: • Exact measurements of existing buildings are important for design and prefabrication • Demolition of old structures requires care and expertise • Air tightness and indoor air quality when combining old and new structures • Moisture safety in assemblies and installations • Collect, analyse and report monitoring data efficiently with robust online interfaces • Monitor building performance for long enough to get results from normal living conditions • Pay attention to communication with tenants and minimise disturbance from construction work • Efficient and smooth implementation of retrofit projects (e.g. difference of interests and motivators of different parties) Contact person(s) for more information: Simon Le Roux, Simon.LeRoux@ym.fi