Biological growth on rendered façades
(2011) In Report TVBM 1029.- Abstract
- Biological organisms have an incredible ability to adapt to almost any
environment and the humans activities on earth have created many
new habitats for different kinds of organisms. For example can certain
organisms grow on rocks and vertical cliffs, and when humans
started building houses with mineral based façades, some organisms
found that these were new habitats to live on. Some of these expansions
of habitats to our houses are not desirable for the us humans and
are considered as “contaminations". Even if this contamination sometimes
only is an aesthetically problem, some contamination is highly
unwanted because it can be unhealthy for the inhabitants -... (More) - Biological organisms have an incredible ability to adapt to almost any
environment and the humans activities on earth have created many
new habitats for different kinds of organisms. For example can certain
organisms grow on rocks and vertical cliffs, and when humans
started building houses with mineral based façades, some organisms
found that these were new habitats to live on. Some of these expansions
of habitats to our houses are not desirable for the us humans and
are considered as “contaminations". Even if this contamination sometimes
only is an aesthetically problem, some contamination is highly
unwanted because it can be unhealthy for the inhabitants - for example
the growth of moulds - or it can degrade the building materials it
grows on -as for example wood-degrading fungi.
For an organism to grow in a certain environment, different requirements
on abiotic (physical and chemical) and biotic (biological) factors
have to be fulfilled. Suitable conditions for growth of organisms
on façades are certain ranges in temperature and a high moisture level
(RH), but also the surface structure, nutrient availability, pH, cardinal
direction etc. might be influencing. Different organisms have different
demands on these factors and it is a complex interaction of these
different factors that decides if an organism can grow in a certain environment.
The last decades many houses in Sweden have been built with constructions
of thin rendering on thermal insulation, a so called ETICS
construction (External Thermal Insulation Construction System). This
construction consist most often of a framework of wooden studs with
thermal insulation in between, and gypsum boards or cement based
boards on both sides. On the outside a thermal insulation layer is applied
and the render is then applied directly on the outside of this thermal
insulation layer. This is a an efficient and compact construction
which is easy to produce. However, many of these constructions have
experienced discolourations from growth of algae and moulds on the
façades already a few years after construction. It has not always been
possible to explain this discolouration. Sometimes one part of the
façade had discolorations and another part of the same façade did not.
One possible explanation for the fast growth of organisms is the
external rendering layer (on thermal insulation that has a low heat capacity
and during night the long-wave radiation from the material to
the sky can contribute to a lower temperature on the surface than the
temperature in the air -on clear nights, when the heat loses through
long-wave radiation is high. The lowered surface temperature then
causes the RH on the surface to increase, sometimes giving condensation
-which increases the risk of biological growth.
In this project we have compared temperatures and RH on surfaces
on façade elements in a test house with constructions with low heat
capacity in the outermost layer (light walls) and constructions with
a high heat capacity in the outermost layer (heavy walls). Simulations
of the growth risk showed that thin rendering on thermal insulation
has a higher growth risk that traditionally render on bricks especially
on the north side. On the south side the most important factor
was the surface colour. In our study we compared a red and a white
surface, and since dark surface colours absorbs more short-wave radiation
from the sun they have a higher temperature during daytime
and therefore a lower RH on the surface.
Another factor which might influence the growth risk is the surface
structure of the render. We fabricated specimens with different
renders with different surface structures and with a thin and thick
rendering layer (3mm and 20mm, respectively) and exposed the specimens
outdoors for four years. This study showed that algaes preferred
a very rough surface structure while moulds (Cladosporium sp.)
also grew on more smooth surfaces. In addition we found that algaes
most often grew on the north side whereas moulds rather grew on the
south side (Cladosporium has a dark pigment in the cells which protects
against radiation from the sun). Furthermore we found a connection
between the amount of growth and the season of the year. The
biological growth was more clearly seen during spring and especially
autumn and occasionally seemed to disappear during summer and
winter. It was found that thin (3-4mm) and thick (20mm) render on
thermal insulation had the same amount of discolouration.
The activity of photosynthetic organisms -algae, lichens and mosseson
façades can be measured with Imaging-PAM. This is an instrument
that measures the chlorophyll fluorescence and gives an indirect measure
of photosynthetic activity. A pilot study was performed where
we -during three days in the autumn- studied algae and mosses growing
on render. Algae dries out easily and is dependent of moisture
from the surroundings and showed the highest activity during mornings
before the sun dried them out. The mosses were active a greater
part of the day; they are able to some extent store water in their leaves
and is not as dependent on moisture from the surroundings as algae.
Another method for measuring activity of biological organisms is
isothermal calorimetry which measures the produced heat from an
organism’s metabolism. In this project we tested a new type of calorimeter
that measures activity at four different temperatures at the same
time. With measurements of a moss (Tortula ruralis) we found that it
was possible to get an activity measure at four different temperatures
at the same time, thus being able to get an understanding of how the
temperature influences the activity. This method should therefore be
very useful in future studies of activity of different types of biological
organisms.
The aim of this project was to investigate constructions of thin rendering
on thermal insulation and the biological organisms growing on
the façades of these constructions. With a multidisciplinary approach
we have increased the knowledge of the façade as a habitat, the organisms
growing, and their interactions with different biotic and abiotic
factors. (Less) - Abstract (Swedish)
- Popular Abstract in Swedish
Biologiska organismer har en fantastisk förmåga att anpassa sig till alla
möjliga miljöer. Människans aktiviteter på jorden har skapat många
nya habitat för olika typer av organismer; t ex kan vissa organismer
växa på sten och vertikala klippor och när människor bygger hus
så kan dessa organismer flytta över till väggar och tak som blir nya
biotoper att leva på. Några av dessa habitatutbredningar till våra hus
är dock inte önskvärda för oss människor och betraktas som en "kontamineringäv
våra byggnader. Även om denna kontaminering till stor
del är ett estetiskt problem, finns det påväxt som är oönskad eftersom
den är... (More) - Popular Abstract in Swedish
Biologiska organismer har en fantastisk förmåga att anpassa sig till alla
möjliga miljöer. Människans aktiviteter på jorden har skapat många
nya habitat för olika typer av organismer; t ex kan vissa organismer
växa på sten och vertikala klippor och när människor bygger hus
så kan dessa organismer flytta över till väggar och tak som blir nya
biotoper att leva på. Några av dessa habitatutbredningar till våra hus
är dock inte önskvärda för oss människor och betraktas som en "kontamineringäv
våra byggnader. Även om denna kontaminering till stor
del är ett estetiskt problem, finns det påväxt som är oönskad eftersom
den är skadlig för invånarna - mögelsvampar - eller bryter ner materialet
de växer på - rötsvampar.
För att organismer ska kunna växa i en viss miljö skall olika krav
på abiotiska (fysikaliska och kemiska) och biotiska (biologiska) faktorer
var uppfyllda. Essentiella faktorer för påväxt på husfasader är
temperatur och relativ fuktighet (RF), men också ytstruktur, tillgång
till näring, pH och väderstreck påverkar. Olika organismer har olika
krav till dessa faktorer och det är ett samspel mellan alla dessa faktorer
där avgör om en organism kan växa i en given miljö.
De senaste årtiondena har många hus blivit byggda med en konstruktion
av så kallad tunnputs på isolering. Konstruktionen består
ofta av en träregelstommer med isolering mellan reglarna och gipseller
cementbaserade skivor på båda sidorna. På utsidan finns ett isoleringsskikt
och putsen fästas direkt på utsidan av detta skikt. Detta
är en effektiv och kompakt konstruktion som är enkel att bygga,
men den saknar ett dränerande och ventilerande skikt. Det har visat
sig att många av dessa konstruktioner har fått påväxt av alger och
mögelsvampar på fasaderna redan några år efter konstruktion. Det
har dock inte alltid varit möjligt att fastställa orsakerna till denna
snabba påväxt. Dessutom kan en del av en fasad kan ha påväxt, medan
en annan del inte har det.
En möjlig förklaring till snabb påväxt på puts på isolering är att
dessa putsskikt har minimal värmekapacitet och då bidrar nattutstrålningen
från putsen att yttemperaturen blir lägre än luftens temperatur
- särskilt i samband med klara nätter, där natutstrålningen är hög. Den
lägre yttemperaturen orsakar då hög RF på ytan och ibland också
kondens - vilket ger hög risk för påväxt. I detta projekt har vi jämfört
temperatur och RF på ytor av konstruktioner i ett provhus med
låg värmekapacitet i ytskiktet (lätta väggar) och konstruktioner med
högre värmekapacitet (tunga väggar). Simuleringar av påväxtrisken
visade att fasader med låg värmekapacitet hade signifikant högre ytfuktighet
jämfört med fasader med högre värmekapacitet och därmed
har tunnputsfasader högre risk för påväxt. Detta gäller framförallt på
norrsidan. På södersidan var färgen på ytan av stor betydelse. I vårt
försök jämförde vi en röd och en vit yta, och eftersom mörka ytor absorberar
mera solstrålning har de därför en högre medeltemperatur
och därmed lägre RF på ytan.
En av de andra faktorerna som visat sig ha stor betydelse för påväxtrisken
är strukturen på putsens yta. Vi tillverkade putsprovkroppar
av olika putstyper och putsstuktur och med tunn och tjock puts och
exponerade dessa utomhus i 4 år. Studien visade att alger fördrog en
mycket grov ytstruktur medan mögelsvampar (främst av släktet Cladosporium)
helst växte på mer släta ytor. Dessutom växte alger oftast
på norrsidan medan mögelsvamparna växte på södersidan (Cladosporium
har det mörka färgämnet melanin i cellväggarna som skyddar
mot solstrålning). Därutöver sågs ett mönster i påväxtgraden efter
årstiderna. Påväxten - vare sig det var mögel eller alger - sågs tydligare
under vår och höst, och såg ibland ut att försvinna under sommar
och vinter. Vi fann ingen skillnad i påväxt mellan tunna (3mm)
och tjocka (20mm) putser på isolering.
Aktiviteten hos fotosyntesaktiva organismer - alger och lavar på
fasader - kan mätas med Imaging-PAM. Detta är ett instrument som
mäter klorofylfluorescens och ger ett indirekt mått på fotosyntesaktivitet.
Ett pilotförsök utfördas med Imaging-PAM där vi under tre
dagar under hösten mätte fotosyntesaktivitet hos alger och mossor
som växte på puts. Alger torkar lätt ut och är helt beroende av fukt
från omgivningen och visade högst aktivitet under förmiddagen innan
solen torkade ut dem. Mossorna var aktiva under större delen av
dygnet; eftersom de bättre kan hålla vatten i sina blad är de inte så
beroende av direkt fukt från omgivningen.
En annan metod att mäta aktiviteten hos biologiska organismer
är isoterm kalorimetri som mäter värmen som utvecklas vid organismers
metabolism. I denna studie testade vi en ny typ av kalorimeter
som kan mäta aktivitet vid fyra olika temperaturer samtidigt. Med
mätningar på en mossa (takmossa, Tortula ruralis) visade det sig möjligt
att få ett aktivitetsmått vid fyra olika temperaturer samtidigt och på
så snabbt bilda sig en uppfattning om hur aktiviteten beror på temperaturen.
Metoden bör därför vara mycket användbar för framtida
aktivitetsmätningar på olika typer biologiska organismer.
Syftet med projektet bakom denna avhandling är att undersöka
tunnputskonstruktioner och de biologiska organismer som växer på
fasaderna. Med ett multidisciplinärt tillvägagångssätt har vi ökat kunskapen
om fasaden som en biotop, de organismer som växer där, och
deras samspel med olika biotiska och abiotiska faktorer (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1963550
- author
- Johansson, Sanne LU
- supervisor
-
- Lars Wadsö LU
- Kenneth Sandin LU
- opponent
-
- Prof.Dr. Karsten, Ulf, Institut für Biowissenschaften (IfBi), Lehrstuhl Angewandte Ökologie, Universität Rostock, Rostock, Germany
- organization
- publishing date
- 2011
- type
- Thesis
- publication status
- published
- subject
- keywords
- temperature, render, radiation, photosynthesis, moulds, mosses, mortar, moisture, lichens, Imaging-PAM, humidity, heat capacity, heat, ETICS, algae, biological growth, calorimetry, desiccation tolerance
- in
- Report TVBM
- volume
- 1029
- pages
- 78 pages
- publisher
- Lund University, Division of Building Materials
- defense location
- Lecture hall V:B, V-building, John Ericssons väg 1, Lund University Faculty of Engineering
- defense date
- 2011-06-16 13:15:00
- external identifiers
-
- other:TVBM-1029
- ISSN
- 0348-7911
- ISBN
- 978-91-7473-127-9
- language
- English
- LU publication?
- yes
- id
- 03f68734-3706-438b-967d-41c4afdfc6f7 (old id 1963550)
- date added to LUP
- 2016-04-01 14:39:21
- date last changed
- 2019-05-23 17:18:36
@phdthesis{03f68734-3706-438b-967d-41c4afdfc6f7, abstract = {{Biological organisms have an incredible ability to adapt to almost any<br/><br> environment and the humans activities on earth have created many<br/><br> new habitats for different kinds of organisms. For example can certain<br/><br> organisms grow on rocks and vertical cliffs, and when humans<br/><br> started building houses with mineral based façades, some organisms<br/><br> found that these were new habitats to live on. Some of these expansions<br/><br> of habitats to our houses are not desirable for the us humans and<br/><br> are considered as “contaminations". Even if this contamination sometimes<br/><br> only is an aesthetically problem, some contamination is highly<br/><br> unwanted because it can be unhealthy for the inhabitants - for example<br/><br> the growth of moulds - or it can degrade the building materials it<br/><br> grows on -as for example wood-degrading fungi.<br/><br> For an organism to grow in a certain environment, different requirements<br/><br> on abiotic (physical and chemical) and biotic (biological) factors<br/><br> have to be fulfilled. Suitable conditions for growth of organisms<br/><br> on façades are certain ranges in temperature and a high moisture level<br/><br> (RH), but also the surface structure, nutrient availability, pH, cardinal<br/><br> direction etc. might be influencing. Different organisms have different<br/><br> demands on these factors and it is a complex interaction of these<br/><br> different factors that decides if an organism can grow in a certain environment.<br/><br> The last decades many houses in Sweden have been built with constructions<br/><br> of thin rendering on thermal insulation, a so called ETICS<br/><br> construction (External Thermal Insulation Construction System). This<br/><br> construction consist most often of a framework of wooden studs with<br/><br> thermal insulation in between, and gypsum boards or cement based<br/><br> boards on both sides. On the outside a thermal insulation layer is applied<br/><br> and the render is then applied directly on the outside of this thermal<br/><br> insulation layer. This is a an efficient and compact construction<br/><br> which is easy to produce. However, many of these constructions have<br/><br> experienced discolourations from growth of algae and moulds on the<br/><br> façades already a few years after construction. It has not always been<br/><br> possible to explain this discolouration. Sometimes one part of the<br/><br> façade had discolorations and another part of the same façade did not.<br/><br> One possible explanation for the fast growth of organisms is the<br/><br> external rendering layer (on thermal insulation that has a low heat capacity<br/><br> and during night the long-wave radiation from the material to<br/><br> the sky can contribute to a lower temperature on the surface than the<br/><br> temperature in the air -on clear nights, when the heat loses through<br/><br> long-wave radiation is high. The lowered surface temperature then<br/><br> causes the RH on the surface to increase, sometimes giving condensation<br/><br> -which increases the risk of biological growth.<br/><br> In this project we have compared temperatures and RH on surfaces<br/><br> on façade elements in a test house with constructions with low heat<br/><br> capacity in the outermost layer (light walls) and constructions with<br/><br> a high heat capacity in the outermost layer (heavy walls). Simulations<br/><br> of the growth risk showed that thin rendering on thermal insulation<br/><br> has a higher growth risk that traditionally render on bricks especially<br/><br> on the north side. On the south side the most important factor<br/><br> was the surface colour. In our study we compared a red and a white<br/><br> surface, and since dark surface colours absorbs more short-wave radiation<br/><br> from the sun they have a higher temperature during daytime<br/><br> and therefore a lower RH on the surface.<br/><br> Another factor which might influence the growth risk is the surface<br/><br> structure of the render. We fabricated specimens with different<br/><br> renders with different surface structures and with a thin and thick<br/><br> rendering layer (3mm and 20mm, respectively) and exposed the specimens<br/><br> outdoors for four years. This study showed that algaes preferred<br/><br> a very rough surface structure while moulds (Cladosporium sp.)<br/><br> also grew on more smooth surfaces. In addition we found that algaes<br/><br> most often grew on the north side whereas moulds rather grew on the<br/><br> south side (Cladosporium has a dark pigment in the cells which protects<br/><br> against radiation from the sun). Furthermore we found a connection<br/><br> between the amount of growth and the season of the year. The<br/><br> biological growth was more clearly seen during spring and especially<br/><br> autumn and occasionally seemed to disappear during summer and<br/><br> winter. It was found that thin (3-4mm) and thick (20mm) render on<br/><br> thermal insulation had the same amount of discolouration.<br/><br> The activity of photosynthetic organisms -algae, lichens and mosseson<br/><br> façades can be measured with Imaging-PAM. This is an instrument<br/><br> that measures the chlorophyll fluorescence and gives an indirect measure<br/><br> of photosynthetic activity. A pilot study was performed where<br/><br> we -during three days in the autumn- studied algae and mosses growing<br/><br> on render. Algae dries out easily and is dependent of moisture<br/><br> from the surroundings and showed the highest activity during mornings<br/><br> before the sun dried them out. The mosses were active a greater<br/><br> part of the day; they are able to some extent store water in their leaves<br/><br> and is not as dependent on moisture from the surroundings as algae.<br/><br> Another method for measuring activity of biological organisms is<br/><br> isothermal calorimetry which measures the produced heat from an<br/><br> organism’s metabolism. In this project we tested a new type of calorimeter<br/><br> that measures activity at four different temperatures at the same<br/><br> time. With measurements of a moss (Tortula ruralis) we found that it<br/><br> was possible to get an activity measure at four different temperatures<br/><br> at the same time, thus being able to get an understanding of how the<br/><br> temperature influences the activity. This method should therefore be<br/><br> very useful in future studies of activity of different types of biological<br/><br> organisms.<br/><br> The aim of this project was to investigate constructions of thin rendering<br/><br> on thermal insulation and the biological organisms growing on<br/><br> the façades of these constructions. With a multidisciplinary approach<br/><br> we have increased the knowledge of the façade as a habitat, the organisms<br/><br> growing, and their interactions with different biotic and abiotic<br/><br> factors.}}, author = {{Johansson, Sanne}}, isbn = {{978-91-7473-127-9}}, issn = {{0348-7911}}, keywords = {{temperature; render; radiation; photosynthesis; moulds; mosses; mortar; moisture; lichens; Imaging-PAM; humidity; heat capacity; heat; ETICS; algae; biological growth; calorimetry; desiccation tolerance}}, language = {{eng}}, publisher = {{Lund University, Division of Building Materials}}, school = {{Lund University}}, series = {{Report TVBM}}, title = {{Biological growth on rendered façades}}, url = {{https://lup.lub.lu.se/search/files/4086826/1963564.pdf}}, volume = {{1029}}, year = {{2011}}, }