Building

Building Sciences

Infrared inspections of buildings are now an established field of expertise with specialised training courses available for building envelope inspections, roof inspections, damp and mould identification, etc.

A thermal image makes it simpler to see where insulation is missing or air is leaking in or out of a building.  Any object that is not transmitting, generating or absorbing heat will take on the surrounding air temperature, so cold air leaking into a building (or missing insulation on a heated building) will cause cold patches on the wall, floor or ceiling.  Conversely, warm air leaking from a building will cause warm patches on the outside of a wall or roof.

In short, the benefits of infrared thermography are:

• Quick inspections
• Results are easily shown visually
• Identifies the areas of air leakage
• Shows thermal insulation defects
• Reveals the efficacy of heating and cooling installations.

 There are three key elements of a thermographic building survey that you need to know:

1.  Understanding of the construction being inspected.

Construction drawings should be reviewed if available and a full visual examination of the construction completed prior to the start of the inspection. You should also,where possible, consult with the building owner or architect regarding any areas of concern within the building that may require special consideration.

2.  Only undertake the survey under suitable environmental conditions.

Infrared surveys can only be completed under the following conditions:

• An external survey must be carried out during the hours of darkness or with little direct solar radiation.
• It is preferable that an internal survey be undertaken under similar conditions,particularly with lightweight construction.
• Sufficient time must elapse to allow heat previously built up from solar gain to be emitted from the building. The time for this to occur varies with the construction, but normally at least three hours is required.Problems with solar gain may limit the effectiveness of thermographic surveys during the summer months.
• No direct solar radiation on each face in the preceding hour.
• Temperature difference across the building enclosure should ideally be 10 K or greater. Standards 5 state: "a minimum of 3/U degrees"; for example, 6 K for a U value of 05 W/m2K.
• Ambient air to internal air difference at least 5 K for the preceding 24 h.
• Ambient temperature within ±3 K during test and for the preceding hour.
• Ambient temperature within ±10 K during the preceding 24 h, or 12 h for lightweight fabric.
• All building surfaces being inspected to be dry. No precipitation immediately prior to or during the survey, this includes mist and fog.
• Wind speeds during the survey not to exceed10 m/s.

3.  Correctly record and document all survey data.

What The L2 Regulations Say:

Part L2 of the Building Regulations now demands that all new buildings in England and Wales with a gross floor area above1000 m² must be tested for air permeability.

Most new commercial and industrial buildings will need to comply with a maximum air permeability of 10 m³/(h.m²) of building envelopes.  This means that the buildings will need to be tested during construction to ensure that the standard is being met and if not, that remedial works are carried out and the building re-tested.

In England and Wales, Part L2 of the Building Regulations introduced from April 2002, recommends thermal imaging of new building fabric to ensure continuity of insulation.  Section 2.1 of the document states:

The person responsible for achieving compliance should (if suitably qualified) provide a certificate or declaration that the provisions meet the requirements of Part L2(a); or they should obtain a certificate or declaration to that effect from a suitably qualified person. Such certificates or declarations would state:

1. That appropriate design details and building techniques havebeen used…or
2. That infra-red thermography inspections have shown that the insulation is reasonably continuous over the whole visible envelope.

Other regulations apply in different regions, but the principles remain the same.

Air Leakage Testing

Thermography is a quick, easy way of locating air leakage from a building envelope.

Although it cannot quantify air leakage rates, infrared thermography provides the most rapid means to identify unintentional air leakage pathways in a building envelope.  The benefits of infrared thermography in this context are:

• Air leakage pathways within a completed construction can be identified and rectified prior to air permeability tests, reducing the risk of repeat testing being required.
• Depending upon the nature of the construction, even a building that meets or exceeds air tightness requirements may still be at risk of deterioration due to air leakage and subsequent condensation.Identifying where air leakage is occurring can be critical.
• Air leakage pathways can often indicate rainwater ingress pathways adding to the potential benefits of an infrared survey.

Building Pressure Testing