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THERMALCITIES: PRACTICAL APPLICATIONS
FOR THERMAL IMAGING
To the right is a thermal image of
an old office building in Lime Street in London in winter. It is
apparent that one of the windows is emitting a lot more heat
than any of the others. This is the standard perception of what
thermal imaging can do, but it can also do much more. From helping to diagnose
medical conditions in people and animals, through preempting
failures in machines and buildings, to informing effective
business and public energy policies, over the coming weeks this
page will present a growing number of examples of how thermal
imaging can be of value. See the energy and technology
pages for more relevant information.
The current article collection on this page will be slowly revised
over the coming months. Contributions are invited from anybody
who thinks they might have relevant information of interest. Any third party
images and comments used will be marked and hyperlinked as requested.
Please see the About page for details of how to contact
thermalcities.com.
ARTICLES
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BELOW:
Aerial
thermal imaging of cities and towns
BELOW: The
case for regular aerial thermal imaging of towns and cities
HERE:
UNDERSTANDING AND DETECTING
THERMAL BRIDGES
This article is
based on material kindly
submitted by Nick Reilly of Ren Solutions
- a UK -based
thermal imaging and sustainability consulting service. Except
where otherwise stated in this section, copyright for all images
resides with Ren Solutions
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A
thermal bridge is a thermally conducting material which
penetrates or bypasses an insulation system; such as a metal
fastener, concrete beam, slab or column. Heat will flow the easiest path
from the heated space to the outside - the path with least
resistance. Very often heat will "short
circuit" through an element which has a much higher
conductivity than surrounding material, which can be described
as a thermal bridge.
Typical effects of thermal
bridges are:
- Decreased interior surface
temperatures; in the worst cases this can result
condensation problems, particularly at corners.
- Significantly increased heat
losses.
- Cold areas in buildings
Such problems need to be
identified properly first, before they can be resolved.
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A thermal bridge caused by a structural beam in a first floor
bed room
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External shot of a floor slab acting as a thermal bridge.
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Mineral wool snagged on a roof joist allows a small area of air
circulation for this bridge.
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This steel column going through the roof to a balcony above is a
major thermal bridge.
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A common problem - insulation is not installed appropriately, up
to near the eves.
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A similar problem to the left, this time with installed bat
insulation rather than roles.
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Here, the bridging is between the ceiling framing and the
plaster board on the walls.
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AERIAL
THERMAL IMAGING OF CITIES AND TOWNS
This article is based on
material from Horton
Levi Ltd and Hotmapping
Ltd who combined their skills to create a geo-rectified aerial
heat-loss survey of London. In addition to providing immediately
useful information, their survey underpins a strong case for such
surveys being conducted on a regular basis in the future. (see
below)
First off, Horton Levi Ltd,
used military specification thermal imaging equipment to capture
over 600 aerial images of London from an aircraft flying at
2,000 feet in 2000.
Known geographic reference
points in each image were then identified and the images were
rescaled so that they could then be overlaid upon standard
mapping data. The composite thermal image was then, effectively,
'georectified', as every geographic point within it,
corresponded to standard mapping data, for automatic plotting
and mapping purposes. The process is explained by Hotmapping
Limited in the column to the right.

Part of a seamless 'georectified'
thermal image from Hotmapping Ltd and Horton Levi Ltd.
Although the big London aerial
image set acquired by Horton Levi dates back to 2000 and a lot
of building, demolition, construction and maintenance has taken
place since, it still generates valuable data. The following
examples are drawn from both Hotmapping and Horton Levi's
websites and used with permission.
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How
aerial thermal imaging data is georectified (Courtesy
Hotmapping Limited)
Step
1 Formatting the image and map data ready for
georectifying.

Step
2 Using multiple Ground Control Points, individual
images are aligned with the map data.

Step
3 The rectified images are joined together to form
a seamless mosaic.

Step
4 The combined image map is projected using map
co-ordinates so that it can overlay the map data in GIS
(Geographic Information Systems = Mapping) software.

A case study of how Hotmapping
has georectified Horton Levi's thermal imagery for
Chester-le-Street District Council, can be accessed here. |
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The above thermal
image has been both georectified and then subjected to further
image analysis so that an average identified temperature has
been colour coded for each known address. The final output is
shown to the right. Note how the pattern of streets confirms the
pictures are related.
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The image to
the bottom left is part of Horton Levy and Hotmapping's
Heat Loss Survey for the London Borough of Haringey.
Horton Levy's thermal image set was processed by
Hotmapping to provide a colour code to 65,000 buildings.
You can click here
to view the complete survey on-line. And here
to get to a Horton Levi web page to access copies of
newspaper articles about this.
Note. Although
Thermalcities is of the opinion that
cities would benefit from regular updated aerial thermal
surveys (Say every 5 years) Policy makers need to realise
the limitations as well as benefits of such data.
Due to how
the technology works, and as intimated by the colour-code
on the right, the best it can do, is to indicate
areas for further review. |
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Source = Horton
Levi Ltd |
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The
case for regular aerial thermal imaging surveys of cities
Regular, repeated georectified
surveys of towns and cities will allow many different types of
analysis to be conducted, which, in turn, can inform everybody
from people living in flats and houses, through facilities
managers and architects, to policy makers.
Regularly updated aerial
surveys of this kind can provide, effectively, for many
different kinds of time series analyses. The fact that climactic
conditions will vary from over-flight to over-flight can be
accommodated in part by introducing known, ground-level control
points.
Thereafter, with
georectification, beyond the simple point-by-point analysis
available from a single over-flight, it becomes possible, for
example, to: benchmark how, within different classes of
buildings, some might have improved thermally, better than
others, and also to evaluate changes in aggregated thermal data
for assorted collections of buildings.
Aggregated housing-heat data
will, for example, be much easier than a single dwelling to
calibrate against known 'environmental control points'.
Meaningful time series analyses can be run. These, in turn,
could be used to review the relative impact, over time, of
different regional energy-efficiency policies, practices and
technologies.
To the right is another
image from Horton Levi Ltd. This is of The Royal Free Hospital,
London. The clearly distinguishable hot spots aid its property
maintenance programme. |
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Copyright for all images and text resides with Steve Lowe/ Thermalcities,
except where otherwise stated.
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