After getting through our first Perth winter in our new Passive House I’ve started to reflect on just how different it is from a normal house. And, while I was the one who designed it, there are still many things that have pleased and surprised me about living in a Passive House.
For the record, I should note that our house has a footprint of 230sqm with 5 occupants. It’s north facing and has 170mm thick walls with R5.0 High Density insulation. We do have one small 6.6kw Reverse cycle AC unit (that hasn’t been turned on yet) but there’s no other artificial heating in the house.
It’s also worth noting that just over 10 years ago I designed and built a 7-star solar passive home using traditional techniques (double brick walls and single glazing). In this home we struggled to keep the house warm overnight due to excessive heat loss through the walls, gaps and glazing. At the time we thought the performance of that house was pretty good, but now compared to our Passive House, we can see that it was actually quite basic.
So, on to our observations. From a comfort point of view, this has been the most enjoyable winter we’ve experienced in our lifetime. According to BOM, winter in Perth 2022 has been quite average with mean maximum temperatures in the 18–20°C range and mean minimum temperatures in the 8–12 °C range. The coldest morning was on the 3rd of July, when minimum temperatures dipped to 2.5 °C at Perth Metro.
During this winter, however, we’ve done away with heavy PJ’s, tracky dacks, and Ugg boots to instead sleep in light clothing with just a light blanket or doona. My boys wake up early and have their breakfast in just a T-shirt, and are often shirtless throughout the day. My wife, Sophia, really feels the cold but I’ve often caught her leaving early for work in a light pullover and have to remind her that it’s actually 8 degrees outside and she’ll need a warm coat!
Here are some statistics and thoughts so far:
The average internal temperature was 22°C with a minimum recorded of 19.8°C early some mornings. Once there is some activity in the house the temperature quickly rises back to a more comfortable 22°C. It’s been interesting to note that the south side of the house can sometimes be a few degrees cooler than the north side.
We had one of the wettest winters in a long time with some severe windstorms and hail, but we were often oblivious to the outside weather. The sound proofing and insulation of an airtight home do an excellent job of buffering wind and rain noise. Sophia also reminded me that we don’t hear traffic noise or those annoying crows that roost in the tree outside our window.
While Solar Passive shading design is critical in a non-passive house, we haven’t found it so important in our Passive House. We found that the direct heat gains from the sun through the north facing windows were welcome on the coldest July/August days, but probably less than necessary in June. This is attributed to the fact that heat losses through airgaps, windows and the thermal envelope are minimised. A typical Solar Passive home that isn’t a Passive House requires solar heat gain from April to September. From a design point of view, this means you can have deeper awnings or alfresco roofed areas in a Passive House, without worrying about the loss of direct solar heat gain in winter.
Without the need for additional heating, we’ve significantly reduced our home’s electricity usage and cost. The biggest energy user in the house is the heat pump clothes dryer, but we usually only run that during the day when the solar panels are generating electricity.
Building comfort, health and operation:
We have polished concrete floors and, while in a typical home we’d be concerned that they’d feel cold under bare feet, this has not been my experience at home this winter. Because the internal temperature is stable, the floor surface is also at a comfortable temperature. This makes concrete or tile flooring a much more appealing option over timber and it hasn’t been necessary to wear socks or slippers inside at all.
With warmer surface temperatures there’s been no evidence of condensation or mould spores that I’ve often found on glass and window reveals in non-passive homes.
The ventilation system keeps the humidity level stable at around 50%, which is optimum for human comfort. Combined with constant air circulation we’ve found several other benefits of this:
Clothes dry quickly overnight or during the day on racks inside the laundry.
Bathrooms and bath towels properly dry out between use so you don’t get that smelly, musty smell in the room. We haven’t needed heated towel racks, tiles or lamps to make the bathroom comfortable to use.
We have HRV boost switches in every wet area that increases air exhaust volumes by 30% for 30 minutes. This helps to extract smells and humidity from the kitchen and bathrooms after use.
The house smells and feels fresh. You aren’t hit with that typical musty, stale smell when you enter the house after being away for a few days.
Dust levels are a fraction of what you would expect. The closed windows, warmer temperatures, and lower humidity combined with air filtration seem to do a great job of reducing dust from both outdoor and indoor sources.
In winter it’s important to keep doors and windows closed to keep the cold air out, but that’s okay because fresh air is constantly supplied to every living space.
Our boys all sleep with their bedroom doors (and windows) closed at night and we can be confident that they’re receiving enough fresh air.
I feel that we’ve been sleeping much better than we have in the past.
I’ve noticed that we’ve been getting cold and flu symptoms much less often than most winters. This could be entirely luck but I do believe that the ventilation system helps prevent sickness spreading amongst the family and contributes to a quick recovery if we do get sick.
On warm winter days it’s been nice to open windows with the knowledge that the interior temperature will recover quickly once these are closed again.
So, that’s a summary of our first 5 months living in our own Leanhaus from May to September 2022. So far, I’m more than satisfied and grateful for the comfort we experience every day. It would be very hard to go back to the old way of living. Any downsides? I haven’t found any yet, but summer is just around the corner and I’m looking forward to seeing how it performs in the Perth heat.
What would you most appreciate about living in a Leanhaus?