Quantifying energy loss

Once the preserve of the few, thermal imaging is now a universal tool used by many. Today the entry cost to infrared is around the £1,300 mark and its commercialisation has allowed the technology to be applied economically to an exceptionally broad range of tasks. One of the sectors in which it continues to have the greatest impact is in building and construction.

Infrared cameras with dedicated application software have been developed to accommodate the specific needs of these industries resulting in their wide use to spot structural failures and insulation defects. Thermal imaging is also the best method of seeing and quantifying energy loss, a vital ability as the industry adapts to the opportunities and challenges posed by the 2012 carbon emission targets.

The building sector currently accounts for 40% of the EU’s energy requirements and therefore offers the largest single potential for greater energy efficiency. Energy Performance Certification has become mandatory in many EU countries and this, together with recent economic stimulus packages is likely to drive the demand for air tightness testing and other methods for investigating energy loss.

In the longer term, we are likely to see harsher EU directives exemplified by the development of the passive house concept. This is currently a voluntary building standard that far exceeds present regulations. Its aim is to reduce the need for heating in a new-build by 90% by comparison with a traditional built property. This will have a great impact on many professionals working in the building sector but with infrared in their armoury, these objectives will be far easier to achieve.

What’s the choice?

Today’s thermal imaging cameras for building inspection generally fall into four distinct groups. Firstly there are the basic point and shoot models with fixed lens and focus. Next in line are the intermediate cameras that typically add in basic diagnosis, manual focus, a visual camera and helpful features such as image storage to USB. Also incorporated at this level is wireless technology that enables, for example, the thermal camera to communicate with a clamp meter so that the relationship between heat and load can be established. Similar readings from a moisture meter and psychrometer can be recorded on the image along with other readings such as relative humidity and ambient temperature.

The third category is aimed at the professional in need of comprehensive performance. These cameras provide higher image quality, additional lenses with auto focus, advanced diagnosis and energy auditing function. The top of the range expert series naturally provides the best performance, technically specific applications and additional tools such as video, GPS, digital detail enhancement and all that is needed for in-depth analysis and reporting.

Typical applications

Infrared is a powerful and non-invasive, non-destructive technique that is ideal for multiple applications and its use in highlighting insulation defects is a good place to start. Missing insulation and delaminating render are easily detected by an infrared camera. All that is required is a difference of about 10°C between the outside and inside temperature of the building for the thermographer to capture good, easy to interpret thermal images. By using a camera with higher resolution and thermal sensitivity, the temperature differential can be less as the image detail will be correspondingly greater.

Air leaks and moisture detection

Higher energy consumption is the by product of air leaks. Commonly, these are detected by the use of a ‘blower-door’ that creates a pressure deficit inside the building. The higher external pressure causes air to escape through unsealed areas and the airflow can be seen by the effect it has on surface temperature. Once identified, untight areas can be rectified before coverings and fittings make it expensive and time-consuming for the fault to be corrected.

Air leakage is also the cause of condensation build-up in walls, floors and ceilings. As wet insulation materials take a long time to dry they become the prime location for the growth of mould and fungi. It’s often a problem that can be smelt rather than seen with the human eye but a quick scan with an infrared camera will locate the moisture that creates an environment conducive to mould.

Moisture can sometimes be difficult to spot so the trick is to raise the ambient temperature in the room. Wet materials will then become clearly visible as their temperature increases much more slowly than dry materials. A major benefit of infrared of course is that it can inspect a substantial surface area in a single pass of the camera whereas other methods only provide a single spot reading.

Tremendous cost savings can also result when wet sections of a roof can be repaired in preference to replacing the entire structure. By using the sun as the heat source it is easy for the infrared camera to determine areas of moisture ingress as night falls and the roof cools down. Again, it can see the problem spots because the temperature of wet insulation reduces at a slower rate causing a differential that creates a thermal picture.

Drying and glass

Using this principle, infrared is additionally proving beneficial in assessing the effectiveness of construction drying. Heat generators rapidly evaporate the water which is naturally present in the walls and areas where moisture remains can easily be seen on an infrared image as a cold spot. By the same token infrared is becoming highly valuable for use before and after flood restoration work.

Another application for infrared is fenestration. Glass is now a highly engineered product and its composition and surface finish have a profound effect on its performance. An infrared camera can, for example, be used to determine if there is a gas leak in a double glazed unit. Gas is heavier than air and will sink to the bottom of the unit. Where there’s gas there’s greater thermal efficiency and the camera shows a clear dividing line in the unit’s performance.

Electrical and HVAC

Electrical faults in buildings are common. Invisible to the naked eye, the faults are seen by the infrared camera as hot spots.

It is a highly cost-effective technique for scanning electrical cabinets for surface evidence of problems, for surveying multiple wiring circuits, connections, fuses and lighting. And of course the result of discovering a fault may not just be greater energy efficiency; it could also prevent a fire. The technology is equally good at spotting problems with blocked chimneys or exhaust systems.

Even when water pipes are laid in the floor or under plaster infrared can be used to check for leaks. It can also provide useful information on the function of air conditioning covers, radiators and ventilation systems, indeed any part of the HVAC system. As a result, the climate in the workplace and in the home can be optimised. It’s good as a pest control tool too!

Infrared has already proven itself as a highly flexible tool for building inspection. Its scope of application is not only vast but also steadfastly growing and with every new application added to the list, return on investment is accelerated, making infrared more and more cost-effective.