Airbase publication

Mandatory building airtightness testing has come gradually into force in European countries mostly because of the increasing weight of building leakage energy impact on the overall energy performance of low-energy buildings. Therefore, airtightness level of new buildings has significantly improved in the last decade.
However, until now, low expertise is available about the durability of building airtightness at mid- and long-term scales.

Demand controlled ventilation (DCV) refers to a ventilation system with air flow rates that are controlled based on a measurement of an indoor air quality (IAQ) and/or thermal comfort parameter. DCV operates at reduced air flow rates during a large amount of the operation time. Due to this decrease, less energy is needed for fan operation and heating/cooling the supply air. However, uncertainty still exists about the IAQ performance and ventilation efficiency in the room, especially at lower air flow rates.

One of the key objectives of the IEA Annex 68 research programme entitled “Indoor Air Quality Design and Control in Low Energy Residential Buildings” is to provide a generic guideline for the design and operation of ventilation in residential buildings. They need to have minimal energy consumption, and at the same time maintain a high level of Indoor Air Quality (IAQ). The paper reports on preliminary results of an interview survey conducted among different stakeholders involved in design, installation and operation of residential ventilation in countries involved in the Annex.

The industry is now focusing in system solutions and the goal is to be able to deliver complete reliable, energy efficient solutions that is understandable and easy to maintain by the normal service personal.  
In order to do this the basic products have to perform exactly as they are described in the technical documentation. The documentation have to help the designer and the installer to actually build the system in the correct way without compromises from other stakeholders. 

There are several methods for measuring air tightness that may result in different values and sometimes quite different uncertainties. The two main approaches trade off bias and precision errors and thus result indifferent outcomes for accuracy and repeatability.  To interpret results from the two approaches, various questions need to be addressed, such as the need to measure the flow exponent, the need to make both pressurization and depressurization measurements and the role of wind in determining the accuracy and precision of the results.

Air infiltration holds a central role in building energy consumption and is associated to several building physics phenomena. Air infiltration in buildings due to wind-induced pressure is a complex process, strongly influenced by the turbulent nature of wind. This extended summary highlights the findings of a series of studies with focus on unsteady wind and its impact on air exchangesin buildings. The focus is on wind gustiness and its relation to air infiltration under natural conditions.

The airtightness just after the end of a building phase is assumed to be relevant criteria for high energy performance. Testing on site the initial performance of the airtightness via the blower door test has become nowadays a common practice but generally implemented before the occupation of the building. But a lot of questions are still remaining targeting the sustainability of the performances.

Wind pressure and thermal forces are driving forces for pressure difference on the building envelope. In European and German standards infiltration is calculated using wind speed, temperature difference and wind pressure coefficients resulting from upstream and downstream flow on the building envelope. This long term measurements shall present measured pressure differences on the building envelope in comparison to those calculations

With lower air leakage in modern homes, ventilation of homes has become more important than ever before. It seems however that we are getting it very wrong. A lack of ventilation can cause building sickness, with degradation of the physical building and also poor air quality which has a big impact on the occupants themselves. Our statistics show that designers and contractors are still not getting it right, leaving us with a generation of poorly ventilated housing stock.

There have been many new sensors introduced on the market claiming that they can perform accurate measurements of Indoor Air Quality. Many of them are low-cost sensors that can be applied at the mass scale. The subsequent question is what is and should be considered to be the metric of Indoor Air Quality. No consesus on this matter has yet been achieved. Few metrics have been proposed in the past including most known CO2 and TVOC concentrations but actually only CO2 concentration has been widely used in the applications related to built environment and HVAC.