Eaves that conform to passive solar guidelines

Hi, anyone been able to get their volume builder to add eaves that conform to the following YourHome guidelines for shading north facing glazing?

"As a rule of thumb, eaves width should be 45% of the height from the window sill to the bottom of the eaves. Aim for consistent sill heights where possible and consider extending the eaves overhang over full height doors or windows. This allows the 45% rule to be simply met with the following standard eaves overhangs:

• 450mm where height is 900–1200mm
• 600mm for a height of 1200–1350mm
• 900mm for a height of 1350–2100mm
• 1200mm for a height of 2100–2700mm."

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

We're considering building with Metricon but have been advised that the most they'll do is 600mm eaves.

We'll have 2700mm high ceilings, and large windows and full height sliding doors on the northern elevation (to the rear). We don't think 600mm would be enough to make the most of the winter sun and block out the summer sun. But we don't need super wide eaves right around the house, as 450-600 is fine for the other elevations. Sounds like Metricon aren't keen on customising the home design to cater for these eave requirements.

Anyone been able to achieve this?

Thanks!

You will find instead that as part of your BASIX requirements that you will probably be required to have some sort of shading device fitted over those windows or have the glazing upgraded.

Stewie

Thanks Stewie, yeah we've opted for double glazing right round the home. We were thinking of some kind of louvre shading to extend the shading, with the louvres angled to let in sunlight at midday in midwinter.

Something like this: https://www.shadeco.com.au/basixapprovedlouvreawning

But we don't know how good that will look if we already have 600mm eaves just above it...

I'd go for 450 eaves. We're doing similar with the windows but may go for a shading device over the west facing windows. We will be having a parapet and eave all around the first floor but the lower ground floor windows will need some sort of shading not unlike what is shown in your link above.

Stewie

Thanks Stewie, yeah i agree with you. I think we'll go with the smaller 450mm eaves all around the home. Saves us about $900 versus 600mm, and we can spend that towards louvre awnings or a pergola across the northern facing wall.

Interested to get your opinion on our floorplan Stewie... This is a rough mockup I've done on Floorplanner.com factoring in our changes to the standard plan. Anything stand out to you that could be improved to maximise solar passive performance?

I think we'll get good light through the main northern wall where the kitchen and family room area is located.. Hoping the kitchen island area will be well lit naturally (it's about 3m from the rear sliding door), and that the top left bedroom doesn't block too much winter sun into the kitchen/family area after midday.

All feedback is appreciated.

Jeez I hate lots of volume builders. You do your best to learn about energy efficient building design (like passive solar design) - because many builders still don't seem to have a clue about it - only to be told something as simple as an eave can't be optimised to exclude summer sun.

Grrrrr!

Also be aware that double glazing has virtually no effect on radiation (direct sunlight). It's effective against conduction (hot or cold air in this case).

Double glazing can actually make the problem of overheating by direct summer sun worse. Inhibiting cooling once the sun is down & the outside temperature is below the inside temperature.

Yes, this! I was really surprised that this would be an issue, considering I've read several times that eaves are one of the easiest solutions to getting the shading right. i can understand that this might affect roof design and that it would require more design work, etc but I would have expected that if a client was willing to pay for it, it would at least be an option.

We can't afford an architecturally designed home, so we've gone the project home option and done so much of our own research hoping we get the design right and end up with a comfortable and efficient home. Hopefully we do!

And good point about the double glazing, thanks for highlighting that, makes sense!

I guess you've already factored in that those two bedrooms on the Western side will cop a lot of heat in the afternoon. I'd just make sure of the insulation on those walls is up to scratch.
I'm also not a big fan of coming into a house from the garage via a pantry.

Stewie

Agree with Stewie, western bedrooms are not a good idea.

If possible I'd be trying to flip the rear of the plan, so that all the bedrooms are on the east, the living area in the NW corner (with northern windows).

Hmm. Thanks Steve and ddarroch. Yeah going to be hard to flip the bedrooms to the east. I might need to reconsider this layout...

Hi guys, so you know how the YourHome website says, "As a rule of thumb, eaves width should be 45% of the height from the window sill to the bottom of the eaves."

Well I was just reading the "Energy Smart Housing Manual" on the Sustainability Victoria website, and they say that's an old rule. Instead they recommend...

"Eaves should have:
› A depth of 25% of the height of the window.
› An offset from the top of the window to the underside of the eave equivalent to half the depth of the eave."

- Page 38: https://www.sustainability.vic.gov.au/Y ... ing-Manual

So based on this "new rule of thumb", a 450mm eave + gutter allowance of 150mm, (totalling 600mm) should be plenty for a 2.7m height ceiling and 2.1m window height. In the "old rule of thumb" it would have required a 1200mm eave.

Does that sound right?
And when a builder quotes a 450mm eave, that's excluding the gutter yeah?

My head hurts...

Howdy!

Hey I am interested to see if you went with this build

I too have been stressing about eave sizing for the North Sun; the builder I am thinking of going with also does 45cm.

I was actually thinking of asking them to use 20cm "edge style" gutters to make sure I have enough shading, as I am looking at 2.1M windows.

I echo your final statement of your last post "my head hurts"

Hey JWJ, yes, we went ahead with 450mm eaves + 150mm gutters. Building is still underway, so don't know if it will be enough. Will report back once we're in.

If space allows put decidous plant in wedt facing windows

They absolutely have a clue. They just don't care about whether youe home is energy efficient or not. But as the name suggests, their business is based on volume, not on helping you achieve energy efficiency beyond the minimum.

The volume builder product is often flashy, supported by sales and marketing magic designed to make you FEEL a certain way so that you make emotional choices. Just look at some of the marketing. "Love where you live" or "youve found the one" etc.

It's a bit futile to get upset and annoyed at volume builders for not doing specific things you want that don't fit their "menu". It's like getting upset at water for being wet. There are builders who can give you exactly what you want, at a premium (custom builders).

Often there is a post handover solution (lik3 awnings, verandahs etc. But you need to think about this when choosing your design, siting and block orientation so that you don't end up in a situation where you just have to live with it.

gglecast , here is a diagram I did for a client quite a while back. You can play around with it by sliding the eaves out and the window sill down until you reach the desired result. The midday summer sun should read December not June. This is moot if your builder won't budge and as per nonames comment above, they will only do any variation if they can make money out of it..
http://i1212.photobucket.com/albums/cc455/stewiesno1/Picture1.png

Stewie

You may already know this but there is also a rule of thumb about glazing amount e.g in Adelaide the total glazed area (windows and glass doors) ideally should be no more than 25% of the floor area. Can have too much northern glazing.