“We are building refrigerators inside ovens”
William Whistler, LEED AP, Estidama PQP and managing director of Green Building Solutions International, explains how thermography is used to maximise the energy efficiency of buildings The issue we see with buildings here in the desert climate of the UAE is that villas and commercial structures which are not properly airtight allow climate and weather […]
William Whistler, LEED AP, Estidama PQP and managing director of Green Building Solutions International, explains
how thermography is used to maximise the energy efficiency of buildings
The issue we see with buildings here in the desert climate of the UAE is that villas and commercial structures which are not properly airtight allow climate and weather factors to greatly increase energy wastage, lower interior air quality and accelerate building deterioration.
The energy required to comfortably cool and maintain a stable range of humidity in buildings increases dramatically due to uncontrolled air transfer through the building’ exterior fabric.
Standard practice in this climate is to design buildings with slightly positive pressure; however, this approach is limited in its ability to ensure that uncontrolled infiltration will not occur.
In addition to the immediate effects on energy wastage, ‘leaky’ buildings allow increased moisture infiltration, more rapid deterioration of building materials, poor indoor temperature and humidity control, contribute to mould infestation and compromised fire and smoke protection measures.
Buildings in the hot, harsh climate of the GCC and MENA regions are particularly at risk to the effects of building envelope air leakage because a combination of intense solar heat radiation and excessive dependence on mechanical air conditioning put great thermodynamic stress on a building’s skin or fabric.
We are, in effect, building refrigerators inside an oven.
Testing envelope performance
The tools and methods to determine the correct air tightness of buildings have until this time been developed in colder or more moderate climates than we have here in the Middle East and North Africa region.
The physics of air movement, humidity and thermal transfer are of course the same. Here, however the emphasis must be placed on the ‘reversed’ conditions we find in intensely hot climates.
For example, heat energy always goes from warm to cool. In colder climates the usual energy usage problem is to contain mechanically produced heat from escaping to the colder outside air; this is called exfiltration and is tested by producing positive pressure in the interior of a building.
Typically in the UAE 60-70% of our energy usage is expended to produce mechanically cooled and humidified air; a building’s ‘skin’ must protect our interiors from the sun’s heat and the infiltration of hot desert air.
Any testing of the effectiveness of a building’s envelope and its contribution to energy savings must be based on this critical difference. The combination of professional non-invasiveprocedures — infrared thermography, fan pressurisation and smoke (vapour) path analysis is cost effective and timely in identifying where and how much remediation might be required.
Although the use of these technologies is not widespread in this area, air tightness testing is referred to in both the Abu Dhabi Estidama Pearl Rating System and the new Dubai Green Building Regulations and Specifications.
Testing procedures
Fan Pressurization Testing. A standard fan pressurisation test will indicate the relative size of the air leakage and the rate of airflow as measured against the total building envelope. To locate where the leaks are this test should be used together with infrared thermal imaging and smoke (vapour) path analysis.
Infrared Thermal Imaging
Infrared thermal imaging is a non-invasive inspection process. This greatly reduces the time and cost of determining actual as built conditions.
Correctly calibrated by a trained professional, an infrared imaging inspection can also be used to detect:
– moisture intrusion
– insulation installation verification
– thermal energy loss
– missing grout in CMU walls
– leaking water piping
– roof waterproofing
– thermal bridging of building materials
– likely areas of mould growth
Smoke Path Analysis
Smoke (vapour) path analysis can be a highly cost effective method of identifying and isolating the locations and intensity of unwanted and uncontrolled air flow.
State of the art testing uses traceable water vapour (similar to a smoke effect in a nightclub) to determine the air leakage travel path.
Building in ovens
Building air tightness is especially critical here in the UAE because the large temperature difference between the hot outdoor air and the mechanically cooled interior air puts great stress on the building fabric.
Unplanned leaking of building air due to either poor design or construction flaws has enormous impact on energy usage over time and invites moisture intrusion causing mould growth and other problems.
Remediation is generally straightforward once the problem is identified. Much like a medical diagnosis, building
envelope testing allows a view into poor building performance and will demonstrate the root cause of the problem, not simply test the symptoms.
A combination of the three testing procedures provides the most accurate air leakage analysis. The goal is to produce reliable, practical information that can be used to reduce energy waste, remediate building flaws and contribute to the sustainability of the local environment.
For more information on thermal imaging you can visit: www.greenbldgintl.com
