Report on a Study of Condensation in Central Mortgage and Housing Corporation Houses in the Winnipeg Area

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Report on a Study of Condensation in Central Mortgage and Housing

Corporation Houses in the Winnipeg Area

DIVISION OF BUILDING RESEARCH

REPORT ON A STUDY OF CONDENSATION IN

ｃｅｎｾｒａｌ

MORTGAGE

AND

HOUSING CORPORATION

HOUSES IN THE WINNIPEG AREA

by

Sheldon Cherry

ANALYZED

(Prepared for the Central Mortgage and Housing Corporation)

DBR Report

R 18

Ottawa,

FOREWORD

Problems of condensation in houses during cold weather continue to be a matter of major concern both to Central Mort-gage and Housing Corporation and to the Division of Building

Research. The Division is privileged to be able to observe how

serious the problem is by examination of houses which are under

the control of the Corporation. This report is a further record

of the results of some of these field observations.

The report forms a supplement ｴｾ that by Mr. Handegord

dealing with problems in Saskatchewan in the winter of

191+7-1948.

(Report R

16

"Report on a study of Wall Surface Condensation in

Prairie Houses", October

1949).

The winter of

1948-1949

saw a

continuation of the complaints to the Corporation about conden-sation in small houses in the prairie provinces, and particularly

in the vicinity of ｗｩｮｮｩｰ･ｾＮ The Division therefore arranged to

make a detailed survey of the "aftermath" of these complaints in the Winnipeg area.

The survey was carried out, with the fullest co-operation of the Corporation, by Mr. Sheldon Cherry who is also entirely

responsible for this report. The project was ｎｾＮ Cherry's first

assigrment after graduating from the University of Manitoba; he received initial assistance from the staff at the Regional Station of the Division at Saskato6n.

In acknowledging, on behalf of the Division, tpe'kind assistance and sympathetic interest of the' staff of C.M.H.C.

in this project, and in particular that of Mr. H. W. ｈｩｧｮ･ｴｴｾ

Regional Supervisor at Winnipeg, I wish to record the

determi-ｮ｡ｴｾｯｮ of the Division to persevere with this type of "operational

research" to the maximum possible degree consistent with available

staff and resources. It is hoped that through such reports as

this steady progress may be made towards a satisfactory solution of the condensation problem.

Discussion .

Conclusions and Recommendations ••..••••.•••••••• ｾ •••.••

Application of Remedies to EXisting House Problems .••.• Recommendations for New House Construction •••••.•••••••

Laboratory Reports . . . . . . . • •ｾＮ｟ ••... (a) Moisture Content of Insulation Batts ••.•••••. ,

(b) Analysis of wood Samples •..•••.•••••••••••••••

Acknowledgernents ' . References •..•...•.•.••...•.•••••••••..••.•••••••..•• Table I . Fi gure 1 . Figure 2 . Illustrations Appendix A

4

tt

4

S

S

S

6

7 Page 1 1 2 7

9

10 12

14

16

18

19

19

19

19

20 20

24

26 26 27 27

28

29

30

Interview: Nature of Complaints •••••• Houses Examined in Detail ••••••• in House No.2-I •••••••••••••••• in House No.4-I ••••••.•••••••••

in

ｈｯｵｾ･

No.6-I

.

in House No. 6-2 •••••••••.•••••• in House No.3-I •••••••••••••••• in House No. 3-2 .••••••••••••••• in House No. 1-1 and 1-2 .••....• (b) Conditions of 1. Conditions 2. Conditions

3.

Conditions

4.

Gondi tions

S.

Conditions 6. Conditions

7.

Conditions (a) Questionnaire Introduc tion . Objects of Investigation •••.•.••••.•••••••••••••••••••• Principles Involved in Condensation Formation •••••••••• Additional Features Affecting the

Condensation Problem ••••.•• (a) Insulation . (b) Vapour Barriers ••••••.•••••••• ｾ ••••••••••••••• (0) Ventilation . (d) High Humidities ...•••••••.•••••••••••••••••••• Me t.hod of Study .

(a') Questionnaire Form ..••.•.••••••••••••••••••••• (b) Procedure of House Examination for structural

and Insulating Condi tiona ••••••••.•••0 • • • • • • • •

REPORT ON A STUDY OF CONDENSATION IN C8:NTRAL MORTGAGE AND HOUSING CORPORATION HOUSES IN THE WINNIPEG AREA

by

Sheldon Cherry

The condensation of moisture on or within walls and attic

spaces of houses 1s an old and troublesome problem. Depending upon a

combinatfon of conditions, ice or frost may form and its sUbsequent melting may cause stains on wall and roofing members, interior

dis-coloration, and exterior paint failure on siding and finishing. Reports

of these damaging effects, and tenant complaints of interior leakage on

to walls, curtains and furniture in wartime rental houses owned by the .

Central Mortgage and Housing Corporation, resulted in a request from the Corporation for the assistance of the National Research Council in the examination of a large number of their rental houses in the Winnipeg area.

The Division of Building Research of the National Research Council administers to the technical research needs of the Corporation.

in association with their various departments. The Division is

in-terested in carrying out investigations which affect the nation as a whole and therefore welcomed the opportunity to study this practical. housing problem which is a condition common in some degree to all parts

of the c oun try. .

It was decided to concentrate this study in the Winnipeg area since complaints originated in that city and because the climatic conditions in that region are among the most severe on the continent. and thus favor the tendency for condensation to exist.

The investigation took place during the period June to

August,

1949.

As this was some time after the spring thaw, actual

con-densation was not observed, but the after-effects of its formation were quite visible.

ｏｂｾｔｅｃｔｓ OF INVESTIGATION

The main objectives of this investigation may be stated as follows:

( 1 )

(2 )

To determine the extent and nature of the condensation problem;

To study the insulating and structural conditions of C.M.H.C. wartime rental houses in which evidence of con-densation had been reported.

The study included preliminary field surveys and tenant interviews fol-lowed by a detailed examina tion of certain selected houses which are

described itn ､･ｴ｡ｩｾｬ further

on

in this report.

PRINCIPLES INVOLVED IN CONDgNSATION

. " "' , ｆｏｒｾａｔｉｏｎ

An understanding of the phenomenon of condensation requires a basic knowledge of the psychometric principles governing the behavior

of air-water vapour miAtures. These principles may be explained by

considering the water vapour present in a given space to be "c ont afne d "

by the air occupying the same space, although this concept is not strictly correct.

A given weight of air may contain various amounts of water

vapour from zero up to a certain limit. This vapour cQntent limit

de-pends on the temperature of the air. For ｡ｾｹ particular temperature

there exists a definite maximum amount Of water vapour-that each pound of air may contain.

When water ｶ｡ｰｯｾｲ ｩｾ added to a given weight of air at a

definite temperature until this limit is reached, the air ｩｾ said to

have become 8aturated or to have reached its ｳ｡ｾｵｲ｡ｴｩｯｮ point. The

amount of water vapour required to saturate this weight of air in-creases markedly with increasing temperature.

Usually the air in a room is only partially saturated and the degree of saturation may be measured in terms of relative humi(iity,

which is the ratio in ｰ･ｲｾ｣･ｮｴ of the weight of water vapour present to

the weight required for ｳ｡ｴｵｲ｡ｴｩｯｾ ｡ｾ that ｴ･ｭｰ･ｲ｡ｴｵｲ･ｾ When the air

is completely dry the R. H. will be 0 per cent and when the a1.r is saturated the R. H. will be 100 per cent.

If 'air which is only partially saturated is cooled,' the amount

of water vapour required for saturation decreases and ｨ･ｮｾ･ the R.

H.

increases. When the temperature is lowered sufficiently, so that ｾｨ･

amount of water vapour present is exactly equal to that required for saturation, the relative humidity will have reached 100 per cent apd the temperature at which this occurs is called the dew point

tem-perature. If the temperature is lowered further the capacity of the

air for holding water vapour is exceeded and precipitation of the ex-cess moisture will occur.

The above discussion is sufficient for the understanding of the first of two common forms in which condensation may exist in build-ings, namely:

(1) surface condensation;

3

-Condensation of moisture from the air occurs when the temperature is

below the dew point temperature of the air-vapour ｾｩｸｴｵｲ･ and ｭｾｹ

oc-cur as water or frost, depending on whether the dew point temperature

is above or below 32°F. A common example of this phenomenon is the dew

formation on the surface of a glass of ice water or the frosting of window panes, walls and doors in houses during cold weather.

In considering inter-wall space condensation i t is practical

to think of the water vapour present in a space in terms of the ｰｲ･ｳｳｵｾ

which it exerts. Such a pressure has a definite value depending

entire-lyon the density of the water vapour. This density of water vapour will

depend both on the relative humidity and temperature and can be determined

for any condition if these two quantities are known. During the winter

months water vapour densities present inside a house will be higher than those outside, even though the relative humidity outside may be higher. This difference in density results in a pressure difference tending to

produce a flow of vapour from inside the house, through the walls and

ceilings to the outside, i.e., vapour flows from high to low pressure areas.

It is apparent that apart from this pressure difference, still

another factor influences vapour diffusion through the wall, namely the

wall construction. The components of the wall will offer a certain

resistance to flow and will determine the actual amount of vapour pass-ing through, as well as the way in which the vapour pressure will vary

from inside to outside. A flow of heat will also occur simultaneously

with the flow of vapour through the wall and the temperature

distri-bution will be determined by the wall construction. Knowing the wall

construction and exterior and interior conditions it is possible, by calculation, to estimate the vapour pressure and temperature at any

point, and therefore an estimate can be ｾ｡､･ as to whether condensation

will take place within the wall. If the actual vapour pressure for

the temperature which exists is above (below) the vapour pressure for saturation condensation will (will not) occur.

For a more complete theoretical approach to the problem and a detailed analysis of the manner in which temperature and pressure dis-tribution takes place within the wall section, the reader is referred

to the works of recognized authorities in this field, some of which are

listed at the end of this paper.

Additional features affect temperature and pressure

distri-bution at various points in the wall. These are discussed below in

order to give an overall picture of the probability of inter-wall space condensation.

ADDITIONAL F'EATFHES AF'FEC'rING 'l'HE CONDENSA'i'ION ?HOE,LEIvi

(a) Insulation

The prime purpose of insulation is to decrease fuel consumption

by retarding the passage of heat to the outside air. By so doing the

inner wall surface temperatures are higher than a non-insulated wall of the same construction but the temperature of the inside surface of the outer sheathing is below that of the non-insulated section (since a lesser quantity of heat passes through this zone per unit of time than

in the previous case). Consequently, the sheathing surface is below the

dew point temperature at much higher outside temperatures than in the

case of the non-insulated wall. Ap a result, in insulated walls the

amount of ｣ｯｮ､･ｮｾ｡ｴｩｯｮ which nBy collect is increased since there will

be longer periods during whi c h condensation will be apt to occur, as

compared to the short periods in which temperatures are low enough for

condensation to take place in non-insulated walls. The most likely

place for condensation to occur in insulated walls is on the inside face

of the sheathing or siding. Actually insulation is not the cause of

condensation since it merely conserves heat, and prevents it from

Leing used to heat the outer portions of the wall. The problem,

there-fore, ts esentially one of preventing vapour from entering insulated

walls.

(b) Vapour Barriers

The purpose of such a barrier is to restrict the outward pas-sace of vapour into the wall space to an amount which may pass through

the outer wall material by normal ｯｵｾｦｬｯｷ process under the lesser

vapour pressure force which exists,due to the temperatue difference be-tween the interior surface of the sheathing and the outside surface

of the wall. Obviously, outflow should not be irrlpeded so that a vapour

barrier must not be placed on the cold side of a wall. Rather, it must

be located at or near the inner face of the warm wall so that its temperature will be above the dew point and therefore no condensation will occur on the barrier.

(c) V\3ntilation

Normal equilibrium conditions of inflow and outflow may be

aided through the use of ventilator openings. Ventilation of attic

and wall spaces is essentially a means of reducing vapour accumulation in these regions by allowing the rapid dissipation of the vapour to

the outside air. In older houses this ventilation is provided due to

the fact that, unlike present practice, construction teclmiques did not

produce an air·-tight home. Nowadays, louvre or eave openings are

pro-vided to give the required ventilation. They should te used in

5

-(d) High Humidities

The effect of humidities on the problem has already been

discussed. It is sufficient to state that for comfort and economy,

natural air infiltration has been reduced to a minimum by the present

tendency of "tight" construction. Health education has advanced the

practice of artificially adding moisture to the air. The overall

result is an accumulation of moisture in the house which causes high relative humidities.

METHOD OF STUDY

The wartime rental houses of the C.M.H.C. in the Winnipeg area were built in groups or projects located in different sections of

the city and its suburbs. The investigations which were carried out

included projects 1 to

6

inclusive.

(a) Questionnaire Form

The initial step of the condensation study was the

compi-lation of a questionnaire form (see Appendix A) which was used to record

the information received from tenants. This form was developed after

preliminary talks and observations were carried out with the house

dwellers of Project No.1. From this area i t was learned just what

could be expected in the way of condensation troubles and complaints, and such information was incorporated into the form.

By examination of the questionnaire it may be seen that an attempt was made to determine two aspects of the problem, namely:

(1) evidence of condensation, the manner of its detection

and the location of its existence.

(2) miscellaneous remarks regarding living (moisture)

con-dit tons.

Following the production of ｾｨ･ questibnnaire-blank,verbal

interviews and visual examination of interior and exterior conditions

were carried out in Project Nos. 2 to

6

inclusive. This work was done

on a Nhouse-to-house" canvassing basis. The completed forms were

sub-sequently used to evaluate figures showing the extent and nature of the

condensation problem. They were also used as a basis for the selection

of certain houses in which a detailed examination of insulation and structural conditions was made.

with the exception of one ､ｷ･ｬｬｾｮｧＬ all houses selected for

this detailed study showed conclusive evidence of having been affected

attempt was made to choose those houses which would be most seriously

affected, but this was naturally quite difficult and may not have been

the case.

For reasons later discussed only one and one-half-(l 1/2) storey dwellings were examined in detail although questionnaire forms were completed for the single-storey houses as well.

(b) Procedure of House Examination for structural and Insulation

Conditions.

Insulation and structural conditions were observed at:

(1) interior locations

(a) attic peak and eave spaces

(b) first floor wall spaces'

(2) exterior locations

As shown on the section drawing of a 1 1/2-storey C.M.H.C. house (see

fig. 1), the upper storey contains an attic peak and two eave spaces.

One eave space (the storage area) was readily accessible by means of

the door located in a bedroom wall. Entrance to the corresponding space

at the opposite end of the house was made by removing a wall panel or cutting a section of the plasterboara between the studs in a bedroom

on the second floor. In a similar manner the attic peak was studied

through a trap door cut between the rafters of the second floor hall

ceiling. Wall examinations were made by removing a panel of

plaster-board from a wall of the first floor. The method of application and

condition of the insulation was observed. The insulation was then

stripped down to allow examination of the underlying sheathing.

Exterior conditions were studied and the asbestos shingle or wood siding and building paper were removed to observe the appearance of the sheathing.

Photographic evidence was taken of the ｣ｯｮ､ｩｴｩｯｮｾ found and

specimens of insulation, bUilding paper and wood were removed for labora-tory analysis.

Insulation, plasterboard and siding were replaced and necessary repairs carried out in all cases.

7

-RESULT OF STUDIES

(a) Questionnaire Interview: Nature of Complaints

Interviews were carried out and blank forms completed for

664

dwellings in Project Nos. 2 to

6

inclusive. Questionnaire forms

were not completed for Project No.1 since this was the first area

sur-veyed and such forms were not available at the time. Remarks of tenant

complaints were noted. Through such interviews it was possible to

establish the extent and nature of the condensation problem.

Tenants repeatedly reported troubles which followed a definite pattern and are, to a large degree, directly attributable to the

con-densation problem which exists. The 1 1/2-storey dwelling was the most

seriously affected -- the problem having created the greatest nuisance

to the tenant and damage to the house in this type. Complaints were

generally of two natures:

(1) Interior leakages

(2) Interior frost deposits

Leakage, which was recognized as the result of condensation accumulations in eave and attic peak spaces, was very common and occurred during the spring thaw and frequently in the fall when a cold period would be

fol-lowed by a sudden rise in temperature. The usual outlet for such

leak-age was from light fixtures, nailheads, ceiling plasterboard joints,

wall to ceiling joints and in the general ｶｩ｣ｩｾｩｴｹ under the eave space.

This leakage caused staining and damage to walls and floors, ｣ｵｲｴ｡ｩｮｳｾ

carpets and other furniture. Condensation leakage appeared to be more

predominant in the north end of the houses, (although this was not al-ways the case) under and in the attic eave spaces, and, as will be

shown later by the photographs, the insulation in the north attic space was in the most serious condition.

Leakage of this type was rarely reported in the single-storey dwellings and in those isolated cases in which the trouble did exist it was usually found to be due to infiltration of snow through

cracks which were often readily visible in the attic roof. Construction

defects of this nature were also found in the 1 1/2-storey dwellings

(see fig.

3).

However, at least one definite report of condensation

in the attic space was received, i.e. tenants actually observed ice

layers on the interior of the roof. At the same time it was

estab-lished that the attic vents in this particular house were not operating properly during the winter since they had become blocked with ice.

Detailed studies were therefore limited to the 1 1/2-storey

type since the single-storey dwellitigs ｾｮ･､ to show definite evidence

Complaints of interior frost and ice deposits were received

from single-and 1 1/2-storey houses alike. These difficulties appear as

frost accumulations on the interior surfaces of exterior walls, parti-cularly at baseboards and lower portions of plasterboard, along points of concentration of wood framing such as corners and behind furniture

where air circulation is restricted. The deposits result in staining

of the walls and furniture and when in contact with c19thing, sometimes

cause mildew. Sweating or moisture zones are often present above such

accumulations -- presumably from the temperature gradient which exists

from the floor upwards. Corner deposits have been found to exist from

floor to ceiline although this was seldom the case.

One other notable complaint was frequently reported when

interviewing tenants. Heavy layers of ice were forming on

second-ｾｴｯｲ･ｹ windows. When such accumulations melt interior leakage results, the water dripping through the second floor and onto the ceiling and

walls of the ground floor. First floor windows were likewise affected

but much of the water was due to melting of condensation in attic spaces which found its way between walls and down through the window frames. The fact that If'any houses report such water penetration with a heavy wind-driven rain may' indicate that the window details or construction are in some way defective.

Exterior paint failures and water stains commonly occurred

in single-and 1 1/2-storey houses with wood siding. The asbestos

shingle siding did not show any deterioration. An extensive examination

of paint failures in C.M.H.C. houses in the Vancouver area has been made

by Mr. E. V. Gibbons and Dr. C. Y. ｈｯｰｫｩｮｳｾｾ of the National Research

Council. In their report the authors concluded that condensation was

a decided factor in contributing to these failures.

Tenants frequently complained of cold floors and draughty rooms.

The most common complaints of the tenants have been set up in

Table I. This table is an indication of the extent and nature of the

problem. These figures have been broken down into projects and

re-present faults ranging from the slightest -- such as single isolated

leakage or frost deposits -- to the most serious, such as leakage

oc-curring in many locations from ceilings and walls of anyone house. Certain houses show all the defects listed, while others may be limited

to a single fault. The quantities are ｢｡ｾ･､ solely on tenant reports.

ｾｾ ｦｾ･ｰｯｲｴ on the ｅｸｾｭｩｮ｡ｴｩｯｮ of Paint on the Exterior of Houses in the

Vancouver Area" by Dr. C.Y.Hopkins and E.V. Gibbons. DBR report R 1,

-- 9

=

It will be noted that the 1 1/2-storey dwellings of Project Nos. 4, 5 and 6 show a lower percentage of condensation leakage than

the remaining projects. There appears to be no apparent differnece in

the actual construction of these houses. Project Nos.

5

and 6 have only

been occupied since ls47 (i.e. two winters) while the others have been

lived in for a period including three winters. Project No.5 was built

by a different contractor than all the other projects and the eave spaces face east and west as opposed to the north-south locations in

Project Nos. 1, 2,

3,

4 and 6. The insulation in the attic storage

space for number 5 is more securely supported through the use of plaster-board as opposed to the corrugated cardplaster-board backing in all other

projects.

(b) Conditions in Houses ｅｾ｡ｭｩｮ･､ in Detail

Following interviews and field surveys a total of six

houses were selected and examined in the manner previously described. Observations were limited to this number since it was felt that con-tinued investigation would produce only duplicate condltions (with the

possible exception that more ｾ･ｲｩｯｵｳ cases would probably be found if

a very large number of houses were examined). Also, the cost of

re-pairing the damage done during the detailed study would be prohititive for large scale examinations.

The houses investigated were as follows:

General: All houses are of the 1 1/2-storey ｃＮｾＮｈＮｃＮ basementless

type without ventilator openings of any ktnd. An unexcavated

crawl space exists under the house and this area can be

venti-lated through openings located in the foundation wall. The

roof construction was the same in all cases consisting of:

asphalt shingles, building paper, wood sheathing, 2= by 4=inch

rafters and 2-inch rock wool insulation. H45 or 46 houses are 5-room dwellings. H15 or 16 houses are 6-room dwellings. House Noo 2-1:

House No. 4-1:

C.ff-.H.C. type H-15 located at 1086 Garwood Avenue.

Wall Construction: Wood siding, building paper, wood

sheathing, 2- by 4-inch studding, 2-inch rock wool in-sulation and plasterboard.

C.M.H.C. type H46 located at 1646 Roy Avenue

Wall Construction: As for houses No. 2-1 but with

House No.6-I:

House No. 6-2:

House No.3-I:

House No.

3-2:

C.M.H.C. type H-16 located at 699 Carter Avenue.

Wall Construction: _{As for house No. 4-1.}

C.M.H.C. type H-15 located at 700 Carter Avenue.

Wall Construction: _{As for house No. 2-1.}

C.NI.H.C.

type H-16 located at 724 Martin Avenue.

Wall Construction: As for No. 2-1.

C.M.H.C. type H-15 located at 738 Martin Avenue.

Wall Construction: As for house No. 4-1.

In addition minor observations were made at: House No.1-I:

House No. 1-2:

C.M.H.C. type H-16 located at 705 Martin Avenue.

Wall Construction: As for house No.

2-1-C.M.H.C. type H-16 located at 578 Harbison Avenue.

Wall Construction: As for house No. 3-2.

(1) Conditions in House No. 2-1

(i) Scope of study

Wall and attic studies were carried out in this house where

evidence of serious condensation had been reported. Photographs

of the different spaces were taken and a sample of wood sheathing

and 2- by 4-inch rafter was removed for laboratory analysis. The

exterior was also examined.

(ii) Exterior Conditions

'l.i.e west wall was seriously stained and blistered (see fig.

4)

as well as a portion of the south wall. East and North walls

showed paint failure (fig. 5) but not to so great an extent as the

other sides nor in the form of blisters. The tenant reported that

a greasy substance ran down the North, west and East walls during

the spring thaw. Slight traces of this substance (i.e. stains)

were still Visible at the time of inspection even though an effort

had been made to remove them. In the past, the west wall of this

house has been exposed to an open field on which construction is now taking place.

11

-Two blistered sections of siding were removed from the

west wall and the underside examined (fig.

6).

Water stains

and black tar marks were visible. A sample of building paper

was then cut away in order to examine the wood sheathing

under-neath. No definite· water stains were found, but the wood hed

a tan colour, presumably from the close proximity of the tarred building paper.

(iii) Evidence of Interior Condensation.

Leakages occurred in the spring from the ceiling of the front hall, living room and first floor bedroom near the north

end of the house. Moisture on the east and west walls of the

front bedroom and living room was also reported. This wetting

follows the general pattern which is a result of frost forming on second floor windows, melting and running down inside the

house. Some leakage was also reported at the south end of the

house from the bath and kitchen light fixtures. Most ceiling

leakage dripped from nailheads and from areas in the vicinity

immediately beneath the attic eave spaces. This type of

leak-age has occurred during the spring thaw of each of the last three years.

(iv) Conditions in Attic and Wall ｾｰ｡｣･ｳ

The north eave space wasln the ｾｯｳｴ serious conditton of

all those houses examined. The reverse side of the panel cut

to eain entrance was visibly stained (fig. 7) as was the

plaster-board ceiling throughout its entire length (fig

8).

Insulation

batts had become torn or detached and were found lying in the

eave space (fig.9). When insulation batts were stripped down

from the roof it was found that 2- by 4-inch rafters and wood

sheathing were badly stained (fig. 10). When the batts were

re-moved from the end walls it was found that the sheathing was

also marked (fig. 11). Wood samples were taken from this space

for laboratory analysis.

The south space which has the storage area also appeared

to have suffered from condensation. In this case, however,

most of the ｳｴ｡ｩｮｾ were concentrated on 2- by 4-inch rafters.

The rafters and roof sheathing of the attic peak space

were seriously stained (fig. 12) and a great deal of the

in-sulation had become completely or partially detached (fig. 13) . . A section of the west wall of the living room was removed

and conditions observed. The insulation had been placed against

the outside sheathing but did not appear to have been dampened

when the insulation was stripped down and the wood was

un-marked. The insulation was re-installed, this time

accord-ing to the recommended practice, i.e., with overlappaccord-ing of

batt backing against the interior stud facing. The

plaster-board finish was then replaced.

(v) Living Conditions

The house is heated by a coal-burning space heater lo-cated in the living room and a wood-burning stove in the kitchen (this has just recently teen replaced by an electric

stove). With the exception of the outside perimeter of the

floor, the dwelling was comfortably warm during the winter

and the fuel bill was approximately $100.

Two adults and six children of an average age of 10

years occupy this dwelling. The housewife does a laundry

approximately three times per week, and it is hung in the

kitchen to dry. The house was not reported as noticeably

damp during any season of the year. Additional moisture was

deliberately added by placing a very large open pan of water on the space heater.

The windows were heavily frosted all during winter but the panels of the back door were free from condensation.

(Usually condensation does occur on the back door panels but, due to the heat given off by the kitchen stove, surface tem-peratures were presumably sufficiently high to prevent this condition.

(2)- Copditions in House No.

4-1

(i) Scope of study

The extent of the investigation was identical to that of study 2-1.

(ii) Exterior Conditions

There was no sign of any failure on the exterior which

was finished with an asbestos shingle siding. Upon removal

of some of the shingles and building paper slight stains were found on the sheathing.

(iii) Evidence of Interior Condensation

As usual, the common condensation leakage predominated under the north eave space which in this case was the storage

13

-hall. Djrect evidence of condensation was noted by the.

housewife who had felt ice deposits behind the insulation

batts in the storace space. An attempt was made to catch

the leakage in this space but some water leaked through the

living room ceiling at various places. In the spring a

strong, musty odour was noticeable on the second floor. Frost accumulations were also reported along the

quarter-round in the bathroom. Such deposits were

particu-larly thick near the ceiling. The ice melting on the second

floor windows also caused interior leakage.

These effects have been occurring over a period of three

years which is the length of time the ｨｾｵｳ･ has been occupied

by the tenants.

(iv) Conditions in Attic and Wall Spaces

The north (storage) space, in ｷｨｩ｣ｾ an ice layer had

actually been felt, was the most seriously affected. The

cardboard ｢｡｣ｫｩｮｾ had become detached and was badly

water-stained. 2- by 4-inch rafters and roof sheathing was badly

marked. A purplish discoloration was noted on a few sheathing

boards and a sample was removed for examination.

The insulation in the south space was in good condition but stains were noted on the upper surface of the plasterboard

for the first floor ceiling. Removal of the insulation batts

showed stains on 2- by 4-inch rafters and sheathing at eave

soffet boards. The extent of marking was not, however, as

great as that found in the bpposite space.

The insulation was intact and in good shape in the attic peak space but the usual water stains were noted on the roof

sheathing and rafters when portions of the insulation were re-moved.

An inspection was ｾ｡､･ on the west wall of the first

floor bedroom. The insulation and sheathing were both in good

condition and no water stains were visible. Exterior

exami-nation was made in a position corresponding to the reverse side of this section.

(v) Living Conditions

A coal-burning space heater and a wood-burning kitchen

stove provide a comfortable heat source during the winter. No

storm windows were used on the second floor which was exceed-ingly hot.

Four children, averaging twelve years of age, and two

adults occupy the dwelling. The laundry which is done once a

week is hung inside the house. Additional moisture js added by

placing water in the compartment provided behind the heater. All windows and the panels of the back door frosted up during the winter.

(3)

Conditions in House No.

6-1

(i) Scope of study

Wall and attic eave space ｩｮｳｰ･｣ｾｩｯｮｳ were carried out and

photographs taken of the different spaces.

(ii) Exterior Conditions

The exterior, whtch is finished with asbestos shingles, was in good condition and showed no evidence of deterioration.

(iii) Evidence of Interior Condensation

Heavy frost accumulations were reported along the exterior wall baseboards (up to a height of approximately one foot from the floor), particularly in the first floor bedrooms, and also at scattered locations on the exterior walls of these r00ms.

Fig.

14

illustrates a typical bedroom wall condition. It was

reported that frost could readily be scraped from these spots. (The interior of the house had been painted some time during the late fall or early winter so that it is possible that some of the areas showing such failures were not completely dry.) Stains were also present on the walls of the second floor tedroom,

particularly at points of wood concentration (fig.

IS)·

The

in-terior discolorations on the first and second floor were the most serious of those encountered in all houses examined.

Leakage was reported from the back, first.floor bedroom and also from a plasterboard joint in the living room ceiling.

(iv) Conditions in Attic and Wall Sp-aces

The south attic space was in good condition with nearly

all insulation as originally placed. A few slight stains were

noted on the upper surface of the plasterboard on the first

floor ceiling. It seems possible that some of the leakage

and stains was due to faulty construction since in certain

places ｾｴ was found that the roof sheathing was not very

closely fitted together and in one particular spot was missing

altogether. The spacing of the 2- by 4-inch rafters sometimes

1.5

-eave space at points corresponding to the reverse side of the frost spot discolorations on the second floor were noted.

Such stains were only slight and did not appear to have caused

(at this time at least) any damage to the wood framing.

EVi-dence of frost accumulations behind the batts was lacking since the sheathing was unmarked.

In the north eave space the cardboard supporting the in-sulation was badly stained and was becoming detached showing that condensation had taken place with subsequent leakage. This statement is supported by the fact that the tenants re-ported hearing water dripping in the north attic space during

the spring thaw. Although some 2- by 4-inch rafters were

slightly stained the insulation was still in good shape and did not appear to have been seriously dampened at any time.

The plasterboard of a portion of the south wall of the first floor front bedroom was removed and the insulation and

underlying sheathing observed. As in all cases, the rock wool

was pushed in against the outside sheathing and there was no lapping along the interior face of the 2- by 4-inch studs. The insulation was firm and rigid and did not appear to have

been dampened at any time. The top board of the wall

sheath-ing was water-stained but all other sheets were unmarked. There was no evidence of water or decay at the bottom of the

wall section near the floor. One panel of the wall was

re-insulated with

J.

mansville rock wool applied in the

recom-mended manner. The two adjacent panels were replaced with

the original rock wool insulation (with the exception of a portion of one in which a batt of the new rock wool was

placed) which was installed in the s?me manner as found, i.e.

against the 'sheathing. A l3-pound waxed kraft (Grade XX)

vapour barrier was applied to the newly insulated ｰｾｮ･ｬ and

the adjacent section nearest the window. Such panels might

be observed during the corning winter to note if any frost ac-cumulations are taking place behind the batts and to what extent (if any) the proper installation of insulation and

vapour barrier affects the formation of condensation.

How-ever, due to lack of water stains it seems doubtful whether these particular panels are accumulating condensation in winter.

In summarizing, i t may be stated that no visible decay or mould was noted in those portions of the walls and attic

spaces examined. The structure appeared to be sound and

(v) Living Conditions

The tenant reported that the houRe was unusually cold and draughty in winter, even though the fuel consumption was

high. ｾｯｲ･ｯｶ･ｲＬ the second floor bedrooms which in most

cases have been reported as almost unbearably hot, were

ex-ceedingly cold and uncomfortable. This was particularly true

of the west bedroom which had to be closed off during a portion

of the winter heating period. The house was damp in winter

and "coolish" in sununer. Pour young children and two adults

occupy the dwel.Ling which is heated by a coal-burning space

heater. Only a small amount of washing is done in the house,

most of it being sent to the laundry. Some damp-frozen wash

is, however, placed inside the house to thaw and dry, and at

times is hung in the upstairs bedroom. This might account

for the heavy frost accumulations and subsequent discolorations

shown in fig.

15.

Additional moisture is added from a small

open pan which is kept filled with water and set on the heater. The panels of the back door become heavily coated with ice

and windows are usually frosted throughout the cold winter

period Ventilation was very limited since doors and windows

were rarely opened.

(4)

Conditions in House'No.

6-2

(i) Scope of Study

The extent of the investigation was identical to that

of study

6-1

with the addition of an examination of the attic

peak. This house is located ､ｩｲｾ｣ｴｬｹ across the street ｦｾｯｭ

house No.

6-1

and was therefore subject to the same weather

conditions. The tenants have been living in this dwelling

for a period of two and one-half years and reported no interior surface condensation or evidence of inter-space condensation

during that time. Since no defects were reported it was

thought advisable to examine attic and wall spaces.

(ii) Exterior Conditions

The paint on the east wall siding was badly blistered while the paint on the north and west walls also showed

evi-dence of deterioration. Two siding boards were removed from

the east wall. Although badly warped, no water stains were

noted on the underside of these boards. However, dark tar

marks were present, presumably from the underlying building

paper. The building paper was itself ｾｵｳｴＭｳｴ｡ｩｮ･､Ｌ apparently

from the nails which passed through it. The wood sheathing

under the blistered siding appeared relatively new, but was of a tan colour.

17

-(iii) Conditions in Attic and ｶｾｬｬ ｾｰ｡｣･ｳ

North and south attic eave spaces and the attic peak

were examined. The north space was in good condition with

all insulation intact (except for one single batt). Some

panels were strioped down and the wood sheathing found to be

unmarked. In the south space, which is ｾｨ･ storage space, all

cardboard backing was intact and free from stains. The

under-lying insulation and sheathing were also in good condition.

All but two batts were found intact in the attic peak. A.

few water stains were visible on the plasterboard ceiling of

the rooms below. Stains which may have been evidence of slight

decay were noted on one board of the roof sheathing. This

particular board was continuous through a number of 2- by 4-inch panels and may have been in this condition when installed.

All other boards were free from discoloration.

A section of the ｰｬ｡ｾｴ･ｲ｢ｯ｡ｲ､ was removed from the west

wall of the front first floor bedroom and the insulation

and sheathing examined. The rock wool which had been

instal-led against the outside sheathing was in good condition.

Water stains which may be evidence of condensation were found

on the sheathing. Two panels of the wall were replaced with

new Johns-Eanville rock wool and the vapour backjne

over-lapped on the interior stud surfaces. The remaining panels

were insulated with the original rock wool insulation pushed

against the sheathing. A 13-pound waxed kraft (Grade XX)

vapour barrier was placed over one of the re-insulated panels

and an adjacent panel insulated in the original manner. ｾｨ･

conditions of workmanship were the same as for house No. 6-1 and the same recommendations apply to this house.

(iv) Living Conditions

The first floor bedrooms and the second floor west bed-room were very cold during the Winter but not unlivable as

was reported across the street at house No.

6-1.

The east

bedroom on the second floor was comfortable. The tenant

re-ported that the house did not feel damp during any season of

the year. Five children and two adults live in the dwelling.

Clothes are washed approximately twice per week and hung

in-side to dry. Additional moisture is added by an open pan of

water placed on the coal-burning space heater. A

wood-burning cook stove is used in the kitchen. All windows

(With the exception of the west wall living room and kitchen windows) and the panels of the back door were frosted in winter.

($)

Conditions in House

No.

3-1

(i) Scope of Study

This investigation was limited to attic eave and peak studies.

(ii) Exterior Conditions

No paint failures were observed on the exterior wood

siding but all nailheads were rusted and were plainly visible.

(iii) Interior Condensation Evidence

Leakage occurred across the entire ceiling of the living-room, hall and front bedroom (under the north attic eave space),

through light fixtures and from ceiling joints. Leakage from

the second floor bedroom light fixture was also reported.

Frost deposits were noted at scattered spots on the first floor

walls. These conditions have been occurring for three years

and are getting progressively ｾｯｲｳ･Ｎ

(iv) Condition in Attic Spaces

The north" (non-storage' space was again most seriously

affected. Many insulation batts had become completely or

partially detached. Stains were visible on the upper surface

of the plasterboard on the ceiling of the room below (fig.

17)

and also on some of the rafters, but the wood appeared

un-marked. The south space was in good condition with all

insu-lation and cardboard backing intact and unstained.

The insulation in the attic peak was iQ very poor

con-dition and a large number of batts had fallen. Serious

staining was noted on the sheathing and rafters.

(v) Living Conditions

Heat was supplied by an oil heater and the fuel bill

was in excess of

$175.

Four adults occupy the dwelling.

The laundry, which is done once a week, is hung inside to dry. An artificial humidifier is used by the tenants and is lo-cated in the living room.

19

-(6)

Conditions in House No. 3-2

The study was identical to house No.3-I. Although

no frost deposits were reported, leakage across the area

under the north eave space was again reported. Conditions

in the attic eave and peak spaces were the same as in house

No. 3-1. Many batts were found detacted and lying on the

first floor ceiling. ｾｾ･ｮ the insulation was stripped down

only slight stains were found on sheathing and ｲ｡ｦｴｾｲｳ

which appeared unmarked. All batts remained in place when

the cardboard backing of the 'south (storage) space was

re-moved. The batts in the attic eave space had suffered from

the effects of condensation and were in a similar

con-di tion t o those shown in fig. 13.

(7) Condiｾｩｯｮｳ in ｈｯｵｳｾＢ No. 1-1 and 1-2

Leakage was reported in the attic space of House 1-1.

Although ｣ｯｮ､･ｮｳ｡ｴｾｯｮ was evidently the chief cause, a

certain amount can be expected from construction defects as

shown by ﾷｴｨｾ photograph of the soil pipe (fig

3)

around

which a visible opening existed jn the roof. The

instal-lation of insulaLion around window frames is illustrated" in

fig. 18. The lack of a good vapour seal is evident. Heavy

leakage had been reported from the window frame.

LABORATORY REPORTS

(a) Moisture ｾｯｮｴ･ｮｴ of Insulation Batts

Three insulation samples were submitted to the.Uni-versity of Manitoba Testing Laboratories for moisture content

tests. They have been recorded under the University's file No.4

record No. 5544.

The report of the tests was as follows:

Specimen 3-1

A B

Moisture content -

%

of wet

weight 3·73 1.65

1·48

Specimen 3-1 was a sample of rock wool insulation batt

removed from the attic peak of house No. 3-1. This house had

the sample was taken (June

8, 1949).

The unvented attic Deak was exceedingly hot and dry so that these batts were obviously much

wetter at an earlier period. Specimen Awas an unused sample of

Johns-Manville rock wool insulation which is of the type presently

being used by

C.W.H.C.

Specimen B was an unused rock wool sample

of the same type as 3-1. A and B were tested for comparative

pur-pQses in order to learn the moisture content which might be expected

in an insulation batt before installation. There was, therefore,

an indication that moisture due to the melting of the ice layers

behind the batts was retained by them. This was to be expected.

(b) Analysis of Wood Samples

Three wood samples were submitted for analysis to the

Forest Products Laboratory in Ottawa. Two of the samples were

taken from the north eave space of house No.2-I. The wood was

badly water-stained but otherwise did not show evidence of rot or

decay. The third sample was taken from the north space of house

4-1.

This specimen had a pink discoloration which had not been

noted in any other dwelling examined. Only a few sheathing

boards were marked in this manner. The report of the analysis is

quoted below.

IfAll three sample s show a superfi cial growth of fungi,

and the pink-tinted sample is entirely penetrated by fungal

hyphae. None of the wood, however, shows any appreciable

deterio-ration. If moisture can be excluded and tbe wood kept dry, the

development of the fungi will be arrested and no decay will occur."

DISCUSSION

Consideration of the principles already outlined indi-cates that the fundamental factors which affect the occurrence

of condensation are those which set up the greatest vapour pressure difference s :

(1) High relative humidities indoors

(2) Temperature conditions (interior and exterior)

(3)

Wall and roof construction

Conditions are such in the C.M.H.C. wartime rental houses that large quantities of moisture are supplied to the air indoors, and wall surface and inter-space temperatures are below dew point conditions, increasing any tendency for condensation to occur. The manner of insulation application in wall and roof construction

further aggravates the ,problem. These points are discussed in

- '21

-For comrort and economic reasons the present construction

practice is to build houses in which air inriltration is reduced ｾ

a

minimum (by we a t.he r--str-f.pp Lng windows and doors, etc.).

Conf'e-quently the water vapour content of the air through normal living

ｾｯｮ､ｩｴｩｯｮｳ will tend to build up within the house. This, or course,

is cornmon to all newer houses. The wartime dwellings are, however,

more seriously affected in this respect since they are rrequently occupied by large ramilies with young children living in crowded quarters so that excessive moisture sources due to large laundries

and extra bathing may be expected. Furthermore, in the

basement-less dwelling, laundry is usually hung in the living space of the

house. Additional moisture is nearly always added cy humidiriers

or open pans or water. Ventilation by windows and doors is

re-duced to a minimum in order to keep the houses warm. The result

is the tendency ror high relative humidities to exist.

No word need be said regarding Winnipeg's severe winter

conditions in which extended periods at -20oP. _{are not uncommon.}

In the wartime dwellings heating cannot be closely controlled and

temperatures vary ｲｲｯｾ room to room and at dirrerent locations in

anyone room. Mr. G. O. Handegord* or the National Research

Council, in investigating insulation performances in C.M.H.C.

rental houses, round temperature variations or 50°F. between points located six inches below the ceiling (106°F.) and six inches above the rloor (56°p.) in the living room or a basementless bungalow.

At this time the outdoor temperature was approximately 7°F. This

large variation is attribptable to the heating system used in these houses (space heaters located in the living room) and the absence or insulation on the rloors over the cold crawl space. Interior surface condensation around the exterior perimeter or the house, particularly at baseboards, is then to be expected,

ｳｩｾ｣･ the lack of insulation and poor heat distribution to these

areas result in ｳｵｲｲ｡｣ｾ temperatures below the dew point. Since

insulation is proviqed, interior wall conditions may be such as to

result in condensation ｵｮｬ･ｾｳ means are provided to prevent rlow

or vapour into the 'waI1.

Obviously, exterior temperature and humidity conditions

cannot be controlled. Present medical practice advocates the use

or higher relative humidities. Ill-sulation results in fuel saving

and improved comrort. It is evident that the rirst two ｭ･ｮｴｩｯｮ･ｾ

ｾｾ

"Report on a study of Wall Surrace Condensation in Prairie Houses" by G.O.P. Handegord. DBR report R 16, October, 1949.

factors affecting condensation cannot be altered to eliminate the

problem. However, certain precautions taken in wall and attic

con-struction will allow the use of insulation and higher humidities

without condensation. The use of a vapour barrier with low

permea-bility correctly applied so as to form a continuous membrane to

re-duce the flow of vapour into the wall, or adequate attic ventilation to balance space inflow vapour to space outflow vapour is necessary

to prevent condensation. Such a barrier must be applied in the

pro-per 'position, namely on the warm side of the room. Examination of

the photographs and figure 1 illustrate that the insulation (in

combi-nation with a vapour barrier backing) has been installed against the

sheathing without lapping the batt backing across ｴｾ･ inner faces of

the studs. This reduces the effectiveness of the barrier which is not

continuous and also aggravates the proQlem by preventing natural air circulation (due t6 infiltration through the wall) in the space which

would normally be present between sheathing and ventilation.

Further-more, all the one and one-haIr-storey houses studied lack efficient attic ventilators for dissipating vapour to the ..outside.

In contrast to this lack of ventilation in the one and one-half-storey dwellings were the louvre openings present in all

single-storey Lungalows. Other than this slight difference, conditions'

which set up attic condensation in the larger houses were identical in

the smaller type yet there was very little ･ｶｩ､･ｮ｣ｾ or complaints of

condensation in the bungalows. This indicates very definitely the

importance of attic vent_ilators.

Not only does the method which has been used to install

the insulation acgravate the condensation protlem, but such insulation has been applied against the cold surfaces of unheated spaces instead

of along ｴｨｾ warm walls and ceiling. Thus there has been a needless

supply of heat into unusable (with the exception

or

the storage area)

and unoccupied attic eave and peak spaces.

ｾｨ･ Maintenance Department of the Central Mortgage and

Housing Corporation has carried out an experiment in ten of its most seriously affected houses in an effort to end the condensation

problem in the attic spaces. This work was essentially a

re-insulation-ventilat10n jot. Batts were installed according to the present

recom-mended practice shown in figure 2. There was, however, no lapping of

batt backing and no additional vapour barriers. The work was carried

out during March,

1949,

so that the results of their experiment will

not be positively ｫｮｯｾｾ until the coming fall or spring. At the time

the job was being done the men reported water-soaked insulation batts, a film or mould layer on studs and sheathing and the presence of an offensive, musty odour.

23

-Tenant reports of condensation in walls were not common. Ordinarily this would not necessarily indicate that side wall

con-densation was not taking ulace since it ｩｾ not very likely to be

seen within the house although it may cause paint failure on the

outside. However, examination of wall sections in which ｾ･ｲｩｯｵｳ

attic condensation had been reported showed only slight (if any)

evidence of condensation. One possible explanation is that the

vapour can pass through the wood or asbestos shin51e siding finish

more easily than through the roofing material. All attic spaces

are located under the roof which, in nearly all cases, is covered

with an asphalt or composition roofing material. This could be, in

effect, a vapour tarrier and as such, prevents the passage of moisture through the section, and aggravates the problem further by being in-stalled on a cold side of the roof.

Two questions now arise regarding the variation in con-densation formations as found in:

(1) north and south eave spaces of anyone house;

(2) any group of houses.

Assuming similar materials, construction,workmanship and insulation application, it appears that the cause of condensation variation in the spaces of a single house is due only to temperature distribution

through the roof section. The roof on the north side, which is ｳｵ｢ｾ

ject to the prevailing cold winds and at the same time does not re-ceive heat from the sun, obviously has a sheathing temperature below

the dew point for the vapour pressure in the attic. At the same

time the corresponding temperature in the south attic space is more frequently above the dew point temperature for the moisture

con-ditions in that space. The accuracy of this statement would have

to ce verified by temperature-humidity measurements under conditions

which actually exist during the winter months. In explaining group

ｶｾｲｩ｡ｴｩｯｮ a greater number of variables exist. It would be expected that a greater variation in workmanship would occur in a group of

houses than in anyone house. As a result it is probable that some

batta were more effectively installed with respect to Napour barrier

and ventilation possibilities. Obviously, heating and humidity

con-ditions would vary from house to house and this is a very definite

contributing factor to the problem. There is no doubt that

conden-sation does exist in a large number of houses even though in some cases there has been no visual evidence of its occurrence (e.g.

House 6-2), and as a result it has not been reported. Although

only a small proportion of the one and one-half-storey dwellings

are finished with wood roofing shingles, interview reports show

that only 12 out of

46

houses were affected by condensation. This

therefore might indicate another reason for variation in groups of houses.

That condensation lessens the insulatinB value in C·N.H.C.

rental houses is no longer a possibility but a fact. Even if there

is no lowering of the insulation value of rock wool batts due to continued cycles of wetting and drying, i t can be seen from the ac-companying photographs that an appreciable percentage of the hatts become detached when wet due to the excess weight which the staples cannot support and, as a result, a supposedly insulated attic space has a large area which actually receives no insulation protection.

There is no doubt that a large number of the paint failures

in the Winnipeg area are due to condensation. The moisture which

gathers in the wall and attic spaces can easily pass through the ordi-nary wall construction but gathers underneath the impermeable paint layers causing blisters and peeling.

Although no visible decay or rot was noted at the time of the house studies there were reports that films which resembled mould

deposits were present in the wet attic spaces during the spring Ｈｾ｡ｲ｣ｨＩ

thaw. Tne laboratory report of the wood samples shows that fungi

growth was present even though it may now have been arrested. It is

evident that conditions are set up each spring which favour the pro-duction and [rowth,pf destructive organisms that are liable to cause serious structural deterioration if condensation is allowed to

con-tinue unchecked. A continuous check should be kept on the house

during each spring and summer to see if such tendencies arise. It will be noted that no attempt of a detailed breakdown of the data (questionnaire) sheets has been made other than to

indi-cate the extent and nature of the problem. Additional useful

infor-mation might be obtained, e.g. the influence of deliberately added water or the effect of the number of occupants on the condensation

problem. The data sheets have been forwarded to the Division's

Prairie Regional Laboratory at the University of Saskatchewan for such possible future statistical studies.

CONCLUSIONS AND RECOMMENDATIONS

From the principles which have teen presented in the opening

pages of this report, the evidence obtained in the houses examined,

and the discussion which has preceded, the following conclusions are drawn:

(1) The cause of much tenant complaint of leakages from

roofs and ceilings is the existence of attic space

condensation to a very marked degree. Approximately

41

per ｾ･ｮｴ of the one and ｯｮ･Ｍｨ｡ｬｩｾｳｴｯｲ･ｹ dwellings

visited showed some evidence of this occurrence.

25

-by this problem. The need for adequate vapour control

in all houses is amply demonstrated.

(2) The principal factors aggravating the problem in

C • M. H. C • rental hou se s are the tendency toward higher indoor relative humidities, inadequate vapour bar-riers and normal ventilation (due to the method of ap-plication of the insulation) and the absence of ven-tilator openings.

(3)

The main location of the condensation is in attic eave

and peak spaces. The north space is usually most

seriously affected and in the poorest condition.

(4)

Interior surface condensation is due to the tendency

toward the existence of high relative humidities, in-adequate heat distribution and lack of floor insu-lation.

(5)

Conditions in attic spaces during the spring and early

ｓｕｄｾ･ｲ favour the growth of destructive organisms.

(6)

The insulatin5 value of C.M.H.C. one and onehalf

-storey rental houses which were affected by conden-sation has been weriously reduced due to the detach-ment of insulating batts over large areas in the attic

spaces.

(7)

Moisture accumulation in attic spaces of a large

number of houses may be aggravated by the use of a highly impermeable roofing material.

RECOM.MENDATIONS:

It is felt that definite steps should be taken to meet the

problem. Unfortunately all solutions to existing house problems

in-volve considerable expenditure which was not anticipated at the time

of construction. For the over-all problem three remedies exist,

namely:

(1) reduction of interior humidity

(2) use of vapour barriers

APPLICATION !jF REMEDIES TO EXISTING HOUSE ｐｈｏｂｌｅｾｩｓ

(1) Reduction of Interior Humidity:

Tenants are reluctant in this respect since health

authorities advocate the use of higher humidities. Vapour at its

source cannot generally be reduced (i.e. cooking, ｷ｡ｾｨｩｮｧＬ bathing).

Daily ventilation by opening doors·and windows aids in reducing the

relative humidity. It is also possible to eliminate water added for

humidification. It should be realized that a small percentage

re-duction in moisture causes a much larger percentage rere-duction in

condensation. Also, there is a limit to the humidity attainable as

is indicated when windows first "frost up". At this point, windows

merely act as de-humidifiers and condense the additional moisture onto their panes.

(2) Vapour farriers:

Application of a vapour barrier paper is impractical.

However, since many houses will undoubtedly be re-decorated in the

future, it is recoIT@ended that paints which are effective vapour

seals be used, e sg , , aluminum, lead and oil paints, varnishes, and

ｲｵ｢｢･ｾ base paints. . '

(3)

Ventilation:

Ventilation is ｵｾｵ｡ｬｬｹ the most practical and often the

sole method in solving the problem in existing houses. Adequate

cir-culation in attic spaces can be provided by screened louvres in

com-bination with cornice vents (if construction details of the houses

allow this). The area of the openings should be at least

1/4

square

inch per square foot of attic "floor area. Unfortuna te ly, in the

war-time houses, such ventilation also requires a ｲ･Ｍｩｮｾｵｬ｡ｴｩｯｮ job

(since all insulation has been installed on the cold side of the roofs) similar 'to the one which was done by the Naintennnce

Depart-ment in their ten experiDepart-mental houses at a cost of ｡ｰｰｲｯｸｩｾ｡ｴ･ｬｹ

Flirty-four dollars

(t.,34.o0)

per house.

Insulation of ground floors over crawl spaces although costly would produce greater comf'ort and reduce interior surface condensation.

RECOrvrrvrBNDATIONS FOR NEW HOUSE', C.ONSTRUCTION

That:

(1) Insulation be applied in accordance with recommended

practice for such dwellings with adequate overlapping of batt backing

, 27 ,

-(2) Additional separate vapour barriers be applied between

plasterboard finish and batt backing of insulation with overlapped edges on interior stud faces.

(3) Insulation and separate vapour barriers be applied

to the ground floors of basementless houses.

(4)

Adequate ventilation be provided in attic peak and

eave spaces by the use of louvres and cornice vents. A ｭｩｮｩｾｵｭ

total area of opening of ｬＯｌｾ square inch per square foot of attic

floor area is recomraended.

.

The above recommendations are based on the work which nas

already been done by Babbitt, Teesdale, Rowley, the University of

Illinois Small Homes Council and others, and not on the basis of

this report which deals only with the extent and nature of the densation problem and its effect on insulation and structural con-ditions.

AC KN OWLEDGErmN TS

Acknowledgment is made to Mr. H. W. Hignett and kr. H. C. Spence of the Prairie Regional Office of the Central l'iiortgage and Housing Corporation for their continued interest and co-operation. Thanks are due to Mr. G. O. Handegord of the Division of Building Research for his assistance in the preparation of the theoretical

principles outlined. The assistance given by the Maintenance

Department of the Prairie Regional Office, C.M.H.C. was greatly

appreciated. Without their co-operation this report would not

have been possible. REFERENCES

1. Condensation in Walls and Attics by L. V. Teesdale - Journal

Royal Architectural Institute of Canada, Aug. 1938. pp. 185-188.

2. The Diffusion of Water Vapour through Various Building illaterials

by

J.

D. Babbitt - Can. Journal of Research, A 17,1939, pp. 15-32.

3. Condensation of Moisture and its Relation to Building Construction

and Operation by F. B. Rowley, A. B. Algren and G. E. Lund, University of Minnesota Engineering Experimental Station, Tech-nical Bulletin No.5.