English

To ensure adequate indoor air quality, ventilation is necessary in new constructions as well as in modernized existing buildings. In order to minimize energy losses, ventilation systems with integrated heat recovery should be used. Particularly in building refurbishment, ventilation systems need to be designed as compact as possible, to allow a subsequent integration in the existing building stock. Ventilation systems in which one component is responsible for ventilation and simultaneously for heat recovery are well suited for this application area.

This research investigates the significance of the moisture buffering and latent heat capacities in exposed cross-laminated timber (CLT) walls with the respect to indoor climate and energy consumption. Hygroscopic materials have the ability to accumulate and release moisture due to change in the surrounding humidity. The moisture buffer capacity is regarded as this ability to moderate, or buffer, the indoor humidity variations. Latent heat refers to the heat of sorption due to the phase change from vapour to bound water in the material and the other way around.

Building integrated renewable energy sources e.g. photovoltaic system is one of the promised solution for improving energy efficiency in building. However such kind of the system is restrained by irregular power supplied and necessity to convert current from direct to altering form. Therefore, very often the electrical energy generated by photovoltaic system cannot be effectively utilised to supply building devices, e.g. components of HVAC or lighting system.

The paper presents optimization model of the chilled water based data center cooling system. The optimization procedure includes system technological and mathematical model, limiting conditions and optimization criterion, which in this case is annual power consumption minimum. The cooling system model is defined by constant parameters and decision variables and consists of aircooled chiller, independent external freecooling heat exchanger (drycooler), computer room air handling unit (CRAH) and constant flow chilled water system with circulation pump.

Airtightness of buildings is necessary to obtain healthy, sustainable and energy efficient buildings. Measuring the airtightness of a building has become more common lately, much due to the higher energy use in leaky buildings. The airtightness of a building can for example be measured in order to attain a certification, or on demand from a developer. In some studies, there have been large seasonal variations in airtightness. In most cases, the buildings are more leaky in wintertime, but there are also some investigations that show the opposite.

Numerous studies have investigated the application of multi-zone demand-controlled ventilation for office buildings. However, although Swedish regulations allow ventilation rates in residential buildings to be decreased by 70 % during non-occupancy, this system is not very common in the sector. The main focus of the present study was to experimentally investigate the indoor air quality and energy consumption when using multi-zone demand-controlled ventilation in a residential building. The building studied was located in Borlänge, Sweden.

In low energy buildings and passive houses due to very low heating demands integrated heating and ventilation (VAV or DCV) systems are used to provide proper indoor climate conditions – thermal comfort and indoor air quality. Dynamic changes of indoor conditions result in permanent changes in air flow.

Demand controlled ventilation (DCV) is seen more and more as a promising way to limit the energy consumption due to ventilation in buildings. However DCV is always a compromise between decreasing the ventilation flow rates and assuring the indoor air quality (IAQ). Ventilation requirements are usually expressed as required air flow rates in the ventilation standards and regulations. Up to now, no consensus for an absolute criterion of IAQ exists in the international scientific community.

Mechanical positive input and extract ventilation are common strategies employed in English houses, generally because they provide adequate indoor air quality and specifically because they are effective at minimizing mould growth and its associated negative health consequences. Air is either exclusively supplied or extracted (never both) by a mechanical system at a prescribed airflow rate designed to ensure adequate indoor air quality.

We propose a new approach for measuring air infiltration rates in buildings. The method belongs to the class of tracer gas techniques but, unlike conventional CO2 based methods that assume the outdoor ambient CO2 concentration is constant, the proposed method recognizes that photosynthesis and respiration cycle of plants and processes associated with fuel combustion produce daily, quasi-periodic, variations in the ambient CO2 concentrations.