Air Tightness - a Definition and the Building Regulations Part L

AIR TIGHTNESS - A DEFINITION

Air Tightness – the resistance of the building envelope to inward or outward air leakage. Excessive air leakage results in increased energy consumption and a draughty, cold building.

Air leakage is driven by differential pressures across the building envelope. The mechanisms that create these differences in pressure are the combined effects of – stack (internal warm air rises), external wind (inducing +ve and –ve pressures on the envelope) and mechanical ventilation systems.

THE BUILDING REGULATIONS PART L

Note – Part L1A/B apply to dwellings. Part L2A/B apply to non–domestic buildings.

Why Do The New Building Regulations Part L include for air tightness

The Government is committed to reduce CO2 emissions from energy consumption by 20% by the year 2010, relative to 1990 levels. This is a long term commitment outlined in the Energy White Paper for a 60% reduction in UK CO2 emissions by the year 2050. The energy use within buildings accounts for approximately half of all UK CO2 emissions. Two major factors in the design and performance of building fabric which affect energy consumption are, air leakage and continuity of insulation.

There are also substantial commercial benefits to building owners that will accrue over the life time of the building. Reduced energy costs provide clients with real cash incentives to achieve airtight buildings.

Other benefits are gained from increased comfort for building users, office staff and / or customers. Although difficult to total, these are tangible benefits to the client.

When did Part L come into force?

Approved Documents Parts L1 and L2 came into force in April 2002. The latest revision of Part L came into force on the 6th April 2006 and introduced air tightness testing as a legal requirement for nearly all new non-domestic buildings. There is also a requirement to test a sample of new dwellings.

Golden rules to ensure Part L is met

All parties involved on the project from the client, contractor and consultants to all site staff and operatives and off site suppliers need to understand the concepts of air tightness and how they affect the part of the project they are involved with. It only takes one part of the building to be leaky to ensure a failure to comply, which can lead to costly remedial works and time delays. A real effort needs to be made to educate everyone involved and ensure that a team effort is made. ALL buildings require designs to incorporate robust details to ensure air tightness, continuity of insulation and potential problems with thermal bridging are addressed.

For Air Tightness;

Requirements for dwellings, carry out air tightness tests on a sample of dwellings in accordance with ATTMA TS1.For non-domestic buildings, carry out an air tightness test in accordance with ATTMA.

Using a company such as HRS, who are full members of ATTMA, ensures clients can have confidence that Building Control/Approved Inspectors will accept the air test result. It also means that HRS can negotiate on behalf of their client if dispensation is required on any part of the project. Use the check list below to identify whether the company is ‘suitably qualified’.

 

How long has the company been established?

HRS have been established 20 years and have worked on air sealing and air tightness testing for 13 years on 1000’s of projects to best practice levels for Tesco, Wm Morrison’s, Asda etc. NOTE: Companies established in 2001/2002 generally have little experience of air sealing/testing and were set up to ride on Part L2.

What experience has the company of working on projects with different contract types?

HRS have experience of working on projects with contracts varying from D&B, PFI, JCT, Shell and Fit Out, and understand their implications for air tightness and other contractual matters.

What experience does the company have of working on complex or large projects?

HRS have experience on working on several very large developments >£200M, as well as 100s of smaller contracts and has gained experience of all manner of complex air tightness/building/contractual problems.

Does the company hold relevant ISO 9001, UKAS accreditation, backed up with PI insurance?

Is the company a member of ATTMA (Air Tightness Testing Measurement Association) whose members are recognised as competent by Building Control/Approved Inspectors nationwide?

HRS are accredited to ISO and UKAS, all backed up with £2 M P.I. insurance. HRS were asked to help set up the ATTMA in 2002, due to HRS’s experience and technical knowledge. Being recognised nation wide by Building Control /Approved Inspectors allows and helps HRS to discuss areas that may need dispensation.

What documented calibration evidence is there for the air test rig (not just the fan) and all other measurement kit within the last 12 months?

Measuring air flows and pressures is sensitive and significant errors do easily occur. HRS calibrate all air test rigs and measurement equipment every 12 months in line with UKAS requirements. NOTE: Small companies may have rigs that have only the fan calibrated by the fan manufacturer, which may lead to significant errors. There is the obvious risk of using non-calibrated kit leading to incorrect results.

What experience do the air test technicians and company have of air sealing buildings?

This is important for main contractors. If an air test fails and the air test company can not help, there is a risk that the main contractor is left blind as to the causes of failure and will be forced to carry out a full smoke test. All HRS air test technicians (and managers) have experience in air sealing and HRS operations managers have been involved with all manner of air sealing and testing problems. If HRS doesn’t know how to get over an air sealing and/or testing problem, no one will!

What is the biggest building tested by the company?

HRS have air tested buildings with floor areas up to 60,000m² and 32 storey tower

What is the smallest component/ building tested by the company?

HRS have air tested joints between panels and small rooms on buildings with floor areas of 20m².

What experience has the company of actually air sealing various designs and sizes of buildings and components?

HRS have 13 years experience of both air sealing and testing all manner of buildings and components. No other company has this level of experience in both sealing and testing.

What is the tightest air tightness specification worked to?

HRS have carried out the air sealing and final air tests on a series of rooms that had to reach an air tightness target 25 times tighter than Part L2, 0.4m³/(h.m²) at 50 Pascals.

What calibrated volume flow rates have the companies fans got?

This demonstrates what size buildings/ rooms/ components can be tested to the relevant specification leakage rate. HRS calibrated fans range from Low Volume Flow Fan – 8 litres/second suitable for testing fume cupboards or building components up to MIDIfan - suitable for testing very large warehouses.

How many rigs have the company got which are capable of testing a 1000m² building? If a company only own 1, you may not get the day you want.

HRS have 12 separate rigs capable of testing a 1000m² building. Consequently, it is very rare that contractors can not have the day they want.

What references can be supplied from blue-chip clients who have been dealt with over a period of time?

HRS have worked for over 13 years for Tesco, Wm Morrisons and main contractors such as Bovis Lend Lease, HBG, Warings, MACE and Bowmer and Kirkland.

Logos for various accreditation bodies

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