Moisture Buffering in Surface Materials Due to Simultaneous Varying Relative Humidity and Temperatures: Experimental Validation of New Analytical Formulas
Round 1
Reviewer 1 Report
In general, excellent work. Below a few comments/questions
- Please proofread the document; there are several typos throughout the document (e.g. end of the second paragraph on page 2 should say analysis).
- Was there any preconditioning (RH and temp) of the samples; before exposing them to the triangular and sinusoidal variations?
- As per figures 1 and 2, no all the variations started in 54% RH.
- please provide details of the environmental chamber used (e.g. small movable chamber, walk-in chamber, other)
- could you provide a schematic of the samples inside the climatic chamber
- Were the samples exposed to the conditions provided by the climatic chamber equally on each side? In the first paragraph of page 7, you said that temperature was assumed to be the same in the interior as the surface... please explain.
Author Response
1. Reviewer
Please proofread the document; there are several typos throughout the document (e.g. end of the second paragraph on page 2 should say analysis).
Response
Thank you. We have double checked and corrected the spelling mistakes
2. Reviewer
Was there any preconditioning (RH and temp) of the samples; before exposing them to the triangular and sinusoidal variations?
Response
The samples were preconditioned for 24h before each test, which was enough for the specific materials we used to reach the balance after each test (the change in weight was monitored live). Before the beginning of the experimental session, samples were stored in a environmental room with similar environmental condition of the test (60% and 22 Degrees), which made the pre-conditioning process before testing feasible in 24h.
Page 2 (materials): Materials were stored in an environmental room at 60\%RH and $22^oC$.
Page 3 (Experimental design): The materials were exposed before each tests to 24h pre-conditioning at 23oC and 54%RH and six cyclic humidity and temperature variations at an air speed of 0.1 m/s.
3. Reviewer
As per figures 1 and 2, no all the variations started in 54% RH.
Response
Thank you to point it out. Figures have been corrected
4. Reviewer
please provide details of the environmental chamber used (e.g. small movable chamber, walk-in chamber, other)
could you provide a schematic of the samples inside the climatic chamber
Response
The model of the climatic chamber was addressed in the paper and a picture of the set up is show (Figure 1)
Page3 (method): Specimens were tested in an environmental chamber (ACS Compact Test Chambers DY110), into which a mass balance were placed to continuously measure the change in weight, as shown in figure 1. More details of the set-up can be seen in Cascione et al 2020
5. Reviewer
Were the samples exposed to the conditions provided by the climatic chamber equally on each side?
Response
The sentence was not clear, but we used Two sensors that were placed within the net that surrounds each scale (figure 1) above the specimens (one tiny tag for each material). The comparison of the sensors gave a good match
Page six (last paragraph): A temperature and RH sensor for each specimen (Tiny Tag TV 4505) monitored the climate condition in the climatic chamber to observe the agreement between the target fluctuations and the actual measurements on both sides of the chamber
6. Reviewer
In the first paragraph of page 7, you said that temperature was assumed to be the same in the interior as the surface... please explain.
Response
We assumed that the temperature the material’s surface follows the same variations as the room temperature. We assume there is no delay or lowering of the temperature fluctuation on the material’s surface.
Page 7 (1st paragraph): The analysis in this paper assumed that the temperature of the surface material always followed the chamber temperature without any delay
Reviewer 2 Report
Despite the extensive literature on research into the moisture buffering phenomenon, I read the article with interest. More consistent experimental and numerical methodologies are still needed to deepen the common understanding of moisture buffering and its impact on energy consumption and environmental quality in residential and commercial buildings, and quantify these benefits accurately. The model proposed in the article meets this demand. I would just like to suggest some minor changes:
- Please include more references for the current journal, where you plan to publish.
- There are abundant of literature in moisture buffering models. One example is ” K. Zu; M. Qin; Rode; M. Libralato “Development of a moisture buffer value model (MBM) for indoor moisture prediction” There are more such studies. Please refer to this literature in your Introduction section.
- How important is it, to introduce internal temperature variability to the model, did the authors compare these changes to the model in which a constant temperature was assumed ?
- Line 136. Whether the assumption that the hysteresis is ignored will not affect the desorption process?
- Figure 5. The description under the picture needs to be corrected
- Line 211- 213 Please explain what could be the reason for this?
- Line 262 - The wrong equation number is given
- Line 265-266 To get the complete picture it would be adequate to add the value of the penetration depth value for the same time periods for clay and gypsum too.
- Figure 7 and 8. Please add a description of the curves, the figures will be easier to read
Author Response
1. Reviewer
Please include more references for the current journal, where you plan to publish.
There are abundant of literature in moisture buffering models. One example is ” K. Zu; M. Qin; Rode; M. Libralato “Development of a moisture buffer value model (MBM) for indoor moisture prediction” There are more such studies. Please refer to this literature in your Introduction section.
Response:
Thank you, the citations were modified accordingly
13 Kaczorek, D. Moisture buffering of multilayer internal wall assemblies at the micro scale: Experimental398study and numerical modelling.Applied Sciences2019,9, 3438. doi:10.3390/app9163438.399
16.Zu, K.; Qin, M.; Rode, C.; Libralato, M. Development of a moisture buffer value model405(MBM) for indoor moisture prediction.Applied Thermal Engineering2020,171, 115096.406doi:10.1016/j.applthermaleng.2020.115096.407
17.Xie, H.; Gong, G.; Wu, Y.; Liu, Y.; Wang, Y. Research on the hygroscopicity of a composite hygroscopic408material and its influence on indoor thermal and humidity environment.Applied Sciences2018,8, 430.409doi:10.3390/app8030430.
2. Reviewer
How important is it, to introduce internal temperature variability to the model, did the authors compare these changes to the model in which a constant temperature was assumed ?
Response:
With internal temperature we meant room temperature. This was better clarified in the paper
Page 7 (1st paragraph): The analysis in this paper assumed that the temperature of the surface material always followed the chamber temperature without any delay
Moreover, the assumption that the surface temperature follows the room temperature can be further justified by the results of the simulation model. To better explain we better explain in the paper:
Page 17 (4.2.2 section): The time delay for the change in temperature in the boards due to a room temperature change is around 1200 s for the 20 mm thick gypsum board and 1600s for the 40 mm thick clay board. This is roughly 1/3 of an hour. For diurnal variations the ratio between this time delay and the time period is of the order 10^-2. For the six days period the ratio is almost one order less and can further justify the approximation.
The comparison of the response of material at constant and variable temperature is experimentally shown in the paper Cascione, V.; Maskell, D.; Shea, A.; Walker, P.; Mani, M. The moisture buffering performance of plasters when exposed to simultaneous sinusoidal temperature and RH variations.Journal of Building Engineering that will be shortly published
Page 21: Overall, it can be stated that either in the experimental and simulations temperature is a significant factor that delays the response of materials to buffer humidity. This is further justified in Cascione et al in which the response of materials to constant and variable temperature were compared, showing that variable temperatures generate a significant lag compared to the case at constant temperature.
3. Reviewer
Line 123. Whether the assumption that the hysteresis is ignored will not affect the desorption process?
Page 2 (3.2.2) This is justified, as the investigated materials showed a very limited difference of the slope of the isotherm within the studied RH regime. The upper and lower between the adsorption and desperation limit is 0.8\% and the lower one is 0.02\%. A sensitivity analysis using this span would reveal an estimate of the impact. In this paper, the average slope is used. Equation 4.8 suggest a square root dependence of the slope on the total moisture uptake.
Response:
4. Reviewer
Figure 5. The description under the picture needs to be corrected
Response:
Thank you, the caption was modified
5. Reviewer
Line 211- 213 Please explain what could be the reason for this?
Response:
We think that it can be due to the longer exposure to low rh and high temperature:
Page 13: The reason could be related to the shorter humidification interval (8h) and longer de-humidification (16h), as shown in Table 4. Moreover, the longer exposure to lower humidifies and higher temperature may slow down the moisture release.
But also:
As also shown in the experimental test (Table 4), the longer lag during the de-humidification in the 8/16h tests, compared to the humidification can be explained by analysing Eq. 4.8. If a 8/8 hours period was analysed, instead of the 8/16, the time tp period would correspond to 16 hours. For the16/16htest would be i.e. 32 hours. The difference in uptake mA would then differ between the 8/8 and16/16h approximately of √32/16=√2, which correspond to 40% difference. For the time delay, a pure sinusoidal variation suggests that the lag is directly proportional to the time period, which corresponds to a doubled time delay. The time delay ratio in the mixed case (8/16) in Fig. 9 is 1.17-1.62. Therefore, the asymmetry is reasonable as the delay ratio is in between 1 and 2, in line with the 8/8 and16/16 ratio.
.
6. Reviewer
Line 262 - The wrong equation number is given
Response:
Thank you, the number was modified
7. Reviewer
Line 252-253 To get the complete picture it would be adequate to add the value of the penetration depth value for the same time periods for clay and gypsum too.
Response:
The data are given in the text:
4.4.2 Gypsum:
tp=24 h dp=7.7 mm
tp=6 days dp=18.8 mm
Clay:
tp=24 h dp=7.5 mm
tp=6 days dp=18.5 mm
8. Reviewer
Figure 8 and 9. Please add a description of the curves, the figures will be easier to read
Response:
The caption was modified for both pictures:
The two curves with the largest amplitude represent the case with a six days variation (72/72h). The smoother and more sinusoidal like curve represents12/12h and the other 8/12h, respectively.
Reviewer 3 Report
This study is thoughtfully designed and the manuscript is well written. I recommend acceptance after minor editorial revisions.
1) Table 1: The property values and confidence intervals in many cases are given with an unnecessarily high level of precision. Zero decimal places would be appropriate for dry density; 1 decimal place for porosity and water vapour resistance factor.
2) In addition to plotting temperature/time and relative humidity/time profiles (Figures 1 and 2), it would be illustrative to plot water vapor pressure to make the time lag in moisture uptake more easily understood.
3) Figure 3 and many of the following figures: “Moisture uptake” would be more fitting than “Moisture buffering” for the vertical axis label.
4) Figures 3c and 4c: the time axis label should be days rather than hours.
Author Response
1. Reviewer
Table 1: The property values and confidence intervals in many cases are given with an unnecessarily high level of precision. Zero decimal places would be appropriate for dry density; 1 decimal place for porosity and water vapour resistance factor.
Response:
Thank you, the numbers were modified
2. Reviewer
In addition to plotting temperature/time and relative humidity/time profiles (Figures 1 and 2), it would be illustrative to plot water vapor pressure to make the time lag in moisture uptake more easily understood.
Response:
Thank you, the pictures with the vapour pressure were added
1. Reviewer
3) Figure 3 and many of the following figures: “Moisture uptake” would be more fitting than “Moisture buffering” for the vertical axis label.
4) Figures 3c and 4c: the time axis label should be days rather than hours.
Response:
Thank you, the pictures were modified
