How does our Passive House perform in a heat wave?

Architect Ben Caine shares his experience of living in a passive house in Western Australia's extreme summer temperatures. Learn the systems, tips and tricks to staying cool and comfortable with minimal energy use.

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[TB-Personal]

Love the videos mate. Think you're onto a winning market in Perth over the next 10 years.

[DavidLockett-xb]

I have a solar designed home in Perth, Australia, that I designed and built in 1988 without mechanical air conditioning, and with only passive ventilation. The house uses thermal mass and never overheats in the summer, and requires very little none passive heating in the winter. If it does start to get warm inside after a couple of weeks of 40+ degrees, I open the windows and use mechanical extraction fans in the evenings and overnight to expel any excess heat. The excellent results are due to effective design and good insulation in the walls and ceiling, no architects needed. I have in recent years considered adding double glazing to the north facing picture windows, but have so far not found it to be needed.

[sarcasmunlimited]

When it gets really hot, yours house becomes passive aggressive.

[patrickmun]

Thanks for sharing; I love this style of construction especially when dealing with climate change

[vonnnner]

Great video and build – well done!

I've been curious about something: Is there an HRV/ERV system that uses two same-size whole house fans, one for intake and one for exhaust, connected to a smart switch? The idea is that on hot summer days, *if* it's cooler outside in the early morning, the smart switch could auto activate the fans to flush the house with cool air, helping it stay cooler throughout the day. Does a system like this exist?

[And-cn]

Great video and thank you for sharing but while it is true that the exterior of the building and air tightness is important, and glass shading is crucial, the insulated thermal mass of your slab is really what is helping you to ride out the day heat and into the generally cooler night cycle with lower energy use - lag time + coupled with clever sensible design - which you have shown. There is good material available on performance benefits of light coloured cladding (such as Coolmax roofing) but you are right that overall design is probably more important - but bad structual design coupled with dark colours will make things worse.

The thing with your dark walls is although it does suck in more heat it seams that material plus the backing arrangement provides little thermal mass for that heat to sink and radiate from for hours - which is why brick walls isn't the best exterior cladding for many climates. The vent system behind the tin walls may provide some venting but most of the heat heading internally would be radiant heat which is in the infrared spectrum and doesn't vent via convection - I assume you know this which is why I don't see any of those whirly-birds on your roof - good choice. But it makes me wonder if you have a reflective barrier in your walls (vapour permeable) which is reflecting the radiant heat out (25mm air gap required). The other negative for dark colours is that it heats up the surrounding neighborhood (urban heat island effect).



I have just replaced my concrete tile roof with Mars terracotta from Monier which has a lower SOI compared to the prior roof. With terracotta having more thermal mass SOI is important. I also have R6+ glasswool insulation and non-reflective vapour-permeable membrane sarking (I am in Melbourne) which is essential when you insulate the roof cavity to a high standard to manage condensation on the back of a tile. It took a long time to explain to a well known roofing brand in Melbourne why you should not being using non-permeable silver sarking when you insulate thoroughly in a cool climate.

The bush fire smoke prevention you described is down to the filters and the capacity of the filter to screen out particles of sufficient size. With smoke being between 0.5 and 2.5 microns in size I would be curious to know what your particulate filter is capable of. In addition the ability to keep your home positively pressured with clean air really helps keep smoke out (noting your house is passive tight). This principle is behind clean rooms used by industry.

In regards to the Daikin heat exchanger cooling performance usually stops with an ambient external air temperature around 44-46C degrees at this point you are reliant upon your slab to keep the home cool (this is when ceiling fans become important for keeping the people feeling cooler than ambient - breeze).

Your additional air transfer fans are really good. But they also have a role to play in managing the stack effect in two story dwellings with open stairwells. Have you used these this way in your projects in addition to a HRV?

I really enjoy your videos and its really encouraging to see quality architectural design that doesn't cost the earth being promoted. I hope you get more subscribers and I appreciate being able to see some of your building designs and floor plans on your website and videos. It would be amazing see the project home builders promoting and building quality homes and not just the biggest thing with lowest efficiency they can ram on the block to unaware home buyers.

[shanereid]

That's great to see more Passive Haus content in Australia but man the comment about limiting what your Tennant's do was a little off.

[alfredodino]

Would be useful to discuss Humidity in relation to heat. Humidity impacts comfort as much if not more than heat.

[todd]

I have 2 questions, 1. Do you hace a recirc kitchen hood or make up air for hood. If make up air do u have motorized damper or fan for make up air? 2. If building when it is hot, I'm worried about portable air conditioning because its a tight house and we r supposed to vent the unit outside so not sure where the intake air will cone from. Won't be able to get our house AC unit for a bit. Thx

[andrewgoy]

great video mate, you've done it so well with a selffy stick (im assuming), looks pro....most importantly its great to illustrate to people that PH isn't just for Europe, love it..also what a great job your guys did with the fascia/cappings, its so hard to get that looking flat even after some hot days

[jacobburgin]

What was the budget for a house off this size? Would love to see a floor plan. Awesome job

[justcallmefrank]

What system do you use for air transfer? We're finding similarly that the north-west corner of our house is a bit of a warm zone also and the HRV isn't capable of mixing enough cool air for the heat gain.

FWIW we went dark Colorbond, although with a dark roof too because it was visible. With the ventilated cavities, it's performing great. Ironically the house is coolest around midday when the windows get a break from the east facing sun (we have shading yet to be installed).

[AKDanMusicMan]

On the east side of the house, why didn't you use a roof overhang to prevent summer sun from hitting the glass instead of having to utilize the roller shutters and eliminating all natural light from that side?

[ISARCHITECT]

Thanks for sharing the insights into your house. It's generated some interesting comments, many of which are worth contemplating. One that jumps out is the facade colour. Our practice (of architects) has been testing this out. We're on the Midnorth Coast of NSW and we put the same house through the NatHERS engine with Shale Grey roof and walls vs Monument roof and walls and the difference was 0.2 star. So negligible.
@FrankReif made the comment that ‘walking in front of a dark facade will feel significantly hotter during the day’. I’m not sure about that. Walking next to a white wall that is reflecting the heat back at you is more likely to be uncomfortable. Try being on a Zincalume roof on a sunny winters day and you’ll appreciate the heat reflection. There’s also a big difference between black masonry and black steel interns of how the energy affects the house or those outside it.

[alawoye]

One thing I would like to suggest,
Considering that you have invested in a in ground pool, depending upon the volume size and depth of it, you could have used it for the cooling of your interior space
If you had made a treatment ( like a live or faux plant overhang/pergola ) for shading especially on the high solar times of day, that water will stay cool throughout the day and easily below 20-22c even on the hottest days, if properly shaded, maybe using a light coloured pool cover during the day when pool not used and removing the cover at night ( to allow night evaporative cooling).

If doing this you could use the pools thermal energy to cool your interior space with a W2A ( water-to-air ) heat pump instead of the A2A heat pump you have, water is a much more superior conductor of energy use, while using far less energy than air fans and pumps

I’ve done this before in Africa and it works fantastically, easily shaving 40-60% off my cooling energy bill ( which is on PV), so a secondary unit (apartment) can keep their unit cool without affecting energy consumption

Something to consider or test using a thermostat probe in a shaded pool on very hot days to track water/ambient air temperature variance

[coachmindy]

I'm housesitting in a passive house and I asked the owner in advance if we could bring our potable air conditioner for upcoming heat waves. she said she'd rather us not because the house us designed to stay cool. I said "OH, so it actually gets cold in there during a heat wave, without air conditioning" She said she uses a fan and it's pretty cool in Summer. We'll here we are and the house will not go below 24 degrees. It doesn't matter if I set the base temp low, put it on auto or cool setting... the house does not cool itself at all when temperatures are 26 degrees outside. That's not even that hot for a Summer day yet the house has been the same temp inside as it is outside all day. 24 degrees is our night time temp. Meanwhile a healthy room temperature for sleeping (for optimal wellness) is 17-19 degrees. So essentially this passive house can't even get close to a healthy sleeping temp at night when it's not even a heat wave outside. This is pretty weak.

[soccerhomework]

What is the ceiling panels with the grid of holes? Is this for sound absorption? Make and model is appreciated.

[xyztnce]

Great video and I guess she likes you building angle but I don’t see any hot air or stale air tower chimney to evacuate the hot air out of the building. How you control hot and cold air flow in building.
I m not an architect but I have interest in passive home.
In USA/Mexico boundary they construct dome shaped homes with a small oculus opening at top of dome and temperature difference is 10 Degrees cooler than outside without AC.

[ArrestedAcorn]

wow you made it into our schools investigation booklet we have to watch your video lol

[wazzaracer]

one good thing about solar perform well on hot sunny days when running an air con is useful. I commend the use of small practical, sensible homes have stupidly large windows for the Australian climate. Dark colorbond colours also fade roofer will tell you that. Its stupid.