Thermal Imaging. By Colin Pearson Head of Condition Monitoring BSRIA

Size: px

Start display at page:

Download "Thermal Imaging. By Colin Pearson Head of Condition Monitoring BSRIA"

Debra Cox
5 years ago
Views:

1 Thermal Imaging In Association with Anderson Mechanical Services Loughgall, Armagh BT61 8HZ By Colin Pearson Head of Condition Monitoring BSRIA

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

3 Today s Presentation Current Building Regulations Testing vs. Assured Design Thermal Imaging Basics Buildings Benefits Acoustic Testing Basics Benefits Training and certification The future

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?

5 Testing vs. Assured Design No matter how good the design and the Building Inspector, there is no way to be sure of thermal insulation or noise isolation without testing!

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

7 Thermal Imaging - Basics Infrared Material properties Imaging systems Benefits Common faults Survey method Understanding results

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

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 ) Intensity of radiation depends on temperature (Boltzman) = T 4 (Stefan s Law) = 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)

9 The infrared spectrum UV Infrared TV & radio TV & radio X-rays Visible Microwaves AM radio.1nm 1nm 10nm 100nm 1µm 10µm 100µm 1mm 10mm 100mm 1m 10m 100m 1km Wavelength Visible Infrared SW LW 100nm 1µm 10µm 100µm 1mm

10 Important material properties Emittance Transmittance Reflectance Background temperature Size Distance Thermal capacity

11 Emittance, reflectance & transmittance r + a +t =1

12 1960s-70s systems Imaging systems

13 1970s systems Imaging systems

14 Thermal imaging cameras

15 Imaging systems 21 st Century systems Low noise images - 80 mk thermal sensitivity High definition images 640x480 pixels resolution, 307,200 picture elements Full speed 50 Hz images High usability with voice and PDA interfaces Sophisticated analysis software

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

17 Building fabric thermography

18 Building fabric thermography

19 Defects Cold bridging Missing insulation Air leakage Slipped insulation

20 27.0 C Gaps in insulation C

21 insulation gaps - walls

22 Thermography locates air leakage behind plasterboard 31.0 C C 26

23 Gaps in insulation 5.0 C C

24 Cold bridges - steelwork 26.5 C SP SP02 SP03 SP C

25 Cold Bridge location C C

26 Air leakage location 36.0 C C

Good structure U value 0.35 20 18 19.1 18.

27 Good structure U value Temperature, C Block Air Plaster Insulation Brick Distance, mm Cavity Air 0.0

28 Poor structure U value Block Brick Temperature, C Air Plaster Missing Insulation Distance, mm - 5 Air

Mortar in poor structure U value 1.41 20 Temperature, C 18 16.3 16 14 12 10 8 6 4 Air Plaster 14.

29 Mortar in poor structure U value Temperature, C Air Plaster 14.5 Mortar Block Dewpoint of 20 C air at 80% rh = 16.5 C Missing Insulation 6.4 Brick Air Distance, mm

30 Mortar in poor structure U value 1.41

31 Chimneys / Flues

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 of 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 CO 2.

33 Note: this is inside of building but outside was warmer so the poorly insulated areas show up as warm Extract from the thermographic report - before

34 Building fabric thermography Construction defects

35 Building fabric thermography Construction defects Remedial action

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); or 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

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

38 What needs to change? Certification of competence Define acceptable limits Show how to prove compliance

39 Certification of competence PCN Level 2 Civil Possible House Thermographer certification

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

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

42 Critical surface temperature factor Defined by risk of condensation and mould Surface temperature factor, f Rsi Proportion of temp. diff. across fabric rather than internal boundary layer T si T e T i - T e Critical surface temperature factor f CRsi f Rsi = Surface temperature factor that will lead to condensation or mould growth in lowest design temperature 0.75 often used

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

44 Surface temperature and area measurement Temperature measurement is common feature of 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

45 Conditions and equipment Suitable conditions, equipment and repeatable method required Follow existing standard eg BS EN 13187:1999, Thermal Performance of buildings Qualitative detection of thermal properties in building envelopes Infrared method (ISO 6781:1983 modified)

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

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

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 obscured, eg by false ceilings.

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 Example

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 CO 2 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

51 Conclusions There is a practical, repeatable semi-quantitative method of assessing thermal insulation performance It is being used by thermographers in England and other countries worldwide It may be used to show compliance with Building Regulations Infrared cameras are being produced with software to identify defective areas

52 Contact Anderson Mechanical Services 77B Main Street Loughgall, Armagh BT61 8HZ Tel: (NI) Tel: (ROI)

Infrared Energy Report

Infrared Energy Report John Jones 5 Anytown Rd. Anytown, NJ 08892 Prepared by: www.njamerispec.com Richard Roshak 3 Derbyshire Lane Somerset, NJ 08873 njamerispec@verizon.net 732-356-6840 Sunday, September