Blower Door Research Articles

Evaluating indoor air quality and energy impacts of ventilation in a net-zero energy house using a coupled model

The National Institute of Standards and Technology constructed the Net-Zero Energy Residential Test Facility to support the development and adoption of cost-effective net-zero energy designs and technologies. In support of indoor air quality goals, contaminant source control approaches were implemented that minimized the use of products containing urea-formaldehyde resin and utilized products with relatively low volatile organic compound emissions. Indoor and outdoor concentrations of formaldehyde and acetaldehyde were approximately measured monthly for 15 months. Independent emission measurements of formaldehyde were made in a small chamber system to determine the emission rates from samples of the wood flooring, plywood, and wood cabinetry taken from the house. Blower door tests were performed to determine the leakage area of the exterior envelope, the interior floors, and transfer grilles between floors. Real-time formaldehyde concentration and energy measurements were used to verify the indoor concentrations and energy predictions of a coupled CONTAM-EnergyPlus model of the house. The verified model was then used to evaluate the impacts of different outdoor air ventilation rates on indoor concentrations and energy. The current work demonstrates the need for consideration of source control options during product selection and the provision of mechanical ventilation, especially in homes with relatively airtight envelopes.

Indoor air quality and wildfire smoke impacts in the Pacific Northwest

Efforts to improve energy efficiency in homes and buildings have led to tighter structures. However, these changes can also produce negative consequences for indoor air quality and human health. One of the dramatic effects of climate change and weather is the increase in destructive wildfires, such as those experienced in the Pacific Northwest during the summer of 2015. The current article presents data for measurements at two houses during periods with and without high levels of wildfire smoke outdoors. For each house, indoor and outdoor pollutant measurements were obtained for ozone (O3), fine particulate matter (PM2.5), and volatile organic compounds along with outdoor weather conditions and occupant activities including the use of windows and doors. The volatile organic compound measurements were obtained using a Proton Transfer Reaction Mass Spectrometer. Compounds monitored included acetonitrile (a biomass burning tracer), formaldehyde, acetaldehyde, methanol, acetone, benzene, toluene, and C2-alkylbenzenes (i.e., sum of xylenes and ethylbenzene), C3-alkylbenzenes (i.e., sum of trimethylbenzene, ethyltoluene, and propylbenzene isomers), and C4-alkylbenzenes (i.e., sum of tetramethylbenzene and its isomers). A carbon dioxide tracer method was used to measure in situ ventilation rates, and blower door tests were also completed to determine standard ventilation rates. For smoky periods with elevated outdoor pollutant levels, penetration factors, defined as the ratio of indoor/outdoor concentrations were quite low. Penetration factors for PM2.5 were 11% for H2 and 15% for H3, except when windows or doors were open. The penetration factors for O3 were also low at 24% for H2 and 5% for H3. Elevated indoor volatile organic compound levels were not typically associated with outdoor levels, but reflected significant indoor sources. During smoke events, acetonitrile, a biomass burning tracer compound, was elevated outdoors and indoors in both houses, and benzene was elevated outdoors and indoors in H3.

Analysis of Airtightness and Air Leakage of Wooden Houses in Korea

Airtightness of buildings is one of critical aspects of its energy performance. To build up references of air-tightness of wooden houses built in Korea, blower door tests have been carried out in 42 houses since 2006. Causes of air leakage were investigated recently. The average value of air change rate was 3.7 h-1 for light frame house and 5.5 h-1 for post-beam construction at ACH50 (air change per hour at 50 Pa air pressure difference). Foam type insulation was more advantageous in ensuring building airtightness than glass fiber batt. Airtightness of wooden houses which were constructed after 2010 was improved to have less than 1.5 h-1 of ACH50, threshold for application of artificial air change. The average air change rate of CLT (cross laminated timber) houses showed the lowest value, 1.1 h-1, among the tested structures.

Evaluating the effectiveness of improved workmanship quality on the airtightness of Dutch detached houses

Increasing the airtightness of buildings can contribute in coming to energy neutral buildings. This paper evaluates two possible measures: modest technical improvements and coaching of construction teams. Beforehand, the specific leakage rate of 44 detached houses was measured using a blower door test and by means of statistics, the most pressing problems were determined. An educational session was developed to explain construction workers the relevance of and their own influence on building airtight houses. The effectiveness of the technical improvements and the education was assessed by evaluating 14 new houses. This evaluation showed a significantly improved airtightness.

Impact of a Pilot Draught Sealing Program on Public Housing Air Permeability

Abstract: Air tightness (or permeability) is a property of a building envelope that describes how air moves though it when subjected to a pressure difference (wind, stack effect, etc.), this impacts on building performance including energy usage, thermal comfort and air quality. The NSW Land and Housing Corporation (LAHC) implemented a pilot program of simple leak (or draught) sealing measures to improve air permeability and building performance on some of its domestic building stock. The effectiveness of this program was evaluated via blower door testing to international standards including measuring overall envelope permeability, and qualitative and quantitative investigation of the leakage paths through the structure. Testing was undertaken before and after the leak sealing interventions to determine the relative impact, the extent of the works implemented was documented, and potential for further improvements investigated.

Experimental analysis of building airtightness in traditional residential Portuguese buildings

It is currently recognized that the residential building sector is one of the largest energy consumers in the world. The energy crisis of the 1970s was important for drawing attention to the subject of energy consumption and the necessity to save energy. The airtightness of buildings is an important factor affecting a building’s energy consumption and also energy-saving potential. On the other hand, the ventilation rate has also a significant effect on indoor air quality and is assumed to be an essential criterion of a building’s performance. However, most of the existing research in this area has been developed in cold climates and there is a research gap with regard to countries in warmer climates such as those close to the Mediterranean Sea. Therefore, this research aimed to study the airtightness and ventilation rate of existing buildings by employing in-situ measurements.In-situ measurements were achieved using the fan pressurization test (Blower Door Test) method.According to the selected case studies, the results of the measurements indicate a correlation between building typology, airtightness, and ventilation rate.

Building air leakage analysis for individual apartments in North China

There is little known on the airtightness performance of apartment building in China. The present study intends to investigate the airtightness performance of twelve individual apartments from four buildings in China's cold area using the blower door method. The air leakage of two building components of each of the three individual apartments from the 4# building was further investigated by a series of blower door tests. The normality test was performed to the test results, and the correlation coefficients between the air leakage and possible influence factors were analyzed.Test results show that the air change rate of the tested individual apartments at 50Pa changes from 1.14 h−1 to 2.44 h−1 with an average of 1.77 h−1. The check valves at the inlets of the discharge flue and exhaust airway were tested to be leakier than the outer windows and doors in the three measured apartments from the 4# building. Results of statistical analysis show that the data was significantly drawn from a normally distributed population at the 0.05 significance level, and the envelope area and the joint length of the opening part of the windows and doors were identified as the main factors that influence the air leakage of the tested apartments at the 0.05 significance level.

Assessment of ventilation effectiveness in exiting residential building in mediterranean countries: Case study, existing residential building in Portugal

Natural ventilation as a part of a buildinǵs function that has a strong effect on human comfort. The reduction of natural ventilation and infiltration, as a part of the ventilation system in the old existing buildings, due to intervention actions, have been causing a reduction in indoor air quality and an increment of relative humidity levels in the indoor environment.Providing optimal indoor condition is not only related to the renewal of the air but also with its distribution. Hence airflow patterns in historical buildings influence interior comfort conditions. The aim of this work is to assess the effectiveness of the existing natural ventilation system in the old and historical buildings by different natural ventilation strategies.To achieve the proposed objective, the research was developed resorting to in-situ measurements and simulation methods The simulation was performed with the Design-Builder software and the main goal was answering to the following question:- What are the existing conditions of the building in concern of the airflow circulation and distribution?The in-situ measurements were performed using Blower Door Test method in order to determine the existing building airtightness. Based on the obtained results for each building the intention is answering the following question:- Due to the limitation of the historical urban areas, which natural ventilation strategy is more effective?The results of this research can be interesting for architects, engineers, and people, who are working on intervention and renovation of old existing buildings.

Airtightness field tests of residential buildings in Dalian, China

There is little known on the airtightness performance of residential buildings in China. The present study intends to investigate the airtightness performance of ten detached houses in China's cold area using “blower door test”. The thermal infrared imager and smoke pencil were used to find out the typical air leakage places in the building envelope.Test results show that the air change rate at the pressure difference of 50 Pa of the tested houses varies from 1.89 h−1 to 0.84 h−1 with a mean value of 1.42 h−1. The typical air leakage places happen at the reserved holes in the outer wall that were not well filled after construction, the frames of window and door that were not fitted correctly and the draught seal was deformed, and the check valves at the inlets of the discharge flue and exhaust airway in the house.The tested detached houses were ranked by their airtightness performance. The total joint length of the opening part of the windows and doors was estimated for each detached house and a linear correlation between the n50 and the joint length of the opening part of the windows and doors was examined.

An infrared thermography passive approach to assess the effect of leakage points in buildings

Energy consumption is one of the major concerns of European citizens and governments. In the EU, buildings use 40% of total energy consumption and generate 36% of greenhouse gases. Therefore, buildings energy efficiency must be optimized, which requires, among others, minimizing infiltrations through the envelope. The measurement of the air leakages through a building envelope is usually carried out by means of the fan pressurization method (Blower Door Test). Although useful for assessing the airtightness of buildings no information is obtained regarding the air leakage pathways. For that, other techniques such as infrared thermography (IRT) can be used.This work presents the results of an experimental campaign that aimed to assess the applicability of IRT to detected air leakage through the roller shutter handle and the window frame of a room. A quantitative approach for results analysis was implemented and the contribution for airtightness of both roller shutter handle and window frame was also evaluated using the Blower Door Test.It was possible to conclude that the window frame had a larger contribution to the air flow rate than the roller shutter handle (109.4m3/h and 21.7m3/h, at a pressure difference of 50Pa). Qualitative analysis of the thermal images indicated that a colder area near the leakage point can be detected and that it grows with the increase of the pressure difference. The quantitative approach showed that a stabilization of the surface temperature close to the value of the outdoor temperature occurred and the relative differences are around 15% both for the window frame and the roller shutter handle. It also showed that, in most cases, the first pressure step (ΔP=25Pa) is responsible for about 60% of the differences in the superficial temperature. A good correlation was found between the proposed Pressurization Thermal Index and the temperature gradient between the exterior air temperature and the initial superficial temperature (ranging from 0.74 to 0.82).

Air-tightness test and air infiltration estimation of an ultra-low energy building

The air-tightness performance of residential buildings in China is not fully investigated. This study intends to investigate the air-tightness performance of an ultra-low energy building in a cold area of China. The air-tightness of the building envelope was measured using blower door method and the whole year air infiltration of the building was simulated by a multi-zone network airflow model based on the air-tightness test results. A thermal infrared imager and a smoke pencil were used to find out the typical air leakage places in the building envelope. The leakage areas of the typical air leakage places are found by measuring the whole building and then sealing the corresponding component and determining the reduction in the building effective leakage area. Test results show that the air change rates of the building at the pressure difference of 50 Pa (ACH50) under the depressurization and pressurization modes are 0.5 and 0.49 h−1, respectively. Simulations show that the air change rate of building under the weather conditions of Dalian changes from 0 to 0.12 h−1 with an average of 0.05 h−1. The typical air leakage places of the building were the reserved holes in the building envelope, the junctions of the windows with the walls, the deformation parts of the outer windows and doors, and the joints and vents that imprecisely sealed. The exhaust vents were found to be the most significant source of leakage among the tested typical air leakage places.

Influence of air tightness of the building on its energy-efficiency in single-family buildings in Poland

This publication focuses on assessing the impact of the tightness of single-family houses with a higher energy standard on their energy demand for heating. To formulate conclusions quantitative and qualitative research, including tightness test (blower door) has been conducted in energy-efficient and passive houses. In the next step, energy demand for heating has been estimated. Based on the observation and results, the simulation of the impact of reducing the flow of infiltrated air through leaks in the buildings for energy demand for heating is calculated. The simulation results confirm the dependence between the tightness of the building and energy demand.

Exhaust ventilation in attached garages improves residential indoor air quality.

Previous research has shown that indoor benzene levels in homes with attached garages are higher than homes without attached garages. Exhaust ventilation in attached garages is one possible intervention to reduce these concentrations. To evaluate the effectiveness of this intervention, a randomized crossover study was conducted in 33 Ottawa homes inwinter 2014. VOCs including benzene, toluene, ethylbenzene, and xylenes, nitrogen dioxide, carbon monoxide, and air exchange rates were measured over four 48-hour periods when a garage exhaust fan was turned on or off. A blower door test conducted in each garage was used to determine the required exhaust fan flow rate to provide a depressurization of 5Pa in each garage relative to the home. When corrected for ambient concentrations, the fan decreased geometric mean indoor benzene concentrations from1.04 to0.40μg/m3 , or by 62% (P<.05). The garage exhaust fan also significantly reduced outdoor-corrected geometric mean indoor concentrations of other pollutants, including toluene (53%), ethylbenzene (47%), m,p-xylene (45%), o-xylene (43%), and carbon monoxide (23%) (P<.05) while having no impact on the home air exchange rate. This study provides evidence that mechanical exhaust ventilation in attached garages can reduce indoor concentrations of pollutants originating from within attached garages.

Assessment of Energy Efficiency Measures on Indoor Air Quality and Microclimate in Buildings of Liepaja Municipality

Eight municipality buildings that have undergone major energy efficiency improvements have been studied. The main aim is to assess indoor air quality and microclimate in the context of energy efficiency, indoor air quality and thermal comfort dilemma in the studied buildings. Microclimate and CO2 measurements were carried out. Tracer gas method was used to determine air exchange rate and blower door tests were conducted to determine building tightness. Results show that ventilation systems are underperforming because they are not used as expected, thus leading to decreased indoor air quality and thermal comfort. Further assessment of economic aspects would be necessary to evaluate the indoor air quality impact on student and teacher health and productivity and its impact on municipality budgets.

An Analytical Approach to the Ventilation Effectiveness of Mediterranean Buildings. Case Study: Existing Residential Building, Portugal

Building airtightness assumes an important role in the energy saving and the indoor thermal comfort. Ventilation rates bring significant impacts on energy usage in the constructions and indoor contaminant concentrations and also setting them as the key parameters in building performance.Ventilation rate have been measured in building for a long time, and there are some developed measurement methodologies related to it in the research domains. However, most of the investigations in recent years have been done usually in the cold climate conditions, while Mediterranean construction are not deeply investigated in the literature.In this paper, the authors present the obtained results of an experimental research which is carried out on the Portuguese residential buildings. The investigation is done by fan pressurization methods, also known as “Blower Door Test (BDT)” as the measurement method as well as Design Builder (DB) as the simulation software. The airtightness measurement of the existing buildings and the influence of air leakage on energy consumption and indoor comfort in different Portuguese construction typologies are focused on the aim of the research.The important parameters of the building such as whole-building air change rates, building infiltration rates, and ventilation effectiveness rate in the residential building are also considered in this research.

An approach to modelling envelope airtightness in multi-family social housing in Mediterranean Europe based on the situation in Spain

Building hygrothermal performance, indoor air quality and energy consumption depend heavily on envelope airtightness. Over the last three decades, single-family dwellings have been amply studied in this respect by researchers in North Europe, the United States and Canada. However, very few studies have been conducted on airtightness in multi-family housing in warm climates such as Mediterranean Europe. This paper aims to enhance the understanding of building airtightness in early twenty-first-century multi-family buildings in southern Spain. Blower Door tests were conducted in 45 units in seven such buildings. The main airtightness parameter values found are reported and compared to the data for other buildings in southern Europe. The paper includes a statistical analysis of the findings, characterises building types and describes the protocol used to identify and quantify air leakage pathways. The conclusion drawn is that although a rough predictive model can be developed, the results are widely scattered due to the impact of the random component of manual construction, even in buildings with identical construction characteristics and types. The values recorded are nonetheless consistent with the findings for other European surveys.

Indoor Air Quality Performance of Ventilation Systems in Classrooms

This study aims to evaluate the field performance and the efficiency of ventilation systems in school buildings. Three classrooms installed with ventilation systems in a high school in Seoul were selected as a test bed for this study. The ventilation systems consisted of two types of multi air-conditioning ventilation system and a window type air-conditioning ventilation system. The ventilation performance was measured by the blower door and tracer gas methods as follows: (1) Evaluation of air tightness and air infiltration in the classrooms; (2) Indoor ventilation performance based on the operating condition of ventilation systems; (3) Ventilation performance based on the operating conditions of ventilation systems and air-conditioners; and (4) Local ventilation efficiency and performance based on the operating status of the ventilation systems and air-conditioners. As a result, the ventilation efficiency was measured at 34.8%-97.8% for the duct type of ventilation and 82.6% for the window type ventilation. In this study, classroom characteristics such as high air infiltration low air tightness lowered the ventilation effectiveness. The ventilation efficiency varied based on the location of air inlet and outlet ducts and the existence of furniture. However, local ventilation efficiency was not significantly affected according to the results of this study. The results showed that a ventilation rate of 1000 cubic meters per hour (CMH) or more would be required to maintain 1000 ppm of CO2 concentrations as per IAQ criteria for Korean classrooms.

Large Buildings Airtightness Measurements using Ventilation Systems

Due to high cost and limitations in availability of specialized and expensive measurement equipment, airtightnes testing of large buildings is relatively uncommon. Sometimes, in existing buildings, leakage measurements can be conducted with the use of ventilation systems, which is allowed by some standards. For this kind of test one can use the measurement of the airflow rate at fans (fan inlet nozzles), at variable air volume terminals (VAV) or in the duct system. The accuracy of the airflow measurement is crucial in these cases.Attention should be paid to a number of aspects related to building preparation and test procedure. The problems of large building leakage tests are discussed in this paper, as well as typical design and workmanship mistakes. This paper presents the methodology and results of airtightness measurements of the selected facilities’ envelopes, using a ventilation system in comparison to blower-door set-up.In the case of multi-zone airtightness measurements, the ventilation system can generate an appropriate pressure in adjacent zones. Another application is the coarse testing of airtightness of the building, when the result of the measurement can be approximate. In the case of final measurement of the airtightness of the building with the use of a ventilation system, the biggest problem is reliable measurement of the airflow rate with the accuracy required by the standards. To obtain accurate results much more expertise and effort are required than in the case of measurement with a set of typical blower door fans.

Estimating the background ventilation rates in new-build UK dwellings – Is n50/20 appropriate?

In the UK, a rule of thumb applied to air permeability is commonly employed when estimating background ventilation rates from pressurisation test data. However, this may lead to significant errors in estimating the infiltration rates in UK new-build dwellings, resulting in poor estimation of the dwellings in-use energy and CO2emissions, and the adoption of ventilation strategies leading to either unacceptable indoor air quality or unnecessary energy consumption. In this paper, a preliminary investigation into the applicability of the rule of thumb is undertaken. Background ventilation rates in four new-build dwellings in the UK are determined using the tracer gas decay method and also the pressurisation (blower door) method coupled with both the conventional n50/20 and (in the UK) q50/20 rule of thumb, and Sherman’s modified rule of thumb, which takes into account other building-related factors. The conventional method overestimated the air-change rate in two of the dwellings and underestimated it in the other two dwellings. The modified rule of thumb produced comparable results for two of the dwellings, but significantly underestimated the air-change rate in the other two dwellings. These results suggest that more work needs to be done to devise appropriate climate and building-related correction factors for the UK.

Permeability Measurements of a Passive House During Two Construction Stages

Usually air permeability is measured for a specific building only once: either when the building construction is was just finished or when the building is already in use. In this paper we present a novel aspect. We researched if there is any variation of the building permeability during its construction. We followed the evolution of the building airtightness during the construction of a passive house carrying out permeability measurements in two different phases: (1) airtight construction but not finished and without HVAC, and (2) finished construction with HVAC. For each phase, we used a blower door experiment stand to measure the airflow at different indoor-outdoor pressure differences in two conditions (depressurization and pressurization). We obtained air change rate at 50Pa well below the maximum limit characteristic to passive house. However an intriguing result was found: the measured permeability for the finished building is slightly bigger than the measured permeability for the unfinished building. On one side the better finishing of the walls and windows lead to an airtightness improvement, but on the other side the new HVAC wall penetrations and HVAC terminals (inlets and exhausts) lead to an airtightness aggravation just enough to turn over the improvement brought by the better state of building finishing.