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.

upgrading energy systems with HEC or CLP funding

HEC and CLP can provide a subsidy to building owners/managers to upgrade the communal services in buildings, including air conditioning, lifts, lighting, water pumps, etc. in commercial and residential buildings.

funding for energy efficiency improvement

It’s a fantastic opportunity for capital (CAPex) funding for energy efficiency improvement work! Both schemes are arranged to provide the rebate AFTER the work is completed and approved by the respective utility.

And both utilities require pre-endorsement by Registered Energy Assessor (REA) before application.

funding for energy efficiency improvement

Upgrading Existing Buildings

Greening of existing buildings can be a challenge, but the HEC Eco building fund and CLP Smart Power fund can help finance energy efficiency improvement to lower your CAPex and your future energy bills.

For more information call us on +852 2335 9830 today!

Green building certification what is it worth?

Green Building rating systems have to sell the benefits of certification before they can be physically realized because the developer needs to plan, construct, and sell the property.

Then, after the dust has settled, developers can judge if the promised added value was delivered. The WGBC has reported that a Hong Kong developer sold their BEAM Platiumn rated green building for 40% more than neighbouring properties of the same type, and 21% more than other buildings in the same district. A 40% premium, that is impressive. And the developer attributed the reason for the premium was the developments green building features incorporated to gain BEAM Platinum certification.

The message seems very clear, not only does Green Building reduce the environmental impact of the buildings, having a certified Green Building adds value, and its a financially positive decision.

Green Building defined by John A. Herbert

green building, john herbert is green building expert

by John A. Herbert

What is the definition of green building? First, some definitions [1] from around the world. Continue reading

Improving Hong Kong’s Green Buildings looking forward by John A. Herbert

by John A. Herbert
green building, john herbert is green building expert

In the 2017 Policy Address by CE C.Y. Leung there is just hint that the present loophole that allows non-green buildings to obtain GFA concessions will be tightened. Continue reading

BEAM PLUS Neighbourhood v1 by John A. Herbert

BEAM PLUS NEIGHBOURHOOD

Neighbourhood v1 is the new member of the BEAM suite of rating tools, this tool unlike it predecessors, which examines the final project, Neighbourhood is specifically designed to assess and rate the master planning stage. If the master plan changes another assessment is required.

If you are familiar with BEAM family and NB, you will recognise framework and credits structure, indeed twenty of the credits listed in the following table are similar to (almost copied from) BEAM NB v1.2 credits

About the Author

John A. Herbert is a veteran professional with more than 30 years solid construction experience, educated in the United Kingdom he has been working across Asia for the last two decades, serving international, and local companies. And involved with the development of Hong Kong Green Building for a decade. He is a Hong Kong Registered Energy Assessor (REA), and a BEAM Professional.

BEAM Neighbourhood BEAM Pro

Hong Kong outperformed Shanghai and Beijing in green building performance by John A. Herbert

Hong Kong was the highest ranked Chinese city for green building beating out Beijing and Shanghai in study by Solidance funded by Singapore Government.

Hong Kong

Hong Kong was ranked 6th, the leading Chinese city, ahead of Beijing and Shanghai, a vindication of Hong Kong’s own independent BEAM green rating rating tool.

BEAM has operating for twenty years, since the first rating tool was issued in 1996, and today, behind the scenes, countless volunteers give up their free time to support Hong Kong community, with little credit and no reward Herbert said. John A. Herbert is a recognised green building expert, a BEAM Professional, and chairman of BEAM Technical Review Panel.

About the Author

John A. Herbert is a veteran professional with more than 30 years solid construction experience, educated in the United Kingdom he has been working across Asia for the last two decades, serving international, and local companies. And involved with the development of Hong Kong Green Building for a decade. He is a Hong Kong Registered Energy Assessor (REA), and a BEAM Professional.

#greenbuilding #hongkong #BEAMPLUS

How to avoid mould in air conditioned buildings

moisture mould problems air conditioned buildings

In air conditioned buildings, the exterior vapour pressure will be higher than the vapour pressure in the air conditioned room, therefore the vapour and moisture flow is high to low (blue line in the diagram above)

Now normally this is not an issue, because a decent ventilation system will transport moisture back to the air conditioning cooling coil, it’s condensed, and safely drained away.

However, problems occur when a vapour retarder is installed (red line in above diagram) interrupting the flow. Moisture becomes trapped, and even the best ventilation system cannot transport it to the cooling coil. Instead what happens, damp, moisture, and then mould growth occurs (left of red line in diagram above).

wall-mould-800w-2

And we already know the problems associated with mould, it causes poor indoor air quality, and therefore health issues for the occupants. If the air conditioning room also happens to be under negative (relatively) pressure, as often occurs in hotel rooms, the situation is compounded because the vapour quantity is increased, accelerating the process. It should be taught in school “don’t ever use vinyl wallpaper in air conditioned buildings” because it causes mould.’

This phenomenon is not limited to Hong Kong, it occurs in hot tropical climates, whether you are in Singapore, Indonesia, Shanghai, or Hong Kong.

Furthermore, it’s the type of problem that’s not immediately apparent, mould doesn’t just appear overnight, and it is unlikely to surface within the defects liability period (DLP).

thermal-scan-101

So it is obvious, lining the external wall of an air conditioned space with any vapour retarder must be avoided at all costs. But sadly it still happens today, increasing maintenance and costs for building owners and operators.

About Kelcroft

Kelcroft based in Hong Kong provides specialist advice, including energy, built environment, and green building consulting services, advising owners and design teams, to lower the cost of building operations.

tags

#mould #mold #hongkong #buildings #hotels #maintenance