Norra 2 was the first phase to subject to the stricter energy requirements and weighting factor 2 for electrical heating. All sites are connected to district heating and have Air Handling Units (AHU) with heat exchangers for air treatment. In this phase, it was possible to credit all locally produced energy. Form factor, proportion of window area, and insulation performance of building envelopes varies. Less favourable conditions could partly be compensated for by technical installations such as solar collectors, solar panels, and wastewater heat exchangers.
All developers have submitted metered values; however, not all requirements were met. The City of Stockholm and developers have continued to discuss causes of deviations from requirements. Subsequently, a strategy has been developed to remedy shortcomings and errors in order to achieve requirements. All developers reported more heat loss than expected, especially for ventilation, hot water circulation losses, and thermal bridges. Other causes that have been identified are problems with meters, system readjustments, and faulty connections that were not detected until warranty inspections. Hot water use in almost all buildings was lower than the standard value. Property electricity has decreased after the first reporting of metered values. The installed wastewater heat exchangers and solar collectors do not achieve the suppliers’ promised performance. Measurement of energy use in garages needs to be reviewed. System tuning and adjustment, as well as measures to address construction and technical installation errors, are ongoing. There are also shortcomings in the handover from project planning to construction work and from construction work to property management. Developers will present the results of this work after the 2021 heating season.
This feedback of experience with learnings from the Norra 2 phase makes an extremely important contribution to improvements in the construction sector. Proactive and transparent collaboration between all parties has created an important knowledge platform.
Adjustments to the monitoring phase have been made according to the National Board of Housing regulations but needs to be improved and developed.
These dialogue meetings have provided important insights and learnings for the construction of energy-efficient buildings throughout the entire construction process – from design and construction to operation and management. Potential exists to improve all parts of the construction process from project planning, energy co-ordination, as-built documentation, to handover to maintenance staff and management. The experiences gained are unique and will contribute to capacity enhancement throughout the construction sector. Updates to recorded values after these measures have been conducted took place during autumn 2020.
Diagram 3.10 Energy performance Norra 2, kWh/m² Atemp per year
- Bonava reported higher heat use, marginally worse solar cell performance, and around 3 kWh/m² lower hot water use than projected, despite the wastewater heat exchanger being un-operational for a period of time. The greater heat requirement is explained by an imbalance in the ventilation system, higher indoor temperatures, alignment deficiencies, and a surcharge for comfort floor heating which is electrically powered and thereby weighted with a factor 2.
- Heba recorded higher heat use due to hot water loss, higher airflow than projected, alignment problems. Several steps have been taken to address these issues, such as the review of AHU performance, ventilation systems, and alignment of heating systems, which has resulted in a reduction in energy use.
- SSM had higher metered heat use than projected. Solar energy metering was substandard and could not be included in the latest review. Hot water use was lower than estimated. Monitoring routines need to be improved.
- Viktor Hanson had higher heat use due to measurement errors, faulty fittings in heating systems, and other areas that impact energy performance of solar collectors and floor heating which were detected during final inspection. These have been adjusted and largely addressed, although work in this area remains to be done.
- Wallenstam dwellings have faults with heating systems and property electricity use was slightly higher than projected. Improvements have been made to monitoring routines. Reporting of faults, shortcomings, and adjustments are continuing and have worked well to date.
- Wallenstam pre-school has high heat use due to its ventilation system not being demand-controlled, resulting in greater air flow, extended periods of operation, and high indoor temperatures. User behaviour has played a key role here. Alignment and remedial actions are ongoing and are expected to show improved results.
- Erik Wallin identified shortcomings in electric batteries used to power apartments’ AHU units and had electrically powered comfort floor heating which is classed as factor 2. The solar collector array failed to fulfil its promised potential and a wrongly installed wastewater heat exchanger did not function. Hot water circulation losses are considerable.
- Skanska has higher heat use due to commissioning problems including metering errors and runtimes.
- Stockholmshem has higher heat use due to commissioning problems including metering errors and adjustments. Wastewater heat exchangers were faulty at the time of the first review and one commercial property lacked meters. Measures to streamline and address flaws in ventilation and heating systems are ongoing. Property electricity use could have been reduced.