Where Do Buildings Leak

Airtightness Introduction

Introduction to airtightness

Airtightness shows quality in a building. Airtightness makes ventilation/heating systems work properly whilst improving insulation’s effectiveness. This helps with reducing our fuel bills and increases health & comfort through the elimination of mould and condensation.

How do we measure airtightness?

We measure airtightness by temporarily mounting a calibrated fan in a window or door opening. We then take a series of readings of imposed pressure differential against the airflow generated by the fan – which is a function of (a) how big the building is and (b) how airtight (or otherwise) the building is.

What equipment is used in airtightness testing?

When carrying out airtightness testing, we use the following;
One or more calibrated fans, temporarily mounted in an open door or window.
Control equipment
Pressure gauges
Thermometers
Barometers
Tape measures

How do I oversee or witness an airtightness test?

For an airtightness test to be valid, several conditions must be met;
The test equipment must have a current calibration certificate
The test engineer must be competent to test the building using the applicable standard
The zero-flow pressure differentials are low enough
The building must be ready to test

How do I prepare for the test?

An Air Tightness Test (which is also known as air leakage test, air pressure test or air permeability test) is a government regulated test to ensure buildings do not leak or retain too much air.

Before an air test is carried out, we need to make sure the building is complete and is clear of all trades in order to achieve the best results possible.

The following criteria should be followed to provide you with the best chance of passing an air test:
1) All fixtures and fittings are installed including lights and sockets.

2) Every service penetration is sealed
All plumbing work is complete with water in the traps.

3) Seal skirting boards in every room
Gaps within walls and floors must be sealed.

4) Bathrooms and kitchens must be fully fitted and mastic sealed.

5) No work trades to be in the building where the test is carried out.

6) All external and internal windows and doors must be installed and closable.

7) The loft hatch is fitted and sealed.

8) 240V power being available in the plots being tested.

Risks in Airtightness

Key Risks associated with airtightness include:
Failing the airtightness test. The most common problem for a contractor or designer. Likely to mean extra sealing works for the contractor, possibly even design issues needing consideration (e.g. discovering that dot-and-dab plasterboard finishes cannot deliver the specified airtightness).
Poor airtightness. This usually means that the property under test is too leaky. But at the other end of the spectrum, ventilation can prove inadequate as the airtightness is improved. This can give rise to condensation and mould, with damaging health impacts.
For many years we have applied the slogan:
Build tight, ventilate right
These days, we try to avoid adding pollutants within a building, from paints, carpets and coverings, furniture. But the biggest issue is usually water. Water in the air leaking through the fabric of our buildings is likely to condense en-route, leading to damaging moisture in walls and roof spaces.

What standards are applied for airtightness?

Airtightness testing in the UK is governed by ATTMA, the Air Tightness Testing and Measurement Association. This is part of BCTA, the Building Compliance Testers Association.

The Future of Housing – And How Airtightness Can Help

A documentary by House Planning Help

Ben follows air leakage expert Paul Jennings from ALDAS as he tests different buildings to see how they perform and how they could be improved.

View the HPH website

ON-DEMAND TRAINING BOTH ONSITE & IN THE OFFICE

Education Opens up the Mind

Aldas offer a wide range of training modules. We are able to deliver this training both onsite or online. Our team are setup to deliver tailor made training for individuals or groups in all aspects of airtightness

Get Trained

Intro to Airtightness
Onsite Passivhaus
Effective Sealing
Leakchecker Fans
Refurbishment
Quality Control
Design Training