Mar 18, 2016: Mould and Other Fun Stuff

Daniel helping to insulate the Greeny Flat

Daniel helping to insulate the Greeny Flat during construction in 2014.

Daniel Jones became a good friend during the building of the Greeny Flat. At the time Daniel had just completed a degree in engineering at the University of Wollongong and had recently been a member of UoW’s victorious 2013 Solar Decathlon winning ‘Illawarra Flame House‘ team. Daniel was keen to gain more on-site construction experience so he drove up from Wollongong once a week to help us build the Greeny Flat.

Two years later Daniel is completing a Masters Degree through the Sustainable Buildings Research Centre, working for Repower Shoalhaven and in his own words…

I’m doing home energy assessments for Parramatta city council, which is a tonne of fun.
I came across an apartment this morning with an internal bathroom (no windows) that had a really bad mould problem, it had an exhaust fan, which was extracting some (not a lot compared to a normal fan) air.

When they use the bathroom they leave the door open so air flow should be reasonable.

The only thing I could think of was to run the exhaust fan for an hour or two in the day when no one is in there to get the air changing a bit more.
They run an a/c at night but not in the room adjacent to that bathroom so the general humidity close by could be pretty high.
Any help would be hot 🙂
Mould in bathrooms can be a serious health and building durability problem

Mould in bathrooms can be a serious health and building durability problem (Source:

Mould in bathrooms (and elsewhere in homes) is such a common issue that I thought I would share with you my reply to Daniel. After spending a number of years performing energy audits on buildings in Montana I saw a LOT of mould problems and did a lot of study on the causes and possible solutions. So here’s what I suggested to Daniel which I hope some readers will find helpful…

In our climate, and most likely in this case, mould is the result of condensation forming on the surfaces of the bathroom. Condensation is a function of two factors, relative humidity and surface temperature. If the humidity is high enough and the surface temperature is low enough you’ll get condensation on the surface. If the condensation occurs often enough and hangs around long enough you’ll get mould growth. So dealing with the mould requires either or both of the following:
  1. Reduce the relative humidity
  2. Increase the surface temperatures
Reducing the relative humidity in this case would involve increasing the exhaust of moist air. The first thing to do would be to check that the existing fan is correctly ducted and that the ducting doesn’t have blockages or restrictions. Unless the attic is VERY well vented the fan should be ducted directly to the outdoors and not into the attic. The next thing to do would be to run the existing fan more, either by instructing the owners to leave it running or to replace the switch with a timer so that they could leave it running for an hour or so each time they used the bathroom. Either way it would be a good idea to put a simple temperature and humidity sensor in the bathroom so that they could keep an eye on it and make sure that the humidity is dropping low enough to prevent mould growth (I’d start by suggesting 50% RH but you’d have to monitor it to ensure that this was low enough and mould was not returning). Otherwise you could replace the existing fan with one that moves more air (once again you don’t want to put that humidity into the attic unless it is VERY well vented) and there are fans you can get that have built-in timers and/or humidity sensors. We just put one into a bathroom and it has a dial that allows us to adjust the humidity level. The fan will run any time the humidity is above the set point.
Increasing the surface temperatures can be as simple as insulating the ceiling above the bathroom. It depends where the mould is growing. Is it on the ceiling? The floor? The walls? Or just the walls that are adjacent to air-conditioned spaces? If the room next to the bathroom is air-conditioned and there is no insulation in the walls, the surface temperature of the bathroom wall will be lower, leading to more potential for condensation and mould. If the mould is all over the bathroom then I would suspect that the problem is more to do with air flow and humidity. However one thing to check is whether there is air-leakage within the wall cavities around the bathroom. Sometimes there are electrical cables or pipes or ducts that run from under the house up to the attic via the wall cavities. If the holes around these penetrations are not sealed, air can flow readily between sub-floor and attic. This can make the wall surfaces cold, leading to more condensation and mould. You can check by looking under the house and in the attic to see if there are unsealed penetrations. If so, seal them up and look to see whether the location of the mould corresponds with the location of the air leakage.
Most likely improving the ventilation of the bathroom will solve the mould problem but it comes with an energy penalty. Unless you are using heat-recovery ventilation, exhausting more air from the bathroom will cause outside air to be sucked into the house which will raise the inside temperature in summer and lower it in winter. This is why, in order to create an indoor environment that is not only comfortable but also healthy, safe, durable and energy efficient, you have to ‘Build Tight, Vent Right‘. ‘Build Tight’ means proper insulation and air sealing and ‘Vent Right’ ideally means Heat Recovery Ventilation along with correct venting of combustion appliances.

Minor Correction and Apology

In last week’s Newsletter I mistakenly described Mary Bowe as an Architect. Mary is in fact a Building Designer with a Degree in Environmental Design and is a member of Building Designers Australia and the Australian Passive House Association. Sorry about that.

More on Lithium Battery Recycling

Also in last week’s Newsletter I asked if any readers knew more about the recyclability of Lithium Ion batteries. A reader named Mark provided the following assessment of the situation…

In terms of lithium battery recycling I do believe this is just a matter of critical mass. Lead acid batteries have been around for a century and in this time the infrastructure has developed around them. Lithium is, as far as I know, highly recyclable in terms of recovery rates (even if the packs might be difficult to work with). It’s also reasonably scarce, and reasonably expensive (although prices are dropping). The fact it’s also often used in much larger systems (much bigger than a starter battery) means you tend to have a lot of it in one spot. It should be easier to get 16+kwh of batteries in one pack to a recycling plant, than to do so across hundreds of units in different locations.

At this point I just think we aren’t seeing a lot of batteries reach end of life. I believe at this stage nearly every failed EV battery has been taken back by the manufacturer for analysis and testing – people are actually keen to get a hold of them and are often unable to. There is great possibility for secondary stationary reuse of these battery packs before they are recycled (I have heard the Nissan LEAF factory uses old LEAF packs for power storage).

I understand large format Nickel-Metal-Hydride batteries are now generally recovered for recycling – but it took about ten years.

Thanks Mark, that all seems very reasonable to me.

Things That Caught My Eye This Week

Roll-up Solar

160318 Roll Up solar


This Energy Matters article describes a new type of solar installation that involves up to 100kW of flexible panels that can be unrolled and deployed in minutes. ‘Renovagen says from go to whoa,  the system can be fully deployed to the point of plugging in appliances in less than 5 minutes after arriving at a site’... Sounds amazing!

Designing for Trust

In this fascinating TED talk, Joe Gebbia describes the birth of AirBnB and how they have learned to get people to welcome complete strangers into their most private spaces.

Global Greenhouse Gas Emissions De-couple from Economic Growth

This article from The Guardian states that, for the first time in the forty years we have been monitoring them, greenhouse gas emissions leveled off at the same time as the global economy has grown. There have been a few other brief periods where emissions slowed but they occurred during economic recessions.  ‘Preliminary data for 2015 from the International Energy Agency (IEA) showed that carbon dioxide emissions from the energy sector have levelled off at 32.1bn tonnes even as the global economy grew over 3% .’

160318 GHG emission level off

The bad news is that we are still at record high levels of GHG emissions but the good news is they haven’t increased. This may well indicate that the tide is finally turning away from fossil-fuel-derived energy and towards renewables and energy conservation.

‘The figures are significant because they prove to traditionally sceptical treasuries that it is possible to grow economies without increasing climate emissions… The new figures confirm last year’s surprising but welcome news: we now have seen two straight years of greenhouse gas emissions decoupling from economic growth’.

At the risk of sounding like a broken record, I firmly believe that we won’t find a true solution until we move away from the current economic model that requires perpetual growth at all costs. Only when we work within a system that strives for balance in all things will we truly be on track to nurture the environment that nurtures us.

Arch Criminals

A friend in the States just sent me this shocking article from the Sightline Institute which describes how the executives of the huge Arch Coal Company paid themselves an 8 Million dollar bonus ONE BUSINESS DAY before the company filed for bankruptcy. Apparently they paid themselves more than $29 Million in bonuses in the year leading up to the bankruptcy. Unfortunately this sort of unbridled greed and corruption seems to be rife in the upper management of corporations and governments around the world. I’ll be amazed if anyone is ever brought to justice over it but the backlash might take America in an even scarier direction. Donald Trump’s popularity is largely due to ordinary Americans being sick to death of Wall Street cronies making insane fortunes while everyone else struggles to keep their head above water. How this mad Billionaire has managed to convince America that he is somehow different from all the other super-rich blood suckers is beyond me. Meanwhile I try not to image what it could mean for the world if he actually became President and Commander-in-Chief.

The silver lining to this cloud is the news that nearly fifty of the major American coal companies have gone into liquidation (as reported in the Sightline Article). Hopefully this marks the beginning of the end for Big Coal and hopefully it won’t take too long before Australia’s politicians realise that coal is not the answer to all their prayers and they’ll stop given Korean companies permission to open new coal mines near historic villages like Berrima or loading docks near the Great Barrier Reef.

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