In this research, an existing building calibrated simulation model from 1981 was built based on measured energy and indoor temperature data. The model was used to study the central control's energy-saving potential. With parametric simulations, DHW circulation internal heat gain and ventilation airflow rate was determined as 85% and 0.29 l/s/m², respectively. DHW circulation heat loss has been found almost as high as DHW use. Dropping the heating curve from 70/40 °C to 65/35 °C resulted in a saving of 0.6 kWh/m²a (0.8% of space heating energy) on the cost of thermal comfort as yearly hours of the mean air temperature below 21 °C rose from 2.7% to 9.0%. It was necessary to reduce the heating curve to 55/25 °C in a hypothetical scenario with fully open thermostats, indicating heat redistribution from warmer to colder rooms, leading to higher heating energy. The findings indicate no energy saving potential due to compromising thermal comfort even by 5 °C heating curve reduction. It was revealed that the building average indoor temperature is not a factor to estimate energy-saving potential because of too low temperature in the coldest apartments.
Building energy efficiency, construction cost, life cycle cost, and carbon emission are the best interests of users, owners and different vendors. This study assessed the energy performance (EP) related investment and operational energy cost of Kouvola housing fair NZEB. Data from 12 new detached houses were collected, which fulfilled the energy certificate class of B according to the Finnish nearly zero energy building (NZEB) regulation. Besides, emission from building materials, construction and energy use during 50 years of one model building were estimated, aiming to compare the life cycle emission from wooden building, insulated concrete building, blockhouse and log house. The results showed that the total construction cost was independent to EP-value and even had a slightly negative correlation to the EP-value. The average EP-value of 12 buildings was slightly higher than that of buildings in Tampere housing fair 2012, which showed no improvement of nearly zero energy building (NZEB) guidelines since 2012. Energy performance related cost dependency in specific cost categories was shown so that EP-value improvement by 40 units increased less than 2% of construction cost. Electricity had a significant contribution to CO2 emission while local district heating was based on renewables. Material emissions contribution was 32-48% of total emissions, and wooden buildings showed lower carbon footprint compared to other building structures.
Space Heating (SH) substations in District Heating-based (DH) systems are typically dimensioned at the design outdoor temperature without accounting for internal and solar heat gains. In residential buildings, the total required DH power typically also includes the need for Domestic Hot Water (DHW). This practice results in oversized substations and high DH design flow rates, which, due to heat gains and building thermal mass utilization in building operation, rarely, if ever, occur. Modern buildings maintain the desired indoor temperature with lower heating power by controlling the SH supply temperature with an outdoor-air-dependent heating curve and heating water flow with room unit thermostats. Applying a dynamic heating control algorithm can be considered one option to reduce the required DH power and optimize the DH network. Another possibility to decrease the needed power is controlling the DH flow by prioritizing DHW production and limiting the DH flow for SH. This study proposed a novel sizing method for the DH substation that quantifies the effects of dynamic control and flow limiters. Building models with detailed hydronic plants, accounting for internal heat gains, and using conventional and dynamic heating controls were developed in the IDA Indoor Climate and Energy simulation tool. The results show a potential DH side power reduction of up to 25%.
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