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Cost of energy conservation measures for new housing
Dumont, R. S.; Orr, H. W.
10171
ISSN
0701-5232COST
OF ENERGYCONSERVATION
MEASURES FOR NEWHOUSING
byR.S.
Dumont and H . W . ~ r r *INTRODUCTION
T h i s report presents n study of t h e costs for the
extra
energyc o ~ l s c ~ v : ~ t j o t ~ mcasures t h a t nrc now b e i n g uscd on a significant nurnhcs o f low-cncrgy hauscs*'
in
Western Canada, p a r t i c u l a r l y i n the Saskntosn a r e a . As o f 1981, approximately 150 low-energy houses have beenconstructed
i n
t h a t part o f Canada.Far an average-sized, contractor-built, new h o u s e , the extra c o s t s for t h e energy c o ~ ~ s c r v a t i o n measures o v e r and above t h e present n i i l i i m u m s t a n d a r d iIrc i n tltc snngc of $30(10 to $5000, which i n c l u r l c 3 normal p r o f i t f o r thc h u i l d e r . The analysis o f the payback on such an e x t r a investment js complicated by the d i f f e r e n t f u e l prices t h a t
e x i s t .
To simplify matters somewhat, f u e l prices are d i v i d e d i n t o separate c a t e g o r i e s . The three price ranges for s h e consumer i n Saskatoon a r e approximately as follows:1. p r e s e n t consumer p r i c e for natural gas (about $2.30/1000 cu ft), which is equivalent t o a space heating f u e l c o s t of a h o u t $3.50/GnJ when burned in a ftlrnacc of 65% seasonal e f f i c i e n c y ;
2. present consumer p r i c e for fuel oil (20 $ / L or electricity 13 #/kW-h), which is now equal t o about $8JGJ a s u s e f u l space h e a t i n g ;
3 . present
OPEC
o i lprice
($41 (Can.) per b a r r e l ) ,which is
equivalent to about $ 1 1 / ~ J as useful space heating.This range of p r i c e s ( $ 3 . 5 0 , $ 8 and $ll/GJ) obviously affects the cost-
benefit analysis of energy conservation measures for low-energy housing.
*
Both a u t h o r s are members o f the P r a i r i e Regional Station, Saskatoon, DBR/NRC.**
For purposes
o f t h i s Note, alow-energy house
i s defined as ahouse w i t h moTe t h a n RSI 5 wall insulation, in o r d e r to d i s t i n g u i s h
t h e s e houses from the large number of new houses with
RSI
3.5 wall insulation.?icasurcs that a consumer would deem economical when prices a r e $ l l / G J a r e
not
attractive when t h e p r i c e is o n l y $3.50/GJ. The intermediate p r i c e of $8/GJ is u s e d l h e r e f o r the b u l k o f t h e analysis. This is the c o s t f i g u r e that most consumers in Central and Eastern Canada face at this time.The
economic analysis i s carriedout
using the simple payback p e r i o d method, t o the exclvsian o f anumber of
life-cycle c o s ttechniques such as t h e present worth or internal rate of return anal- yses. The simple payback p e r i o d f o r an energy conservation measure i s d e f i n e d a s t h e initial e x t r a investment d i v i d e d by t h e f i r s t year s a v i n g s in enerEy cost. For a space-heating energy price of $ 8 / G 3 ,
t h e simple payback period f o r t h e encrgy conservation methods discussed in t h i s paper i s between 4 and 25 years f o r housing i n the p r a i r i e region o f Canada.
The g r e a t advantage of the payback period analysis
is
t h a t itcompares two known quantities, the present p r i c e of energy conservation f e a t u r e s
and
the present cost of energy. A second advantage i s t h a t it i s widely understood by b o t h t h e public and t h e engineeringcommunity. One disadvantage is that the increased value embodied in t h e house investment i s n o t accounted for. On balance, however, the simple payback analysis has attractive features which make i t s use acceptable for comparing t h e economic feasibility
of
d i f f e r e n t levels of energy conservation.An
alternative approach is the p r e s e n t worth analysis,' which uses a discounting t e c h n i q u e to r e l a t e a f u t u r e s t r i n g of payments to t h e i r equivalent value a t t h e present time for comparison with an investment i n t h c p r e s c n t . 'I'fkis a p p r o a c l ~ Ilas becn used to d e t e r m i n e the insulatjnrl requirements i n t h e Canadian ""Measuresfor
Energy Conservation in New Buldings 1978."2 A prescnt worth f a c t o r o f 18 was chosen at that t i m e along with a base energy priceof
S3.42JGJ (corresponding to fuel oil at 1 3 . 2 $ J L ) . When burnedin
a furnace of 6 0 % seasonal efficiency, the n e t energy cost i s $ 5 . 7 0 J G J . This present worth factor o f 18 corres- ponds t o a useful lifetime of 30 years (typical mortgage l i f e ) and amortgage interest rate 3% h i g h e r t h a n t h e r a t e of annual e s c a l a t i o n in t h e p r i c e of f u e l .
W i t h the p r e s e n t w o r t h f a c t o r so d e f i n e d , the simple payback period can be r e l a t e d t o t h e present w o r t h factor. For a present worth f a c t o r equal t o 1 8 , onc could j u s t i f y conservation measures up to t h e p o i n t where t h e l a s t incremental measure used would have a simple payback of
18 y e a r s . W i t h a higher p r e s c n t worth factor, a longer payback p e r i o d
would be acceptable.
ENERGY
CONSERV.4TION MEASURESThe t h r e e measures used f o r law-energy housiny a r c a s follows: air tightness w j t h coritrollcd ventilation, s u - p e r i n s u l a t j o n , and use of south windows for passi.ve solar gain.
I . Air T i g h t n e s s w i t h Controlled Ventilation
I n average new housing i n Canada, air exfiltration accounts f o r approximately 25% of t h e t o t a l heat l o s s from a dwelling. Typically, a i r change r a t e s f o r dwellings arc i n the range of 0 . 3 t o 0.5
air
changes p e r hour during the heating season. In houses w i t h combustion equipment such as oil, n a t u r a l gas, o r propane h e a t i n g , about 0 . 2 a i rchanges p e r h o u r a r c r e q u i r e d t a satisfy the combustion and chimney air requirements of t h e combustion equipment [furnace and water h e a t c r ) .
The results from a sample of low-energy houses in Saskatoon show t h a t it is p o s s i b l e to decrease t h e uncontrolled
air
change r a t ein
a house to approximately 0.05 t o 0 . 1 0 air changes per hour by tightly sealing the house and isolating any combustion equipment if uscd, by means o f a sealed furnace room. The techniques for achieving t h i s low a i r lea- kage a r e described in t h e booklet "Low Energy Passive Solar H o ~ s i n g . " ~To d a t e , forty I~ouses incorporating t h e s e a i r tightness techniques have
b e e n tested u s i n g a portable fan a p p a r a t u s . The air leakage o f the w e l l sealed houses is approximately 1/3 t h a t of s t a n d a r d housing i n t h e Saskatoon area.
The air-vapour b a r r i e r installation is the crucial operation i n assuring air tightness i n t h e houses. I n s t a n d a r d houses t h e vapour
barrier is u s u a l l y 50 prn p o l y e t h y l e n e and t h e j o i n t s are
n o t
caulked or s e a l e d . In the upgraded case, 150 pm p o l y e t h y l e n e i s u s e d andt h e j o i n t s a r e c a r e f u l l y sealed u s i n g a non-hardening c a u l k i n g compound The time to install t h e vapour barrier to t h e upgraded standard i s about 6 person-days of l a b o u r . F e r a s t a n d a r d vapour basrier, about 1 person-day of labour is involved. Thus t h e n e t extra l a b o u r charge i s 5 person-days. The c o s t s are presented in T a b l e I .
Cantrolled ventiIntion using an air-to-air I~cat exchanger
Controlled ventilation i s necessary f o r houses
with
upgraded air tightness. Because t h e house i s r e l a t i v e l y t i g h t it i s possible ta u s e an air-to-air heat exchanger. Canadian-made a i r - t o - a i r heat exchangers a r e available a t allout $425 F.O.B. i n Saskatoon. The c o s t of a u n i t i n c l u d i n g the installation charge is presentedin
T a b l e 2 .
Tf a combustion f u r n a c e is uscd in a relatively airtight house, p r o v i s i o r r must I)c made f o r the s u l ~ p l y of combustion a i r and chimney i . Scver;tf a p p r o a c h e s arc p o s s i b l e :
1. u s e of n d i r e c t outside a i r supply to the furnace through s p e c i a l
d u c t i n g ;
2 . u s e o f a s e a l e d furnacc room with a duct t o t h e outside; and
3 . use o f an outside a i r duct t o supply outside a i r t o the huuse; t h e f u r n a c e air i s t a k e n from t h e l ~ o u s e . Normally t h e o u t s i d e a i r duct is connected to t h e return air plenum on the furnace to
With appro:lches Nos. 1 and 2, n s u p p l y o f outside a i r must be provided f a r t h e occupants of t h e house. T h i s o u t s i d e air can
be
provided at a low energy c o s t if an air-to-air heat exchanges i s used.With
approachNo.
3 t h e air-to-air heat exchanger i s notr e q u i r e d .
Care must
be taken, however, to e n s u r e thar s u f f i c i e n ta i r
flowis
maintained to p r o v i d e adequate ventilation f o r the occupants.A number
of
reports have presented cost data on t h e total extra c o s t s for insulation beyond t h e presentminimum
standards. The '%~uilders Guide r o Energy Efficiency i n New ~ o u s i n ~ , ~ ' 4 produced for HUDAC and the Ontario M i n i s t r y of Energyin
1980, presents cost datnfor walls, bascmcnt walls and c e i l i n g s . These d a t a are presented as t h e incremental c o s t s beyond the m i n i m u m standards. Ilurnont, Besant
and ~ c h o c n a u s p r e s e n t c o s t d a t n for a I n n m2 bungalow w i t h a preserved wond fuutlcl3tion. 'J'hc N:~tion:al llcscarch Cozlncil i n t h e "Commentary o n Mcasurcs for Ericrgy C r ~ n s c r v a t i o n
in
Ncw l l u i l d i n g s 1978,"fi presents cost data developed by a consultant. ~ e d l i n 7 h a s i n i r i a t e d a study of supesinsulation casts, and h i s results were made available f o r t h e costs o f double s t u d w a l l canstruction. A paper by Besant,Dumont and schoenau8 includes these figures. Enercon Ltd.
of
Regina h a s prepared a comparative cost study9 f o r superinsulated walls.The c o s t s presented by the various authors are summarized i n Table 5 .
The incremental costs for ceiling insulation are
in
close agreement between t h e five reposts, varying from 85.5 t o 110 #/m2 RSI. The c o s t s for t h e concrete basement wall i n s u l a t i o n a r e also in close agreement -244
and
249 g/m2 RSI. For t h e preserved wood foundations, t h e two costs vary from 103 to 155 #/m2 RSI. It is believed that t h e h i g h e rfigure i s caused by t h e inclusion o f t h e c o s t o f t h e gypsum s h e e t i n g i n t h e h i g h e r c a s t estimate.
The
major d i f f e r e n c e i n c o s t s f o r t h ei n s u -
lation of t h e concreteand
wood basements is due to the presence of studding in the wood basement,which
g r e a t l y reduces the c o s t of the structure to hold the insulation.With
t h e concrete basement insulated o n t h e i n s i d e , the cost of t h e structure to hold the insulation i s as i g n i f i c a n t c x t r a . For t h e above-grade walls, the c o s t s of the cxtra
r u a E l i n s u l a t i o n a r e i n a range of 0 to 1047 #/m2
RST.
T h i s variation is, ;tr f i r s t glxncc,
d i f f i c u l t to reconci l c .A morc clct;i i l c d colnl~irrisorl o f the cost figures produccd by t h c various a u t h o r s f o r wall i n s u l a t i o n a r c presented i n Fig. 1. The c o s t
for t h e b a s i c wall ( e x c l u d i n g s i d i n g and i n t e r i o r gypsum board) is S 1 3 . 4 4
/mZ
fos a standard 38 x 89 mrn wall w i t h fibre~lass b a t ti n s u l a t i o n . O f t h c seven d i f f e r e n t s e t s o f cost f i g u r e s p r e s e n t e d , some were originally p r e s e n t e d as the extra c o s t for t h e more h i g h l y i n s u l a t e d wall. In o r d e r to p r o v i d e n more consistent basis f o r comparison, t h e total cost f o r t h e w a l l s , rather than the extra cost, i s p l o t t e d i n this figure. The total cost was calculated by adding t h e
extra
c o s t to t h a t of the basic wall which i s $13.44/m*.As can b e seen
from
the d a t a t h e r e is a considerable amount of s c a t t e r i n t h e p o i n t s . F o r conveniencesake, t h e
wall i n s u l a t i o n l e v e l s are d i v i d e d i n t o two groups, the s i n g l e stud and the double s t u d designs.Single
stud designsFor the single stud designs, t h e lower incremental c o s t s a r e
generally based on
the
use of r i g i d i n s u l a t i n g board t o replace thec o n v e n t i o n a l s h e a t h i n g materials such a s p l ~ w o o d , particle board o r gypsum board. With this approach, the extra wall c o s t i s only t h e cxtra m a t e r i a l cost f o r t h e i n s u l a t i n g board r e l a t i v e to the con- v e n t i o n a l sheathing plus a c o s t for e x t r a wall bracing t o p r o v i d e s u f f i c i e n t r a c k i n g strength. A t t h i s p o i n t t h e o b j e c t i o n can b c
raised, however, t h a t one is no l o n g e r comparing equal walls i n
terms o f quality of construction. T h e argument goes that a wall w i t h plywood or comparable s h e a t h i n g m a t e r i a l i s superior co a wall s h e a t h e d w i t h an insulating board w i t h low d e n s i t y and low tensile strength. The resolution of this argument i s beyond the scope of t h i s paper.
Up t o a n i n s u l a t i n g l e v e l o f a b o u t RSI 3.5 t h e insulating boards may be used w i t h conventional 38 x 89 mm studs. Beyond t h i s wall
insulation level, 38 x 140 m m studs p l u s i n s u l a t i n g board may be used t o a c h i e v e an insulating value of about RSI 5 - 3 . Beyond this insu- lating level, 38 x 190 m s t u d s may b e used, although t h e double stud wall appears to h e more popular f o r these h i g h e r i n s u l a t i o n l e v c l s . The less expensive s i n g l e stud designs have an incremental c o s t slope of about 220 $/m2 RSI, a s shown in Fig. 1.
Double stud d e s i e n s
As shown in F i g . 1, t h e costs for the double stud designs e x h i b i t
a l a r g e amount o f s c a t t e r , with a c o s t
difference
o f about $7/m2between thc h i g h e r and lower values. It
is t h e
a u t h o r s ~ j u d g m e n t t h a t t h e upper figures r e p r e s e n t a more up to d a t e estimate of t h e incre- m e n t a l c o s t s for the double stud wall d e s i g n s . As can be seen from t h egraph, a
discontinuity
occurs in the price l e v e l s when t h e insulation l c v c l exceeds RSI 5.3 and a double stud wall design is used. Them a j o r c o s t incsomcnt is due to the labour and material c o s t of t h e cxtra s t u d w:111, O n c c t h c cloublc wall h a s been c o n s t r u c t e d , however, the i ~ ~ c s c m c n t a l c o s t f o r c o r i s t r u c t i n g tllc tlljcker wall i s a g a i n r e l a t i v e l y
law.
'I'he e x t r a costs f o r t h e wall. included t h e costs for t h e e x t r a f i n i s h i n g materials a t wlndows and doors to accomodate the greater wall
thickness.
Not included in t h e figures, however, a r e s h e extrac o s t s f o r the roof
and
siding to accomodate t h e extra wall thickness. Also n o t included ( w i t h the exception of the H e d l i n flgures7) is any charge f o r the cxtra foundation o r lost space in the dwelling. The e x t r a s i d i n f i r e q u i r e d because of the increased wall rhickness, and thecxtra r o o f area required ta m a i n t a i n the same r o o f overhang, a r e n
minor e x t r a c o s t . These additional c o s t s a r e approximately as follows for a bungalow:
s i d i n g c o s t
Roof cost
of additional floor area (Masonite s i d i n g ) of additional f l o o r area
(Asphalt s h i n g l e s )
With the wall thickness increased
from
t h e srandard 8 9 mm s t u d t o300 mm, the extra cost for t h e s i d i n g and roof f o r a 12
m
x 8.5m
bungalow would be 41 x[i"~O~,8n]
x $20.50 = $ 1 7 f this worec o n v e r t e d to an additlon'al chargk a g a i n s t tlze insulation, the cost for t h e wall area would b c equivalent t o 37 g/m2 RSI. As can b e seen from Table 3 , these extra costs a r e relatively small (<30%)
for
even t h e most inexpensive cost f i g u r e s presented,The e x t r a cost f o r the space r e q u i r e d for the t h i c k e r wall i s a n o t h e r f a c t o r that should be considered. A t one extreme, one could claim that t h e ~ e i s
a
c o s t o f about $500/m2 of lost f l o o r space, ast h i s
is
t h e average cost of f i n i s h e d spacein
an average house. With a t h i c k e r wall u s i n g & m 2 o f space, for example, there would b e an e x t r a c h a r g e of $4000. A t t h e o t h e r extreme, t h e r e is t h e argument t h a t t h e lost space has na v a l u e whatsoever. The approachi s
taken that ground space outside the house is used, not f l o o r space, f o r t h e extra w a l l thickness, and t h a t the c o s t of that space for an average lot is o f t h e o r d e rof
$30/m2 or l e s s . Provided the housei s
designed p r o p e r l y , no extra foundation is needed for the t h i c k e r wall, as the extra insulation i s cantilevered outside t h e foundation. The t w o options a r e shownin
F i g . 2.Thc second option of c a n t i l e v e r i n g t h e extra wall insulation appears t o b e t h e bctzer
of
t h e t w o strategies and thus the extrac o s t s f o r the wall space should bc only a relatively minor charge on the extra i n s u l a t i o n f o r t h e w a l l s .
Beyond an i n s u l a t i n g value
of
about RSI 5 , t h e useof
a double s t u d w a l l h a s advantages o v e r the s i n g l e s t u d designs. A particular advantage of t h e double stud d e s i g n i s that it allows the placement of t h e vapour barrier on t h e outside o f the inner studwall.
With this technique, t h c electric wires may be placedon
the warm s i d e o f the vapour b a r r i e r , t h u s a l l o w i n g the vapour barrier to remain f r e eof penetrations. A shcmatic of" a double stud
wall
is shown in F i g . 3 - To d a t e , about t e n of t h e s e lrouses u s i n g double stud walls have been c o ~ ~ s t r u c t e d i n tllc Saskatcson area, w i t h sevcral morein
British Columbia, Alberta, Manitoba, O n t a r i o , and p a r t s of Saskatchewan. The material and labour
c o s t s
f o r a double stud wall are higher than t h o s e f o r a m i n i m u m standard wall.One contractor'' now
specializing
in this
double wall cons- truction estimates t h a t h i s t o t a l incremental c o s t s are equal t o the extra materials plus $5.50 m2 of wall surface. The total cast f o r a wall withRSI
6 . 3 is presented in T a b l e 4 .Another advantage o f t h e double wall construction
is
that very large amounts of insulation can h eadded
withsuch
a design.The
o n l y extra c o s r s a r e f o r t h e insulation, the t o p and bottom p l a t e s , d r y w a l l r e t u r n s and t h e
e x t r a
roof and s i d i n g once the doublc wall is built. Several h o u s e s using RST 10.6 walls have been constructed using the doublc wall design shown. Y e t another advantage of thedouble wall i s that t h e c o s t o f t h e conventional vapour barrier is reduced because no plastic pans or wall vapour barrier at the conventional location are required.
In summary, the incremental c o s t s for t h e insulation are as follows: ceiling
-
1 1 0$/m2;
basement walls [concrete) - 247 $/m2; basement walls (preserved wood) - 155elm2.
Because t h e above grade walls have a discontinuous incremental cost, the w a l l costs a r e presented i n Table 5 f o r a number of discrete incremental steps. The additional costs for the e x t r a roof and s i d i n g t o accomodate the greater wall thickness axe
included.
One argument f o r increasing t h e insulation levels
in
housing is that a t v e r y high l e v e l s of insulation it becomes p o s s i b l e to reduce the size and complexity of t h e h e a t i n g system considerably. Aconventional forced air furnace and duct system can be replaced with either a smaller furnace or electric baseboard heater, resulting
in
savings of up to $1000 on t h e initial c a p i t a l cost of t h e heating s y s t e m . Assuming t h a t an average house h a s a surface area of 300 m2and
t h a t t h e average increase in R value due to the superinsulation i s RSI 5, the c o s t s a v i n g due t o t h e sarnller heating system couldbe
2
$ 1 0 0 q . x 100 #/dollar
,
67 ,,$RSI
300 rn2 x 5 mzmoC/WThese il l u s t s n t i v c f i g t ~ r e s i n d i c a t e t h a t t h e lltrueTQcas o f extra insulazion c a n bc r ~ d u c c d owing t o COST reductions in t h e ovcr-
a l l system.
3 . Uneraded South Windows
The solar heating e f f e c t of s o u t h windows can he substantial in most populated p a r t s of Canada. Table 6 presents data from a report by ~asakatll on the
net
h e a t gain f o r windows facing the cardinalp o i n t s . Results are p r e s e n t e d f o r Swift Current, Saskatchewan, which h a s a climate much l i k e Saskatoon.
N o t e t h a t f o r a double g l a z e d window, t h e net heat gain i s
+549 MJ/m2 f o r a s o u t h orientation
and
-899 W/m2 f o r a north orientation. Awall
insulated t o a l e v e lof
RSI 3.5 would have a n c t heat l o s s of 103 ~ ~ / m 2 - y r for a south exposure. Thus the n e t h e a t g a i n for'a double glazed south window relative t oa
wall with RSI 3.5 i s 5 4 9 - (-103) = +652 ~ ~ / r n Z . y r .If
t r i p l e g l a z i n g i s used, the n e t h e a t g a i n increases to 1008 M J / ~ ~ yr c ~ m p a r e d t o a w a l lwith
RSI
3.5. F u r t h e r improvements may be madeby
using q u a d r u p l e g l a z i n g or d u a l glazing with n i g h t i n s u l a t i o n . In at y p i c a l house tllc window area is about 10 to 1 5 % of t h e f l o o r
a r e a abovc grade. Thus a standard bungalow would have about 13 m 2 of window. I f 80% o f e h i s area (10 m2) were on t h e south facade and t r i p l e g l a z i n g were used, alrout 10 G J per h e a t i n g season would b e gaincd on an avcrngc house in Saskatoon, using this analysis.
The u s e f u l passive gain
from
southwindows
will be reduced fora v e r y highly insulated house, however, because of t h e reduced period o f t h e
year
f o r which purchased heat is r e q u i r e d . Thus the useful h e a tgain
would bereduced
to well below 1800 ~ ~ / r n 2 -y r .
It could b e as low as 600 b~Jm2.yr.The extra c o s t s associated w i t h placing t h e major areas o f g l a z i n g an the s o u t h s i d e o f t h e house are g e n e r a l l y very small, p r o v i d e d that t h e o r i e n t a t i o n of the Lot i s suitable. The c o s t s f o r upgrading the windows t o triple g l a z i n g rather than double g l a z i n g will vary in t h e range o f 20 to 50% extra depending on t h e window s t y l e .
The approximate simple payback period on t h e upgrading may be determined by u s i n g t h e p r e v i o u s l y mentioned figures. The calcula-
tion is presented
i n
Table 7 for a s o u t h window in Saskatoon. Altllough the payback period for t h e triple glazing o p t i o n i s rela- t i v e l y long, t h e increased comfort and r e d u c e d condensation problems would serve to reduce the t o t a l c o s t to t h e owner.In the case of e a s t o r wcst f a c i n g windows, t h e energy savings jn the Saskatoon a r e a for t r i p l e glazing over d o u b l e glazing amount
t o 4 2 5 ~1,~/rn"?~r.
WIG
~ a y h a c k period is reduced to 10 years. CASE STUDY - RESIIIENCE LOCATED IN SASKATOONAs w i t h most investmcnts i n energy c o n s e r v a t i o n , t h e phenomenon of d i m i n i s h i n g r e t u r n s is p r c s c n t . T h m s t h e c o s t to save the first
III (;.I u year in a l~ousc E~catjng b i l l by reducing t h e heat requirement From 1SO to 1413 G J i s v e r y much l e s s than t h e c o s t to save 1 0 G J a year by reducing t h a t same house from 20 G J / y r t o X O GJ/yr.
To
o f a reference house located in Saskatoon, Saskatchewan is p r e s e n t e d . The reference house i s built to the current (1980) minimum e n e r g y conservation standards f o r this location. The insulation, vapour barrier,
and glazing
s t a n d a r d s a r e presented i nTable
8 .A number of d i f f e r e n t sequences might be followed in up- grading t h e thermal behaviour of the house. The f i r s t and likely most cost-effective alternative, A,
is
to maximize t h e u s e f u l passive g a i n , upgrade the vapour barrier and a i r t i g h t - n e s s , increase t h e insulation levels, install an exhaust air heat recuperator, u s e t r i p l e g l a z i n g and again increase t h e insu-l a t i o n l e v e l s . A l t e r n a t i v e B simply involves an increase i n insulation.
As t h e house is at t h e design stage o n l y , it is possible to reorient the b u i l d i n g to maximize the passive solar gain. (With
a n actual housc, this may not be possible because o f obstruction from a d j a c e n t b u i l d i n g s or o t h e r structures.)
Using t h e computer program HSLD,12 a program for calculating residential h e a t l o s s ,
and MSUNPR,
1 2 a program f o r calculating t h e month-by-month behaviour of a house having substantialinternal gain and passive solar gain, it was possible t o estimate t h e annual h e a t s a v i n g s from t h e various measures
in
both alter- n a t i v e s A and B .For the standard house the annual space h e a t i n g energy con- sumption is equal to 98.7 G J . (With a combustion furnace of 0.6
efficiency, t h e energy c o n t e n t
o f
t h ef u e l
wouldbe
165 G J . ]The
annual loads f o r the house u s i n g upgrading alternative A
are
presented i n T a b l e 9 . As can be seen from t h e Table, t h e passive gain increase is t h e most c o s t effective of all the measures,r e q u i r i n g o n l y a site orientation change at no extra charge provided t h e l o t is s u i t a b l y oriented. The next most cost e f f e c t i v e measure i s t o increase t h e basement wall insulation t o RSI 2 . 2 f u l l height, w i t 1 1 a payback period
of
4 . 1 yr. By upgrading the air-vapourbarrier to r c d u c e t h e a i r change to 0 . 2 / h , the payback period is calcttlated to I,c 4 . 2 yr, Increasing the insulation lcvcls as
shown in ~ t c p 4 , TabIc 9 results in payback pcriads ranging t o
14 years.
The installation of the air-to-air h e a t exchanger (step 5)
reduces t h e annual space h e a t i n g load to 28.9 GJ/yr, and has a payback of 1 0 . 9 yr. Triple glazing ( s t e p 63 has a payback of 13.5 y r . Furtl~cr i n c r e a s i n g t h e insulation as i n step 7, demons- t r a t e s payback periods ranging to 26 yr.
The cumulative t o r a l c o s t of the seven upgrading measures would equal $5021; w i t h that investment, the annual space heating load is
reduced
from
99 t o 14 GJ/yr. If upgrading steps 6 and 7 areeliminated, thc cumulative t o t a l cost o f the upgrading measures is $3016; as a "package" f o r a new house the measures would reduce the annual space h e a t i n g load from 99 t o 29 GJ/yr.
The payback periods
for
Alternative B , t h a t of increasing t h e i ~ l s u l a t i o n l e v e l s o n l y , are presented in Table 10. The f i r s t increase i n t h e insulation levels h a s a payback p e r i o d of about X yr, t h e second increase a payback period o f 13 yr, and t h e t h i r d an increase o f about 21 yr. The t o t a l e x t r a c o s t for the t h r e e measures is $3450, and the annual space heating load i s reducedfrom 99 to 45 C J / y r . From an observation of alternatives A and B, it can be s e e n that t h e inclusion of passive gain, air tightness,
and an a i r - t o - a i r h e a t exchanger can produce a more energy c o n s e r v i n g house t h a n can superinsulation alone.
A presentation
has
been made of theextra
c o s t s f o r new housing of a number o f measures designed to reduce space heating c o s t s . The measures used to reduce t h e energy consumption i n new houses may be categorized as follows: (1) a i r t i g h t n e s s w i t h controlledventilation; ( 2 ) s u p e r i n s u l a t i o n ; ( 3 ) u s e of the south windows for passive solar gain.
The
approximate c o s t s f o r these measures 011a new house in Saskatoon, and the simple payback p e r i o d based on a space heating energy price of $8/GJ are a s follows:
Simple Payback Period yr. 1 . Air t i g h t n e s s
Irtlproved vapour barrier $500 Air-to-air heat exchange^ $565
2. Superinsulation
C e i l i n g insulation increased from:
RSL 4 . 9 to RSI 6
US1 6 to RSI 7 RSI 7 to RSL 8
IS1 8 t e RSI 9 Wall insulation increased frm:
RSI 2 . 2 to RST 3 . 5 4 . 2 RSI 3.5 to RSE 4 . 9 13.5 RSI 4 . 9 t o RSZ 6 . 3
(including benefit of increase
i n a i r tightness) 18.1
Basemct~t wall insulation increased from :
RSI 1 . 4 ( 6 0 0 m below grade)
to RSI 2 . 2 full h e i g h t 4 . 1 R S I 2.2 t o RSI 3 . 5 9.0
R S I 3.5 to R S I 4.9 21.9
Basement floor insulation increased from:
RSI 0 to RSI 0.88 6 . 1
AS1 0.88 t o RSI 1.7b 1 5 . 7
3 . Reorientation of w i n d o w s to south $0 Use aF t r i p l e ~ l a z i n f i $507
In o t h e r parts of Canada with d i f f e r e n t fuel
prices,
climatesand
construction costs, t h e analysis will be somewhat d i f f e r e a t . However, t h e numerical results presented i n t h i s paper are likely to be applicable i n mostparts
of
the Canadian prairie. Such an a n a l y s i s should logically be extended to the o t h e r major cltmatic zonesin
Canada.REFERENCES
ASHRAE Handbook and Product Directory, 198 0 Systems, New Y o r k , 1980 Chapter 45.
' ~ e a s u r e s for Energy Conservation in New Buildings 1 9 7 8 . National Research Council of Canada, Associate Committee en the N a t i o n a l
Building Code, Ottawa, 1978.
(NRCC
16574)3
Low Energy Passive Solar Housing. U n i v e r s i t y of Saskatchewan, Dept.
of Mechanical Engineering, Saskatoon, Saskatchewan, 1979. 4
B ~ i i l d e r s Guide to Energy Effi.cjcncy i n New Housing. Housing and
l l r b a n L)evelo])mcnt Association of Canada and O n t a r i o M i n i s t r y
of Energy, 1 9 8 0 . A v a i l a b l e from H U M C National Office, 15 Toronto St., Toronto, O n t a r i o .
' h m o n t , R.S., Besant,
R.W.
and Sehoenau, G.J. Recently Constructed PassSve Solar Buildings i n Saskatoon. P r o c . , Conf., Solar Energy Society of Canada I n c . , Charlottetown, P E I , August 1979.G~ommentary on Measures f o r Energy Conservation
in
New Buildings. National Research Council o f Canada, Associate C m i t t e e on the National Building Code, O t t a w a , 1978. [NRCC 16945)7 i ~ e d l i n , C. P., Narional Research Council of Canada, Division of
Building Research, Saskatoon, Saskatchewan, private communication. 8
Bcsant
,
It.
W. , I)mont, R. S.
and Schoenau, C . J.
Tlle Saskatchewan Conservation Ilouse - A year of Pcrfarmance Data. Proc., Conf., S o l a r Encrgg Society e f Canada I n c . , Charlottetown, P E I , A u g u s t1079.
9
Lange, L . , Enercon B u i l d i n g C o r p o r a t i o n , Regina, p r i v a t e communication. 1°~ibson, R.
,
Custom Solar B u i l d e r s , Saskatoon,
Saskatchewan, private"Elarakat, S.A. Solar Heat Gains Through Windows in Canada. National Research Council of Canada, Division of Building Research, NRCC
18674, October 1980.
1 2
Dumont, R.S.
and
Harnlin, T. A Simple Computer Program f o r Estimating the Space Heating Requirement o f Residences. To be published.TABLE 1
COSI' CO~IFARISON 1"CaR STANlIhRF) AN11 UPGRADED
VAPOUR
BARRIER
Standard
Vapour Barrier Upgraded Vapour Barrier50
urn
polyethylene
-
300 m2 at 1 2 . 8$/m2
1,ahour charge
- 1 person-day at $75/d
Upgraded vapour barrier
Less: standard vapour barrier
Extra
cost for upgraded vapour barrier150 pm polyethylene
- 300 m 2 at 3fl
#/m2
$ 90.00Acoustic31 sc;llant caulking coml~ound
24 tubes a t $.'t/tul>a 7" t1)II
J.abour charge
-
6 person-days at $75/d 450.00 $612.00TABLE
2COST
FOR AIR-TO-AIR HEATEXCHANGER
Cost o f a i r - t o - a i r heat exchanger
C o s t of dehumidistat controller
C o s t of d e f r o s t control timer I n s t a l lation cost
TABLE 3
BEYOND
THE 1979MINIMUM STANDARDS
Basement
Walls
Concrete PreservedWalls Ceiling Wall Wood
6 Commentary 37 9 104 x i c ~ g l c stuil 3 90 85 double stud h m o n t and Besant 143 110
Schoenau5 single stud
Durnont and Besant 196 8 5
~choenau5 double s t u d Builders ~ u i d e ~ O to 1047 104 single stud Ensrcon 9 237 s i n g l e stud 344 double s t u d
Note: The figures presented a r e t h e extra c o s t s for increasing the insulation resistance of 1
m2
of surface by I u n i t o f thermal resistance. The wide variation in costs is explained in the text,TABLE 4
NI:'F EX'TRA IIOST FOR
INSULATION
FOR
DOUBLE- STIIUWALL
CONSTIEUCTIONBasic wall
38
x
89mm
s t u d s at 600mm
on c e n t r e w i t h 131 ywood s h e a t h i n gDouble s t u d wall
I n n e r w:1L1 - identical t o basic wall w i t h addit ionaL 1Stl Vrn polyethylene
O u t c r wall - s i n g l e stud d e s i g n with no s t r u c t u r a l headers; t o t a l wall t h i c k - ness 267
mm
Extra materials cost per square metre o f wall I n s u l a t i o n - fibreglass batt
-
RSI 4 . 2 3Outer studs and p l a t e s 2 . 0 0
Vapour b a r r i e r - 150
urn
n.30Plywood t o p and bottom plates (including interior walls)
Drywall returns 0.50
Total extra
material
c o s t 7.20Extra labour c o s t A-5 -50
T o t a l cost $12.70
--
7
TABLE 5
WALL
COSTS
FORINCREASING INSULATION
LEVELSWall Design
Wall
Thermal
Wall Cost* perResistance, Unit Area,
rn2
*oc/w
$/m*
I . Basic wall 38 x 89 mm s i n g l e stud with g l a s s f i b r e b a t t s 2 . 38 x 8 9 m m s i n g l e stud with g l a s s f i b r e b a t t s and RSI1 . 4 insulating foam sheathing 3.5 16.02
3 . 38 x 140 m m single s t u d w i t h g l a s s f i b r e b a t t s and RST
1 . 8 i n s u l a t i n g foam s h e a t h i n g 4 .!I 20.54 4. 38 x 89 mm double s t u d with
lass
f i b r e b a t t s ; total insulation
t h i c k n e s s = 267 m m 6 . 3 2 8 . 3 5 5. 38 x 89 m d o u b l e s t u d with g l a s s
fll-lre batts; total insulation
thickness = 450 rnm 1 0 . 6
*13xcluding c o s t of i n t e r j o r gypsum board and exterior f i n i s h , hut i n c l u d i n g costs f o r extra f i n i s h i n g work and extra roof and s i d i n g
TABLE 6
Single
pane
Double pane Triple paneNET
SOLAR HEAT GAINDURING HEATING SEASON
FOR SWIFT
CURRENT, SASKATCHEWAN( ~ ~ / r n z
.yr)
South East
TABLE
7PAYBACK ANALYSTS FOR TRIPLE
GLAZING
INSASKATOON
- SOUTI3WINDOW
North -2457
Double g l a z e d south window (basic wall)
Triple glazed south window
N et h e a t g a i n by going from double to
triple g l a z i n g
N e t Solar Gain, cost, $/m2 ~ ~ / r n 2 .
y r
(inc 1. frame)Energy saving p e r square metre assuming energy
c o s t
of
$8/GJ $ 2 . 84/m2-
yrTABLE 8
IZEFERENCE HOUSE DESIGN
llousc Type Ceiling Walls Windows - s o u t h -east -west - 110rth Doors Basement w a l l s -above grade -helow g r a d e F l o o r Vapour barrier Tnternal h e a t gains Wall exterior surface
absorptivity Roof exterior s u r f a c e absorptivity E x t e r i o r surfaccs film h e a r transfer coefficient Tns i d e tcn~pcraturcs - m : l i n f l o o r - bnscment Annual i ~ t i x i l i a r y space h e a t i n g e n e r g y r e q u i r e m e n t
Bungalow with R111 bnsemer~t Area, R Value, m 2
--
m 2-
QC/IV 96 4.9 61.8 2.2 SOurn,
n o t caulked 708W
from electricity 179 W from h o t water I l n n u a l space h e a t i n g c o s t w i t h energy at $8/GJ (equivalent to electricity at 2.S8$/kW-h,
or fuel o i l at 20&/I,
w i t h a f u r n a c e w i t h a seasonal efficiency of O . h 5 % ) $789-
" l i x c l t ~ r l i ~ ~ ~ : ~ l - o u n J o f f c c t : l ~ n ~ r s c vnIrrmc = 4 I l m"; : ~ i r C ~ I : B J I ~ C r;1tp = [ ) . * i / l ~k W QJ M E: r m
a
.=
-
2
h W .rl 0 +.' m o P) v x al N 1 - A -0 d 1 1 0 0 V 1 - e cr O--. I - a s4 -4 u C m m n U C +zvJ 4 t d P k +I Y - - I w e n C H3 . n h * d 4 N I D N L O O = ~ O I
4 r - m
. .
~. * . .
m - e r o a r - r r - . *-h & n dl- e m d m o n m m
FIGURE
14 4
I
I
I 1 I I I4 4
BUILDERS GUIDE
4 0 0 HEDLlN EXCL. F W N D A T I O N COSTIT 7
HEDLlN (1NCL. F O U N D A T I O N COST)
COSTS OF WOOD FRAME WALL AS A FUNCTION OF TI4ERMAL RESISTANCE
3 6
3 2
THIS STUDY
- V DUMONT, BESANT. SCHQENAU~
-
A ENERCON' -
-
-
-
- A & - - I-
0 i-
SINGLE STUD1
.
.W A L L B U I L T I N W A R D
. - -
NOTE
W A L L B U I L T O U T W A l R D
TWO
POSSIBLE OPTIONS
FOR LOCATIONOF
EXTRA WALLINSULATION
Z reated cardboard
insulation stop ,
acoustlcai ssabnt
7.5 rnm (5/16 in) plywood 150 pm (6 mr!) wpbur b a r n
39 X &rnm (2 I X 3 in) stud 400 mm (16 in) O.C.
5 3 8
x
89 mm (2x
4 in) stud 40 mrn (16 in) 0 . Cs h e a t h i n g a r
building paper and siding- RSI 4.9 (R28) minimum
7.5 mrn (5/16 in) plywood - 38 X89rnrn (2 X 4 i t 1 1 4
1 1 ~
400 mrn (16 in)O.C.
RSI 2.1 (~12)* RSI 3.5 IR20)- 1/2 in rigid fibreglass- drainage layertoe nail to concrete floor
FIGURE 3
WALL SECTION - CONCRETE WALL