We are happy to share with you information on the topical sessions dedicated to airtightness namely “Building and ductwork airtightness regulations in various countries” & “Revision of ISO 9972: Improvements in the reliability of airtightness measurements”,  set to take place at the upcoming TightVent- AIVC – venticool joint conference in October 2023. We hope to see you there.

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Building and ductwork airtightness regulations in various countries

The current trend in most European countries regarding building ventilation is to follow the “build tight, ventilate right” strategy. New energy efficient buildings are indeed getting more and more airtight to avoid energy losses through uncontrolled air leakages. Instead, mechanical ventilation systems are installed to ensure a good indoor air quality (IAQ) with controlled ventilative air flowrates.

In some European countries, minimum requirements for building airtightness are included in EP-regulations, with sometimes a mandatory justification required by testing or applying certified approach, such as in France, Ireland and United Kingdom. As a result, building airtightness tests are getting commonly performed on new buildings in many European countries to quantify and limit air leakage through the envelope.
On the other hand, if the significant impact of leaky ventilation ductworks on energy use and IAQ has been well established in the literature, the awareness on this issue is raising more slowly.

In 2008 a series of VIP (from VIP 17 to VIP 27) were published by the AIVC, detailing the “Trends in the building ventilation market and drivers for changes” for 10 countries. Regulations have however evolved a lot in most countries since then. A new series of VIPs is being published to get an update on the current regulations in European countries regarding building and ductwork airtightness. They include for both, when relevant, information on:

• national requirements and drivers: airtightness indicator, requirements in the regulation, energy programs, airtightness justifications, sanctions, etc.;
• if it is included in the energy calculations and how;
• the airtightness test protocol: qualification for the testers, guidelines, requirements on measuring devices;
• tests performed: tested buildings/ductworks, database, evolution with time;
  guidelines to build airtight buildings/ductworks.

Eight VIPs have been already published in this new series, and most of them have already been presented at the last AIVC Conference in Rotterdam (for Belgium, Czech Republic, Estonia, France and Greece). Contributions from other countries are in preparation, and a total of about 15 publications is expected to give an overview of the building and ductwork airtightness trends in various countries. Some of them are presented in this Topical Session.

The objective of this session is to present three to five of the published (or under revision) AIVC VIPs on building and ductwork airtightness regulations, giving a view of the current situation in different countries.

Session programme

• Intro: Presentation of the series of AIVC VIPs on building and ductwork airtightness regulations – Nolwenn Hurel, PLEIAQ, France
• Building and ductwork airtightness in Norway: national trends and requirements, Tormod Aurlien, NMBU, Norway
• Building and ductwork airtightness in the Netherlands: national trends and requirements, Niek-Jan Bink, ACIN instrumenten, the Netherlands
• Building and ductwork airtightness in Spain: national trends and requirements, Irene Poza Casado, University of Valladolid, Spain
• Building and ductwork airtightness in Latvia: national trends and requirements, Andrejs Nitijevskis, IRBEST Ltd, Latvia
• Air tightness and its impact on energy consumption in multi-family residential buildings in Montenegro, Esad Tombarević, University of Montenegro, Montenegro

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Revision of ISO 9972: Improvements in the reliability of airtightness measurements
ISO 9972 is an international standard describing the measurement procedure and calculation methods for determining the air permeability of buildings using the fan pressurisation method. Given the impact of airtightness on building energy use, more and more tests are performed, a lot of them required by regulations. Indeed, environmental conditions during the test, and more specifically wind and temperature differences, may cause significant errors and thus increase the result uncertainty. However, when a target value must be reached in a mandatory context, knowing the test uncertainty is crucial. Recent works have underlined the need to improve the reliability of the method to measure a building’s air leakage rate as described in ISO 9972.
To address these challenges, Cerema has launched a project to review ISO 9972 and has set up a working group of international experts in the field of building airtightness testing to identify the relevant issues with the current standard and propose improvements. This project aims to lay a foundation for a thorough review and revision of the current ISO 9972 standard and this session will present the first results towards this revision.
The objective of this session is first to give an overview of the project and summarise issues with the standard that are not correct or relevant, induce difficulties in performing the test, are inconsistent with other standards or are missing in the standards. In the second part, further research and studies conducted by members of the working group will be presented, including:

• presenting a series of in-situ fan pressurization tests that have taken place under various wind conditions. The objective is to investigate the uncertainty in airtightness tests due to wind conditions and discuss the important factors. Towards quantifying these uncertainties, an analysis of declared airtightness tests has been conducted. The findings indicate that the assessment of the impact of dynamic wind should consider the following factors: i) angular exposure of the blower door to the direction of the prevailing wind speed, ii) spectral energy distribution at low frequencies and gustiness of wind, and iii) the wind speed carrying the maximum energy.
• investigating the integration of two new aspects in the fan pressurization measurement procedure: an uncertainty source related to the inhomogeneity of pressure difference along the building envelope and the autocorrelation of successive pressure difference measurements due to wind fluctuations. Those are integrated into the framework of uncertainty calculation and are then applied to a series of 30 tests conducted in repeatability conditions in an apartment in Brussels. Results show the relatively low impact of those additions to the determination of building characteristics and their large impact on both results variability and uncertainty assessment.
• introducing and evaluating the reliability of conversion equations between different indicators for air tightness using different pressure references and various geometric parameters. To do so, a statistical analysis of the French database was conducted and the compactness factor was found to be a good representation of the building geometry. The results show that different indicators can be reliably estimated by knowing the building type and geometry.

Finally, a proposal for new implementations in the standard will be presented, and discussions with the audience will cover possible further improvements.

Session programme

• Introduction to the project of ISO 9972 revision, Valérie Leprince, Cerema, France
• Impact of dynamic wind on leakage numbers obtained using fan pressurization method – conference paper, Dimitrios Kraniotis, Oslo Metropolitan University, Norway
• On the integration of envelope pressure inhomogeneity and autocorrelation in fan pressurization uncertainty analysis, Martin Prignon, Buildwise, Belgium
• Statistical analysis of the correlations between buildings air permeability indicators, Bassam Moujalled, Cerema, France
• Proposal for new implementations in ISO 9972, Benedikt Kölsch, Cerema, France
• Discussion with the audience