Buildings That “Leak” Only on Sunny Days: Case Studies and...

Buildings That ldquoLeakrdquo Only on Sunny Days Case Study and Investigative Guidelines

LONNIE HAUGHTON CDT LEED AP Richard Avelar amp Associates

318 Harrison St Suite 103 Oakland CA 94607 P 510shy893shy5501

eshymail lhaughtonravelarcom

Proceedings of the RCI 25th International Convention Haughton shy 101

ABSTRACT

The speaker will present a case study of a commercial space that has sat empty since its conshystruction due to intermittent hot weather ldquoleakagerdquo from the bottom side of its roof deck Dataloggers confirmed the regular midday appearance within the interior of increased levels of water vapor due to solar heating of the building envelope The location of an unintended resershyvoir of excess water was identified and the process by which condensation resulted at the OSB deck was explained The case study demonstrates that the best approach to such puzzles often is to first ask where the excess water could be located

SPEAKER

Lonnie Haughton uses forensic expertise and a wide range of investigative tools ndash from moisshyture meters to watershyfinding test paper to inshysitu sensors to calcium chloride vapor domes to hygrometers to psychrometric tables to WUFI software ndash to solve leakage and condensation puzzles in California and Nevada Lonnie is a regular contributor to Interface magazine in which he authors informative articles that explore theoretical legal and practical aspects of forensic evaluations of building envelope performance

Haughton shy 102 Proceedings of the RCI 25th International Convention


Photo 1 ndash Vacant electronics manufacturing facility in California at southeast and northeast eleshyvations

ABSTRACT This paper introduces a vacant

3500shysqshyft electronics manufacturing space in the San Francisco Bay metshyropolitan area that has sat empty since its construction in 2004 due to sporadic afternoon hotshyweather ldquoleakshyagerdquo from the bottom side of the engishyneered wood roof deck and associated steel supports This puzzling pheshynomenon had been investigated unsuccessfully first by the buildingrsquos developer general contractor and roofer and then by an intermittent series of engineers and other consulshytants In 2008 the authorrsquos evaluashytion of data from humiditytemp shy

erature loggers installed within the facility confirmed the daily midday appearance of elevated concentrashytions of water vapor Further analysis indicated these daily ldquowavesrdquo of ambishyent vapor were caused by solar heatshying of water reservoir(s) residing at the building envelope or its surshyrounds Upon additional review both the general location of this moisture pool and the most likely process by which solarshydriven vapor caused conshydensation at the ceiling were reported to the owners This paper summarizes the forensicshysurvey process and recshyommends ldquoinvestigative guidelinesrdquo for similar investigations

INTRODUCTION Photos 1 through 3 present a

vacant southeastshyfacing building The exterior walls are constructed with concrete tiltshyup panels that terminate below grade at concrete footings The floor is a 6shyinch reinforcedshyconcrete slabshyonshygrade The aluminumshyframed fixed windows were assembled in place The builtshyup roof covering assembly consisting of three hotshymopped ply sheets and a granuleshysurshyfaced reinforced glass mat cap sheet is marketed by a major manufacturer The roof deck consists of OSB (orientshyed strandboard) panels installed over steel trusses and wood purlins A


gravity vent at the roof (Photo 3) has been the sole means of ventilating the interior space

Fiberglass batt insulation with a polyethylene facing (see Photo 4) is installed between the purlins with slight sagging that creates ldquodeadrdquo airshyspace immediately below the deckshying1 As seen in Photo 5 unsealed voids at the ends of the batts particshyularly at the steel trusses allow some air (and vapor) flow between the dead air cavities and the ambient interior

A condensation2 problem evishydenced by water dripping from steel trusses and connectors within the dead airspace above the batt insulashytion (see Photo 5) was reported to occur at earlyshyafternoon hours during hot sunny weather Resulting corroshysion of the structural steel can be seen in Photo 6 During the authorrsquos initial site visit in April 2008 the first drips were observed at about 2 pm the exterior temperature at this time was 80ordmF

Investigation by Professional Engineer in 2006

In response to initial complaints of ldquoroof leakagerdquo occurring only on sunny days a wellshyqualified mechanshyical engineer was hired by the project developer in 2006 After a compreshyhensive investigation this engineer reported

Photo 2 ndash Vacant commercial space intended as small electronshyics manufacturing facility

Photo 3 ndash Fourshyply roof covering system consists of three hotshymopped ply sheets and glassshyreinforced cap sheet Note the

gravity vent

Photo 4 ndash Fiberglass batt insulashytion with a polyethylene facing is installed between the purlins with slight sagging that proshyvides ldquodeadrdquo airspace immedishyately below the OSB decking


He expected that the added heat would promote drying of the (presumshyably) wet decking and that the dehushymidifier then would remove this excess moisture from the building

As seen in Photo 7 full removal of the ceiling insulation revealed no evishydence of the staining damage or decay at the exposed face of the watershysensitive OSB that might have been expected from a reservoir of moisture trapped somewhere within the roofing system

Even so upon removal of the insushylation batts several large dehumidishyfiers were operated within the vacant

Photo 5 ndash Sporadic condensashytion problem occurs at earlyshyafternoon hours during hot weather

bull Sensors positioned within the batt insulation recorded norshymal humidity levels during the night and morning hours followed by abruptly sharp increases to dewpoint saturashytion in the early afternoon These conditions repeated daily

bull Removal of several insulation batts during a period of conshydensation found the OSB roof deck and associated structurshyal steel to be visibly damp over the entire surface but lacking any observable indishycations of water staining wood decay or water leakage

Based upon these observations the engineer concluded that an undeshytermined prior event had produced a reservoir of excess moisture hidden within the roof covering assembly and that the effect of solar heating of this wet roofing was to drive water vapor inward until it condensed at cooler surfaces within the dead air spaces above the insulation batts This process often is described as ldquosunshydriven moisturerdquo or ldquosolarshydriven difshyfusionrdquo

Photo 6 ndash Corrosion at steel truss Note absence of observable water damage at OSB decking

Sunshydriven moisture is a phenomenon that occurs when walls are wetted and then heated by solar radiation Upon solar heat ing a large vapour [sic] pressure difference may occur between the exterior and interior leadshying to the inward diffushysion of moisture3

The engineer recommended temshyporarily removing the batt insulation to facilitate simultaneous heating and dehumidification of the interior space

space for an extended period while ldquomany tens of gallonsrdquo of water were extracted from the ambient air Unfortunately the ldquoroof leakagerdquo reappeared soon after the insulation batts were reinstalled and has continshyued to occur during ensuing months and years as more consultants were hired to engage the problem

bull Note At a later time after the 2006 reinstallation of the insulation batts the perimeshyter ends of the polyethylene facing were taped to the adjashy


cent structural members to minimize air transfer This action reportedly lessened the extent and severity of water drips observed at the perimeter ceilingshytoshywall transitions however these condensation events continshyued unabated at the nonshytaped joints (see Photos 4 and 5) where the insulation batts terminate at the steel trussshyes

SUBSEQUENT INVESTIGATIONS

During this ensuing period a wideshyranging series of tests and inspections by various inspectors included a) destructive sampling by the original roofer of the roofing assembly b) deactivation of the HVAC system for the commercial space c) close examination of the aluminum storefront windows for evidence of leakage d) moisture metering and calcium chloride vapor testing of the floor slab by an engineering consulshytant e) a nondestructive roof survey by another consultant using an elecshytrical impedance meter f) acoustical sounding of the vacant building and the floor slab for potential plumbing leaks and g) coring of the concrete slab to confirm the presence of an undershyslab vapor retarder The results of these various tests are sumshymarized as follows

a The destructive sampling at the lowshyslope roof was not independently observed and was limited to several test cuts in the field above one of the areas where the hot weather ldquoleakagerdquo often was observed (The original roofer reported that his testing proved that the roof covering system was installed as designed and was performing as intended)

b Deactivation of the seldomshyused HVAC system produced no observable effect on the sporadic condensation probshylem

Photo 7 ndash Removal of the fiberglass insulation reveals localized corrosion of the structural steel but no observable evidence of trapped water at the wood purlins and OSB decking

c No evidence of installation deficiencies or past water infiltration was observed at the window surrounds

d Calcium chloride testing4 of the concrete floor slab at varshyious field and perimeter locashytions reportedly produced moisture vapor emission rates (MVER) of less than 20 lbs of vapor per 1000 sq ft per 24 hours however the MVER value above the thickshyened slab edge near the side (NE) exterior wall was about 30 lbs These values were not deemed excessive5 howshyever it should be noted that the inspector failed to propershyly prepare the concrete surshyface in accordance with Section 62 of ASTM F1869 (This failure to remove the surface sealer is likely to have produced lower MVER values than would have been achieved with proper surface preparation)

e Months later a roof survey by an independent consultant

found no evidence of a perforshymance problem or any resershyvoir of trapped moisture from a prior rain event

f Soon thereafter an acoustical survey throughout the vacant building by an experienced professional revealed no evishydence of hidden plumbing failures Near the front wall soundings through the floor slab did produce acoustical anomalies (ldquoreverbsrdquo) that reportedly were consistent with groundwater at the base of the wall or its footings

g Subsequent coring of the floor slab at four locations confirmed the concrete slab was installed over a 1shyinch layer of sand over a continushyous polyethylene vapor reshytarder At all locations the soil below the polyethylene vapor retarder was found to be dry however at a test hole near the northeast wall (near the location of high MVER found at item ldquodrdquo) the sand layer above the vapor reshy


tarder was found to be much wetter than the sand extractshyed from the other holes6

In short an extended period of inspections and testing by a series of qualified investigators had revealed no actionable evidence of problematic building performance at the roof the walls or the concrete floor slab Several indicators of increased moisshyture content levels near the front and side walls had been observed howevshyer no one suspected a causal relashytionship between the ceiling condenshysation and these perimeter condishytions

In other words despite multiple inspections and analyses by a wide variety of consultants more than three years after initial discovery of the problem there remained no agreed explanation for the earlyshyaftershynoon condensation occurring at the bottom side of the roof deck Nonroofing experts still suspected a reservoir of trapped water hidden within the roofing assembly Others simply had no credible hypotheses

2008 Forensic Survey

The author was hired by the ownshyers of the nonusable commercial space in time to witness the roof surshyvey (item ldquoerdquo) the acoustical survey (item ldquofrdquo) and the coring of the floor slab (item ldquogrdquo) described above Except for the noted concern regardshying the calcium chloride testing process (item ldquodrdquo) our close inspecshytion and moisture metering7 of the interior slab and exterior walls found nothing that would discredit the earlishyer inspections and testing

The purpose of the authorrsquos survey was to assist stalled legal negotiations between the owners and the original developer The owners required a dry commercial space suitable for manushyfacture of microelectronic devices but the developer could not implement a mutually acceptable repair if the source of the condensation problem could not be determined

The scope of our commission was to evaluate the evidence collected preshy

viously by the various professionals propose any supplementary nondeshystructive testing that might be approshypriate and then to identify to the building owners the most likely causeshyandshyeffect relationship between building characteristics and the sposhyradic condensation problem In short our assignment was to carry out a limited forensic analysis that identishyfied the most likely explanation for the condensation puzzle

The investigative process was modeled upon a standard protocol (per ASTM E2128) for investigative evaluations of problematic leakage conditions

1 An evaluation is conshyducted in response to a problem situation hellipand may involve several techshyniques and procedures specifically adapted and applied in a systematic manner to diagnose a speshycific problem

2 The information sysshytematically accumulatshyedhellip is analyzed as it is acquired The new inforshymation may motivate a change in approach or fo shycus for subsequent steps in the evaluation process

3 The evaluator is exshypected to establish a causeshyandshyeffect relationshyship between [building] characteristics and obshyserved leakage This re shyquires an appropriate se shylection of activities and a logical analysis and intershypretation of the acquired information

4 The conclusions and findings from an evaluashytion must be rationally based on the activities and procedures undertakshyen and the information acquired if they are to be considered legitimate and substantiated

5 The record should be sufficiently complete so that any interested party can duplicate the evaluashytion program and acquire similar informationrdquo8

In a previous paper the author has extolled the merits of this invesshytigative protocol ldquohellipA forensic buildshying envelope professionalrsquos survey methodology and testimony typically should be based upon recognized scishyentifically valid principles of qualitashytive analysis as exemplified by ASTM E2128rdquo9

Similarly the authorrsquos article in the November 2008 issue of Interface noted that ASTM E2128 ldquoprescribes an orderly stepshybyshystep accumulation of information in such a manner that each step enhances and supplements the information gathered in the preshyceding step hellipPermeating throughout the building envelope survey strategy delineated in ASTM E2128 is the critshyical goal of tying together cause(s) and effect(s) hellipThis investigative process commonly is both inductive and deductive and should be carried out with methodological competence intellectual rigor and professional integrityrdquo10

INVESTIGATIVE GUIDELINES

To these ends the following invesshytigative guidelines are recommended by this author for forensic surveys of similar condensation puzzles

Investigative Guideline 01 Locate the source(s) of uninshytended water

Most moisture problems can be diagnosed by lookshying at the condition and asking how much water it took to create that probshylem Solving the problem amounts to asking where that amount of water could have come from and where it should go11

Longshyterm condensation condishytions within buildings require replenshyishment of the condensed vapor by


new water vapor from one or more sources Too often attempted forensic analyses of condensation puzzles are doomed to failure because the investishygator tries to use an engineering model such as the professional vershysion of the popular WUFI program to theorize overwhelmingly complex hygrothermal processes that contain multiple unknown and difficultshytoshydetermine variables Instead the recshyommended first step for tackling such puzzles is to locate the moisture source then the task of deciphering how the condensation resulted will be much simpler

For this investigation review of the prior testing had revealed indicashytors of possible reservoir(s) of belowshygrade water at the front andor side exterior walls In addition while supshyplemental metering of the floor revealed a satisfactory range of moisshyture content levels the highest readshyings were found near the same two walls (above the thickened slab edge seen in Figure 1) It remained possishyble of course that any such reservoir located at or near the slab edge had no substantive relationship to the condensation problem Still the most efficient approach to successful investigative surveys is ldquoFind the moisture sourcerdquo

Investigative Guideline 02 Consider the common origins of unintended water within buildings

Prior to commencing the search for unknown moisture sources the investigator should review the comshymon origins of unintended water within buildings

1 Liquid water from precipishytation (rain and melting snow)hellip

2 Liquid water fromhellip plumb ing leaks

3 Water vapor from the exteshyriorhellip

4 Water vapor fromhellip activishyties and processes within the building

5 Liquid and vapor from the soil adjoining the building

6 Moisture built in with the materials of construcshytionhellip and

7 Moisture brought in with goods and people14

In this case we had a vacant and unoccupied building with no ongoing ldquoactivities and processes within the buildingrdquo no plumbing leaks (per the acoustic survey) and no evidence that the summertime condensation con ditions were caused by ldquoliquid wa shyter from precipitationrdquo15 Close inspecshytion of the vacant interior space had found no evidence of liquid water penshyetration at any portion of the building envelope including the slabshyonshygrade floor Similarly there simply was no evidence to suggest that this unabatshyed multiyear problem had resulted from original ldquomoisture built in with the materials of constructionrdquo

In other words by a process of elimination our analysis indicated that the most likely source(s) of the problematic moisture that was causshying the condensation at the ceiling were ldquowater vapor from the exteriorrdquo

Photo 8 ndash Could excessive moisture infiltration (via air convecshytion) through the gravity vent cause the interior condensation problem

andor ldquovapor from the soil adjoining the buildingrdquo

bull Excessive amounts of water vapor from the exterior could be entering the building via air convection through voids at windowshytoshywall transitions or at the roof covering assemshybly (or perhaps through the gravity vent seen in Photos 3 and 8) or

bull Similarly unintended levels of water vapor from the surshyrounding soil could be infilshytrating the building interior via air convection through gaps at the walls windows or foundation or

bull Unintended levels of upward vapor diffusion into the inteshyrior space could be occurring if the longshyterm moisture content of the concrete slab was unusually high andor

bull Excessive levels of inward vapor diffusion could result from solar heating of liquid water that had been absorbed into the concrete walls (As previously noted this potenshy


Actual Grade of Landscaping and Asphalt Hardscape

tially problematic process often is called solarshydriven diffusion)

The previous calcium chloride testing (item ldquodrdquo) and the authorrsquos sub sequent moisture metering ap shypeared to have ruled out problematic levels of upward vapor diffusion at a ldquowetrdquo floor slab Still due to the noted concern about the quality of the concrete testing process the owners of the vacant space were asked to cover the floor with a conshytinuous layer of plastic tarping (see Photo 9) in general accordance with the ldquoplastic sheet testrdquo described in ASTM E190716

The purpose of this test was to ascertain whether or not observable evidence of vapor condensation would occur under the sheeting (thus indicating high moisture levels withshyin the slab) The tarping was allowed to remain in place for a multiweek period in which several more vapor condensation events were reported at the ceiling During this period only one strip of moisture condensation was observed under the tarp ndash again above the thickened slab edge (see Figure 1) at the northeast elevation17

In summary the multiweek tarp test and related earlier testing (in shycluding the slabshycoring activities described at item ldquogrdquo) collectively had provided strong evidence to exclude the concrete floor slab or groundwater

under the slab as a primary vaporshygenerating source of the water necesshysary for continuation of the condensashytion events occurring at the ceiling

At this stage of the investigation the stepshybyshystep survey process had excluded all of the ldquocommon origins of unintended waterrdquo listed above ex cept for air convection of ambient exterior vapor andor solarshydriven diffusion at the concrete walls at the front and side elevations (The west elevation of the vacant space is an interior comshymon wall shared with an adjacent commercial space) As noted the origshy

Photo 9 ndash Continuous plastic tarping was placed over the floor slab during condensation test Note the solar exposure at the northeast and southshyeast elevations during summer months

Figure 1 (below) ndash Concrete tiltshyup panels terminate below

grade at concrete footings

inal engineerrsquos analysis in 2006 had blamed the ceiling condensation on solarshydriven vapor diffusion from trapped water within the roofing assembly but subsequent inspection analysis and testing had discredited that hypothesis

Upon review of the structural drawings for the project the concrete tiltshyup panels at the exterior walls were found to terminate below grade at concrete footings (see Figure 1) None of the provided construction drawings called for belowshygrade waterproofing or perimeter drainage


at the base of the walls

In addition the drawings and specifications did not call out belowshygrade waterproofing or perimeter drainage at the building perimeter and limited excavation at the front elevation had found no evidence of belowshygrade waterproofing Further we noted that the actual grade of the adjacent irrigated landscaping and asphaltshycement hardscape roughly matched the top of the interior floor slab We also observed that an irrigashytion system regularly waters the landshyscaping at the front of the building producing lush vegetative growth (see Photo 1) These various additional observations continued to suggest that belowshygrade water reservoir(s) at the front andor side walls could be the source of the water vapor necesshysary for the condensation events at the ceiling18

Investigative Guideline 03 Donrsquot forget the Second Law of Thermodynamics

bull The Second Law of Ther shymodynamics requires as a fundamental law of the universe that when two unequal reservoirs of en shyergy (including disparate concentrations of ambient water vapor) are connectshy

ed the greater pool will flow into the lesser pool until equilibrium is reached

bull For water vapor this pro shycess of energy flow has been summarized by North Americarsquos leading building science experts as ldquomoisture tends to move from warm to cold (driven by the magnitude of the thermal gradient) and from more to less (drishyven by the concentration gradient)rdquo19

Investigative Guideline 04 Use one or more portable temshyperatureRH loggers to monitor ambient moisture content over an extended period

Photo 10 shows typical portable humiditytemperature loggers20 used for investigations of problematic moisture in buildings As demonstratshyed below temperature and relative humidity (RH) data collected from such dataloggers can be processed with readily available software to in shyform us of the approximate ldquohumidity ratiordquo (ie ambient moisture content) within the space The humidity ratio is expressed as pounds of water vapor per pound of dry air21

Photo 10 ndash Typical portable loggers used by the author for humidity investigations

Many building professionals alshyready employ a variety of meters to evaluate moisture content levels of specific building materials (such as wood or concrete) and assemblies of materials (eg lowshyslope roofing sysshytems) The humidity ratio simply informs us of the moisture content of ambient air in much the same manshyner that commonly used meters inform us of the moisture content of wood and concrete

The author has promoted the use of these temperatureRH loggers to monitor the rise and fall of ambient moisture content trends over a lengthy period (eg 20 to 100 days) in order to then evaluate when and why these changes occurred22 After the loggers have been retrieved their digshyital data is transferred to a computer for storage processing and review via proprietary software and Microsoftrsquos Excel spreadsheet program Investi shygators who are reasonably skilled with Excel have numerous options for analytical statistical and comparashytive evaluations of data streams from one or many loggers

Investigative Guideline 05 Generally do not position datshyalogger(s) directly adjacent to sources of moisture production or intrusion

For most forensic testing of enclosed spaces whether inside a room or a wall cavity the datalogshyger(s) should not be positioned immeshydiately adjacent to potential sources of moisture production or intrusion For example water vapor (eg from a teakettle) will quickly disperse equally throughout an enclosed space in accordance with the Second Law To best understand the overall impact of the teakettlersquos vapor production on an apartmentrsquos ambient air the data series collected from one sensor locatshyed in the middle of the room will be more readily useful than the data recorded at the massive humidity spike occurring at the teakettlersquos spout


Front Door

Northeast

Investigative Guideline 06 Multiple loggers are recomshymended when the goal is to decipher ambient moisture migration from one location to another

In many cases a properly posishytioned single datalogger is suitable for monitoring an entire space particushylarly when the general goal of the testshying is to evaluate ebbs and flows of ambient interior moisture (perhaps due to the effects of exterior precipitashytion or human activities) On the other hand multiple dataloggers should be deployed for moisture conshydensation puzzles in order to identify the patterns and orientation of moisshyture movement from more to less (the concentration gradient) and warm to cold (the thermal gradient)

For this survey the site plan in Figure 2 identifies the placement of three portable loggers the office datashylogger (positioned above the ceiling tiles in the front office the front datashylogger (hanging from the ceiling about 18 ft above the floor) and the rear datalogger (about 19 ft above the floor) The office datalogger is separatshyed from the others by interior walls and a closed door An exterior logger also had been installed outside the front wall (Logistical and budgetary constraints limited the number of logshygers that could be deployed and monshyitored23)

In accordance with the Second Law the positioning of these datalogshygers should enable identification of the directional flow (if any) of in shycreased water vapor appearing within the space

Figure 2 ndash Site plan for vacant commercial space Entry door is at far right at southeast elevation Note locations of office datalogger front datashylogger and rear datalogger

bull If on a daily basis an in shycreasing quantity of ambient interior moisture does (or does not) initially appear at only one of the interior datashyloggers we quickly have learned a lot about the orishygins and directional migrashytion of the vapor

bull Similarly it would be highly informative if two or more loggers simultaneously reshycorded the commencement of daily moisture increases and

bull It would be particularly in shystructive if there happened to

Figure 3 ndash Office datalogger (43059) on 08302008 at 700 am (compare with Figure 6)

Figure 4 ndash Front datalogger (43015) on 08302008 at 700 am (compare with Figure 7)


Figure 5 ndash Rear datalogger (43707) on 08302008 at 700 am (compare with

Figure 8)

be a strong correspondence between the humidity ratio data produced by the exterior datalogger and data from any of the interior loggers

For example the matrices in Figures 3 4 and 5 inform us of temshyperature relative humidity and dewshypoint readings on August 30 2008 at 700 am from the office datalogger front datalogger and rear datalogger From these data the humidity ratio (ambient moisture content) values were derived with separate psychroshymetrics software24 The results were evaluated and summarized with Mi shycro soft Excel (Note The temperature and RH data were recorded at 1shyminute intervals however for similar investigations the author prefers a fiveshyminute data collection schedule to facilitate the review process)

Figures 6 7 and 8 then present afternoon data for August 30 2008 from the same three dataloggers In essence these three matrixes identify the particular afternoon point of time at which a ldquowaverdquo of infiltrating water vapor first reached its peak (ie the highest humidity ratio of the day)

bull At 236 pm the office datashylogger first recorded its highshyest humidity ratio 001166 pounds of water vapor per pound of dry air (4333 more moisture than 700 am)

bull At 237 pm the front datashylogger first recorded its highshyest humidity ratio 001195 pounds of water vapor per pound of dry air (3342 greater than 700 am) and

bull At 346 pm the rear datashylogger first recorded its highshy

Figure 8 ndash Rear datalogger (43707) on 08302008 at 345 pm (compare with

Figure 5)

Figure 6 ndash Office datalogger (43059) on 08302008 at 230 pm (compare with Figure 3)

Figure 7 ndash Front datalogger (43015) on 08302008 at 230 pm (compare with Figure 4)


Figure 9 ndash Average hourly humidityshyratio results from front datshyalogger peak about 200 pm

Figure 10 ndash At rear elevation the moisture cycles peak about 345 pm

est humidity ratio 001108 pounds of water vapor per pound of dry air (2368 greater than 700 am)

In short we see that a wave of infiltrating water vapor first reached its peak humidity ratio more than one hour later at the rear datalogger than when the moisture peaks commenced

at the office and front dataloggers We also see that the peak of the vapor wave occurred almost simultaneously at the office and front dataloggers even though these devices are located in separate enclosed rooms In accorshydance with the Second Law (ie vapor moves from more to less and warm to cold) the close corresponshydence between these two loggers indishy

Proceedings of the RCI 25th International Convention

cates a common origin of this moisshyture event Further the close correshyspondence of the data indicates the shared moisture reservoir is located outside the front of the building

Now consider Figures 9 and 10 which graph the average hourly moisshyture influx recorded by the front datshyalogger and the rear datalogger for four continuous days from Aug 30 at 700 am to Sept 3 2008 at 600 am (Note during this period the interior plastic tarping seen in Photo 9 remained in place) Observe the daily cycles of infiltrating water vapor peaking at about the same time every day

Additional review of the massive amount of temperature and RH data that has been collected at this project confirms that to a greater or lesser degree similar midday influxes of ambient vapor occur every sunny day in which the exterior temperature ex shyceeds about 70ordmF This daily increase in ambient moisture is consistent with the conditions reported in 2006 by the first engineer Further the largest cycles (ie the waves with the greatest amplitude) of infiltrating vapor always occur on hot sunny days (eg August 30) However review of National Weather Service data finds other equally hot and sunny days (eg September 2) in which the amplitude of the moisture wave is relatively moderate thus indishycating that the magnitude of the daily influx is controlled by more than just severity of solar exposure

Investigative Guideline 07 Daily ldquowavesrdquo of water vapor that tend to increase on hot sunny days are caused by solar heating of moisture reservoir(s)

The regularity and daily patterns of the vapor cycles depicted in Figures 9 and 10 are consistent with solar heating of moisture reservoir(s) at or near the building envelope Every hygroscopic (watershyabsorbing) matershyial that is heated by the sun releases water vapor While some hygroscopic roofing or cladding systems are conshystructed with multiple layers of

Haughton shy 113

vaporshyretarding elements that can serve to hinder solarshydriven vapor from reaching the building interior other solarshyheated hygroscopic walls such as concrete and masonry can generate very large vapor drives25

Further the risks of problematic solarshydriven diffusion at concrete walls are exacerbated if they were constructed with a high watershycement ratio26

This naturally occurring ldquovapor driverdquo process can be particularly problematic when roofs or walls have absorbed excess moisture that magnishyfies the solarshycharged amplitudes of the daily waves The inward drive of pressurized vapor tends to leave these hygroscopic building materials dryer than their exterior surrounds leading to replenishment of this missing moisture (via adsorptionabsorption) later that evening and early morning as a natural consequence of the Second Law The entire cycle repeats daily to varying degrees depending on weather conditions and other moisture sources These cycles of increased solarshydriven diffusion easishyly can be identified by the waveshylike shape of average hourly humidity ratio data in Figures 9 and 10 and in Figures 11 through 14)

Investigative Guideline 08 If the general timing shape andor amplitude of vapor cycles from one logger correshyspond to vapor cycles from another logger in a separate space there probably is a direct relationship between the measured conditions

Figure 11 repeats Figure 9 (ie four continuous days of average hourly humidity ratio data from the front datalogger) Figure 12 presents the same four days of information from the office datalogger installed in the adjacent enclosed space The close correspondence of timing shape and amplitude of the daily waves in both graphs clearly demonshystrates that the ambient environshyments in these separate spaces are being affected by solar heating of a

Haughton shy 114

Figure 11ndash Average hourly humidityshyratio results from front datalogger (same data as Figure 9)

Figure 12 ndash Average hourly humidityshyratio results from office datalogger

common moisture reservoir

Now consider Figures 13 and 14 which present data for a different fourshyday period in August 2008 from the front datalogger and the exterior datalogger (Note During this period the interior plastic tarping seen in Photo 9 was not installed) In this case it is only the close corresponshy

dence of the timing and shape of the daily waves in both graphs that demonstrates solar heating of a comshymon reservoir Further in accordance with the Second Law the greater amplitudes of the exterior cycles indishycate that the location of this common reservoir is outside the building

Then consider Figure 15 which


Figure 13 ndash Average hourly humidityshyratio results from front datalogger (beginning 08162008)

Figure 14 ndash Average hourly results from exterior datalogger The greater amplitudes of the daily cycles indicate that a solarshyheated moisture reservoir is located outside the building

graphs weather data from the intershynational irport located only two miles from this vacant building The absence of any close correspondence with the data in Figure 14 confirms that the conditions recorded at the exterior datalogger result from a local solarshyheated reservoir of water

In short comparison of the front datalogger (Figure 13) exterior datashy

logger (Figure 14) and the airport graph at Figure 15 is interpreted by the author as substantive support for his early hypothesis (based upon the initial ldquofindshytheshywaterrdquo survey) that belowshygrade reservoir(s) of water at the front and side elevations of the building were the vaporshygenerating sources of the ambient moisture necshyessary for continuation of the condenshysation events occurring at the ceiling


bull In spring and summer months both the northeast and southeast walls experishyence direct solar heating durshying much of the daylight perishyod however the condensashytion events also were obshyserved on two hot (gt80ordmF) sunny days in November 2008 when only the southshyeast wall experienced direct sunlight

It also is interesting to consider that the front datalogger data in Figure 9 were recorded during the period when the plastic tarping was installed while the front datalogger data in Figure 13 was recorded prior to tarp installation While the limited data in these two graphs certainly is not sufficient to determine if the absence of the plastic tarp greatly affects the amplitude or overall magshynitude of the vapor waves it can be assumed that any solar heating of the uncovered slab will contribute some additional vapor to these daily cycles

Investigative Guideline 09 Be careful when interpreting exterior weather data reported at distant stations

It should not be assumed that weather data reported from distant stations always can serve as a neutral control set when evaluating the potential magnitude of moisture vaporization due to solar heating of wet soil adjacent to a building All wet ground whether due to local irrigashytion or distant rainfall will release water vapor when heated by the sun Evidence of such regular midday vapor release from solarshyheated wet soil can be found in the data reported by many weather stations Weather data from large airports appear to be less affected by this issue likely due to the general absence of unpaved soil however upon review of the local airport data summarized in Figure 15 we still find that the ldquowettestrdquo period during these hot sunny days tends to occur during the early afternoon hours

This advice should not be conshy

Haughton shy 115

strued as a recommendation to avoid using weather data from independent sources instead the investigator simshyply needs to take care when extraposhylating this distant information to help decipher local conditions

SUMMARY DISCUSSION ndash SURVEY PROCESS

In general conformance with the investigative protocol promulgated by ASTM E2128 the author carried out an orderly stepshybyshystep accumulashytion of information in such a manner that each step enhanced and suppleshymented the information gathered in the preceding step A critical goal of this forensic survey was linking cause with effect The investigative process was both inductive and deductive

A cardinal principle of all such qualitative surveys is that their causal conshyclusions must be emershygent from a purposeful series of field observations by a skilled investigator that capitalize on early learning to guide subseshyquent direction toward findings that have subshystantive significance ndash ie a strong meaningful relashytionship27

The results of the survey process for this case demonstrate the use and merits of the following ldquoinvestigative guidelinesrdquo for similar investigations

bull Investigative Guideline 01 Find the source(s) of uninshytended water

bull Investigative Guideline 02 Consider the common origins of unintended water within buildings

bull Investigative Guideline 03 Donrsquot forget the Second Law of Thermodynamics

bull Investigative Guideline 04 Use one or more portable temperatureRH loggers to monitor ambient moisture content over an extended

Figure 15 ndash Hourly humidityshyratio calculations from data reported at nearby international airport Note the lack of correshyspondence with the solarshyheated cycles in Figures 13 and 14

period

bull Investigative Guideline 05 Generally do not position datalogger(s) directly adjashycent to sources of moisture production or intrusion

bull Investigative Guideline 06 Multiple loggers are recomshymended when the goal is to decipher ambient moisture migration from one location to another

bull Investigative Guideline 07 Daily ldquowavesrdquo of water vapor that tend to increase on hot sunny days are caused by solar heating of moisture reservoir(s)

bull Investigative Guideline 08 If the general timing shape and amplitude of vapor cycles from one logger correspond to vapor cycles from another logger in a separate space there probably is a direct relationship between the measured conditions

bull Investigative Guideline 09 Be careful when interpreting exterior weather data reportshy

ed at distant stations

Often the intent of an investigashytive survey is to decipher the basic outlines of an explanation for a buildshying performance puzzle This qualitashytive process is not an equivalent subshystitute for a comprehensive engineershying analysis by a team of building scishyence experts unhindered by the wide variety of time access logistical budshygetary andor legal hurdles commonshyly encountered during preliminary building performance investigations ASTM E2128 acknowledges the many constraints that are placed upon investigators by noting that any conshyclusions or expectations about the substantive significance of their findshyings should be proportional to the defined scope of work and the effort and resources applied to this task28

Upon completion of the survey summarized above the authors findshyings were reported to the owners and their attorney for subsequent evaluashytion by the various experts representshying other parties in the legal dispute The primary goal of this informationshysharing process was to foster general consensus among the experts regardshying the condensation puzzle


bull To this end the building professional must provide a record of the investigashytion and analysis that is sufficiently complete to enable another professhysional to duplicate the intertwined processes of observation sampling and analysishellip29

bull The qualitative analyst presents an argument for substantive significance in the findings of a sumshymary report but subseshyquent reviewers of this expertrsquos analysis also will make their own value judgments about signifishycance In determining substantive significance both the analyst and the reviewers must address these kinds of questions

a How solid coherent and consistent is the qualitative evishydence in support of the expertrsquos findshyings

b To what extent and in what ways do the findings further a deep understanding of the observed conditions

c How well do the findings define and correlate causal relationships in a manner that maxishymizes understandshying of the various processes and pheshynomena of interest that are occurring within the populashytion

d To what extent are the expertrsquos findings consistent with knowledge derived from other sourcesrdquo

SUMMARY DISCUSSION ndash FINDINGS

As noted the goal of this invesshytigative survey simply was to decipher the basic outlines of a reasoned credshyible explanation for the building pershyformance puzzle The accumulated evidence supports a preliminary findshying that solar exposure at the front (southeast) and side (northeast) elevashytions of the building (see Photo 1) serves to heat reservoir(s) of uninshytended water Subsequent daily ldquowavesrdquo of water vapor diffuse through the interior space due to the large pressure differentials created at the solarshyheated concrete walls which terminate below grade at poorshyly drained soil that is regularly irrishygated at the front landscaping The magnitude of these solarshydriven waves may be exacerbated by high porosity of the concrete due to high watershycement ratios during construcshytion of the tiltshyup panels The extent of these vapor waves may be additionshyally affected by solar heating of the concrete flatwork at the front door andor the adjacent area of irrigated soil andor the adjacent asphalt drishyveway Also the author has reviewed preliminary data from the loggers that suggest that the amplitudes of these interior vapor cycles become greater during ldquohumidrdquo summer days (ie those days in which the ambient exteshyrior vapor levels in the San Francisco Bay metropolitan area are elevated)

In accordance with the Second Law these daily waves of ambient water vapor will migrate (via vapor difshyfusion andor air convection) throughout the interior space includshying the ldquodeadrdquo air spaces above the insulation batts at the ceiling While the perimeter ends of many of the batts are taped (see bottom of Photo 4) there are large gaps and voids where the insulation transitions with the structural supports The author further opines that when this large influx of moisture reaches the air space above the sagging insulation condensation will occur on those parshyticular days when the surface tempershyature at the structural steel within these air pockets still remains lower

than the dewpoint temperature of the incoming moisture waves To a great degree the surface temperatures within these insulated dead air spaces will be controlled by minimum nighttime temperatures and the addishytional effects of ldquonight sky coolingrdquo of the roof

The dewpoint temperatures of the moisture waves will be controlled to a great degree by how much vapor has been solarshygenerated on any particushylar day The quantity of new vapor being generated may be controlled primarily by the unknown irrigation schedule and secondarily by the wideshyly varying levels of ambient exterior moisture that can occur in this proshyjectrsquos marine climate (Note The local summer weather is described as ldquosemiarid hellipRainfall is particularly low during the summer monthsrdquo)

In short the likelihood for resultshying condensation is determined by a daily race between the leading edge of the moisture wave and normal warmshying of the surface temperatures withshyin the dead air spaces above the insushylation ndash a short period of vapor conshydensation and resulting damage (see Photo 6) will occur on those hot sunny days in which the wave of ambient vapor wins the race

These survey findings and analyshysis presented an explanation for the condensation puzzle that was suffishyciently reasoned and credible to reopen the legal negotiations foster further expert examination and begin joint evaluations of repair options

To date the repair options that have been jointly reviewed with the defense consultants can be summashyrized as follows a) reduce the water load adjacent to the building via perimeter drainage andor b) apply additional sealers coatings andor belowshygrade waterproofing to hinder moisture infiltration into the building envelope andor c) exfiltrate via mechanical ventilation the excess vapor after it enters the building andor d) redesign or relocate the roof insulation to eliminate the air pockshyets

In similar cases it has been the


authorrsquos opinion that the initial goal for the design team should be to drain the problematic reservoir(s) of belowshygrade water provide an appropriate level of belowshygrade waterproofing and reduce or eliminate unintended sources of excess moisture that re shyplenish these reservoirs Then de shypending on the nature and extent of the performance problems that have been identified the potential merits of other repair options (eg additional ventilation of the interior space or ap shyplication of a fluidshyapplied vapor re shytarder at an onshygrade floor slab or seali ng of breaches in the building en shyvelopersquos air barrier) can be evaluated

FOOTNOTES

1 Note this basic design for installing slightly sagged batt insulation between structural supports at the ceiling is consisshytent with local industry practice and minimally complies with applicable California codes howshyever most experts would recomshymend that the open ends seen in Photos 4 and 5 should be sealed or closed in some manner

2 Condensation a phase change from water vapor to liquid water occurs at the coldest adjacent surface at a dewpoint temperashyture when there no longer is sufshyficient ambient energy to mainshytain all of the existing ambient water molecules in their vapor (gas) form

3 Dr Wahid Maref et al ldquoLabor shyatory Demonstration of Solar Dri ven Inward Vapour Diffusion in a Wall Assemblyrdquo National Research Council Ca na da 11th Canadian Conference on Build ing Science and Tech nology Banff Alberta 2007 (Also reference numerous seminal publications by Dr Joseph Lsti burek and Dr John F Straube at wwwbuildingsciencecom)

4 The calcium chloride test is carshyried out in accordance with ASTM F1869 Test Method for Measuring Moisture Vapor Emis shy

sion Rate of Concrete Subfloor Using Anhydrous Calcium Chlo shyride using a plastic dish conshytaining anhydrous calcium chloshyride under a flanged clear plastic cover sealed to the concrete The dish is weighed prior to the test and then after a period of 60 to 72 hours is weighed again The current moisture vapor emission rate (MVER) at this particular location is calculated with a forshymula that considers the inshycreased weight of the calcium chloride the test time and the surface area inside the plastic cover

5 Typical published vapor emisshysions acceptance limits for floorshycovering systems are 30 lbs or 50 lbs of moisture vapor per 1000 sq ft per 24 hours

6 Many California engineers still require a sand layer above the plastic vapor retarder despite the best efforts of numerous buildshying science experts to explain why this practice can be probshylematic Eg see Dr Joseph Lstiburekrsquos paper ldquoInvestigating and Diagnosing Moisture Prob shylemsrdquo (Building Science Digest 108) at wwwbuildingsciencecom ldquoThe sand layer becomes a resershyvoir for water in the liquid state that enters the sand layer by gravity flow from the top sides and bottomrdquo

7 A proprietary electrical impedshyance meter was used to estimate relative moisture content by sending an electrical signal into the concrete slab and walls ASTM E1907 informs us that the depth of the signal penetration will vary (from 075 inch to 20 inches) depending on the mateshyrial composition and moisture content of the slab

8 ASTM E2128 Standard Guide for Evaluating Water Leakage of Building Walls ASTM Inter shynational West Conshohocken PA

9 L Haughton and C Murphy ldquoQualitative Sampling of the

Building Envelope for Water Leakagerdquo Journal of ASTM International Volume 4 Issue 9 (October 2007) Republished in April 2009 in ASTM STP1493 Repair Retrofit and Inspection of Building Exterior Wall Systems (editors Jon M Boyd and Paul G Johnson)

10L Haughton ldquoQualitative Sam shypling v Statistical Analysis v Daubertrdquo Interface RCI Inc (November 2008)

11WA Rose Water in Buildings ndash An Architectrsquos Guide to Moisture and Mold John Wiley amp Sons Inc 2005

12ldquoWUFIshyORNLIBP is a menushydriven PC program which allows realistic calculation of the transhysient coupled oneshydimensional heatshy and moistureshytransport in multilayer building components exposed to natural weather It is based on the newest findings regarding vapour [sic] diffusion and liquid transport in building materials and has been validated by detailed comparison with measurements obtained in the laboratory and on outdoor testshying fieldsrdquo See wwwornlgov scibtcappsmoistureindex html and wwwhokiibpfhgdewufi bezug_ehtml

13Eg for computer modeling purshyposes at this building what speshycific vapor permeability value should be used for concrete walls that terminate 36 in below grade and after considering typshyical concrete construction pracshytices in Northern California are assumed to have been conshystructed with a high watershycement ratio

14Dr John F Straube ldquoMoisture Con trol in Buildingsrdquo ASHRAE Journal January 2002 and other seminal publications by Dr Straube Dr Joseph Lsti shyburek and others at wwwbuildingsciencecom Also reference Section 11 of ASTM E241 Standard Guide for Limiting WatershyInduced Damage


to Buildings ASTM Internashytional West Conshohocken PA

15 The local summer weather is described by the National Weather Service as ldquosemishyarid hellipRainfall is particularly low durshying the summer monthsrdquo

16 ASTM E1907 Standard Guide to Methods of Evaluating Moisture Conditions of Concrete Floors to Receive Resilient Floor Coverings ASTM International West Con shysho hocken PA

17 The general absence of wideshyspread undershyplastic condensashytion also was confirmed by a humidity logger positioned below the tarping

18 For an excellent discussion re shygarding the perils of irrigated landscaping adjacent to concrete slabs see Dr Joseph Lstiburekrsquos paper ldquoInvestigating and Diagshynosing Moisture Problemsrdquo (Building Science Digest 108) at wwwbuildingsciencecom ldquoThis is a fairly simple problem to diagshynose and fix Stop the water Kill the plants Or move the plants well away from the foundation perimeter so that when they are irrigated the saturated ground is not in contact with the foundashytion hellipFinally dampproof the edge of the slab with an acrylic latex paint or some other dampshyproofing materialrdquo

19 Dr Joseph Lstiburek ldquoInvestishygating amp Diagnosing Moisture Problemsrdquo ASHRAE Journal December 2002 and other semishynal publications by Dr Lstiburek and Dr John Straube at wwwbuildingsciencecom

20 The author commonly uses the

model RHTemp1000 datalogger manufactured by MadgeTech (wwwmadgetechcom) and marshyketed by Omega (wwwomegacom) or the less expensive HOBO U 10 model manufactured by Onset (wwwonsetcompcom) However any portable digital device that accurately can record multiple weeks or months of temperashytureRH data is acceptable For example the RHTemp1000 datashylogger can record 21600 duplex temperatureRH readings at 5shyminute intervals during a 75shyday period

21 For those familiar with a standard ASHRAE psychrometric chart humidity ratios are shown in the vertical (ordinate) axis at the right edge of the chart

22 L Haughton ldquoUsing Humidity Temperature Loggers for Moisture Investigations ndash Case Studiesrdquo RCI Symposium on Building Envelope Technology San Diego CA October 2009

23 With the benefit of hindsight the author believes that selective placement of only two additional loggers could have produced valushyable additional data to better define the timing and paths of travel of the daily moisture events In particular loggers should have been installed above the batt insulation and at floor level immediately inside the front wall

24 The author uses the Get Psychedtrade software by kW Engineering (wwwkwshyenershygycompsychhtm)

25 ldquoIt is clear that any wet material hellipthat is heated by the sun will generate large inward vapour [sic]

drivesrdquo (Dr JF Straube ldquoThe Influence of LowshyPermeance Va shypor Barriers on Roof and Wall Per shyformancerdquo Proceedings of Thermal Performance of Building Envelopes VII Clearwater Beach Florida 2001)

26 Concrete expert George Donnelly (wwwmoisturetest ingcom) ldquoPermeability is governed by porosity which in turn is a direct consequence of the watercement ratio of the original concrete mix design As the watercement ratio increases in linear form the porosity and permeability of the finished concrete product increasshyes exponentiallyrdquo

27 L Haughton and C Murphy ldquoQualitative Sampling of the Building Envelope for Water Leak shyagerdquo Journal of ASTM Internashytional Volume 4 Issue 9 (October 2007) Republished in April 2009 in ASTM STP1493 ndash ldquoRepair Retrofit and Inspection of Building Exterior Wall Systemsrdquo (editors Jon M Boyd and Paul G Johnson)

28 ASTM E2128 Standard Guide for Evaluating Water Leakage of Building Walls ASTM Interna shytional West Conshohocken PA

29 L Haughton and C Murphy ldquoQualitative Sampling of the Building Envelope for Water Leakagerdquo Journal of ASTM International Volume 4 Issue 9 (October 2007) Republished in April 2009 in ASTM STP1493 ndash ldquoRepair Retrofit and Inspection of Building Exterior Wall Systemsrdquo (editors Jon M Boyd and Paul G Johnson)

30 Ibid


ABSTRACT

The speaker will present a case study of a commercial space that has sat empty since its conshystruction due to intermittent hot weather ldquoleakagerdquo from the bottom side of its roof deck Dataloggers confirmed the regular midday appearance within the interior of increased levels of water vapor due to solar heating of the building envelope The location of an unintended resershyvoir of excess water was identified and the process by which condensation resulted at the OSB deck was explained The case study demonstrates that the best approach to such puzzles often is to first ask where the excess water could be located

SPEAKER

Lonnie Haughton uses forensic expertise and a wide range of investigative tools ndash from moisshyture meters to watershyfinding test paper to inshysitu sensors to calcium chloride vapor domes to hygrometers to psychrometric tables to WUFI software ndash to solve leakage and condensation puzzles in California and Nevada Lonnie is a regular contributor to Interface magazine in which he authors informative articles that explore theoretical legal and practical aspects of forensic evaluations of building envelope performance

















gravity vent


































































































Front Door

Northeast













Figure 8)








Figure 5)















Haughton shy 113






Haughton shy 114



















Haughton shy 115











period



























FOOTNOTES




































30 Ibid

















gravity vent


































































































Front Door

Northeast













Figure 8)








Figure 5)















Haughton shy 113






Haughton shy 114



















Haughton shy 115











period



























FOOTNOTES




































30 Ibid

































































































Front Door

Northeast













Figure 8)








Figure 5)















Haughton shy 113






Haughton shy 114



















Haughton shy 115











period



























FOOTNOTES




































30 Ibid



Figure 8)








Figure 5)















Haughton shy 113






Haughton shy 114



















Haughton shy 115











period



























FOOTNOTES




































30 Ibid













Haughton shy 113






Haughton shy 114



















Haughton shy 115











period



























FOOTNOTES




































30 Ibid







Haughton shy 114



















Haughton shy 115











period



























FOOTNOTES




































30 Ibid













Haughton shy 115











period



























FOOTNOTES




































30 Ibid












period



























FOOTNOTES




































30 Ibid



















FOOTNOTES




































30 Ibid




















30 Ibid


Buildings That “Leak” Only on Sunny Days: Case Studies and...

Documents

Transcript of Buildings That “Leak” Only on Sunny Days: Case Studies and...