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Biological growth on rendered façades

Johansson, Sanne LU (2011) In Report TVBM 1029
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)
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)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof.Dr. Karsten, Ulf, Institut für Biowissenschaften (IfBi), Lehrstuhl Angewandte Ökologie, Universität Rostock, Rostock, Germany
organization
publishing date
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 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
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
2011-05-19 14:13:32
date last changed
2016-09-19 08:44:50
@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},
  keyword      = {temperature,render,radiation,photosynthesis,moulds,mosses,mortar,moisture,lichens,Imaging-PAM,humidity,heat capacity,heat,ETICS,algae,biological growth,calorimetry,desiccation tolerance},
  language     = {eng},
  pages        = {78},
  publisher    = {Lund University, Division of Building Materials},
  school       = {Lund University},
  series       = {Report TVBM 1029},
  title        = {Biological growth on rendered façades},
  year         = {2011},
}