Roof Maintenance in General
Waterproofing problems manifest themselves in two ways: Leakage and
entrained moisture contamination. Leakage is pretty simple, although
the leak inside the building rarely directly relates to the exact spot
on the roof, since the water flows down the slope of the roof to a spot
that is not sealed and into the building at that point. Most leaks occur
where the waterproofing is sealed or where there is a penetration of
the roof. Since most types of roof systems absorb some amount of water,
it is harder to find the exact spot of water contamination in the insulation
because it may not leak into the building until it has absorbed all
the water it can hold.
There are three types of surveys that are used to find
water in a roof. Nuclear gauges-which count neutrons, capacitance meters-which
measure resistance, and infrared-which measures heat. Both nuclear gauges
and capacitance meters are used to take spot readings on a 5’
X 5’, 10' X 10' or 20' X 20' grid on the roof. These measurements
are used to extrapolate where the water is from the readings obtained
from the gauges. These surveys are very labor-intensive and therefore
expensive. They are good for types of roofs that do not gain or lose
much solar energy and therefore, do not lend themselves to infrared.
Roof Infrared Basics
During the day, the sun radiates energy onto the roof
and into the roof substrate, and then at night, the roof radiates the
heat back into outer space. This is called radiational cooling. Areas
of the roof that are of a higher mass (wet) retain this heat longer
than that of the lower mass (dry) areas. Infrared imagers can detect
this heat and "see" the warmer, higher mass areas, during
the "window" of uneven heat dissipation.
Why Aerial Infrared
Performing infrared roof moisture surveys while standing on the roof
is not the best method because imagery from a walk-on survey is not
as useful as aerial imagery. The same laws of physics apply to both
aerial IR and on-roof IR. A dry roof, low winds and no rain are needed
on the night of the survey. However, the "window" when the
roof is radiating heat differently from wet and dry areas is longer
with aerial infrared because slight nuances of temperatures over large
areas are recognizable. A high angle of view and high resolution are
needed to produce usable imagery. We use large-format infrared cameras,
which have at least 512 x 512 staring array detectors (262,144 pixels).
From an altitude of 1,200 – 1,500 feet above the roof with over
a quarter of a million pixels, the ground resolution element is about
six inches square.
Visual photographs are taken earlier in the day or the next day. Both
visual and infrared images are used to do the analysis by overlaying
the AutoCAD drawing of the roof ‘over’ the digitized photographs
and thermographs. The drawings are created indicating areas of suspected
moisture contamination. The result is a report where visual, infrared
and AutoCAD components (printed and video) are well matched and lined-up.
Fixed-wing aerial infrared imaging provides many advantages over on-roof
- Access to multiple levels of the roof is not a problem.
- High-angle, straight down infrared images lessen reflection
High-resolution images capture large areas at once, making report
writing easier and less expensive to produce.
- Plan view allows for infrared images, visual images and
AutoCAD drawings to be reconciled closely. As a result, the report
is clear, concise and easy to understand (see Figure 4,5,6).
- Plan view imaging allows accurate marking of areas of suspect
roof moisture contamination.
- The printed AutoCAD drawings can be used on the roof to
paint areas of moisture contamination directly on the roof (after
verification), if desired.
- The trending of roof moisture becomes possible.
Aerial IR allows the building owner to buy only the report he needs
at that time.
- Further processing can be done on roof areas of specific
concern. The report components are as follows in order by cost:
- Unedited videotape. The raw videotape of the infrared flight
over the building.
- Edited videotape. An edited videotape can be made from the
original digital video.
- Printed thermographs. Printed infrared thermographs of each
roof section can be captured and printed in high-resolution.
- Aerial photographs. Printed digital and/or conventional
photographs of the roof (straight down) and site (beauty shots of
the building and property) can be printed. Note: A straight down photograph
of a roof section aids significantly in the infrared analysis, showing
stains, equipment and roof boundaries, etc.
- AutoCAD drawings. Accurate AutoCAD drawings can be made,
then printed and saved to disk
- Digital and printed report. A complete quantitative aerial
infrared roof moisture survey report would include all of the above,
printed in high resolution and saved to a CD.
The biggest advantage of aerial infrared is on roofs that are the most
difficult to image from any distance or angle. Roofs that, for instance,
have a lot of ballast, are covered with reflective coatings or for whatever
reason are impossible to image from the roof. With high-resolution,
plan view aerial imagery, slight nuances of temperature can be seen
from far enough away to actually see the pattern of heat and make a
determination of where the problems are.
Roof Real Roof Asset Management
Roof Moisture FindIR is the most popular of all the FindIR services,
because it is quick and inexpensive. See slideshow here...