moisture

The means for keeping the indoor relative humidity (RH) and pollutant concentration below a threshold level of interests are necessary and essential to improving building performance in terms of indoor air quality (IAQ), energy performance and durability of building materials. In this paper, the similarity between the moisture and VOC (Volatile Organic Compounds) transport models is applied to study the effect of toluene (a typical VOC) and moisture buffering capacities of a hemp concrete wall on indoor toluene concentration and RH.

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.

Purpose of the work

This extended summary is a part of a more extensive summary (technote to be published) that compiles a number of AIVC publications that deal with ventilation and health in relation to moisture in air, and the development over time.

A smart ventilation system is generally equipped with a range of sensors. The data – or data derived from it - collected by these sensors can be used by both building owners, occupants and managers. A new generation of IoT  enabled residential ventilation systems allows collecting and analysing this data at scale to get a better view on typical IAQ conditions in dwellings. In this paper, the results from such an analysis on the first 900 installed devices of a new model with respect to moisture in relatively new Belgian dwellings is presented. 

Mastering building airtightness is essential to meet the requirements of current and future building codes, not only for saving energy but also for ensuring moisture safety. Perfect airtightness is difficult to achieve: failures are often observed, due to bad design or poor workmanship. Some published investigations proved that leaking air mostly flows through porous material and thin air channels, due to material imperfections and construction tolerances.

One of the most commonly used strategies to reduce the heating demand in low energy buildings is reducing the leakage level of the building envelope. Dedicated ventilation systems are then installed to compensate for the reduced air change rate in an energy efficient way. Most occupants, however, operate their ventilation system at very low flow rates. Together with the emission of bio-effluents, linked to the presence of the occupants, moisture production related to household activities is one of the most important sources of indoor air pollution in dwellings.

In this paper, the new capabilities of PowerDomus to simulate central HVAC systems combined to its whole-building hygrothermal model is presented. First, models for the primary (chiller, cooling tower, primary pumps and condensation pumps) and secondary (cooling and dehumidifying coil, humidifier, fan and mixing box) systems are presented. Those mathematical models have been integrated into the whole-building PowerDomus program.