Malya ABDELOUHABa,b, Bernard Collignan , Francis Allard Abdelouhab_CSTB.pdf · Malya ABDELOUHABa,b,...

Malya ABDELOUHABa,b, Bernard Collignana, Francis Allardb

16-19 March, 2010 | INTERSOL2010: 9th International Conference-Exhibition on Solils

Sediments and Water, Paris. PAGE 1

Passive Sub-slab Depressurization System in

building, against volatile soil contaminants

a: CSTB- Centre Scientifique et Technique du Bâtiment- FRANCE

b: LEPTIAB- Université de La Rochelle - FRANCE

16-19 March, 2010 | INTERSOL2010: 9th International Conference-Exhibition on Soils

Sediments and Water- Paris |

Plan

Introduction

Presentation of experimental dwelling

Study of Passive S.D.S.

Protocol

Results and discussions

Conclusion

PAGE 2



Introduction (1/3)

PAGE 3

2

3

1

2

3

44

cracks

joints between walls

pipeline networks

Convection

Diffusion

34

12

1

Underground sources: contaminatedsoil or groundwaterSource CSTB

P+

P- P+

Tout<Tin

Vadose zone

Chemical vapor migration

walls

How to prevent the building against entry of the volatile soil contaminants ?



Introduction (2/3)Active S.D.S.

PAGE 4

Well know technology for more than twenty years in radon building protection

Fan

Depressurized zone

Active S.D.S. is one of the most effective methods of lowering volatile soil contaminants levels

P -

P- -

P +



Introduction (3/3)Passive S.D.S.

PAGE 5

Thermal buoyancy + wind effect Passive S.D.S.

Ability and efficiency of Passive S.D.S. to maintain the depressurization of the basement : one year follow-up

To study hybrid solutions for basement depressurization using a stato-mechanical extractor

Fan

Depressurized zone

Wind

Tout< Tin

P-

P+

P- -



Presentation of experimental dwelling (1/3)

PAGE 6

MARIA: Mechanized house for Advanced Research on Indoor Air

To study relations between ventilation and indoor air in housing sector

Preliminary experiments



Presentation of experimental dwelling (2/3) Installation of S.D.S.

PAGE 7

Installing S.D.S. during the construction 10 holes managed through concrete slab to

measure pressure

Gravel

Slab

Memebrane

Sumps

10 holes drilled through the concrete slab to measure pressure



Presentation of experimental dwelling (3/3) Characterisation of basement permeability

PAGE 8

P

PFan

Inhabited volume

Preliminary experiments

10

100

10 100

Basement exhaust flow (m3/h)

Basement depressurisation (Pa)

hole1 hole2

hole3 hole4

hole5 hole6

hole7 hole8

hole9 hole10



Study of passive S.D.S. (1/9)Adaptation of basement

PAGE 9

Preparation of basement : need to install a new sump with 200 diameter



Study of passive S.D.S. (2/9) Experimental protocol

PAGE 10

- Wind (velocity and direction)- External temperature

- Internal temperature

- Duct air velocity- Duct temperature

Basementdepressurisation:

P

Basic extractor

Stato-mechanical extractor



Study of passive S.D.S. (3/9)Monthly Results

Figure 1: Evolution of basement extract flow and basement depressurization during time

High variability of running during a day natural forces highly variables

Flow rate rises the depression of the basement also rises

0

5

10

15

20

25

30

0

10

20

30

40

50

60

5/3 10/3 15/3 20/3 25/3 30/3

Pam3/h basement extract flow basement depressurisation



Study of passive S.D.S. (4/9)

Monthly Results

Figure 2: Comparison of basement extract flow function of basement depressurization for natural and mechanical extraction

The difference of the slopes is due of the Installation of the centred sump

Basement depressurization is

always homogenous

1

10

100

0 1 10 100

Q (m3/h)

DP (Pa)

Natural extraction Mechanical extraction



Study of passive S.D.S. (5/9)Annual Results

Figure 3: Monthly averaged temperature difference between air duct and external air and monthly averaged wind force along year

Thermal and wind forces induce the extracted air flow rate from the basement.

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

0

2

4

6

8

10

12

14

j a s o n d j f m a m j

m/s°C

Monthly averaged (Tduct-Text)

Monthly averaged wind force



Study of passive S.D.S. (6/9)Annual Results

Figure 4: Percentage of running time of the system along year above three thresholds

Significant percentage of running along year and mainly during winter season

Efficiency is better from March installation of static extractor

0

10

20

30

40

50

60

70

80

90

100

j a s o n d j f m a m j

% Qextr. > 13,5 m3/h (1 Pa)

Qextr. > 19 m3/h (2 Pa)

Qextr. > 23 m3/h (3 Pa)

Installing static extractor



Study of passive S.D.S. (7/9) Effect of static extractor

Figure 5 : Comparison of extract flow from basement function of wind velocity for system with static extractor and with basic extractor (temperature difference < 4°C)

y = 0,96x1,99

y = 0,44x2,07

0

5

10

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6 7 8

m3/h

m/s

with static extractor with basic extractor

power law (with static extractor) power law (with basic extractor)

Relative dispersion of experimental points obstacles around a dwelling (trees, other buildings)

Extract flow with static extractor is around twice the value of extract flow with basic extractor




Effect of the mechanical operation of the extractor

PAGE 16

Gravel

Slab

Memebrane

Sumps

10 holes drilled through the concrete slab to measure pressure

Hybrid solutions

Fan on

Maximum power (20- 25 W) 03/06/2008 at 1pm30

Medium power (10- 15 W) 06/06/2008 at 1pm30

Minimum power (2- 4W) 09/06/2008 at 1pm30

Mechanical operation of the extractor for three regimes




Effect of the mechanical operation of the extractor

Figure 6 : Time evolution of wind force, temperature difference between the air duct and the outside and airflow extracted from the basement for three regimes of

mechanical operation of the extractor (Maximum, Medium, and Minimum)

Natural forces are negligible the mechanical running ensures a flow of minimum extraction

0

5

10

15

20

25

30

35

40

45

50

-6

-4

-2

0

2

4

6

8

10

12

3/6 4/6 5/6 6/6 7/6 8/6 9/6 10/6 11/6 12/6 13/6 14/6

m3/h°C m/s Wind force (Tgaine-Text) Extracted flow

P minP max P med



Conclusion

The natural running of S.D.S. is highly variable along the year but percentage of running time could be significant and mainly during winter season

Using two different extractors: a basic one and other with shape optimised to benefit of the impact of wind on extraction flow ‘static extractor’

Natural forces are insufficient use of an optional mechanical operation of the static extractor can generate a minimum rate of extraction

Advantage of passive S.D.S.: Protect the building against volatile soil contaminants

This system is a low cost of operation and it requires low maintenance

PAGE 18



Thank you for your attention

PAGE 19

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