< Previous20 Fall 2024 • Ontario Building Envelope Council FEATURE n n n By David De Rose & Anthony Lukes, Synergy Partners & Greg Hildebrand, EXP Services Compressed Air Frost Spray (CAFS) Testing I nsulating Glazing Units (IGUs) have long been a staple in new construction and building renewal projects. Predicting IGU failures is a challenge for building owners, contractors, and consultants alike, with fogging often only becoming apparent after IGU seals have already failed. Improv- ing IGU performance and extending their service life are necessities for resilient and sustainable construction. This article ex- plores a simple in-field or in-plant test meth- od for screening IGUs descriptively named the Compressed Air Frost Spray (CAFS) test. The CAFS test allows testers to screen many IGUs in a short period of time in a cost-effective manner. IGUs are typically composed of two (or more) glass panes separated by a spacer with desiccants. The units are held together with a combination of sealants that make up the primary and secondary seals and the gas space between the glass panes is filled with air or inert gases such as argon to improve thermal and acoustic performance. There are several potential issues with IGU fabrication that may lead to premature failure. These issues may be related to defi- ciencies during the manufacturing process. IGU fabrication techniques could be al- tered to address deficiencies and improve performance/durability where IGU issues are detected early in the fabrication process. IGU failure becomes apparent when con- densation or fog appears between the glass panes. At the point that condensation or fog appears between the glass panes, the seals will likely have already been compromised for some time. The insulating properties of the unit may be reduced before visual signs of fogging or condensation between panes becomes evident. Early failure detection can help maintain energy efficiency and help owners budget/plan for future replacement. Refined dewpoint testing of IGUs such as described in ASTM E576 utilizes special- ized equipment to determine temperatures at which fogging occurs (within +/- 5 °C). Refined dewpoint testing of IGUs, while reliable, is costly and is not always feasible for rapid, in-plant or in-field assessments of many units in a short time frame. The CAFS test method was developed by the late Greg Hildebrand. Greg co-chaired the CSA A440 Series Technical Committee that sets fenestration standards. He also served as the Canadian Chair of NAFS (North American Fenestration Standard) as well as working on many committees/task groups with the ASTM (American Society of Testing Materials). The CAFS test is a simple, quick and cost-effective method for screening many IGUs in a short time frame. The results of the CAFS test help to identify potential IGU issues prior to visual deterioration. The test can be used early in a project to diagnose potential fabrication issues that may otherwise lead to internal fogging or to assist with service life planning in existing buildings. The following materials are required to complete the test: •10 oz cannisters of compressed air. The number of cannisters of compressed air is dependent on the number of IGUs to be tested. In our experience, one cannis- ter of compressed air can test 4-6 IGUs; •A T-type thermal couple connected to a data-logger device; and •An ice scraper and cloth. The objective of the test is to apply a temperature of ~-50 °C to a small area on the surface of the IGU. This is achieved by applying the liquid from an inverted com- pressed air cannister to the surface of the IGU. The thermocouple and data logger are used to record the temperature of the liquid from the compressed air cannister. The procedure for completing the test on a double glazed IGU is as follows: A Cost-Effective Method to Screen Insulating Glazing Unit Quality and Durability Applying compressed air fluid to an IGU. A thermocouple connected to a data logger is attached to the nozzle of the compressed air cannister to measure fluid output temperature. Photos and graphics courtesy of Anthony Lukes.Pushing the Envelope Canada 21 n n n FEATURE •Connect a thermocouple to the nozzle of the compressed air canister to check output temperature; •Hold the compressed air cannister upside down, approximately 25 mm away from the IGU; •Apply compressed air to the IGU in four slow, circular revolutions (ap- proximately 100 mm in diameter) with each revolution lasting about one second. This constitutes one cycle. This can be done on either side of the IGU (Surface 1 or 4). Gloves should be worn to mitigate liquid from con- tacting the testers skin which may otherwise cause burns; •Allow time for the compressed air to evaporate after each cycle. Test adjacent IGUs simultaneously during this period, typically grouping four IGUs together. Apply the four circular revolutions to the other three IGUs sequentially; •Once all four IGUs have completed the first cycle, enough time will have passed for frost to develop on the first IGU; •Repeat the procedure for four cycles (16 total revolutions per IGU); and •After completing all cycles, use a frost scraper and cloth to remove the frost from the IGU surface. A failed IGU is identified by the pres- ence of fog or condensation between the glass panes (i.e., surfaces two and/or three). For triple-glazed IGUs, both the interior and exterior surfaces must be tested to check for moisture within either gas space. This test can determine if the dewpoint of an IGU is below -50 °C which would indicate that there are no imminent signs of IGU failure. A failure during this test i.e. the presence of moisture in the cavity at -50 °C, suggests a potential issue or a reduced ex- pected service life for the IGU. If fogging or condensation are detected in the IGUs dur- ing screening, more refined dewpoint testing with more specialized equipment can be completed to refine the dewpoint temper- ature between glass lites to within +/- 5 °C. In the 1980s, the Sealed Insulating Glass Manufacturers Association (SIGMA) began a study to track the performance of 2,400 IGUs installed in various buildings and cities in the USA. Jim Spetz, their consultant who carried out field dewpoint testing developed a qualitative method of determining the relationship between IGU dewpoint tem- peratures to likelihood of fogging (see Fig- ure 2). Dewpoint temperatures of IGU can also be tracked in subsequent readings from year-to-year to track tends to more accurate- ly extrapolate time to fogging.1 CAFS testing has been utilized to screen IGUs in both new construction projects and on existing buildings. At a new construction project for an Insti- tutional project, CAFS testing was utilized to screen recently installed large triple-glazed IGUs. No failures were observed, and the results provided confidence to the Consult- ant and Owner that there are no manufac- turing issues with the new IGUs that could lead to premature failures. CAFS testing has also been utilized on various existing buildings to screen existing IGUs. At one large residential building in Toronto, CAFS testing revealed failures in all the units that were tested despite no visible signs of fogging prior to testing. Ex- isting IGUs were approximately 40 years of age at the time of testing. This testing was used to help owners plan for IGU or window replacement. A frost scraper is used to remove frost from the IGU following the test. A successful test is identified when no fog, condensation, or frost is observed between the glass panes. Figure 2: The Spetz Method for qualitatively determining time-to-fogging.22 Fall 2024 • Ontario Building Envelope Council FEATURE n n n At another large residential building in Toronto, CAFS testing was completed on over 45 IGUs in a few hours. Existing IGUs were approximately 30 years of age at the time of testing. No failures or imminent signs of failure were observed during the testing. The results of the tests helped the owners defer IGU replacement in their Re- serve Fund Study. The CAFS test offers significant benefits in screening both new and existing IGUs. It’s simplicity, cost-effectiveness and rapid re- sults make it an invaluable tool for detecting potential IGU issues. Building owners, IGU manufacturers, and consultants can ef- fectively assess IGU quality or make more informed decisions with respect to IGU re- placement planning.n David De Rose, M.A.Sc., P.Eng., BSS is a Principal for Synergy Partners. He is the Chair of the CSA A440.6 subcommittee that deals with high-exposure Fenestration Installation and is a voting member for CSA-S478 Stan- dard of Building Durability. David is currently a part-time Professor at Toronto Metropolitan University and at the University of Toronto. Anthony Lukes, B.Eng., is a Project Man- ager for Synergy Partners. Anthony has worked on over 200 projects over a nine-year career in building Science and Restoration. He special- izes in building enclosures and has extensive experience ein the evaluation and field testing of building façades. Greg Hildebrand, M.Sc.Eng., CET, was the head of the façade engineering group at EXP Services and a leading expert in the Canadian window and door industry. Greg chaired or sat on committees for CSA A440, North Amer- ican Fenestration Standard (NAFS), and the American Society for Testing and Materials (ASTM) during his career. Figure 1: A sample of data from the data logger tracking fluid temperature per test. REFERENCE: 1.G.R. Torok. Predicting Time-to-Fogging of Insulating Glass Units. 11th Canadian Conference on Building Science and Technology. Banf, Alberta, 2007.Pushing the Envelope Canada 23 Kestrel Court: Case Study of a Successful Deep Energy Retrofit By Jonathan Smegal, RDH Building Science T wo-thirds of the buildings that exist today will still exist in 2040,1 which means many buildings will require a deep energy retrofit to meet CO 2 reduction goals in Canada, the United States, and the rest of the world. This case study considers Kestrel Court: a cold-climate, net-zero energy ready (NZER) project located in London, Ontario. A NZER building can, with the addition of solar panels or other on-site renewable energy technologies, achieve net-zero energy performance annually. The results of this case study provide insight into deep energy retrofit strategies that could contribute to meeting national and global energy targets. A report (linked at the end of this article) provides additional details, including the mechanical systems strategies used for this project. The Kestrel Court project received in- spiration from the Local Energy Efficiency Partnerships (LEEP) program and received funding through the Office of Energy Re- search and Development (OERD) at Nat- ural Resources Canada (NRCan). PROJECT BACKGROUND The Kestrel Court student townhomes at Fanshawe College were constructed in 1993 and represent construction practices of their era (see Figure 1). Fanshawe College proposed deep energy retrofits of 11 units (three townhouse build- ings) using five different exterior insulation systems and six HVAC packages to achieve NZER levels. This project was completed by Fanshawe College in the fall of 2023. Sig- nificant industry in-kind support was provid- ed for the enclosures, windows, and HVAC equipment by several manufacturers who participated in the LEEP for Renovations initiative in London in 2017-2018. Key objectives of the Kestrel Court pro- ject included the following: Figure 1: Kestrel Court pre-retrofit student townhomes constructed in 1993. Photos courtesy of Jonathan Smegal. n n n FEATURE24 Fall 2024 • Ontario Building Envelope Council •Achieve net-zero energy ready measured performance annually on the three townhome blocks working with five dif- ferent insulation manufacturers; •Reduce greenhouse gas emissions as much as possible; and •Provide technology transfer to the industry so others may also benefit from the learning acquired on the project. BUILDING IMPROVEMENTS In a deep energy retrofit, it is critical to create a highly insulated, airtight enclosure. Enclosure improvements are intended to control the heat loss/heat gain between the interior and exterior to reduce the energy required for space conditioning. The Kestrel Court townhome enclosures were retrofit using a combination of exterior insulation strategies, an exterior air barrier system, and all new, high-performance win- dows and doors. ABOVE-GRADE WALL RETROFIT STRATEGIES Five insulation manufacturers and five specific approaches were used for the above- grade wall assembly energy retrofits. Mod- elling conducted for the study determined that the insulation levels should be R-60 in the attic, R-28 (effective) in the above-grade walls, and R-20 for the full-height basement insulation. The following sections will de- scribe the five approaches taken and the insulation manufacturers who participated in the project. 1. BASF wall system Following the removal of cladding and insulating sheathing, horizontal 2x3 strap- ping was installed on the exterior of the 2x4 framing and closed-cell spray polyurethane foam (ccSPF) was installed five inches (127 mm) in depth from the interior drywall to the 2x3 strapping. Two inches (50 mm) of Neopor ® EPS was installed against the horizontal strapping and covered with a water-resistant barrier (WRB), 1x4 vertical strapping, and cladding (see Figure 2). 2. Dryvit wall system The Dryvit Outsulation ® MD assembly was the only retrofit strategy that did not require the removal of the existing masonry on the first storey. Exterior gypsum was in- stalled over the framing in locations where the vinyl cladding had been removed. A manufacturer formulated fluid-applied air/ water barrier was installed over the masonry and exterior gypsum and made continuous with all adjoining assemblies and penetra- tions. EPS foam 3.5 inches (89 mm) thick was installed over the air/water barrier, and an EIFS finish coat with varying impact pro- tection based on height was installed over the surface of the EIFS (see Figure 3). 3. Owens Corning wall system The Owens Corning assembly is a sys- tem of exterior XPS CodeBord® insulation and sill gasket membranes for air control installed directly to the exterior face of the framing without sheathing. Two layers of two inch (50 mm) XPS were installed with the interior layer taped and sealed. On the exterior of the XPS insulation, 1x4 strapping was installed through the exterior insulation for cladding attachment (see Figure 4). 4. Plasti-fab Insulspan® wall system The Plasti-fab Insulspan ® wall system included an initial layer of one inch (25 mm) poly-faced EPS DuroFoam with all joints taped and installed directly against the framing as the primary air control lay- er of the system. A nailbase panel with 3.5 inches (89 mm) of EPS foam bonded to an exterior OSB facer was secured to the structure. A WRB was installed over the OSB for rainwater protection and 1x4 strapping was installed to provide a drained and vented cavity for cladding at- tachment (see Figure 5). 5. ROCKWOOL wall system The ROCKWOOL wall system includ- ed the removal of the existing insulating sheathing and installation of new OSB sheathing installed over the framing. A Dorken self-adhered WRB was installed over the OSB sheathing. ROCKWOOL ComfortBoard 110 was installed in a four inch (102 mm) layer, with exterior vertical 1x4 strapping installed on the exterior of the insulation to provide a drained and vented cavity, and cladding installed to the vertical strapping (see Figure 6). Figure 3: Dryvit wall system with finished EIFS deep energy retrofit enclosure. Figure 2: BASF first-floor insulation in progress (second floor is original). FEATURE n n nPushing the Envelope Canada 25 FEATURE n n n BELOW-GRADE ENCLOSURE For the project’s below-grade retrofit strategy, 2 pcf ccSPF was installed against the interior of the concrete foundation wall as air, vapour, and thermal control. The ccSPF was continuous behind the basement framing against the concrete, and in the rim joist. The basements in every unit were constructed in the same way (see Figure 7). ENCLOSURE AIRTIGHTNESS AND MONITORING All the units were airtightness tested prior to renovations and again following construc- tion. After the renovations, all units met and exceeded the CHBA required airtightness criteria for the Net-Zero Energy Ready la- beling program of 1.5 ACH at 50 pascals. Moisture levels in the enclosures are be- ing monitored using relative humidity, and wood moisture content sensors placed at various locations within the enclosure sys- tem. After the installation of an effective air control layer and exterior continuous insulation, each wall system’s risk of mois- ture condensation and accumulation was reduced. Preliminary data analysis following the first winter indicates that the wall assem- blies have no elevated moisture levels or risk of moisture accumulation. Figure 5: Plasti-fab Insulspan® wall assembly during installation. Figure 4: Owens Corning exterior insulation being installed with strapping.26 Fall 2024 • Ontario Building Envelope Council SUMMARY A NZER retrofit to three townhouses at Fanshawe College’s Kestrel Court was implemented to reduce energy consump- tion and reduce greenhouse gas emissions. The project’s high energy performance was achieved using four key strategies: exterior continuous insulation, improved airtight- ness, higher performance windows and doors, and upgraded mechanical systems. NRCan will continue to share the valu- able information gained during this project related to all aspects of design, and the measured performance of the enclosure and HVAC equipment, through further case studies and articles such as this one. The author’s recorded presentation and full report of the case study can be accessed here: https://www.rdh.com/resource/net- zero-ready-deep-energy-retrofits-kestrel- court-case-study/. n Based in Waterloo, Ontario, for nearly 20 years, Jonathan Smegal is an associate and senior building science consultant at RDH. He leads projects related to laboratory research, forensic analysis of building failures, litigation, hygrother- mal modeling, and field monitoring of building enclosure performance. As a researcher, he is an author on multiple peer-reviewed papers and has frequently shared his work through industry publi- cations, webinars, and speaking events. Figure 8: Spray foam installed against the interior of the foundation wall.Figure 6: ROCKWOOL deep energy retrofit wall assembly. REFERENCE: 1.International Energy Agency (IEA), “Technology and Innovation Pathways for Zero-carbon-ready Buildings by 2030: Introduction,” https://www. iea.org/reports/technology-and-in- novation-pathways-for-zero-car- bon-ready-buildings-by-2030/intro- duction. Accessed December 7, 2023. FEATURE n n nPushing the Envelope Canada 27 From Roof Collapse to Remediation: Understanding RAAC in Ontario’s Buildings By Brandon Gemme, Leading Edge Building Engineers, Ltd T he use of Reinforced Autoclaved Aerated Concrete (RAAC) has been a contentious topic in Ontario. In November 2023, the Ministry of Education issued a memorandum to the Directors of Education requesting all school boards “im- plement an investigation, assessment, and management strategy for RAAC within their buildings”1 in response to the 2018 partial collapse of a UK school roof constructed with RAAC panels, prompting the closure of 104 similar schools. More recently, the Ministry of Infrastructure announced that it would be closing the Ontario Science Centre as of June 2024, with one of the major justifi- cations for the closure being the condition of the RAAC roof panels.2 Some have criticized the decision to close the Ontario landmark, pointing out that the engineering report pre- pared by Rimkus identifies only one RAAC roof panel as being in critical condition and an additional six per cent as high risk. 3 Re- gardless of your opinion on the closure, RAAC is an important topic that merits fur- ther discussion and awareness. To assist building owners and restora- tion professionals working with RAAC, this article will provide a brief history of RAAC construction in Ontario, including com- monly used products, describe the primary durability concerns associated with RAAC, explain how to identify RAAC structures in existing buildings, and provide some recom- mendations on the maintenance, repair and replacement of RAAC structures. WHAT IS RAAC? The composition of RAAC varies slight- ly by product, but it is typically comprised of a mixture of sand, gypsum, lime, Portland cement, water, and aluminum powder.4 It is fabricated as panels in factories and cut to the desired structural shape, typically as masonry blocks, roof planks, wall panels, or floor units. Once the panels are molded and cut into the desired shape, the mixture is heated and cured in high pressure steamed autoclaves. The product was first developed in Sweden in the 1930s, and although the use of RAAC is more common in Europe, the only RAAC sold to the Ontario market goes by the brand name of “Siporex,” which was manufactured by Domtar at their Montreal Plant from 1955 to 1972. Other RAAC prod- ucts include Durox, Celcon, Hebel, Ytong, Aircrete, and Theramlite, some of which are now being imported into parts of Can- ada. Siporex panels used conventional steel reinforcement, coated with cement latex coating, to provide tensile and compressive strength to the panels. The product became popular in Canada due to its good insulating properties, which allowed for insulation to be omitted from roof assemblies, acoustical properties, and lightweight nature, allowing for ease of construction, and was mainly used in schools, hospitals, commercial, and light industrial buildings. 5 Although it is called concrete, RAAC differs from conventional concrete in that it has different materials and physical proper- ties than conventional concrete. The alum- inum powder reacts with water and lime to create hydrogen gas, which creates uniform air bubbles throughout the concrete. These air bubbles give the concrete the appearance of looking like a sponge and significantly re- duce the weight of RAAC to approximately 30 per cent of conventional concrete.6 These air bubbles also reduce strength of RAAC, as well as its ability to bond to steel reinforce- ment. RAAC does not use coarse aggre- gate, which also contributes to its reduced strength.7 RAAC DURABILITY CONCERNS Prior to the 2018 collapse, a string of RAAC roof panel failures occurred in the UK in the 1980s, affecting panels initial- ly installed in the 1960s.2 This temporarily halted the production of RAAC products in the UK and led to significant research being conducted in the early 1990s. Schools and other public building owners are being tasked with implementing a management strategy to address the safety concern posed by RAAC. The primary durability concerns associat- ed RAAC construction are listed next: This is what Reinforced Autoclaved Aerated Concrete (RAAC) looks like. 9 n n n FEATURE•RAAC has an effective service life of 30 years. 8 Given that RAAC production in Ontario was stopped in 1972, all RAAC panels currently in place in Ontario are well beyond the end of their expected service life and are due for replacement. •The porous nature of RAAC makes it highly susceptible to moisture ingress and carbonation. This vulnerability leads to moisture-related degradation and concrete carbonation effects such as shrinkage, sulfate attack, and leaching of cement hydrates.4 As such, all RAAC requires exterior weather protection. •The porous nature also compromis- es the alkaline protective layer that shields steel reinforcement within concrete, making it prone to corrosion from rainwater penetration and car- bonation. To mitigate this issue, steel reinforcement in RAAC is typical- ly coated with bituminous or cement latex coatings. However, assessments have revealed corrosion even in areas where these coatings appear visually intact, raising concerns about their long-term effectiveness.7 Corrosion of the steel reinforcement can occur without apparent cracks or spalling oc- curring on the exterior of the RAAC due its high porosity and low compres- sive strength. 8 •The low modulus of elasticity of RAAC causes it to undergo permanent creep de- flection when subjected to loading. This increases the likelihood of water ponding on roofs, which further increases loading and likelihood of moisture infiltration. This makes RAAC roof panels particu- larly susceptible to failure. ASSESSMENT AND MANAGEMENT OF RAAC The first step in identifying RAAC panels in Ontario buildings is to look at the age of the building. As noted previously, RAAC was only sold in Ontario from the mid-1950s to mid- 1970s; therefore, buildings built outside of this range are unlikely to have been constructed with RAAC. Following this preliminary step, RAAC can be visually identified as follows: •Size: Siporex floor and roof panels were typically manufactured to be 457 mm (18”) wide, 76 mm to 254 mm (3” to 10”) thick, and lengths up to 6.1 m (20 ft). Wall panels are typically 457 mm (18”) wide or 1,524 mm (60”) wide, 127 mm to 254 mm (5” to 10”) deep, and up to 6.1 m (20 ft) long. Masonry blocks are typically 229 mm x 457 mm (9” x 18”) and available in thickness from 75 mm to 254 mm (3” to 10”). •Shape: RAAC panels typically have a chamfer or V-shaped groove at the edge of the panels. •Colour: Light grey or off-white. •Texture: Smooth or slightly textured surface. Porous/bubbly interior with no visible stones or aggregate. •Weight and density: The weight varied from 9 to 30 lbs/ft2 and the density is ap- proximately 25 to 37 lbs/ft3 (pcf), which are 20 to 25 per cent of normal reinforced concrete. It produces a somewhat hollow sound when tapped with a hard object. •Strength: Compressive strength was ori- ginally specified to be 300 to 700 psi (25 to 37 pcf). •Bowing and deflection: RAAC roof panels may bow or deflect. This can be most easily observed when there is differ- ential bowing from one panel to another. Siporex literature denoted a maximum deflection of 1/360 of the effective span under the weight of applied loads. FEATURE n n nPushing the Envelope Canada 29 •Softness: RAAC is soft and can more easily be scored with a screwdriver, screw or nail. Once RAAC has been identified at the building, periodic structural assessments of the panels should be conducted by a licensed structural engineer. The structural assess- ment should include a review of deadload, including any potential changes to the roof assembly and/or mechanical equipment on the roof, measurements of deflections and end bearing distances, recording of defects including differential displacement, cracks, spalling, water leaks, resonant sounding of panels for evidence of debonded steel re- inforcement, and recording of alterations made post construction. Localized intrusive openings and in-situ load testing can also be completed, with consideration for the po- tential damage that could be caused to the structure.5 Based on the results of the assessment, individual panels can be categorized based on their risk level. The report prepared by Rimkus recommends four risk categories: critical risk, high risk, medium risk, and low risk. Periodic roof condition assessment and moisture testing should also be performed by a qualified building enclosure consultant in conjunction with the structural assessment. Roofing assessments should include thermo- graphic imaging, electrical capacitance, and destructive cut tests with moisture probe equipment. The presence of RAAC construction is likely to affect more than just the school boards and other public entities which are currently implementing management programs for these structures. Those inter- ested in learning more about the topic are encouraged to review the references listed to the right. n Brandon Gemme is a Project Manager at Leading Edge Building Engineers in Vaughan, Ontario, Canada. He holds a Bachelor of Applied Science in Civil Engi- neering from the University of Toronto and is a licensed Professional Engineer in On- tario, specializing in building restoration. Brandon’s expertise encompasses evaluat- ing, investigating, and remediating build- ing envelope and structural systems. His involvement in numerous deep energy retro- fit projects has equipped him with valuable experience in design, modeling, and project management. REFERENCES: 1.Rushowy, K. (20244, June 27). Hundreds of Ontario schools with the same aging concrete as the Ontario Science Centre are at risk. The Toronto Star. https://www. thestar.com/politics/provincial/hundreds-of-ontario-schools-with-the-same-aging- concrete-as-the-ontario-science-centre-are/article_df6983d2-3251-11ef-862d-b361d- 337cf3d.html. 2.Benzie, R. (2024, June 21). Ford government abruptly closes Ontario Science Centre after report found roof in danger of collapsing. The Toronto Star. https://www.thestar. com/politics/provincial/ford-government-abruptly-closes-ontario-science-centre-af- ter-report-found-roof-in-danger-of-collapsing/article_3e7a8442-2fd8-11ef-9c00- 03276c11fe83.html. 3.Lam, E. (2024, June 24). Ontario Science Centre doesn’t require full closure: A close reading of the engineers’ report. Canadian Architect. https://www.canadianarchitect. com/ontario-science-centre-doesnt-require-full-closure-a-close-reading-of-the-engin- eers-report/. 4.Petrolab Ltd. (n.d.). Reinforced Autoclaved Aerated Concrete (RAAC) – Basic Com- position & Petrography. https://www.petrolab.co.uk/reinforced-autoclaved-aerat- ed-concrete-raac-basic-composition-petrography/. 5.Caruso, F (1998). Lightweight, Autoclaved, Aerated, Cellular Concrete Roof Panels (LAACCRP): Structural and Re-Roofing Problems. Interface. 6.The British Reinforced Concrete Association (BAR). (2023). REINFORCED AUTOCLAVED AERATED CONCRETE (RAAC). https://www.uk-bar.org/news/ BAR-GUIDANCE-NOTE-REINFORCED-AUTOCLAVED-AERATED-CON- CRETE-RAAC/113113. 7.CROSS-UK. (2019). Failure of Reinforced Autoclaved Aerated Concrete (RAAC) Planks. CROSS-Safety. https://www.cross-safety.org/sites/default/files/2019-05/fail- ure-reinforced-autoclaved-aerated-concrete-planks.pdf. 8.Rimkus Consulting Group, Inc. (2023, September 4). Understanding the Historic Use of Reinforced Autoclaved Aerated Concrete (RAAC) in Building Construction in Ontario. Infrastructure Ontario. https://www.infrastructureontario.ca/49fd31/conten- tassets/84df22e71b7c40b2aaeef94da88c78b5/rimkus-white-paper---understanding- the-historic-use-of-raac-in-building-construction-in-ontario---2024-06-25.pdf. 9.Department for Education. (2024, April). Reinforced Autoclaved Aerated Concrete (RAAC) Identification Guidance. GOV.UK. https://assets.publishing.service.gov.uk/ media/6628e519b0ace32985a7e5ad/GUIDE-DFE-XX-XX-T-X-9002-Reinforced_ Autoclaved_Aerated_Concrete_Identification_Guidance-A-C04__002_.pdf. 10.HTA Building Investigations Scotland. (n.d.). RAAC Assessments. https://hta-build- ing-investigations-scotland.co.uk/building-investigations/raac-assessments/. Steel Corrosion in RAAC.10 n n n FEATURENext >