When we bought our home, we fell in love. We loved the beautiful little cottage that was now our sanctuary, and was representative of a major milestone in our lives: our very own house! But, like nearly every other home purchaser, we didn’t consider – not even a little bit – what the house would be like to live in day-to-day. Whether it would be thermally comfortable, what it would cost to keep comfortable, and what impacts the thermal performance of the home would have on us and on it’s long-term durability. But now, two and a half years later, it’s weighing heavy on my mind. As a sustainability professional who improves other people’s buildings for a living I can no longer ignore what’s right under my nose. I want my very own Passivhaus home. Why?
This is the one that is most obvious, and it’s also the most enduring memory year to year. As winter fades into spring I feel grateful – and immediately promise myself I’m going to fix it before next winter. Always the procrastinator, as we approach this winter I’m already freezing in my draughty, high thermal mass, double brick home. The small measures I’ve started on haven’t done the trick. Perhaps it’s a case of poor solar design, with living to the east, little northern glazing and high ceilings, but one thing is certain – this house was not made to be comfortable in winter. Or summer for that matter!
It’s not just the rising damp
We have condensation everywhere, including on internal walls. And mould at times (although we’ve managed to avoid this of late). I’m sick of having to put condensation traps in the bottom of wardrobes, and carefully reviving jackets that succumbed to the spores. I won’t miss that! We only realised one of our walls actually had painted-over wallpaper when it just started to come clean away in sheets – affected by the rising moisture underneath. These minor ailments are signs of potentially significant and permanent damage occurring to my home. It’s time to go!
It blows a gale!
As I sit at my desk, I can feel such a draught that I need to wear shoes just to stop my feet becoming icicles. My house includes windows that don’t shut properly, floors dropping away from the skirting and visible daylight around the front door. All issues that signify my house is more than just a little leaky. Draughts can simply also be signs of the imbalances between warm and cold spaces, where draught is induced. Either way, it’s having a huge impact on our comfort throughout.
We need to think of others now
While I’ve been the one saying “just put another jumper on” and propping up the Explorer sock company for a while now, a new family member – one who spends most of his waking hours on the floor – means that comfort weighs on my mind more than ever now. While we’re thinking of icy draughts and cold little hands now, a feisty summer of 40˚C+ days (and 35˚C nights!!) is still fresh in my mind. I don’t want to worry year-round! I want to shut out those extremes.
As well as thinking about the temperature, I want my child to stay happy and healthy. Indoor air quality (IAQ) is critical to health and wellbeing. A sad statistic is that children in Australia and NZ have the highest rates of asthma in the world. I also have a number of friends and relatives who have developed hay fever late in life. I have done some research, but also just made some observations, and I believe it’s no coincidence that our homes are among the worst in terms of IAQ. There is no history of asthma in my family, and I don’t want this to start now. A Passivhaus is an investment in our health and comfort, with no condensation, no mould, no allergens and a constant air supply, often fresher than outside thanks to filtering in the MVHR.
But I’m still thinking of myself.
Oh the dust! There’s 100-plus years of dust coming to settle in my house. It lays across everything, and I can’t keep up with removing it. It comes up through the floors, blows in off the street, shakes off the dog and is trodden in underfoot. I’m sincerely looking forward to the day that my house is airtight and the ventilation system provides me with a fresh, filtered supply of dust-free air. I can handle changing a filter once a year if it means I only dust that often too!
My home is my investment
Despite it being a very sentimental thing, as owning a home in Australia tends to be, our home really is where we have chosen to sink a decade or so of hard-earned $$. So we want to protect that, and even hope to make that investment work for us. We’re going to make this a Passivhaus, and we’re going to love living in it. And when the time comes that we choose to move on, I am sure that someone else will be just as keen to have that too. For the past decade or more, there has been strong growth in the market for ‘green’ homes – a premium of up to $100,000 or more.
So it’s time. I’m going to go Passivhaus!
If you want to know what Passivhaus is, head to this page. It’s basically a methodology that I’m applying to my design and build that will ensure (guarantee!) that we have a comfortable home with almost no energy use. And here’s how we’re going to do it:
An airtight home will give us control over the heat losses (and, conversely, summer gains) meaning that we’re not just throwing heat, energy and money out the door. Most people have no idea that leakiness accounts for up to 50% of their heating and cooling energy – and that’s a huge figure! And so easily remedied in most cases.
I’ve already started with foam core rod in the obvious places, better door seals, door snakes (though temporary fixes), and sealing up duct vents that we don’t use anyway, but the main fix is much larger. Next we’ll be looking at the bigger picture, and using a bigger renovation project as a good opportunity to make wholesale fixes to the whole envelope. This will include lots of tapes and membranes, and making obvious decisions like removing chimneys and retrofitting wall cavity insulation so that wall vents can be permanently closed off.
Windows and doors will be replaced or significantly treated to eliminate unnecessary leakages. Though installing new doors and windows is not an option available to everyone, the renovation gives us a great opportunity to get things right. The old timber windows are starting to rot, some don’t properly close at all and the clear single glazing is doing nothing at all for our comfort.
Insulation, insulation, insulation
Did I mention it was cold? There is no wall or floor insulation, and birds and possums are making a mockery of our roof insulation. It’s clearly time, and such an easy and effective fix, to insulate. The floor will be tricky, with a sloping site and some on-grade, but we’ll be doing as much as possible up to at least R2.0. The wall cavity will be filled with a moisture retardant rockwool bead, giving us a boost of R1.5-R2.0 that will be supplemented with external-clad rigid insulation to at least R4.0. The roof will be completely renewed to at least R6.0. And all of this will be carefully installed with a consideration for eliminating thermal bridging. The trickiest parts will be at the floor-wall and wall-roof junctions.
The window upgrades will ensure that the insulation effect is carried across the façade. In any building, the windows are the weakest part of the facade in terms of thermal performance. If I’m going to the concerted effort to bring my building fabric up to scratch, not including the windows in this equation would be like leaving the doors open 24/7 – it’s madness. My new windows will be thermally-broken, double glazed with a low-e coating, and will be airtight as described above. In the old part of the house I’ll either be replacing them entirely (budget pending) or installing low-emissivity films so that the performance will be upgraded in the interim. The choice of film is important – a solar control film only has any effect when the sun is shining on the glass, and most often works best for summer conditions by blocking extra heat gains. I’m going for a low-emissivity film that stops the flow of heat all day and all year, much like a reflective foil, and gives me what is almost equivalent to double-glazing performance.
I cannot convey how much I am looking forward to my MVHR system. This is a mechanical ventilation system with heat recovery, and basically means that I’ll have a steady flow of fresh air 24/7, and it will be filtered. The heat recovery part of this means that the heat will either be kept in (for winter) or out (for summer) and that we’ll be able to maintain comfort inside without having to run big energy guzzling systems. The system is the size of a suitcase and uses about the same amount of energy as an LED globe. It has been established that these systems are much more efficient than naturally ventilating a home, especially when maintaining comfort is considered. Add in the benefits relating to IAQ, health and wellbeing, and it’s a no-brainer.
Passivhaus makes a lot of sense to me, particularly having grown up in a climate that experiences such extremes. I’ve slept in 3 layers of clothing at below freezing temperatures in the Tasmanian winter, and under fans during over-30 degree nights in Melbourne summers. I refuse to believe the only way to be comfortable is to run massive mechanical plant or burn any number of fuels, particularly in dwellings. As we face a more carbon-constrained future, face the impacts of climate change and energy prices continue to rise, I’m looking forward to providing an example of what the solution looks like, and not continuing to be part of the problem.