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Performance of passive ventilation systems in a two-storey house
Shaw, C. Y.; Kim, A. K.
https://publications-cnrc.canada.ca/fra/droits
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https://nrc-publications.canada.ca/eng/view/object/?id=d8b2c837-ee0e-46e7-b8a1-bc239a94a83c https://publications-cnrc.canada.ca/fra/voir/objet/?id=d8b2c837-ee0e-46e7-b8a1-bc239a94a83c
TH1
National Research Conseil national
N21d
1
si
Council Canada
de recherches Canada
no.
1276
@. 2= I
PERFORMANCE OF PASSIVE VENTILATION SYSTEMS IN A TWO-STOREY HOUSE
by C.Y. Shaw and A. Kim
ANALYZED
Presented a t
The Implementation and Effectiveness of Air Infiltration Standards in Buildings
5th AIC Conference, October 1
-
4 1984, Reno, Nevada, USAPaper 11, p. 11.1
-
11.27Reprinted with permission
DBR Paper No. 1276
Division of Building Research
R ~ S U M ~
Les d6bits de renouvellement de l'air ont 6t6 mesur6s dans une rnaison individuelle de deux dtages munie de cinq types
fondamentaux drinstallations de ventilation passive : prise
d'air dans la paroi du sous-sol; prise d'air ext6rieur raccord6e A l'installation de chauffage 3 air puls6; chemin6e
d16vacuation allant du sous-sol au toit; deux installations cornbinant prise dlair et chemin6e. Un parametre a dtd d6fini pour &valuer le taux de renouvellement de l'air dans la maison
% partir de 11Qtanchdit6 3 l'air de la maison, du niveau de
pression nulle et de lv6cart entre la temp6ratur-e de l'air
2
lVint6rieur et celle
3
l1ext6rieur. On a obtenu pour la maison d'essai un bon accord entre les taux pr6vus et ceuxeffectivement mesur6s. Les effets du ventilateur du
g&n&rateur, du systhme de distribution de l'air et des dimensions et de l'emplacement des bouches de -ventilation sur les taux de renouvellement de l'air sont 6galement abord6s.
THE IMPLEMENTATION AND EFFECTIVENESS OF AIR INFILTRATION
STANDARDS I N BUILDINGS
5th
A I C Conference, October 1-4 1984, Reno, Nevada, USA
PAPER 11
PERFORMANCE OF PASSIVE VENTILATION SYSTEMS IN A TWO-STOREY HOUSE
C . Y . SHAW and A. K I M
Division of Building Research, National Research Council of Canada, Ottawa, Canada, K I A 0R6.
ABSTRACT
A i r change r a t e s were measured i n one two-storey d e t a c h e d house w i t h f i v e b a s i c t y p e s of p a s s i v e v e n t i l a t i o n systems: an i n t a k e v e n t i n t h e basement w a l l ; an o u t d o o r a i r s u p p l y d u c t e d t o t h e e x i s t i n g f o r c e d a i r h e a t i n g system; a n e x h a u s t s t a c k e x t e n d i n g from t h e basement t o t h e r o o f ; and two c o m b i n a t i o n s of t h e s u p p l y systems and t h e e x h a u s t s t a c k . An e x p r e s s i o n was d e v e l o p e d f o r e s t i m a t i n g house a i r change r a t e from h o u s e a i r t i g h t n e s s , n e u t r a l p r e s s u r e l e v e l and indoor-outdoor a i r t e m p e r a t u r e d i f f e r e n c e . Good agreement was o b t a i n e d f o r t h e t e s t h o u s e between t h e p r e d i c t e d and t h e measured a i r change r a t e s . The e f f e c t s o f f u r n a c e f a n o p e r a t i o n , a i r d i s t r i b u t i o n s y s t e m , and s i z e and l o c a t i o n of v e n t o p e n i n g s on h o u s e a i r change r a t e s a r e a l s o d i s c u s s e d .
1. INTRODUCTION
The a i r l e a k a g e c h a r a c t e r i s t i c of a house h a s a major e f f e c t on energy consumption, i n d o o r a i r q u a l i t y a n d m o i s t u r e problems. To i n v e s t i g a t e t h e e f f e c t of w e a t h e r , a i r t i g h t n e s s , and h e a t i n g and v e n t i l a t i o n s y s t e m s on t h e a i r change and a i r p r e s s u r e
d i s t r i b u t i o n of a h o u s e , s e v e r a l s t u d i e s were u n d e r t a k e n on f o u r d e t a c h e d two-storey houses. These s t u d i e s were p a r t of t h e Mark
X I Energy Research P r o j e c t co-sponsored by t h e D i v i s i o n of B u i l d i n g R e s e a r c h a n d t h e Housing a n d Urban Development
A s s o c i a t i o n of Canada (HUDAC). The a i r change r a t e s and t h e a i r t i g h t n e s s v a l u e s measured f o r t h e f o u r h o u s e s , a n d a d i s c u s s i o n on t h e r e l a t i o n s h i p between house
a i r
change r a t e anda i r t i g h t n e s s , wind a n d s t a c k a c t i o n , a n d t h e o p e r a t i o n o f a n a t u r a l - d r a f t g a s f u r n a c e , h a v e a l r e a d y been r e p o r t e d . 2s 3,
The r e s u l t s of a s t u d y on mechanical v e n t i l a t i o n s y s t e m s have a l s o been r e p o r t e d . T h i s p a p e r p r e s e n t s t h e r e s u l t s of a s t u d y on p a s s i v e v e n t i l a t i o n systems.
I n t e r e s t i n p a s s i v e v e n t i l a t i o n t e c h n i q u e s h a s been i n c r e a s i n g a s more a i r t i g h t h o u s e s a r e c o n s t r u c t e d and more m o i s t u r e problem a r e r e p o r t e d . P a s s i v e v e n t i l a t i o n u s u a l l y t a k e s . t h e form of a n a i r i n l e t i n t h e e x t e r i o r w a l l o r a n e x h a u s t s t a c k , o r a c o m b i n a t i o n of t h e two. S i n c e t h e amount of o u t d o o r a i r s u p p l i e d by t h e s e means v a r i e s w i t h o u t d o o r w e a t h e r c o n d i t i o n s , p a s s i v e v e n t i l a t i o n h a s n e v e r been c o n s i d e r e d a s a s a t i s f a c t o r y means of p r o v i d i n g v e n t i l a t i o n a i r i n t i g h t houses. However, f o r h o u s e s i n which a i r
l e a k a g e p r o v i d e s most of t h e v e n t i l a t i o n , a w e l l - d e s i g n e d p a s s i v e v e n t i l a t i o n s y s t e m c a n b e a p r a c t i c a l means of s u p p l y i n g t h e a d d i t i o n a l o u t d o o r a i r r e q u i r e d f o r c o n t r o l l i n g i n d o o r h u m i d i t y and improving i n d o o r a i r q u a l i t y .
The main o b j e c t i v e of t h i s s t u d y was t o check e x p r e s s i o n s developed f o r p r e d i c t i n g t h e
a i r
change r a t e of h o u s e s w i t h p a s s i v e v e n t i l a t i o n systems.2. EFFECT OF VENT OPENINGS ON HOUSE A I R CHANGE AND PRESSURE
I n a p r e v i o u s s t u d y , t h e a i r change r a t e s of one of t h e f o u r h o u s e s (H3) were measured t o d e t e r m i n e t h e e f f e c t of v e n t i n g t h r o u g h a chimney on t h e house a i r l e a k a g e c h a r a c t e r i s t i c . The r e s u l t s a r e summarized i n Fig. 1.
F i g u r e l a shows t h e temperature-induced a i r f l o w and p r e s s u r e d i f f e r e n c e p a t t e r n s f o r t h i s h o u s e w i t h t h e chimney capped. Because t h e a i r i n s i d e t h e house i s w a r m e r , and h e n c e l e s s d e n s e t h a n t h a t o u t s i d e , i t t e n d s t o r i s e and l e a k o u t t h r o u g h t h e u p p e r p a r t s of t h e house; c o l d e r o u t d o o r a i r l e a k s i n t h r o u g h t h e lower p a r t s of t h e h o u s e t o r e p l a c e i t . The p r e s s u r e d i f f e r e n c e a c r o s s t h e e x t e r i o r w a l l d e c r e a s e s l i n e a r l y from a p o s i t i v e v a l u e a t t h e g r a d e l e v e l t o a n e g a t i v e v a l u e a t t h e c e i l i n g l e v e l . Near mid-height, t h e r e i s a l e v e l where t h e p r e s s u r e d i f f e r e n c e i s z e r o . T h i s i s c a l l e d t h e n e u t r a l p r e s s u r e l e v e l . m e n a v e n t , s u c h a s a chimney o r a n e x h a u s t s t a c k , i s i n s t a l l e d i n t h e h o u s e , t h e a i r change r a t e i n c r e a s e s d u e t o t h e a i r £ 1 ~ t h r o u g h t h e v e n t ( F i g . l b ) . The a i r f l o w t h r o u g h t h e v e n t d e p e n d s upon t h e t e m p e r a t u r e d i f f e r e n c e between i n s i d e a n d o u t s i d e , a n d t h e s i z e and l o c a t i o n of t h e v e n t . A s a r e s u l t , t h e p r e s s u r e d i f f e r e n c e a c r o s s t h e e x t e r i o r w a l l i s r e d i s t r i b u t e d s o t h a t a mass f l o w b a l a n c e i s m a i n t a i n e d .
The a i r change r a t e caused by s t a c k a c t i o n a l o n e depends on t h e a i r t i g h t n e s s of t h e e n v e l o p e a n d t h e i n d o o r - t o - o u t d o o r a i r
t e m p e r a t u r e d i f f e r e n c e . F i g u r e l c shows t h e a i r change r a t e s f o r t h e h o u s e w i t h and w i t h o u t a chimney. Without a chimney, t h e measured a i r change r a t e s f o r wind s p e e d s l o w e r t h a n 12 kmlh a g r e e d c l o s e l y w i t h t h e v a l u e s p r e d i c t e d by Eq. 1 ( d e r i v e d p r e v i o u s l y f o r t h e o t h e r two c h i m n e y l e s s h o u s e s , H1 and H 4 , i n c l u d e d i n t h e Mark X I p r o j e c t ) . where : I = house a i r change r a t e , a c l h , A = a r e a of b u i l d i n g e n v e l o p e ( a r e a of e x t e r i o r w a l l above g r a d e and c e i l i n g a r e a of t o p f l o o r ) m2, V = volume of b u i l d i n g i n c l u d i n g basement, m 3 , C = f l o w c o e f f i c i e n t , L / ( s * m 2 * ~ a n ) , n = f l o w e x p o n e n t , A t = indoor-to-outdoor t e m p e r a t u r e d i f f e r e n c e , K , 0.32 = d i m e n s i o n a l c o n s t a n t , m 0s *pan/ ( L * ~ " * h ) .
With a chimney, t h e measured a i r change r a t e s c o u l d b e e x p r e s s e d by an e q u a t i o n s i m i l a r t o Eq. 1:
r
= B(A/v) c , ( A ~ ) ~ v ( 2 where: Cv = f l o w c o e f f i c i e n t w i t h v e n t , ~ / ( s . m ~ . ~ a " ) , n v = f l o w e x p o n e n t w i t h v e n t , n n B = 0.43, a d i m e n s i o n a l c o n s t a n t , m3.s .Pa '/(L*K V * h ) .A s t h e r a t i o of t h e c o n s t a n t s i n Eqs. 1 and 2 was a p p r o x i m a t e l y e q u a l t o t h e r a t i o of t h e two n e u t r a l p r e s s u r e l e v e l s , a g e n e r a l e x p r e s s i o n f o r t h e two e q u a t i o n s was: v I I = 0.32 (A/V) r Cv(At) ( 3
1
and r = l + l ( h v - h ) l / h i where : Cv = f l o w c o e f f i c i e n t w i t h v e n t , L / ( s *m2.Panv), nv = f l o w e x p o n e n t w i t h v e n t ,i
hv = n e u t r a l p r e s s u r e l e v e l w i t h v e n t , m, h = n e u t r a l p r e s s u r e l e v e l w i t h o u t v e n t , m. I f b o t h an i n t a k e v e n t and an e x h a u s t v e n t are i n s t a l l e d , t h e changes i n n e u t r a l p r e s s u r e l e v e l c a u s e d by t h e v e n t s t e n d t o c a n c e l e a c h o t h e r . When t h e r e a r e m u l t i p l e v e n t s , t h e e x p r e s s i o n f o rr
is:J
r = l+
c l ( h v , j-
h) l / hwhere J i s t h e number of v e n t s and h v
.
i s t h e n e u t r a l p r e s s u r e l e v e l c o r r e s p o n d i n g t o t h e j t h v e n tit
i t were t h e o n l y one. Equation 3 r e q u i r e s v a l u e s of t h e f l o w c o e f f i c i e n t (C) a n d exponent ( n ) and t h e n e u t r a l p r e s s u r e l e v e l o f t h e h o u s e w i t h v e n t i l a t i o n system. These v a l u e s c a n be measured d i r e c t l y o r e s t i m a t e d u s i n g t h e methods d e s c r i b e d i n Appendix A.Although Eq. 3 was d e r i v e d f o r s t a c k a c t i o n a l o n e , i t a p p l i e s e q u a l l y w e l l where t h e r e i s t h e combined e f f e c t o f s t a c k a c t i o n and wind ( F i g . I d ) . The a i r change r a t e s were measured i n a t e s t house and compared w i t h t h e v a l u e s p r e d i c t e d by Eq. 3 t o check t h e v a l i d i t y of t h i s e q u a t i o n .
3. TEST HOUSE AND PASSIVE VENTILATION SYSTEMS
3.1 T e s t House
The t e s t house (H4) is a two-storey d e t a c h e d h o u s e w i t h a f u l l basement, l o c a t e d i n a d e v e l o p e d r e s i d e n t i a l a r e a i n t h e c i t y o f G l o u c e s t e r , O n t a r i o . The house h a s a f o r c e d - a i r h e a t i n g s y s t e m w i t h a n e l e c t r i c f u r n a c e . It a l s o h a s a 12.7 c m d i a m e t e r chimney, which was capped when t h e e l e c t r i c f u r n a c e was i n u s e . The volume of t h e h o u s e , i n c l u d i n g basement, i s 386 m 3 and t h e a r e a o f t h e house e n v e l o p e , i n c l u d i n g t h e a r e a of t h e s e c o n d f l o o r c e i l i n g i s
227.7 m2. The s e c o n d - s t o r e y c e i l i n g i s 5.4 m above g r a d e l e v e l .
3.2 Vent Openings
Each of t h e two basement windows i n t h e s o u t h w a l l was r e p l a c e d by a plywood p a n e l w i t h a 10
c m
d i a m e t e r p i p e i n s t a l l e d a t t h e c e n t r e(Fig. 2). One of t h e p i p e s c o u l d b e c o n n e c t e d t o t h e r e t u r n a i r d u c t of t h e h e a t i n g system. The e x i s t i n g 12.7 c m d i a m e t e r chimney was u s e d t o s i m u l a t e an e x h a u s t s t a c k . P r o v i s i o n was made f o r
i n d o o r a i r t o e x h a u s t t h r o u g h t h e s t a c k f r o m e i t h e r t h e basement o r t h e second s t o r e y .
VENT STACK
INLET VENT. N. VENT'
E' 12.7 en 12.7 cm 12" cm DIA. DIA. DIA. g;7Tx: VENT, 5, rn E C
-.-
f :-;- FIRST-STOREY VENT. N. 12.7 cm DIA. BASEMENT INLET. BASEMENT VENT, 5, 10 sm DIA. {BASEMENT VENT. S. 10 cm DIA. S O U T H E L E V A 7 1 0 N F i g u r e 2. T e s t house w i t h l o c a t i o n of v e n t o p e n i n g sPlywood p a n e l s w i t h a 12.7 cm d i a m e t e r c i r c u l a r opening were i n s t a l l e d i n t h e opening of one s o u t h window and one n o r t h window on t h e f i r s t s t o r e y , and one n o r t h window and one e a s t window on
t h e second s t o r e y . These openings could be c l o s e d by merely
c l o s i n g t h e casement windows.
The v e n t openings and e x h a u s t s t a c k were combined t o s i m u l a t e t h e f i v e b a s i c p a s s i v e v e n t i l a t i o n c o n f i g u r a t i o n s shown i n Fig. 3a, and t h e s i x a d d i t i o n a l c o n f i g u r a t i o n s shown i n Fig. 3b. The f i v e b a s i c con£ ig u r a t i o n s were:
( I ) 10-cm diameter opening i n s o u t h basement w a l l d e l i v e r i n g a i r t o t h e basement a t g r a d e l e v e l ;
(11) 10-m d i a m e t e r p i p e s u p p l y i n g outdoor a i r t o t h e r e t u r n d u c t of t h e f o r c e d - a i r h e a t i n g system; i n t a k e opening a t g r a d e l e v e l ;
(111) 12.7-cm d i a m e t e r e x h a u s t s t a c k e x t e n d i n g from basement t o above t h e r o o f ;
(IV)
combination of I and 111;(V)
combination of I1 and 111.S i x more c o n f i g u r a t i o n s were t e s t e d t o demonstrate t h e v e n t i l a t i o n c a p a b i l i t y of t h e d i f f e r e n t p a s s i v e v e n t i l a t i o n t e c h n i q u e s i n houses w i t h and w i t h o u t an a i r d i s t r i b u t i o n system. They were a l s o i n t e n d e d t o show how w e l l t h e v e n t i l a t i o n a i r ( o u t d o o r a i r ) mixed w i t h indoor a i r , and how t h e l o c a t i o n of t h e v e n t openings
TESTS WERE REPEATED WITH THE FURNACE F A N SHUT D O W N , THESE TESTS WERE INDICATED BY A SUBSCRIPT "A"
t ( 0 ) F I V E B A S I C C O N F I G U R A T I O N S
( b ) A D D I T I O N A L C O N F I G U R A T I O N S
a f f e c t e d t h e v e n t i l a t i o n r a t e . The s i x a d d i t i o n a l c o n f i g u r a t i o n s were :
(VI) 12.7-cm d i a m e t e r e x h a u s t s t a c k e x t e n d i n g from second s t o r e y t o above t h e r o o f ; ( V I I ) two 10-cm d i a m e t e r o p e n i n g s a b o u t 5.3
m
a p a r t i n t h e basement w a l l , a t g r a d e l e v e l ; ( V I I I ) 12.7-cm d i a m e t e r o p e n i n g i n f i r s t s t o r e y n o r t h window, 1.2 m above g r a d e ; (IX) 12.7-cm d i a m e t e r o p e n i n g i n s e c o n d s t o r e y n o r t h window, 5 m above g r a d e ;(X)
12.7-cm d i a m e t e r o p e n i n g i n f i r s t s t o r e y s o u t h window, 1.8 m above g r a d e ;(XI) 12.7-cm d i a m e t e r o p e n i n g i n second s t o r e y e a s t window, 5 m above g r a d e .
A l l of t h e s e c o n f i g u r a t i o n s were t e s t e d w i t h t h e a i r c i r c u l s t i n g f a n of t h e f o r c e d - a i r h e a t i n g s y s t e m o p e r a t i n g c o n t i n u o u s l y . C o n f i g u r a t i o n s I1 t o V were a l s o t e s t e d w i t h t h e f a n o f f .
4.
TESTS
AND MEASUREMENTSFor e a c h weather c o n d i t i o n , t h e v a r i o u s c o n f i g u r a t i o n s were t e s t e d , o n e a f t e r a n o t h e r and t h e f o l l o w i n g p a r a m e t e r s were measured:
( 1 ) i n d o o r and o u t d o o r a i r t e m p e r a t u r e s , measured and r e c o r d e d o n a c o m p u t e r b a s e d d a t a l o g g i n g system;
( 2 ) l o c a l wind s p e e d and d i r e c t i o n , measured 10 m s o u t h of t h e h o u s e and 1 8 m above g r a d e , and r e c o r d e d o n t h e same d a t a l o g g i n g system;
( 3 ) a i r change r a t e ( s ) , (whole h o u s e , o r l i v i n g s p a c e a n d basement s e p a r a t e l y ) ; and
( 4 ) a i r f l o w r a t e s t h r o u g h v e n t o p e n i n g s a n d e x h a u s t s t a c k .
A i r p r e s s u r e d i f f e r e n c e s a c r o s s t h e h o u s e e n v e l o p e were o n l y measured u n d e r calm c o n d i t i o n s (wind s p e e d less t h a n 8 km/h) and o n l y f o r some c o n f i g u r a t i o n s (no v e n t s , and c o n f i g u r a t i o n s I t o V
and IX)
.
Fan p r e s s u r i z a t i o n t e s t s t o d e t e r m i n e t h e a i r t i g h t n e s s of t h e house, w i t h and w i t h o u t v e n t o p e n i n g s , were performed o n c e i n e a r l y summer under calm c o n d i t i o n s and o n l y f o r s e l e c tc o n f i g u r a t i o n s (no v e n t s , and c o n f i g u r a t i o n s I , 11, lIa, 111, I V , V , V I I , I X and
X).
4.1 A i r Change R a t e
A i r change r a t e was measured u s i n g t h e t r a c e r g a s d e c a y method w i t h N20 ( n i t r o u s o x i d e ) as t h e t r a c e r g a s . 6 The d o o r t o t h e
basement was k e p t c l o s e d d u r i n g t h e measurement. For e a c h measurement, t h e t r a c e r g a s was i n j e c t e d i n t o , and a i r s a m p l e s were c o l l e c t e d from, t h e f o r c e d a i r h e a t i n g s y s t e m w i t h s e p a r a t e i n j e c t i o n and sampling t u b e s . The f u r n a c e f a n w a s o p e r a t e d c o n t i n u o u s l y t o mix t h e t r a c e r g a s w i t h t h e i n d o o r a i r .
For t h o s e s p e c i a l t e s t s w i t h t h e f u r n a c e f a n o f f , t h e f a n was o n l y s h u t down a f t e r t h e t r a c e r g a s was t h o r o u g h l y mixed ( a b o u t 3 0 min. a f t e r an i n j e c t i o n ) . During t h e t r a c e r g a s sampling p e r i o d ,
mixing was h a n d l e d by s e v e r a l p o r t a b l e f a n s l o c a t e d t h r o u g h o u t t h e house. For t h e s e t e s t s w i t h f u r n a c e f a n o f f , a i r samples were
t a k e n d i r e c t l y from t h e basement a n d from t h e main l i v i n g a r e a . The N20 c o n c e n t r a t i o n s were measured on s i t e w i t h a n i n f r a r e d a n a l y z e r . The a n a l y z e r was c a l i b r a t e d p e r i o d i c a l l y u s i n g c e r t i f i e d c a l i b r a t i o n g a s .
4.2
A i r Flow R a t eI
The a i r f l o w t h r o u g h t h e v e n t opening and t h e s t a c k w a s measured
u s i n g e i t h e r a p a i r of t o t a l p r e s s u r e a v e r a g i n g t u b e s o r a n I o r i f i c e p l a t e , w i t h a diaphragm-type p r e s s u r e t r a n s d u c e r ( s t a t i c e r r o r band of
5%
f u l l s c a l e ) . 4.3 V e r t i c a l P r e s s u r e D i f f e r e n c e P r o f i l eI
I Values of indoor-outdoor p r e s s u r e d i f f e r e n c e a c r o s s t h e h o u s e e n v e l o p e w e r e measured u n d e r calm c o n d i t i o n s a t f o u r l o c a t i o n s a l o n g t h e n o r t h w a l l w i t h a diaphragm-type p r e s s u r e t r a n s d u c e r ( s t a t i c e r r o r band of 5% f u l l s c a l e ) . P r e s s u r e p r o b e s werei n s t a l l e d a t t h e s i l l and head of a f i r s t f l o o r window, and a t t h e
s i l l and head l e v e l of a second f l o o r window d i r e c t l y above t h e
f i r s t . The p r o b e s were l o c a t e d 1.1, 2.6, 3.9 and 5.2 rn above 1 g r a d e , r e s p e c t i v e l y .
5. RESULTS AND DISCUSSION
I
I
1
11.8
The r e s u l t s of t h e f a n p r e s s u r i z a t i o n t e s t s conducted i n e a r l y summer, w i t h t i g h t n e s s e x p r e s s e d i n terms of C and n , a r e g i v e n i n Table 1. Also g i v e n i n Table 1 a r e t h e h e i g h t of n e u t r a l p r e s s u r e l e v e l s a n d t h e p r e s s u r e d i f f e r e n c e s a t g r a d e l e v e l measured u n d e r calm c o n d i t i o n s w i t h a n i n d o o r - t o - o u t d o o r t e m p e r a t u r e d i f f e r e n c e of 34 K.
The a i r change r a t e s of t h e h o u s e and t h e a i r f l o w r a t e s t h r o u g h t h e v e n t s were measured d u r i n g t h e 1982-83 h e a t i n g s e a s o n under a v a r i e t y of w e a t h e r c o n d i t i o n s ; a i r t e m p e r a t u r e d i f f e r e n c e r a n g e d
from 10 t o 40 K , and wind speed v a r i e d up t o 30 km/h. The r e s u l t s
f o r t h e f i v e b a s i c c o n f i g u r a t i o n s a r e shown i n F i g s . 5 t o 9, a n d are d i s c u s s e d i n t h e f o l l o w i n g s e c t i o n s .
To d e t e r m i n e t h e e f f e c t i v e n e s s of t h e s e v e n t i l a t i o n t e c h n i q u e s , t h e measured a i r change r a t e s were compared w i t h t h o s e measured f o r t h e house w i t h o u t p a s s i v e v e n t i l a t i o n (measured i n a p r e v i o u s
s t u d y 3 ) . For a wind s p e e d lower t h a n 12 kmlh, t h e a i r change r a t e
i n c r e a s e d w i t h i n s i d e - o u t s i d e t e m p e r a t u r e d i f f e r e n c e a s d e f i n e d by Eq. 1 (Fig. 4 ) . For h i g h e r wind s p e e d s , t h e a i r change r a t e
exceeded t h e v a l u e s t h a t would a p p l y f o r t h e same A t w i t h low wind speed. However, f o r t e m p e r a t u r e d i f f e r e n c e s g r e a t e r t h a n 20 K and wind speed r a n g i n g from 12 t o 40 km/h, t y p i c a l w i n t e r c o n d i t i o n s
f o r t h i s r e g i o n o f Canada, t h e a i r change r a t e was a p p r o x i m a t e l y c o n s t a n t a t 0.2 a c / h . Thus, 0.2 a c / h was chosen as t h e s e a s o n a l a v e r a g e a i r change r a t e f o r t h e t e s t h o u s e w i t h o u t p a s s i v e v e n t i l a t i o n . Z 0.30 r
-
( b ) a O SEASONAL U .r 0 . 2 0-
- 4.
/-
/<€a. 1 I 0.10-
- I , 0 . 0 8 - 1 2 c w S 2 O km/h-
L 0 2 0 c W < 4 0 km/h 0 . 0 5 I I I I I 1 1 I 1 1 1 8 10 2 0 3 0 4 0 50 4 1 , T E M P E R A T U R E D I F F E R E N C E . K F i g u r e 4. A i r change r a t e w i t h o u t p a s s i v e v e n t i l a t i o n ( R e f e r e n c e 3) 5.1 The F i v e B a s i c C o n f i g u r a t i o n s F i g u r e s 5 t o 9 i n d i c a t e t h a t t h e h o u s e a i r change r a t e i n c r e a s e d w i t h t h e i n d o o r t o - o u t d o o r a i r t e m p e r a t u r e d i f f e r e n c e b u t was r e l a t i v e l y i n s e n s i t i v e t o wind f o r a l l systems. However, a t a c o n s t a n t A t , t h e i n f l u e n c e o f wind o n h o u s e a i r change c o u l d b e0 . 5 WWEZ
.
W s l o km/h 0 l O ~ W S ~ k m / h a w =-XI km/h 0 . 2 Kh5ONAL A W G E W T H W T VENT 0 . 1 12
4 6 a 1 0 20 3 0 40 6 0 0 a t . TEMPERATURE DIFFERENCE, K 35
0 . 6 MEAWRED VAWES -;
0 . 5 m A ~ C M x 2 0 . 4 o m c a ~ s m K a n t c m K a n t . TEMPERATURE DIFFERENCE, K W, WlND SPEED. km/hFigure 5 . House a i r change r a t e and a i r f l o w r a t e through intake
vent
-
configuration I .c 1-1 3 VENI J 0 . 1 I I l l L I I I k l 1 1 12
8 10 20 30 4 0 50-
z
A t . TEMPERATURE DIFFERENCE. K 3 I u 0 . 5 .- e-
- * 0.4-
d-
-
01 0 . 3-
b 4 s 0. 0.
c 0 0 U . ?-
MEASURED VALVES r b 7 5 20 K-
0 2 0 < b r s 3 0 K a K t b I 0 1 1 1 1 1 I I 1 1 1 1 1 1 5 8 10 20 3 0 40 50 W, WlND SPEED, km/h-
3 0 AMRAGE e C 0 A t , TEMPERATURE DIFFERENCE, KFigure 6 . House a i r change r a t e and a i r f l o w r a t e through intake
d e t e c t e d ( 5 a t o 9 a ) . Likewise, f o r a c o n s t a n t wind s p e e d , t h e s c a t t e r i n t h e a i r change d a t a w a s mainly c a u s e d by s t a c k a c t i o n ( 5 b t o 9 b ) .
The measured a i r change r a t e s f o r t h e f i v e c o n f i g u r a t i o n s a r e compared w i t h t h o s e p r e d i c t e d by Eq. 3 i n F i g s . 5a t o 9a. In
g e n e r a l , t h e c a l c u l a t e d a i r change r a t e s were w i t h i n 20% of t h e measured v a l u e s .
A comparison between Eqs. 2 and 3 i n d i c a t e s t h a t t h e r a t i o Bl0.32 s h o u l d b e e q u a l t o
r ,
i f t h e v a l u e s o f n a r e a b o u t t h e same. S i n c e t h e v a l u e of B can be e s t i m a t e d i n d e p e n d e n t l y by f i t t i n g t h e measured a i r change r a t e s t o Eq. 2, a n o t h e r check on t h e a c c u r a c y of Eq. 3 was made by comparing t h e r a t i o Bl0.32w i t h
r.
The r e s u l t s , l i s t e d i n T a b l e 1 , i n d i c a t e t h a t t h e maxinum d i f f e r e n c e between ~ 1 0 . 3 2 andr
i s a b o u t 10% ofr
f o r t h e f i v e c o n f i g u r a t i o n s . 5.1.1 C o n f i g u r a t i o n I--
One basement i n t a k e v e n t T h i s c o n f i g u r a t i o n i s s i m i l a r t o a h o u s e w i t h a preponderance o f l e a k a g e o p e n i n g s i n t h e l o w e r h a l f of t h e h o u s e e n v e l o p e , s u c h a s a window v e n t . The v e n t i l a t i o n s y s t e m became e f f e c t i v e ( i . e . , a i r change r a t e exceeded t h a t of t h e h o u s e w i t h n o v e n t , 0.2 a c l h ) when t h e t e m p e r a t u r e d i f f e r e n c e was g r e a t e r t h a n 20 K , a s showni n
Fig. 5a. T h i s f i g u r e a l s o shows t h a t Eq. 3 o v e r p r e d i c t s t h e a i r change r a t e by a b o u t 6% i n comparison w i t h t h e b e s t f i t t o t h e measured d a t a .
F i g u r e 5 c shows t h a t t h e a i r f l o w t h r o u g h t h e v e n t opening a l s o i n c r e a s e d w i t h t e m p e r a t u r e d i f f e r e n c e . The a i r f l o w r a t e t h r o u g h t h e v e n t was a l s o i n f l u e n c e d by b o t h wind s p e e d and d i r e c t i o n .
5.1.2 C o n f i g u r a t i o n I1
--
Basement s u p p l y t o f o r c e d - a i r h e a t i n g s y s t e mT h i s c o n f i g u r a t i o n i s s i m i l a r t o c o n f i g u r a t i o n I , e x c e p t t h a t t h e v e n t i n g a c t i o n i s now augmented by t h e o p e r a t i o n o f t h e f u r n a c e f a n . The house a i r change r a t e exceeded t h a t of t h e h o u s e w i t h n o v e n t (0.2 a c l h ) f o r a t e m p e r a t u r e d i f f e r e n c e a s small a s 10 K ( F i g . 6 a ) . T h i s s u g g e s t s t h a t t h e f u r n a c e f a n i s e f f e c t i v e i n i n c r e a s i n g t h e s u p p l y of o u t d o o r a i r t o t h e house. T h i s s u g g e s t i o n i s r e i n f o r c e d s i n c e t h e a i r f l o w t h r o u g h t h e s u p p l y v e n t remained n e a r l y c o n s t a n t a t a v a l u e o f a b o u t 1 8 L / s o r 0.17 a c / h r e g a r d l e s s of t e m p e r a t u r e d i f f e r e n c e ( ~ i g . 6 c ) ; t h a t i s , t h e s u p p l y of o u t d o o r a i r was c o n t r o l l e d by t h e f u r n a c e f a n r a t h e r t h a n by s t a c k a c t i o n . A s t h e o u t d o o r s u p p l y a i r r a t e w a s c o n s t a n t , t h e h o u s e a i r change r a t e s h o u l d a l w a y s e x c e e d 0.17 a c l h . The t e m p e r a t u r e d i f f e r e n c e c o r r e s p o n d i n g t o 0.17 a c l h
i s 12.5 K (Fig. 6 a ) , s u g g e s t i n g t h a t Eq. 3 s h o u l d b e u s e d o n l y when A t i s g r e a t e r t h a n 12.5
K.
F i g u r e 6 a a l s o i n d i c a t e s t h a t Eq. 3 u n d e r p r e d i c t s t h e a i r change r a t e by a b o u t 10% i n comparison w i t h t h e b e s t f i t t o t h e measured v a l u e s .5.1.3 C o n f i g u r a t i o n I11
--
Basement e x h a u s t s t a c kT h i s c o n f i g u r a t i o n i s s i m i l a r t o a house w i t h a preponderance o f l e a k a g e o p e n i n g s i n t h e u p p e r h a l f of t h e h o u s e envelope. As Fig. 7a i n d i c a t e s , t h e house a i r change r a t e w a s g r e a t e r t h a n 0.2 a c / h when t h e t e m p e r a t u r e d i f f e r e n c e was g r e a t e r t h a n 20 K. Compared w i t h t h e p r e v i o u s two s y s t e m s , t h i s s y s t e m i s more e f f e c t i v e t h a n c o n f i g u r a t i o n I ( p r o b a b l y d u e t o a l a r g e r s i z e v e n t ) b u t i s less e f f e c t i v e t h a n c o n f i g u r a t i o n 11, e s p e c i a l l y under m i l d w e a t h e r c o n d i t i o n s . F i g u r e 7 a a l s o i n d i c a t e s t h a t Eq. 3 c o i n c i d e s w i t h t h e b e s t f i t t o t h e measured d a t a .
The a i r e x h a u s t r a t e t h r o u g h t h e s t a c k was more s t r o n g l y
i n f l u e n c e d by s t a c k a c t i o n t h a n i n t h e two p r e v i o u s c o n f i g u r a t i o n s ( F i g . 7 c ) . Under mild weather c o n d i t i o n s , t h e e x h a u s t r a t e s were a l s o i n f l u e n c e d by wind. The wind i n f l u e n c e , however, d i m i n i s h e d a s t h e t e m p e r a t u r e d i f f e r e n c e i n c r e a s e d .
5.1.4 C o n f i g u r a t i o n I V
--
Combination of I and 111This c o n f i g u r a t i o n can be found i n h o u s e s w i t h a f o r c e d - a i r h e a t i n g s y s t e m when t h e o u t d o o r a i r s u p p l y i s d i s c o n n e c t e d from t h e h e a t i n g d u c t . A s shown i n Fig. 8 a , t h i s s y s t e m s u p p l i e d more v e n t i l a t i o n a i r t o t h e h o u s e t h a n any of t h e f o r e g o i n g s y s t e m s , and Eq. 3 o v e r p r e d i c t s t h e a i r change r a t e by a b o u t 7% i n comparison w i t h t h e b e s t f i t t o t h e measured d a t a .
Data p r e s e n t e d i n Fig. 8 c show t h a t t h e a i r s u p p l y and e x h a u s t f l o w s t h r o u g h t h e i n t a k e v e n t and t h e e x h a u s t s t a c k were
i n f l u e n c e d s t r o n g l y by s t a c k a c t i o n . Also t h e a i r f l o w t h r o u g h t h e e x h a u s t s t a c k was a l m o s t i d e n t i c a l t o t h a t o f c o n f i g u r a t i o n 111, and t h e a i r f l o w t h r o u g h t h e i n t a k e v e n t was a b o u t t h e same
a s t h a t of c o n £ i s r a t i o n I. T h i s s u g g e s t s t h a t t h e h o u s e p r e s s u r e , and hence t h e a i r f l o w s t h r o u g h t h e i n t a k e v e n t a n d e x h a u s t s t a c k , were u n a f f e c t e d by t h e p r e s e n c e of t h e o t h e r v e n t .
-
- MEASURED VALUES 0 . 4-
m W 6 1 0 hm/h o I 0 < W 6 ?O kmjh 0 . 3-
o W = 2 O k m / h/G"
'
0 . 2 + SEASONAL AVERAGE/
- WITtrOUT MNT 4.15
; 0 . 1 I 1 I 1 1 I I 1 1 1 1 1 1 1 14
8 10 2 0 3 0 4 0 5 0 6 0 Y n t , TEMPERATURE DIFFERENCE, K 5 MEASURED VALUES 0 . 5 7 nt 5 2 0 K 0 . 4-
o 2 0 c A 1 5 3 0 K el-
0 & t > 3 0 K 0 . 3-
0-
0 0 o 8 . 0 . 2-
- .
' ( b ) (1.1 1 1 ( 1 1 1 I I 111k1d 8 10 20 3 0 4 0 5 0 6 0 W, WlND SPEED, km/h hl, IEMFfRATURE DIFFERENCE, KFigure 7 . House a i r change r a t e and a i r flow r a t e through exhaust
vent
-
configuration I11AVERAGE
.
W 5 10 km/hh 0 10 2 0 3 0 4 0 5 0 6 0
u
0
z Ot, TEMPERATURE DIFFERENCE. K
L .
0 0.2 MEASURED V4LUES W, WlND SPEED, km/h a'F
EXHAUST STACK 0 E7 0 0 0 o O * o n O INTAKE VENT.
IP I C l a 1 10 2 0 3 0 4 0 5 0 n t , TEMPERAIURE DIFFERENCE, KFigure 8 . House a i r change r a t e and a i r flow r a t e through vents
-
5.1.5 C o n f i g u r a t i o n V
--
Combination o f I1 a n d I11T h i s c o n f i g u r a t o n can be found i n h o u s e s w i t h a f o r c e d - a i r h e a t i n g s y s t e m h a v i n g a n o u t d o o r a i r s u p p l y c o n n e c t e d t o i t s r e t u r n d u c t . The t e m p e r a t u r e d i f f e r e n c e c o r r e s p o n d i n g t o 0.17 a c / h , t h e o u t d o o r a i r s u p p l y r a t e , i s 10 K (Fig. 9 a ) . A s t h i s w a s t h e minimum a i r
change r a t e f o r t h i s house, Eq. 3 i s a p p l i c a b l e f o r A t g r e a t e r t h a n 10 K. The a i r change rates p r e d i c t e d by Eq. 3 a r e a l m o s t i d e n t i c a l t o t h o s e g i v e n by t h e b e s t f i t t o t h e measured d a t a .
A s w a s t h e c a s e w i t h c o n f i g u r a t i o n I V , t h e a i r f l o w s t h r o u g h t h e i n t a k e v e n t a n d e x h a u s t s t a c k w e r e u n a f f e c t e d by t h e p r e s e n c e o f t h e o t h e r v e n t ( F i g . 912).
F i g u r e 10 shows t h e temperature-induced a i r f l o w and p r e s s u r e d i f f e r e n t i a l p a t t e r n s f o r t h e h o u s e w i t h a n d w i t h o u t a p a s s i v e v e n t i l a t i o n system. The a i r change r a t e s and t h e a i r f l o w r a t e
through t h e v e n t s were o b t a i n e d from F i g s . 4 t o 9 f o r A t = 34
K.
C o n f i g u r a t i o n V induced t h e h i g h e s t a i r change r a t e a t 0.42 a c / h , f o l l o w e d by c o n f i g u r a t i o n s I V , 11,- 111 a n d I a t 0.35, 0.33, 0.3 and 0.26 a c / h , r e s p e c t i v e l y . The a i r l e a k a g e r a t e t h r o u g h t h e h o u s e e n c l o s u r e f o r c o n f i g u r a t i o n V i s g r e a t e r t h a n t h a t f o r t h e house w i t h o u t v e n t s , even though t h e i r n e u t r a l p r e s s u r e l e v e l s a r e i d e n t i c a l . T h i s d i s c r e p a n c y may b e c a u s e d by e r r o r s a s s o c i a t e d w i t h n e u t r a l p r e s s u r e l e v e l measurement and a p o s s i b l e change i n t h e a i r l e a k a g e c h a r a c t e r i s t i c of t h e h o u s e e n c l o s u r e . The n e u t r a l p r e s s u r e l e v e l s of c o n f i g u r a t i o n s 111, I V , and V , a l l w i t h a n e x h a u s t s t a c k , were h i g h e r t h a n t h a t o f t h e h o u s e w i t h n o p a s s i v e v e n t i l a t i o n , a s Fig. 10 shows. F u r t h e r , t h e n e u t r a l p r e s s u r e l e v e l s o f c o n f i g u r a t i o n s I a n d 11, a l l w i t h o u t a n e x h a u s t s t a c k , were lower t h a n t h a t of t h e h o u s e w i t h o u t p a s s i v e v e n t i l a t i o n . Thus i t i s n o t d e s i r a b l e t o i n s t a l l a p a s s i v e v e n t i l a t i o n s y s t e m s i m i l a r t o c o n f i g u r a t i o n s I and 11 i n h o u s e s . Such a s y s t e m c a n l o w e r t h e n e u t r a l p r e s s u r e l e v e l o f t h e h o u s e , which i n t u r n , i n c r e a s e s t h e amount of humid a i r l e a k i n g o u t t h r o u g h t h e u p p e r w a l l s a n d c e i l i n g . Thus, i t i n c r e a s e s t h e p o t e n t i a l f o r d e v e l o p i n g m o i s t u r e problem.
6. EFFECT OF FURNACE FAN AND A I R DISTRIBUTION SYSTEM
C o n f i g u r a t i o n s 11, 111, I V , and V were r e t e s t e d w i t h t h e f u r n a c e f a n s h u t down t o d e t e r m i n e t h e e f f e c t of t h e f u r n a c e f a n a n d
a i r
d i s t r i b u t i o n s y s t e m on v e n t i l a t i o n e f f i c i e n c y and c a p a c i t y . I n t h i s s e r i e s of t e s t s , t r a c e r g a s c o n c e n t r a t i o n s were measured i n t h e basement and i n t h e f i r s t s t o r e y l i v i n g a r e a . The door t o t h e basement was k e p t c l o s e d , b u t t h e r e g i s t e r s a n d g r i l l e s of t h e a i r
MUSURFD VAWES O 5 W S ID l m / h 0 . 4
-
0 l O = W 5 m h / h 0 . 3 0 . 2 SEASONAL AWllnGC-
WITHOW { m l MNI 0 . 1 I 1 1 1 1 I I I I I r 1 1 1 4 5 8 10 2 0 3 0 4 0 9 0 n t , TEMPERATURE DIFFERENCE, KC
MEASURED VALUES 0 . 2.
a t s z o ~ 5 10 2 0 3 0 4 0 5 0 A t , TEMPERATURE DIFFERENCE, K W. WIND SPEED, km/hFigure 9. House air change rate and air flow rate through vents
-
con£ iguration
V
& I 9 L/s Y , BUILDING
Figure 10. Temperature-induced air flow and pressure patterns for At =
34 K
..
I 0 2 8 --
- 0 7:
0 2 5 - + 6 0 U "3 < 0 3 - = u, u 2 Ow z 2 T I M E , men F i g u r e 11. Sample p l o t s of N20 c o n c e n t r a t i o n v e r s u s t i m e f o r a i r samples c o l l e c t e d from r e t u r n a i r d u c t , basement a n d main l i v i n g a r e aF i g u r e 11 shows t h r e e sample p l o t s of N 2 0 c o n c e n t r a t i o n v e r s u s time; one f o r c o n f i g u r a t i o n V ( w i t h f u r n a c e f a n on) and two f o r c o n f i g u r a t i o n V a ( f u r n a c e f a n o f f ) , o b t a i n e d under similar w e a t h e r c o n d i t i o n s . The r e s u l t s i n d i c a t e a s t r a i g h t l i n e r e l a t i o n s h i p between t h e l o g a r i t h m of t r a c e r g a s c o n c e n t r a t i o n and t i m e f o r a l l t h r e e c a s e s . T h i s s u g g e s t s t h a t a d e q u a t e t r a c e r g a s mixing was a c h i e v e d i n t h e t e s t s p a c e s . With t h e f u r n a c e f a n o f f , t h e t r a c e r g a s decay r a t e f o r t h e basement i s much g r e a t e r t h a n t h a t f o r t h e f i r s t s t o r e y l i v i n g a r e a ; t h a t i s , t h e l o c a l a i r change r a t e w a s g r e a t e r i n t h e basement t h a n i n t h e l i v i n g a r e a . The e f f e c t o f f u r n a c e f a n o p e r a t i o n on l o c a l a i r change i s shown i n F i g s . 12 and 1 3 f o r t h e f o u r c o n f i g u r a t i o n s .
C o n f i g u r a t i o n s IIa and V a , shown i n Fig. 1 2 , have t h e o u t d o o r a i r s u p p l y d u c t e d t o t h e h e a t i n g system, a s i n h o u s e s w i t h g a s - h e a t e d , f o r c e d - a i r h e a t i n g systems. C o n f i g u r a t i o n I1 r e p r e s e n t s t h e o f f - c y c l e c o n d i t i o n w i t h h i g h o r medium e f f i c f e n c y g a s f u r n a c e s . C o n f i g u r a t i o n Va r e p r e s e n t s t h e o f f - c y c l e c o n d i t i o n w i t h a n a t u r a l - d r a u g h t g a s f u r n a c e . ' h e a i r change r a t e s measured i n t h e basement and i n t h e l i v i n g s p a c e w i t h c o n f i g u r a t i o n 11, ( F i g . 1 2 a ) were a l m o s t i d e n t i c a l , i n d i c a t i n g r e a s o n a b l e mixing of a i r i n t h e h o u s e even w i t h t h e f u r n a c e f a n o f f . T h i s i s b e c a u s e t h e a i r d i s t r i b u t i o n d u c t of t h e h e a t i n g s y s t e m p e r m i t s a i r e n t e r i n g
through t h e v e n t opening t o r e a c h t h e l i v i n g a r e a . The a i r change
r a t e w i t h t h e f u r n a c e f a n o f f was up t o 15% lower t h a n t h a t w i t h t h e f u r n a c e f a n o p e r a t i n g c o n t i n u o u s l y . T h i s i s r e f l e c t e d i n Fig. 12c; t h e a i r f l o w t h r o u g h t h e o u t d o o r a i r d u c t w i t h t h e f u r n a c e f a n o f f was n e a r l y c o n s t a n t a t 6 L / s and a b o u t o n e - t h i r d of t h e f l o w w i t h t h e f a n on. 1 1 . 1 6
-
I I I T 1 1 1 1 1 1 1 ~ --OW-c,
L I V I ~ G A R E A 5 0 -0-.-
--0----.-
v-
-
D l o - \<v,, B A S E M E N T-
\
-
y - M I X I N G B Y F U R N A C E F A N 1 o l 0-
at 3 5 . 5 K , W 1 6 . 4 k m / h ( W S W ) , o I 0 3 5 o c / h Va - M I X I N G B Y FLOOR F A N S nt.
3 4 4 K , w 1 3 . 4 k m / h ( E N E ) , L I V I N G A R E A , I 0 2 3 o s / h o B A S E M E N T , I 0 6 7 o c / h I I I I I I I I I I I 0 5 111 1 5 20 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0o . Us - FURNACE FAN OFF, WITH AIR DISTRIBUTION SYSTEM o . BASEMENT O 3 n L I V I N G SPACE 0 . 2 ", A t , TEMPERATURE DIFFERENCE, K
Vo - FURNACE F A N OFF, WITH AIR DISTRIBUTION SYSTEM o : BASEMENT n . L I V I N G SPACE
-1
I 1 0 1 0 ' 0 I 0 0 0 0 0 0 o0-
-
o . 11 FURNACE FAN O N - . no>FURNACE FAN OFF
-
-
"
"0 n 0 + b b-
a .'a a +-
-
( 0 1 l t l I 1 1 I 0 2 0 3 0At, TEMPERATURE DIFFERENCE, K
F i g u r e 12. E f f e c t of f u r n a c e f a n on a i r f l o w r a t e t h r o u g h i n t a k e v e n t a n d h o u s e a i r change r a t e
With an e x h a u s t s t a c k i n t h e basement ( c o n f i g u r a t i o n V a
-
F i g . 1 2 b ) , t h e a i r change r a t e i n t h e basement was c o n s i s t e n t l y h i g h e r t h a n t h a t measured i n t h e l i v i n g s p a c e above. T h i s s u g g e s t s t h a t much of t h e a i r l e a k i n g i n t o t h e basement e s c a p e d d i r e c t l y t h r o u g h t h e e x h a u s t s t a c k . The a i r change r a t e i n t h e l i v i n g s p a c e , ( t h e e f f e c t i v e v e n t i l a t i o n r a t e ) w i t h t h e f a n o f f was a b o u t 25% l o w e r t h a n t h a t w i t h t h e f a n on. T h i s i s a l s o shown i n F i g . 12c; t h e s u p p l y a i r f l o w w i t h f a n o f f , a l t h o u g h s t r o n g l y a f f e c t e d by s t a c k a c t i o n , remained l o w e r t h a n t h e f l o w w i t h t h e f a n on. I n Fig. 13, c o n f i g u r a t i o n s 111, and I V a , w i t h t h e v e n t s d i s c o n n e c t e d from t h e a i r d i s t r i b u t i o n s y s t e m , had a s u b s t a n t i a l l y h i g h e r a i r change r a t e i n t h e basement t h a n i n t h e l i v i n g s p a c e . The d i f f e r e n c e i n a i r change r a t e was g r e a t e r w i t h c o n f i g u r a t i o n I V a ( F i g . 13b). With b o t h i n t a k e v e n t and e x h a u s t s t a c k l o c a t e d i n t h e basement, o u t d o o r a i r e n t e r i n g t h r o u g h t h e v e n t opening i n t h e basement bypassed t h e l i v i n g a r e a and went d i r e c t l y o u t
t h r o u g h t h e e x h a u s t s t a c k . Consequently, o u t d o o r a i r e n t e r i n g t h r o u g h t h e v e n t was n o t v e n t i l a t i n g t h e l i v i n g s p a c e . Moreover, t h e a i r i n f i l t r a t i o n t h r o u g h t h e basement w a l l was a l s o b y p a s s i n g t h e l i v i n g s p a c e .
- FURNACE FAN OFF, WITHOUT AIR DlSTRlWllON SYSTEM
"1
1
0 : BASEMENT4 : LIVING SPACE
0 . 4
,a, 0 10 2 0 3 0 4 0
4 0 . 5 AIR DlSTRl8UTlON SYSTEM 0 . 4
0
at. TEMPERATURE D I F F E R E N C E , K
Figure 13. Effect of air distribution system on house air change rate
0 . 5 I
z I ' I ' I 1
LOCATION OF STACK INLET
0
-
.z 0 SECOND FLOOR -2
0 . 3-
O B A S E M E N T - ~ 0 . O e O-
l j z 0 . 2-
1-
= 0 . 1-
-at, TEMPERATURE DIFFERENCE. K
Figure
14.
Effect of location of stack intake on house air change7.
EFFECT OF EXHAUST STACK CONFIGURATIONF i g u r e 14 compares t h e house a i r change rate and t h e e x h a u s t s t a c k f l o w of c o n f i g u r a t i o n s I11 and V I , which d i f f e r e d o n l y i n t h e l o c a t i o n of t h e i n l e t t o t h e e x h a u s t s t a c k . Both t h e house a i r change r a t e and t h e e x h a u s t s t a c k f l o w remained r e l a t i v e l y
unchanged r e g a r d l e s s of whether t h e i n d o o r a i r e x h a u s t e d from t h e basement o r f r o m t h e second s t o r e y . The l o c a t i o n o f s t a c k i n l e t h a s v e r y l i t t l e e f f e c t on t h e v e n t i n g performance of a n e x h a u s t
s t a c k when t h e f u r n a c e f a n i s on. However, when t h e f u r n a c e f a n i s o f f , o r when t h e r e i s no a i r d i s t r i b u t i o n s y s t e m , t h e p r e f e r r e d l o c a t i o n of t h e i n l e t t o t h e e x h a u s t s t a c k i s i n t h e l i v i n g s p a c e . T h i s l o c a t i o n w i l l e n s u r e t h a t outdoor a i r e n t e r i n g t h e basement, e i t h e r t h r o u g h t h e w a l l o r t h r o u g h a v e n t i l a t i o n i n l e t , w i l l p a s s t h r o u g h t h e l i v i n g s p a c e .
8. EFFECT OF VENT OPENING LOCATION
House a i r change r a t e s were measured w i t h a 12.7 cm d i a m e t e r v e n t i n s t a l l e d a t v a r i o u s l o c a t i o n s i n t h e h o u s e e n c l o s u r e
( c o n f i g u r a t i o n s I , and V I I I t o XI). The v e n t was l o c a t e d n e a r t h e s i l l of a f i r s t s t o r e y window, o r n e a r t h e h e a d o f a second s t o r e y window ( F i g . 1 5 ) .
.
NORTH WINDOW. FIRST STOREY - Pm 0 NORTH WINDOW, 0 . 3 SECOND STOREY - IX O , 0 n IY 05
a . 5 I I x 1 u m W T H WINDOW, w-
0 ' 4-
FlRST STOREY-
X 4.
0 SOUTH W l N r n W , a . 3-
M BASEMENT-
I. '
11.2-
.oB- 0 . 1-
.
NORTH WINDOW, L-
FIRST STOREY - 0 SOUTH WINDOW, 8 0 %-
FIRST STOREY - X-
0 O-
.'OD 0 a + . , e O O-
( c )-
5 < W c 2 6 . 4 km/h I I I 1 I I 0 NORTH W I N D O W ,-
SECOND STOREY - IX 0 EAST WINDOW, SECOND * O-
STOREY - XI .**
. a - 6 O-
.
O P .-
0 - 7 < W c 2 7 k m / h ( 4-
I 1 I A t . T E M P E R A T U R E D I F F E R E N C E , KF i g u r e 15. E f f e c t of v e n t l o c a t i o n on house a i r change f o r wind s p e e d s u p t o 25 km/h
The h o u s e a i r change r a t e w a s n o t s t r o n g l y a f f e c t e d by a n
e l e v a t i o n a l change of t h e v e n t o p e n i n g , n o r by whether t h e v e n t opening was a c t i n g a s a n i n t a k e v e n t ( V I I I ) o r a s a n e x h a u s t
v e n t (IX) ( F i g . 1 5 a ) . There was no a p p a r e n t d i f f e r e n c e ( F i g . 15b) i n h o u s e a i r change r a t e between a basement v e n t l o c a t i o n ( I ) a n d a f i r s t - s t o r e y l o c a t i o n
(X),
even though t h e a r e a of t h e basement v e n t was 38% less t h a n t h a t of t h e f i r s t s t o r e y v e n t . Thed i r e c t i o n a l o r i e n t a t i o n of t h e v e n t opening had no n o t i c e a b l e e f f e c t ( F i g s . 1 5 c , d ) o n h o u s e a i r change f o r wind s p e e d s u p t o 27 km/h. These r e s u l t s a g a i n s u p p o r t t h e c o n c l u s i o n t h a t s t a c k a c t i o n i s t h e d o m i n h t d r i v i n g p o t e n t i a l f o r p a s s i v e v e n t i l a t i o n .
EFFECT OF VENT SIZE
F i g u r e 16 shows t h e measured house a i r change r a t e s w i t h two 10 cm v e n t s (5.3 m a p a r t ) i n t h e same w a l l ( V I I )
.
The h o u s e a i r change r a t e s w i t h two v e n t s were o n l y s l i g h t l y g r e a t e r t h a n t h o s e w i t h one v e n t , p r o b a b l y b e c a u s e t h e a i r f l o w t h r o u g h t h e v e n t s ( o n a v e r a g e 7.5 L / s p e r v e n t ) d i d n o t have a s i g n i f i c a n t i n f l u e n c e o n h o u s e a i r change. The a i r change r a t e c a l c u l a t e d from Eq. 3 f o r two v e n t s o v e r p r e d i c t e d t h e measured v a l u e s . Q ! , T E M P E R A T U R E D I F F E R E N C E , K F i g u r e 16. House a i r change r a t e-
c o n f i g u r a t i o n V I I 10. SUMMARY 10.1 A l l t h e p a s s i v e v e n t i l a t i o n s y s t e m s t e s t e d i n c r e a s e d t h e h o u s e a i r change r a t e o v e r t h a t of t h e h o u s e w i t h n o v e n t s ( T a b l e 1 ) . Of t h e f i v e b a s i c s y s t e m s , c o n f i g u r a t i o n V produced t h e h i g h e s t h o u s e a i r change r a t e , f o l l o w e d by c o n f i g u r a t i o n s I V , 11, 111, a n d I. For example, a t A t . = 34K, t h e measured house a i r change r a t e s werea b o u t 0.42 and 0.35 a c / h f o r V and I V , a n d t h e y were a b o u t 0.33, 0.3 and 0.26 f o r 11, 111 and I , r e s p e c t i v e l y . 10.2 S t a c k a c t i o n was t h e dominant d r i v i n g p o t e n t i a l f o r p a s s i v e v e n t i l a t i o n w i t h wind s p e e d s l e s s t h a n 30 h / h . However, s i g n i f i c a n t f l o w a u g m e n t a t i o n was p r o v i d e d by t h e a i r c i r c u l a t i n g f a n of t h e f o r c e d - a i r h e a t i n g s y s t e m when t h e v e n t was c o n n e c t e d d i r e c t l y t o t h e h e a t i n g system. 10.3 The o r i e n t a t i o n and e l e v a t i o n of t h e v e n t o p e n i n g a p p e a r e d t o h a v e v e r y l i t t l e e f f e c t on h o u s e a i r change w i t h wind s p e e d s l e s s t h a n 27 km/h.
10.4 The l o c a t i o n where t h e e x h a u s t s t a c k withdraws i n d o o r a i r had v e r y l i t t l e e f f e c t o n h o u s e a i r change r a t e w i t h t h e f u r n a c e f a n o p e r a t i n g , b u t c o u l d have a s i g n i f i c a n t e f f e c t on t h e e f f i c i e n t mixing of o u t d o o r a i r w i t h t h e a i r i n t h e l i v i n g s p a c e . 10.5 An a i r d i s t r i b u t i o n s y s t e m s i g n i f i c a n t l y improves t h e d i s t r i b u t i o n and mixing of o u t d o o r a i r t h a t e n t e r s t h r o u g h v e n t o p e n i n g s a n d i n f i l t r a t e s t h r o u g h o p e n i n g s and c r a c k s i n t h e basement w a l l w i t h t h e i n d o o r a i r . 10.6 Methods f o r e s t i m a t i n g t h e a i r t i g h t n e s s c h a r a c t e r i s t i c of a h o u s e w i t h v e n t o p e n i n g s and t h e e f f e c t of t h e s e o p e n i n g s o n t h e n e u t r a l p r e s s u r e l e v e l h a v e been p r e s e n t e d . The d e r i v e d c h a r a c t e r i s t i c s and Eq. 3 p r o v i d e a r e a s o n a b l e e s t i m a t e of h o u s e a i r change r e s u l t i n g from p a s s i v e v e n t i l a t i o n s y s t e m s f o r t e m p e r a t u r e d i f f e r e n c e s g r e a t e r t h a n 1 5 K.
11. REFERENCES
1. SCHEUNEMAN, E.C.
"Mark X I Energy R e s e a r c h P r o j e c t , Summary o f R e s u l t s ,
1978-1981", B u i l d i n g P r a c t i c e Note 27, D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l Re s e a r c h C o u n c i l Canada, Ottawa, 1982. 2. SHAW, C.Y. and TAMURA, G.T.
"Mark X I Energy R e s e a r c h P r o j e c t , A i r t i g h t n e s s and Air
I n f i l t r a t i o n Measurements", B u i l d i n g Research Note 162, D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l Canada, Ottawa, 1980.
3. SHAW, C.Y.
"A C o r r e l a t i o n Be tween A i r I n f i l t r a t i o n a n d A i r t i g h t n e s s f o r Houses i n a Developed R e s i d e n t i a l Area", ASHRAE Trans. -9 87 P a r t 2, 1981.
4.
SHAW, C.Y. and BROWN, W.C." E f f e c t of A Gas Furnace Chimney on t h e A i r l e a k a g e
C h a r a c t e r i s t i c of A Two-Storey Detached House", P r o c e e d i n g s , 3 r d A I C Conference, Energy E f f i c i e n t Domestic V e n t i l a t i o n Systems f o r A c h i e v i n g A c c e p t a b l e I n d o o r Air Q u a l i t y , London, U.K., September 1982, p. 12.1-12.13.
5. SHAW, C.Y.
"The Ef f e c t of Mechanical V e n t i l a t i o n o n t h e Air Leakage C h a r a c t e r i s t i c of a Two-Storey Detached House", B u i l d i n g R e s e a r c h Note 204, D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l Research Council Canada, Ottawa, 1983.
6. BASSETT, M.R., SHAW, C.Y. and EVANS, R.G.
"An A p p r a i s a l of t h e S u l p h u r H e x a f l u o r i d e Decay Technique f o r Measuring A i r I n f i l t r a t i o n R a t e i n B u i l d i n g s " , ASHRAE
T r a n s .
87,
P a r t ..2, 1981.Acknowledgement
The a u t h o r s w i s h t o t h a n k D.L. Logan f o r h i s a s s i s t a n c e i n c o n d u c t i n g t h e t e s t s . T h i s p a p e r i s a c o n t r i b u t i o n from t h e D i v i s i o n of B u i l d i n g Research, N a t i o n a l Research Council o f
Canada, and i s p u b l i s h e d w i t h t h e a p p r o v a l of t h e D i r e c t o r o f t h e D i v i s i o n .
12. APPENDIX A ESTIMATION OF C , n AND NEUTRAL PRESSURE LEVEL FOR HOUSES WITH VENTS
12.1 Flow C o e f f i c i e n t and Exponent
The a i r l e a k a g e c h a r a c t e r i s t i c of a h o u s e b e f o r e i n s t a l l a t i o n of a v e n t i l a t i o n s y s t e m c a n b e d e f i n e d by t h e e q u a t i o n , where : Q = a i r l e a k a g e r a t e , L / s , C = f l o w c o e f f i c i e n t , L / ( S *rn2.pan), A = a r e a of b u i l d i n g e n v e l o p e , m 2 , AP = p r e s s u r e d i f f e r e n c e , Pa, n = f l o w exponent.
A f t e r t h e i n s t a l l a t i o n of a p a s s i v e v e n t i l a t i o n system, t h e t o t a l a i r l e a k a g e of t h e h o u s e a s d e t e r m i n e d by a f a n p r e s s u r i z a t i o n t e s t , would b e t h e sum of t h e a i r l e a k a g e t h r o u g h t h e b u i l d i n g e n v e l o p e and t h e a i r f l o w t h r o u g h t h e v e n t . Thus, where : Q' = a i r l e a k a g e r a t e w i t h v e n t , L / s , Qv = a i r f l o w r a t e t h r o u g h t h e v e n t , L / s . To e s t i m a t e t h e v a l u e of Qv, t h e f o l l o w i n g two c a s e s a r e c o n s i d e r e d : ( a ) I f t h e v e n t i s c o n n e c t e d t o t h e f o r c e d a i r h e a t i n g s y s t e m w i t h t h e f u r n a c e f a n o p e r a t i n g c o n t i n u o u s l y , t h e n Qv can b e assumed t o b e c o n s t a n t b e c a u s e of t h e l a r g e s u c t i o n i n t h e s u p p l y d u c t i n d u c e d by t h e f u r n a c e f a n . Measurements c o n d u c t e d on t h e t e s t house h a v i n g a 10 c m s u p p l y d u c t i n d i c a t e t h a t Q v was a b o u t 18 L / s under t y p i c a l w i n t e r c o n d i t i o n s . For s i m i l a r o r less a i r t i g h t h o u s e s , Qv would b e p r o p o r t i o n a l t o t h e s i z e of t h e s u p p l y d u c t ,
where D i s t h e d i a m e t e r of t h e s u p p l y d u c t i n c m .
(b) I f t h e v e n t i s j u s t an opening i n t h e b u i l d i n g e n v e l o p e , Qv would be a f u n c t i o n of t h e p r e s s u r e d i f f e r e n c e i n d u c e d by t h e
p r e s s u r i z a t i o n f a n , AP. Thus, Qv c o u l d b e approximated by t h e o r i f i c e e q u a t i o n , L e t t h e o r i f i c e d i s c h a r g e c o e f f i c i e n t Cd = 0.6, t h e above e q u a t i o n becomes where: p = d e n s i t y of i n d o o r a i r , kg/m3,
%
= a r e a of t h e v e n t , m 2 ,AP
= p r e s s u r e d i f f e r e n c e a c r o s s h o u s e e n v e l o p e a s i n d u c e d by a p r e s s u r i z a t i o n f a n , Pa.S u b s t i t u t i n g Eq. A 3 o r A4 i n t o Eq. A2, v a l u e s of Q ' c a n b e
c a l c u l a t e d f o r t h e r a n g e of AP n o r m a l l y u s e d i n a p r e s s u r i z a t i o n test. By f i t t i n g t h e s e d a t a t o t h e a i r f l o w e q u a t i o n ( A l ) , t h e v a l u e s of C and n f o r t h e h o u s e w i t h v e n t s c a n b e d e r i v e d .
Values of C and n were c a l c u l a t e d f o r c o n f i g u r a t i o n s I , 11, 111, I V , V and V I I . Because t h e c a l c u l a t e d and t h e measured v a l u e s of n were v e r y c l o s e , t h e v a l u e s of C were r e c a l c u l a t e d u s i n g Eq. A1 and t h e measured v a l u e s of n , t o f a c i l i t a t e comparison o f t h e
measured a n d t h e c a l c u l a t e d C. The c a l c u l a t e d and measured v a l u e s of C , p r e s e n t e d i n T a b l e A l , show good agreement.
FIN. 2ND FLOOR
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----1 I FIN. rrr worn---
I " - - - - I-_-. C% - 8 - 6 - 4 - 2 G 1 1 6 0 5 P , P R E I S U R E D I F F E R E N C E . Pe F i g u r e A l . D i s t r i b u t i o n of l e a k a g e o p e n i n g s and p r e s s u r e d i f f e r e n c e p r o f i l e c a u s e d by s t a c k a c t i o n 12.2 N e u t r a l P r e s s u r e Level I f v e n t o p e n i n g s a r e i n s t a l l e d i n a h o u s e e n v e l o p e a s shown i n Fig. A l , t h e n e u t r a l p r e s s u r e l e v e l (NPL) w i l l s h i f t t o h' f r o m h and t h e p r e s s u r e d i f f e r e n c e a c r o s s t h e h o u s e e n v e l o p e due t o s t a c k a c t i o n w i l l change a c c o r d i n g l y . Assuming t h a t : (1) t h e a i r l e a k a g e c h a r a c t e r i s t i c of t h e house w i t h o u t v e n t s c a n ber e p r e s e n t e d by two openings: one l o c a t e d a t g r a d e l e v e l a n d t h e o t h e r a t t h e c e i l i n g l e v e l of t h e t o p s t o r e y , and t h a t ( 2 ) t h e v e r t i c a l d i s t r i b u t i o n of p r e s s u r e d i f f e r e n c e of t h e h o u s e w i t h o u t v e n t s i s known, t h e new n e u t r a l p r e s s u r e l e v e l ( h ' ) c a n b e e s t i m a t e d from t h e mass f l o w b a l a n c e e q u a t i o n : where: CAb = o v e r a l l f l o w c o e f f i c i e n t below n e u t r a l p r e s s u r e l e v e l , L / ( s - P ~ " ) ,
