Insulation retrofitting : a case history

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Insulation retrofitting : a case history

Strelka, C. S.; Burn, K. N.

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INSULATION RETROFITTING

-

C.S. StreLka and K . N . Burn

Division of B u i l d i n g Research., Eational Research C o u n c i l of Canada

INSULATION FETROFITTING

-

C.S. Strelka and K.N. B u m

INTRODUCTION

In the fall of 1978, the D t v i s i o n had the opportunity to

monitor a case of r e t r o f i t t i n g insulation in a two-storey balloon-frame house sttuated in an older s u b d i v i s i o n of O t t a w a . Because the house is owned by a s o c i a l service organization and m o s t of i t s rooms are used only for occasional meetings, there were no problems o f d i s t u r b i n g t h e

owners with observation activities. On _{the other hand, because there} is a live-in caretaker, the house is kept at a comfortable temperature

at a11 times and may therefore be considered a normal residential

building with minimal occupancy effects. This house is t h e larger part of an uneven d o u b l e .

Initial i n s t a l l a t i o n of insulation above the c e i l i n g was poor, but was corrected about half-way through t h e heating season. The records therefore include the energy consumed for three different

heating conditions: without insulation; with wall insulation, but inadequate ceiling insulation; and with the ceiling insulation i n s t a l l e d as i n i t i a l l y intended.

DESCRIPTION OF HOUSE Exterior

The b u i l d i n g is a two-storey, two-unit, balloon-frame

construction w i t h a 1-mhigh vented a t t i c s p a c e beneath a f l a t roof, built sometime before t h e turn of the century. The exterior finish of

the front (street) elevation facing e a s t is cement stucco on l a t h .

At t h e second floor level on t h i s side of the house there is a s i n g l e glazed, unheated and uninsulated sun room, supported on wood columns

over the f r o n t verandah (Fig. 1). The n o r t h elevation facing a

3 m - w i d e lane has t h e same type of finish treatment (Fig. 2 ) . A t t h e

rear of the house is a one-storey addition, in which the kitchen is

located ( F i g . 3 ) - The exterior f i n i s h of the rear (west) elevation i n c l u d i n g the kitchen a d d i t i o n is a l s o stucco on lath. The unheated

rear entrance porch has aluminum c l a d d i n g . The south wall of the observed p a r t of the b u i l d i n g is not exposed to the external environ-

ment. It forms a party w a l l between the two housing u n i t s and i s constructed of wood frame with board sheathing and plaster lath on

for all exterior walls (Fig. 4). The roof of the buflding is flat, w i t h minimum slope towards the inside roof drain. An attic space is

formed by a frame structure extending about 1 m above the second floor c e i l i n g . There is no p h y s i c a l separation between the t w o u n i t s

in t h i s space.

Interior

The sketch floor plans of t h e observed part of the building with use of i n d i v i d u a l rooms indicated are shown in F i g s . 5 and 6 .

Interior finish on all exterior w a l l s and partitions is p l a s t e r over

wood lath over 13-mm boards. Windows

All windows i n t h e b u i l d i n g are wood-frame single-glazed vertical sliders with allrminum frame single-glazed vertical slider

storm windows attached to the exterior face of the wooden window frame. Basement

Basement w a l l s are constructed of stone masonry approximately

300 rmn t h i c k unfinished on t h e i n s i d e face. The retrofittfng program d i d not include adding insulation to the basement walls.

Heating System

An o i l - f i r e d furnace (Beach L0137, Output 40 150 W) w i t h forced warm air heating system is situated in the basement.

INSULATION RETROFITTING

As already mentioned, both u n i t s of the double-house structure were retrofitted at the same time. The contractor recommended providing

a polyethylene vapour barrier over the floor in the attic space including

the separate a t t i c over t h e kitchen addition and then blowing in loose

cellulose f i b r e insulation t o the thickness of approximately 200 mm over

the full area of the vented a t t i c space. The proposed i n s u l a t i n g value

w a s RSI 6.2. Calculations by t h e authors, based on the volume of

insulatfon the c l i e n t was b i l l e d for, indicate that the resulting value

after retrofitting should have been RSI 5.1.

The same type of insulation m a t e r i a l was used for t h e exterior walls.

In balloon-frame construction the f l o o r joists are supported

on ledger boards on t h e inner face of t h e studs rather than on plates as w i t h p l a t f o r m construction. T h i s makes access to the wall cavities

from above relatively simple. The method followed therefore w a s to fill between the studs from t h e a t t i c space by blowing in loose insulation. The wall cavities below the windaws w e r e f i l l e d using

h o l e s of approximately 25 mm d r i l l e d vertically through the window afXls, The insulation value of the exterior w a l l s was estimated by the

contractor as RSI 2.8; calculations confirm this estimate. Retrofitting w a s cuarple~ed by 20 October 1978.

According to t h e invoice submitted by the contractor to the

owners, 46 bags of insulation (0.33 m3 per bag) were used to insulate the at tic space,

and 42

quantity of mater3al used in t h e insulated areas was calculated as

follows : A t t i c S n a c e s

House

...

Kitchen

...

After 10% reduction for j o i s t s , eec,

...

d

to j o i s t depth

.

.

.

...

d

3

Insulation used

...

...

Exterior Walls

A f t e r deduction for door and window openings

...

Waf1 cavity

...

..

Available cavity volume (20% reduction for framing). 11.1 m3 3

Insulation used

-

...

In February

1979

f i r s t scanned and then p i c t u r e s were taken at various p o i n t s where

the infrared images showed temperature patterns indicating heat losses

greater than normal. At t h e time of this survey, the temperature inside the house w a s 2 4 O ~ . A similar procedure was a p p l i e d to

i n s p e c t i o n on t h e exterior of t h e b u i l d i n g , bur because the o u t s i d e temperature was -15'~~

which

equipment: after approximately half an hour of work, only three pictures

were taken.

The following is a list of representative themgrams taken during t h i s survey together with interpretations of the t h e m 1

conditions they d e p i c t . The areas in rhe themgrams appear as shades of grey varying in Tntensfty f r o m black t o w h i t e illustrating relative surface temperature for t h e same surface material. The coldest areas

are black and the warmest are whlte. When viewed from t h e i n s i d e a well-insulated section crf

wall

because the insulation reduces the rate of heat loss from the inside

sursace to the outside. When viewed from the o u t s i d e a well-insulated section of a wall appears colder than one that is not,because Ehe

insulation retards t h e conduction of heat from the i n s l d e to the

outside surface. The thenmgrm numbers and locations are shown on the floor plans in Figs

-

F i g .

F i g .

F i g .

7: The front elevation of the building showing heat loss through windows, through t h e uninsdated upper part of t h e exterior wall at attic l e v e l , by a i r leakage ar thermal bridges formed by the wood structure and hy air leakage from t h e rminsulated sun room over t h e verandah;

8: The cold p a r t of a wall of t h e meeting r o o m on the f i r s t flanr indicating t h a t insulation is missing;

9 : The corner at the exterior w a l l between the meeting room and the pantry indicating i n s u f f i c i e n t or missing

insulation;

F i g . 10: The c o l d corner in t h e upstairs mail room;

F i g . 11: An exterior shot of the s a m e corner;

F i g . 12: The diagonal line at t h e bottom edge of a dark area indicating a structural membe~ which obstructed t h e downward movement of insulation, resulting in an uninsulated cavity below. This thermograrn a l s o shows

poor insulation ah t h e southwest corner of t h e building. Fig. 13: The ceiling in the second floor -bathroom showing

uninsulated joist spaces adjacent to the exterior wall;

F i g . 14: The ceiling and wall at the outside corner of t h e second floor bedroom showing insufficient insulatlton.

After the thermographic survey and the i n i t i a l evaluation of the thermograms, a physical inspection 0 5 insulation was conducted. As no destructive probing of the exterior w a l l s was permitted, t h i s w a s restricted t o visual inspection of the a t t i c space only. The

Tnspection confirmed t h e thermographic f i n d i n g s . Uneven diszribution of insulation and empty j o i s t spaces especially at the edges and

comers of the roof were caused

by

when the applicator, for lack of space or for h i s convenience, stood

in the open c e i l i n g hatch and f r o m t h i s paint d i r e c t e d the nozzle all around. This resulted in the i n s u l a t f ~ n being stopped by the c e i l i n g j o i s t s perpendicular to the directiun of f l a w . Insulation was thus heaped m one s i d e of most c e i l i n g frame members, but behind t h e j o i s t s ,

t t

on the lee" side, the thickness of l n s u l a t f w was minimal. Close to t h e hatch the spaces were adequately f i l l e d ; in p l a c e s f u r t h e s t from the hatch around t h e perimeter of the c e i l i n g , insulation was t o t a l l y

missing or was minimal in d e p t h (Figs. 15 to 17). This situation was

pointed out to the contrator, who remedied it by adding 26 bags of insulation and raking it t o an even lager over t h e entire floor in the

a t t i c space to the thickness of approximately 200 mm. C e i l i n g Insulation Thickness Before and After Inspection

Theoretically, 15.2 m3 of insulation used in the first stage

in the a t t i c should have covered the entire floor area to the d e p t h

of

200

d

76.17

caused, e . g . , by j o i s t s , should have resulted in an even greater thickness of insulation. According to Bomberg a d S h i r t l i f f e (19781, a layer of

blown cellulose f i b r e . insulation on £1 at surfaces is subj ecred to approximately 20X s e t t l i n g during and after installat-ion.

If

than

inspection of the a t a c confirmed that the proposed thickness was not

i n s t a l l e d . The required thickness of insulation and expected savings

on

26 bags of insulation produced a n addittonal thickness of 100 mm

over the whole attic area.

These calculations and t h e i n s p e c t i o n suggest three possible

c~lclusions:

a) the 5nsulation material settles much more than 20% after befng

b l m in;

b) because two housing u n i t s were r e t r o f i t t e d at the same time, more material w a s used for t h e other u n i t than estimated by

or c) t h e recorded quantity of insulation w a s not a p p l i e d , e s p e c i a l l y

to the a t t i c area.

There are strong indications that the last-mentioned w a s the case,

COMPARISON OF FUEL USAGE BEFORE AND AFTER REXROFI7TING

Table I shows the fuel consumption during t h e heating season: (1) before Znsulatfon retrofitting

(2) for 4 _{112 months when} the insulation in the attic was not

properly i n s t a l l e d

,

( 3 ) after the remedial action w a s taken. Table 1 Aetual F u e l Consumption

As fndlcated in Table I the winter periods of 1978-79 and

1979-80 w e r e 4.5% and 9.5X milder than the winter of 1977-78, on the b a s i s of degree-days. Heating Period (1) O c t . 77

-

-

-

To provide the proper camparism of f u e l consumptfon and to indicate t h e actuel energy savings, t h e fuel consumptim for the

h e a t i n g seasons of 1978-79 and 1979-80 w a s recalculated so that the numbers of degree-days were the same as for the heating p e r i o d of 1977-78. This adjustment is shown in Table 11;

Where: Fuel Consumption, L 8215 6816 5394

A

...

A~

...

AC

-.

Z

DD

...

Z

in

and heating season caliculated;

S

...

Monitoring t h e retrofitting operatfan of t h i s house has shown that even w i t h the b e s t intentions and techniques, the results

of insulating in restricted spaces and closed wall cavities are not always, and probably cannot be, c o q l e t e l y e f f e c t i v e . The job m i g h t

not be completed as intended, unless the contractor suggests, a r the owner requires and is prepared to accept the additional c a s t of,

themnographic inspection after the retrofitting and is prepared to a c t

upon its f i n d i n g s .

Heating f eriod

1977-78 1978-79 1979-80

An example drawn from t h i s case m a y be illustrated using

Fig. 12. The thermogram shows a diagonal framing member in the

exterior w a l l which prevented proper fllling of the wall cavity with insulation. The contractor, after h i s i n i t i a l Inspection, assumed t h i s house to be a two-storey ballam-frame structure. But he could not

have khown that some time in the past a secand storey had been added, The diagonal member in question could have been a part of the o r l g f n d

roof franie or bracing l e f t in t h e wall,

+ DD

,

X

-

Again, inspection of t h e attic space after retrofitting confirms h m important it is for the owner to require the contractor

to dlemcmstrate that the work has been done properly. As shown in t h e

S column in T a b l e If, correction of the situation which included

adding insulation and raking it to an even layer resulted in doubling

the s a d n g s .

CONCLUSIONS

The monitoring of this particular retrofittling operation

demonstrates clearly how, by addjng i n s u l a t l m in exterior walls and

conservation

of

of

will

short time.

The

of

Heating o i l price:

1st heating season after r e t r o f i t t i n g C13.9/L 2nd heating season after r e t r o f i t t i n g C15,7/L

3 r d heating season after retrofitting (Jan 811 C21.81L Assuming

tha-t:

increase by 20% per year, dollars saved over four heating seasons will be:

Heating Season Amount of Fuel

Used,

of

c

The i n i t i a l c o s t of retrofitting to the owner will therefore be recovered in approximately four heating seasons, after which the reduction in annual energy costs represents considerable savings.

This

homeowners

r e t r o f i t t i n g been considered. ACKNOWLEDGEMENTS

The authors express appreciation to t h e i r colleagues

G.D. Schuyler

and

~ichardson

this

Reference

1 Bomberg,

M.

i n s u ~ a t f o n s , Part

1

-

Pub. 660, p . 82-103. Dec. 1978- BIBLIOGRAPHY

Bomberg, M. and C . J . Shirtliffe. Comments on standardization of density and thermal resistance testing of cellulose f i b r e Fnsufarion for horizontal applications, NRCIDBR, B u i l d i n g Research Note 147,

May 1979.

Bomberg, M, and K-R, Solvason. How t o ensure good thermal performance

of cellulase f i b r e tnsufntion: P a r t I

-

NRC/DBP, Building Research Mate 157, March 1980; Part 2

-

Exter-lor w a l l s . NRCIDBR, Building Research Note 158, March 1980. B d e r g , M. and K.R. Solvason. HOW to ensure good thermal performance of

blown mineral fibre insulation in horizontal and vertical

installations. MRC/DBH, Building Research Note 167. August 1980. Burn, K.N. and G,D. Schuyler. Applications of infrared thermography in

locating and i d m t i f y 3 n g building faults. ;Tour. Internat. I n s t .

f o r Consenration

-

Spring 1979.

S h i r t l i f f e , C.J, and H. Bumberg. Blown c e l l u l o s e fiber thermal insulations, Part 2

-

7

*I7

1 3

Mot Hon l t a r e d Note : D l mensl ons a re i n mftlfrnctres F I G U R E 5 G R O U N D F L O O R P L A N

Hot Mnn I tored

Sun P o r c h

(Un insulated)

F I G U R E 6

1.000 I THV

n

8

,PICTURE

ON

WALL

-

MlSSlNG INSULATION

BETWEEN WINDOW

CORNER

OF

FIGURE

13

BATHROOM

C E I L I N G

A N D THERMOGRAM

STRIP

AT

CEILING

A N D

EXTERIOR

WALL

-

MISSING JNSULATI

COLD STRlP

AT

L

CEILING

A N D

EXTER1 OR COR'NER

FIGURE 1 4

F I G U R E 15

A T T I C

- -

TO

A T T I C

- -

E X T E R I O R

- -

14-

D i r e c t i o n o f A i r F l o w

Cell

FIGURE