Owner build a solar passive house

Are you getting help from an architect, building designer or draftsman that uses Revit, as it has some very good modelling tools for sunlight?

For eaves and window sizing, it's very possible to go down a rabbit hole and end up overthinking things too much. When designing our new house, I spent many, many hours and days using various tools (including Revit) to work out and model exact eave lengths and vertical offsets, doing daily sun path and shadow analysis, calculating the exact ratios of each window area of direct sun/indirect light/shadow for each part of the year, all to maximise solar gain in winter and minimise it in summer....

The end result of all that effort? We have 600mm eaves (which are working just fine at shading all the windows in the current summer, and will still allow full solar gain in winter). Sometimes standards and rules-of-thumb do work.

Note that I'm not saying to not do any analysis, but my suggestion is to start with the rules-of-thumb at the yourhome.gov website. A basic shadow diagram of your proposed build at summer and winter solstices will get you 90% of what you really need, and you can then tweak based on that.

Hello Beetaloo
Hope you get this even though it is 3 years later .
I would so love to ask you some questions.
My husband and I have just moved to Wandering south of Perth ( a cold spot similar to where you are)
We so want to build a solar passive house here in the country. Our catch after our food retail franchise went cuput. Is the cost !! The designs we like though simple I’m sure will be expensive. Any direction you could give us
Thank you from donna

As my house is different to most houses that builders build, I built my solar passive house as an owner builder this way I kept costs under control.

Wow thank you so much for such a prompt reply . I wasn’t sure you would still be in this page now you are warm and cosy 3 years on in your home
We are just very nervous about owner building cost being way more than we thought. Quotes we get now by the time we need that job done it could be way more expensive. We are very much at the beginning stage and really not sure how to start. I have the rough design but nothing fixed.
It’s the $ which is the scary part. Builders and architects see $ when you want solar passive and not straight off the plan. The other idea was to adapt a kit home and have it built to lock up??? Also loaning more money when owner building is a problem.

Also how are you finding you home now 3 years on
Thank you 🙏

Donna, maybe you are confusing "passive solar" design with "Passivehaus" standards.

To be certified as Passivehaus, a home must be extremely air tight & well insulated. To achieve a home capable of meeting this standard costs a lot of money (particularly in cold climates), with high levels of insulation, double or glazed windows, vapour permeable wall wraps, rolls & rolls of tape, & a lot of attention to detail. These 'tight' homes must have expensive centralised HRV (heat recovery ventilation), or ERV, to maintain adequate ventilation, while minimising heat loss. Another costly addition.

In simple terms "passive solar design" is all about orientating the home correctly, to take advantage of the sun's movement throughout the year. Using winter sunshine, which is lower in the sky, to heat the home. While shading the home in summer, & using cooling breezes.

If you haven't already looked over it, I'd thoroughly recommend you read the brilliant 'Your Home' government website, all about sustainable, energy efficient home design,

https://www.yourhome.gov.au/passive-design

As the sun is in the predominantly in the northern sky in Australia (except the far north, where it dips to the south over summer), this means orientating living areas to the north. These rooms will be light, warmed by the sun in winter, & shaded by adequate eaves in summer.

Simple really, & no more costly than any other build (kinda, I'll get to that in a minute). You've just got to choose an appropriate design. Living areas to the north, bedrooms to the south or east, rarely used rooms like the garage, the laundry & bathrooms to the west.

Additional cost will come about, if you can't find an appropriate plan. Which would often be the case, as not enough builders consider a home's orientation or energy efficiency to be important. A justified criticism of the current state of the Australian building industry.

If plans change to modified, it's likely costs will be increased (unless the plan is flipped, which is often free). If too many modifications have to be made with a volume builder's plan the process can increase a lot. In this case it's often better to go with a custom builder. Where you'll usually achieve a better outcome.

The other areas that will increase costs are the fact that you really should increase the insulation levels of the building envelope above the bare minimum. Australian building standards are extremely poor. The most areas of Australia the Your Home website recommends MINIMUM insulation levels for the ceiling to be R4.1, & R2.8 for the walls. At the time of the build is certainly be installing bulk insulation in the walls, as it's extremely difficult later. The most that will fit in a normal stud wall is R2.5, so I'd be aiming for that.

Upgrading windows is a very tricky one, as good quality, energy efficient windows are so much more expensive in Australia than in Europe & the US. In areas like Sydney it's not really worth the added expense, it's much better to spend those funds elsewhere, like on solar PV or energy efficient appliances. But in colder climates, like Canberra, double glazing is certainly worth the added cost (with either uPVC, timber or thermally broken frames - as aluminium is such a poor insulator).

The other thing with considering is the air tightness of the build. Australian homes are extremely leaky, you may as well go live in a tent sometimes!

The measure of air tightness is ACH50 ( air changes per hour @50Pa). This is when you see blower door tests done, which are a requirement in many developed countries.

Passivehauses must be extremely tight, with an ACH50 below 0.5. A home that uses standard building techniques, a vapour permeable wall wrap, care & attention to detail should achieve an ACH50 somewhere around 1.5. Every possible leak must be considered in this case. Around the window frame, skirting boards, even under power points & obviously seals in doors & windows. A good result for any home should be around 3. An average Australian new build is around 10-15!

So I'd look at the cost of including a vapour permeable wall wrap, & taping it, & any other sources of leaks.

If you're on FB, it's worth joining the Me Efficient Electric Home (MEEH) group. One of the mods there, Jenny Edwards, specialises in energy efficiency of homes. Getting very good results, in a cold climate, without too much additional expense. She is based in Canberra, but it may be worth checking out their website, & possibly contacting them,

http://www.lighthouseteam.com.au/

Oh, & if you do achieve a tight home - obviously not to the levels of Passivehaus, but somewhere below around an ACH50 of 3 - I'd be installing an HRV. Not an expensive, centralised HRV, like those required for a Passivehaus. Instead a couple of sets of simple, & much cheaper, decentralised HRV's. Two options are Lunos & Stiebel Eltron.

Thank you so much for taking the time
To explain so much to me. The passivehaus is a whole next level we hadn’t really got that far . It’s more like you said, finding a plan the fits the north and the views we have and build in the country. Surely more building companies should be focusing on passive solar as standard !!!
I will check out those links and MEEH.
And do some more reading into wall wrap.
Thank you again I really appreciate it
From
Donna