Moisture content and heat-insulating properties of building materials

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NATICiAL, i G S W H COUiJCIL OF CANADA

JdOISTUiZE CCNTENT AIJD HEAT

-

IKSULATING PRCPERTIES

(Fuktighet och VKrmeisoleringsf8r1~a~a hos Byggnadsmaterial)

translated by

H. A. G. Nathan

This i s the Sixth o f the S e r i e s o f Translations Prepared f o r the Division o f Building Research,

Ottawa

PREFACE

The National Research Council through i t s D i v i s i o n o f B u i l d i n $ Research h a s a c l o s e l i n k w i t h b u i l d i n g r e s e a r c h work i n Sweden f o l l o w i n g a v i s i t by t h e w r t e r t o Sweden i n 1948, C l i m a t i c c o n d i t i o n s i n Sweden a r e similar t o t h o s e i n Canada and i t i s hoped t o deve op f r u i t f u l l i a i s o n between t h e b u i l d i n g r e s e a r c h vork i n t h e two c o c m t r i e s ,

It i s t h e r e f o r e a p l e a s u r e to have t h i s t r a n s l a t i o n of the Swedish a r t i c l e on b u i l d i n g m a t e r i a l s pu l i s n e d

by t h e Council, It d e a l s w i t h a m a t t e r o f e ~ u 2 . l i n p o r t a n c e i n Sweden and i n Canada and p r e s e n t s u s e f u l i n f o r m a t i ~ n which i s n o t u n r e l a t e d t o Canadian c o n d i t i o n

.

T r a n s l a - t i o n i s published w i t h t h e a p p r o v a l o f t h e aubhor k i n d l y o b t a i n e d f o r t h e C o u n c i l through W, B o r i s Blomgren, S e c r e t - a r y o f t h e S t a t e n s Komnittee f o r 3yGgnadsforskningo Robert F, Legget, D i r e c t o r , D i v i s l o n o f B u i l d i n g Research,

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MOISTURE CONTENT

AND

HEAT-INSULATING PROPERTIES OF BUILDING MATERIALS Is the effect of moisture content on the heat-insulating properties of building materials sufficiently taken into account?

It is generally known that moisture has a detrimen- tal influence on the effectiveness of all insulating materials, Therefore, an allowance for safety is added to the thermal

conductivity value obtained from tests of materials in the dry state,

Insufficient knowledge of the moisture oontent which actually exists in a building material, and lack of a suffic- iently large number

~f

results obtained from tests under

different moisture conditions have shown that there is still great uncertainty concerning the margin of safety to be

allowed,

It is also very difficult to obtain a definite value for the thermal conductivity of a building material with a given moisture content. Care must be taken that the distribu- tion of the moisture content during the test is the same as that of the material in use.

In

the method used at present in Sweden (the material being tested between two metal plates at different temperatures) this requirement is hardly ever taken into account. According to the "theory for cold wallst' the moisture passes over to the cold surface of the material where it accumulates in front of the metal plate, while the rest of the material more or less dries out, depending on the time required to attain steady state test conditionso Since ft takes a certain time to attain steady state heat flow con- ditions before test results can be read, abnormal displacement of moisture is encountered, even in the most favourable case, Since displacement of the moisture towards the cold surface continues throughout the whole test, then the longer the test lasts the more favourable the results will be, This fact, among others, caused the present author to make a test at the Statens Provningsanstalt, the results of which have been

placed on record,

It is clear therefore that either the values obtained must be converted to those for uniform moisture distribution or a different experimental set-up must be used to test moist materialso A correct conversion requires more lengthy systema-

Page , - 2 TT-95

Dro Ing h a b i l o J o S C a m e r e p , T u t e i n g , and P r c f ,

DHD, I n g o Q 1 K r i a c h s ~ , Munich, r e e o m e n d an a p p a ~ a t u s i n which t h e c o l d s u r f a c e o f t h e t e s t specimen i s exposed t o a f ~ n o t s a t u r a t e d wf t i 1 mof s t u ~ e , s o t h a t eqrs.poratf a n can t a k a p l a c e , a s a c t u a l l y o c c u r s f ~ o m external wallsJ With t h i s method t h e change i n t h e m s i a t u ~ e c o n t e n t can be determined when each

r e a d i n g i s made, 'The t e m p e r a t u r e d i P f a r e n c s a t t h e two a u ~ f a c e s should be a s s m a l l a s possfPLe and t h e c o l d s u r f a c e should n o t be a t f r e e z i n g t e m p e ~ a t u r e ,

WSth $ h i s method t h e s e t w o scientists have obfafned k e s u l t s very dif'ier9en% fmrn t h o s e g e r r e ~ a l i l y c o n s i d e ~ e d c o r ~ e c t ,

I t seems t o be a p p r s p ~ f a t e t h e r e f o r e t o make u s e of t h e i r argument and d a t a ,

Normal Moisture Content a c c o r d i n g t o Cammerer

To b e g i n w i t h , Camnre~er draws a t t e n t i o n t o something q u i t e n a t u r a l , The m o i s t u r e c o n t e n t of new w a l l s always

exceeds t h e p u r e l y h y g r o s c o p i c rnofsture, %,e,, t h e m o f s z u ~ e c o n t e n t i n the air-damp s t a t e , H e a t t r z 3 b u t e s t h i s t o t h e

dampness of new w a l l s , wind d r i v e n :na%w, c o n d e n s a t i o n on %he i n t e r i o r s u r f a c e o f e x t e r n a l w a l l s and, f i n a l l y , vapour

d i f f u s i o n , The l a t t e ~ o c c u r s when t h e r e a r e d i f f e r e n t

p a r t i a l p r e s s u p e s of ths w a t e s v a p s u r , for example, a t b o t h s i d e s o f a n e x t e r n a l w a l l o A s t h e s e p a r t i a l p p a s a u r e s t e n d t o become e q u a l i z e d , t h e y cause e o n t f n ~ ~ o u s movement 0% t h e

m o i s t u r e from t h e room, l e a d i n g to _{c o n d e n s a t i o n on t h e wallsc} T h f s p ~ o b l e m a'tld o t h e ~ s connected wi$h t h e m s n s t u ~ e c o n t e n t of b u i h d i n g r n a t e ~ i s l s have been t ~ e a t e d in a p h ~ t l c u l a ~ l y c l e a r way by t h e c f v i l e n g i n e e r s C h r l s t e ~ G e m e l and N i l s

Tengvik b n Repopt No% 1 of S f ~ a t e n s k o m i t t d

f'cs

byggnadsfoss- knf ng

C u m m e ~ e ~ p o i n t s out s p e e f f F c a l P y t h a t i f a w a l l is damp f o r any r e a s o n its h e a t - f n s u l a . f i n g p ~ o p e r t i e s a r e reduced and t h e c o n d e n s a t i o n sf mo%ature becomes abnormally g r e a t , t h u s f n e ~ e a s f n g t h e r n s f s t u ~ s c o n t e n t r

However, no a c c u r a t e method of p r e d i c t i n g the m o f s t u r e c o n t e n t o f w a l l s from t h e p h y s i c a l laws o f m o i s t u r e a b s o r p t i o n and e m i s s i o n is known as y e t . T h e r e f o r e , sampling

i s t h e o n l y way o f o b t a f n f n g it f a r p r a c t i c a l p u r p o s e s , and an a t t e m p t can be made t o g i v e t h e expected m o f s t u r e c a n t e n t by means of s t a t i s t i c a l l y a r r a n g e d d a t a f"or m o i s t u r e c o n t e n t s o f e r e c t e d b u i l d i n g s , Data o b t a i n e d by Cammeper in t h i s

manner a r e shown i n T a b l e s I and I I L , H e p o i n t s o u t t h a t t h e magnitude of t h e m o i s t u r e c o n t e n t depends sn a g r e a t many

f a c t o r s , such a s c l i m a t e , season, l o e a t i o n and h e i g h t OF the b u i l d i n g a s w e l l a s q u a l i t y of t h e buSId4.ng m a t e r i a l The d a t a g i v e n i n t h e T a b l e s , h m e s s e ~ ~ e p e a e s e n t rnearl T ? ~ B L ? ~ s

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3 TT-95 obtained from extensive investigations.

Some indication of the moisture contents that may occur in Sweden can be obtained from the numerous examples of total precipitation and ensuing sweating on the interio surfaces of walls. It is interesting to note that the values obtained by Watzinger and Kindem, Norway, for ordinary brick- work, are from 0.4 to

4

per cent by volume and at partic- ularly exposed points from 007 to 17 per cent by olume.

Kregger and Eriksson consider 2 per cent by volume of moisture normal for brick walls and 3 per cent by volume for plaster coats. They found values of 12.8 and 6.4 per cent by volume for light-weight concrete.

TABLE I

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MOISTURE CONTENT OF INORGANIC MATERIALS

-

(per cent by volume) a. Interior walls in heated space b. External walls of heated space c o External walls of unheated space

*

Maximum values observed with formation of condensation,

Type of Material

?

Moisture content in per cent by volume c 2,s 13.0 1 0 e O 7.0 10.0 I Limiting Value Brick walls of any

weight per unit

volume, solid or with hollow spaces

Concrete of any weight per unit volume, irres-

a 0 0 5 3,5 1.0 1.0 1.0 0,2 to 3.0 b 1.7 7.0 3.0 3.0 4.0 pective of strengthen- ing material

Interior lime plaster External plaster Mortar Joint 3,O to 24.0% 0 0 5 to 17.0 0 0 5 to 17,0 003 to 16.0

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TABLE

I1

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MOISTURE,CONTENT OF ORGANIC MATERIALS -p e r cent by weight) UnfavousabP COP% slabs Peat slabs Fibre slabs Wood, bare, neither boarded with wood fibre

slabs nor plas

a) Applies to slabs on, the inner surface of external walls

b) Applies to slabs o n the outer surface of unexposed fronts

c) Applies to slabs o n the outer surface of exposed walls

As is evident from the Tables, C m e r e x ? makes a n espeefally sharp dfstinction between organic and inorganic materials, a distfnctfon which is still sharper i n the Table below (the influence of rnoisturee content o n heat-insulating p~spertfes of inorganic materials). He found that, because o f the marked h y g ~ c e i p ~ i c i t y o f organic materials, their mofsture content (in litpeg of water per cubic meter) is directly p ~ o p o ~ t i o n a l to %he weight of solid e o n s t f t u e n t ~ ~ The moisture content should therefore be expressed in per cent by weight, An kganfc material having a weight per uni t volume o f 300 kg./cu,m, thus contains tni ee a s many l i t ~ e s of water as that weighing I50 kgo/cuem,

For inorganic materiala, o n the other hand, Cammeper found that the wate content per cubic meter is the same,

irrespective of the weight per unit volume. The moisture

content is therefore suitably expressed in per cent by vobume,

Interesting in this onnestion are samples taken at the Sodersjukhuset (Southern Hospital) where a lfght eonekete

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w a l l weighing 424 kg,/cuomo c o n t a i n e d 23,6 p e r c e n t by weight and 10 p e r c e n t by volume of m o i s t u r e and a n o t h e r ond a t t h e same p l a c e 9,2 p e r c e n t by weight and 10 p e r c e n t by volume a t a weight per u n i t volume of 1,100 k g o / c u o m e I n s p i t e o f t h e i r g r e a t l y d i f f e r i n g we g h t p e r u n i t volume b o t h had t h e same m o i s t u r e c o n t e n t

-

expressed i n p e r c e n t by volume,

With r e l e r e n c e t o Table I i t should be p o i n t e d o u t t h a t Cammerer g i v e s t h e hygroscopic m o t s t u r e c o n t e n t of b r i c k s a s O02 p e r c e n t by volume and t h a t of l i g h t c o n c r e t e a s

2,5 p e r c e n t by volumeo I t i s found t h a t t h e m o i s t u r e c o n t e n t s o b t a i n e d by Cammerer, i f on1 i n one l i m i t i n g value f o r b r i c k s , most l i k e l y t h o s e o f a p a r t i t i o n , approach t h e v a l u e s shown i n Table I.

I n h i s i n v e s t i g a t i o n s Cammerer d i d n o t f i n d t h a t t h e r e i s a tendency f o r moist1 r e t o accumulate i n any p a r t i c u l a r

p a r t of t h e m a t e r i a l of a w a l l . However, a s

a

breakdown of Table I shows, he assumes t h a t t h e m o i s t u r e c o n t e n t i s g r e a t e r f o r a m a t e r i a l f a c i n g o u t s i d e t h a n f o r one f a c i n g i n s i d e ,

T h i s may be t h e b e s t e x p l a n a t i o n of t h e e f f e c t o f wind d r i v e n r a i n s and of t h e u u a l d i r e c t i o n o f h e a t flow, The f a c t t h a t t h e r e i s no r e g u l a r f o r m u l a t i o n of m o i s t u r e i n l a y e r s i s

a t t r i b u t e d by Cammerer t o e q u a l i z i n g c a p i l l a r y f o r c e s and t h e d i f f e r e n t d i r e c t i o n s of t h e h e a t flow i n summer and w i n t e r , He s t a t e s f u r t h e r m o r e t h a t n o t even a very dense p l a s t e r can p r e v e n t e v a p o r a t i o n of m o i s t u r e from a w a l l o

Cammererls s t a t e m e n t

-

t h a t he d i d n o t o b t a i n h i s d a t a f o r m o i s t u r e c o n t e n t s where t h e e v a p o r a t i o n o f m o i s t u r e had been excluded o r , t o say t h e l e a s t , r e n d e r e d e x t r e m e l y d i f f i c u l t

-

can be a c c e p t e d , Consequently much g r e a t e r v a l u e s f o r m o i s t u r e c o n t e n t s t h a n t h o s e g i v e n i n t h e Tables may be expected i n t h e s e l a t t e r c a s e s , p a r t i c u l a r l y f o r e n c l o s e d new b u i l d i n g s . T h i s may be S O , f o r example, i n t h e c a s e of

a n i n s u l a t e d r o o f ( " n e p o n s e t f ' )

The I n f l u e n c e of Moisture Content on t h e Thermal C o n d u c t i v i t y Value of I n o r g a n i c M a t e r i a l s

For those accustomed t o e s t i m a t i n g t h e e f f e c t of t h e m o i s t u r e c o n t e n t i n r e d u c i n g t h e i n s u l a t i n g value a s o n l y a few p e r c e n t , Cammerer's f i g u r e s must appear a s e x t r a o r d i n a r y a s t h o s e shown i n Table I I I o I n r e p l y t o t h e a u t h o r f s p e r s o n a l i n q u i r y b o t h Cammerer and K r i s c h e r have s t a t e d t h a t t h e

measured ( s m a l l e r ) i n f l u e n c e of t h e m o i s t u r e must be due t o t h e d i s p l a ement o f m o i s t u r e towanads t h e s u r f a c e r e s u l t i n g from t h e d e s l g n of t h e a p p a r a t u s o They emphas zed t h a t t h e g r e a t e s t d i f i c u l t y was t o a v o i d t h i s d i s p l a c e m e n t o

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6 TT-95

T A B L E I11

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I N F l U E N C E O F M O I S T U R E O N ThE THERMAL C O N D U C T I V I T Y

-

V A L U E O F I N O R G A N I C P i i T E R I A L S

Cammerer points out that the values listed in the

above Table do not apply to a moisture content within the limits of the hygroscopic properties of the material i n

question, in other words, not to moisture contents as low as those of bri ck ( 0 , 2 per cent by volume), and concrete (2,5 per cent by volume), since in this state the factors given below

are not yet apparento

An amount should be added to the thermal condue- tirity value since the material was dried at + h 0 5 ° C n and consequently contained but little of its moisture.

It

is evldent from the above Table that Cammeker considers it necessary that for brickwork under normal con- ditions an amount closely approaching 45 per cent, but not less, should be added to the

A

value obtained for material in the dry state. According to Krischer the eo~responding increment for brick with a weight per unit volume of 1 0 4

should be approximately 35 per cent, For concrete materials, according to both investigators, this increase should be

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7 TT-95 Cammerer e x p l a i n s t h i s g r e a t e f f e c t o f m o i s t u r e by t h e f a c t t h a t n o t o n l y d o e s t h e w a t e r f i l l some o f t h e f i n e p o r e s b u t even a t a v e r y e a r l y s t a g e , it s e t t l e s a l o n g t h e w a l l s o f t h e p o r e s , t h u s forming c o n t i n u o u s h e a t b r i d g e s o Furthermore he r e f e r s t o t h e g r e a t importance of t h e vapour d i f f u s i o n o K r i s c h e r found t h a t t h i s d i f f u s i o n a l o n e c a u s e s the- thermal c o n d u c t i v i t y v a l u e i n t h e m o i s t p o r e s t o m u l t i p l y f o u r f o l d a t +2Q°C0 The r e a s o n f o r s u c h a g r e a t e f f e c t from o n l y a s m a l l q u a n t i t y of m o i s t u r e i s , a c c o r d i n g t o Cammerer, t h e f a c t t h a t t h e s a i d h e a t b r i d g e a l r e a d y forms a t a n e a r l y s t a g e , The e f f e c t o f vapour d i f f ' u s i o n could a p p e a r s t i l l e a r l i e r , S u p e r f i c i a l l y , t h e v a l u e s of Cammerer and K r i s c h e r seem t o d i f f e r g r e a t l y , However, i f a g i v e n h _{v a l u e of a} m a t e r i a l i n t h e d r i e d s t a t e be t a k e n t o g e t h e r w i t h some of t h e v a l u e s f o r m o i s t u r e c o n t e n t s l i s t e d i n Table I , and i f t h e n a c o r r e s p o n d i n g i n c r e a s e a c c o r d i n g t o b o t h i n v e s t i g a t o r s be made and t h e d e t e r i o r a t i n g i n f l u e n c e o f t h e j o i n t s be

added, a t e r m i n a l v a l u e w i l l be o b t a i n e d which does n o t d i f f e r by more t h a n 1 t o 1 0 p e r c e n t from t h e a r i t h m e t i c mean v a l u e , T h i s must be c o n s i d e r e d s a t i s f a c t o r y i n e v e r y r e s p e c t , p- Regarding ~ r i s c h e r h d a t a i t i s found t h a t t h e i n f l u e n c e o f t h e m o i s t u r e c o n t e n t i s g r e a t e r f o r t h e lower w e i g h t s p e r u n i t volume, U n f o r t u n a t e l y no e x p l a n a t i o n of $ h i s can be found i n t h e l i t e r a t u r e ,

I n a very i n t e r e s t i n g t e s t made i n Sweden a l i g h t - w e i g h t c o n c r e t e m a t e r i a l , which was found t o have a m o i s t u r e c o n t e n t of a p p r o x i m a t e l y I 0 pep c e n t by volume, had h _{v a l u e s}

185 p e r c e n t h i g h e r t h a n t h o s e i n t h e a i r - d r y s t a t e , T h i s m o i s t u r e i n f l u e n c e 1 s s t i l l g r e a t e r t h a n t h a t g i v e n by

Cammerer, e v e n though d u r i n g t h e t e s t t h e m o i s t u r e must have been d i s p l a c e d t o a c e r t a i n e x t e n t towards t h e c o l d s u r f a c e , The I n f l u e n c e o f Moisture Content on t h e Thermal C o n d u c t i v i t y

Value o f Organic M a t e r i a l s

Cammerer makes a marked d i s t i n c t i o n between o r g a n i c and I n o r g a n i c m a t e r i a l s o A s s t a t e d above, i t i s s u i t a b l e t o

give t h e m o i s t u r e . c o n t e n t o f o r g a n i c m a t e r i a l s i n p e r c e n t by w e i g h t , and t h e r e f o r e t h e i n f l u e n c e o f m o i s t u r e on t h e t h e r m a l

c o n d u c t i v i t y v a l u e should a l s o be g i v e n i n p e r c e n t .by w e i g h t of m o i s t u r e . Cammerer found t h a t f o r o r g a n i c m a t e r i a l s t h e in- fluence per per c e n t by weight of m o i s t u r e can be e x p r e s s e d by a s i n g l e r l g u r e , namely an i n c r e a s e o f 1 . 2 5 p e r c e n t o f t h e

h _{v a l u e o f t h e m a t e r i a l d r i e d a t +105*Co}

I t may be mentioned t h a t a t a r e c e n t i n v e s t i g a t i o n on wood f i b r e s l a b s , where e v e r y means was used t o p r e v e n t

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8

TT-95

d i s p l a c e m e n t of m o i s t u r e , t h e i n f l u e n c e p e r p e r c e n t by weight of m o i s t u r e observed was a p p r o x i m a t e l y one p e r c e n t , T h i s a g r e e s w e l l w i t h C a m m e r e ~ ~ s f i g u r e s . A eomparison of C a m e ~ e r " f i g u r e s shows t h a t , whereas f o r a wood f i b r e s l a b w i t h 20 p e r e e n t m o i s t u r e c o n t e n t ( d r y b a s i n ) t h e p e r c e n t a g e i n c r e a s e i n t h e r m a l c o n d u c t i v i t y p e r p e r c e n t m o i s t u r e c o n t e n t is f o 2 5 p e r c e n t o r a t o t a l of 25 per c e n t ; f o r l i g h t weight c o n c r e t e w i t h 7 p e r c e n t m o i s t u ~ e c o n t e n t the p e r c e n t a g e i n c r e a s e i n thermal c o n d u c t i v i t y p e r p e r c e n t m o i s t u r e c o n t e n t i s % 3 , 3 p e r c e n t o r a t o t a l of 93 p e r c e n t . T h i s ought t o aeeount f o p t h e f a c t t h a t t h e m o i s t u r e c o n t e n t of t h e wood f i b r e s l a b i s e x p r e s s e d in p e r c e n t by w e i g h t ,

If t h i s s l a b h a s a weight p e r u n i t vorume of 300 k g o / c u o m , ther& i t s 20 p e r c e n t by weight of m o i s t u r e f a e q u i v a l e n t t o 6 p e r

c e n t by volume. Thus, e x p r e s s e d i n p e r c e n t by volume o f mo s t u r e , t h e i n f l u e n c e of m o i s t u r e c o n t e n t i s i n t h i s c a s e a p p r o x i m a t e l y 4 p e r c e n t f o r wood f i b r e s l a b s and 13 p e r e e n t f o r c o n c r e t e m a t e r i a9. C m e r e r e x p l a i n s t h i s g r e a t d i f f e r e n c e by t h e f a c t t h a t t h e m o i s t u r e i n o r g a n i c m a t e r i a l a , owing t o t h e i r hygro- s c o p i c q u a l i t i e s , i s e n t i r e l y OF p a r t l y absorbed by t h e f i b r e s whose i n s u l a t i n g p r o p e p t i e s a r e t h e r e b y r e d u c e d , The a i r s p a c e , o n t h e o t h e r hand, which t a k e s t h e most a c t i v e p a r t , remains i n t a c t . T h i s t h e o r y i s a l s o found i n Watzinger and Kindemss r e p o r t "

J o i n t s

I t must be emphasized t h a t t h e i n c r e a s e s g i v e n by Carnmerer and K r i s c h e ~ i n Table I11 do n o t i n c l u d e t h e i n f l u e n c e of t h e j o i n t s . T h i s l a t t e r i n c r e a s e must be t a k e n i n t o a c c o u n t s i n c e t h e t h e r m a l c o n d u c t i v i t y value of s t o n e m a t e r i a l i s e s t a b l i s h e d under nokmal e o n d i t f s n s , f o e o , th e t h e ~ m a l c o n - d u c t i v i t y v a l u e f o r m a t e k i a l i n t h e d ~ y s t a t e i n c l u d e s t h e expected i n f l u e n c e of t h e m o i s t u r e c o n t e n t , F P o

X.

H i r ~ e h b o l d h a s made up t h e f o l l o w i n g t a b l e from which, w i t h g i v e n t h e r m a l c o n d u c t i v i t y v a l u e f o r s t o n e m a t e r i a l of trimmed s i z e , t h e h _{v a l u e f 0 r . a s t o n e w a l l c a n be} r e a d . Cammeper g i v e s t h e foXlowing t h e ~ m a l c o n d u c t i v i t y v a l u e s f o r m o r t a r : v e r y d r y w a l l s : X = 0 0 6 n o r m a l l y d r y w a l l s : X = 0 0 8 damp w a l l s : X = 41.0

Page

-

9 TT-95

TABLE

I V

-

I N C R E A S E FOR THE

INF'LUENCE O F

MOR,TAR

WITH

V A R I O U S

S T O N E S I Z E S FOR ALL WALL THICKNESSES AND BONDS (CALCULATED BY H I R S C H B O L D )

It is very interesting and enlightening to compare

the thermal conductivity values given by Cammerer with those

used by the Swedish Building Loan Bureau (Statens ~ y ~ g n h d s -

lanebyrg).

Block

dimensions

cm, 0 0 2 O03 0 0 4 0.5 0 . G 0.8 1 . 0 i 2 5 x 1 2 x 6 , 5 50 30 1 7 9 3 -5 -11 25 x 12 x 9 , , 5 25 x 1 2 x I 4 33 x 25 x 20

Thermal

conductivity

value

kcal,/m,hr.

O C . I

Percertage increase of the thermal

conductivity value of stone for

mortar joints and plaster at a

thermal conductivity value for

stone of

Page

-

10

TTc.95

Und~essed brickwork on sand lime mortar of

brLck, wezght per unit

volume : 1 - 8 f , 6

a

,,la 10 2 Undressed brickwork of light-weight concrete uade o#' cement and sand, weight per unit volume:

1 . 0

0 0 7

Insulation of light- weight concrete without mortar, weight per unit volume : 1,2 0 - 5 0 , , 3 5 Gran~lated cinder, weight p e r . unit volume : 0;4

It appears that Cammerep may have based his cwlcuia

tfons, in some cases, an a thermal oonduetfvitg value for an

absolutely dry material differing from the 'value used in Sweden for a corresponding material,

For organic materials, o n the other hand, the agreement is satisfactory, owfng to the fact, of course, that the moisture zontent o f these is not nearly so important as for inorganic materialsd

C O N C L U S I O N

Although years of hard study have passed since the publicat ion of Camerep

'

s and the other inaesti gators 3 reports, their results cannot merely be disregardedo Should they prove correct it must be remembered that unfortunately the most economical thermal conductivity value for building

Page

-

11 TT-95 investigations into moisture- problems are being planned and carried out by the Swedish Committee on Building Research

(Statens ~ommittd fBr byggnadsforskning) and it is to be

hoped that in the near future results which closely approximate actual conditions will be produced.

BIBLIOGRAPHY

Canunerer, JoSo:- Die Bereehnung des praktischen ~~rmeschutzes der Baustoffe aus fhrer Wichte, Heizung and ~uftung 1943, no. 7/8, p. 75-81.

Cammerer, J. S. :

-

Die konstruktiven Grundlagen des warme and ~tiltesehutzes fm Wohn- and Industriebau.

Jul, Springer, Berlin (1936).

Cammerer, J.So:- Die Warmeleitzahl von Leichtbeton, insb. Gas

-

and Schaumbeton. Fortschritt and For-

schungen im Bauwesen, 1942, Series B no.2. Cammerer, J o s e :

-

Der Einfluss der Feuchtigkeit auf den

Warmeschutz von Bau- a d ~&nmstoffen nach dem internationalen SehrifUum, Warme and Kalte- technik, 1939, no.9.

+) Cammerer, J.So:- Feuchtigkeitsuntersuchungen zur Bestimmung des praktischen Warmeschutzes von Holzwolle

Leichtbauplatten. -Baugilde 21 noo14.

Gemmel, Christer and Tenavik, Nils:

-

Om kondensation och annan fuktbildning- f byggnader Rapport nr

I

f rhn Statens kornmitte' f6r byggnadsfor~kning~

Krischer, O m and RohnaPter,

H,:-

~grmeleitun~ und Dampfdiffusion in feuchten ~Gtern, VDI Forschungsheft 1940 noo402. Krfscher, O 0 and Rohnalter,

Hog-

w&meleitung und Dampfdiff'usion

in K3lteschut~stoffen~ Wgrme and ~Zltetechnik 194i,p,h, Watzfnger and Kindem;- Om Bvgnlnqsmate- 'aliers varmeisolering,

Publf cations of Kongl. Norske Videnskabers Selskab, 1934, no,l9,

All the above articles, except that marked with * )

can be obtained from the 1fbrary.of Chalmeps Tskniska Hb'gskola, Cammereras article * ) can be purchased as a photostat from

~rnstrzm and Coo AB, ~zteborg for Kr, 6,50. Gemmel and Tengvikqs paRer is obtaf nable at Statens ~ornmitte' fgr bygg- nadsforskning, Stockholm.