AIVC reference on Pressurisation - Infiltration Correlation: Models

#No3125 The use of a guarded zone pressurization technique to measure air flow permeabilities of a multizone building.

AUTHOR Furbringer J M, Roecker C, Roulet C A

BIBINF in: "Effective Ventilation", 9th AIVC Conference, Gent, Belgium, 12-15 September, 1988. #DATE 00:09:1988 in English

ABSTRACT In the past few years, research efforts have been made to acquire accurate knowledge about infiltration and ventilation in multi-zone buildings. By this way, a wide variety of modelling techniques have been developed which suffer of a lack of satisfactory validations. The purpose of this work is to set up a data bank of high quality measurements which will serve to carry out an empirical validation of multi-zone air infiltration programs. Among other data, a complete set of air flow permeabilities of a well known experimental midsize building will be included to this bank. We use the guarded zone pressurization technique for the purpose of measuring this set. The system is made of two computer controlled fans which automatically pressurize the different rooms of the building. Pressures and air flows are sampled and gathered during the overall experiment which runs generally over one night. Values of the corresponding permeabilities are calculated from these data through a mean square fit. An overview of the procedure used to measure these permeabilities as well as a description of the experimental equipment for this purpose, is presented in this paper. The measured permeabilities and a discussion of their values are also given.

KEYWORDS pressurization, air flow, modelling, permeability

#No3376 Stairwell pressurization in a cold climate.

AUTHOR Clark J A, Harris J W

BIBINF Preprint: Ashrae Transactions, Vol 95, Part 1, 5pp, 3 figs, 3 refs. #DATE 00:00:1989 in English

ABSTRACT The three national model building codes require pressurization systems for high-rise buildings. The goal of stairwell pressurization is to provide a relatively smoke-free evacuation route by maintaining a pressure differential across a stairwell door opening, thereby preventing smoke infiltration. Thisgoal is difficult to attain in cold climates due to weather extremes that relate to stack effect, increased wind effect, and the additional problem of heating the stairwell. This paper discusses the design, construction, testing, and computer modelling of the stairwell pressurization system of a 14-story hotel built in Minneapolis, MN.

KEYWORDS building code, high rise building, pressure differential, smoke movement, stack effect, wind effect, modelling

#No3562 Ventilation and airtightness in energy balance analyses

AUTHOR Blomsterberg A

BIBINF in:UK, AIVC, 10th AIVC Conference, held at Espoo, Finland, 25-28 September 1989, Volume 1, February 1990, pp305-324, 4 tabs, 3 refs. #DATE 00:02:1990 in English

ABSTRACT Ventilation in buildings occurs as a consequence of natural air infiltration and through the use of purpose provided ventilation. The air infiltration part of ventilation is often difficult to determine for different boundary conditions. The influence of ventilation on the energy balance of a residential building is therefore usually determined as a remainder together with internal gains from people and the sun or given a constant value. This paper summarizes a report, on one-family houses, on: - the influence of ventilation and airtightness on the energy balance - methods of separating out the ventilation losses from the energy balance - the performance of different ventilation systems. The results are based on performance monitoring and evaluation during two years of four modern one-family houses with different ventilation systems. Two of the houses are equipped with mechanical exhaust-supply ventilation and two with mechanical exhaust ventilation. The ventilation systems were studied during several one-week periods using the constant concentration tracer gas technique. The airtightness of the houses was examined using the fan pressurization technique. The ventilation was predicted with a simplified theoretical one-zone model (the LBL-model) and a multi-zone network model (MOVECOMP). The energy balance was simulated with a dynamic simulation model (STAWAD). The following conclusions are valid for the examined houses. A simplified theoretical one-zone model can be useful and make accurate estimations of the air infiltration in tight houses with mechanical ventilation. This is also a very straightforward kind of model to employ. For less tight houses a multi-zone network model can be useful. There are however two problems with a multi-zone network model; it is time-consuming to put together all the inputs needed and there isn't enough data as to wind pressure and the location of leakage paths available.

KEYWORDS energy balance, mechanical ventilation, constant concentration, fan pressurisation

#No3705 AIM 2: The Alberta air infiltration model.

AUTHOR Walker I S, Wilson D J

BIBINF USA, University of Alberta, Department of Mechanical Engineering. Report 71, January 1990, 40 pp, 8 figs, 7 tabs, 12 refs. #DATE 00:01:1990 in English

ABSTRACT This report presents the relevant equations for a complete single zone air infiltration model (AIM-2), and validates the model by comparing its predictions to measured infiltration rates in test houses. The relation ship for the building envelope is described using a pressure flow law whose coefficients are determined by fan pressurization testing. Unlike other simple models the furnace flue is treated as a separate leakage site. Wind and stack effects are determined separately, then superimposed as a sum of pressures, with a correction term that accounts for the interaction of wind and stack induced pressure. This wind and stack effect interaction term includes the only empirical constant in AIM-2 determined by fitting tomeasured data. The results indicate that treating the furnace flue as a separate leakage site significantly improves model predictions. Because the flue leakage is at a different height for stack effect AIM-2's predictions have about 5% error and the other model errors range from about 20% to 50%. The flue top has its own wind pressure coefficient, and is allowed to have different shelter than the rest of the building. For a sheltered building with a flue AIM-2's error is about 16% with the other models ranging from about 40% to 90%. For an unsheltered building with a flue AIM-2 has an error of about 12% with the other models ranging from about 20% to 26%. These errors are the approximate sum of the bias and scatter in each case. The measurements also show that the orifice flow assumption used in some models is a significant source of error, and the power law pressure-flow relationship, used in AIM-2, is more appropriate as it reduces the scatter error for a housewith no flue from 18% for an orifice flow model to 3% for AIM-2.

KEYWORDS mathematical model, flue

#No3900 Study of the errors occurring in measurement of leakage distribution in buildings by multifan pressurisation.

AUTHOR Furbringer J-M, Roulet C-A

BIBINF in: "Validation", Final report of research programme "Energy aspects of air flow in buildings", LESO-EPFL, Switzerland, April 1990. #DATE 00:04:1990 in English

ABSTRACT The magnitude and the distribution of leakage in buildings is a major parameter in multizone modelling. The multizone pressurization method used to measure the leakiness is a complex method and the study of the confidence limits of the results shows how carefully they should be used in modelling and where effort should be concentrated to enhance the quality of measurements. In this paper the analytical error functions in two multizone pressurization techniques are derived and a sensitive study of the most important parameters is presented and commented. Finally a comparison of the two methods in realistic cases shows their respective properties and also the severe importance of such a study, the error in some cases passing 100%.

KEYWORDS leakage distribution, fan pressurization

#No4868 Using pressurization measurements to predict ventilation performance and heating energy requirements of a large industrial building.

AUTHOR Perera MDAES, Powell G, Walker R R, Jones P J

BIBINF UK, AIVC 11th Conference, "Ventilation System Performance", held 18-21 September 1990, Belgirate, Italy, Proceedings published March 1990, Volume 2, pp 315-338, 7 figs, 4 tabs, 14 refs. #DATE 00:03:1991 in English

ABSTRACT A single whole building pressurisation test using robust and easy to use equipment can, in a very short time, quantify the air-leakiness of the building envelope. However, such measurements do not give a direct measure of the ventilation characteristics of the building which normally requires time-consuming and specialist tracer gas tests. This paper provides a model which makes the link between leakage measurements and ventilation characteristics and applies it to a large, industrial building constructed according to 1979 UK Building Regulations. Air leakage measurements with the building'as found' and then with its loading doors sealed showed a 14% reduction at an inside/outside pressure differential of 25 Pa. Using these leakage characteristics, the model predicted ventilation rates which corresponded well with measured values. Meteorological data at the site for the heating season were combined with the ventilation characteristics of the building (given by the model) to predict the ventilation performance of the building over that period. The results indicated that the building 'as-found' would have, on average, an air change rate of 0.5 h-1 during the heating season. Sealing the loading doors would reduce this rate by 24%, i.e. to 0.38 h-1. This paper shows that space heating energy requirements for the heating season can be assessed using either the combined hourly-predicted ventilation rates and meteorological data forthe site or using the mean predicted ventilation rate with existing design guidance. The two approaches agreed to within 10% of each other. The results also indicated that ventilation heat losses accounted for 44% of the total required energy.Calculations also show that replacing the loading doors with ones which are more air tight and better insulated will reduce by 25% the energy required for ventilation losses and by 5% the losses through the building fabric. This results in an overall reduction of 14% of the total requirement.

KEYWORDS pressurisation, prediction, industrial building

#No4915 Determination of leakages in the building envelope using pressurization test measurements.

AUTHOR Jensen L

BIBINF Air Infiltration Review, Vol 7, No 4, August 1986, pp 6-8, 3 figs, 2 tabs, 1 ref. #DATE 00:08:1986 in English

ABSTRACT There are several methods by which the airtightness of a building can be measured. One method involves the use of a fan to pressurize or depressurize the building. This creates a known pressure difference across the building envelope. Thecorresponding air flow through the fan is measured and this is an indication of the airtightness of the building. This air flow rate can be expressed as the number of building air changes per hour, a useful unit when comparing buildings of different volumes. So far only simple methods have been employed to analyse this condition. However, it is possible to use a morestrict scientific approach based on mathematical models and known parameter identification methods. These techniques are described in this article.

KEYWORDS air leakage, building envelope, pressurisation

#No4926 AC pressurisation model tests.

AUTHOR Sutcliffe H, Waters J R

BIBINF Air Infiltration Review, Vol 9, No 4, August 1988, pp 12-15, 6 figs, 1 tab, 2 refs. #DATE 00:08:1988 in English

ABSTRACT Leakage area measurement by fan pressurisation becomes more difficult as the volume of a building is increased. The equipment becomes bulky, and measurements of air flow through the fan and the resulting pressure differential require more care. AC pressurisation offers an attractive alternative. However, in the case of large industrial buildings, the exterior envelope is often constructed of thin flexible sheet material, and also industrial leakage paths may have a much larger area than is found in, say, typical domestic construction. Thus theinertance effect described by Card et al (1) and the flexing constant described by Sherman (2) may be particularly important. In order to explore these problems, tests are being carried out on a laboratory model. This note reports the results of the first sets of measurements.

KEYWORDS pressurisation, testing chamber

#No5582 Field tests on staircase pressurization system in Hong Kong.

AUTHOR Chow W K, Lam Wai L, Cheung K P, Lam K C

BIBINF USA, Ashrae, Far East Conference on Environmental Quality, held Hong Kong, 5-8 November 1991, pp 27-38, 13 figs, 3 tabs, refs. #DATE 05:11:1991 in English

ABSTRACT This paper reports a series of field tests on the performance of staircase pressurization systems. The differential pressure levels across the doors to the staircase, airflow rate, air temperature, and fan characteristics are measured. A review on the present local fire regulations is also presented. The airflow network program ASCOS was also used to simulate the system. By comparing the measured field test results with those simulated by the computer model, modification to the operation is proposed. Recommendations are made for improving the future design of these smoke control systems.

KEYWORDS stairwell, pressurisation, air flow, temperature, building regulations, smoke control

#No6188 Experimental and numerical analysis of transient air changes in buildings: a case study.

AUTHOR Borchiellini R, Cali M

BIBINF Roomvent '92, Third International Conference, Aalborg, Denmark, September 2-4 1992, Publisher: DANVAK, Lyngby, Denmark, Volume 1, pp 417-434. #DATE 02:09:1992 in English

ABSTRACT Air change rates calculated from the data obtained using tracer gas techniques are usually considered as constant in time, therefore their values represent the average in the time measurements interval. In this paper the measurements performed in two identical detached test houses, using the decay technique, are described. The two houses, which were built by Italian main gas company, are very well equipped with instruments in order to acquire meteorological data and inside air temperatures; pressurization tests were also performed in the past. After a quick glance at the mathematical formulation of the problem using the parameter estimation theory, the concentration measured values are here analysed by considering the air change rates as parameters which change in time. The computed air change or air flow rates are plotted as time functions and are compared with the results obtained by assuming the parameter constant in time; uncertainties due to measurement errors and to calculation procedures are taken into account. Finally it is shown how interesting considerations and information, on the validity of the experiment, can be obtained by the analysis of the results.

KEYWORDS measurement technique, mathematical modelling, test house, tracer gas measurements, air change rate

#No7058 Distributions of expected air infiltration and related energy use in buildings based on statistical methods with independent or correlated parameters.

AUTHOR Nielsen A

BIBINF UK, Air Infiltration and Ventilation Centre, 14th AIVC Conference, "Energy Impact of Ventilation and Air Infiltration", held Copenhagen, Denmark, 21-23 September 1993, proceedings, pp483-492. #DATE 21:09:1993 in English

ABSTRACT The equivalent leakage area algorithm is used to illustrate the use of statistical simulations to predict distributions of infiltration and energy loss for buildings. The important parameters in the model are: leakage at 50Pa pressurisation, indoor and outdoor temperature, leakage in the ceiling and the floor, wind speed, building height and shielding class. Most of these parameters are not known accurately.In the statistical method we assumed for each a distribution based on measurement or good guess. To find the resultant distribution of infiltration we make 1000 simulations with random values from the distributions of the parameters. This has been done with normal, uniform and/or Weibull distributions. We find that the infiltration energy loss for a house in Oslo in average is 7025 kWh/year (case 1) and 10% is above 10500 kWh.year and 10% is below 4200 kWh/year. The results are also given as mean air change for infiltration. Results from five other simulations are described. We normally assume that the parameters are uncorrelated, but it is easy to calculate what will happen, if we have a positive or negative correlation. We found, that in this case made correlation between some parameters practically no difference in the distributions. The simulation method can be used on more complicated and correct models to find out howuncertain knowledge of parameters will influence the finalresults.

KEYWORDS air infiltration, air leakage, simulation, energy losses

#No7173 Performance of attached sunspaces.

AUTHOR Blomsterberg A, Wall M

BIBINF Proceedings of the 3rd Symposium on Building Physics in the Nordic Countries: Building Physics '93 (Bjarne Saxhof, editor), Thermal Insulation Laboratory, Lyngby, Denmark, 1993, vol 1, pp465-473, 6 figs, 4 tabs, refs. #DATE 00:09:1993 in English

ABSTRACT Many modern residential buildings in Sweden are equipped with attached sunspaces. In several cases it has been claimed that important energy savings, due to the sunspace, can be obtained. A sunspace can contribute in two ways to space heating of a building, by preheating the outdoor air and by reducing the thermal losses through the exterior walls. The paper examines the indoor climate and energy balance of sunspaces (balconies) in an apartment building in Stockholm. The constant concentration tracer gas technique was used to monitor the ventilation of the sunspace and the apartment. Fan pressurization was employed to characterize the air leakage. Temperatures in the sunspaces and in the apartments were monitored continuously for a year. A multi-zone network model was used to further evaluate the ventilation. The energy balance was estimated using a dynamic simulation model.

KEYWORDS air flow, calculation techniques, indoor climate, sunspace, passive solar design

#No7749 Bayesian method for estimating airtightness coefficients from pressurization measurements.

AUTHOR Furbringer J-M, Foradini F, Roulet C-A

BIBINF UK, Building and Environment, vol 29, no 2, 1994, pp151-157, 8 figs, 8 refs #DATE 00:00:1994 in English

ABSTRACT A new method for processing pressurization data of building is presented. The inverse problem theory is applied to the estimation of airtightness coefficients. The method, based on the conjunction of theoretical andexperimental information, provides better confidence intervals than a classical least mean square fit methodand allows one to take into account more sources of error. The airtightness coefficients are major parameters for predicting air renewal from weather data and they usually have very large confidence intervals whose reduction merits some numerical efforts.

KEYWORDS Air tightness, pressurization, numerical modelling

#No7756 Sensitivity of models and measurements in the airflow in buildings with the aid of experimental plans. Sensibilite de Modeles et de mesures en aeraulique de batiment a l'aide de plans d'experiences.

AUTHOR Fuerbringer f

BIBINF Switzerland, Lausanne, Ecole Polytechnique Federale de Lausanne, Doctoral Thesis no 1217, 1994, 181 pp #DATE 00:00:1994 in French

ABSTRACT Simulation is proving more and more important in building physics. Programs of different levels of complexity are today available for researchers and designers to model and plan buildings. Natural ventilation is the domain of this dissertation. We have focused our study on the accuracy of the simulation outputs as a function of the accuracy of the input parameters. This is an area of investigation which requires particular attention, so that the simulation outputs can be used with their confidence intervals; without these intervals, the use of the simulation output is risky. The following question has steered our investigation: Is the prediction of detail models more accurate than that of simple models if the accuracy of their respective input parameters is taken into account? There is a risk that inaccurateinput data can invalidate attempts at exact simulation.The answer is that the detailed model for the studied case has larger confidence intervals than the simple models inwind as well as stack dominated situations. The resulthas been obtained by investigation models and measurement processes and determining their confidence intervals. Themeasurements provide the input data of the investigated models. It is then necessary to also investigate the inaccuracy level of these measurement. The measurement analysis was also performed for the more ambitious task of validating calculation programs. The originality of the work lies mainly in the use of fractional factorial design to estimate the partial derivatives of the models by the input parameters with an optimum number of simulations. The random Monte-Carlo method has also been used and both methods were compared. The superiority of the factorial design in the perspective outlined above is illustrated in the dissertation. The measurements analysed more precisely are pressurisation, which provides the air tightness coefficients, and airflow measurements with tracer gas. Concerning the models, thedetailed multizone nodal model COMVEN and 4 simple models BREVENT, LBL, AIDA and TURBUL have been investigated. A 6-zone family house was chosen as case of study because it allowed the comparison of the sensitivity of simple and detailed models.

KEYWORDS modelling, measurement technique, air flow

#No8009 Flow paths in a Swedish single family house - a case study.

AUTHOR Hedin B

BIBINF UK, Air Infiltration and Ventilation Centre, 1994, "The Role of Ventilation", proceedings of 15th AIVC Conference, held Buxton, UK, 27-30 September 1994, Volume 2, pp593-614.

ABSTRACT The ventilation of a Swedish single family house is investigated by means of tracer gas and pressurization techniques. The ventilation flow plays an important role in this house as it enters through a dynamic loft insulation and exits via the crawl space. This design is said to give preheated and clean supply air, warm floors and good energy efficiency. But to meet these promises, it is essential that the air really flows in the intended paths. A single tracer gas technique is used to determine the air flow rates. The measurements show that actually too much of the supply air by-passes the dynamic insulation by direct infiltration. The measurements also detect an unintended flow from the crawl space to the living area. If there exists radon in the ground such a flow must be avoided. Pressurization tests are used to build a pressure drop-flow model. This model describes intended flows, i.e. supply air through dynamic insulation, extract air to crawl space and exhaust air from crawl space to the outside, as well as the unintended flows, i.e. infiltration to living area and the two leakages from outside to crawl space and from crawl space to living area. The model is used to explain the present flows and then to tell how to change them. This is done by simulating the model when one of the parameters (e.g. a size of a leakage) is changing. One conclusion is that the crawl space must be made considerably more airtight.

KEYWORDS (air flow, residential building, tracer gas, pressurization, attic, insulation, crawlspace, air tightness)

#No8212 Relative effectiveness of sub-slab pressurization and depressurization systems for indoor radon mitigation studies with an experimentally verified numerical model.

AUTHOR Gadgil A J, Bonnefous Y C, Fisk W J.

BIBINF Denmark, Indoor Air, No 4, 1994, pp 265-275, 8 figs, 1 tab, refs.

ABSTRACT The performance of sub-slab-ventilation (SSV) systems has been parametrically studied with a numerical model that was earlier compared successfully with experiment (Bonnefous et al., 1992). The model distinguishes between the sub-slab gravel and the underlying soil. It is used to examine system performance for the following system parameters: the permeability of the soil and of the sub-slab gravel, the magnitude of pressurization (or depressurization) applied by the SSV system, and the mode of SSV application (i.e. pressurization (SSP) or depressurization (SSD)). The mechanisms contributing to the successful performance of SSP and SSD systems are identified. For SSD systems, the mechanisms are (1) the inversion of the pressure gradient across the basement slab, and (2) the reduction of the radon concentration in the soil. For SSP systems, the mechanisms are (1) the elimination of convective flow of soil-gas from the soil into the sub-slab gravel by pressurization of the sub-slab region, (2) the reduction of the radon concentration in the soil, and (3) the suppression of diffusion of soil-gas from the soil into the sub-slab gravel by advective flow of air from the gravel bed into the subgravel soil. Numerical modeling demonstrates that placement of a sub-slab gravel layer substantially improves the SSV system performance. Except in the case of highly permeable soils, SSD systems are predicted to perform better than SSP systems. This prediction is consistent with reported field experience. The numerical model is used to elucidate the reasons for this difference in performance.

KEYWORDS radon, modelling, depressurisation

#No8240 Estimation of design ventilation rates for buildings.

AUTHOR Galbraith G H, McLean R C.

BIBINF UK, Building Serv, Eng. Res. Technol; Vol 15, No 4, 1994, pp 199-203, 7 figs, 4 tabs, 10 refs.

ABSTRACT Building fabric heat loads have decreased in recent years as standards of thermal insulation have improved. This in turn has led to an increase in the relative importance of the infiltration component of the total heat loss. The quantification of this component requires the accurate assessment of air infiltration rates under relevant environmental design conditions. Unfortunately, techniques for such assessments are much less well developed than those for calculating fabric heat loss and in many cases building services designers still rely upon the use of empirical estimates which are often unrealistic. This paper presents a case study in which a combined measurement and modelling procedure is applied to provide the designer with a more realistic estimate of air infiltration rates for an existing building. The basis of this work involves the use of the fan pressurisation measurement technique to determine actual leakage characteristics for the building envelope. This information provides real input data for a nodal airflow computer model, the results of which can then be used to estimate appropriate design ventilation rates. The case study involves application of the technique to a large secondary school undergoing refurbishment, and shows clearly that empirical estimates could have led to the installation of a severely undersized heating system. The measurements, in fact, highlighted a problem of excessive infiltration rates which required remedial action. The effectiveness of this remedial action was then confirmed by further measurements and remodelling was carried out to establish the final infiltration rates to be applied by the design engineers.

KEYWORDS building design, ventilation rate

#No8345 Ventilation and airtightness in atria-full-scale measurements and analyses.

AUTHOR Blomsterberg Ake, Wall Maria.

BIBINF Poland, Silesian Technical University, 1994, proceedings of Roomvent '94: Air Distribution in Rooms, Fourth International Conference, held Krakow, Poland, June 15-17, 1994, Volume 2, pp 423-438.

ABSTRACT Many modern office and residential buildings in Sweden include an atrium. The atria are often mechanically ventilated. Very little is known about the ventilation and air infiltration in built atria. The airtightness of the atria are mostly unknown. The airtightness and ventilation have therefore been tested in five different atria. One atrium is surrounded by an apartment building. There is no heating system in this atrium. The other four atria are surrounded by office buildings and are heated during the winter and cooled during the summer. The paper examines the air flows between the atrium and the surrounding building and between the atrium and the outside. The influence of the airtightness on the ventilation of the atrium is also examined. The different principles of ventilation in the examined buildings are discussed. Fan pressurization was employed to characterize the air leakage of the atrium. A multi-zone network model was used to evaluate the air flows. The roof of an atrium can be very leaky and therefore the exfiltration can be large. The walls between the atria and the surrounding buildings can also be very leaky and therefore the uncontrolled air flow through these walls can be large. Many ideas exist as to how to ventilate an atrium and how to couple its ventilation with the surrounding building. The knowledge concerning the real ventilation of atria and the surrounding buildings is insufficient. The size of the air flows between the different zones is of importance to the indoor climate and the energy use.

KEYWORDS atrium, air tightness, mechanical ventilation

#No8421 Experimental evaluation of comis results for ventilation of a detached house

AUTHOR Borchiellini R, Cali M, Torchio M.

BIBINF USA, ASHRAE, 1995, proceedings of ASHRAE Centennial Conference, held 28 January - 1 February 1995, Chicago, USA, 10pp, 12 figs, 2 tabs, refs.

ABSTRACT This paper presents a comparison of measured airflows in a detached house with the results of a simulation model. The house was built mainly for experimental purposes and therefore allows very detailed measurements of the interior and the outside microclimate (e.g., wind velocity, air temperature, humidity, etc.). The air permeability of the house was characterized by means of a pressurization technique. Ventilation measurements were carried out using the tracer gas technique (decay method with two gases, SF6 and N2O). A mobile, multizone, multitracer apparatus, designed and built by the authors, was used. The measured data were analyzed using an inverse problem technique in order to calculate the time histories of the airflow rates during the measurement period and their uncertainties. The building envelope air-leakage coefficients and meteorological data were used in COMIS to obtain the simulated airflow rates. The comparison with measured airflows allows one to define the application limits of the model discussed here.

KEYWORDS detached house, air flow, simulation, tracer gas, building envelope

#No8422 Simulation and measurement of air infiltration and pollutant transport using a passive solar test house

AUTHOR Yoshino H, Yun Z, Kobayashi H, Utsumi Y.

BIBINF USA, ASHRAE, 1995, proceedings of ASHRAE Centennial Conference, held 28 January - 1 February 1995, Chicago, USA, 8pp, 12 figs, 2 tabs, refs.

ABSTRACT This paper describes the measured and calculated results of air infiltration and decay profiles of tracer gas in a passive solar test house used to evaluate the simulation model COMIS for multizone air infiltration and pollutant transport. The interior leakage and exterior windows and wall leakage were measured by the fan pressurization method. Air infiltration was measured in three rooms under different conditions. The concentration decay method using three gases, N2O, SF6, and CHCI2F, was employed to find the air exchange rates and investigate indoor pollutant transport. The data, such as gas concentrations, temperatures, and wind, were measured in situ. In addition, the data from the measurements were used as simulation input data for air infiltration and pollutant concentrations, assuming tracer gases as the pollutant. The results of comparisons between measurement and simulation values of air exchange rates and tracer gas concentrations using the COMIS model are reasonable

KEYWORDS simulation, air infiltration, pollutant, passive solar house

#No8634 Dynamics of laboratory pressurization.

AUTHOR Ahmed O, Mitchell J W, Klein S A

BIBINF USA, ASHRAE Transactions, Vol 100, Part 2, 1994, pp 223-229.

ABSTRACT Laboratories are depressurized with respect to a reference space in order to contain the lab contaminants. Conversely, pressurization of a laboratory prevents flow of outside foreign particles and keeps the lab space clean. The lab pressure is controlled by maintaining either a pressure differential across the lab envelope or a differential flow rate between the total lab exhaust and supply flows. The current design process for pressure control does not apply the knowledge of space pressurization dynamics, which is critical for a variable-air-volume (VAV) lab. This paper presents a simple model for analyzing the transient response of space pressure. The simulated results show the importance of physical variables such as air changes per hour (ach) and the leakage characteristics of the envelope on the pressure dynamics. The other findings include influence of supply flow rate response characteristics on the pressure control performance and the significance of solving mass and energy equations to select the differential flow and pressure setpoints.

KEYWORDS laboratory, depressurisation, pollutant

#No8787 Air pressure control of latest leakage

AUTHOR Stewart W E, Saunders C K, Stickler L A.

BIBINF USA, Ashrae Journal, May 1995, pp 40-47, 3 figs, 1 tab, 14 refs.

ABSTRACT Describes how a computer program was developed that models the interaction of water vapour transmission and air pressure in building walls. The investigation reported in this article obtained some experimental data for air pressurization to prevent moisture transfer, through porous building wall materials.

KEYWORDS air leakage, pressurization

#No9060 Pressure simulation program.

AUTHOR Knoll B, Phaff J C, de Gids W F

BIBINF UK, Air Infiltration and Ventilation Centre, 16th AIVC Conference Implementing the results of ventilation research , held Palm Springs, USA, 18 - 22 September, 1995, Proceedings Volume 1, pp 233-242.

ABSTRACT A computer program has been developed to predict the wind pressure coefficients Cp on facades and roofs of block shaped buildings. The program is based on fits of measured data, including wind shielding by obstacles and terrain roughness. Main advantages of the program are: * It needs no expertise of its users on wind pressures; * input is simple. It exists of building and obstacles co-ordinates and orientations; * generating Cp values for ventilation model calculations needs no separate action. By linking the pressure simulation program and the ventilation calculation program as well as their input, wider application of ventilation programs for non-experts becomes possible. The accuracy of the predicted wind pressures in the first version of the pressure simulation program are promising. Especially complex building shapes and surroundings have to be dealt with more carefully, as well as increasing wind velocities in small passages. Also detailed improvements are necessary, e.g. to account for sloped roofs and the position of ventilation provisions above roof level. Therefore, generation and implementation of additional wind tunnel data is planned, to improve the present version.

KEYWORDS simulation, pressurization, wind pressure, wind barrier

#No9592 A sensitive method for prediction of air flow rate in buildings from energy and environmental point of view.

AUTHOR Nantka M B

BIBINF Healthy Buildings 95, edited by M Maroni, proceedings of a conference held Milan, Italy, 10-14 September 1995, pp 1609-1614, 4 figs, 4 refs.

ABSTRACT The loads of building deciding of the air flows and change are of different character and mostly depend on stack and wind effect. The main ways to gain information about air change rate are measurements and computer simulations based on various building models. Measurement method (tracer gas and pressurization tests) cannot be applied in simultaneous of vast inner areas characteristic of multizone structures. Therefore, analytical methods based on mathematical models of buildings and processes taking place in them are most frequently used. These models divide the building into a given number of zones (spaces) mutually combined. In most cases, the division of a building usually consists in separation of buildings with natural ventilation and where wind effect is predominant. However, the results of the calculation do not conform to the results of measurements made in selected spaces of existing buildings. On the basis of such comparisons it has been assumed that the air flow and change rate taken as average for a flat is rarely representative of each of rooms located in this flat. This conclusion has become the basic reason to make an attempt of creating a new method of air flow prediction.

KEYWORDS air flow, stack effect, wind effect

#No9623 Modelling the influence of building and HVAC system parameters on radon levels in a large building.

AUTHOR Gu L, Swami M V, Anello M T

BIBINF USA, Ashrae Transactions, Vol 102, Pt 2, 1996, [preprint], 12 figs, 1 tab, refs.

ABSTRACT Heating, ventilating, and air-conditioning (HVAC) operation can play a crucial role in controlling indoor radon concentrations. Both the introduction of fresh air and the pressurization of an indoor radon concentration levels. Using an in-house computer model, this paper examines the impact of configurational and operational parameters of a building and HVAC system on indoor radon concentrations in a large building. To achieve this, a three-phase approach was followed. Based on the results of the parametric analysis, inferences are drawn about the influence of the parameters on indoor radon concentrations and the efficacy of radon mitigation strategies is examined. Results indicate that building ventilation rate and the OA/EA ratio are significant parameters that affect indoor radon concentration.

KEYWORDS radon, large building, modelling

#No9679 Optimal control of duct pressure in HVAC systems.

AUTHOR Li H, Ganesh C, Munoz D R

BIBINF USA, Ashrae Transactions, Vol 102, Pt 2, 1996, [preprint], 8 figs, refs.

ABSTRACT The energy cost of monitoring and controlling a building environment is a serious consideration for the heating, ventilating, and air-conditions (HVAC) engineering industry. This work is focused on minimizing the energy cost associated with the control of variable-air volume (VAV) systems. All the experimental work was performed using a low-speed wind tunnel. The authors modified a low-speed wind tunnel to simulate a single VAV system. We also developed a dynamic model of the system and analyzed its energy consumption characteristics. Conventional proportional and integral (PI) control, adaptive control and optimal control algorithms were developed and applied to the duct pressure control loop within the VAV system. A comparison of the performance of these control algorithms indicates that an optimal control strategy can save up to 30% of the energy consumed in a system that employs a conventional PI control scheme.

KEYWORDS pressurisation, duct, air conditioning

#No9697 Scale modelling of the pressure drop in a stairshaft.

AUTHOR Wong Y W, Chan W K

BIBINF USA, Ashrae Transactions, Vol 102, Pt 2, 1996, [preprint], 7 figs, 1 tab, refs.

ABSTRACT This paper presents results of a study of the pressure drop in a scale model of a stairshaft with closed treads. A 1:10 scale model of a 10 story stairshaft was build to study airflow resistance within the shaft under isothermal conditions, including the effect of occupant density. Three cases were investigated: a stairshaft with no occupant, a shaft with medium density, and one with high-density occupancy. In addition, the effects of the distribution of occupants in the stairshaft were studied. The pressure drop through the model stairshaft was measured at each story for a range of volume flow rates between 0.0368 and 0.0901m3/s (1.29 and 3.18 ft3/s) introduced at a single injection point at the top of the stairshaft. The pressure loss coefficient for the scale model with no occupants was found to be approximately 33.2. The results obtained are comparable to published measurements made in full-scale stairshafts with typical floor heights between 3.2m and 3.85m. The pressure drop varies linearly with the height of the stairshaft and varies directly with the square of the supply air rates. Results from the test demonstrate the same trend as reported in the literature - that the pressure loss coefficient is a function of the occupant density in the stairshaft. The loss coefficient increased by a factor of approximately two when the model was populated to simulate occupancy at medium occupant density and by a factor of three at high occupant density when compared to that of the empty stairshaft. The pressure loss coefficients for the scale model at medium and high occupant densities were found to be approximately 65.7 and 95.9 respectively. The results also agree with published results that the distribution of occupants, whether on the landings at each story or between floors, has little effect on the loss coefficients for medium- and high-density occupancy.

KEYWORDS stair pressurisation, modelling, air flow, occupancy effects

#No9736 Measuring technique of leakage area of houses by AC-pressurisation method.

AUTHOR Utsumi Y, Kobayashi H, Kadoya T, Yoshino H

BIBINF Japan, proceedings of the 5th International Conference on Air Distribution in Rooms, Roomvent '96, held Yokohama, Japan, 17-19 July, 1996, Volume 1, pp 29-34.

ABSTRACT This research is aimed to develop the leakage measuring technique by AC-pressurization method (AC-Press), which applies the sinusoidal volume changing to the building to be tested. This paper describes the principles and the characteristics including the comparison of the DC-pressurization method (DC-press), that is, AC-Press has less impact to indoor environment during the measurement, and is not necessarily penetrating the envelop with a duct for the testing. Also instrumentation of this method is indicated and the laboratory experiment using scale model with four holes is executed. Effective Leakage Area (ELA) of the holes were measured by DC-Press. The results show that reproducibility is confirmed and that the difference of ELA between AC-Press and DC-Press varies from -2.2% to -7.7%. Furthermore the effect of the flow exponent and phase lag between room volume change and pressure change upon the estimated ELA is discussed.

KEYWORDS measurement technique, air leakage, pressurisation

#No9943 AC pressurisation: Fourier analysis and the effect of compressibility of air.

Dewsbury J

UK, Building Serv Eng Res Technol, Vol 17, No 2, 1996, pp 73-77, 4 figs, 3 tabs, 10 refs.

The AC pressurisation method of measuring the airtightness of building is briefly described. Using a simplified model, the leakage characteristics of the enclosure may be found by Fourier analysis of the pressure signal if the effects of compressibility and flexing are neglected. These effects become small at low frequency, but the frequency required to make them negligible may be too low for the available instruments and the resulting pressure signal may be smaller than appropriate for building airtightness measurements. The conditions under which the other approximations in the model may be justified are not yet know.

pressurisation, modelling, air leakage

#No10105 Air leakage in the perspective of international standards.

Levin P A, Wilson D J, Ackerman M Y

in: Airflow performance of building envelopes, components and systems, USA, ASTM 1995, papers presented at a symposium held in Dallas, Texas, 10-11 October 1993, pp 231-247.

There exist a number of national standards and a draft international standard for the fan pressurization method for measuring air leakage. Although the standardized methods in principle are the same, the way of interpreting and presenting the results is different. In previous studies, houses that have a relatively large leakage area at a low pressure difference (4 to 10 Pa) can still seem comparatively airtight at a high pressure difference (50 Pa). This face is a consequence of differences in the flow exponent in the power-law equation, which is the normal equation used to fit to the data points, and can be a source of error when trying to compare the relative airtightness of houses. Extrapolating results from high pressure differences to low pressures, which are out of the measured range, can thus result in substantial errors. Air leakage testing of windows normally starts at 50 Pa which should be accounted for when trying to use these results as inputs in network air infiltration models. Measurement results on low pressure air leakage are discussed in the paper and compared with high pressure air leakage. Pressurization test date from 105 tests in one house at the Alberta Home Heating Research Facility are used for the study. The tests were made automatically over a seven-month period in low wind conditions. A wide range of pressure differences were tested and the results cover the test specifications for most standards. In addition to comparing standards, these tests were used to measure seasonal effects on air leakage in a wood-frame house with a plastic film air/vapor barrier. The results show some significant differences between the standards, and also a variation with month of test, indicating a seasonal variation in air leakage.

air leakage, measurement technique, fan, pressurisation, standard, wood frame, pressure difference

#No10107 Uncertainties in fan pressurization measurements.

Sherman M, Palmiter L

in: Airflow performance of building envelopes, components and systems, USA, ASTM 1995, papers presented at a symposium held in Dallas, Texas, 10-11 October 1993, pp 266-283.

The ASTM Method for Determining Air Leakage Rates by Fan Pressurization Test (E 799-87) measures the airtightness of building envelopes using fan pressurization. Uncertainty is introduced in the process from the uncertainty of the airflow and pressure measurements as well as from nonlinearities in the system to be measured. This paper analyses the precision and bias associated with making a measurement using E 779 in typical field situations. Model specification (or modelization) errors may also contribute significantly to the overall uncertainty in the estimates of the 4 Pa leakage; the sources and sizes of these modelization errors interact with the instrumentation errors in making a fan pressurization test. Insufficient field date exist to fully include the effects of modelization and other low-pressure phenomena, but the current standard can nevertheless be improved by tightening the instrumentations and procedural specifications and by judicious choice of pressure measurement stations.

building envelope, air leakage, air flow

#No10111 Basic air infiltration.

Lyberg M D

UK, Building and Environment, Vol 32, No 2, 1997, pp 95-100, 2 figs, 10 refs.

Some fundamental properties of building air infiltration are derived starting from propositions stressing the underlying assumptions. Possible structures of air infiltration models relating the flow to a leakage area are considered. Approximate expressions are derived for the value of the reference pressure necessary for mass conservation to hold. These results are applied to the case of enforced building pressurization. It is demonstrated that some currently used models of air infiltration violate mass conservation. Other models are shown to lead to unnecessarily large errors when applied to pressurization

air infiltration, modelling, pressurisation

#No10120 A comprehensive validation of two airflow models - COMIS and CONTAM.

Haghighat F, Megri A C

Indoor Air, No 6, 1996, pp 278-288, 12 figs, 10 tabs, refs.

Several airflow and contaminant dispersion models have been developed to study air distribution in buildings. This paper reports the results of a comprehensive validation of two models: COMIS and CONTAM. The validation process was carried out at three different levels: inter-program comparison; validation with experimental data which was collected in a controlled environment; and finally, validation with field measurement data. At the inter-program level, the airflow rates and pressure values predicted by COMIS and CONTAM for a four-zone paper building were compared with the airflow rates and pressures predicted by CBSAIR, AIRNET and BUS. The results show good agreement between these software programs. The second level of validation compares the models' predictions with measured data collected in a controlled environment. Fan pressurisation, smoke and tracer gas tests were conducted to estimate the permeability of building envelope components, to locate cracks, and to determine the interzonal airflow rates between rooms. The results confirm that there is good agreement between predictions made by COMIS and CONTAM; there are, however, some differences between these models' predictions and the measured date. The predictions made by these models were also compared with the results of a tracer gas measurement carried out in a residential building. The predicted and measured values were in good agreement.

air flow, modelling

#No11285 The verification of radon protective measures by means of a computer model.

Jiranek M, Svoboda Z

International Building Performance Simulation Association (IBSPA), 1997, proceedings of "Building Simulation '97", the Fifth International IBSPA Conference, held September 8-10, 1997, in Prague, Czech Republic, Volume II, pp 165-171, 6 figs, 1 tab, refs.

The numerical model for verification of various radon protective measures has been developed. This model is based on the partial differential equation for the two-dimensional steady-state radon transport caused by diffusion and convection. The finite element method was used to obtain the numerical solution of the governing equation. The general finite element formulation was derived by means of the Petrov-Galerkin method with weighting functions different from interpolation functions. The performance of soil ventilation systems has been studied with this model. The results of simulation demonstrate that the soil depressurization systems are effective in the majority of cases while the soil pressurization systems only in case of permeable soils.

numerical modelling, radon

#No11366 A study of the rainscreen concept applied to cladding systems on wood frame walls.

Morrison Hershfield Ltd

Canada Mortgage and Housing Corporation, August 1990.

Investigates the performance of the Rainscreen Principle applied to residential claddings on wood frame construction. The study included a full scale simulation, in the laboratory, of the rain penetration control performance of three cladding types with each having a sealed and leaky air barrier system. The study also undertook an examination of the pressure equalisation performance of one of the cladding systems on a construction model placed in a boundary layer wind tunnel. In addition a simple mathematical model was developed that simulates the pressure equalisation performance of a rainscreen wall. It was designed to predict the cavity pressure and time response of the cavity for various gust load rates and magnitudes. The laboratory investigations of the test walls have shown that the pressure equalisation phenomenon reduces the amount of water that penetrates the cladding system. To achieve rain penetration control, it was found that the rainscreen wall is dependent on certain design and construction features, including an effective air barrier system within the wall, sufficiently rigid components, the air barrier system in particular, adequate venting and drainage of the cladding system, and effective compartment seals located at corners.

wood frame wall, pressurisation, simulation, rain

#No11618 Evaluation of the COMIS model by comparing simulation and measurement of airflow and pollutant concentration.

Zhao Y, Yoshino H, Okuyama H

Indoor Air, No 8, 1998, pp 123-130, 9 figs, 2 tabs, 1 ref.

This paper describes the measured and calculated results of airflow rates and pollutant concentration profiles in an airtight test house, the aim being to evaluate the calculation model COMIS for multizone air infiltration and pollutant transport. Firstly, the leakage areas of internal doors, exterior walls and windows were measured by the fan pressurisation method. Secondly, two measurements were carried out, assuming that the test house consisted of ten zones. The concentrations and injection rate of SF6 were measured in order to determine the airflow rates by a system identification method. The boundary conditions, such as indoor and outdoor temperatures, wind speed and direction, and wind pressures were also recorded in situ and saved simultaneously on diskettes, using a computerised data acquisition system. Thirdly, the measured boundary data and leakage characteristics were used as input in the simulation of airflow using COMIS; initial concentrations, injection rate, along with the previous data were used for simulating pollutant transport, assuming tracer gas SF6 as a pollutant. Lastly, the comparisons between measurement and simulation results of airflow rates and pollutant concentrations were carried out by linear regression analysis. The correlation coefficient between the measured and calculated air change rates was 0.72, and that for pollutant concentration was 0.94.

air change rate, pollutant concentration

#No11782 Building ventilation: a pressure airflow model computer generation and elements of validation.

Boyer H, Lauret A P, Adelard L, Mara T A

UK, Energy and Buildings, No 29, 1999, pp 283-292, 13 figs, 45 refs.

The calculation of airflows is of great importance for detailed building thermal simulation computer codes, these airflows most frequently constituting an important thermal coupling between the building and the outside on one hand, and the different thermal zones on the other. The driving effects of air movement, which are the wind and the thermal buoyancy, are briefly outlined and we look closely at their coupling in the case of buildings, by exploring the difficulties associated with large openings. Some numerical problems tied to the resolving of the non-linear system established are also covered. Part of a detailed simulation software (CODYRUN), the numerical implementation of this airflow model is explained, insisting on data organization and processing allowing the calculation of the airflows. Comparisons are then made between the model results and in one hand analytical expressions and in another and experimental measurements in case of a collective dwelling.

modelling, pressurisation, air flow, calculation techniques

#No11792 Impact of combined dilution and pressurisation effects of ventilation air on indoor contaminant concentration.

Budaiwi I M

Switzerland, Indoor and Built Environment, No 7, 1998, pp 289-299, 8 figs, 26 refs.

When outdoor air is the main source of pollutants indoors, mechanical air ventilation can be viewed as having two fronts of action in controlling indoor air quality. The first is its capacity to remove indoor air pollutants by dilution, and the second is its capability to prevent, through its pressurisation effect, the pollutant source (i.e. untreated outdoor air) from infiltrating, through the building envelope, to the occupied space. This paper discusses the impact of combined dilution and pressurisation potentials of ventilation air on indoor contaminant concentration when outdoor air is the main source of pollutants. Utilising an airflow model in conjunction with a one-compartment indoor air quality model, contaminant concentration behaviour within a single zone enclosure is predicted at various enclosure air leakage, system characteristics and pressurisation levels. Results from this study are indicative of the appreciable impact of the pressurisation effect of ventilation air which needs to be considered for a better assessment of ventilation air effectiveness and further enhancement of indoor air quality control.

indoor air quality, pressurisation

#No11923 Comparison of residential air infiltration rates predicted by single-zone and multizone models.

Musser A, Yuill G K

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 8 pp, 2 figs, 5 tabs, refs.

Residential air infiltration rates predicted by a detailed multizone computational model are compared with those predicted by a single-zone model. The multizone model is created using the public domain program CONTAM96, which allows the user to break the house into a number of zones connected to one another and the outdoors by leakage paths and user-defined characteristics. Actual floor plans for a ranch-style house and typical published leakage characteristics of residential building components are used to construct a very detailed model with roughly 2,000 zones and 7,000 leakage paths. The leakage path configuration of this multizone model is then validated by performing fan pressurization tests on two houses constructed according to the floor plan used to develop the computational model. At pressure differences typical of infiltration conditions, the leakage of the multizone model is in between that of the two identical houses. Infiltration rates computed by the multizone model for representative outdoor temperatures and wind speeds are then compared to those predicted by the single-zone LBL model. Four ventilation systems are modeled: no mechanical ventilation or exhaust, supply fan only, exhaust fan only, and balanced supply and exhaust fans. Comparisons are initially made based on the single-zone model predictions using typical assumptions,. The multizone computational model is then used to calculate more precise wind parameters and building leakage characteristics for use in the single-zone model, and the resulting infiltration is again compared with that predicted by the multizone model. These comparisons show that the predictions of both models are sensitive to the choice of wind-related parameters and that the assumption that leakage is evenly distributed throughout the building envelope has little effect on the predictions of the single-zone model. The predictions of the single-zone model most closely match those of the multizone model when flows are added using a quadrature method that takes into account the flow exponent obtained using the multizone model.