Research article

The causes of air movement in hidden indoor micro-environments: measurements in historic bookshelves

Authors
  • Morena Ferreira orcid logo (UCL Institute for Sustainable Heritage, London, United Kingdom)
  • Josep Grau-Bove orcid logo (UCL Institute for Sustainable Heritage, London, United Kingdom)
  • Hector Altamirano orcid logo (UCL Institute for Environmental Design and Engineering, London, United Kingdom)
  • Nigel Blades (National Trust for England, Wales and Northern Ireland, London, United Kingdom)

This article is a preprint and is currently undergoing peer review by UCL Open: Environment.

Abstract

The use of ventilation holes in small micro-environments has been proposed as a mechanism to improve the environmental conditions of moisture and temperature within bookshelves. The National Trust, for example, has used these mechanisms to encourage air movement behind books as a possible strategy to reduce the risk of mould growth. It is believed that including ventilation holes as a passive design solution to promote airflow within micro-environments could prevent decay from occurring in archives of historic buildings. This paper investigates the mechanisms that cause airflow behind bookshelves using field measurements in three National Trust historical libraries. The measurements indicate that small but measurable velocities, up to 4 cm/s, can be generated passively behind bookshelves. Air movement in such confined micro-environments is caused by a combination of natural convection, caused by temperature differences between the interior and the exterior of the bookshelf(stack effect), and forced convection due to drafts in the surrounding environment. While in some cases one mechanism prevailed, both mechanisms may be present simultaneously in most cases. Finally, this paper proposes that air movement as a result of the stack effect in these micro-environments can be predicted with a simple mathematical model, which offers a good fit with the experimental data in the cases where temperature differences promote air motion.

Keywords: Preventive conservation, Mould, Built environment, Micro-environment, Historic buildings, Air movement

Preprint Under Review

 Open peer review from FERNANDO SARCE

Reviewer: FERNANDO SARCE
ORCID: orcid logo https://orcid.org/http://orcid.org/0000-0002-0737-2953
DOI: 10.14293/S2199-1006.1.SOR-ENG.AXXEIZ.v1.RCTSMZ
Date Completed: 2022-08-01

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-ENG.AXXEIZ.v1.RCTSMZ
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Engineering , Architecture
Keywords: Preventive conservation , Historic buildings , Built environment , Micro-environment , Air movement , Mould

Review text

1. At the abstract, it has been stated that "the use of ventilation holes in small micro-environments has been proposed as a mechanism to improve the environmental conditions of moisture and temperature within bookshelves". However, this has not been discussed on the results nor on the conclusions.

2. The stack effect is a natural thermodynamic phenomena, but how this related to the improvement of the "moisture excess" that you would like to partially eliminate? This would be a valuable research statement for your research.

3. Please refer as indoor/ outdoor environmental conditions. Indoor air relative humidity or indoor air pressure, etc.

4. Are you interested on the air motion to then determine an effective way to estimate a mass air flow rate (to dilute the presence of excessive moisture) depending on the air psychrometric conditions? In this case, is your contribution aimed to complement the current understanding on temperature and humidity modelling simulations?

5. Please explain why have you selected those heights for the anemometers locations. What is the rationale behind? It should be clear at the introduction of section 2.1.

6. Improve the quality of Figure 3. The data lines are difficult to see.

7. Please refers as air pressure in your hypothesis stated in Section 3.2.

8. Is it possible that air leakage on the window's frame could affect air speed together with some of the indoor/ outdoor openings in the buildings? If yes, can this be introduced in your methodology or for further research?



License: Creative Commons Attribution 4.0

Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

Note:
This review refers to round 1 of peer review and may pertain to an earlier version of the document.

 Open peer review from Lars Gunnarsen

Reviewer: Lars Gunnarsen
ORCID: orcid logo https://orcid.org/http://orcid.org/0000-0003-2227-7759
DOI: 10.14293/S2199-1006.1.SOR-ENG.ALCSN1.v1.RUELYY
Date Completed: 2022-09-28

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-ENG.ALCSN1.v1.RUELYY
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Engineering , Architecture
Keywords: Preventive conservation , Historic buildings , Built environment , Micro-environment , Air movement , Mould

Review text

The paper analyses data from continuous monitoring of air temperature, relative humidity, and velocity behind books in bookshelves and in the space in front of the shelves at three locations.

The driving forces behind air movements behind the books are seen as the result of differences in air temperatures influencing air density and the activities in the buildings housing the historic bookshelves including movements by visitors, renovation works and opening of doors.

The paper presents a simple model assumed to predict air velocities that is demonstrated to have some prediction capability but lacks precision and inclusion of important parameters such as surface temperatures of walls behind bookshelves and more precise information about openings between space and hidden environments.

The analysis would benefit from more precise modelling of boundary layers and buoyancy taken from more comprehensive fluid dynamic and heat transfer theory. The analysis would also benefit from more precise modeling of wall surface temperatures and information about outdoor temperatures during measurements.

Mold will normally start growing in the range 70-75 %RH. Absolute humidity measured as water weight per weight of dry air will without sinks and sources be constant in air flows being heated and cooled. Analyses of water content based on temperature and relative humidity would also be relevant in the available data. Moisture content of the cold exterior walls could be at equilibrium with somewhat higher relative humidity than measured in the air and be at higher risk of mold growth.

My thinking is that increased air flows behind the books in bookshelves may not be sufficient to prevent mold growth on cold outer walls but may increase the temperature of the books and their margin to mold formation.

Paper would benefit from more precise modeling of air flows, assessment of wall temperatures and inclusion of absolute humidity in the analysis.



License: Creative Commons Attribution 4.0

Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

Note:
This review refers to round 1 of peer review and may pertain to an earlier version of the document.

 Open peer review from Lars Gunnarsen

Reviewer: Lars Gunnarsen
ORCID: orcid logo https://orcid.org/http://orcid.org/0000-0003-2227-7759
DOI: 10.14293/S2199-1006.1.SOR-ENG.A3ILIG.v1.RTPDND
Date Completed: 2022-12-05

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-ENG.A3ILIG.v1.RTPDND
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Engineering , Architecture
Keywords: Preventive conservation , Historic buildings , Built environment , Micro-environment , Air movement , Mould

Review text

Wall temperatures could be approximated by knowledge of outdoor temperatures and properties of the walls. This information needs to be included. The intended more comprehensive analysis could be included in the present paper to increase relevance and credibility.



License: Creative Commons Attribution 4.0

Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

Note:
This review refers to round 2 of peer review and may pertain to an earlier version of the document.