Recently, there has been an increase in apartments with a large number of inhabitants, i.e., high residential density. This is partly due to a housing shortage in general but also increased migration, particularly in suburbs of major cities. This paper specifies issues that might be caused by high residential density by investigating the technical parameters influenced in Swedish apartments that are likely to have high residential density. Interviews with 11 employees at housing companies were conducted to identify issues that might be caused by high residential density. Furthermore, simulations were conducted based on extreme conditions described in the interviews to determine the impact on the energy use, indoor environmental quality, and moisture loads. In addition, the impact of measures to mitigate the identified issues was determined. Measures such as demand-controlled ventilation, increase of a constant ventilation rate, and moisture buffering are shown to reduce the risk for thermal discomfort, mold growth, and diminished indoor air quality; while still achieving a lower energy use than in a normally occupied apartment. The results of this study can be used by authorities to formulate incentives and/or recommendations for housing owners to implement measures to ensure good indoor environmental quality for all, irrespective of residential density conditions.

Cleaning coils can be an efficient way to reduce the need for reparations and maintain the functionality of a ventilation system. This study builds upon existing knowledge concerning the contamination of heat exchangers. Through field measurements on coils and heat-recovery units, a laboratory experiment on a coil, and a generic calculation example, this study determines the impact of sustained contamination on heat-recovery units with regards to energy use. Field measurements made before and after cleaning of heat exchangers show an average increase in the pressure drop by 12% and decrease in the thermal exchange efficiency by 8.1% due to mass deposited on the surface of the heat exchangers. Results from a laboratory test show a correlation between the mass deposited on a coil and (1) the increase in pressure drop over the coil, as well as (2) a diminishing heat exchange. Accumulating contamination on heat-recovery units in residential and commercial buildings (over time) is then linked to increasing pressure drop and diminishing thermal efficiency. With models based on these links, energy loss over time is calculated based on a generic calculation example in a realistic scenario. Practical application: The results from this study emphasize the need for maintenance of buildings with ventilation systems with coils, but more so those with heat-recovery units. The presented field measurements and laboratory study correlate energy loss with sustained accumulation of contaminants on coils and heat-recovery units. These results should serve as a recommendation to property owners considering maintenance of such units in their buildings.

From 1950 until 1975 approximately 1.3 million apartments were built in Sweden. Now, a considerable part of these are in need of renovation. This paper is part of an evaluation of a new DCV system developed especially for the renovation of these houses. The DCV automatically regulates the air change rate for each dwelling based on measurements of the indoor air. One of the measured parameters is the moisture supply. Simply put, the ventilation rate increases when the measured moisture supply exceeds the set point based on a PI-controller. In this paper, simulations have been carried out to determine an appropriate set point for the moisture supply for avoidance of moisture damage on biological building materials. A worst case scenario has been considered – and the general maximal set point is recommended to be 3g/m3

A novel DCV-system controls the air-change rate for each apartment in multifamily buildings based on two indoor air parameters: 1) the moisture load (supply), and 2) volatile organic compounds. With a central fan, but decentralized control boxes placed outside each apartment, the system controls the air-change rate for each apartment. This paper’s main aim is to determine the potential of this DCV-system, through a case study, to: 1) achieve good IAQ, 2) handle the moisture loads appropriately, and 3) achieve good energy efficiency in multifamily buildings. Furthermore, the paper aims to assess the possibility to achieve good IAQ by validating the DCV-system’s VOC-controls through measurements of CO₂ in apartments. Field measurements show that the system responds appropriately to apartment-specific loads, and that acceptable emission and moisture loads are achieved in most apartments in the case study. The impact that the system has on the energy use was assessed through calculations based on the field measurements. The calculations show that the DCV-system saves energy used for heating the supply-air by 86% in comparison to a mechanically balanced ventilation system without heat recovery, and 22% in comparison to the same system but with heat recovery.