scholarly journals A Discussion Regarding the Measurement of Ventilation Rates Using Tracer Gas and Decay Technique

2020 ◽  
Vol 5 (10) ◽  
pp. 85
Author(s):  
Ricardo M. S. F. Almeida ◽  
Eva Barreira ◽  
Pedro Moreira
Keyword(s):  
Cross Contamination ◽  
Single Family ◽  
Outdoor Temperature ◽  
Time Dependency ◽  
Tracer Gas ◽  
Large Variability ◽  
Change Rate ◽  
Air Change Rate ◽  
Ventilation Rates

The measurement of ventilation rates is crucial in understanding buildings’ performances, but can be a rather complex task due to the time-dependency of wind and buoyancy forces, which are responsible for the pressure differences that induce air movement across the envelope. Thus, assessing air change rate through one-time measurements during brief periods of time may not be a reliable indicator. In this paper, the variability in the measurement of ventilation rates using the decay technique was evaluated. To that end, two compartments of a typical single-family detached dwelling were selected as a case study and 132 tests were performed, considering two different boundary conditions (door closed and door open). This work allowed the large variability of the results to be highlighted, as the coefficient of variation ranged from 20% to 64%. Wind speed had a key effect on the results, especially because during the measurements indoor–outdoor temperature differences were not so significant. The possibility of using occupant-generated carbon dioxide as tracer gas was also analyzed, but problems of cross-contamination were identified.

scholarly journals Danish Dwellings with Cold Attics—Ventilation Rates and Air Exchange between Attic and Dwelling

Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 64
Author(s):  
Tessa Kvist Hansen
Keyword(s):  
Mould Growth ◽  
Single Family ◽  
Tracer Gas ◽  
Change Rate ◽  
Air Change Rate ◽  
Humidity Measurements ◽  
Excess Moisture ◽  
Ventilation Rates ◽  
And Diffusion ◽  
Air Exchange

Naturally ventilated cold attics are traditional in many Danish single-family homes. The moisture balance of these attics is dependent on sufficient ventilation for removal of excess moisture. Moisture is generated in the dwelling below, and transported to attic spaces through convection and diffusion. Therefore, airtight ceilings are vital for reduction of excess moisture, which may yield mould growth in the attic. If mould spores migrate to the dwelling it can cause risk of health concerns for occupants. The presents study includes analysis of tracer gas and temperature/relative humidity measurements, in 30 dwellings/attics. The measurements yielded results of both air change rates in attics and dwellings, as well as air exchange between the two zones. Four of 30 houses, met the recommended air change rate of 0.5 h−1, and only in summer. The air change rate in the attics was found to be higher, and with larger variation compared to the dwelling. Visible mould growth was found in three attics, which all exhibited low air change rates. Air exchange between zones occurred in houses both with and without vapour barriers. The downward air exchange in summer, was however slightly larger in cases without vapour barriers. These results highlight the importance of airtight ceilings for both dwelling and attic performance.

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

2016 ◽  
Vol 26 (4) ◽  
pp. 502-513 ◽  
Author(s):  
David Johnston ◽  
Anne Stafford
Keyword(s):  
Preliminary Investigation ◽  
The Other ◽  
Tracer Gas ◽  
Related Factors ◽  
Change Rate ◽  
Rule Of Thumb ◽  
Air Change Rate ◽  
Ventilation Strategies ◽  
The Uk ◽  
Ventilation Rates

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 CO2 emissions, 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.

Improving the air change rate in high-rise buildings through a transom ventilation panel: A case study

2019 ◽  
Vol 147 ◽  
pp. 35-49 ◽  
Author(s):  
Ardalan Aflaki ◽  
Kamran Hirbodi ◽  
Norhayati Mahyuddin ◽  
Mahmood Yaghoubi ◽  
Masoud Esfandiari
Keyword(s):  
Change Rate ◽  
High Rise ◽  
Air Change Rate

scholarly journals Airflow as a Possible Transmission Route of Middle East Respiratory Syndrome at an Initial Outbreak Hospital in Korea

2018 ◽  
Vol 15 (12) ◽  
pp. 2757 ◽  
Author(s):  
Minki Sung ◽  
Seongmin Jo ◽  
Sang-Eun Lee ◽  
Moran Ki ◽  
Bo Choi ◽  
...  
Keyword(s):  
Middle East ◽  
Infected Patient ◽  
Close Contact ◽  
Middle East Respiratory Syndrome ◽  
High Concentration ◽  
Tracer Gas ◽  
Long Distance ◽  
Indoor Airflow ◽  
Change Rate ◽  
Air Change Rate

In this study, the results of an airflow investigation conducted on 7 June 2015 as part of a series of epidemiologic investigations at Pyeongtaek St. Mary’s Hospital, South Korea, were investigated. The study involved 38 individuals who were infected directly and indirectly with Middle East Respiratory Syndrome (MERS), by a super-spreader patient. Tracer gas experiments conducted on the eighth floor, where the initial patient was hospitalized, confirmed that the tracer gas spread to adjacent patient rooms and rooms across corridors. In particular, the experiment with an external wind direction and speed similar to those during the hospitalization of the initial patient revealed that the air change rate was 17–20 air changes per hour (ACH), with air introduced through the window in the room of the infected patient (room 8104). The tracer gas concentration of room 8110, which was the farthest room, was 7.56% of room 8104, indicating that a high concentration of gas has spread from room 8104 to rooms across the corridor. In contrast, the tracer gas was barely detected in a maternity ward to the south of room 8104, where there was no secondary infected patient. Moreover, MERS is known to spread mainly by droplets through close contact, but long-distance dispersion is probable in certain environments, such as that of a super-spreader patient hospitalized in a room without ventilation, hospitals with a central corridor type, and indoor airflow dispersion due to external wind.

Indoor hygrothermal loads for the deterministic and stochastic design of the building envelope for dwellings in cold climates

2017 ◽  
Vol 41 (6) ◽  
pp. 547-577 ◽  
Author(s):  
Simo Ilomets ◽  
Targo Kalamees ◽  
Juha Vinha
Keyword(s):  
Field Measurements ◽  
Heating System ◽  
Building Envelope ◽  
Cold Climates ◽  
Outdoor Temperature ◽  
Change Rate ◽  
Levels Of Detail ◽  
Air Change Rate ◽  
Excess Value ◽  
Occupancy Rates

In this study, several years of field measurements of indoor hygrothermal loads in 237 dwelling units are analysed. Moisture excess is calculated from hourly values of temperature, and relative humidity measured both indoors and outdoors. Air change rate and moisture production in bedrooms are calculated on the basis of carbon dioxide measurements. It is found that indoor temperature profiles differ depending on whether a building has central heating, a stove or combined heating system. The determined average moisture excess value, 2.8 g/m3 with a standard deviation of 1.6 g/m3 for cold periods, can be used in stochastic calculations. Critical values for moisture excess at the 90th percentile, ranging from 3–8 g/m3, depending upon occupancy rates, can be used in the deterministic analysis. Averages and weekly maxima of moisture excess in the study are reported at different percentiles. Considerable deviations from the EN ISO 13788 standard are discovered, concerning the breaking point depending on outdoor temperature and moisture excess during the summer. The average and critical moisture production in bedroom is presented and insufficient ventilation determined based on measurements. During the heating period, the air change rate is relatively stable while moisture production levels increase along with the dropping outdoor temperature. Two indoor temperatures and three humidity models with different levels of detail and influencing factors are proposed. Temperature and humidity loads derived using the proposed models can be used to determine the indoor hygrothermal boundary conditions for the building envelope of dwellings in cold climates.

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