Biodegradation of Cultural Heritage. State of the Art, Finland

Transcription

1 Bidegradain f Culural Heriage Sae f he Ar, Finland Hannu Viianen VTT Building and Transpr, PB 1806, VTT, Finland 1. Inrducin The bjecive in cnsrucin f buildings has always been make sund and well funcinal buildings. A building, hwever, is a lng-lasing prduc cmpared wih many her uiliy gds, and differen kinds f ageing and damage caused by several reasns may ccur. There is differen ypes f buildings and srucures, and he perfrmance f he whle buildings depends n many facrs: maerials, srucures, caings, envirnmen, climae, ype f use, service ec. The bidegradain f building and maerials is caused by misure exceeding he misure capaciy f maerials and srucures. The service life f a building varies, and in he lng hisry f buildings, differen echnlgy has been inrduced and he prblems in he funcin f hese echnlgies have been seen, unfrunaely, during he use f he buildings. The causes f damage may be cnsrucin errrs, errrs made during repair, r incrrec use, which usually is he resul f missing r pr peraing and service insrucins. Examples frm pas years include defauls in repair and resrain f flrs f ld lg huses, frmaldehyde and radn prblems in indr air. R damage, which may cause srucural prblems, has radiinally been recgnised as a prblem in a building. In general, muld has n been cnsidered be very hazardus, alhugh expers in he field have knwn abu is adverse effecs fr a lng ime. On he her hand, gd, fresh indr air has always been a gal. The echnique aain gd indr air varies, bu surely muld r micrbe grwh have n belnged inside a building in he previus decades. Even very ld guides in he field f cnsrucin have deal wih hese basic quesins. Muld grwh, hwever, has been a naural prcess in uside srucures. 2. Naural aging f he buildings and misure, muld and decay prblems in buildings During he service life f buildings, naural aging f maerials due differen chemical, physical, and bilgical prcesses can ake place. In damage cases, mre severe changes f maerial are assciaed. Wd is a radiinal building maerial in Finland and bideerirain is impran criical facr fr durabiliy f wd and wd based prducs. The service life f imber in a srucure depends primarily upn he humidiy and misure cndiins during he use f wd maerials. The humidiy and emperaure cndiins regulae he presence f wd aacking rganisms. Als naural durabiliy f wd, he prperies f her maerials, preservaives, surface reamens, srucures and mainenance have a significan rle in he aciviy f rganisms and he durabiliy f wden srucures. Muld and decay prblems in buildings are caused by misure damage: waer leakage, cnvecin f damp air and misure cndensain, rising damp frm he grund and misure accumulain in he srucure. During recen years misure prblems in huses seem have been increased in Finland. This can be parly caused by he added knwledge and users are afraid f he prblems. Misure, muld and decay prblems, hwever, can be very cmplicaed in buildings. In buildings, muld fungi cause prblems in differen srucures and maerials: rfs,

2 aics, basemens, flrs and walls. Apar frm wden maerial, surfaces f many her maerials suppr grwh f micrbes and muld prblems are mre cmmn han decay damage. Waer can invade differen ways in building and cause differen prblems, defecs and damages Misure sress humidiy, emperaure, maerial, ime perid MOISTURE DAMAGE lerances are verladed MOULD RH: > % Temp: 0-55 C Time: d, w, m DECAY RH: > % Temp: 5-50 C Time: w, m, y Deecin he damages and simulain he causes f prblems Figure 1. Misure damages are causes muld prblems and decay damages. The ypical rganisms fund in ld buildings r damage cases in Finland are: fungi: mld, bluesain and r fungi baceria: acinbaceria and srepmycees insecs: beeles and ans 2.1 Muld fungi The grwh f muld fungi n maerials in buildings is fen an early indicain f increased humidiy r misure levels, bu he prblems caused by fungi in buildings vary depending n he ype f fungal aack. Prblems caused by muld fungi are mainly disclurain, dur and healh disadvanages. The ypical muld fungi in waer damaged Finnish building are Ascmycees fungi. Alernaria, Acremnium, Aspergillus, Aurebasidium, Fusarium, Oididendrn, Penicillium, Sachybrus, Trichderma species. Muld fungi d n significanly affec he srengh f maerials. The surface f maerials can be damaged caused by he cellullyic aciviy f sme discluring fungi, e.g. Trichderma spp., Aurebasidium pullulans and Ghaemium glbsum. Muld fungi cause several prblems in he buildings: sains, smell, healh prblems. Als in he sund buildings, hwever, muld grwh can be fund n facades, aics and crawlspaces, which are ypical srucures expsed high humidiy cndiins and aack by muld fungi. 2.2 Decay fungi Differen classificains are used fr he decay fungi in pracice. Ofen, hree differen decay ypes are classified and fund als in buildings brwn r, sf r and whie r. Ms f he brwn r and whie r fungi belng Basidimycees, bu sme belng Ascmyces. Ms f he sf r fungi belng Ascmycees and Fungi Imperfeci e.g. Chaemium glbsum and Phialphra hffmannii. In buildings suffering frm excessive misure lading, brwn r is he ms cmmn

3 decay ype. Amng he ypical brwn r fungi which cause he ms serius damage in buildings in emperae climaes are Serpula lacrymans (dry r fungus), her Serpula and Leucgyrphana spp., Cniphra pueana (cellar fungus), differen Anrdia r Pria species, Glephyllum sepiarium, Glephyllum rabeum, Paxillus panuides and Leninus lepideus. Especially he dry r fungus S. lacrymans, which is able ranspr waer hrugh mycelial srands frm he surce f misure in dry wd, has been repred cause large and desrucive damage in buildings and in differen maerials in emperae climae regins, als in Finland. Accrding he sudies perfmed a VTT Building echnlgy, he brwn r fungi, e.g. he dry r fungus Serpula lacrymans and he cellar fungus Cniphra pueana, cause damage especially in flr cnsrucins. In rfs he damage is mre fen caused by muld fungi r her brwn r fungi such as Glephyllum rabeum, G. sepiarium and Fibrpria spp. Hwever, in decay damage, several rganisms are fen invlved: baceria, muld fungi and decay fungi. Baceria and algae are usually firs clnizers f maerials in we cndiins. 2.3 Insecs Wd desrying insecs usually uilize wd as a fdsuff, eiher direcly r indirecly. Many insecs are dependan n parially decayed wd, live in symbisis wih wd desrying fungi. Sme insecs are nly bring wd make ness wihu feeding n i, e.g. carpener ans. In Finland, he Anbidae are he ms serius wd bring beeles. Hadrbregmus cnfusus and Hadrbregmus perinax are ypical beeles in ld wden huses which are aacked by r fungi. Anbium puncaum has becme mre uncmmn when he relaive humidiy f inside air is lwered due beer heaing and venilain sysems in buildings. This beele can n lerae he cld winer in Finland. Hylrubes bajulus exis nly n sme islands f he Turku and Ahvenanmaa archipelag. In Finland he jewel beele Bupresis haemrhidalis and carpener ans cause lcal damages in wden cnsrucins. 3. Managemen f building damages 3.1 Humidiy and misure cnrl In buildings he perfrmance f wd and her maerials is grealy dependan n srucural prvisins. The main principal f srucural precin is eliminae r diminish he risk f fungal decay by designing and mainaining he cnsrucins s ha hey remain cnsanly dry r are allwed dry rapidly afer weing. The misure cnen f wd shuld remain under %. In he cld climae f Finland, bilgical deerirain can hen be alms ally prevened, because he risk f insec aack is small. RH f % is a criical humidiy level fr grwh f muld fungi, bu als emperaure, expsure ime and surface f maerials are impran facrs. RH % is fen criical level fr he develpmen f decay a C. Waer supprs germinain, hyphal grwh and sprulain f fungi. Air humidiy and micrclimae is criical fr sprulain, spre release and survival f spres. The majr facrs affecing he micrclimae are misure migrain and accumulain in maerials, cmpsiin, exure and surface qualiy f he maerial, emperaure, humidiy, waer cndensain and air circulain. In buildings he dry r fungus, hwever, can ranspr waer and cause mre serius damage due he exensive mycelial spread frm a misure surce dry wd. Hwever, dry r fungus is quie sensiive exreme cndiins and he use f high emperaure fr he eradicain f he viable dry r frm huses can be sufficien. Fr undersanding he prcesses f muld and decay in wden maerial, mahemaical mdels are derived a VTT. The mdels describe he risk f muld and decay develpmen in relain humidiy, emperaure and durain f expsure (Figure 2).

4 100 G r w h s p T c l d Muld risk is high m m =4 weeks =8 weeks Muld risk is pssible T h RH [%] T dry Temperaure [ C] Figure 2. Cndiins favurable fr iniiain f muld grwh n wden maerial as a mahemaical mdel. RH, emperaure and expsure ime have be pimal fr develpmen f prblems. Decay can be develped, if RH is abve 90 % r wd misure cnen is abve % fr lnger ime. The principles f srucural precin in wd building have been knwn and fllwed since ld imes. Hwever, hey are smeimes negleced wih resuling decay hazards. Ms misure damage in a building can be avided if a few basic issues are aken in cnsiderain during cnsrucin. Accrding feedback infrmain, we rms, flr srucures, sme rf cnsrucin and he jin beween he fing and he bm edge f exerir walls are he ms difficul places in a building. Careful design, cnsrucin and mainenance f hese srucures will guaranee lng life fr a building. 3.2 Chemical reamens and mdificain prcesses prec maerials The preservain f wd wih chemicals is a cnveninal echnique add he durabiliy f wd. Differen ype f chemicals has been used. Tar and crese ils are very ld preservaives. Tar il is used fr precin f shingle rfs, bas, fences ec. I is acually a surface reamen mehd. In indusrial wd preservain, differen impregnain echnlgies are used. Afer 1950 pressure prcess and waer based chemicals, like CCA preservaives, came in use in Finland. T prec wd agains waer penerain, differen pains and waer repellens has been used. Ochre pains are very permeable pains; il pains are less permeable. Permeabiliy f many mdern acrylae pains is higher han ha f il pains r alkyd il pains, bu he permeabiliy is lwer han ha f chre pains. Waer penerain hrugh a acrylae pain layer is higher han ha hrugh an il pain, which can inrduce prblems in ld facades. During recen years number f sudies and mehd develpmen wrk have been direced apply differen mdificain echnlgy slid wd in rder imprve he durabiliy and behaviur f wd in adverse envirnmens. The mdificain f wd can be direced imprve he dimensinal sabiliy prperies, hardness prperies and/r durabiliy prperies f wd agains decay. Amng he chemical mdificain reacins aceylain is ne f he ms sudied, as his mehd has shwn penial wih minimum adverse side effecs. Als resin cmpunds and ar il derivaives has been sudied.

5 Hea reamen f wd is very ppular pic in Finland and in Eurpe a he mmen. The basic f his echnlgy is acually very ld: wd was fire reaed already in ancien imes. Nw research is carried u in he field by several Eurpean cunries, research insiues and indusrial paries. Als new bicide reamens have been sudied. Accrding research resuls, argeed bicides prvide an efficien l fr designing f wd preservain. Targeed wd precin is efficien, safe in use, have lw envirnmenal impac and is designed ms suiable end use. 3.3 Srucures We rms and flrs In we rms waer is ms fen peneraed hrugh inside surface r pipe leakage in he srucures. Gd waerprfing is essenial regardless f wheher he building is made f sne r wd. The walls and flr mus be waerprf, which means jins and inles mus be carefully sealed. Gd venilain during and afer use f he rm remves misure ha places a sress n he surfaces in he rm. In ld buildings, he malfuncin f we rms has caused severe muld, decay and insec prblems. In he ld wden buildings in Finland, he flr is fen based n a cld venilaed basemen. The flr f living rms shuld be sufficienly high abve he surface f he grund arund he building and he fundain and surrundings f he building shuld be kep as dry as pssible. If waer is peneraed in he crawl base, he venilain may n keep he flr dry. If venilain caps are clsed, severe decay prblems have been fund, e.g. dry r damage. The grund base flr is used in he ld buildings. This ype a flr is very sensiive fr waer damage and micrbial grwh. In he newer buildings, wden beams are fen based n cncree slab n grund. As insulain maerials, mss, wd chips r mineral wl is ms fen used. This ype f srucure is fen sensiive fr misure sress, and muld r decay damages has fen been fund due waer damage. Fr beer funcin, he grund slab srucures shuld have a leas 50 mm f insulain belw he bm cncree slab. Waerprfing maerial, such as biumen fel, shuld be placed beween wden and cncree pars. In cnjuncin wih repair, bricks r cncree blcks shuld be used raise he wden suppring rails f a wd flr abve he level f he lwer cncree slab. Waerprf maerial shuld als be placed beween he brick r cncree blck and he wd srucure. The wden pars f inerir walls shuld always be abve he finished flr and insulaed frm he cncree belw by means f srips f biumen Exerir walls and rf Parial decay r insec damage is fen fund in he lwer beam f exerir wall due waer penerain frm he basemen. Waerprfing maerial shuld be placed beween he bm beam f he wall and he basemen. The lwer srucures f he exerir walls shuld n cme in cnac wih he cncree r sand uside. Regardless f he srucure f he exerir wall, a funcinal venilain space shuld be lef a he bm edge f he wall allw air pass hrugh he venilain space behind he facade. In ld buildings, hwever, n venilain space exiss. The waer vapur resisance f he maerial layer n he warm side f an pen prus hermal insulain layer shuld be five imes higher han ha n he cld side. I is necessary have a genuine air barrier in he envelpe in rder be able cnrl he pressure cndiins in buildings and avid he harmful waer vapur cnvecin frm indr air he envelpe. A building s funcinal rf and rf srucure prec he building agains rain. Rainwaer is, hwever, fen peneraed hrugh he exerir wall in he inside srucure. Wide eaves, lng guers and rainwaer drainage sysems prec he walls agains waer damage risk. Inles, differen levels, ridges and valleys f a rf are penial places f damage. Insallain f an air barrier is always recmmended in a wden rf srucure. In he Finnish climae i is ypical ha muld grwh can begin in he auumn n he wden surfaces in cnac wih udr air, when

6 he emperaure and relaive humidiy are high enugh. The resuls f VTT shw ha, in ms buildings, minr muld grwh can be fund in cld pars f srucures regardless f he maerials used Indr air There has recenly been discussin abu air permeabiliy f buildings. Inside air qualiy, hwever, is primarily dependen n he venilain sysem f a building. Regardless f wha kind f venilain sysem is used, i mus be capable f exchanging a sufficien amun f air preven hazardus subsances frm accumulaing indrs. This is very impran especially in cld climae, and cnrlled air venilain is needed save he energy cnsumpin. If he inerir surface f a building is made f prus maerial, such as wd r cnsrucin sheeing, hey may accumulae misure and pssibly her gaseus subsances. This can have an effec n he inside air qualiy. A prerequisie is, ha he surface shuld n be caed r reaed wih an impenerable maerial, such as a pain. Wden maerial in ineracin wih indr air will balance he variain f indr air humidiy when misure lad is varying. Accrding presen knwledge in Finland, hwever, he bes siuain frm he sandpin f venilain is cnrlled enry f fresh, clean air in he rms f a building and cnrlled exhaus f used air. Cnrl f venilain is imprved if he uer shell is airigh, which means an airigh layer inside (an air barrier) and a wind barrier n he uside. 4. A building is an individual and whle uni Frm he sandpin f he funcining f a building, i is impran design, cnsruc and repair a building wih verall funcinaliy in mind. The srucures shuld be funcinal, bu he venilain sysem, plumbing sysem and aumain shuld suppr verall funcinaliy. Even hugh separae pars and devices f a building funcin well independenly, his des n guaranee prper funcining f he whle prduc. In his sense, simple, clear peraing and service insrucins are n he leas impran maers. They shuld be included in all ypes f buildings. Mainenance and upkeep are impran frm he sandpin f lng-erm funcinaliy f a building. Ms impran is prevenive mainenance, which helps in eliminaing undesirable facrs befrehand. Misure and bilgical damages in buildings are echnical prblems and herefre he expers f he building field mus be used in sudying and repairing hem. In he ms difficul cases, he cperain f differen paries (expers f he building field, healh and building auhriies and bilgy expers) is required. A repair plan f misure and decay damages in buildings shuld be made based n he acquired infrmain: hw he cause f he damage shuld be remved and hw furher damage shuld be prevened, hw exensive he repair wrk will be, wha shuld be repaired and hw. This will require clse c-perain beween expers, research scienis and cmpanies. The design f srucural sluins and prper maerial chice, bh fr new and ld buildings, needs be develped in he fuure. Als prper analyses and reparain echnlgy f muld, decay and insec damages are needed. Then i wuld be pssible agree use nly a gd and prven basic sluins. In Finland, he Minisry f he Envirnmen s new misure regulains and direcives (C2) and relaed applicain insrucins will prvide a gd base fr cnsrucing buildings ha wihsand misure. Fr prevenin f muld and decay reparain, several echniques can be and have been used. 5. References [1] Hukka, A. and Viianen, H A mahemaical mdel f muld grwh n wden maerial. Wd Science and Technlgy 33 p

7 [2] Kkk, E., Ojanen, T., Salnvaara, M., Hukka, A ja Viianen, H Puurakeneiden kseusekninen imina (Misure physical behaviur f wden srucures). VTT Tiedeia, VTT Research Nes. 1991, 160 p. [3] Kääriäinen, H. Ranamäki, J and Tulla, K. Misure Perfrmance f Wden Buildings. Feedback Knwledge f Acual Buildings Esp: Technical Research Cenre f Finland. 85 p. (VTT Research Nes 1923). 63 p. + appendices 14 p. (in Finnish) [4] Paajanen, L. & Viianen, H. Decay fungi in Finnish huses n he basis f inspeced samples frm Sckhlm. Inerna. Res. Grup n Wd Pres., Dc. N: IRG/WP/ p. [5] Paajanen, L., Rischkff, A. and Viianen, H Effec f insulain maerials n he bideerirain f buildings. Esp. VTT Julkaisuja p. + app. 8 p. (Finnish, English Absrac) [6] Rischkff Anne-Chrisine; Viianen, Hannu; Kskela, Kyösi. The respnse f building maerials he muld expsure a differen humidiy and emperaure cndiins Healhy Buildings Esp, FI, 6-10 Aug Seppänen, O. & Säeri, J. (ed). Vl. 1. Finnish Sciey f Indr Air Qualiy and Climae (FiSIAQ) (2000), s [7] Sikkeli, A. A sudy n he lng-erm durabiliy f exernal wd claddings in Finland. In: Sikkeli, A. (ed.). Managemen f Eurpean building heriage. Universiy f Oulu (2000), s [8] Tulla K. Misure perfrmance f wden buildings. Feedback infrmain and repair f damages. In: Sikkeli, A (ed,) Managemen f he Eurpean wden building heriage. Univerisy f Oulu, Deparmen f Archiecure. p [9] Viianen, H Facrs affecing he develpmen f bideerirain in wden cnsrucins. Maerials and Srucures 27, [10] Viianen, H. Facrs affecing he develpmen f muld and brwn r decay in wden maerial and wden srucures. Effec f humidiy, emperaure and expsure ime. The Swedish Universiy f Agriculural Sciences. Uppsala, [11] Viianen H. 1997a. Mdelling he ime facr in he develpmen f muld fungi - Effec f criical humidiy and emperaure cndiins in pine and spruce sapwd. Hlzfrschung, Vl 51, N 1, p [12] Viianen H. 1997b. Mdelling he ime facr in he develpmen f brwn r decay in pine and spruce sapwd - he effec f criical himidiy and emperaure cndiins. Hlzfrschung 51, N 2, p [13] Viianen H. & Bjurman J Muld grwh n wd a flucuaing humidiy cndiins. Ma. und Org. 29(1): [14] Viianen, Hannu; Tulla, Kauk. Cndiin managemen sysems fr wden buildings In: Sikkeli, A. (ed.). Managemen f Eurpean building heriage. Universiy f Oulu (2000), s [15] Viianen, Hannu; Hanhijärvi, Ani; Hukka, Ani; Kskela, Kyösi Mdelling muld grwh and decay damages Healhy Buildings 2000: Design and Operain f HVAC Prceedings. Esp, 6-10 Augus Vl. 3. SIY Indr Air Infrmain Oy (2000), s [16] Viianen, H. & Pulkkinen, M The wd aacking insecs in wden huses f a ld pen air museum in suhern Finland. The Inernainal Research Grup n wd Preservain. IRG Dc. N: IRG/WP/ p.