SLIDE 1 Thermal Imaging
By Colin Pearson Head of Condition Monitoring – BSRIA
In Association with Anderson Mechanical Services Loughgall, Armagh BT61 8HZ www.andersonmechanical.net Email: info@andersonmechanical.net
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SLIDE 2 My background
- Head of Condition Monitoring at Research and Specialist Consultants, BSRIA.
- PCN Level III thermographer
- Chairman of the UK Thermography Association
- Fellow of BINDT
- Member of CIBSE
- Associate Member Institute of Acoustics
- 14 years experience in building thermography
- 5 years experience in acoustic testing
- Chairman Thermography Training and Certification Working Group
- BSI and ISO CM & NDT committees.
- 10 years in research & consultancy for farm buildings
- BSc Environmental Engineering
- 5 years with mechanical and electrical contractor
- 4 years with lighting manufacturer
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SLIDE 3 Today’s Presentation
- Current Building Regulations
- Testing vs. Assured Design
- Thermal Imaging
Basics
Buildings
Benefits
Basics
Benefits
- Training and certification
- The future
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SLIDE 4 Current Building Standards (Regulations)
- The Building Control Act 2007 Ireland (Building Standards)
- Technical Guidance Documents (Approved Documents)
- Parts A to M (L: Conservation of Fuel & Energy, E: Sound)
- Specifies the minimum acceptable standards
- No testing specified
- Are these providing the right quality of buildings?
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SLIDE 5 Testing vs. Assured Design
- No matter how good the design and the
Building Inspector, there is no way to be sure
- f thermal insulation or noise isolation without
testing!
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SLIDE 6 Pre-Completion Testing
- Thermal insulation problems don’t show until
it gets cold
- Acoustic problems don’t show until the
neighbours are noisy
- The only way to be sure is to test!
- Testing provides quality assurance
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SLIDE 7 Thermal Imaging - Basics
- Infrared
- Material properties
- Imaging systems
- Benefits
- Common faults
- Survey method
- Understanding results
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SLIDE 8 Infrared radiation
- Discovered in 1800 by William Herschel
- “There is a heating effect from solar radiation beyond the
red zone of the visible spectrum”
- Detection improved by thermoelectric thermometer
(Nobili – 1830)
- The radiated energy is due to molecular vibration
(Maxwell theory of EM radiation - 1873)
- Intensity of radiation depends on temperature (Boltzman)
= T4 (Stefan’s Law) = 5.6686 x 10 –8 Wm-2 K-4
- All objects above absolute zero emit IR
- Wavelength of peak radiation depends on temperature
(Wien’s law)
- Quantum Hypothesis (Planck – 1906)
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SLIDE 9 UV AM radio TV & radio TV & radio Microwaves Infrared Visible X-rays
1m 10m 100m 1km 100mm 10mm 1mm 10µm 100µm .1nm 1nm 10nm 100nm 1µm
Wavelength 100nm 1µm 10µm 100µm 1mm Infrared Visible SW LW
The infrared spectrum
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SLIDE 10 Important material properties
- Emittance
- Transmittance
- Reflectance
- Background temperature
- Size
- Distance
- Thermal capacity
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SLIDE 11
Emittance, reflectance & transmittance
r + a +t =1
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SLIDE 12 Imaging systems
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SLIDE 13 Imaging systems
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SLIDE 14
Thermal imaging cameras
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SLIDE 15 Imaging systems
- 21st Century systems
- Low noise images - 80 mK
thermal sensitivity
640x480 pixels resolution, 307,200 picture elements
- Full speed 50 Hz images
- High usability with voice and
PDA interfaces
software
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SLIDE 16 Benefits of thermal imaging
- Quick inspection
- Results clearly shown in pictures
- Shows precise location of fault
- Shows severity of fault
- Shows compliance with regulations
- Improves quality of products
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SLIDE 17
Building fabric thermography
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SLIDE 18
Building fabric thermography
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SLIDE 19 Defects
- Cold bridging
- Missing insulation
- Air leakage
- Slipped insulation
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SLIDE 20
Gaps in insulation
16.0°C 27.0°C 16 18 20 22 24 26
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SLIDE 21
insulation gaps - walls
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SLIDE 22 Thermography locates air leakage
25.5°C 31.0°C 26 27 28 29 30 31
behind plasterboard Anderson Mechanical Services
SLIDE 23 Gaps in insulation
5.0°C
2 4
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SLIDE 24 Cold bridges - steelwork
21.2°C 26.5°C 22 23 24 25 26
SP01 SP02 SP03 SP04
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SLIDE 25 Cold Bridge location 2
30.0°C 36.0°C 30 32 34 36
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SLIDE 26 Air leakage location
30.0°C 36.0°C 30 32 34 36
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SLIDE 27 19.1 18.4 15.8 3.9 2.8 0.2 0.00 2 4 6 8 10 12 14 16 18 20 50 100 150 200 250 300 Distance, mm Temperature, °C
Block Brick Insulation Cavity Air Air Plaster
Good structure U value 0.35
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SLIDE 28 18.2 17.1
0.8 + 0.00 2 4 6 8 10 12 14 16 18 20 50 100 150 200 250 300 Distance, mm Temperature, °C
Block Brick Missing Insulation Air Air Plaster
Poor structure U value 0.85
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SLIDE 29 16.3 14.5
6.4
0.8 + 0.00 2 4 6 8 10 12 14 16 18 20 50 100 150 200 250 300 Distance, mm Temperature, °C
Block Brick Missing Insulation Air Air Plaster
Mortar in poor structure U value 1.41
Mortar
Dewpoint of 20°C air at 80% rh = 16.5°C
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SLIDE 30
Mortar in poor structure U value 1.41
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SLIDE 31
Chimneys / Flues
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SLIDE 32 Case study 1
- retail building, 130x75 metres and 6-9 m high
- interface detail left a 73mm strip uninsulated
- =30 square metres of cladding with a U value
- f 3.5W/m²K instead of 0.35W/m²K.
- would require an extra 2kW of heating
- nearly 8000 kWh a year extra heating
- cost of over €1000 a year
- generating nearly 4000kg of additional CO2.
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SLIDE 33
Extract from the thermographic report - before
Note: this is inside of building but outside was warmer so the poorly insulated areas show up as warm
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SLIDE 34 Building fabric thermography
defects
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SLIDE 35 Building fabric thermography
defects
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SLIDE 36 Building Regulations Part L2 (2002)
“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);
- r they should obtain a certificate or declaration to that effect
from a suitably qualified person. Such certificates or declarations would state: a) that appropriate design details and building techniques have been used or b) that infra-red thermography inspections have shown that the insulation is reasonably continuous over the whole visible envelope”
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SLIDE 37 But are the buildings acceptable?
- Normally rely on skill and experience of
thermographer
- No guidance on what is acceptable
- Standards and Guides do not set criteria
- Proposals in England and Wales for
certification by a competent thermographer
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SLIDE 38 What needs to change?
- Certification of competence
- Define acceptable limits
- Show how to prove compliance
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SLIDE 39 Certification of competence
- PCN Level 2 Civil
- Possible ‘House Thermographer’ certification
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SLIDE 40 How do you show compliance?
- Show thermal anomalies
- Differentiate between real thermal anomalies
and confounding factors
such as localised differences in air movement,
reflection and emissivity
- Quantify affected areas and their severity
- State whether the anomalies and the building
thermal insulation are acceptable
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SLIDE 41 Approach
- Select critical temperature factor
- Select acceptable defect area limit
- Measure surface temperature difference
caused by each anomaly
- Measure or estimate area of the defects
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SLIDE 42 Critical surface temperature factor
- Defined by risk of condensation and mould
- Surface temperature factor, fRsi
Proportion of temp. diff. across fabric rather than internal boundary layer
Tsi – Te Ti - Te
- Critical surface temperature factor fCRsi
Surface temperature factor that will lead to condensation or mould growth in lowest design temperature
0.75 often used
fRsi =
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SLIDE 43 Allowable area
- Must maintain high standards without
alienating construction industry by failing too many buildings
- 0.1% is suggested as suitable for large
commercial and retail buildings
- This leads to about one failure in six
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SLIDE 44 Surface temperature and area measurement
- Temperature measurement is common feature
- f a thermographic survey
- Area measurement is often a feature of
analysis software requiring:
Object distance Angular field of view Setting threshold temperature in software Pixel counting Computation of area below threshold temperature
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SLIDE 45 Conditions and equipment
- Suitable conditions, equipment and
repeatable method required
– eg BS EN 13187:1999, Thermal Performance of buildings – Qualitative detection of thermal properties in building envelopes – Infrared method (ISO 6781:1983 modified)
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SLIDE 46 Method
- Internal survey usually best
- Requires image of every anomaly
image square to any features of the wall or roof. viewing angle perpendicular to surface imaged interfering sources of infrared radiation such as
lights, heat emitters, electric conductors, reflective elements minimised
- Requires calculation of building surface area
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SLIDE 47 Analysis
- Adjust each image for distance, background temp &
emissivity
- Place area analysis tool to enclose anomaly
- Set threshold temp. for area according to internal &
external temp.
- Use pixel counting tool and calculation from image
parameters to find area below threshold
- Repeat for all anomalies
- Use summary table to add all areas below threshold
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SLIDE 48 Limitations
- This method may not be suitable for:
Heavyweight structures, particularly where the
main insulating element is near the outside surface
Buildings where much of the internal surface is
- bscured, eg by false ceilings.
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SLIDE 49 Energy efficiency survey
- Heat loss through structure can be shown by
surface temperature
- Calculated from temperature difference
across boundary layer
- Depends on constant boundary layer
resistance and known internal temperature
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SLIDE 50 Impact of introducing testing
Projection, because we don’t have it yet
- Improved average thermal performance about
200kWh/yr for a house, or 37kg CO2 emissions
- Extra cost of construction €0 just applying best practice
- Extra cost of testing €15/house based on 1/10 sample
- Extra cost of remedial action
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SLIDE 51 Conclusions
- There is a practical, repeatable semi-quantitative
method of assessing thermal insulation performance
- It is being used by thermographers in England and
- ther countries worldwide
- It may be used to show compliance with Building
Regulations
- Infrared cameras are being produced with software
to identify defective areas
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SLIDE 52 Contact
Anderson Mechanical Services 77B Main Street Loughgall, Armagh BT61 8HZ www.andersonmechanical.net Email: info@andersonmechanical.net Tel: +44 28 3889 1320 (NI) Tel: 048 3889 1320 (ROI)
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