Unhealthy Hong Kong Homes

by John Herbert

We spend many hours indoors every day, and during the covid19 pandemic many people are forced to work from home.

If you or your family are suffering from persistent illness, symptoms might include headaches, fatigue, allergy, asthma, diarrhoea, or flu like symptoms, your home could be unhealthy causing sickness. Kids are still growing, and can be particularly susceptible to different types of illness during their development.

If you want to discuss your unhealthy building, call John Herbert 2335 9830 today!

Damp, pollution, faulty drains, faulty ventilation, and water seepage are just of some of the reasons causing an unhealthy home, persistent illness in your family indicates you could have a problem. Do you regularly see your neighbour in the local GP’s surgery or in the hospital, that could indicate both families are living in a sick, unhealthy building.

In Hong Kong, medical professionals are reporting that patients appear to be ignoring symptoms and illness, and do not seek medical attention early enough! Don’t delay already seek doctors advice immediately.

#sickbuilding #sickbuildingsyndrome #unhealthy

Building Air Leakage Resource Centre

by John Herbert (@johnherbert)

For building owners building air leakage costs extra money, whether it is through the additional energy use or poor indoor environmental quality. The latter, infiltration of polluted outdoor air and Radon are both a serious health concern impacting occupants.

Attempting rectification after occupation/renovation is always more difficult and time consuming, so the execution of the construction work is vital, we know it has a major impact on the airtightness of buildings.

Air leakage can be tested and verified during construction, using a 2 stage process using blower door test, supported with thermography (Infrared) and fog testing, to ensure unwanted air leakage is minimised.

In 2004 HK BEAM created 4/04 green building rating tool for new buildings, that introduced air leakage testing, and later in 2012 BEAM PLUS Interiors rating tool introduced air leakage testing for shops and offices, but regulation has not followed. Europe now has strict regulations requiring new buildings to undergo air leakage testing, to meet the country standard.

John Herbert organised air leakage seminar in 2015

Therefore to help reduce building energy use and wasting energy, air leakage standards and testing are needed here in Asia.

Air Leakage Frequently Asked Questions (FAQ)

What is Building Air Leakage?

A building envelope with openings, sometimes due to poor construction, allows polluted outdoor air into the building.

What are the consequences of air leakage in buildings?

In Asia, air infiltration has several consequences:

  1. allowing hot humid air to enter an air conditioned building, causes condensation on interior surfaces, providing the right environment for growth of mould inside buildings;
  2. poor indoor air quality impacts the health of occupants;
  3. increased energy use;

How to Identify Building Air Leakage?

Air leakage can be detected using blow door test, thermography, fog testing to identify the location of the air leakages, but in most cases these do not quantify the amount of leakage corresponding to each leakage.

What is the Key Issue for Buildings with Curtain Walls

According to the ASTM standard for curtain wall construction, curtain wall have permitted air leakage rate that qualifies for the ASTM standard. ( xxx litres/sec at 300pa). that means buildings with curtains walls have air leakage.

Resources (suggest a resource?)

Retrotec blower door Online Training

German Air Leakage Association Handbook (Chinese)

German Air Leakage Association Handbook 2 (Chinese)

Building Air tightness article by John Herbert (HK)

Air Change in Low and High-Rise Apartments research (HK)

A Guide on Indoor Air Quality Certification Scheme for Offices and Public Places 2019 (HK)


Passive Haus Guide (UK)

Analysis of Large Building Air Leakage
Testing DOD (USA)

Air Testing Standard Military (USA)

ATTMA Air Testing Standard 1 (UK)

ATTMA Air Testing Standard L2 non-domestic (UK)

BEAM Plus – Interiors rating tool (PDF)

HK BEAM 4/04 version (PDF page 1-20)


tightness EU newsletter (PDF) Nov. 2020


  1. CAN/CGSB 149.15 – Determination of the Overall Envelope Airtightness of Buildings by the Fan Pressurization Method Using the Building’s Air Handling Systems
  2. The United States Army Corps of Engineers Air Leakage Test Protocol for Building Envelopes
  3. ISO 9972:2006 – Thermal performance of buildings — Determination of air permeability of buildings — Fan pressurization method
  4. ASTM E779 – Standard Test Method for Determining Air Leakage Rate by Fan Pressurization
  5. ASTM E1827 – Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door
  6. EN 16798-3: 2017: “Energy performance of buildings – Ventilation for buildings – Part 3

tags: air leakage, infiltration, exfiltration, permeance, building envelopes, airtightness

BEAM PLUS, HVACR Air filters, and COVID

While it seems everyone is scrambling to retrofit their HVACR systems with air filters rated at ASHRAE MERV13 to mitigate the impact of COVID-19 virus. However, the smart building owners that followed the BEAM PLUS v1.2 NB IEQ5 credit requirement already have MERV15 air filters installed!

That BEAM PLUS standard was set years ago in 2010, and it is still better than MERV13 benchmark specified by WELL 2016 version.


Lousy IAQ Analysis

Restaurants in Hong Kong must comply with the relevant provision of the FEHD licensing requirements. For Air-conditioned restaurants, typically the indoor air is largely recirculated with a small quantity of fresh air / outdoor air added into recirculating air steam.

By law, the minimum requirement is provided in clause 42 of the licensing requirements, only 17m3/hr/person (or 4.2 litres/sec/person) [1] of fresh air / outdoor is required, to put that into perspective that rate is lower than the normal 7-10 litres/sec/person rate.

Of course, the result is poor IAQ quality, because the air pollutants, including airborne covid19 [2] concentrations, are diluted extremely slowly.

“Poor ventilation may play a major role in transmission” RTHK reported the spread of covid19 investigation [3]. However, as explained above, it is no surprise, all Hong Kong restaurants have little fresh air/outdoor air, thus are poorly ventilated, and any bacteria/virus in the air is not diluted.

[2] http://www.kelcroft.com.hk/20200404-news-covid19.htm
[3] https://news.rthk.hk/rthk/en/component/k2/1537915-20200715.htm

Building Infrared Inspection

Building infrared inspection reveals hidden defects not visible to the human eye, the temperature image can locate the source of water ingress, damp, water damage, locate missing sections of thermal insulation missing, identify overheating switchgear, and much more.

#hongkong #thermography #infrared #building #inspection #condition survey

phone QR code

Pressurisation and IAQ

Positive building pressurisation and proper filtering of the outdoor air will be more important as testing reveals plastic in the air we breathe!

Plastic particles have been found in the air in the mountains but now in cities[1] . It may take years for the human studies and research but commonsense dictates plastic inside the human body, particularly in the lung should be minimised now.

1 https://www.theguardian.com/environment/2019/dec/27/revealed-microplastic-pollution-is-raining-down-on-city-dwellers

Vapour diffusion

Moisture is a problem in the tropics so its important to understand two issues, moisture is transported within the air, and through a process known as Diffusion.

One property of air is the water vapour pressure, for air-conditioned buildings, we are mainly concerned with the difference between the outdoor and indoor water vapour pressure. Why air-conditioned buildings? Cooling and dehumidifying indoor air lowers the indoor water vapour pressure.

In the CIBSE guide or equal, properties of air, look up the water vapour pressure for outdoor air say 35 db/28 wb and an air-conditioned space, lets say 24 degC and 50% rh. That delta P, the pressure difference is the driving force for moisture diffusion through the building envelope, including curtain walls, towards the lower pressure space inside buildings.

Typically, we expect that “Good Ventilation” inside the building will transport that moisture and condense it on the cooling coil. However, if the internal face of the external wall is blocked, with a vapour barrier on the inside or obstacles preventing air movement, moisture will accumulate internally causing mould.

Often vinyl wallpaper or a polymer type paint, essentially a layer of plastic, is used inside buildings, which stalls diffusion, causing moisture to accumulate internally, causing damp and mould as shown in the diagram above. If the room is naturally ventilated the water vapour pressure inside and outdoor are effectively equal, and adjacent air-conditioned rooms would with similar conditions means the delta P is also effectively zero.

So its important to understand the different processes, to solve IAQ problems.

Productivity & Sick Days

The Hong Kong outdoor air quality and therefore the indoor air quality will be miserable for the first week of Oct. 2019 impacting productivity as the number of sick days is likely to increase in the urban areas (the places where people work).

The AQICN.org website is an invaluable resource reporting the real-time outdoor air quality but also providing a prediction for the next few days, and its bad news, it predicts Unhealthy (over 100) air quality.

Causeway Bay – greater than 100 is unhealthy
poor Outdoor Air Quality predicted 30 Sept – 5 Oct. 2019

Study after study shows poor air quality correlates with increasing hospital visits for respiratory problems.

Can we improve the Hong Kong Indoor Air Quality? the simple answer is yes, controlling the outdoor air is important to prevent condensation, and properly cleaning the air, before pumping it around the office, is the most practical solution.

CENTRAL – greater than 100 is unhealthy
poor Outdoor Air Quality predicted 30 Sept – 5 Oct. 2019

Hong Kong’s IAQ certificate requires the outdoor air quality to meet the same criteria as the indoor air quality values, so we guarantee no measurements can be taken this week!

And that’s its weakness, those measurements are a snapshot, taken on days with “good” outdoor air quality, this gives owners a false sense of security, on other occasions the Outdoor Air Quality and therefore the Indoor Air Quality does not meet the objective.

Proper air outdoor air management, including air cleaning, will improve the indoor air quality in your building, in your lungs, and lower the number of Hong Kong sick days.