Building Airtightness Research Articles

Optimal Renovation Strategies through Life-Cycle Analysis in a Pilot Building Located in a Mild Mediterranean Climate

The 2030 climate and energy framework includes EU-wide targets and policy objectives for the period 2021–2030 of (1) at least 55% cuts in greenhouse gas emissions (from 1990 levels); (2) at least 32% share for renewable energy; and (3) at least 32.5% improvement in energy efficiency. In this context, the methodology of the cost-optimal level from the life-cycle cost approach has been applied to calculate the cost of renovating the existing building stock in Europe. The aim of this research is to analyze a pilot building using the cost-optimal methodology to determine the renovation measures that lead to the lowest life-cycle cost during the estimated economic life of the building. The case under study is an apartment building located in a mild Mediterranean climate (Castellon, SP). A package of 12 optimal solutions has been obtained to show the importance of the choice of the elements and systems for renovating building envelopes and how energy and economic aspects influence this choice. Simulations have shown that these packages of optimal solutions (different configurations for the building envelope, thermal bridges, airtightness and ventilation, and domestic hot water production systems) can provide savings in the primary energy consumption of up to 60%.

Building airtightness measurement uncertainty due to steady stack effect

Current building pressurization test methods considerably reduce the scope of validity of the test results when stack effect is significant without clear justification. This work attempts to fill this gap based on physical modelling and numerical simulations. In steady and no-wind conditions, it gives the error in the test result with leaks discretely distributed over the building height assuming the flow exponent is the same for all leaks. It also gives an analytical expression of the error when the building can be modelled with two leaks, one at the bottom and one at the top. The results show that the maximum absolute value of the error in the two-leak case has a very high probability to be the upper limit of the absolute value of the error obtained with any leakage distribution of more than two leaks. Consequently, one can use the two-leak model to obtain the minimum induced pressure to generate to contain the error below a given limit. For example, using an induced pressure greater than twice the stack pressure should be sufficient to contain the error in absolute value below about 5%; the error should be below 14% if the induced pressure is greater than the stack pressure. In turn, this paper gives recommendations for testing together with tables and charts to be used by field technicians.

Suite-level air tightness and compartmentalization in multi-unit residential buildings: How do we achieve our intended goals?

Control of inter-zonal air flow in multi-unit residential buildings (MURBs) is currently regulated by ASHRAE 62.2: Ventilation and Acceptable Indoor Air Quality in Residential Buildings, which specifies a maximum whole-suite air leakage rate, normalized by surface area. Despite the fact that the compartmentalization requirement has been in effect since 2013, few studies have explicitly examined the feasibility of the requirement in concrete MURBs. This paper presents results from recent inter-zonal air leakage testing completed in 12 newly constructed MURBs located in southern Ontario, Canada (N = 175). Normalized air leakage under an induced pressure difference of 50Pa (q50) ranged between 0.16 and 2.51 L/s/m2 (0.03 and 0.49cfm/ft2) of total suite surface area with a mean equal to 0.49 L/s/m2 (0.10cfm/ft2), well below ASHRAE 62.2's limit of 1.52 L/s/m2 (0.30 cfm/ft2). However, guarded blower door testing in concrete MURBs revealed large disparities between the various suite boundary types, suggesting that the whole-suite air leakage rate may not provide sufficient information about partition-based air tightness to identify potential performance issues. While guarded blower door testing provides more useful air tightness data, it is very labour-intensive and time-consuming. Completing the test prior to general occupancy improved testing efficiency slightly; however, new logistical concerns arose when testing on an active construction site. Lessons learned and recommendations for future testing efforts are discussed.

Estimating Building Airtightness from Data – A Case Study

The focus on energy conservation in buildings is increasing. Despite that, the yearly building renovation rate is only at around 1 %. To increase the renovation rate, new and time-efficient methods used for screening of large building portfolios’ energy saving potential are needed. In this paper, a re-engineered take on the classical energy signature method is applied to two renovated apartments in Denmark. The energy signature model relies on time-series measurements of space heat consumption, outdoor temperature, solar irradiation, and wind speed. The estimates obtained from it consist of—among other things—heat loss coefficient and wind-induced heat loss. This paper focuses on the latter. To validate the model estimate, the airtightness has been quantified by blower door-tests in both apartments: the results showed that one apartment is reasonable airtight, while the other suffers from significant air leakages. The energy signature and two other infiltration models, based on blower door test results, were compared. Good agreement between the results obtained from the data-driven energy signature and the blower door test were found. With use of a simple linear relation between the average infiltration and the blower door test result (q50), from the Danish national building code, the energy signature was found to overestimate the blower door test result (q50) by 33 % for the leaky apartment and underestimate the same air flow by 18 % for the other apartment. Both estimates are within the standard error of the infiltration model in the Danish national building code.

Built environment and indoor air quality: The case of volatile organic compounds

A large number of studies indicated the presence of volatile organic compounds (VOCs) of various chemical classes in indoor environments (public buildings, homes). VOCs affect the air quality indoors having an impact on human health and wellbeing. They are the result of infiltration of polluted outdoor air and emissions from various indoor sources, including building materials, consumer products (fragrances, air fresheners), activities of the occupants (cleaning) and smoking. On average, people spend a great part of their time (85 to 90%) in confined spaces (homes, office buildings and schools) exposed to a complex mixture of air contaminants at concentration levels that are often several times higher than outdoors. For many chemicals present in indoor air (and their mixtures) the risk for human health and comfort is almost unknown and difficult to predict because of the lack of toxicological data and information on the dose-response characteristics in humans or animal models. Saving of energy for homes and public buildings becomes an additional and essential criterion for the overall quality of the built environment. The need to construct airtight buildings may lead to the accumulation of air contaminants indoors and thus changing the prevailing philosophy for a healthy indoor environmental quality. The necessity emerged, in particular, for low emitting construction and building materials along with the adaptation of appropriate ventilation regimes to ensure wellbeing and comfort for building occupants. The paper provides an overview of indoor/outdoor air concentrations of volatile organic compounds in buildings. It discusses the methodological approaches and procedures applied so far to assess VOC's presence indoors and outdoors, notably benzene and formaldehyde as model compounds for indoor air quality emphasizing the needs for future research and action plans to ensure a healthy and occupant friendly indoor environment.

Airtightness Analysis of the Built Heritage–Field Measurements of Nineteenth Century Buildings through Blower Door Tests

Airtightness is a major issue in architectural design and it has a significant impact on the energy performance of buildings. Moreover, the energy behaviour of built heritage is due, to its singular characteristics, still a great unknown. The aim of this study is to establish a better knowledge of the airtightness of historical buildings, based on an in depth field study using blower-door tests. A set of 37 enclosures were analyzed inside eight buildings located in historical areas of a Spanish city with a significant built heritage. They were constructed between 1882 and 1919 and include diverse construction typologies applied for many building uses such as residential, cultural, educational, administrative and emblematic. The results indicate lower values compared to other previous airtightness studies of historical buildings. The average air change rate was found to be n50 = 9.03 h−1 and the airtightness of the enclosures presented a wide range of between 0.68 and 37.12 h−1. Three main levels of airtightness were identified with two thirds of the tested samples belonging to the intermediate level between 3–20 h−1. To conclude, several correlations have been developed which provide a method to estimate air leakage and could serve as a basis for energy performance studies of these kinds of building.

Three-dimensional characterization of air infiltration using infrared thermography

The energy consumption in buildings is still very high despite its reduction in recent years. Buildings’ conditioning is the main cause of this energy consumption and, in this sense, air infiltration has a great impact. The control of air infiltration is essential to achieve thermal comfort and energy efficiency. The evaluation of the global airtightness of the building envelope based on pressurization tests has been broadly used to determine the airtightness of buildings, but it cannot define the shape of air leakages. The use of thermography in combination with pressurization tools could be very useful.This paper presents the laboratory experimental measurements to obtain a three-dimensional definition of the air temperature when passing through a controlled envelope gap. The method is based on the bidimensional temperature matrix, captured by infrared (IR) thermography, that the air leakeage produces close to the gap, and depending on the configuration of the air inlet and airflow. The temperature measurement was done using a non-continuous rendering surface in order to avoid the Coanda effect that opaque surfaces cause, achieving in this way a 42% increase in the measuring accuracy.

Long-term performance of Passive House buildings

Long-term experience with Passive House buildings is illustrated with two early large-scale projects, a school and an office building located in Germany. Those were monitored in lump energy performance (school, commissioned 2004) and great detail (office, commissioned 2002), respectively. Moreover, they give an indication of the characteristics of such buildings subject to changes in usage intensity. Both buildings generally performed as expected with the school facing occasional overheating in the summer due to inflexible shading controls. Following an extension in schooling hours, the addition of a canteen was required and the ventilation system was adapted to the changed usage. Nevertheless, the building’s user comfort and energy performance remain high, despite exceeding the Passive House primary energy target slightly due to increased electricity consumption. The office likewise meets the calculated efficiency in operation. The ground-coupled cooling worked well despite greatly increased internal heat gains due to unexpected usage. This extra heat input did not, however, exhaust the geothermal (passive) cooling capacity for the future. Thermal comfort proved near optimal at all times, despite a very simple control regime of the one-circuit concrete core activation system for heating and cooling. In the last section, airtightness design and measurement experience in the UK and, particularly, the question of long-term stability of the airtight building envelope are assessed. It was found that measurement results are not only repeatable in relatively short intervals such as a few months. The data available suggests stability of the airtight envelope over many years. Attention is required as regards the leakage of party walls of terraced buildings which need to be integrated in the overall airtightness concept. A high permeability of party walls in terraced buildings with a common airtight envelope presents a challenge for measuring airtightness. Long-term series of airtightness measurements exist for the Kranichstein House in Darmstadt, Germany, and prove the stability of the chosen airtightness concept. Moreover, results for 17 early Passive House buildings in Germany in eight locations and various construction types revisited in 2001 (1.4 to 10 years after the initial airtightness test) suggest stability of airtightness values over time. Great advances have since been made in materials and methods available and the general understanding in the industry. This is supported by a large sample of 2934 Passive House projects of varied construction materials, locations, sizes, and usages that yielded an average airtightness test result as low as n50 = 0.41 h−1.

Numerical and experimental validations of the theoretical basis for a nozzle based pulse technique for determining building airtightness

Motivated by intentions of avoiding large net fluid flow and enabling a more practical airtightness test for large buildings, a low-pressure Pulse pressurisation technique was developed for measuring building airtightness at pressures that are considered more representative of that experienced by buildings under natural conditions. Due to the short and dynamic operation, this technique is able to minimize wind and buoyancy effects during the measurement of building pressure. The investigation, based on the “quasi-steady” temporal inertia model, explores a technique that generates a pressure pulse inside a building by releasing a known amount of air pulse over 1.5 s using a compressed air tank. The volumetric flow rate of the air pulse released from the tank is obtained by measuring the transient pressure in the air tank during a test run. The air leakage through the building envelope is then obtained by accounting for the compressibility of indoor air. Simultaneously, the pressure variation within the envelope of test building is monitored. Therefore, the leakage-pressure relationship of the building envelope can be obtained. The validity of the theoretical model and the assumptions on which the model is based are validated using experimental and numerical investigations.

Quantifying airtightness in Brazilian residential buildings with focus on its contribution to thermal comfort

ABSTRACT Airtightness refers to the amount of air leakage through a building’s envelope. This uncontrolled exchange of air between inside and outside, either infiltration or exfiltration, may lead to thermal discomfort. Nevertheless, little or no attention has been given to airtightness in some countries including Brazil. In Brazil, a range of different strategies are suitable to achieve thermal comfort depending on the several climatic regions. In those regions where winter conditions are noticeable, such as in São Paulo, airtightness is a key parameter, but it has been historically overlooked. In this work, the authors deployed the innovative Pulse test methodology to determine airtightness levels for the first time in Brazil, in the city of São Paulo. Three representative multifamily residential buildings dating from the 1970s, 1980s and 2000s were measured, and the results’ values widely ranged from 1 to 5.7 h−1, at 4 Pa. Next, dynamic building simulations were conducted using measured and representative airtightness values (converted to infiltration) to understand the contribution of this variable on the thermal comfort. The results suggested that up to 9% improvement in the thermal comfort levels could be achieved by adopting 1 h−1 as maximum infiltration, and up to 14% by adopting 0.5 h−1.

Estimation of the infiltration rate of UK homes with the divide-by-20 rule and its comparison with site measurements

Buildings are responsible for 40% of the global energy usage to which infiltration-caused heat losses are responsible for 30%. Air infiltration is the unintended flow of air through leakage paths and fundamentally determined by the airtightness of a building. In the United Kingdom, building airtightness is conventionally measured through a blower door test and used to predict air infiltration in conjunction with the divided-by-20 rule, which is a rule of thumb that has been adopted by SAP (Standard Assessment Procedure: a UK government's recommended method system for measuring the energy rating of residential dwellings) for the estimation of the infiltration-caused heat losses for dwellings. This paper assesses the representativeness of this rule of thumb by carrying out blower door and tracer gas tests in twenty one dwellings located in the East Midlands Region of the United Kingdom. Results showed that a divide-by-37 rule would be more representative. It was also seen that the air infiltration rate is overestimated by SAP when modifying factors are added. The errors are as high as 500% in some cases. The most affected dwellings were the tighter ones. A revision of the usage of the divide-by-20 rule and the modifying factors is advised.

A new methodology of evaluation of overheating in buildings

Overheating in built environments during climate extreme heat events is a major concern to human health, particularly for people vulnerable to prolonged exposure to heat and humidity. However, currently available methods for assessing the risk of overheating lack robust procedures to evaluate the effects of overheating on the comfort and health of vulnerable occupants residing in the various different dwellings. This paper developed a general methodology to define and characterise overheating events and evaluate the risk to reduced comfort and undesirable health effects of building occupants exposed to extreme heat events. Criteria to declare overheating were developed based on heat-related health outcomes related to limits for body dehydration and core temperature of healthy average-age and older adults. The methodology was then applied to a case study of a residential building with typical local construction practice for cold climates and compared with existing methods for assessing risk from exposure to extreme heat events. The results showed that all the methods predicted that highly insulated and airtight buildings are more prone to overheating than older buildings that are less well insulated and airtight. However, only the proposed methodology described in this paper predicted that natural ventilation through opening windows significantly reduced the overheating risk to below the threshold value. Furthermore, multi criteria methods might be difficult to apply in practice in that it is not guaranteed to violate all the criteria to declare a building space is not overheated. The proposed methodology sets the groundwork for establishing a benchmark model from which different overheating metrics can be compared.

An empirical approach to improving preconstruction airtightness estimates in light framed, detached homes in Canada

In order to estimate preconstruction airtightness in conventionally constructed homes, a local blower door testing population of 2297 homes was examined. Three builder-specific, geometric-based, temporally independent, multiple linear regression models were developed. Some of these builder-specific models explained over 58% (R = 0.79, p ≪ 0.001) of whole building airtightness. A five variable, geometrically based model which controlled for handicraft explained up to 74% (R = 0.87, p ≪ 0.001) of the whole building airtightness. The regression-based analyses on the local population suggested that air leakage is prominent through two building details: the floor-to-wall, and at the window-to-wall assemblies. While many comparable studies formulate airtightness models as a method to estimate post construction homes, this study demonstrated that preconstruction airtightness could be estimated with a temporally independent, builder specific, and geometrically-based method. Furthermore, this regression approach suggests that the methodology presented could be utilised as a design tool by members of the construction industry under a strict set of limitations.

Indoor Air Quality in Passivhaus Dwellings: A Literature Review.

Indoor air quality (IAQ) is a critical consideration in airtight buildings that depend on mechanical ventilation, such as those constructed to the Passivhaus standard. While previous reviews of IAQ on Passivhaus-certified buildings foccused on offices, this study examines residential buildings. A summary of data collection methods and pollutant concentrations is presented, followed by a critical discussion of the impact of Passivhaus design strategies on IAQ. This review indicates that IAQ in Passivhaus-certified dwellings is generally better than in conventional homes, but both occupant behaviour and pollution from outdoor sources play a significant role in indoor concentrations. Moreover, there are differences in data collection and reporting methods. Many of the available studies depend on short-term IAQ monitoring of less than two weeks, making it difficult to determine the longer impact of housing design on IAQ and occupants’ well-being. There is also a lack of studies from non-European countries. Future research should focus on investigating associations between IAQ and Passivhaus design strategies in hot and humid climates, where evidence is particularly lacking. Further effort is also required to investigate potential links between occupant’s perception of IAQ and physical exposure to indoor pollution. Finally, the lack of homogeneous monitoring and reporting methods for IAQ studies needs to be addressed.

Modeling dynamic behavior of volatile organic compounds in a zero energy building

With increasing building airtightness, the design of an adequate ventilation system gains importance. The first generation of ventilation systems, based on continuous supply of the nominal airflow rate, are now being replaced by demand controlled ventilation (DCV). These systems, often H2O and/or CO2 controlled, typically do not take into account the emissions of volatile organic compounds (VOCs) to the indoor environment. A small, airtight, zero energy building that has been designed as the Belgian submission to the international Solar Decathlon competition (2011) was rebuilt afterwards in Ostend, Belgium. This building will be used as test facility for the development and validation of a holistic VOC source model. In this study, results are obtained from thermal, airflow and contaminant simulation models of the test facility to check the potential of this facility for research concerning VOCs. The different models and modeling assumptions are discussed. A dynamic VOC source model, derived from literature, is used as proxy to obtain possible VOC concentrations. The results show an important influence of temperature and humidity on the indoor VOC levels with VOC concentrations exceeding health guidelines. It is therefore important to design DCV systems and controls taking into account possible elevated VOC levels and while doing so, incorporate the dynamic behavior (influence of temperature and humidity) of the VOC emissions.

Airtightness of sealed building joints: Comparison of performance before and after artificial ageing

Airtightness is considered an important factor on all levels of the building envelope, i.e. overall building envelope, on a component level and on a material level. Airtightness of the building envelope is a defining factor to achieve energy efficient and durable buildings, i.e. reduced risk of condensation and water infiltration through the building envelope, reduced risk of cold draughts and it improves the correct functioning of the HVAC-system. Over the past decades the amount of airtightness tests for newly built buildings in Belgium has significantly increased. However, the measured airtightness level of the tested buildings from 2006 to 2016 did not significantly change. This implies that there is still a lack of knowledge to achieve airtight building details, both on a design level and on the implementation of the building details. However, literature concerning airtightness of sealed building joints is very limited. In this study, the airtightness performance of different materials to seal building joints was experimentally assessed. In general, a good airtightness was achieved for all tested materials in case they were perfectly installed. However, the performance of the sealing materials was very sensitive to faulty workmanship and primarily depended on the quality of implementation, in particular for the tapes, silicone based materials and foam sealing strips. The performance of the liquid applied coating primarily depended on the characteristics of the materials and the application method was determining for the performance of the polyurethane foams.

Air Change in Low and High-Rise Apartments

Air exchange in tall apartment buildings is critical in controlling indoor environments in urban settings. Airtightness is relevant to energy efficiency, thermal comfort and air quality experienced by urban dwellers who spend much of their time indoors. While many air change measurements have been made in residential homes, fewer are available for high-rise apartments. The blower-door and CO2 exchange methods were used to measure air change in some Hong Kong apartment buildings, for comparison with those from other parts of the world. Hong Kong apartments are often small and typical rented apartments show a median of seven air changes per hour under a 50 Pa pressure difference, similar to Mediterranean houses, though much greater than the airtight buildings of Northern Europe. Extrapolation of blower-door measurements made at 50 Pa to the natural pressure difference measured for individual Hong Kong apartments provides an approximation (within 8%) of the natural air change rate measured with a tracer. Air flow is a function of the pressure difference ∆Pnf and the exponent n was found close to the typical 0.6. There was a positive relationship between air permeability and construction age, but some of this also seems to reflect varying levels of maintenance by the building management companies. The median exchange in the apartments under naturally ventilated conditions was 0.26 h−1, not atypical of some houses on the US West Coast.

Fire induced pressure in airthigh houses: Experiments and FDS validation

The need for sustainability and smaller ecological footprint lead to the construction of more airtight building envelopes with better thermal insulation in order to increase the energy efficiency of houses, according to the Energy Performance of Buildings Directive. The specific fire hazards possibly associated with such structures raised questions amongst fire community in Belgium. A full-scale experimental facility was built in the region of Mons to study the effects of both the airtightness of the building envelope and the mechanical ventilation on fire hazards and especially on fire induced pressure.Two different ventilation duct configurations were tested: one with mechanical ventilation on, the other one with the ducts closed with an airtight metal cap, the mechanical ventilation being off. Measurements were made for gas pressure, mass loss rate, gas temperature, volumetric flow rate in the ducts and for some tests O2, CO2, CO and THC concentrations were also quantified.Pressure peaks from 870 to 2035 Pa were measured without mechanical ventilation (ducts closed), while values from 420 to 750 Pa were observed with the mechanical ventilation on. The mechanical ventilation network is not sufficient to prevent pressure inside the rooms. The occupants may not succeed in escaping during a period of several minutes due to the impossibility to open inward opening doors linked to this fire induced pressure.This experimental campaign was also used for validating the field model FDS version 6.5.0 predictive capability. The effective loss coefficients of the HVAC system were calculated from all the components of the ventilation network without the need of estimation from initial pressure data. Moreover, the variation of the effective leakages area of the setup as function of fire induced pressure has to be taken into account in the pressure zone modelling in order to obtain satisfactory simulation results compared to the experimental measurements. Consequently, in addition to classical blower door tests, pressurization tests up to 600 Pa were also carried out in order to measure the effective leakages area as function of pressure according to ASTM E779. This new capability was implemeted by the developers of FDS since the 6.5.0 version. The use of validated software could be helpful to take into account the fire-induced pressure in confined dwellings in fire safety design.

Effect of enhanced supply air filtration in buildings on protecting citizens from environmental radioactive particles

The effect of enhanced filtration on protection citizens staying indoor against airborne radionuclides released during nuclear core melt accidents was determined by field measurements using outdoor particles as simulants. An electrically enhanced filter was installed in the HVAC system of an office building and its removal efficiency for particles was altered by using a separate particle charging section in power on and off positions. The effect of air filtration on indoor particle concentrations was determined by using an automated measurement system which was continuously sampling from the outdoor air, filtered supply air and exhaust air. With the aid of the measured outdoor and modelled indoor concentrations the indoor/outdoor ratio of particles of outdoor origin could be accurately determined. External charging of the particles increased the electret filters removal efficiency for 0.4 µrn size particles from 60% to 95%, resulting in decrease of the average I/O ratio of the same size particles from 0.67 to 0.40. Despite the high improvement in the supply air filtration efficiency the indoor concentrations decreased only modestly which is likely due to the leaky construction of the building, demonstrating the detrimental effect of air infiltration on the protection provided by buildings against outdoor airborne hazards. Practical implications: The developed method allows quantification of the key parameters affecting the protection of buildings against outdoor contaminants, thus allowing accurate estimation of size resolved indoor to outdoor ratios for fine particles. The electrically enhanced filter can remove effectively also submicron particles thus reducing the occupant exposure to outdoor hazardous or harmful materials. Best results can be achieved with airtight buildings.

Study on the Influence of Air Tightness of the Building Envelope on Indoor Particle Concentration

In order to grasp the building palisade structure tightness of indoor particulate matter mass concentration based on the particle penetration mechanism and settlement characteristics, this article analyzes the measurements of two different types of building air tightness of a Shenyang university office building in terms of indoor and outdoor particulate matter mass concentration levels from 2016-1-09 to 1-22, 2016-7-18 to 8-03, and 2017-2-28 to 3-13. The building outside the closed window that had no indoor source condition, the indoor office building and outdoor particle mass concentration, and the aperture size and shape of the envelope were analyzed to carry on the numerical simulation research by Fluent software, which was then analyzed; the results reveal that the measuring point of the I/O ratio is less than point B of the I/O ratio, measurement points of A linear regression fitting degree is lower than the fit of the measuring point B, and the causes for the measuring point A tightness (level 8) is superior to the measuring point B (level 4). When the gap height h is greater than 0.5 mm, the penetration rate of particles within the range of 0.25–2.5 μm particle size is close to 1. In different gap depths, the penetration rate of particles within the range of 0.1–1 μm particle size was close to 1. In diverse pressure difference, the 0.25–2.5 μm particles within the scope of penetration rate P is close to 1, the gap on both sides of the differential value ΔP; the greater the particle, the higher penetration rate. The larger the right-angle number of gap n, the lower the penetration rate of particles. The L-shaped gap and U-shaped gap have significantly better barrier effects in larger and smaller particles than the rectangular gap. The research results in this paper can help people understand and effectively control the influence of outdoor particles on the indoor air quality and provide reference data for the prediction of indoor particle mass concentration in buildings, which has theoretical basis and practical significance.