Publisher’s version / Version de l'éditeur:
Technical Note (National Research Council of Canada. Division of Building Research), 1965-09-01
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
NRC Publications Archive
Archives des publications du CNRC
For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
https://doi.org/10.4224/20358940
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Meeting of the CIB Working Commission on Rain Penetration,
Rotterdam, 13-15 May 1964
Ritchie, T.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
NRC Publications Record / Notice d'Archives des publications de CNRC: https://nrc-publications.canada.ca/eng/view/object/?id=b2dde78b-2e5c-4c1c-b882-8212261b9b52 https://publications-cnrc.canada.ca/fra/voir/objet/?id=b2dde78b-2e5c-4c1c-b882-8212261b9b52
-
-DIVISION OF BUILDING RESEARCH
NATIONAL RESEARCH COUNCIL OF CANADA
ＬｾＮ
.
'If
EClHI N][ CAlL
NOTlE
No.
454
PREPARED BY T. Ritchie CHECKED BY PJS APPROVED BY RFL
September 1965
PREPARED FOR
SUBJECT
Inquiry and Record Purposes
MEETING OF THE CIB WORKING COMMISSION ON RAIN PENETRATION, ROTTERDAM, 13-15 MAY 1964
This meeting, the fifth of the Working Commission on Rain Penetration, was held at the Bouwcentrum building in Rotterdam. Two
building research organizations in Holland, Foundation Ratiobouw (Rotterdam) and Institute TNO for Building Materials and Building Structures (Delft)
acted as hosts for the meeting. There were two working sessions, Wednesday, 13 May and Friday, 15 May, with a tour of local building research labora-tories on the day between. The meeting and tour were well arranged and proceeded smoothly.
The following members attended the meeting: Norway:
Denmark:
France:
United Kingdom:
Mr. Birkeland (Chairman) and Mr. Isaksen (Norwegian Building Research Institute)
Dr. Becher and Mr. Christensen (Danish National Institute of Building Research)
Mr. Korsgaard and Mr. Madsen (Laboratory for Heat Insulation) Mr. Bietry (Centre Scientifique et Technique du Biitiment)
Mr. Villiere (Centre Technique du Bois)
"
Spain:
Holland:
Canada:
2
-Mr. Paredes and -Mr. Avendano (Seccif>n de Experimentaci6n, ｍｩｮｩｳｴｾｲｩｯ de la Vivienda)
Mr. Van Sante (Foundation Ratiobouw)
Mr. Broekhuis and Mr. Vos (Institute TNO for Building Materials and Building Structures)
Mr. Ritchie (Division of Building Research)
In arranging the meeting it was planned to discuss meteorological studies, including measurements of the wetting of walls and the preparation of driving rain maps, then to deal with laboratory test methods and finally to exchange experiences with rain penetration problems of actual buildings.
Several papers and reports were distributed to members prior to the meeting and were introduced by the authors for discussion. Mr. Lacy had prepared three reports dealing with various aspects of measurements of rainfall. In one of them a comparison was made of three types of rain gauges, a new gauge designed at the British Building Research Station, the Norwegian 4-way gauge, and the older BRS 8 -way gauge. It had been indicated in Mr. Lacy's studies that air flow greatly affects how much rain is caught in a gauge attached to a wall. A recent study made in Scotland showed this clearly. Two gauges were mounted on a wall, one close to a corner, the other 7 metres along from the corner. A free-standing gauge clear of the wall was also used. The relative amounts of rain caught by the gauges in a rainfall was 2.5:1 :4.8.
Mr. Lacy reported that driving rain maps had been found useful in the United Kingdom. He had been assigned the task of collecting such maps from member countries but progress was slow. The Working Commission now has maps of the U. K., Canada, Norway and Denmark
(the last was presented at the meeting). A map for France is being prepared. A difficulty has arisen in some cases due to the use of Beaufort wind scale in weather records, the problem being to convert such scale readings to metres per second.
Mr. Lacy mentioned the interest of the British Building Research Station in air flow around buildings and the effect this may have on rain
drops striking a wall. A wind tunnel is being built for studies of this problem. There is also an interest in "run-off" of rain from walls, especially where there are projections.
"
3
-Mr. Korsgaard and -Mr. Madsen reported on their studies of rain gauges. A comparison was made of the Norwegian 4-way gauge, the British 8 -way gauge and their newly-developed "all-way" gauge. Similar results were obtained with the three gauges. The last-mentioned, however, does not give the direction of rainfall.
Mr. B,roekhuis showed a rain gauge developed recently at TNO which simultaneously catches rain entering it, and catches water running down the wall. This instrument is being used at TNO.
Dr. Becher and Mr. Christensen reported on their studies of frost action on insulation-filled cavity walls. This type of wall has been used for about 15 years in Denmark, apparently with no trouble resulting when durable bricks were used. Preliminary tests were reported in which wall sections were subjected to wetting, then to freezing and thawing of one side while the other side was maintained at room conditions. The tests made so far have shown that decay of the outer wythe occurs only when frost-susceptible bricks are used. Such bricks also fail in unfilled-cavity walls; the indications are, therefore, that the insulation-filled cavity does not promote decay by frost action. Dr. Becher said there have been
instances of rain penetration of filled cavity walls of buildings, attributed to mortar bridges of the cavity.
The author reported that DBR in Canada has learned of several failures of glazed brick, a material coming into rather extensive use in Canada.
Mr. Vos described a probe developed at TNO for determining the moisture content of walls. It operates on the principle of a relation-ship between the thermal conductivity of a material (which can be measured in s{tu) and its moisture content. It is possible to place a probe in a wall and to obtain a measurement of moisture content at nine locations across the wall, thus the distribution of moisture may be traced.
Mr.
Korsgaard and Mr. Madsen described their studies ofinsulated cavity brick walls. In such walls there is little effect of moisture in the bricks on the insulating value of the wall since all the insulating value is provided by the rock wool insulation. The moisture content of surface-treated walls (rendered with a thin coating) was found to be appreciably higher than that of the same wall unrendered.
4
-Mr. Birkeland and -Mr. Isaksen spoke about Norwegian studies; the former said that solid masonry, especially of lightweight concrete, has given much trouble from rain penetration because of the tendency to
develop cracks. Solid walls therefore should not be used; an air gap in the wall (cavity wall) is essential. Mr. Isaksen described tests made at his laboratory at Trondheim of rain penetration of various types of joints between building elements, e. g., between parts of a window. The width of the opening, the slant, and the nature of the surfaces, are very important to the tightness of the joint. Gaskets may be necessary in windows to ensure tightness. Newer plastic materials show promise for this application.
Tests of the resistance to rain penetration of wooden windows were reported by Mr. Villiere of France. These tests have also shown the
importance of wind pressure and air leakage on rain penetration. Mr. Broekhuis described his work at TNO using'models of joints to test for rain penetration. Models of actual designs of joints are cut from plastic and tested in a small apparatus in which the air pressure may be adjusted (steady pressure or gusts) and water drops are sprayed on the sample. The glass sides of the chamber allow observations to be made of paths of leakage. This method of test has been found particularly useful for studying the tightness of that area where a vertical joint meets a
horizontal joint. It was stated that it is very difficult to make a rain-tight window which opens to the inside. The practice now in Holland is to make all windows open outwards.
The author reported studies made by DBR at Ottawa and Halifax of the moistur e content of materials in r elation to the driving rain index. Various masonry materials were exposed to the four directions at both stations (which differ widely in driving rain index) and the samples were weighed periodically to trace changes in moisture content. An interesting finding was that there was not an appreciable difference in moisture content of the samples exposed at Ottawa and Halifax, even though there was a considerable differ ence in driving rain index.
Mr. Bietry described the test apparatus being used in his laboratory for rain penetration studies. It differs from others in that air is blown at an angle to the sample surface and it is possible to vary the
angle of incidence. The apparatus has two air pumps, one of which provides the air flow, the other maintains the super-pressure.
5
-Mr. Lacy reported that BRS is building a new "rain machine" capable of testing storey-height samples. It will be able to provide
variable rain conditions. A study is being made of weather data to provide a realistic test condition.
Mr. Birkeland reviewed his paper on test methods, which is proposed as a CIB publication. An important factor in testing is wetting
of the sample. There was a discussion of water films on wall surfaces; most members reported having seen a film of water on walls of buildings during heavy rain, therefore to establish such a situation in a test is
realistic. Mr. Birkeland said that in tests of panels (for curtain walls and panel walls) a high sample should be used (1t storeys) and it should be wide
enough so that intersections of vertical and horizontal joints are tested. The fastenings of the panels must be the same as those to be used in the actual building.
Mr. Vos described work proposed by TNO to measure air flow around buildings. This is to be done by installing hot-wire anemometers on the wall surfaces. He pointed out that there is a great lack of infor-mation on how air flow affects the wetting of walls by rain drops, and even about the flow ar ound a building.
In connection with t est methods for rain penetration the author suggested that, in view of the wide variety of tests being used by the members, it might be useful to send around a sample, for example a window, to each laboratory to be tested by the particular method being used. A comparison of test results may show the importance (if any) of the particular test conditions used, such as the size of the water drops, degree of wetting, and pressure difference.
A symposium on moisture problems in buildings, jointly planned by CIB and RILEM to be held in Helsinki in 1965, was mentioned by
Mr. Birkeland who noted that the program of the symposium includes "moisture penetration" as one of its subjects. He propos.ed that three papers be presented by members of the Working Commission on Rain Penetration: (1) the onslaught of rain on buildings (to be prepared by Mr. Lacy), (2) the work of the CIB Working Group on Rain Penetration (to be prepared by Mr. Birkeland) and, (3) a paper on test methods(by Mr. Bir keland).
·a
ｾｾ
.,
6
-In concluding the meeting the Chairman noted that the Commission had been operating for 10 years and it was necessary to consider its future.
If it continued, consideration should be given to the nature of its future work. Dr. Becher and others stated that the Commission had accomplished much useful work and should be continued. Mr. Birkeland suggested
that the emphasis might shift in the future to two aspects in particular of the problem of rain penetration: measurements of onslaught of rain on buildings and the further development of laboratory test methods.
It was proposed that the next meeting should take place in Madrid in 1966.
TOUR OF LABORATORIES
The second day of the meeting (14 May) was set aside for visits to three laboratories. Two of them were laboratories of Institute TNO for Building Materials and Building Structures, one dealing with heat and moisture problems, the other with tests of rain penetration. The third laboratory, located about 30 ｭｩｬｾｳ from Rotterdam at Loenen, and
operated by NEDACO, (the Netherlands Association of Roofing Tile Manu-facturers), was established to study problems of rain penetration of roofs.
The group was welcomed to TNO by the Director, Mr. Van
Seters, who gave a short talk on TNO and its function (similar to the National Research Council of Canada). A visit was made to the laboratory of
Mr. Vos whos e work has to do with heat flow and moistur e flow. A study is being made of test walls which are alternately wetted and dried, some with a temperature difference maintained across them. The moisture probes described previously are being used to trace the distribution, and the over -all moistur e content is being ｣ｨ･｣ｾ･､ by weighing the samples which also gives the rate of drying. Previously-used heat flow meters were found to give poor results, especially when moisture was present in the walL
A new building has been constructed to form a wall-testing laboratory. Openings have been left in the walls and test samples are placed in the spaces. The test samples are instrumented for heat and moisture measurements and rain gauges are fitted on the outer surface.
/
7
-Much use is being made'in the laboratory of automatic equipment, such as weighing devices, and temperature and moisture recording devices.
In the laboratory operated by Mr. Broekhuis the visitors were shown the model-testing apparatus described previously in which models of joints (e. g. window sections) can be subjected to rain and air pressure, and the leakage paths readily traced. Other laboratories were also
visited including that containing alar ge apparatus for rain penetration tests. It has the capacity to test a wall section of storey-height and about 20 ft wide. A test has been made of a conventional wall section (including door and window), which was very leaky, then of a similar wall section designed by TNO to overcome the problems of the conventional wall.
This wall performed well. The use of poor quality wood (poorly seasoned) was mentioned as amajor factor in leakage problems of houses in Holland because such wood shrinks and warps, resulting in openings for leakage.
At the NEDACO laboratory the group was welcomed by officials of the Netherlands Roofing Tile Manufacturers Association. It was pointed out that practically all roofing in Holland is of clay tiles. The manufacturers decided about six years ago to set up a laboratory to investigate rain
penetration problems, particularly since there was a trend to the use of low-slope roofs and therefore a greater possibility of leakage troubles developing. There is a staff of 6 or 7 in the laboratory which is devoted entirely to the rain penetration problem, but it was mentioned that the work may be extended to durability studies later. The laboratory is housed in a former church which is considered an ideal building for the type of test being used because of the large free space inside it.
In the rain penetration tests a large sample of roof is used which is about 15 ft square. It is mounted on a deck that can be adjusted to provide any required degree of slant to the roof. A network of pipes with holes spaced along them is fitted above the roof sample. Water under pressure by a gravity feed passes through the pipes and falls from the holes. A horizontal scr een beneath the pipes (about 1/8 -in. mesh) catches the water and breaks it down into a uniform pattern of drops. The screen is vibrated. Air flow over the sample roof is provided by a variable-speed propeller. Rain water, collected previously and stored, is us.ed in the tests.
/
8
-The roof is tested at various angles to the air flow. -The leakage beneath each row of tiles is collected. Previous to constructing a sample roof all tiles are checked for warpage and squareness; the amount of leakage in the test has been traced in many cases to excessive warpage of individual tiles used in the roof. As a result of studies made in this laboratory it is considered possible to build a rain-tight tile roof at a slope of 15 degrees, rather than at 30 degrees which was previously thought to be the minimum slope possible to avoid leakage.
An interesting study being planned is to collect tile roofs from actual buildings in which there has been no leakage problem and to use these tiles to build a test roof. In this way the laboratory test results
can be "calibrated" with actual service results. CONCLUSIONS
The meeting of the CIB Working Commission on Rain Penetration resulted in a useful exchange of experiences with, and ideas on, the
problem of rain penetration of buildings. Membership in the Commission has grown to include representatives of 18 countries, which indicates that rain penetration is an extensive problem in building. The meeting was well arranged and because of this its business proceeded smoothly. Visits to three laboratories in the Rotterdam area were also useful and interesting.
The Working Commission on Rain Penetration is considered to perform a useful function as a "clearing house" for the .exchange of infor-mation on this important problem. Studies being made in DBR on rain penetration are of interest to the members of the Commission, and at the same time much useful information has come to DBR as a result of its association with the Commission.
