Canberra Region Solar Passive Custom Build

Hi all, I've been looking for a place to document our upcoming build where I can get some good feedback and discussion happening with likeminded people, and given how much I've been looking at these forums over the last 12 months for advice, it seemed right to do it here.

Our story is this:

The location: Murrumbateman, New South Wales
The land: 6500 square metre block (land due to settle in January 2022) - north facing, approximately 54 metres wide by 120 metres deep
The people: Myself and the wife with plans for a family
The brief: A solar passive home built using conventional construction techniques
The builder: Classic Constructions

The background: My wife and I made the fairly impulsive decision to buy a block of newly released land in a new estate at Murrumbateman, NSW, in October 2020. We had no immediate plans to buy, and certainly had no plans to build. But we had the funds (mostly) and a keen eye on the Canberra property market. There wasn't much coming up in Canberra that we liked in terms of established houses, and then one day she saw an online ad for land that was releasing soon. I had the day off work, so I went out to take a look, and on a splendidly peaceful and rainy day I fell in love with the area immediately. We bought a block a day or two later and essentially had our pick of the lot. Our block should sit nice and high, is north facing, and should have a nice view to the hills on the horizon.

The obsession: I've always had a keen interest in architecture and design and I was immediately obsessed with house plans. In earnest, we started looking around at a few builders. We went to a seminar with a volume builder, Regal Homes, and their designer told us all about the benefits of solar passive design. After that, I was like Alice down the rabbit hole. Lots of research, scrolling through thousands of plans on pinterest for inspiration, and drawing, drawing, drawing.

Building solar passive just makes sense. If you're planning a new house and don't at least cast your mind toward a few of the very simple principles it utilises, you're robbing yourself of the opportunity to live in a thermally comfortable, energy efficient house without having to do anything too out of the ordinary.. Particularly (as in our case) where you've got a large rural block and the freedom to place your house as you please.

What I learned:
I appreciate there's a lot more to it than this, but the key solar passive principles I was applying when coming up with our plans were essentially these:

• North light is king - minimise or eliminate east and west windows as much as possible, keep smaller windows on the south side, and use tons of glazing on your north side
• This means getting as many of your main living areas to the north of your plan as possible, and sticking the lesser used or more utility type rooms like the laundry to the south
• Orient the house as best you can toward solar north, not magnetic north
• High thermal mass in places the winter sun will filter through to - e.g. polished or burnished concrete floors in those northern living spaces, strategic brick walls placed inside
• Deeper eaves on the north side, calculated to completely block out the higher summer sun, but which allow all the lower winter sun to penetrate your north glazing and heat up those high thermal mass features inside
• Those high thermal mass features store heat from the sun from during the day and release it all back into the house during the cool of the night
• Try to allow for good cross-ventilation, particularly of your living spaces
• Good air tightness is critical - you don't want to be airtight to Passive House (aka PassivHaus) standards, which would require the house to be mechanically ventilated. But you DO want a builder that understands where leakage occurs and realises the importance of sealing properly around windows, square set cornices, avoiding penetrations in the ceiling etc.

At this stage, I want to give a shout out to yourhome.gov.au. This was in invaluable resource for learning everything an amateur could possibly need to know about building a solar passive house (particularly with regard to calculating the depth of those eaves).

I also want to mention The Booken House on Instagram. This is an example that takes the solar passive idea to the extreme, but is a perfect illustration of what can be achieved using conventional construction techniques (and therefore on a normal reasonable budget). Her results also appear to be quite amazing, and were quite inspirational for me.

The plan:

Over time I taught myself how to use SketchUp, which is a brilliant free to use CAD program, and used that for most of my many, many plan iterations. Shout out as well to Home By Me, which is a free interior design program that was great for drawing basic plans and awesome for furniture mapping (it also does neat 3D rendering of spaces).

Below is what I eventually came up with and is what we've submitted to the builder's architect. It closely considers not only the above principles but also how we live our lives and how we anticipate living them in the future. We've told the architect to change anything he sees fit, but he told us it was a nicely resolved plan and only suggested a few things:

• Rejigging the front a little to get more morning light into the kitchen
• Moving the powder room toward the mudroom/laundry (a great idea for when doing yard work, or if we eventually put in a pool)
• Widening the study and window seat section between the living and bedroom pavilions
• Consider moving the garage to the west side (this would be ideal as it would mean it absorbs the hot afternoon sun, rather than the sun directly striking the side of the house. However, the fall of our site would mean it would need to go on the front of the house, which is IMO a waste of some of our northern frontage, and I'm also keen to hide it around the side of the house because I think garages aren't all that nice to look at, PLUS our gate is on the eastern end of our front boundary - so it'll stay to the east)
• Roofline changes - roofs are really hard to do in sketchup so a few of them were drawn flat just due to my own limitations with the program

The above plan takes inspiration from heaps of different plans. I realised pretty quickly the ideal block is actually probably one that faces south, because there are SO MANY awesome plans with living spaces all oriented to the backyard of houses that are designed for south street frontages (mainly for privacy reasons, I suppose). For houses that face north and have northern views, it was incredibly challenging to find anything that worked. Hence my struggle to come up with something unique.

Important to note:

• Polished/burnished concrete in all north facing rooms, carpets for comfort in the southern bedrooms
• Heaps of north glazing (the architect also pointed out it can be possible to have too much glazing even with solar passive designs and there is a ratio of glazing to floor space that should be adhered to - although its a trade off, because aesthetically, more glazing looks more amazing)
• Only one west-facing window (small, in the bathroom)
• Zero east facing windows - only the entry door
• Cross-ventilated living pavillion
• We're planning on installing a 6.6kw PV solar system to take care of most of our power needs
• Having a good level of air tightness is super important (not to PassivHaus standards of course, or to the point where you'd need mechanical ventilation, but reducing air leaking is critical). The builder we've chosen prides themselves on their attention to detail during construction and, for example, uses high R-Value insulation as standard. They understand that I want to avoid unnecessary penetrations in the ceiling such as downlights or ducts for air conditioning, as in most conventional homes these are the sorts of things that contribute to massive heat loss.

There are loads of reasons from a lifestyle perspective the plan has been designed the way it has, but I'll mention only a few:

• We love the dual pavillion style (one for living and master bedroom, and the second which can be closed off for heating efficiency and noise related reasons, intended for guests and our eventual children)
• We wanted a place that was large enough to be in-keeping with the big family homes in the area, but not huge. This is because we like a cosier feeling home, and bigger homes are less energy efficient and more expensive to build. This plan has only roughly 230m2 of living space, so it's by no means a monster, and would probably be considered quite small for the area. We think it strikes a good balance.

Here's some sketchup renders of a slightly earlier iteration of the above plan. This is to give an idea of the scale of glazing I want to achieve and the materials we like:


Sketchup is also amazing because it has allowed me to model the shadows on the house in winter verses in summer. This has given me a lot of confidence that the place won't overheat in summer, because as you'll see, those eaves are putting in work and completely shading the glazing in summer.


1:00pm on summer solstice


1:00pm on winter solstice

So, in the dead of winter, we should have sunlight galore streaming in and heating up that concrete slab and internal brickwork, to be slowly released overnight. In summer, we're totally shaded, so nothing is absorbing heat. Then, as the seasons change, the amount of sunlight we'll get inside will change appropriately. For example, here's 10:30am on October 5:



So cool.

The undecided:


At the moment, I have no idea what to look at in terms of supplemental heating and cooling. I believe the solar passive design will do most of the heavy lifting in terms of heating, and ceiling fans and cross ventilation should be mostly sufficient in summer. But there's always long strings of rainy winter days where there's no sun at all, and strings of blistering summer days, to be wary of.

As I stated earlier, I want to avoid any/all ceiling penetrations to minimise air leakage, so that effectively rules out ducted air conditioning.

Budget permitting, I would like a wood fireplace, though that'd be more for occasional use rather than daily use.

Through my research, I think one split system air conditioning unit in the living pavilion should do the trick for any supplemental heating in winter and cooling in summer. That's assuming we do achieve a decent level of air tightness during construction. Possibly, I would put one in the lounge room in the bedroom pavilion as well, which I would think would flow through to most of those bedrooms fairly well. As a bonus, these systems would also be supplemented by the solar if used during the day, if there's any sun at all.

I'm also 50/50 on whether I favour a darker external colour scheme or a lighter one. Originally I was in love with recycled bricks as a feature, coupled with dark standing seam colourbond cladding. But, apparently, a dark roof on a hot day can have effects of an additional 10+ degrees within your roof cavity.

Now I think I may have come around more to the idea of recycled bricks as a feature coupled with horizontal, wide Stria (James Hardie) style cladding in white, with a light coloured roof.

Not sure...

Anyway, I could go on for hours. At this stage, I'm very excited to see what the architect comes back to us with based on the brief we gave him. I welcome any comments, questions, feedback, your experiences with solar passive design... anything at all. Let's nerd out over this

You might consider hydronic in slab heating driven by a heat pump.

Effectively silent, supplemented by your thermal mass it will transfer heat to your southern rooms, and on a timer to make the most of your solar and/or off peak electricity

That's something we looked at very closely before I went down the solar passive rabbit hole. From experience it's certainly a lovely radiant heat and we were very keen on it.

Downsides are the upfront costs to install, and given how long it takes to heat the slab up or cool down after use, it's not particularly responsive.

A while ago I read the blog of a fella who did a solar passive renovation/extension and did in slab hydronic heating in Melbourne. Unfortunately I can't find it again - it was a great read. He essentially said if he had his time again he wouldn't do the hydronic heating because it wasn't responsive enough to just supplement the heating needed on particularly cold days, and on other days the house actually had a tendency to overheat when it was used. It was an expensive experiment which proved unnecessary in the end.

With that said, a radiant heat is so much nicer than anything circulated by a fan. I wonder if hydronic wall panel heaters would be any better for our needs?

Good for you.. in 3D Bim modelling your Forever House.
If you are really keen you might want to consider certified
CFD FEM Engineering Simulations Do you have spare $10K?
Cheers
Chris

I'm sure sketch-up isn't a 3D BIM model. It doesn't contain any information about material quantities and specifications. You're always advertising 3D BIM modelling so surely you would know?

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OP, good effort on picking up sketch-up tool! it's a great software to build a free walk-through model of your house while being able to play around with the lighting 365 days / 24 hours a day! With furniture placement really gives you good sense for scale of things without needing to fork out $3k~$5k for a 3D model from the builder.

Just remember that the passive solar guidance on yourhome makes a lot of assumptions, with one being air tightness like you said. Considering you're on a 6000sqm, would you be leaving the balcony door open frequently in the summer when you spend a lot of time on the balcony? We like ducted evaporative cooler in summer because it lets us leave a lot of things open rather than keep things closed (but it doesn't work as well on certain days).

I'm also curious if skillion roof will be hotter as you lack the roof void space in comparison to the usual hip&valley (which can have a lot more layers of insulation to avoid heat loss if you desire)? Just a thought, sorry i'm not being too helpful but i too love thinking about these things!

Try searching Sketchup Bim Add ons
You are right why would anyone fork out $3-$5 k on an artistic BIM model to position 3D Warehouse furniture....
The funny thing is they do for engineering Bim 3D Models, Multiphysics simulations, Data/proofs, compliance certification etc and I'll throw in material quants and their engineering properties for free (Humour)
Heres an example where CFD ( fluid flow) modelling helps
OT, Say you live in close proximity/overlooking an industrial port with multi million dollar views?
The rich home owners would be interested in contaminant particle tracings (ppm) through open balcony doors
into their living rooms.... no views are worth dying for?... get it...
Cheers
Chris

It's pretty clear the OP has not included BIM into the 3D model, which is totally fine as he is using it as tool to check out space and solar access.

Multiphysics Simulations and CFD on a residential single / double story??! Just as much rip off in engineering as you suggest builders are ripping off... might as well run aerodynamics on a toddler's tricycle design.

Just a lot of fancy jargon terms & pointless abbreviations to sell to those who don't know better. OP came in asking for feedback with regards to the passive solar design and as usual your reply is to sell these engineering simulations!

Try educating yourself
Is Ray Tracing a FEA
Ray Tracing Simulations are Engineering (Coupled) Simulations
Should we show clients Crushing Realistic global warming simulation effects?
Probably not and
Building your Life time investment isn't a gaming experience.... my2c

You can get a multi split system.

All the internal units run off a single outdoor unit, the internal units can be mounted in walls, floors, ceilings, bulkheads etc, pretty much anywhere.

Each internal unit gets its own copper run so no ducts cut into the roof space.

More efficient than ducted as you're only running the part of the system you need not the entire thing.

Better for temperature control as well as each room is conditioned separately.

https://www.mitsubishielectric.com.au/a ... e-2019.pdf

Heya Spazzen,

Do you not end up with a little unsightly indoor units in every room / area you want to cool and heat? I was looking into this earlier but this was my main concern. The ducted seem better aesthetically and supposedly they can now cool separate zones at different temperatures?

Our builder actually does 3D modelling as standard which we'll get access to in the next planning stage. It'll do the lighting and shadows much more accurately than I ever could with my sketches, I'm sure. Aside from that, I may consider some thermal performance modelling with someone like Lighthouse group further down the track, but I think that's about as far as I can justify going.

I think the intention in summer time would be to leave the doors open a lot. Ideally I'd like to rely mainly on the thermal mass, cross ventilation and ceiling fans for summer cooling, with supplemental aircon only to be used on those extreme days. With that said, everything at this point is an unknown and it would be slightly unnerving to not have a reliable backup option installed at the build stage that will also serve as a good long term, regular use option if it turns out it's needed.

I'm assuming the ducted evaporative cooler uses ductwork in the ceiling similar to a ducted air conditioning system? If so, I'll effectively have to rule it out. Canberra is a heating dominated climate so my main concern is trapping the heat in during winter - hence I don't want ducts in my ceilings.

I actually raised the skillion roof question with the architect and he wasn't concerned. I can't remember the intricacies but rather than relying on batts as you would in a hip/valley roof, I believe there is some kind of specialised foil-like insulating layer that goes directly under the roofing. I could however be completely misrepresenting what he said and be way off the mark, but regardless of how it's done I don't think there's much to worry about in that respect. I would actually think a hip/valley would be worse, because you're creating a big void space for a lot of hot air to get trapped in without much ventilation. Again, just speculation though!



Thanks so much for this info. I didn't realise this was how a multi-split worked so I will 100% look into this. Sounds like it may very well be the solution I'm after, rather than putting two separate indoor units with their own individual outdoor units. Good to know there's no ducts to join the indoor units. Cheers.

[/quote]
Heya Spazzen,

Do you not end up with a little unsightly indoor units in every room / area you want to cool and heat? I was looking into this earlier but this was my main concern. The ducted seem better aesthetically and supposedly they can now cool separate zones at different temperatures?[/quote]

It depends on what sort you get, the old school traditional split system has a big wall mounted unit, but there's lots more options now.

I'm having ceiling cassettes installed which are flush mounted with the ceiling, a little bigger than a ducted vent, but not by much.

They look similar to this.

https://www.appliancecentral.com.au/ima ... 00x800.png

You can get individually zoned ducted systems with automatic dampers linked to a temperature sensor in each room, it certainly controls the temperature better than regular ducted, but I've used it before and it's far from perfect based on the way the air return works.

With ducted the air has to get back to the return vent, that can mean doors slamming from the air pressure when you go to close them and then the cooled(or heated) air rushes out under the door of the room you want to cool back to the return.

So if you're like me and only want to cool one or two rooms at a time, say your bedroom while you sleep you'll be paying to cool the hallway or wherever the return is.

With a split in a bedroom for example the return is in the unit so no air leaves the room, you only pay to cool the room you're in.

That can also be an issue with leaky houses, a ducted system can push cold air out of the house and then suck warm air in near the return because the return will suck air from the point of least resistance, that usually means some of it gets pulled through all the various air gaps in a house.

They all do the 3D Modelling spiel as standard , LOL, that's what hooks the clients into paying for the next planning stage and then the next stage and so on?
Architectural 3D Bim was suppose to "according to the 3D Bim Curve ?" shorten, optimise, Blah,Blah the Building experience
I have to admit as an early implementer in Architectural Bim in housing it's has been a big failure.
Contrary to the Bim I see in other Industries like infrastructure and Mining.
Pity most Battlers and Punters gets their pants pulled down at the 2D Engineering stage.
It will be good to see what your progressive builder is offering you.. I hope it's not the Mushroom Treatment


There are no codes for Shadowing fake Images
.. if it's wrong then grow a vine over the side of the house (humour)

Ahhhh thanks for that! the ceiling flush cassette definitely looks better than the old wall mounted units. I'm guessing you can cool / heat large open plan kitchen/dining/leaving as well?

How's the initial / upfront cost of the multi-head system for a typical 4 x 2 house, compared to ducted?


If you have ducted aircon but with 2-3 units (1 unit powering small beds, 1 unit powering kitchen / dining / living, 1 unit powering study / master for example), is that somewhat similar to multiheaded system u reckon? kinda middle ground maybe?

Yeah you can cool large areas, the unit for my living area is 9kw.

Cost for my build was about the same as ducted, it really depends though it probably costs more than a basic ducted system, but if you start adding individual temperature sensors and dampers in each room in a ducted system that costs more too and I'm sure some indoor units for split systems cost more than others.

You can have multiple ducted systems, but they sometimes fight each other, it normally works where there's a clear separation, as in one ducted system downstairs and another upstairs.

I believe you can even get a multi system that has ducted, so you might have a ducted system to the living areas and splits to the bedrooms but it's still a single outdoor unit, I don't know much about those though.

for best passive design in a sometimes cold wet climate i suggest that you include more doorways to zone separate areas of the house, include some east and west windows for late afternoon and early morning sunshine and i've included a few ideas for consideration

Wow, thanks so much for taking the time to draw that up! There's certainly some very well considered ideas there. Particularly the pantry/powder room/mudroom setup, I think there's a lot about that I really like and I wish I'd made this post before our meeting with the architect. Although, based on some comments he made, I imagine we'll end up with something similar.

With that lounge room in the bedroom pavilion, it certainly works as the open rumpus room kind of setup you've drawn, but I think practically speaking it would be important for a growing family to be able to close it off for noise reasons. I'm just thinking long term as it being a space for teenagers to stay up and play games, watch movies etc. But still, it works so well the way you've drawn it that I'm probably going to start second guessing myself.

With regard to the east/west windows, almost all of the reading I have done has said to minimise or eliminate them where possible so I'm not so sure about that. I think that early morning and late arvo sun would have a tendency to overheat rooms in the summer months..

my suggestions about east and west windows are based on living and building in a similar climate and finding that between seasons tends to be cold in a house with only north facing windows and eg the window in the family bathroom helps add light and sunshine on cold afternoons and the eastern highlight window will brighten the ensuite bathroom long before sunshine comes in the north facing windows and small windows are easy to add external shutters for hot weather and room sizes need to be based on furniture and activity...i made the small bedrooms similar size to my estimate of your original plan but i think the bedrooms could be comfortable at 3m x 4m plus wardrobes and the lounge could be bigger to make it possible to add a separate hallway if needed

Hi,

Great read, do you think the raked ceilings will be okay in the cooler months?

How will you cross ventilate, recycle air? Low windows, high windows, sliding windows, fly screens

Thanks Pedro. I guess the ceilings will create a larger air volume that will in turn require more energy to heat it. I'm banking that it'll still be a comfortable space, but if it requires a bit of supplemental heating from a fire or split system on really cold days, I'm ok with that.

Re: ventilation - We're lucky in our climate here that even our really hot summer days tend to have really nice and cool evenings and nights. I used to live in Western Sydney where you'd often swelter through hot sticky nights one after another again and again. That's just not the case here, which is great, and from a solar passive perspective its important because you rely on the cool of the night to cool off any of the heat your thermal mass takes on during the day.

My plan is to have good security screen doors on the south side, so that I'm not worried about leaving the glass doors open at night. I'm hoping that if I have louvres up high on the north side that I can leave open at night, that will have a nice air flow over the slab in the main living space at night.

With the main doors on the north side, I want to get retractable fly screens similar to these so that I can have them open during the hotter days and not have to worry about insects. The way they retract when not in use, like in winter, means they're not inhibiting any of that nice sun getting in.

Great points, and I really do like the ensuite window to the east. You're right, it'd be nice getting that early morning sun into that space, but can be easily shuttered if it's an issue. Cheers again.