Drone inspection Paradox – Speaking from Professional

Drone application in the view from Professional Surveyor 

As drone technology, or Unmanned Aerial Vehicle (UAV) , becomes increasingly mature and commercialized, the real estate industry has jumped at its potential for building inspection. 

Use of Drone in Construction field / inspection 

Drone technology contributes to the construction field in several ways. It can be used to capture a full picture and provide a solid understanding of the site. It can help in constructing a progress model that assists in monitoring construction process with ease. 

Theory Vs Practical and Professional 

In theory, it is an elegant solution that allows inspection to be carried out on areas that are hard to access. In addition, some IT Engineer alleged that an accurate diagnosis of the building could be be exponentially enhanced by AI. Though, we have had a lot of reservation to this AI application theoretically. However, the actual application of drone technology in building inspection can be less than optimal and costlier than previously believed. Aside from all the hype, it may not stack up against other alternative building inspection technologies and methods.

Professional Surveyor Feedback to Drone application

While UAV can reach areas that are difficult to reach, they have their own physical limitations in professional building surveying. 

Physical Limitations includes:

Hardware Limitations 

  1. UAV has a general altitude limitation of 90m and the image pixel is limited at 1084-2k in most models. The image via the controller is usually compressed for storage, at an even lower resolution. For some inspection which demands close visual inspection, such as sealant shape, cracks on the wall, damp patches mark, deformation of materials, rusty stain etc. The image captured are lust loss and become unreliable. 

Glare from the reflective surface 

  1. Drone operation is heavily dependent on weather conditions. Sunlight can cause glare on reflective surfaces, rendering footage and image unusable. Should there is strong reflective sunlight, the image becomes glared with distorted illusion background . 

Insufficient data for thousand type of variation to build machine learning

  1. AI diagnosis for building inspection is often mentioned as a feature together with drones. AI is built on top of a massive database that promises diagnosis and predictive ability. However, buildings vary by many elements, such as building envelope, height, location, profile, and usage. Furthermore, buildings are dictated by regulations as a product of the location, weather and idiosyncratic factors. There simply isn’t enough data available to power AI to be a blanket solution to building inspection. Currently, professional knowledge is still essential to interpret information generated by AI.

Safety and Lack of Standardization 

  1. There are designated No Fly Zones due to congested buildings, privacy, securities, etc. In addition drones application is not standardized for UAV inspection deliverables. One very rare known limitation is the safety distance between the building and the drone, many drone model is designed to be in hold position when the drone intervenes into the safety distance. This distance makes the image captured ability be doubtful.  

Form over substance

Professional Knowledge is indispensable and cannot be replaced by UAV or AI currently. Having said that, drones can assist Surveyor in capturing images, reference pictures and preliminary scans prior to on-site survey. Unfortunately, it may upset the Surveyor owning to the image reliability. 

Drone application and 360 Cam

Our feed previously posted has presented the 360 Cam for capturing in centimetre distance to the external wall. The image is sent via data to the mobile phone. The inspector can inspect the physical object with the immediate aid of 360 image .

 

Be a smart user to technology 

Always be handy to the technology can advance your professional skill. On the contrary, too much fantasy to the technology will be ended with effort abortive

Hand-free Toilet

In the week between May 7th and 15th, 867 COVID-19 infections were found in Thailand Simmummuang fruit and vegetable market. Health investigators in Thailand identified the entrance of the public toilet as the suspected source of most infections. This rises our concern on the infection possibility of public toilets in Hong Kong.

Simmummuang fruit and vegetable market: https://www.bastillepost.com/hongkong/article/8489819-%e6%b3%b0%e8%a1%97%e5%b8%82%e7%88%86867%e4%ba%ba%e6%96%b0%e5%86%a0%e7%a2%ba%e8%a8%ba-%e5%8e%9f%e5%85%87%e7%ab%9f%e6%98%af%e5%85%ac%e5%bb%81

Transmission Route in Public Toilets

According to Joseph Allen, associate professor at Harvard T.H. Chan School of Public Health, public toilets can be an important source of COVID-19 spread. The major way of spread are flushing and touching.

When toilet water contains viruses and bacteria, the churning and bubbling of water creates particles that will float in the air. These  viruses and bacteria will spread around the toilet, linger in the air and settle onto surfaces in the toilet. COVID-19 can survive in the air for 3 hours and even up to 24 hours in paper. Hence, the possible transmission route are people breathing in viruses when flushing and people touch installations in the toilets which viruses and bacteria settled.

COVID-19 in toilets: https://specialty.mims.com/topic/covid-19-in-hospitals–toilets–staff–public-areas-show-contamination-

Ways to Prevent Infection in Public Toilets

In Hong Kong, the most common way to prevent infection in public toilets are wearing mask, wash hands after using the toilet and increase disinfecting arrangements. Nonetheless, these precautions still remain some loopholes in our dense against COVID-19. One common example is after washing hands, people still need to hold the door handle and open the door. If there are some viruses settled on the door handle before, the people will also get in touch with the viruses and may get infected if he or she then touch his or her mouth, nose or eyes. This example is just a tip of an iceberg, in public toilets, not only we need to touch door handles, but also push button toilet flush, faucet handle, soap dispenser handle, etc.. The more we touch, the higher the possibility that we are infected.

Touching doors in toilets: https://health.ucdavis.edu/coronavirus/covid-19-information/coronavirus-mistakes.html

Touching Flush Button: https://www.pbs.org/newshour/health/public-bathrooms-carry-coronavirus-risks-heres-how-to-be-careful

To close up the loopholes, the best ways is to reduce the amount of viruses and bacteria spreading from flushing and minimize the need of touching in public toilets.

Reduce Viruses from Flushing

People no need to touch the toilet lid, the lid will automatically opens and closes when nearing or leaving the toilet. Therefore, even when people forget to close the toilet lid, the auto open/close lid will close the lid and reduce the amount of viruses and bacteria spreading.

Minimize the need for Touching

Although closing the toilet lid will reduce the amount of bacteria and viruses comes from flushing, there are still risk of getting infected in public toilets as it cannot minimize the amount of bacteria and viruses to 0. As a result, another effective precaution will be minimize the need for touching in public toilet, that is, to update a traditional toilet into a hand-free toilet. Here are the lists of installations in hand-free toilets.

  • Auto Toilet Door
  • Auto Flush Sensor
  • Auto Trash Bin
  • Auto Toilet Seat Sanitiser Dispenser
  • Auto Toilet Paper Dispenser
  • Auto Tissue Dispenser
  • Auto Soap Dispenser
  • Auto Faucet
  • Auto Door
  • Auto Hand Dryer

No ones knows when this pandemic will end, but we can try out best to minimize the possible spreading routes. Wearing mask and frequent disinfection are ways preventing viruses getting into our body, while upgrading toilets to hand-free toilets are smart ways to reduce the amount of bacteria exists in toilets. GBE will keep updating different measures to stop transmission route for the public to fight COVID-19.

GBE welcomes comments from professionals and enquiries from the Public

Cracks in Stone Cladding

Nice Stone Cladding but Danger from Height 

Stone cladding are natural, good-looking and durable, and are widely used in both interior and exterior applications. Although stones are durable, on average, you may not know that there at least is 1 to 2 % of stone panels on buildings in US (Simmons & Richter, 1993) contain cracks due to various reasons.

Example of cracks on stone cladding: http://www.service.hkpc.org/hkiemat/previous/2008/mastec03_notes/SLCHAN.PDF

Common Types of Stones

  • Granite

Most granites are suitable to be used as building materials, as they are hard, dense, durable, virtually impermeable to water, resistant to impact damage and stable within industrial environments. Because of the high cost of quarrying and finishing granite, it is frequently used as a cladding material or alternatively cast directly onto concrete cladding units. Besides, granite is also available for flooring and for hard landscaping including pavings, setts and kerbs.

Granite: https://www.minimegeology.com/granite-igneous-rock-graywhite

  • Sandstones

Natural sandstones can be fine or coarse in texture depends on the nature of the original sand deposit. Some types of sandstones, for instance, Calcareous sandstones, are not durable under acid rain.

Sandstone: https://freewp.cfsscloud.hk/idb/rs024-sandstone/

  • Limestones

Limestones must not be mixed with or located above sandstones, as this may cause rapid deterioration of the sandstone. Some limestones, for example, dolomitic limestone, is more durable then original limestone as it replace calcium carbonate content by magnesium carbonate. Nonetheless, it still cannot resistant to heavily polluted atmospheres.

Limestone: https://www.azomining.com/Article.aspx?ArticleID=1236

Effect of Cracks

The major concern of cracks development on stone slab is the weakening of fracture withstand ability on the maximum wind load of the stone panel. Another concern is that cracks may diminish much water exclusion properties of the of sealer applied on the stone surface. The effect of cracks will eventually contribute to highly undesirable appearance effect and worst still , the safety issue for instance, corrosion of anchors. Other effects includes aesthetic qualities and durability of the stone.

Stone cladding falls from the building facade: https://www.researchgate.net/figure/Examples-of-stone-slabs-removed-from-the-building-facade-a-east-side-b-south-side_fig4_336970581

Types of Cracks

  • Natural Crack

Natural cracks are formed by geologic processes in the stone before it was quarried, hence, natural cracks are most likely more than several million years old. Some natural cracks appears to be artificial cracks, so natural cracks are recognized by the presence of natural crystal. Natural cracks are ubiquitous in some granites, 1 to 2 dozen may occur within an area of one square foot. When liquid, for instance, sea water and rain, makes its way through the clefts and dispense minerals into the crack, crystals formed. Although natural cracks are common in stones, not all of them weaken the stone, only some severely decrease the strength of stone.

Natural cracks: https://www.123rf.com/photo_98560883_red-granite-slab-with-a-deep-crack-natural-stone-texture.html

Natural crystal in natural cracks: https://tinyrituals.co/blogs/tiny-rituals/pyrite-meaning-healing-properties-everyday-uses

  • Exacerbated Natural Crack

Exacerbated natural cracks are natural cracks that have been widened or lengthened by non-geologic activities. They are recognized by its width and length exceeding the value expected for a natural crack.

  • Artificial Crack – Crack developed other than by natural process

Artificial cracks are formed by non-geologic processes. They appeared to have sharp edges on polish face, irregular walls and do not have well developed crystal. If artificial cracks are located in or near mid-span, they can severely decrease the strength / durability of the stone panel.

Artificial Crack: https://www.cnilawfirm.com/specific-construction-components-gallery/

Professional Building Surveyor pay attention to the “Causes of Cracks”

Cracks formed when the local stress of stone is larger than the local strength. The reasons increase local stress includes geological processes, quarrying, handling, fabrication, and erection. Each kind of reasons carries a ton of knowledge behind. Besides, residual stress may also be a major factor in the development of cracks, source of residual stress includes handling, fabrication, shipping, dunnage, and erection on the building. The most typical is the “erection” problem

 

  • Geological Processes

Stones experience heat and cold cycles repeatedly, in heat days, the stone expands while in cold days, the stone contract. The repeated thermal expansion stresses tend to open cracks along grain boundaries.

Cracks: https://www.champlainstone.com/stone-101/

  • Quarrying Process – Fine flaw hidden in the slab block 

stone can be damaged in the quarry if it is extracted by the use of explosives which may cause internal fractures and cracks.

 

  • Handling and Fabrication

damage can be caused by excessive tooling of the surface of the stone, it may cause hairline cracks.

 

  • Dry fixing / erection

If the workmanship or the installation of the stone cladding is too not strictly controlled, mal-anchorage may cause the hairline cracks will be easily found near the anchor point.

  • Shipping – Storage of inventory 

Granite slab should avoid being carried flat . The localised stress building up due to unduly surface may cause hairline granite crack. Examine the stone finishes before hanging on the wall is highly important

  • Dunnage

Dunnage is used to protect stones during shipping, if unsuitable material are used, for example, softwood, the stone may slide around and form cracks or damage.

 

Quality Control before Installation

Before installation, materials should be inspected according to the construction quality acceptance specifications and design requirements, for example, have factory certificate, inspection report, material mechanical properties test and stone radioactivity. On site witness sampling and sampling inspection can also be conducted. The variety, color, pattern, flexural strength, tensile strength, compressive strength and common defects of the stone tile should be checked.

Inspection

 Inspection Method Related Defects
Crack Meter/ Crack Comparing Device/ Optimal Measuring Device, Mechanical Extensometer Fracture, Cracking, Cracking or fracture of the stone element near the joints
Cladding Flatness and Slope Evaluation Vegetation, loosening of the stone element, non-linearity or inadequate dimensions of the joints, cracking or fracture of the stone elements near the joints
Measurement of Internal Humidity Level Biological Colonization, alteration or deposition, cracking or fracture of the stone element near the joints
Percussion Test

 

Loss of adherence of the stone element, flatness flaws of the cladding surface, Gap in the stone

 

Cladding Flatness and Slope Evaluation: https://link.springer.com/article/10.1007/s00170-019-04893-7?shared-article-renderer

 

Tapping rod for percussion test: https://shopee.com.my/TAPPING-ROD-MOSAIC-TESTER-TILE-TESTER-TILE-CHECK-EXTENDABLE-HOLLOW-WALL-HAMMER-CHECKER-HOLLOW-EXAMINER-TILES-CHECKING-i.53165988.1957429999

Maintenance – Cleaning

External granite and marble cladding require regular washing with a mild detergent solution. For example, highly polished external marble should be washed at least twice per year to prevent permanent dulling of the surface.

Cleaning: https://www.industrial-clean.co.uk/services/brick-and-stone-cleaning/

 

In short, although stones are durable, regular inspection and maintenance are required to identity the effect of cracks one by one and to distinguish whether maintenance is required.

GBE welcomes comments from professionals and enquiries from the Public

 

References

Simmons G., Richter D. Cracks in building stone. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1993, 30(7): 1553-1557.

Misery water seepage sources – Annoying water dripping in the middle of living area

Again , again and again, the water seepage investigation demands a highly complex analysis to both in-situ environment and desk study. The case presented here has been left unresolved over 2 years before GBE was called on board and finally took the issue to the end.

 

The annoying water dripping in middle of living area.

The building is a 4 storey house. It is generally deemed a luxury town house in Hong Kong. A water damp appeared on the ceiling of ground level where is the living area for family gathering. The damp worsened onward and started water dripping everytime the heavy rainfall happened. The seepage spot is about 8m away from the external wall. It became very misery where the water came.

Don’t undermine the importance of desk study 

Having reviewed the layout plan, structural plan, decoration record photos and some maintenance history, we have considered a few possible sources which might be attributed to the water seepage. Following with the desk study, we took the site inspection firstly to verify the information obtained from desk study, to survey any other information which were not found in desk study. This really demanded a lot of professional call because those items outside the desk study were also very tricky.

Patient is important – Elimination Method with “Right” Testing

With reference to many literature , the way to identify the water seepage sources is “Elimination”. We have to establish the few possible sources and apply the “Right” testing to verify the assumption. This needs some experience together with the professional judgement. Sometimes , the site condition can render some cues for this judgement. In this case , we have done the survey to window , external wall, roof and some interior fitting out. The condition of window suggested its good and fair condition while the rain outlet at the roof and the skirting at the roof have found not properly done. We thus started the pooling test to the roof.

Judgement Call for the possible seepage path

With the aid of fluorescent liquid, the pool of liquid is prepared and stayed for 48 hours. Followed to this , we then applied the UV torch for tracing the “possible path” . Again, the “possible path” demanded a lot of imagination , but we found the cues in the record photos. We found that the conduit were laid in the recessed chase formed on the floor level. It could be pathway for water running.

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We found the seepage and fix it 

Make Use of Verandah in High Rise Buildings for Fire Safety Aspect

The impact of Fire Safety Code in Hong Kong

The fire safety code has experienced a few rounds of reform. The most influential reform we opined was the code published in 1996 and also the code in 2011. While there are many honorable peers have shared the view to both code applicable in Hong Kong, GBE found one interesting HK-unique escape staircase arrangement which have been prevailing in 2 decades ago. This the verandah space intercepting between the apartment units and the requirement staircase (usually scissor-type)

 

Verandah Space being merged 

This verandah space was a space designed in half-open to the external air. The space is connecting between the staircase and the apartment unit through the fire-rated doors. Driven by congested space in Hong Kong, some verandah, in this case, has been enclosed by the window and merged to the apartment units. This was deemed to be against the fire safety code or approved plan.

 

GBP for showing the Typical location of the verandah in a domestic unit

The Provision of HK CAP 502

In 2007, the HONG KONG CAP 572 Fire Safety (Buildings) Ordinance has been put into enforcement. The “Purpose Of Ordinance” is cited in clause 2 of Cap 572 and We copied here as follows.

This ordinance is aimed to provide protection from the risk of fire of occupants, users, and visitors to certain kinds of composite buildings and domestic buildings.

The law further explains the requirements including fire service installation and equipment and fire safety construction for different kinds of buildings in its Schedule 1 , 2, and 3 correspondingly. The governing requirements stated clearly is to apply the Code 1996 as the “standard” to satisfy the intention of this Ordinance. Thus, the said “Verandah” enclosure or modification is likely in this radar.

 

What did Code in 1996 talk about the “Verandah”

In our view, there was no direct elaboration to the “veranda” being designed for the intercepting lobby between the required staircase and the unit. From the MOE code 1996 and FRC 1996, there was a few relevant paragraphs which came up eventually the “veranda” application as a protected lobby. Since the author was not the Code writer nor in an authoritative position to comment, this blog of write-up serves to trigger some interesting discussion.

 

The provision of the “Protection” lobby was written in clause 13.5 in MOE 1996 and the design of “Protection lobby” was explained in 11.3 FRC 1996. Nevertheless, the enclosing wall of the Protected lobby was further explained in clause 11.7. Honestly, it was a complex integration of different clauses at different code and could easily lead to various explanation outcomes. This undesirable situation such complex set of codes has been improved in lately 2011 code.

The interpretations of Protected Lobby stated in MOE 1996 Code

The design of “Required staircase and protected lobby” was explained in Clause 11.3 at FRC 1996 Code

The Clause 13.5 in MOE 1996 Code

Indeed, the old 1996 code has remarked very clearly in clause 13.5 MOE 1996 code that “such lobby shall be designed as a common area and an integral part of the staircase so that it could not be readily incorporated as part of any adjacent unit(s) of accommodation” The 1996 code did aware the issue of merging the protection lobby to the private unit. Nevertheless, the complex nature of the set of codes 1996 which led to different explanations may undermine the intention in clause 13.5.

Plan for demonstrating the Verandah between the required staircase and the apartment

Above is another example where the “Veranda” was inserted between the escape staircase and the apartment. Interestingly, the kitchen doors also opened to the verandah. It was believed that this layout configuration is hardly survivable in today’s Code.

Misery of Non-accountable GFA in Existing Building. The road from plain drawings to value-added

GFA is the core asset in real estate

GFA – Gross Floor Area is considered as the core valuable asset in real estate. One of the significant governing regulation to GFA stated in Buildings Ordinance is Building (Planning )Reg 23. The Reg 23 (3)(b) have listed in literal form the areas which can be subject to non-accountable GFA whereas the Reg 23(3)(a) has included all areas within the external of buildings as GFA countable.

The Ordinance allows some accountant GFA in 23(3)(a) becomes considered as non-accountable GFA through the power vested to Buildings Authority by section 42 of Buildings Ordinance and explained by the ADV – 02 (PNAP 30 in former version). Some GFA calculation cases are further complicated by the injection of sustainable development requirements stated in APP 151.

Existing Building GFA vs Regulation 23(a) 

In existing Building which was built in decade ago plus , the control to the non-accountable GFA was relied by Reg 23(3)(b) which generally covered the essential plants / duct / carpark etc. When the landlord wants to review/revamp the existing GFA hoping for unlocking the hidden potential, the latest requirements in 23(3)(a) mentioned before will kick in to the backdrop.

Some areas within the building which had been exempted from accountant GFA in the past may have to re-examine under Reg 23(3)(a) and is assessed in the ADV -02. The interesting but painful point is that some typically exempted in the past may now become accountable unless the modification is granted by BA. In some case, the modification is not straight-forward but under complex assessment such as BEAM requirement in APP 151. Obviously, the latest GFA requirements has blocked the unlock of some potential GFA.

Example showing the effect impact from tightening of GFA assessment

Assuming there is plant room , this plant room is assumed be acceptable by Reg 23(b). The implication of GFA will be manifest because the protected lobby going with the plant room will be exempted. To the contrary, If the said “plant room” is NOT in Reg 23(b), the GFA exemption will be at the stakes. The wall and associated protected lobby solely serving for plant rooms will be subject to the “non-mandatory features”. The area of wall and associated protected lobby will be barred by the overall cap of 10% in paragraph 4 APP 151 for non-mandatory features) . The capping 10% will effect some GFA from non accountable back to accountable.

Case by Case assessment 

Valuable assets in the urban areas are all GFA driven for the best maximization of property value. This is the key driving incentive to closely review and revamp from time to time to unlock the potential hidden GFA in the active asset management.

(Reader is advised to look also other strategies which have been shared in our other blog” of this website)

 

 

 

 

Part 1 : Coating materials for Aluminium cladding – Non-Combustibility

From natural anodisation technique to PVF2 coating technique , the aluminium finishing coating has undergone a lot of revolutionary advancement. In recent years, there came with the discussion about “Self-cleaning” of the aluminium coating surface. This is about the coating materials which gives effect to flush its’ surface every time in raining. “Self-cleaning” is indeed a merchants’ name . The behind sciences are varying from among different manufacturer.I have conducted some comparison among some cladding’s surfaces being applied to different “treatment” allegedly claim the self-cleaning properties.  In my small research , some coatings are sheet- applied on the surface of anodised aluminium cladding. Unfortunately, my research (limited online data searching) cannot conclude sheeting-applied one was made up compilable to the Section E clause 10.1 of FS code or as per the BS476 -part 4. Well, many peers have messed up the concept of BS476 – PART 6 / PART 7 which is about spread of fire to BS476 – part 4 which is non-combustibility .

 

There are some testing to confirm “non-combustibility”. The FS code of Hong Kong does a job to cite a reference table E1 to facilitate the conversion between BS and European standard . There are many building in Hong Kong are cladded with aluminium-panel externally , but the lack of attention is paid to its “non-combustibility” requirement. Example like “self-cleaning” sheet lining or coating or spray-paint applied materials and even the fire – ratardard which are applied on external architectural features. The add-on materials on top of the aluminium are sometimes commercially attractive in term of ease of application and its price but to the sacrifice of fire safety.

Fire accident in Grefell Tower, London

Photo : Wing On building in Sheung Wan was reported to have cladded with non-combustible cladding. Source from ejinsight on the pulse ( http://www.ejinsight.com)

In my next blog , I shall explain in details the “self-cleaning” being applied in aluminium cladding.

 

“Loose of Neutral” in Electrical Circuit in traditional expensive residential apartment

The night scene of Hong Kong is always representing the prosperity and the stunning pictorial attraction for many people . The backdrop of the night scenery is the densely packed high-rise buildings being lit up.

With the air-conditioning became introduced in Hong Kong , some traditional luxury residential development was designed with 3 phases supply to cope with the loading consumption

Effect of Neutral Loss and Over-heat

The 3-phased live wiring is pairing with the neutral wire. The power runs into your apartment through “live” and return through “neutral . There is a defect called “nentral loose” which means the neutral wire loose contact or in bad connection. If there is “neutral loose” , that may be caused by various reasons, there will be abnormal arcing around the point of connection, a flash phenomena or spake fire will be occurred from time to time to heat up the already loose connection point and adversely causing unpredictable loading of electric current passing through the entire circuit. This circuit connects the load side appliance such as air-conditioners, the electronic parts or protection fuses of these electrical appliances may be damaged.

Inspection by Infra-red scanning and WR 2 checking

Unfortunately, it was not always detectable the abnormal heat up around the connection point . I prefer to adopt the infrared thermography scanning technique in my project or my inspection. However, the electrician today prefer to do by visual inspection which in my view may be subjective in some occasion. Our in-house infra-red is E4 model from FLIR. This is not the latest model, but still fit to our general routine checking.

 

 

 

Acoustic performance in Curtain Wall

Curtain wall system is such a complex external envelope of the building . It is more than an enclosure but also to serve to reduce heat gain and sound proof. The evaluation of  heat gain is commonly considered by the amount thermal transfer in the energy unit. Nevertheless , lesser attention is given to the acoustic consideration . Thank to my friend Dr Man and our peers Lixil who shares me one table. The airborne acoustic reduction is considered by STC value which varies as per the glass panes composition and thickness of glass. STC is to measure the degree of decibel reduction. The reduction is further related to the hertz of sound transmission. For easy communication , each composition of glass panes will be assigned the STC value. The interesting observation is that the “laminated glass” is achieving similar STC value compared to similar glass panes thickness of “insulating glass unit”. Furthermore , A 12mm thick single panes can achieve similar STC value to 6+12+6 insulating glass unit. Indeed, there are more consideration to the curtain wall acoustic including the impact-borne sound transmission caused by impact to the mullion or transom . Sometimes, the provision of the noise barrier or the provision of the balcony projecting out from the external facade can help to reflect the unwanted sound such as traffic away.