Indoor formaldehyde levels in houses with different ventilation strategies

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Indoor formaldehyde levels in houses with different ventilation

strategies

Figley, D. A.

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Indoor Formaldehyde Levels in Houses

with Different Ventilation Strategies

by D.A. Figley

Appeared in

Proceedings 6th AIC Conference

"Ventilation Strategies and Measurement Techniques"

Het Meerdal Park, Southern Netherlands

September 16

-

19, 1985

P.

17.1 -17.11

(IRC Paper No. 1447)

Reprinted with permission

Price $2.00

NRCC 27471

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ABSTRACT

P o s s i b l e build-up of p o l l u t a n t l e v e l s i n low-energy houses i s i n c r e a s i n g l y under i n v e s t i g a t i o n . F i e l d d a t a are p r e s e n t e d on t h e i n d o o r formaldehyde (HCOH) c o n c e n t r a t i o n s i n a group of 33 r e l a t i v e l y new low-energy houses.

~ S U &

On se penche d e p u i s un c e r t a i n temps s u r l a q u e s t i o n d e l ' a u g m e n t a t i o n p o s s i b l e d e s t a u x d e p o l l u a n t s d a n s l e s maisons

2

f a i b l e consommation 6 n e r g 6 t

ique.

C e document p r g s e n t e d e s d o n n h s c o n c e r n a n t les c o n c e n t r a t i o n s de formald6hyde (HCOH) I r e l e v c e s dans un groupe d e

33

rnaisons

3

f a i b l e consommation

Gnerggtique d e c o n s t r u c t i o n r e l a t i v e m e n t n o u v e l l e . - - - - -. w I I * 1809 002 - L

INDOOR FORMALDEHYDE LEVELS IN HOUSES WITH DIFFERENT VENTILATION STRATEGIES

D.A. Figley Research Officer

Division of Building Research

National Research Council of Canada Saskatoon, Sask., Canada

1. Synopsis

This paper d i s c u s s e s t h e indoor formaldehyde l e v e l s i n two groups of houses. With t h e e x c e p t i o n of t h e h e a t i n g and v e n t i l a t i o n systems, t h e house c o n s t r u c t i o n , formaldehyde s o u r c e s and occupancy were s i m i l a r f o r t h e two groups. One group ( A ) used e l e c t r i c baseboard c o n v e c t i v e h e a t e r s f o r s p a c e h e a t i n g and

semi-ducted h e a t recovery v e n t i l a t o r s (HRV) f o r s u p p l y i n g outdoor a i r and e x h a u s t i n g i n d o o r a i r . The second group (B) had e l e c t r i c f o r c e d - a i r f u r n a c e s w i t h a ducted a i r s u p p l y t o e v e r y room.

Outdoor a i r was drawn i n v i a a connection t o t h e r e t u r n a i r ductwork.

During t h e w i n t e r , 77% of t h e Group A houses had bedroom

formaldehyde l e v e l s h i g h e r t h a n t h e l i v i n g room l e v e l s . I n t h e Group B houses, only 20% had a bedroom l e v e l h i g h e r t h a n t h e l i v i n g room l e v e l . These d a t a s u g g e s t t h a t t h e semi-ducted HRV systems p r o v i d e l i m i t e d a i r c i r c u l a t i o n w i t h i n t h e houses compared t o t h e f u l l y ducted f o r c e d - a i r f u r n a c e s .

The average w i n t e r HCOH l e v e l s were s i m i l a r f o r both house groups; however, t h e Group A houses had v e n t i l a t i o n r a t e s t w i c e a s h i g h a s t h e Group B houses. S i n c e t h e HCOH s o u r c e s t r e n g t h s w i t h i n t h e house groups should be e q u a l , s u p e r i o r mixing e f f i c i e n c y i n t h e Group B houses may be r e s p o n s i b l e .

The r e s u l t s a l s o show t h a t a continuous supply of v e n t i l a t i o n a i r i s n e c e s s a r y t o p r e v e n t t h e build-up of i n d o o r p o l l u t a n t s .

V e n t i l a t i o n systems t h a t a r e coupled t o t h e a i r

c i r c u l a t i o n / h e a t i n g system (Group B) a r e n o t r e l i a b l e d u r i n g low/no h e a t p e r i o d s . I n e n e r g y - e f f i c i e n t houses w i t h low a u x i l i a r y h e a t i n g requirements, i n d o o r a i r q u a l i t y problems may develop.

2. I n t r o d u c t i o n

Concerns o v e r t h e b u i l d - u p of p o l l u t a n t l e v e l s i n new "low-energy" houses have a r i s e n r e c e n t l y . T y p i c a l l y , low-energy houses have w e l l s e a l e d air-vapour b a r r i e r s t o minimize a i r l e a k a g e and u s e

mechanical systems t o supply v e n t i l a t i o n a i r .

This s t u d y was i n i t i a t e d t o p r o v i d e f i e l d d a t a on t h e i n d o o r formaldehyde (HCOH) c o n c e n t r a t i o n s i n a group of 33 r e l a t i v e l y new

(1-2 y e a r s o l d ) "low-energy" houses l o c a t e d i n Winnipeg and Pinawa, Manitoba. Using p a s s i v e d o s i m e t e r s , c o n c e n t r a t i o n s were measured i n December 1983 ( v e n t i l a t i o n v i a i n f i l t r a t i o n and mechanical system o n l y ) and a g a i n i n September 1984

The December 1983 HCOH data for a subgroup of 16 houses have already been analyzed in detail1 and the results indicated that for a given type of occupancy, indoor HCOH levels could be related to the ventilation rate by the simple expression (Fig. 1):

where Ci = indoor HCOH concentration (pg/m3)

c8

= = outdoor HCOH concentration (pg/m3) net apparent HCOH source strength (pg/s*m2)

9

= net ventilation rate (m3/s)

K

= mixing factor

(K

=

1

perfect mixing)

Af = main floor area (m2).

150

-

125

-

Ci-26 + too

-

75

-

50

-

25

-

CI UNOCCUPIED TEST I 8 UNOCCUPIED TEST 2 OCCUPIED SMOKING o OCCUPIED NON SMOKING

Fig. 1. Indoor formaldehyde concentration vs air flow rate for

four test cases (Ref. 1)

Conversely, the study demonstrated that pollutant concentration measurements in the absence of ventilation rate data are difficult to analyze since variations in concentration levels could be

caused by variations in pollutant source strengths and/or ventilation rates.

This paper is intended to outline the methodology of the indoor pollutant measurement program and discuss the implications of the data on the design of heating and ventilating systems for housing. This data base may also be of use to health professionals and policymakers who must assess the potential health risks of exposures to indoor pollutants.

For t h e purposes of t h e paper, v e n t i l a t i o n a i r w i l l r e f e r t o outdoor a i r i n t r o d u c e d i n t o t h e b u i l d i n g v i a i n f i l t r a t i o n o r

mechanical means. C i r c u l a t i o n a i r w i l l r e f e r t o a i r moving w i t h i n t h e b u i l d i n g e n c l o s u r e due t o t h e a c t i o n of a c e n t r a l f o r c e d - a i r d i s t r i b u t i o n system.

3. D e s c r i p t i o n of t h e Houses

A l l of t h e houses examined i n t h i s s t u d y were new, wood-frame s i n g l e - f a m i l y r e s i d e n c e s c o n t a i n i n g g l a s s f i b r e i n s u l a t i o n . The c a s t - i n - p l a c e c o n c r e t e basements were i n s u l a t e d on t h e i n t e r i o r u s i n g wood s t u d s and g l a s s f i b r e b a t t s .

The houses i n Group A were l o c a t e d i n Pinawa, Manitoba and

Winnipeg, Manitoba and were b u i l t by one c o n t r a c t o r u s i n g s i m i l a r c o n s t r u c t i o n m a t e r i a l s and techniques. The above-grade w a l l s were c o n s t r u c t e d u s i n g t h e double-stud technique. Heat recovery

v e n t i l a t o r s (HRV) were used t o s u p p l y o u t s i d e a i r and c i r c u l a t e a i r w i t h i n t h e houses. The u n i t s had i n t e r l o c k e d supply and e x h a u s t f a n s w i t h t h e ON/OFF o p e r a t i o n c o n t r o l l e d by a h u m i d i s t a t . The e x h a u s t a i r was removed ( v i a ductwork) from t h e k i t c h e n and bathroom. The o u t s i d e a i r was s u p p l i e d i n t o t h e c e n t r e of t h e basement and allowed t o m i g r a t e through t h e house. F l o o r r e g i s t e r s were c u t through t h e main f l o o r t o f a c i l i t a t e a i r movement between t h e main f l o o r and basement. E l e c t r i c baseboard h e a t e r s ( c o n v e c t i v e ) were used f o r s p a c e h e a t i n g .

The houses i n Group B were l o c a t e d i n Pinawa, Manitoba but were b u i l t by a d i f f e r e n t c o n t r a c t o r t h a n t h o s e i n Group A. The above-grade w a l l s were c o n v e n t i o n a l s i n g l e - s t u d . A l l o t h e r c o n s t r u c t i o n m a t e r i a l s and t e c h n i q u e s were s i m i l a r t o t h o s e used i n t h e Group A houses. Group B had e l e c t r i c f o r c e d - a i r h e a t i n g systems (20-kW i n p u t ) w i t h ducted supply a i r i n t o e v e r y room and two c e n t r a l i z e d main f l o o r r e t u r n a i r g r i l l e s . Outdoor a i r was s u p p l i e d v i a a 125-mm d i a m e t e r d u c t connected t o t h e r e t u r n a i r plenum. The single-speed f u r n a c e f a n (-400 L / s ) o p e r a t i o n was c o n t r o l l e d by h e a t i n g demand.

D e t a i l s on t h e houses a r e given i n Table 1. 4. Experimental Procedure

A i r t i g h t n e s s measurements3 were t a k e n f o r a l l of t h e house envelopes. T h i s involved d e p r e s s u r i z i n g t h e house u s i n g a n

e x h a u s t f a n and measuring t h e a i r f l o w , Q ( L / s ) , and corresponding v a l u e s of t h e d i f f e r e n t i a l p r e s s u r e a c r o s s t h e b u i l d i n g envelope, AP(Pa). Values f o r t h e flow c o e f f i c i e n t

,

c ( L / s * ~ ~ (pa)"), and f l o w exponent, n ( d i m e n s i o n l e s s ) , can t h e n be c a l c u l a t e d u s i n g t h e e x p r e s s i o n :

where A = a r e a of t h e b u i l d i n g envelope (m2).

The Group A houses were extremely a i r t i g h t , having a group a v e r a g e induced a i r leakage of 0.25 a i r change p e r hour ( a c h ) @50 Pa w i t h

Table 1. Basic House Data

Pressure Total Floor Test Result

House Year of Construction Volume Area Excluding ~ / ~ ( a c h Age of Code Construction Style (m3) Basement (m2) @ 50 Pa) Furniture

Croup 2 82 Bungalow 465 91.7 0.18 none

A 3 8 2 Bungalow 465 91.7 0.14 none 4 8 2 Bungalow 465 91.7 0.26 none 5 82 Bungalow 465 91.7 0.16 2-5 yr 6 N /A Bungalow 465 91.7 0.17 none 7 82 Bungalow 465 91.7 0.15 N/A 8 8 2 Bungalow 465 91.7 0.19 none 17 81 I$ Storey 513 92.6 0.25 new 18 8 1 Bungalow 465 91.7 0.22 3 yr 19 82 Bungalow 455 91.0 0.67 2 yr

LO 83 Split Level 374 76.9 N/A 2-5 yr

21 81 Bungalow 465 91.7 0.20 3 Yr 2 2 8 2 Split Level 373 75.1 0.19 2 yr 2 3 82 Bungalow 465 91.7 0.21 2 yr 24 8 1 I+ Storey 513 92.6 0.27 3 yr 25 N/A Rungalow 465 91.7 0.25 2 yr 26 8 2 Bungalow 465 91.7 0.32 2-5 yr

27 83 Split Level 304 59.3 0.39 new

2 8 N/ A Bungalow 465 91.7 0.23 2-5 yr

29 8 1 Bungalow 465 91.7 0.15 new

30 81 Bungalow 465 91.7 0.35 2 yr

3 1 N/A Bungalow 465 91.7 0.27 N/A

3 2 N/A Bungalow 465 91.7 0.28 2 Yr

33 N/A Bungalow 465 91.7 0.24 N/A

34 81 I+ Storey 513 92.7 0.49 3 yr

3 5 8 1 Bungalow 465 91.7 0.16 new

Group 9 82 Bungalow 477 95.6 N/A N/ A

B 10 8 2 It Storey 452 102.8 1.61 N/A

1 I N/A Bungalow 507 102.1 1.23 N/A

2 82 Bungalow 545 110.2 1.54 NIA 13 82 Bungalow 477 95.6 1.54 2 yr 14 82 Bungalow 545 110.2 1.95 N/A 15 82 If Storey 452 102.8 2.12 none a s t a n d a r d d e v i a t i o n of 0.12. For Group B, t h e a v e r a g e a i r l e a k a g e t e s t v a l u e was 1.67 a c h 6'50 Pa w i t h a s t a n d a r d d e v i a t i o n of 0.32. Data f o r t h e i n d i v i d u a l h o u s e s a r e g i v e n i n T a b l e 1. The t e s t s were conducted w i t h a l l i n t e n t i o n a l e n v e l o p e openings ( d o o r s , windows, a i r i n t a k e and e x h a u s t d u c t s ) blocked.

Two s e p a r a t e s e t s of HCOH and v e n t i l a t i o n measurements were t a k e n . One s e t ( T e s t 1 ) was t a k e n i n December 1983 and t h e s e c o n d

( T e s t 2) i n September 1984. The d a t a f o r T e s t 1 and 2 are p r e s e n t e d i n T a b l e s 2 and 3, r e s p e c t i v e l y .

Formaldehyde l e v e l s were measured i n t h e l i v i n g room and m a s t e r bedroom u s i n g Dupont C-60 d o s i m e t e r s exposed f o r a p p r o x i m a t e l y s e v e n days. During T e s t 2, o u t d o o r HCOH l e v e l s were measured a t f i v e r e p r e s e n t a t i v e l o c a t i o n s .

Elapsed t i m e m e t e r s were i n s t a l l e d t o m o n i t o r t h e ON t i m e of t h e i n t e r l o c k e d HRV f a n s . The HRV a i r f l o w r a t e s ( s u p p l y and e x h a u s t ) and t h e o u t s i d e a i r f l o w s t o t h e e l e c t r i c f u r n a c e s were measured u s i n g a h e a t e d p r o b e anemometer t r a v e r s e . A t t h e b e g i n n i n g and end of t h e HCOH t e s t i n g , t h e i n d o o r a i r t e m p e r a t u r e and r e l a t i v e humidity were e s t i m a t e d u s i n g a n a s p i r a t i n g psychrometer.

I n t e r v i e w s were conducted w i t h t h e household o c c u p a n t s t o d e t e r m i n e occupancy, smoking h a b i t s and n o n - b u i l d i n g - r e l a t e d p o l l u t a n t s o u r c e s .

Outdoor a i r t e m p e r a t u r e and wind speed d a t a were t a k e n from Environment canada4 summaries.

A n a l y s i s of Data

The t o t a l v e n t i l a t i o n r a t e (VT) f o r t h e Group A houses was c a l c u l a t e d a s :

where VM = time-averaged mechanical v e n t i l a t i o n flow r a t e ( a c h )

V1 = i n f i l t r a t i o n flow r a t e (ach).

For t h e Group A houses, VM was c a l c u l a t e d by d i v i d i n g t h e t o t a l v o l u m e t r i c a i r flow r a t e through t h e HRV d u r i n g t h e t e s t ( t o t a l running time X average d u c t a i r v e l o c i t y ) by t h e t o t a l t e s t time. I n most c a s e s , t h e supply and e x h a u s t a i r flows through t h e HRV

were n o t balanced, s o t h e l a r g e r of t h e two v a l u e s was used. This would normally r e s u l t i n a mechanically induced p r e s s u r e

d i f f e r e n c e which would u p s e t t h e i n f i l t r a t i o n . However, s i n c e t h e i n i t i a l c a l c u l a t e d v a l u e s of VI were r e l a t i v e l y s m a l l , no a t t e m p t was made t o c o r r e c t them. The v a l u e of VM f o r t h e Group B houses was c a l c u l a t e d by m u l t i p l y i n g t h e f u r n a c e ON time by t h e outdoor a i r flow r a t e w i t h t h e f u r n a c e f a n ON ( 3 5 L/s) and d i v i d i n g by t h e t o t a l t e s t t i m e . The f u r n a c e ON t i m e was approximated a s t h e t o t a l measured f u r n a c e e l e c t r i c a l energy consumption (kwh) d i v i d e d by t h e r a t e d h e a t o u t p u t (20 kW).

shaw's5 method was used t o c a l c u l a t e t h e i n f i l t r a t i o n r a t e (VI) u s i n g t h e v a l u e from t h e f a n d e p r e s s u r i z a t i o n t e s t .

The w i n t e r v a l u e s were c a l c u l a t e d f o r Type 1 i n f i l t r a t i o n (temperature-driven) d a t a u s i n g t h e e x p r e s s i o n :

where V = house volume (m3)

AT = average indoor/outdoor t e m p e r a t u r e d i f f e r e n c e (OC). The summer v a l u e s assume Type 2 i n f i l t r a t i o n (wind-driven) and were c a l c u l a t e d a s :

where v = wind speed (m/s).

The v a l u e s f o r VT a r e g i v e n i n Tables 2 and 3. The summer v a l u e s of VT w i l l n o t r e p r e s e n t t h e t o t a l v e n t i l a t i o n r a t e s i n c e windows were f r e q u e n t l y opened.

The average of t h e l i v i n g room and bedroom i n d o o r a i r HCOH l e v e l s f o r t h e Group A houses a r e shown i n F i g s . 2a and 2c. Figs. 2b and 2d show t h e d i s t r i b u t i o n of t h e a v e r a g e i n d o o r HCOH c o n c e n t r a t i o n f o r t h e Group B houses.

Table 3. T e s t 2 (Summer) Data

OCCUPANCY HOUSE TEMP RH VT LR HCOH BR HCOH AV HCOH (BR-LR)/LR ( ~ d u l t s l RADON CODE (OC) ( % ) ( a c h ) ( P P ~ ) (ppm) (ppm) ( % d i f f . ) C h i l d r e n ) (pCi/L)

Group 2 20.6 47 0.52 0.041 0.056 0.049 36.6 0 3.08 A 3 21.1 50 0.52 0.055 0.076 0.066 38.2 0 6.27 4 20.0 52 0.26 0.034 0.032 0.033 -5.9 21 1 6.94 5 19.7 48 0.37 0.029 0.047 0.038 b2.1 3.16 6 N/A N/A N/A N/A N/A N/A N/A 0 N/A 7 18.9 52 0.77 0.033 0.028 0.031 -15.2 211 1.91 8 18.9 48 0.01 0.047 0.051 0.049 8.5 2/ 2 5.93 17 20.6 51 0.39 0.048 0.067 0.058 39.6 2.02 18 22.2 56 0.12 0.068 0.057 0.063 -16.2 4'0 21 2 2.97 19 22.8 53 N / A 0.101 0.100 0.101 -1.0 210 1.07 20 20.6 52 0.33 N/A 0.030 0.030 N / A 214 2.43 21 21.1 52 0.36 0.039 0.046 0.043 17.9 4.19 22 22.8 69 0.38 0.132 0.087 0.110 -34.1 210 8.57 23 18.9 61 0.29 0.082 0.079 0.081 -3.7 210 2.30 24 21.7 60 0.07 0.101 0.090 0.096 -10.9 210 N/A 25 22.8 49 0.01 0.049 0.043 0.046 -12.2 212 6.27 26 22.2 48 0.64 0.055 0.069 0.062 25.5 210 2.20 27 19.4 38 0.33 0.045 0.068 0.057 51.1 110 N/A 28 20.0 54 0.54 0.058 0.054 0.056 -6.9 21 2 4.75 29 21.1 51 0.22 0.048 0.046 0.047 -4.2 211 1.42 30 21.1 44 0.53 0.029 0.037 0.033 27.6 21 2 5.05 31 22.2 45 0.06 0.059 0.037 0.048 -37.3 1.34 32 22.2 42 0.01 0.038 0.047 0.043 23.7 2/ 1 1.27 33 22.2 64 0.33 0.088 0.100 0.094 13.6 212 1.11 34 22.2 56 0.31 0.097 0.072 0.085 -25.8 410 2.10 35 20.0 60 0.01 0.066 0.062 0.064 -6.1 210 2.10 Group 9 16.1 77 N/A 0.178 0.182 0.180 2.2 0 N / A B 10 19.4 53 0.08 0.054 0.048 0.051 -11.1 410 5.60 11 20.0 71 0.05 0.106 0.093 0.100 -12.3 6.27 12 19.4 53 0.06 0.115 0.038 0.077 -67.0 2/1 2/ 1 7.95 13 19.4 57 0.06 0.037 0.036 0.037 1.4 212 2.41 14 20.0 50 0.10 0.086 0.130 0.108 51.2 2.07 15 18.6 59 0.10 0.185 0.235 0.210 27 .O 0 9.96 LR = l i v i n g room; BR = bedroom

Table 2. T e s t 1 (Winter) Data

HOUSE CODE Group 2 A 3 4 5 6 7 8 17 18 19 20 21 22 23 24 25 26 27 28 29 30 3 1 32 33 34 35 Group 9 B 10 11 12 1 3 14 15 TEMP RH V T LR HCOH ("C) (XI (ach) (ppm) 22 29 0.51 0.035 14 57 0.16 0.057 20 34 0.55 0.039 20 34 0.18 0.061 21 31 0.42 0.051 17 55 0.77 0.056 19 49 0.01 0.109 21 48 0.29 0.074 N/A NIA N/A N/A

23 38 N/A 0.093 20 32 0.40 0.042 21 33 0.35 0.063 23 46 0.33 0.069 19 45 0.28 0.103 N / A N/A 0.20 N / A N/A N/A 0.26 N / A 22 48' 0.61 0.123 N/A NJA N / A N/A

20 46 0.53 0.089 23 42 0.52 0.066 22 41 0.52 0.054 20 52 0.36 0.067 21 46 0.53 0.051 22 38 N/A 0.060 22 48 0.26 0.112 19 48 0.01 0.048 BR HCOH ( P P ~ ) OCCUPANCY AV HCOH (BR-LK)/LR (Adults/ RADON

( P P ~ ) (% d i f f . ) C h i l d r e n ) (pCi/L)

LK = l i v i n g roolo; BR = bedroom

6 ' I 1 ' ' I I I I I . OCCUPlEO

1

5 - UNOCCUPIED

0

. 4 _{GROUP A} TEST I 3

-

+ 2 LL o 02 4 06 08 la Ir I4 0 OCCUPIED UNOCCUPIED GROUP B TEST I GROUP B TEST 2

J

Fig. 2. D i s t r i b u t i o n of t h e a v e r a g e indoor formaldehyde l e v e l s

The d i s t r i b u t i o n of p o l l u t a n t l e v e l s i n t h e houses was a l s o examined by comparing t h e p e r c e n t a g e d i f f e r e n c e between t h e bedroom and l i v i n g room HCOH c o n c e n t r a t i o n s . The r e s u l t s a r e shown i n F i g s . 3a (Group A) and 3b (Group

B)

f o r T e s t 1, and Figs. 3c and 3d r e s p e c t i v e l y f o r Test 2.

6. Discussion

To d a t e , Canada does n o t have a n a c c e p t e d s t a n d a r d t h a t d e f i n e s t h e maximum a l l o w a b l e HCOH c o n c e n t r a t i o n i n r e s i d e n c e s . For t h e purposes of t h i s d i s c u s s i o n , 0.1 ppm6 w i l l be used a s a n a r b i t r a r y s t a n d a r d .

The HCOH s o u r c e s i n t h e houses can be d i v i d e d i n t o two major

a r e a s : b u i l d i n g s o u r c e s and occupant s o u r c e s . The major b u i l d i n g s o u r c e s a r e assumed t o be u r e a formaldehyde r e s i n bonded p a r t i c l e board c o n s t r u c t i o n m a t e r i a l s i n c l u d i n g :

1 ) 9.5-mm s u b f l o o r

2) f ormica-covered c o u n t e r t o p s 3) k i t c h e n cupboards and v a n i t i e s

Table 4. Average V e n t i l a t i o n R a t e s and Indoor HCOH Levels For T e s t s 1 and 2

Winter ( T e s t 1 ) Summer ( T e s t 2)

House

_v~

HCOH _{"T HCOH}

Group ( P P ~ ) ( P P ~ )

A (unoccupied) 0.40 0.064 0.48 0.058

A (occupied) 0.35 0.078 0.29 0.060

B (unoccupied)

N

/A

N

/A 0.10 0.210

B (occupied) 0.18 0.075 0.07 0.075

The d i s t r i b u t i o n of t h e average HCOH c o n c e n t r a t i o n i n t h e Group A houses f o r December 1983 (Fig. 2a) shows t h a t o n l y t h r e e occupied

and one unoccupied house exceeded t h e 0.l-ppm l e v e l . The 17

occupied houses had a n average v e n t i l a t i o n r a t e of 0.4 ach and a mean i n d o o r HCOH l e v e l

(x)

of 0.078 ppm. For two of t h e t h r e e

occupied houses w i t h HCOH l e v e l s above 0.1 pprn (houses 23 and 34),

i n c r e a s e d o p e r a t i o n of t h e HRV f a n s ( s e e Fig. 1 ) c o u l d reduce t h e l e v e l s t o below 0.1 ppm. Both houses had a v e r a g e HCOH l e v e l s o n l y s l i g h t l y g r e a t e r t h a n 0.1 pprn w i t h VT v a l u e s below 0.3 ach. The o t h e r occupied house (house 26) had a l e v e l of 0.12 pprn w i t h t h e HRV o p e r a t i n g c o n t i n u o u s l y a t maximum flow (0.6 ach). For t h i s house, t h e mechanical v e n t i l a t i o n system was i n a d e q u a t e t o c o n t r o l

t h e indoor l e v e l below 0.1 ppm. I n t h e c a s e of t h e unoccupied house (house 8 ) , t h e HRV f a n s were s h u t o f f .

The Group B houses (Fig. 2b) maintained r e l a t i v e l y low HCOH l e v e l s d u r i n g t h e December 1983 test p e r i o d

( x

= 0.075 pprn). A l l of t h e houses were occupied and none of t h e i n d o o r l e v e l s exceeded

0.1 ppm.

For t h e w i n t e r t e s t , t h e average HCOH c o n c e n t r a t i o n i n t h e occupied Group B houses was comparable w i t h t h a t of t h e occupied Group A houses. However, t h e c a l c u l a t e d v e n t i l a t i o n r a t e was less

t h a n one-half. S i n c e t h e n e t HCOH s o u r c e s t r e n g t h should be s i m i l a r f o r both groups, t h e i n i t i a l comparison would i n d i c a t e a n i n c o n s i s t e n c y w i t h Equation 1. The most l i k e l y e x p l a n a t i o n l i e s w i t h t h e v a l u e of t h e mixing f a c t o r

K.

The f o r c e d c i r c u l a t i o n Group B houses would have a l a r g e r mixing f a c t o r t h a n t h e Group A houses.

The summer (September 1984) v a l u e s f o r t h e occupied, Group A houses showed a g e n e r a l r e d u c t i o n i n t h e i n d o o r l e v e l s

(E

= 0.060 ppm) when compared t o t h e p r e v i o u s December 1983 d a t a . The average mechanical v e n t i l a t i o n r a t e was a l s o lower, s u g g e s t i n g t h a t a d d i t i o n a l v e n t i l a t i o n must have been s u p p l i e d v i a

undocumented window and door openings* I n t h i s group, two occupied houses had a v e r a g e i n d o o r HCOH l e v e l s m a r g i n a l l y above 0.1 ppm, a l t h o u g h i n c r e a s e d o p e r a t i o n of t h e HRV could have reduced t h e l e v e l s . The r e l a t i o n s h i p between t h e i n d o o r HCOH l e v e l and t h e v e n t i l a t i o n r a t e d i d n o t change f o r t h e unoccupied Group A houses ( t h i s assumes no occupants, hence no window o r door

openings), i n d i c a t i n g t h a t t h e n e t a p p a r e n t s o u r c e s t r e n g t h of t h e b u i l d i n g had n o t changed a p p r e c i a b l y .

I n c o n t r a s t , t h e September 1984 t e s t showed a c c e p t a b l e l e v e l s i n t h e occupied houses

(x

= 0.075 ppm) b u t h i g h l e v e l s ( a v e r a g e

HCOH = 0.18 and 0.21 ppm) i n t h e two unoccupied houses v h e r e windows were n o t opened. These d a t a a r e c o n s i s t e n t w i t h t h e i n t u i t i v e o b s e r v a t i o n t h a t d u r i n g t h e c o l d weather monitoring p e r i o d t h e f u r n a c e was running f r e q u e n t l y and drawing i n f r e s h a i r . I n t h e summer, t h e f u r n a c e f a n s would n o t be o p e r a t i n g ; hence t h e primary s o u r c e of v e n t i l a t i o n would b e window openings. I n a d d i t i o n , t h e s t a c k e f f e c t i s reduced i n t h e summer.

These d a t a s u g g e s t t h a t w h i l e both systems ( p a s s i v e o r mechanical) can p r o v i d e adequate v e n t i l a t i o n f o r t h e c o n t r o l of indoor HCOH l e v e l s , p r o p e r l y maintained mechanical systems do n o t r e q u i r e d e l i b e r a t e occupant i n p u t and may, t h e r e f o r e , b e more r e l i a b l e . I n c a s e s where occupants of houses w i t h o u t mechanical v e n t i l a t i o n systems do n o t u s e window openings t o i n t r o d u c e p a s s i v e

v e n t i l a t i o n (such a s a i r - c o n d i t i o n e d h o u s e s ) , i n d o o r HCOH l e v e l s could become e x c e s s i v e .

During t h e w i n t e r ( T e s t 1) t h e Group A houses had a i r c i r c u l a t i o n r a t e s c o n t r o l l e d by t h e a i r flow of t h e HRV. When O N , t y p i c a l HRV flow r a t e s were ~ 0 . 7 ach; however, ONIOFF c o n t r o l reduced t h e time-averaged r a t e s ( s e e T a b l e s 2 and 3). The absence of a supply a i r ductwork system f u r t h e r reduced t h e complete c i r c u l a t i o n of t h e a v a i l a b l e v e n t i l a t i o n a i r . The f u r n a c e f a n s i n t h e Group B houses had c i r c u l a t i o n c a p a c i t i e s of between 2.6 and 3.0 ach when

ON.

I n t h e Group A houses ( T e s t l ) , 1 7 o u t of 22 had bedroom l e v e l s h i g h e r t h a n l i v i n g room l e v e l s (Fig. 3a). I n c o n t r a s t , only one of t h e f i v e Group B houses (Fig. 3b) had a bedroom l e v e l h i g h e r t h a n t h e l i v i n g room l e v e l .

During t h e summer (Test 2 ) when window openings were e x t e n s i v e l y used by a l l of t h e house groups, t h e Group A houses had 11 o u t of

24 c a s e s where t h e bedroom l e v e l was h i g h e r t h a n t h a t of t h e l i v i n g room (Fig. 312). S i m i l a r l y , f o u r o u t of seven of t h e Group 2 houses had e l e v a t e d bedroom l e v e l s (Fig. 3d).

Although t h e p o l l u t a n t l e v e l i n a s p a c e i s a f u n c t i o n of t h e s o u r c e s t r e n g t h and t h e a i r exchange r a t e , s i m i l a r i t i e s i n

c o n s t r u c t i o n m a t e r i a l s and occupancy l o a d i n g s s u g g e s t t h a t d u r i n g t h e w i n t e r , poor a i r c i r c u l a t i o n i n t h e Group A houses may be r e s p o n s i b l e f o r t h e e l e v a t e d bedroom l e v e l s . During t h e summer, window openings i n c r e a s e d t h e d i s t r i b u t i o n of t h e v e n t i l a t i o n i n t h e Group A houses and t h e w i n t e r p a t t e r n of c o n s i s t e n t l y h i g h l e v e l s i n t h e bedrooms was e l i m i n a t e d .

It i s obvious from t h e s e d a t a t h a t d i f f i c u l t i e s i n a n a l y s i s a r i s e when a one-compartment model i s used f o r v e n t i l a t i o n and a

two-compartment model i s used f o r measurements. I n g e n e r a l , however, uniform p o l l u t a n t l e v e l s throughout a house would be expected i f t h e a i r c i r c u l a t i o n r a t e were r e l a t i v e l y h i g h , a s i n

t h e c a s e of window openings o r f u r n a c e f a n o p e r a t i o n . Conversely, i n a r e a s w i t h uneven v e n t i l a t i o n r a t e s , s t r a t i f i e d l e v e l s of

p o l l u t a n t s s h o u l d e x i s t . 7. Conclusions

Although f i r m c o n c l u s i o n s cannot be drawn from t h i s s m a l l d a t a s e t , a number of o b s e r v a t i o n s can be made:

-

t h e only a v e r a g e HCOH l e v e l s s u b s t a n t i a l l y above 0.1 ppm were

observed i n unoccupied p a s s i v e l y v e n t i l a t e d houses (Group B). This s u g g e s t s t h a t t h e mechanical v e n t i l a t i o n systems used i n t h e Group A houses were p r o v i d i n g r e l i a b l e indoor HCOH c o n t r o l . F u r t h e r , s i n c e n a t u r a l i n f i l t r a t i o n f o r c e s are minimal i n

summer, d e l i b e r a t e window openings a r e r e q u i r e d t o p r o v i d e adequate v e n t i l a t i o n i n p a s s i v e l y v e n t i l a t e d houses.

-

houses w i t h low a i r c i r c u l a t i o n r a t e s can have s i g n i f i c a n t i n t e r i o r v a r i a t i o n s i n p o l l u t a n t c o n c e n t r a t i o n s . For t h e group A houses, 77% of t h e houses had bedroom HCOH l e v e l s h i g h e r t h a n t h o s e i n t h e l i v i n g room.

8. References 1. FIGLEY, D.A.

"The R e l a t i o n s h i p Between Indoor A i r Formaldehyde

C o n c e n t r a t i o n s and V e n t i l a t i o n Rates For a Group of S i x t e e n New Houses", Accepted f o r P u b l i c a t i o n , APCA 7 8 t h Annual Meeting, D e t r o i t , M I , June 1985.

2. ORR, H.W.

"Design and C o n s t r u c t i o n of Low Energy Houses I n

Saskatchewan", Building P r a c t i c e Note No.

30,

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 of Canada, Ottawa, 1982.

3. ORR, H.W. and FIGLEY, D.A.

"An Exhaust Fan Apparatus f o r Assessing t h e A i r Leakage C h a r a c t e r i s t i c s of Houses", B u i l d i n g Research Note No. 156, 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 of Canada, Ottawa, 1980.

4. "Monthly M e t e o r o l o g i c a l Summary"

Atmospheric Environment S e r v i c e , Environment Canada, 1983-1984.

5. SHAW, C.Y.

"A C o r r e l a t i o n Between A i r I n f i l t r a t i o n and 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.

-

87 p a r t 2, 1981, pp. 333-341.

6 . " V e n t i l a t i o n f o r Acceptable Indoor Air Q u a l i t y " ASHRAE 62-1981, A t l a n t a , GAS 1981.

T h i s p a p e r i s b e i n g d i s t r i b u t e d i n r e p r i n t f o r m by t h e I n s t i t u t e f o r R e s e a r c h i n C o n s t r u c t i o n . A List of b u i l d i n g p r a c t i c e and r e s e a r c h p u b l i c a t i o n s a v a i l a b l e from t h e I n s t i t u t e may be o b t a i n e d by w r i t i n g t o t h e ~ u b l i c a t i b n s S e c t i o n , I n s t i t u t e f o r R e s e a r c h i n C o n s t r u c t i o n , N a t i o n a l Research C o u n c i l o f C a n a d a , O t t a w a , O n t a r i o , K 1 A

0R6.

Ce document e s t d i s t r i b u 6 s o u s forme d e t i r e - a - p a r t p a r L ' I n s t i t u t de r e c h e r c h e e n c o n s t r u c t i o n . On p e u t o b t e n i r une l i s t e d e s p u b l i c a t i o n s d e 1 ' I n s t i t u t p o r t a n t s u r l e s t e c h n i q u e s ou l e s r e c h e r c h e s e n matiere d e b a t i m e n t e n d c r i v a n t

B

l a S e c t i o n d e s p u b l i c a t i o n s , I n s t i t u t d e r e c h e r c h e en c o n s t r u c t i o n , C o n s e i l n a t i o n a l d e r e c h e r c h e s du Canada, Ottawa ( O n t a r i o ) , K I A OR6.