Air quality measurements in low-leakage houses

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Air quality measurements in low-leakage houses

ISSN

0701-5232

S e r

TH1

- , ,I ,

...

*- , .

AIR QUALITY pfEASlJREMENTS

IN LOW-LEAKAGE HOUSES

by

R

.

S

.

X)umon t

A N A

LYZED

Division of B u i l d i n g Research, National Research Council of Canada

AIR

QUALITY

MEASUREMENTS IN LOW-LEAKAGE

HOUSES

by

R.S.

Dumont

Abstract

R e s u l t s of air qua11 t y measurements are presented for a group of

low-leakage hauses located in Saskatoon, Saskatchewan. A total of 4 6 houses were tested for formaldehyde, n i t r o g e n d l o x i d e , xadon, and humidity l e v e l s .

The median l e v e l of formaldehyde was 0.09 ppm, slightly lower than t h e

guidel-lne of 0.1 ppm. Elevated levels of formaldehyde

C

Xl.1 ppm) were found

in 18 of 46 houses. The median

l e v e l

of radon was 3.0 p i c o c u r i e s t ' l i t r e ,

s l i g h t l y lower than t h e g u i d e l i n e

of

4 p C i / ~ . Elevated l e v e l s o f radon ( 2 4 p ~ i / ~ ) were found in 1 2 o u t of 4 4 houses. The median level of nitrogen

dioxide was 4 . 6 ppb, c o n s i d e r a b l y lower than the g u i d e l i n e of 50 ppb, No houses were found with elevated nitrogen dioxide l e v e l s (250 ppb).

In recent years, a large number of houses have been constructed i n the

Canadian prairie r e g i a n that have been sealed to a considerably h i g h e r

degree t h a n conventional housing. A

1981

report by Dumont and

Orr

l includes

pressure t e s t values f o r a group of 40 houses that were specially sealed.

On average, these houses had equivalent leakage area valves that were 53% o f

those in conventional houses. (See T a b l e 1).

As part of an ongoing research p r o j e c t , testing was done on t h e levels of s e l e c t e d p o l l u t a n t s in a group of t h e s e low-leakage houses.

A number of g u i d e l i n e s exist for a i r p o l l u t a n t levels. A frequently

q u o t e d standard is t h e document " V e n t i l a t i o n f a r Acceptable M r Quality"

produced by the American S o c i e t y of

Heating,

Refrigerating, and hir

Conditioning Engineers (ASHRAE)

.

Values f o r f ormaldehye

,

radon daughters, and nitrogen

dioxide

are presented in Table 2.

ZR I982 a preliminary air q u a l i t y survey of 5 1 houses i n t h e Saskatoon area was undertaken to determine l e v e l s of formaldehyde and radon daughters.

The

survey included houses of varying ages and airtightness levels.

As shown in Figure I , a number of the houses exhibited higher l e v e l s of

f armaldehyde gas. Using the ASHRAE criterion o f

0.1

ppm, 8 of the

5

1

Saskataon houses had elevated formaldehyde gas

levels,

Of p a r t i c u l a r

interest f n this i n i t i a l survey was t h e r e l a t i o n s h i p b e t w e n formaldehyde

levels and the a i r t i g h t n e s s of t h e structure. F i g u r e 2 p r e s e n t s the

r e l a t i o n s h i p between formaldehyde l e v e l s and t h e pressure t e s t reading for each house.

It

shows that houses with higher formaldehyde readings were generally among t h e more airtight of the sample. (It should b e n o t e d t h a t

t h e airtightness of the structure is n o t a d i r e c t measure of t h e air change

systems. These systems can

substantially

i n c r e a s e t h e amount of ventilation compared t o n a t u r a l veatilatBon from s t a c k and wfnd e f f e c t s . )

In t h e 1982 survey, radon d a u g h t e r l e v e l s were a l s o measured using t h e

Terradex Track-Edge Detector. The results are p r e s e n t e d in Figure 3. Using

the

ASHRAE

l e v e l of 0.01 working levels as a cut o f f , 17 of 4 3 houses* had

elevated radon daughter l e v e l s . A p l o t of the radon daughter l e v e l s as a

f u n c t i o n of t h e pressure t e s t readings f o r the houses is presented in

F i g u r e 4 .

1983 Study of S a s h - Houses

As a follow-up to the 1982 study, a survey of formaldehyde, nitrogen d i o x i d e and radon gas l e v e l s was conducted in 1983 in a sample of 46 hauses

in

Saskatoon. The houses chosen had all been built s i n c e 1978, and were

chosen because they had a pressure test reading of less than 2.5 a i r changes p e r hour at 50 pascals. The average pressure test reading f o r the 4 6 houses was f - 3 3 a i r changes p e r hour at 50 pascals.

This i s considerably

t i g h t e r

than the value of 3.6 air changes per hour at 50 pascals which w a s reported l

as an average f o r conventional h o u s e s b u i l t during the p e r i o d 1960-1980 in

Saskatoon.

For steady s t a t e c o n d i t i o n s , t h e concentration o f a pollutant w i t h i n a

well-mixed space may be expressed as:

where

C,

= c o n c e n t r a t i o n of pollutant w i t h i n t h e space (mass/volwme)

C,

= c o n c e n t r a t i o n of p o l l u t a n t at t h e s o u r c e of t h e v e n t i l a t i o n air, i.e.

,

o u t s i d e air (mass/volme)

N

= n e t p o l l u t a n t generation rate within the space (mass!time)

V

= volume rate of a i r exchange (volume/time)

A high concentration of p o l l u t a n t w i t h i n t h e s p a c e may be experrenced

under any or a l l

of

three conditions:

8 high outdoor concentration

(c,)

C high pollution generation rate

(N)

a

low

ventilation rate

(v)

*

Due t o equipment f a i l u r e e t c .

,

n o t

all

of the t e s t s

were

successfully

completed.

For

instance,

in

this case, although 5 1 t e s t s were conducted,

only 4 3 were successful. Throughout t h i s paper, reference is made only t o

T e s t Procedure for Air Quality Heasxtrememts in the 1983 Study

1.

Formaldehvde

Formaldehyde t e s t s were made in t h e houses using Ihpont Pro-tek passive

badges- A t o t a l af

2

badges, each of whf ch was exposed f o r o n e w e e k

p e r i o d s , were placed in the l i v i n g areas {generally the dining or l i v i n g

roams) of each house. The badges were analyzed in a laboratory in Toronto. The measurements were taken from January

3

t o January 21, 1983. W r i n g this

t i m e , t h e average outdoor temperature was -1 1°6, and t h e average w i n d speed was 13 km/h. The results of the t e s t s f o r the houses are p r e s e n t e d in

Table 3.

2. Radon Gas Tests

Radon gas l e v e l tests in the houses were made using Tesradex Rack Etch

passive detectors. The p a r t i c u l a r detector chosen has a f i l t e r w h i c h

m i n i m i z e s the contact of dust particles with the detector; hence o n l y the

r a d o n gas and n o t the radon d a u g h t e r concentration is measured.

Measurements w e r e made from January t o A p s l l 1983. Results are presented in

T a b l e 3.

Appendix A presents a discussion on the consistency of t h e formaldehyde and radon sensor readings.

3. Nitrogen Dioxide Tests

Nitrogen dioxide t e s t s , one p e r house, were made during a

week

in early

January using a passive detector. The test badges were processed by H e a l t h and Welfare Canada. Results are presented in Table

3.

In a d d i t i o n t o these three t e s t s , data were gathered

for

each house, as follows:

a Pressure t e s t result at a pressure d i f f e r e n c e of 50 Pa.

Type of heating system

a Type of ventilation system used

a. None

b . Fresh air d u c t i n t o plenum c. Air-to-air heat exchanger

o Type of air-to-air heat exchanger

Number of occupants during day and n i g h t p e r i o d s

a I n s i d e temperature and relatjve humidity d u r i n g formaldehyde t e s t s

o Area of p a r t i c l e board

+

Number of wood heating appliances (wood stoves ox fireplaces w Number of cigarette or c i g a r smokers.

These data are contained

in

Table 3.

Test Results

1 . The formaldehyde levels for each house are presented in Figure 5, The values shown are the average sf t h e t w o readings t a k e n . The median

greater t h a n 0.1 ppm. A p l o t of formaldehyde levels as a function of

i n d o o r r e l a t i v e humid1 t y is shown in F i g u r e 6 . A p l o t of t h e

formaldehyde levels

as a function of t h e amount of p a r t i c l e board

fn

each house is shown in F i g u r e 7.

2. The results of the radon gas tests are sham in Figure 8 , Of the 4 3 houses successfully tested, 12 houses had radon gas levels t h a t exceeded 4 pfcocuriesjlitre, which is the

U.S

EPA remedial c r i t e r i o n . The

median value for t h e s e 4 3 houses was 3.0 p i c o c u r i e s / l i t r e .

3.

The

results of the n i t r o g e n dioxide t e s t s are shown in Figure 9. The

median level, f o r the 46 houses w a s 4.6 ppb, The houses were divrhded into four categories, depending on t h e presence or absence of wood applLances and smokers- The results were as follaws:

Category _{No 2} Number

P P ~ of Houses

No

wood a p p l i a n c e s , n o smokers

3.5

12 No wood appliances, smokers 5 -3 4

Wood appliances, no smokers 5.1 2 1

Wood appliances, smokers 5.6 9

Formaldehyde

The median formaldehyde

Level

was 0.09 pgsn, with values ranging

between 0.033 and 0.24 ppm. The houses w i t h higher formaldehyde r e a d i n g s tended to have higher relative humidifies. Of the 8 homes with relative

h u m i d i t y

(BH)

values less t h a n 302, none had f armaldehyde readings greater

t h a n 0.1 ppm. Of the 6 houses w i t h RH values greater than 40%, 2 had

formaldehyde readings greater than 0.1 ppm. A p l o t of t h e relationship

between formaldehyde and interior relative humidity is shown i n Figure 6. Assuming constant moisture generation rates in t h e various houses (on an equivalent volume b a s i s ) ,

low

relative humidity values are a r e s u l t of

higher air change rates. Thus t h e r e l a t i o n s h i p between formaldehyde and relative h m i d i t y is not unexpected. There is a secondary e f f e c t , s i n c e

the formaldehyde offgassing rate is known to

increase

w i t h higher

humidities

.

Higher formaldehyde readings were a l s o associated w i t h the houses t h a t

d i d not have a mechanical v e n t i l a t i o n system. F i f t y percent of the houses with no mechanical ventilation system showed formaldehyde levels greater

than 0.1 ppm, Only 27% of those t h a t had mechanical v e n t i l a t i o n showed

levels greater than 0.1 ppm.

As

part of t h e survey, measurements were made of t h e area of p a r t i c l e board contained w i t h i n each house. The areas of p a r t i c l e board are shown in

Table 3. The range of particle board areas varied from 0 to 31 1 m2. Tn a d d i t i o n , there were other formaldehydeemitting sources within t h e houses

(some carpets, permanent press f a b r i c s , hardwood plywoods) t h a t were not q u a n t i f i e d . A s shown i n Figure 7, there was weak p o s i t i v e correlation

(correlation coefficient =

0.36)

between the formaldehyde l e v e l and t h e

amount o f particle b o a r d Fn the houses. O t h e r f a c t o r s , such a s t h e

ventilation rate, the age

and

brand of the p a r t i c l e board, the type of covering on the p a r t i c l e board, t o b a c c o smoke and o t h e r sources of

formaldehyde

are p o s s i b l e

reasons

the c o r r e l a t i a n between the formaldehyde

level

and the amount of particle board is

not:

stronger.

A house

can

have a

low

formaldehyde reading by having either a low volume of f o r m a l d e h y d e e m i t t i n g sources or a high allr change rate. Due to u n a v a i l a b i l i t y of equipment, air change measurements were n o t made dusf ng

the period the formaldehyde readings were taken.

It

is possible to estimate

the a i r change rate of those houses that d i d not have f o r c e d v e n t f l a t i o n

systems by using the pressure t e s t data. shaw3 p r e s e n t e d a correlation

between the a i r change rate and t h e pressure test data, w i n d speed and o u t s L d e air temperature. The correlation equation when the w i n d speed i s

greater than 3.5 m/s and the temperature difference is greater than 25 K, i s

a s follows:

where

I

= air change rate (h-I)

C

= constant from pressure test (L/(s-pa") )

V

= volume of house (m3)

Values f a r

C, V,

and

I for

t h e houses in t h e survey lacking forced

ventilation systems are presented i n T a b l e 3 . As may be seen f r o m t h e

table, the calculated average i n f i l t r a t i o n rate f o r t h e s e houses was

0.23 a c l h , and t h e corresponding average f armaldehyde l e v e l was 0.1 06 ppm.

This relatively

low

air change rate, coupled with the h i g h p a r t i c l e

board loadlng for a number of the houses, is believed to be r e s p o n s i b l e f o r the elevated formaldehyde gas readings in this group of houses.

2. Radon

The median radon level f o r the h o u s e s w a s 3.0 p i c s c u r i e s l l i t r e , w i t h

the v a l u e s ranging between 0.82 and 9.44

pCi/L.

The r e a d i n g s w e r e a l l taken

in

the lowest levels of t h e houses, which were generally not o c c u p i e d .

2, Nitrogen Dioxide

The medEan value f o r the NO2 readings was 4.6 parts p e r b i l l i o n , w i t h

values ranging between 0.7 and 13.3 ppb, well, below t h e ASHEEAE g u i d e l i n e of

50

ppb. Three of the f o u r houses ~ 5 t h readings above 10 ppb had e i t h e r woad

s t o v e s or f i r e p l a c e s . The f o u r t h house, with a r e a d i n g above 10 ppb, had 2 smokers with cigarette consumption levels of 1 pack (20 cigarettes) each p e r d a y . The houses w i t h

no

wood appliances and n o smokers averaged 3.5 ppb, and those w i t h both wood a p p l i a n c e s and smokers averaged

5.6

ppb.

The results of t h i s study i n d i c a t e a number of areas for further work: Future studies of t h i s type should include direct measurements of the air change rates in the houses using tracer gas ar o t h e r a p p r o p r i a t e

means.

Remedial

work

on these houses e x h i b i t i n g higher

levels

of p o l l u t a n t s

s h o u l d be undertaken.

lnvestfgatfons should be undertaken ro determine t h e source sf t h e

radon g a s . An area t h a t is l i k e l y to be a s t r o n g source is the f l o o r

drain, through which radon can leak into t h e house via the weeping

tile system.

Offgassing rates for typical p a r t i c l e boards used in Canadian houses should

be

d e t e r m i n e d . A particular need exists for d a t a on the offgassing rate when t h e board has a floor covering. Also of

i n t e r e s t is the rate of offgassing a s a function of the age of the board, the board temperature, and t h e relative humidity.

Further studies should be undertaken on residences such as mobile

homes, that c o n t a i n large q u a n t i t i e s of p a r t i c l e board.

R e f

ereaces

1. Dumant, R.S. and

Orr,

H.W. "Airtightness Measurements of Detached Muses

in the Saskatoon Area," National Research Council of Canada, D i v i s i o n of Building Eksearch, B u i l d i n g Research Note 178, Ottawa, Ontario,

1981.

2. ASHRAE, "Ventilation for Acceptable Indoor Air W a l i t y " Standard 62-1981, 1791 T u l l i e C i r c l e N . E . , A t l a n t a , Georgia, 30329, 1981.

3. Shaw, C.Y., "A Correlation between Air I n f i l t r a t i o n and Air Tkghtness

for Houses in a Developed R e s i d e n t i a l Area," ASHRAE Transactions, V o l .

87,

Pt.2, 1981.

LIST O F TABLES

1. Comparison of

air

leakage characteristics

for

groups of Saskatoon houses.

2. Guidelines for selected air contaminants. 3.

Air

q u a l i t y data, 1983 Survey, Saskatoon

4 , Calculated a i r change rates f o r houses lacking forced v e n r i l a t i o n .

LIST OF

FIGURES Flgure

1

Figure 2 Figure 3 Figure 4 F i g u r e 5 Figure 6 F i g u r e 7 Figure 8 Figure

9

Formaldehyde

r e a d i n g s , 1982 s t u d y .

Formaldehyde readings a s a function of air t i g h t n e s s , 1982

study.

Radon readings, 1 9 8 2 s t u d y .

Radon readings as a function of air tightness, 1982 study. Formaldehyde r e a d i n g s , 1983 s t u d y .

Formaldehyde readings a s a function of indoor relative humidity, I983 s t u d y .

Formaldehyde readings as a function of the amount of p a r t i c l e board, 1983 study.

Radon readings, 1 9 8 3 study.

Table 1. Comparison of Air Leakage Characteristics f o r Groups of

Saskatoon Houses

TYPE k a k a g e

Air

chlh Number

Area at 50 Pa of Houses

m 2

ac J h Pre-1945

.I078

10.35 19 1946-1960

.O

709

4.55

20 1961-1980 .062 k 3

-57

97 S p e c i a l air- tight houses (1977-1980) -0330 1.49

40

Table 2. Guidelines far g e n e r a l l y acceptable l e v e l s of s e l e c t e d a i r contaminants

.

Con raminan t Level Reference

- - - - . . - - . - . - - - --

Formaldehyde 0.12 mg/m3 ASHME 62-1981

0.1 ppm at 25OC,

101.3

kPa

Radon 4 pCi/L U.

S.

EPA

Radon daughters 0.01 working levels

ASHRAE

62-1981

Nitrogen Dioxide 100 pg/m3 W.S. EPA

50 ppb at 25'C, 101.3 kPa

T a b l e 3.

Air

Quality

Da

La,

1983

S u r v e y , Saskatoon

Tightness

Fo

rmald. Fo rmald.

House

Year

ac /h Press. P P WPQnt p p Dupont

T a b l e 3 (cont'd)

House T o t a l P a r t i c l e

House Volume Board Area

/!

of # of Radon

Code ( m 3 )

(m2)

PP

Wood Appl Smokers @CI/L)

A2 A4

A5

B 1 2 I311 B13 B10 B15 B 1 4 B3 AA!J

B6

C8

D2 D3 FF5 D4 E4 FF6 3'8 P9 F1 G J

G4

H6

H7

H8 3 3 L l O

LL

1 6 3 M8

M9

P2

P5

P 4 R3

R8

S9 S 1 FF1

S8

T3

T4

W7

Y1

T a b l e 3 Ccont'd)

He at ing Number V e n t i l

UA

Heat

MA

Es

t Problems

House System of Sys t e r n Exchanger On Erne Moisture/

Code Type Chimneys TY

TY

pe Hrs. &lour?

A2

A4

AS

B12

BP

1 £313

B10

B 15 B 1 4

B3

AA9 B6 C8

D2

D 3 FF5 D4

E4

F

F6

F8

F 9

F1

G7

G4

H6 H7 H a 53

L90

L11 G 3 M 8 M9

P2

P5 P 4

R3

R8 S 9 S 1 FFI

S

8

T3

T4

W7

Yl

GAS 2 GAS 1

GAS

3 GAS 2 GAS 2

GAS

2 GAS 2 GAS 1 GAS 1 GAS 2 EL. BASE. 0

EL.

BASE.

1 GAS 1 GAS 2 GAS 1 GAS 2 GAS 2 GAS 2 GAS 2 GAS 2 GAS 2 GAS 3 HOT WATER 1

EL.

BASE. 2 GAS 1 GAS 3 GAS 2 GAS 2 GAS 2 GAS 2 GAS 2

GAS

1 GAS 2 BOILER 1

EL* FURNACE

0 GAS 2 GAS 3 GAS 2 GAS 2 EL. BASE. 1 GAS 2 GAS 2

GAS

2 GAS 2 GAS 1 GAS 2 A TO A A TO A A TO A FR. A I R DUCT

FR.

A I R

DUCT

NQNE A TO A A TO A NONE A TO A A TO A R

TO

A A t o k A

TO

A A

TO

A FRm

AIR DUCT

A TO A PR. A I R DUCT NONE FR. AIR DUCT FR.

AIR

DUCT NONE A TO A A

TO A

A TO A A TO A A TO A A

TO

A A TO

A

FR.

AIR

DUCT PR. A I R DUCT A TO A FR. AIR OUCT

FR.

AIR DUCT A TO A NONE A TO A A TP A A TO A A

TO

A A

TO

A

FR. AIR DUCT

A TF A A TO A A

TO

A A "110 A P & P

MITSUB

VAN

E E 200

---

---em-

----

MITSUB

P & P

---

P & P

PASS

SOLAR

P & P

VAN

EE

200 P & P

P & P

---

MITSUB +----

---

---

----dm

---

P C P

P & P

VAN

EE 200

VAN

EE 200 P h P OTHER VAN

EE

200 dm---

MITSUB

---

--dm-

VAN EE

200

---

PASS. SOLAR

VAN

EE 200

VAN

EE 200 P & P P & P OTHER

VAN

EE 200 DC2

PASS.

SOLAR YESJNO

N O

NO NO

YES /NO

NO

NOIYES

YES/NO NO

VESSNO

YES/NO

T a b l e 3 (cont'd)

Daytime Nightime In.Temp In.Ternp RelHurn & I l i u m

House Adul t s / Adults

/

Deg (C) h g

{a

Pe

s cen t: P e r c e n t

Code Children Children Week

I

Week 2 Week 1 Week 2

- - A2 A4

A5

B 1 2 B 1 1 B13 B 1 0

a1

5 B14 B3 kA9 B 6 C8 D2 D3

FF5

D4

E4

F F6

F8

F9 F 1 6 7 6 4 H 6 Hi' H 8 5 3

L

10 L11 G 3 M8 I49

P2

P5

P

4 R 3 R 8

s9

S1

FF1 S8

T3

T4

w7

Y

1

Table 4 . C a l c u l a t e d a i r change rates far houses l a c k i n g forced

ventilation

. - . -

Formaldehyde

House

C

n V

I

PPm

Code m3/ ( s-pa") (m3) A C J ~ 2 wk Average

Consistency of the Radm and Formaldehyde Seasore

During t h e

a i r

quality measurements, a number of cross-checks were made

with

the radon and formaldehyde sensors. These checks

were

p r i m a r i l y taken

ro

ensure that the companies supplying t h e sensors and d o i n g the analyses

w e r e providing consistent readings,

Radon

-

During the course of t h e experiment, groups of 5 s e n s o r s w e r e p l a c e d

side-by-side in t w o l o c a t i o n s , The f i r s t l o c a t i o n f o r the aide-by-side check was in a crawl s p a c e area t h a t was known t o have e l e v a t e d radon

l e v e l s , The results f o r the f i v e sensors, all of which were placed s i d e by

side,

were

as follows, when read at the 1.0 pCiJL-month s e n s i t i v i t y l e v e l .

Sensor

No.

Radon r e a d i n g IpCii'L)

5.40

-

Average = 5.59

A second check, again using 5 sensors placed s i d e - b y s i d e , was

performed in a well-venrflated l a b o r a t o r y . The results f o r t h i s comparison

are

shown below:

Sensor No. Radon reading (pCi /L)

Dl

00

-

0.17

Average = 0.18 S t d . Dev, = 0.06

Formaldehyde

A side-by-side check was performed on the DuPont sensors. A t o t a l of 4 sensors

were

placed s i d e b y - s i d e in one house f o r a one week period. The

Sensor no. Formaldehyde l e v e l (ppm)

0 -088

-

Average = 0.078

0

0 4.0 8.0 12.0 16.0

A I R TIGHTNESS nsO

,

A I R CHANGES / H R . AT 5 0 Pa

< 0 H E b t l H G TYPE -

A

B O ELECT RlClTY A D O NATURAL G A S - AGE OF HOUSE A PRE 1945

D

1946 -1960 0 1961-1900

-

0

n

0. Q

n o

n I 1 I I I I I Figure 2

0

HEATING

TYPE

A

E3

O

ELECTRICITY

A

0

NATURAL G A S

8

I

AGE

OF HOUSE

Li

PRE

1945

1946

-1960

0

1961

-

1980

0

8.

0

A

-"

('0

8

n

0

A

A

0 0

1

0

,

I

I

I

I

A I R

TIGHTNESS

n 5 0

.

A I R CHANGES/ HR. A T

5 0

Pa

Figure 4

0

.a5

.

I 0

.I5

.20

FORMALDEHYDE

R E A D I N G S , p p m

F i g u r e

5

RELAf I V E HUMIDITY, %

Figure 6

PART

l C t E BOARD

A R E A

/

HOUSE

VOLUME

,

m

- I

F i g u r e 7

M E A N

= 3.56

S.D.

= 2.14

MEDIAN

=

3.01

0

0

2.5

5 . 0

7.5

R A D O N ,

p i c o c u r i e s

litre

F i g u r e 8

0

5

10

NO2

L E V E L S ,

p p b

Figure 9