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Unit 15, Netherton Business Centre

Kemnay, Inverurie, Aberdeenshire

AB51 5LX. Tel: 07732 561573

www.fec-home.co.uk

Air tightness testing of traditional and new rural housing

Traditional houses are usually draughty, especially when it is windy. In these conditions, all the air in

the house is changed about every 5 mins. The cold air from outside blows in, causing discomfort,

replacing the warm air inside. Extra fuel is then needed to keep the house warm. Reducing draughts

will therefore improve comfort and reduce heating fuel

costs.

Although all new houses need to be air tightness tested to

check that they are not excessively draughty, even these

may need improvement. The same process can be used on

both new and traditional houses to identify draughts, to

assess the scale of the problem, and to guide towards a

more airtight home.

It is important to understand that:

Improving air tightness means reducing unintended ventilation. Controllable ventilation such as

extract fans, trickle vents and opening a window, must allow for sufficient fresh air. Some

combustion heaters must have permanent ventilation.

Whilst some air may escape directly to outside, most will leak out through the buildings structure.

The moisture in the warm air will easily condensate on the cold surfaces of the external wall which

could cause structural problems. Reducing draughts therefore helps reduce the risk of timber rot.

Key steps for dealing with draughts are:

1. Identify where the air is coming in with either an air tightness or draught detection test.

2. Seal leakage, where possible

3. Where more extensive renovation is needed ensure that the work is to be completed in an

airtight manner

4. Test again after completion, to ensure that building work including windows, kitchen or

bathroom suites have been installed without leaving gaps.

These services will be of most interest to

householders who:

• Want to reduce heating costs

• Feel their house is draughty

• Want to protect the house structure

• Or, simply have concern for the

environment.

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Air tightness testing

An air tightness test involves fitting a large fan to the door of a house (Figure 1). After known

ventilation systems have been sealed, the fan sucks air out of the house. The amount of air that

flows through the house can then be compared to accepted standards, indicating a pass or fail. An

official report will be provided.

With the fan operating the draughts are usually obvious – you will feel them with the back of your

hand – or cold smoke can be used as an indicator. During the test a thermal imaging camera can be

used to reveal less identifiable leaks, and variations in insulation.

Even a tiny crack can leak a lot of air, if it is long.

Unsealed skirting boards are a common source of air leakage. The thermal image in Figure 2 shows

that the joints between tongue in groove cladding which are also a source of air leakage.

Figure 1: Fan fitted in doorway Figure 2: Air leakage between joints of T & G

panelling, and a larger leakage area

(blue).

Some air leakage, such as holes around pipework, are made clear during an air tightness test, even if

they are hidden by built-in units. If inaccessible, the only solution may be to ensure that future units

are not installed until the wall behind has been sealed.

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Draught sealing

Our draught detection service aims to highlight the main sources of draughts so that they can be

blocked. Many methods are available to seal draughts, including using sealants, draughtproofing

strips and secondary glazing solutions.

So long as steps are taken to minimise moisture in the house, and ventilation is provided for heating

devices, it is highly unlikely that the house will be over sealed: see the blue box below.

Future building work

Clearly, ensuring that building work is

sealed during construction is the best

solution. Many tradesmen do not

recognise the need for sealing the

building, so may leave holes unless they

are explicitly requested not to do so.

Even gaps of 1 mm or less give significant

air leakage for example window frame

edging, if left unsealed, can be a problem.

Air tightness testing before and after

building work will encourage builders not

to leave unsealed holes.

Alternative heating

solutions

Whilst occupants often want central

heating to increase the air temperature in the house, with draughty houses alternative systems may

be more efficient, so cheaper to run. The selection of heating systems is complex, and the standard

options may not suit best in the long term. However, we can assess your requirements and suggest

other solutions.

How much ventilation is actually needed?

The amount of air exchange needed is determined by

the amount of moisture in the house. The key sources

are steam from: bathroom, drying clothes and cooking.

Remove this and the need for ventilation greatly

reduces.

What is the impact of poor insulation?

A poorly insulated house will not only lose heat but

require low humidity to prevent condensation, damp

and harmful moulds. Keeping relative humidity to

below 60% will normally be sufficient to avoid

problems.

This can be achieved by fitting humidity-controlled fans

and, if necessary, dehumidifiers. Home owners are

usually good at controlling conditions in their home,

but they need feedback. Humidity displays are cheap

and easy to install, so are well worth considering.

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How to proceed

To start improving your home energy efficiency we offer the following services:

1. Draught detection

2. Infrared surveys

3. Full air tightness testing for existing, new, or extended houses.

Advice is provided on remedies and draught proofing to make your house more comfortable, and

energy efficient.

Please contact FEC- Home at the above address, or by calling 07732 561573.

More information available on our websites:

www.farmenergyconsulting.co.uk

www.fec-home.co.uk

www.fec-acoustics.co.uk

Approved Tester No: 0588

For official air tightness tests, we maintain calibrated equipment and are fully accredited for

testing with the Independent Air Tightness Testing Service.

Full tests are most efficient if plans of the house are available and can only be done when the

house is ready and during suitable weather conditions.