Airtightness and energy impact of air infiltration in residential buildings in Spain

Addressing the airtightness of the building envelope is key to achieve thermal comfort, good performance of ventilation systems and to avoid excessive energy consumption. Previous studies have estimated an energy impact on infiltration on the heating demand between 2 and 20 kWh/(m2·y) in regions with temperate climates. In Spain, this issue has not yet been addressed in depth. This study aims to assess the energy impact of uncontrolled air flows through the building envelope in residential buildings in Spain.

Exist’air: airtightness measurement campaign and ventilation evaluation in 117 pre-2005 French dwellings

Between 2017 and 2018, the Centre for Studies and Expertise on Risks, the Environment, Mobility and Planning (Cerema) organized an airtightness measurement campaign in 117 multi-family collective and single-family French dwellings. These dwellings were built before 2005, that is, before the release in 2005 of the fifth French thermal regulation for new dwellings, that was the first to introduce specific requirements for airtightness.

New findings on measurements of very airtight buildings and apartments

The trend in European countries, such as Belgium, France and Germany is that the quality of the airtightness of the building envelope is getting better and better. This is true for small, airtight apartments, Passive houses and some large buildings with an excellent airtightness due to special requirements, e.g. oxygen reduction or fire protection.

Comparison between infiltration rate predictions using the divide-by-20 rule of thumb and real measurements

Across different territories there are various normative models for assessing energy demand of domestic dwellings, which use simplified approaches to account for the heat loss due to the air infiltration of a building.  For instance, the United Kingdom uses a dwelling energy model, known as the Standard Assessment Procedure (SAP), and this utilises a process where the measured air permeability value (q50), is simply divided by 20 to provide an infiltration rate (subsequent modification factors are then used for factors such as sheltering etc.).

On the experimental validation of the infiltration model DOMVENT3D

Buildings represent approximately 40% of global energy demand and heat loss induced by uncontrolled air leakage through the building fabric can represent up to one third of the heating load in a building. This leakage of air at ambient pressure levels, is known as air infiltration and can be measured by tracer gas means, however, the method is disruptive and invasive. Air infiltration models are a non-disruptive way to calculate predictive values for air infiltration in buildings.

How Accurate is our Leakage Extrapolation? Modeling Building Leakage Using the Darcy-Weisbach Equation

This study used a mathematical model to explore the accuracy of extrapolating multi-point blower door test results down to lower pressures at which building infiltration usually occurs naturally.  The mathematical model was applied to leaks of five different widths.  The leakage of the five different widths was then combined in different distributions to simulate total building leakage.  The calculated total building leakage was then compared to an extrapolation from the test pressures using a power law curve fit.

Airtightness and non-uniformity of ventilation rates in a naturally ventilated building with trickle vents

Infiltration is an uncontrolled contribution to ventilation in a building and can contribute significantly to the total ventilation rate, particularly in older, leaky, dwellings which can rely on infiltration to provide adequate indoor air quality. However, as explored in this paper, using a whole house airtightness metric to characterise ventilation rates can fail to identify low ventilation rates in specific rooms. 

Influence of the external pressure tap position on the airtightness test result

Due to the wind induced pressure, different results may be obtained if the inside-outside pressure difference is measured across different locations on the building envelope, i.e. if the external pressure tap of a differential pressure sensor measuring this pressure difference is placed in different positions. Therefore, the position of the external pressure tap may influence an airtightness test result as well.

Airtightness of buildings – Considerations regarding place and nature of pressure taps

This paper discusses two particular points of the buildings airtightness measurement method (ISO 9972) in relation with the pressure difference: (1) the nature of the pressure tap and (2) the place of the pressure tap outside. 

Quantification of uncertainty in zero-flow pressure approximation due to short-term wind fluctuations

Uncertainties in airtightness measured using fan pressurization test should not be defined by the scattering of the points around the line defined using ordinary least square method anymore. Its definition requires first to know the uncertainties in pressure and airflow measurements. This works aims at quantifying one of the component of the envelope pressure uncertainty: the uncertainty in zero-flow pressure approximation due to short-term fluctuation of wind speed and direction.

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