Airbase publication

The window/door opening behavior of occupants is a very important factor in determining the airflows and ventilation conditions in buildings, on which indoor pollutant concentration and transport are highly dependent. A two-room residence model was simulated in this study to analyze the airflow characteristics and pollutant transport under different window/door opening behaviors. Airflows were unidirectional and the residence could not be treated as a well-mixed zone when there were no temperature differences.

Individual effects of temperature and humidity on formaldehyde emissions from manufactured fiberboards have been studied previously, but their combined effects and possible correlation with initial emittable concentration (C0) of building materials have not been reported yet. This paper investigated their combined effects on C0 theoretically from microcosmic perspective. Total formaldehyde content related to humidity and formaldehyde molecular phases affected by temperature in the porous material were considered.

Initial emittable concentration (C0), diffusion coefficient (Dm) and partition coefficient (K) are the three key emission parameters determining formaldehyde emissions from “dry” building materials. Previous studies of humidity effect on formaldehyde emissions were mainly focused on the analysis of steady-state emission rates or concentrations, whereas humidity effects on emission parameters were seldom discussed.

Building energy simulation is essential for most architectural design projects. Many models have been developed to predict the indoor air temperature and relative humidity as well as the building’s heating and cooling loads. However, in most building energy analysis the calculation of heat conduction through walls usually neglects the transport and storage of moisture in porous building materials, and the interaction between hygrothermal transfer and airflow inside the building.

The IEA EBC Annex 68 project on “Indoor Air Quality Design and Control in Low Energy Residential Buildings” has been recently completed. The project considered indoor air pollution loads in dwellings, particularly how such pollutants are emitted in dependency of the hygrothermal conditions: temperature, moisture and air flows. Thus, a proper understanding of the mutual interactions between hygrothermal conditions and pollutants was needed to obtain optimal paradigms for demand-controlled ventilation.

The overall objective of the “Annex 68” Project, which belongs to the International Energy Agency’s “Energy in Buildings and Communities” Implementing Agreement, has been to develop the fundamental basis for optimal design and control strategies for good Indoor Air Quality (IAQ) in highly energy efficient residential buildings, and to disseminate this information in a practically applicable guide. The strategies shall facilitate the possibility to design and operate residential buildings with minimal energy use, while ensuring impeccable indoor climates.

In order to evaluate the impacts of volatile organic compounds (VOCs) emissions from building materials on the indoor pollution load and indoor air quality beyond the standard chamber test conditions and test period, mechanistic emission source models have been developed in the past. However, very limited data are available for the required model parameters including the initial concentration (Cm0), in-material diffusion coefficient (Dm), partition coefficient (Kma), and convective mass transfer coefficient (km).

IEA-EBC Annex 68 “Indoor Air Quality Design and Control in Low Energy Residential Buildings” is an international collaborative project to provide new insight into methods and strategies for ensuring high indoor air quality in dwellings during both design and operation phase of their life cycle. Within the Annex 68 work, we defined a common exercise, which focusses on model-to-model comparison of different simulation tools to assess their modelling abilities with respect to combined heat, moisture and pollution transfer.

To achieve stringent energy objectives, new dwellings are subject to energy conservation measures including low air permeability and high levels of insulation. Mechanical Ventilation with Heat Recovery (MVHR) can be used to control the balance between energy efficiency and Indoor Air Quality (IAQ) in these buildings. This paper evaluates the effectiveness of the design and operational strategies adopted in a new development comprising two apartment blocks in East London.

In order to achieve nearly net zero energy use, both new and energy refurbished existing buildings will in the future need to be still more efficient and optimized. Since such buildings can be expected to be already well insulated, airtight, and have heat recovery systems installed, one of the next focal points to limiting energy consumption for thermally conditioning the indoor environment will be to possibly reducing the ventilation rate, or making it in a new way demand controlled. However, this must be done such that it does not have adverse effects on indoor air quality (IAQ).