FAQs

What is building airtightness?

Building airtightness (also called envelope airtightness) can be defined as the resistance to inward or outward air leakage through unintentional leakage points or areas in the building envelope. This air leakage is driven by differential pressures across the building envelope due to the combined effects of stack, external wind and mechanical ventilation systems [1].

[1] G. Guyot, F. R. Carrié and P. Schild, “Project ASIEPI – Stimulation of good building and ductwork airtightness through EPBD,” 2010.

What is ductwork airtightness?

Ductwork airtightness can be defined as the resistance to inward or outward air leakage through the ductwork shell.

What is infiltration/exfiltration?

Infiltration/exfiltration is the uncontrolled inward/outward leakage of outdoor/indoor air through cracks, interstices and other unintentional openings of a building, caused by the pressure effects of the wind and/or the stack effect [1].

[1] M. Limb, “Technical note AIVC 36- Air Infiltration and Ventilation Glossary,” International Energy Agency energy conservation in buildings and community systems programme, 1992.

What is the energy impact of building and ductwork airtightness?

The implementation of the EPBD recast puts increasing pressure to achieve better building and ductwork airtightness since for most European climates and countries, good airtightness levels are necessary to achieve nearly zero-energy buildings. This has been shown in a number of studies with energy impacts of the order of 10 kWh per m2 of floor area per year for the heating needs in a moderately cold region (2 500 degree-days) and 0 to 5 kWh/m2/year for the ducts plus the additional fan energy use [1]. For more information see also the ASIEPI project technical report on building and ductwork airtightness as well as REHVA journals’ special issue on airtightness [2].

[1]G. Guyot, F. R. Carrié and P. Schild, “Project ASIEPI – Stimulation of good building and ductwork airtightness through EPBD,” 2010.

[2] R. Coxon, “Research into the effect of improving airtightness in a typical UK dwelling,” The REHVA European HVAC Journal-Special issue on airtightness, vol. 50, no. 1, pp. 24-27, 2013.

Is there experimental data showing the energy savings of good building airtightness?

Yes. The Building Research Establishment in the UK has recently published an experimental study showing energy savings achievable with improved airtightness [1,2].

[1] R. Coxon, “Research into the effect of improving airtightness in a typical UK dwelling,” The REHVA European HVAC Journal-Special issue on airtightness, vol. 50, no. 1, pp. 24-27, 2013.

[2] D. Butler and A. Perry, “Co-heating Tests on BRE Test Houses Before and After Remedial Air Sealing,” Building Research Establishment.

Is good building airtightness compatible with good indoor air quality?

Yes, provided that the building is equipped with an appropriate ventilation system (whether natural, mechanical or hybrid). A recent French study mentioned in the AIVC newsletter n°2 shows that better building airtightness converges with better indoor air quality because the ventilation system operates more efficiently. Building leaks cause uncontrolled airflows and potentially poorly ventilated rooms although the total building air exchange rate may be sufficient [1].

[1] L. Mouradian and X. Boulanger, “QUAD-BBC, Indoor Air Quality and ventilation systems in low energy buildings,” AIVC Newsletter No2, June 2012.

What is an adhesive, a grommet, a vapour barrier, etc.?

See Definitions of terms used for tightening products at the end of the list of FAQs.

Are there groups of airtightness testers?

Yes there are. The best known are probably the German FLiB (www.flib.de) and the British ATTMA (www.attma.org)

Since September 2012, TightVent hosts an airtightness associations committee (TAAC) with representatives of national/local associations or groups including FLiB and ATTMA (tightvent.eu/partners/taac).

How is the building airtightness quantified?

The airtightness of a building is often expressed in terms of the leakage airflow rate through the building’s envelope at a given reference pressure (usually 50 Pa) divided by the:
– heated building volume V. At 50 Pa, it is called the air change rate at 50 Pa and noted n50.
– envelope area AE. At 50 Pa, it is called the air permeability at 50 Pa and noted q50.
– floor area AF. At 50 Pa, it is called the specific leakage rate and noted w50.

The lower the ‘airtightness’ value is, the more airtight the building’s envelope is.

How is the ductwork airtightness quantified?

Duct airtightness classes A to D are defined in European Standard EN 12237 for circular ducts and EN 1507 for rectangular ducts. Class A is the leakiest class. A parallel standard to EN12237, EN 1507 and EN 1751 based on the same leakage classification is EN 15727 which applies to technical ductwork products and specifies the leakage requirements for technical ductwork products. The leakage test method for system commissioning is described in EN 12599. Airtightness classes for air handling units (L1 to L3) are defined in EN 1886. System standards, in particular EN 13779, give further recommendations for airtightness class selection for different purposes. [1]

[1]G. Guyot, F. R. Carrié and P. Schild, “Project ASIEPI – Stimulation of good building and ductwork airtightness through EPBD,” 2010.

What are the most common air leakage/infiltration paths?

Common leakage sites are listed in Figure 1 below. Figure 2 gives the classification of these sites in 4 categories [1]:

Figure 1: Vertical section of a typical building with identification of potential leakage junctions (Source: CEREMA - Pôle QERA)

Figure 1: Vertical section of a typical building with identification of potential leakage junctions (Source: CEREMA – Pôle QERA)

  1. Junction lower floor / vertical wall
  2. Junction window sill / vertical wall
  3. Junction window lintel / vertical wall
  4. Junction window reveal / vertical wall (horizontal view)
  5. Vertical wall (Cross section)
  6. Perforation vertical wall
  7. Junction top floor / vertical wall
  8. Penetration of top floor
  9. Junction French window / vertical wall
  10. Junction inclined roof / vertical wall
  11. Penetration inclined roof
  12. Junction inclined roof / roof ridge
  13. Junction inclined roof / window
  14. Junction rolling blind / vertical wall
  15. Junction intermediate floor / vertical wall
  16. Junction exterior door lintel / vertical wall
  17. Junction exterior door sill / sill
  18. Penetration lower floor / crawlspace or basement
  19. Junction service shaft / access door
  20. Junction internal wall / intermediate floor
Figure 2: Common leakage sites classified in 4 categories (Source: CEREMA - Pôle QERA)

Figure 2: Common leakage sites classified in 4 categories (Source: CEREMA – Pôle QERA)

 

[1]F. Carrié, R. Jobert and V. Leprince, “Contributed Report 14- Methods and techniques for airtight buildings,” AIVC, 2012.

 

The text and images of this webpage is available for modification and reuse under the terms of the Creative Commons Attribution-Sharealike 3.0 Unported License and the GNU Free Documentation License (unversioned, with no invariant sections, front-cover texts, or back-cover texts).

How do you design for airtightness?

The answer to this question, amongst others, is included in pp. 07-13 of the AIVC-TightVent  ‘Contributed Report 14’ [1]

[1]F. Carrié, R. Jobert and V. Leprince, “Contributed Report 14- Methods and techniques for airtight buildings,” AIVC, 2012.

What is an air barrier?

What is an air barrier? Air Barriers control the unintended movement of air into and out of a building enclosure [1].

[1]ABAA, “Air Barrier Association of America (ABAA)- The center of excellence for the air barrier industry,” Air Barrier Association of America, 2011. [Online]. Available: http://www.airbarrier.org/about/index_e.php. [Accessed 26 June 2013].

Is building and ductwork airtightness testing mandatory?

It depends on the country and context of the measurement. Most EU countries include in their regulations either required or recommended minimum airtightness levels with or without mandatory testing. There are several countries (e.g., United Kingdom, France, Portugal, Denmark, Ireland) where, by regulation, airtightness testing is mandatory for certain building types or in the case of specific programmes [1].

[1] R. Carrié, M. Kapsalaki and P. Wouters, “Right and Tight: What´s new in Ductwork and Building Airtightness?,” BUILD UP energy solutions for better buildings, 19 March 2013.

What is a Blower Door?

A Blower Door is a device that fits into a doorway or building, containing a fan, for supplying or extracting a measured rate of air flow. It is normally used for testing air leakage by pressurization or depressurization [1]

[1] M. Limb, “Technical note AIVC 36- Air Infiltration and Ventilation Glossary,” International Energy Agency energy conservation in buildings and community systems programme, 1992.

What is an airtightness/air leakage testing? What is fan pressurization?

A method of quantifying how much air leaks into or out of an enclosure. EN 13829 gives a standard test method for buildings. Several standards apply to ductwork systems (see also “How is the ductwork airtightness quantified?“).

Building airtightness levels can be measured by using a fan, temporarily installed in the building envelope (a blower door) to pressurize the building. Air flow through the fan creates an internal, uniform, static pressure within the building. The aim of this type of measurement is to relate the pressure differential across the envelope to the air flow rate required to produce it. Generally, the higher the flow rate required to produce a given pressure difference, the less airtight the building [1].

[1] M. Limb, “Technical note AIVC 36- Air Infiltration and Ventilation Glossary,” International Energy Agency energy conservation in buildings and community systems programme, 1992.

What does n50 mean?

n50 quantifies airtightness. It gives the leakage volume airflow rate in m3/h at 50 Pa divided by the buildings’ volume. It is expressed in h-1.

What are the impacts of poor envelope airtightness on ventilation, indoor air quality and building damage?

Because air infiltration is uncontrolled, poor envelope airtightness may affect:

  • Indoor air quality: Some rooms may be largely under-ventilated while other are over-ventilated.
  • Energy use: Air leakage may inadequately increase the total ventilation airflow rate; or it may not allow sufficient heat recovery (in case of a systems with heat recovery devices, the unit will only recover heat on the airflow passing through it).
  • Building materials: Air leaking out of the envelope may cause condensation damage as its temperature drops below dew point.

What is the impact of duct leakage on comfort, ventilation, indoor air quality and fire security?

Duct leakage is not only detrimental to energy efficiency, but also indoor air quality (in terms of lower air change rates and ventilation efficiency in rooms), comfort, and fire protection. It is often accompanied by other problems, such as inferior commissioning and cleaning. In Scandinavia good ductwork airtightness has largely been promoted together with indoor air quality benefits. Note that the Swedish VVS AMA guideline not only deals with energy issues related to duct airtightness but also with safety and indoor environment. [1]

[1] G. Guyot, F. R. Carrié and P. Schild, “Project ASIEPI – Stimulation of good building and ductwork airtightness through EPBD,” 2010.

Definitions of terms used for tightening products

Adhesive:  Substance that holds one surface to another surface by attachment.

Adhesive membrane: Flexible film (generally made of polyethylene) associated with a nonwoven fabric used to seal joints between the peripheral of a window and a vapour barrier/retarder or a plaster.

Bond: Material used to tie or fasten things together.

Expanding foam: Expanding material (generally polyurethane-based) applied to fill gaps, to fix doors and to insulate connecting joints (especially between window frames and wall).

Fastener: Material used to bind things securely together.

Grommet: Material used to create an airtight seal around circular-section elements such as plumbing pipes, electrical conduits or cables as these pass through the airtight layer.

Joint: Location where several parts of the structure (building or ductwork) meet.

Sealant:  A material that has the properties to join 2 surfaces together to prevent gases, liquids or solids from passing between these surfaces.

Mastic: Putty-like sealant.

Plasters: Fluid or paste-like mixtures made of cement, lime, or gypsum. These products are spread or projected on the surface.

Pre-compressed tapes: (also called pre-compressed foams) Rolls a few centimetres wide whose thickness is reduced when rolled-up and slowly get thicker when installed. They are made of polyurethane or polyester foams impregnated with a synthetic butyl or acrylic resin. The retarded decompression process allows the gaps to be filled while the foam was put without force into them.

Repair tape: Oversized tape roll or flat patch typically used to repair holes in films or holes made on purpose e.g., for blowing insulation.

Tape: An adhesive in the physical form of a tape, i.e., a narrow strip of material.

Vapour barriers or retarders: Membranes or films of large areas originally intended to limit or regulate vapour transfer within vertical walls and roofs. When properly installed and at the right location, they prevent interstitial condensation, in particular in the insulation layer. Their composition can be very diverse, e.g. they can be partly made of polyethylene, polyester, polyane, aluminium, etc. They are usually airtight unless perforated.

[1] Ramachandran, V., Paroli, R., Beaudoin, J., & Delgado, A. (2002). Handbook of thermal analysis of contruction materials. USA: Noyes Publications / William Andrew Publishing.

[2] F. Carrié, R. Jobert and V. Leprince, “Contributed Report 14- Methods and techniques for airtight buildings,” AIVC, 2012

 

The text and images of this webpage is available for modification and reuse under the terms of the Creative Commons Attribution-Sharealike 3.0 Unported License and the GNU Free Documentation License (unversioned, with no invariant sections, front-cover texts, or back-cover texts).