Top ten tips for air tightness compliance

A BSRIA Presentation

By Andy McGrath

2Making buildings better

Presentation Topics

1. What is Air Leakage

2. Air Leakage Paths

3. General Principles & the Air Line

4. Building Tight – Walls, Dry Lining & Ceilings

5. Harron Homes

6. ATTMA Competent persons Scheme & Certificate Lodgement

7. Temporary Sealing

8. Checklist


What is air leakage?Air leakage is the uncontrolled flow of air through gaps and cracks in the fabric of a building (sometimes referred to as infiltration or draughts).

This is not to be confused with ventilation, which is the controlled flow of air into and out of the building through purposebuilt ventilators that are required for the comfort and safety of theoccupants.

Air leakage commonly occurs at interfaces between construction elements.Typical locations include:

• Wall to roof and wall to floor junctions

• Window and door to wall joints

• Service penetrations


Air Leakage Paths

Air leakage paths are quite often tortuous – air may travel some distance through the building fabric between the points of entry and exit.

The key to ensuring good levels of airtightness is to ensure the air tightness line in a building is continuous


General Principles of Design & ConstructionThe basic principles of airtightness are:

• Airtightness is not rocket science, but it doesn’t happen by chance

• The airtightness strategy should be simple, robust and achievable

• The building air line should be identified pre-construction and preferably at design stage

• Responsibility should be given to a nominated individual or team

• Communication of its importance and relevance is key

• All parties in the process should be involved

• Common details should be generated• It must be clear who is responsible for sealing each element• Protocols for checking detailing must be in place


What is the air line?

The air line is normally defined as the element(s) that are used to create the airtightness line.

• The air line should be decided at design stage

• It must be continuous around the building

• It must be possible to slice through the building on any plane and see a continuous air line

• The air line should be continuous with the thermal line

The Air Line / Air Tightness Line - Think of a continuous RED line around the Building.


Basic Principles


Basic Principles


Building Tight

To ensure compliance with Building Regulations the developer needs to consider two air barriers, these being:

1) Internal block work face

2) Dry-lining

Our investigations have shown that in the majority of cases a bare block work shell is capable of exceeding the requirements set out in Part L1A with scores as low as 3m³ (hr.m²) being achievable.


The Build Elements – Walls


The Build Elements – Walls


The Build Elements - WallsThese form the vertical elements of the envelope, some are structural, some not, but all are required to perform an effective barrier between the internal and external space.

Best Practice• Blockwork used as the air line

• Soft joint to all other components

• All penetrations, such as windows, sealed to the airline element• Generally, walls should be sealed to the floor and ceiling

Traditional Block and Brick CavityIt is the most common wall type, but can also deliver the most variation in airtightness performance. This is mainly as a result of workmanship and the airtightness performance of the block work.


The Build Elements - Walls

The block work must provide a continuous barrier:

There should be no gaps in the coursing.

Where the block work barrier is breached the penetrations should be sealed so that the integrity of the shell is restored.

Examples of this will include joist penetrations and service penetrations

The responsibility for these requirements should be delegated by the developer to the appropriate trades i.e. bricklayers, plumbers etc.

In instances where the responsibility for performing these sealing works has not been clearly stipulated, failures often occur.


The Build Elements - Walls

The block work itself must also provide a square edge to the cavity closers, failure to do this will result in difficulty sealing the block work to the cavity closure, which should be sealed to prevent air entering the cavity.

The block work stops short of the cavity closure, leaving a large void to fill

The cavity closer has been sealed to the block work, lintel and window ensuring the air line is maintained.


The Build Elements - WallsWe would recommend that the dry-liner should be permitted to tack the top floor ceilings, (and 1st floor ceiling in 2.5 storey dwellings), to the trusses before any other trades commence work. This is to allow the shell envelope to be completed, as long as the developer ensures that the:Perimeter of the ceiling is sealed to the block work

The gap between the wall and ceiling will allow air leakage to occur if a continuous ribbon of adhesive is not present on the dry-lining

A mechanical seal is present between the top floor ceiling and the external wall ensuring the air line is maintained.


A gap is present between the window board and the block work, a cavity closer is not present allowing air leakage to occur

A mechanical seal prevents air leakage occurring

Building Tight To ensure that the air line is maintained,

all penetrations through it must be sealed

Ensure products that have their own means of sealing to the air line are effective and that there is no additional sealing required

Ensure products that have their own means of sealing to the air line, are effective and that there is no additional sealing required


Building Tight To ensure that the air line is maintained all penetrations through it must be sealed

There is no cap to the top of the SVP boxing, providing a significant air leakage path.

A gap has been left at the penetration of the SVP through the ceiling

The ventilation duct has not been sealed to the block work as it passes through it

The boiler flue has not been sealed to the block work as it passes through


Building Tight at an Early Stage

At this stage the developer should be able to inspect the dwelling and see that the shell integrity is satisfactory. This must be done prior to any internal finishes being installed. At this point the only air leakage present in the dwelling will be through the block work itself.The Blockwork can be used as the air line, if the Blockwork envelope is sealed, this is a good start to achieving Air Tightness.


Failure to ensure the integrity of block work and dry-lining will result in multiple egress points

When dry-lining takes place it is imperative that the requirement to ensure a continuous solid dab is adhered to.

This will significantly reduce the volume of air that can reach the internal block work face and will therefore aid in preventing leakage through the block work itself, it should be noted that the dry-wall adhesive is not an impermeable product.

Continuous solid dabs must also be present around all electrical outlets and any other such penetrations.

Building Tight Dry-Lining

The lack of a continuous ribbon of adhesive will allow air leakage to occur through penetrations to the plasterboard

Another example of “dabs” rather than continuous ribbons being used.


The Build Elements - WallsCommon Pitfalls

• Blockwork sealed to steel beams/lintels, but beams not sealed

• Blockwork hidden behind internal finishes before penetrations are cut, making access to seal the blockwork difficult

• Expanding foam used for filling gaps, but this is often performed ineffectively. If used it should be used appropriately and sparingly

• Mortar seal between wall and beam joint – incorrectly assumed appropriate, mastic seal should be present.


Elements – Ceilings/RoofsPlasterboard

Plasterboard will commonly form the airline. This may be horizontal, or contain multiple elements for warm roof constructions

The more complex the design the more consideration must be given to the continuity on the air lineBuildings that have a full storey on the top floor are potentially the simplest to design an air seal line for. However they can have significantly more breaks in the line than you might first think.

Best Practice

• The ceiling should be continuous

• It should be mechanically sealed to the vertical air line

• All penetrations, such as loft hatches, sealed to the airline element


Elements – Ceilings/Roofs


Elements – Ceilings/Roofs


Elements – Ceilings/RoofsCommon Pitfalls

• Significant number of breaks in the airline that are not visible and therefore often not sealed

• Service penetrations inside internal walls

• Service penetrations behind boxings

• Ceiling line often broken at internal walls


Elements – Ceilings/RoofsAir Barrier Continuity – Bed the wall plate on a continuous mortar bed.Fix ceiling first and seal all gaps between the ceiling and the masonry wall with either plaster, adhesive or flexible sealant.Seal all penetrations through air barrier using a flexible sealant.Install a double, full length nogging between the floor joists and seal between the nogging, ceiling and upper stud wall with a flexible sealant. The dotted blue line depicts the continuity of the air barrier through the noggings..


Checklist

Detail Outcome

Block work Must have no gaps in the coursing

Joist penetrations Must be sealed to the block work

Windows/ Cavity closers

Must be sealed to each other and block work

Service penetrations

Must be sealed at both block work and plasterboard penetrations

Dry-Lining Must have a continuous ribbon around the perimeter and around electrical outlets, etc.


In respect of conducting Air Tightness Testing, it should be noted there have been some changes that have been applied in respect of the implementation of a Competent persons scheme by ATTMA (Air Tightness Test and Measurement Association).

This has been implemented along with changes to the Certification scheme , with a certification lodgement scheme being applied and an automatic check regarding any deviations on the test.

ATTMA Competent persons Scheme & Certificate Lodgement Scheme


Air Tightness Test Worksheets & Certificate of Air Permeability Test

As part of the ATTMA Scheme, it will be a requirement to lodge tests and a link can be sent to the developer to download the certificate. The BCO can also verify the certificate.The worksheet and associated test file are submitted to ATTMA, this is reviewed and if compliant, an ATTMA certificate is issued & Lodged.


Implementation of ATTMA Competent Person Scheme

Air Tightness Testing Competent Persons Scheme

The DCLG wished to see the underlying assessment of competence for air tightness testers, to be strengthened with a Competent Persons Scheme (CPS), wanting it to be compliant with the latest Conditions of Authorisation. It wanted it to be better controlled, regulated and observable.

DCLG (Department for Communities & Local Government) have authorised ATTMA to run a competent persons scheme for Air Tightness Testing.


Building Regulations 2013 - 43 (4) – explicitly allows a BCB to accept an air tightness “certificate” if it has been produced by someone who is registered by either BINDT or ATTMA

The Building Regulations AD L1a and L2a documents state under 3.15, that the BCB should confirm that the person (offering the Certificate) has been appropriately trained and registered for the specific building type. If the Air Tightness Tester is registered with ATTMA the BCB are able to accept this without further qualification of their competence.

BINDT have closed their list of accredited testers and will not be running a CPSThe ATTMA scheme is therefore currently the only authorised scheme, although at least one other application has been made to DCLG



All BSRIA Compliance Test Engineers are registered with the ATTMA Competent Persons Scheme for Air Tightness Testers

In order to fulfil some elements of the ATTMA Competent Persons Scheme, the Test Reports for the tests conducted by BSRIA Compliance are lodged with ATTMA and the certificates for the Airtightness Testing are thus generated by ATTMA and lodged on their scheme system.

ATTMA have issued guidance on what is and what is not acceptable in respect of the Temporary Sealing applied to a plot for the Air Tightness Test. We are now going to see the ATTMA Guidelines on Temporary Sealing.



ATTMA Temporary Sealing Guidance



Examples - Not Acceptable Temporary Sealing





These Temporary Seals – WHY ?It can only be an attempt to CHEAT the test. There is no other objective. Will the tape be removed after the test. Will the fault be left as it is?There is No Respect to Quality or Consideration to future Occupiers.This is Not the Way – Build Right is the RIGHT Way.


Air Tightness Test Worksheets

If your Air Tightness Test Worksheet has the deviations Box filled, (bottom left), with Temporary Seals that have been applied, that should not have been, then thereis a chance you will not receive the ATTMA Certificate or it will be marked as we can see.


Refer to the BSRIA Checklist relating to elements of the build that should be finished/complete and checked/ready for Testing .Below are a few guidelines for the Site Managers in respect of preparing for the Air Tightness Tests.• Failed Tests and Plots not ready for testing, all increase costs for the Build• Ensure that you only Book Tests for the plots that you believe will be ready• Ensure that you check that each plot will be ready for the test, 24 hours before

the test• Check the notification of testing received from BSRIA and inform BSRIA of All

Cancelations/Changes to plots requiring testing, prior to the scheduled testing date

It would be best if the site manager should check the day before the scheduled tests, that the plot is ready for testing, (please refer to the BSRIA Checklist), if the plot is not ready for testing, if you advise BSRIA the day before the test, then there will be no charge.Where a visit to site has been conducted to test a plot and it is not ready for the test, then a charge will still be made.

Checks to be Made


Make Sure the Plot is Ready for Testing.

• Is there power available?• Are incoming services connected / sealed ie electric, gas, water,

waste? • Plumbing complete & traps filled• Is plot at final fix stage? Mastic bead to sanitary ware, gaps sealed

under bath/shower and around toilet. (Rockwool does not make an airtight seal)

• All electrical sockets, lights (where appropriate) and switches should be in place – not sealed.

• Windows, trickle vents, doors should be installed and windows should be operable.

• Door Thresholds complete• Boiler Flue penetration sealed.• SVP penetration to boxing & ceiling, sealed.• Loft hatch fitted and perimeter of hatch sealed.• Wall / floor junction sealed.• Mastic for air seal line, complete

SEE the BSRIA CHECKLIST


SummaryWe hope that these presentations have provided you with an overview on Air Leakage / Air Tightness Testing.

The first presentation afforded an understanding on Why Testing is required, What causes Air Leakage and a summary of the Part L building regulations that apply, along with an understanding on Testing Regimes.

The second presentation gave guidelines on the Basic principles, confirmation on how important the Red AirLine is and how it must be continuous, unbroken.

It also provided some tips on how Air Tightness can be achieved and information on the changes to Air Tightness Testing with the implementation of the ATTMA Competent Persons Scheme, Certificate Lodgement and Temporary Sealing.

We trust that this has been beneficial and of interest and hope that you take away an understanding of the Requirements for Air Tightness testing.


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Top ten tips for air tightness compliance