1

Potential impacts ofPotential impacts of ductwork and envelope

leakage

Rémi Carrié and Peter Wouters

TightVent Webinar

Airtightness and ventilation perspectives in Romania

21 June 2011

Presentation outline

Ductwork leakage Good and bad examples

Typical leakage rates

P t ti l i li ti Potential implications

Envelope leakage How does it work?

Possible airflow rate impacts

Conclusions

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Ductwork leakage

Ductwork can look like this

3

It can also look like that

Ductwork leakage classes

Leakage classes are defined in EN 12237

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Field observations

80%

90%

100%

France

Belgium

1 3 9 27 81 2430.3

20%

30%

40%

50%

60%

70%

Occ

urr

ence

g

Sweden

Belgium and France:15% to 25% of ventilation flow rate

was leaking away(1999)

Sweden

0%

10%

Cla

ss D

Cla

ss C

Cla

ss B

Cla

ss A

3*C

lass

A

9*C

lass

A

27*C

lass

A

Plu

s

Duct leakage data from the SAVE-DUCT project (Carrié and collaborators, 1999). 21 systems tested in Belgium, 21 in France, 69 in Sweden.

Why bother ?

Fan flow is not adjusted to compensate leakage air flow rate

Fan flow is adjusted to obtain

t i fl tair flow rate correct air flow at terminals

No increased energy losses

Bad indoor air quality

Energy losses by:

increased ventilation load

increased fan power demand

5

90%

100% Nominal efficiency Duct resistance: 5 m2 K / W

Results on one test case

From 80% down to 43% !

30%

40%

50%

60%

70%

80% Duct resistance: 1,2 m2 K / Wto 43% !

+ increased fan energy use+ increased

ventilation load

0%

10%

20%

30%

Class C Class A 3*Class A

SE system with ducts located in unconditioned spaces. Reference : Proceedings of the BUILDAIR 2011 symposium, auhtors: Carrié and Leprince

Envelope leakage

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Envelope leakage

How does it work ?Wind and stack effect increase the total ventilation airflow rate

If there is a HR system, it may be short circuited

+ —

Envelope leakage

How does it work ? Disturbance of flow patterns

BUILD TIGHT, VENTILATE RIGHT !

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Background

Airtightness can be characterized with leakage flow rate at 50 Pa divided by the building’s volume (not the only indicatorused in practice) :

n50 =Airflow rate at 50 Pa

Heated volumeUnits : 1/h

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Airflow rate impacts

Typical values of infiltration airflow rate, ninf

2050

inf

nn

• Rule of thumb, see Drubul, 1988; Kronval, 1978.

Rough approximation however useful to see orders of magnitudes

*n50

30n50

10

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Air change rate (1/h)

Assumed airtightness (n50,

1/h)Infiltration

airflow rate (1/h)

Infiltration airflow rate divided by air change rate (%)

0,5 3 0,15 30%0,6 3 0,15 25%0,7 3 0,15 21%0,8 3 0,15 19%

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Typical n50 values ?

90%

100%

PassivHaus

Réf. RT 2005 - MaisonsV/A = 1.4 m

30%

40%

50%

60%

70%

80%

réq

ue

nc

e c

um

ulé

e (

%)

Réf. RT 2005 - Collectif, etc.V/A = 2.3 m

Réf. RT 2005 - AutresV/A = 2 5 m

0%

10%

20%

30%

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0Perméabilité à 50 Pa (Vol/h)

Fr

Maisons individuelles - 215 opérations

Collectif, bureaux, hôtels, étbt. enseignement ou sanitaire - 23 opérations

Industries, salles polyvalentes ou de sport, etc. - 25 opérations

V/A = 2.5 m

Source : Extraction de la base de données du CETE de Lyon - Juillet 2006

MININFIL project

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MININFIL project

Large effort initiated by (CETE de Lyon) to help designers and workers, both on the methodology and on the technical solutions

MININFIL project

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Conclusions

The significance of envelope and ductwork leakage on energy use and ventilation system efficiency has been demonstrated in the pastefficiency has been demonstrated in the past

Their potential impact implies specific attention in the context of nearly zero-energy buildings

There is obviously room for improvement:Probably in most countries outside Scandinavia for

ductwork systemsductwork systems

Probably in ALL countries for envelope airtightness

There is a range of technical solutions available to overcome these problems