A Field Study of Full Height Passive Radon Stack in the ... · Radon Reduction Methods 2 (EPA Consumer’s Guide to Radon Reduction, 2016) •Active sub-slab depressurization 50-99%

A Field Study of Full Height Passive Radon

Stack in the National Capital Region of

Canada

Prepared by: Dr. Liang Grace Zhou, Ethan Li, Gang Nong, and Jeff Whyte

National Research Council Canada - Construction Research Centre

For: the 14th International Workshop on the Geological Aspects of Radon Risk

Mapping

February 7, 2019

Radon Reduction Methods

2

(EPA Consumer’s Guide to Radon Reduction, 2016)

• Active sub-slab depressurization 50-99%

• Passive sub-slab depressurization 30-70%

Maybe more efficient in cold climates• Sub-membrane depressurization 50-99%

• Sealing radon entry routes Variable

• Sump-hole suction 50-99%

• Drain tile suction 50-99%

• Basement pressurization 50-99%

• Heat recovery ventilation Variable

3

2014 British Columbia Provincial Building Code

Radon Pipe Changes

(Illustration courtesy of BC Office of Housing and Construction Standards)

In 2015, several change requests submitted to

National Building Code (NBC) Standing

Committee on Housing and Small Buildings.

Installation of a radon vent pipe which extends

through, and terminates outside, the building in

Radon Area 1.

Passive Radon Stack Radon Reduction Effectiveness

Canadian Centre for Housing Technology Passive stack 56 Bq/m3No stack 85 Bq/m3

Passive Stack Radon Reduction: 35%

R14 insulation in attic to avoid ice blockage

Passive Stack:

Insulation in Unheated Space

5

R7 in unheated attic and R14 above rooflineCanadian General Standards Board Radon Control

Options for New (149.11) and Existing (149.12)

Buildings

Computational Fluid Dynamics Simulation Using COMSOL Multiphysics

Outdoor T: -25 °C and -30 °C

Attic T: -13 °C and -17 °C

Stack Inlet T: 18 °C

Stack Inlet RH: 50% and 100%

Stack Air Speed: 0.05 m/s, 0.1 m/s and 0.15 m/s

Above Roof Wind Speed: 21.5 km/h

6

Full Height Passive Radon Stack:

A Field Study in the National Capital Region

Why:

• Mid-term radon monitoring to minimize bias;

• A wide range of measurement parameters to understand system performance;

• Address National Building Code change requests;

• Develop practice guide.

How:

• 5 homes in Ottawa-Gatineau;

• House characteristics survey questionnaires;

• Blower door test before and after stack installation for air tightness;

• Tracer gas decay test before stack installation for natural air exchange rate;

• >30 day stack open, >30 day stack closed in the fall of 2017;

• >30 day stack open, >30 day stack closed in the winter of 2018;

• Measurements: radon concentration (indoor, soil, and stack); sub-slab pressure;

P/T/RH at the base and the exit of the stack; flow rate and air speed in the stack.

Special thanks to:

MB Radon Solutions for the stack installation and sub-slab communication testing

Jonathan Ham Energy Consulting for the blower door testing and locating leaking points

7


House Characteristics Questionnaire

• 4 single homes and 1 townhome were recruited;

• All homeowners understood what radon is and the associated health risk;

• The highest level of education in all 5 households was university level or

higher;

• 1 home was located on a 2 acre property with minimal obstructions, and

the other homes were located in areas of moderate housing density;

• 4 homes were 2 storeys with a basement, and1 home was a bungalow

with a basement;

• All 5 homes had forced air furnaces and air conditioning systems. Only 1

home had a Heat Recovery Ventilator (HRV);

• Only 1 home had a smoker.

8


Tracer Gas Decay Tests and Natural Air Exchange Rate

Home ID

Square footage

excluding the

basement (ft2)

Air Changes per Hour (ACH)

1 2000 0.071

2 1400 0.493

3 2100 0.046

4 2000 0.096

5 2950 0.101

y = 3.5933e-0.493x

R² = 0.9723

0

0.5

1

1.5

2

2.5

3

3.5

0 1 2 3 4

SF6

co

nce

ntr

atio

n (

pp

m)

Elapsed time (hour)

Home 2 SF6 Decay

y = 0.5675e-0.046x

R² = 0.8874

0

0.1

0.2

0.3

0.4

0.5

0.6

0 1 2 3 4 5 6

SF6

co

nce

ntr

atio

n (

pp

m)

Elapsed time (hour)

Home 3 SF6 Decay

9


Blower Door Test and Sealing Radon Entry Points

10


Radon in Soil Gas Sampling

• Saphymo soil gas probe

• AlphaGUARD PQ2000

PRO radon monitor

• AlphaPUMP

• Saphymo Multisensor Unit

• Vapor Pin™ KitHome ID

Number of

sampling

locations

Average

sampling depth

(m)

Soil radon

concentration

(Bq/m3)

1 20.50 36100

0.50 58200

2 1 Sub-slab area* 22560

3 6

0.81 15690

0.65 22512

0.51 11780

0.50 11470

0.60 12320

0.50 19240

4 5

0.93 18740

1.00 21550

0.77 36120

0.80 28590

0.75 34650

5 1 0.50 57050

• Difficult to drill 0.8-1.0 m

deep into the ground

• Difficult to obtain sufficient

soil gas flow due to high

back pressure in the

compact soil

• Radon concentration in

soil varies greatly over

small distances

11


Communication Test and Stack Insulation

Sub-slab Pressure Communication Testing is critical! No stack installed in Home 5

due to unsuccessful sub-slab pressure communication testing

R7 in unheated attic and R14 above roofline

12

Home 1 Home 2 Home 3 Home 4


Stack Configuration

13

Results from Home 1 Closed stack: 150 Bq/m3 Open stack: 110 Bq/m3 (Reduction 36%)

Before

sealing

radon entry

points: 310

Bq/m3

Stack height = 23 ft

Flow rate = 2.4 cfm

14


Before

sealing

radon

entry

points:

200 Bq/m3


Flow rate = 11 cfm

15


Before

sealing

radon

entry

points:

196 Bq/m3


Flow rate = 12 cfm

16


Before

sealing

radon

entry

points:

161 Bq/m3

Stack height = 23.5 ft

Flow rate = 3.4 cfm

17

Full Height Passive Radon Stack Field Study:

Observations and Conclusions

• A monitoring period of 4 weeks for each testing scenario is required to capture

passive radon stack performance;

• Under the test conditions, the 4 passive radon stacks reduced the indoor

radon concentrations by 36%, 92%, 81%, and 51%;

• Height of passive radon stack is critical (>25 ft to achieve >50% reduction);

• Blower door testing plus a smoke pencil can pin point the radon entry points;

• Sealing radon entry points effectively may contribute significantly to radon

reduction;

• Insulation of the portion of stack passing unheated space may enhance the

stack effect and radon reduction;

• Radon mitigation requires specific knowledge and skills as well as good

practice;

•Tracer gas decay test demonstrated Home 1 had <0.1ACH; a HRV and

increased ventilation rate may be a radon solution;

• Soil gas radon levels can vary within a very short distance and thus sampling

radon from soil provides limited extra value.

18

Future Work: 2018 and Beyond

Phase II of field study of full size passive radon stack in BC (15 homes):

• House characteristics questionnaire;

• Conduct blower door testing prior to open/closed stack testing;

• >30 day stack open, >30 day stack closed in the fall of 2018

• >30 day stack open, >30 day stack closed in the winter of 2019

• Measurements: radon concentration (indoor and stack); sub-slab pressure;

P/T/RH at the base and the exit of the stack; air speed in the stack.

A field study of HRV for indoor radon control in airtight houses with moderate

radon levels

1919

Thank you

Liang Grace Zhou

Senior Research Officer

613-990-1220

[email protected]

www.nrc-cnrc.gc.ca

November is Radon Action Month in Canada!

http://www.nrc-cnrc.gc.ca/

20

Outreach

• “Radon in Canadian Buildings”, Building Owners and Managers Association of Ottawa,

2012

• “Radon Mitigation NRC’s Indoor Air Strategies and Solutions,” for Association of

Municipalities of Ontario, 2013

• “Impact of Radon ASD System on Re-entrainment, Energy Use, and Indoor

Environment”, Construct Canada Expo, Toronto, 2013

• “New Research for Healthier Homes,” Better Builder Magazine, 2014

• Canadian Home Builders’ Association Housing Research Summary 2013–2015

• Host a stakeholder consultation workshop in 2012

• “NRC helps integrate radon technology into the building code”, Canadian Association of

Radon Scientists and Technologists, Vancouver, 2015

• “Experimental Study Of Heating Energy Use And Indoor Environment During Operation

Of Active Soil Depressurization Radon Mitigation System”, Indoor Air Conference,

Belgium, 2016

• “NRC and Radon Control Technologies”, Federal Provincial Territorial Radiation

Protection Committee 2016

• “NRC and Radon Control Technologies”, CHBA TRC Forum 2016

• “Combatting Radon with Scientific Research”, Construct Canada Magazine in 2017

• Media launch of National Radon Action Month 2017

21

Home ID Test Scenario ACH @50 Pa ELA (sq.in.)

1

Before stall

installation5.17 179.8

After stack


2

Before stall


After stack


3

Before stall


After stack


4

Before stall


After stack


5

Before stall


After stack

installation

(No stack installed)

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Documents

A Field Study of Full Height Passive Radon Stack in the ... · Radon Reduction Methods 2 (EPA Consumer’s Guide to Radon Reduction, 2016) •Active sub-slab depressurization 50-99%