Hi, there, and welcome to this week's episode of The Mould Show. Today we're going to be talking about the issue of humidity in the built environment. We're broadcasting from Australia. This is in Southeast Asia, and many cities in Australia are plagued with humidity problems, especially towns like Darwin. But, what about other areas of South and Southeast Asia like Kuala Lumpur in Malaysia or Jakarta in Indonesia? Or what about in your hometown?
We are going to be talking about this issue of humidity, and I'm going to be reviewing some of the research literature on humidity and what building scientists and engineers have worked out as some of the sustainable practices for reducing the levels of mould. And this couldn't be a more important topic because there have been changes to the residential tenancy laws, certainly in Victoria and in Australia, making the onus of responsibility for having a mould free living environment more of a responsibility for the landlord.
But also, if the tenant is claiming that mould is a problem, they need to be able to prove this. So this episode is going to be focusing on humidity, and I've titled it, You Give Me 10 Minutes And I'll Give You The Truth About Having A Mold Free Home In Humid Climates. I'm going to be going over not one or two, but the three main ways in which mould can take hold inside your home, and we're going to go over how you can control this, especially if you are living in a highly humid environment. And I'm also going to be talking to you about even in a cold climate, when you're running the heating indoors, how you can get condensation developing inside, and essentially, you can have a humid environment, especially if you are running a washing machine in Euro-style laundries, and if there is inadequate ventilation, you're going to have a very humid living space, and that's not a good thing.
So we're going to kick right off and go straight into the best practices for having a mould free home in a human climate. And in a sense, this really does mean that you need to understand some of the different growth models that, as I said, these climate scientists and building engineers have worked out for you. And we're going to go through these eight models. And the first you need to appreciate is there's something called relative humidity. And that is the amount of water vapour that there is in the air. Why is this important? Well, mould requires a couple of things for its growth, and one of these is an available source of water. The temperature needs to be right as well. Too hot or too cold and the relative humidity is not going to condense out and form droplets for mould to use. When we're considering whether any building or room interior could sustain mould, we need to take into consideration how long or what is the duration of, for example, the wetting event? What is its frequency?
For humid environments, they may be more or less humid in spring or summer. Mould growth though also depends on the surface condition. And what do I mean by the surface condition? Well, when the building engineers assess the surface condition, they're looking at the porosity of it, and this has a big impact on whether or not the water is absorbed and making that material wetter or whether it, in a sense, wicks off and is easily dispersed and can evaporate. This issue of exposure impacts on buildings. And what do I mean by exposure? Well, if we're talking about basically an indoor-outdoor living area, what is the temperature fluctuations in that particular space? And then there is the sensitivity of the materials, that is, what are they made from? Is it a jural material, for example, or is there a lot of plastics or polyesters, for example, if we are considering drapery around windows, which could potentially be suffering from condensation due to humidity? And then we have to look at the amount of nutrients, how clean is the property?
Now, when we focus on these different models for understanding it, we need to take them all into consideration when examining or doing building inspections of potentially mould contaminated properties as well. And we also need to drill into how different types of building materials that a home can be constructed from impact on their ability to support mould growth. We'll go into the four classifications that building scientists use to define the type of building material. And, obviously, the first one is an optimal culture medium. Well, what do I mean by that? Well, if you were to take a pure microorganism in my microbiology lab and streak it out onto a Petri plate, well, that Petri plate contains all the right nutrients and available water to sustain the colony and provide luxurious growth. But what happens if your building has been flooded by sewage, for example, if the storm water backs up?
Well, then that carpet and the underlay would be potentially an optimal culture medium. But the next type are biologically recyclable building materials, and what's a great example of this? Well, reclaimed wood. Now, that is a great green building material and that is at the next stage of building materials that could support mould growth. Then we have biologically adverse recyclable building materials, and the typical example here is green thermal insulation, which is made with polyester or earth wool. And then we have the next type, which is biological building materials that are neither degradable nor contain nutrients. Now, I correct myself here. These aren't biological. They are just building materials that don't contain any natural materials, and a typical example here is precast concrete slabs.
Now, you're probably thinking, "Okay, relative humidity, temperature, how porous the material is, whether or not it's timber or recycled timber, that all makes sense. What can I do?" What can you do to make sure or optimize your indoor living conditions so that you reduce the probability of mould being a problem in your life or home? We now need to go into the three ways that you slow down or interfere with the mould growth life cycle. And the operative word here is slow down mould growth. That's what you're trying to do if you reach for that disinfectant to spray on your grout, tiling in your bathroom, or if there is a small patch of mould, you might consider using vinegar or, or oil of cloves, or some of the natural disinfectant. You'll want to slow its growth down. But rather than reaching for the disinfectant, there are three things that you can use, and I need you to consider these.
The first one is moisture control. Obviously, that's a no-brainer. If you've got a plumbing problem or a building defect with guttering or rising damp, well, you should get onto that and control the moisture. But we're talking about living in humid environments. Well, the World Health Organization recommends an indoor living area percentage of 75%. I don't think that is sufficient. At 75% relative humidity, you will certainly definitely have ideal conditions where some moulds can grow. I much prefer the U.S. EPA recommendations, which are at 30% to 60% indoor relative humidity. The next more important issue is nutrient control. When your plasterboard gets wet, it can survive, because it is chewing through the material. For example, the cardboard backing of the plasterboard. So you want to maintain a clean and dust-free home. Remember that microorganisms have an ideal growth at 25 to 30 degrees Celsius.
So in a mechanically ventilated building or an apartment complex, you'll want to try running your air conditioner 24 hours a day, or at least for 12 hours a day. And this is the big issue with sustainability here, because is it feasible to operate the air conditioner for less than 24 hours a day to reduce the probability of indoor mould contamination? And a lot of work is being done worldwide on testing this out, because the costs involved with running air conditioners are a very significant cost of multi-story buildings in urban environments. Now, some of the emerging research is looking at cycling the air conditioners on and off. That means reducing the amount of condensation occurring inside a building. So you can see, it's pretty simple. Moisture control, temperature control, and food control. But if you are in an apartment, then you really only have your air conditioner and openable windows, if you have any, or ventilation, mechanical ventilation, under your control.
But you are able to clean, you are able to ensure that items of personal property are not budding up straight onto walls that could show these significant temperature shifts, because that's when you can get condensation and that's when you can get this problem, especially in humid environments.
Now, the four key takeaways from today are, number one, use air conditioners preferably on for 24 hours a day. Maintain and properly clean and maintain your property in a hygienic state. Number three, reduce the moisture sources. And number four, and again, this is emerging research, there is some nano particle-containing paints. There are also heat reflective paints and other interesting building materials. Heat reflective paints can be applied to the roofline and are reported to reduce the amount of heat transferring inside to the building through the building envelope.
So these are really interesting emerging areas of building and construction science. I'm a microbiologist. I love it when science and chemistry usefully applied to these real world, big-ticket problems like, how do you control moisture and mould growth sustainably in humid environments? Now, my call to action this week is a little bit different. I've recently joined something called Clubhouse, which is a new social media app. I would encourage anyone who likes to have conversations, who is pro-wellness and into various different aspects of science and technology to consider jumping on Clubhouse. This app is really interesting. It's available only for iOS at this point in time, but I've been having some fantastic conversations around mould, wellness, sustainability, and environmental health.
I think it's a fantastic new medium. We're beginning to host some rooms focusing on these things, and certainly, the interactions are exciting. Very different to a live stream or a podcast in that it's very interactive. And so look out for this. I'd encourage you to download this app and jump in now. Look for me there. I'll be spending a bit of time there on a weekly basis with some collaborators here in Australia and also overseas.
In any case, my name's Dr. Cameron Jones. Be sure to follow and subscribe. This is also going out to a podcast so you can find that on YouTube and, of course, on all the normal social media channels. Anyway, have a good week. Stay safe and see you next week. Bye for now.