Better than passive solar - active solar

Houses like the one we built based on passive solar design are intrinsically more effective to heat and cool because their orientation and shading mechanisms optimise warming sunlight during winter but block out the hot summer sun.

They are a 'passive means' of making use of the difference between the sun paths during the year. With minimal input from the user, they greatly reduce artificial heating and cooling requirements compared to an normal house. Of all the ways to make an house energy-efficient this method is the most effective cost-neutral method.

However, there are disadvantages to a purely passive system:

1) They are based on the average expected temperature and sunlight through the year and without additional intervention by the occupants do not cope with aberrant weather conditions or year-to-year variations.
2) The fixed length of the eaves reduce the potential to introduce more sunlight on colder than average days or block additional sunlight on hotter than average days.
3) Most conventional window schedules result in the top portion of the window remaining in shade most of the day. This is particularly an energy liability during winter. The alternative solution are to use skillion roofs or uptilt eaves. Either are problematic of design either when locating solar system on the roof or designing gutter systems.

The alternative requires a bit more intervention by the owner but have the potential to control the comfort conditions of the house...

Unlike passive solar design, all north eaves are abandoned. Instead a flexible system of shading is introduced to the house. This may involve pivoting awnings that can fully retract, adjustable shade flaps (as decribed in Derek Wrigley's) book , a pergola structure with horizontal retractable shadecloth or an automated louvred system.

The shades can be left in a appropriate position depending on the time of year. However, on occasions when this is not adequate they can be manually adjusted to improve the comfort in the home on any given day.

The main drawback to this system is the added intervention of the occupants and the requirement of a robust enough system that allows occasional adjustment. There are also some issues with allowing excessive rainfall on the walling structure and windows.

However, it provides an elegant method of completely controlling sunshine depending on the weather at the time and possibly requires less window area than a pure passive design.

Yes active, quite so
We have shading plants that are deciduous
Meaning they loose their leaves during winter allowing light to hit the concrete floors
...and in summer grow leaves to shade and cool through transpiration
...and I love my passionfruit pav the 'cheese and kisses' does a wonderful
job (cept the eggs are a bit yellow ) they go pink
The ponds bring the temps down at night quickly with a bit of breeze
And act as solar collectors in the winter as we run the system with around 2ppt salt
all things passive and a few things active but watch the cost, you have to do a cost analysis
to measure the offset
onc_artisan

The cost of active is mainly your own time and being vigilant. Not everyone's cup of tea. Passive solar is better if you don't want the hassle.

I enjoy pulling up the blinds (even for the unused rooms) as soon as the sun hits the north windows. It's exciting to see the sun strike the window during the winter. Today we didn't need any added heating until 2 hours after sunset.

Flexible shading system vary from the exotic/expensive e.g. electrical aluminium louvres to cheap-as chips such as Derek Wrigley's DIY Coolaroo shade flaps. This is offset against the savings on building materials used for eaves.

For those who like to do energy efficiency at a budget I would recommend his book. He is an architect who retrofitted his house in Canberra doing a lot of it himself or improvised components.

There is another alternative which is not much utilised for house environment control - that is automated systems - active without human intervention. For example a passive solar hotwater system is where the tank sits on the roof above the panels and the thermosyphon effect naturally draws the water around the system without pumps. The other solar hot water system is active and automated. This is where the tank is on the ground and temperature sensors and thermostat turn on an off the pump when sufficient solar is available. Neither system requires intervention from the householder.

So this could be translated into automatic control of shading and ventilation devices. But is adds to the expense of installing and operating and more things to breakdown or maintain. But I think there is some place for simple automated system in solar house design.

A bit like the difference between flying a glider versus flying an Airbus. The former involves a person interacting closely with natural forces (but prone to human error) but the other allows use to push the boundaries of what is possible (but you place your trust in a computer).

It may give more options for home designers but there needs to be some way to manually override the system if it breaks down.

Who knows what the future holds? Technically you could have a multitude of sensors measuring air temperature, radiant temperature, humidity and air movement coupled with the personal comfort preferences of the occupant. This could be integrated into a complete set of simultaneous interventions - pull a shade, crack open a window, switch on a fan, open a vent....

Thermostat and solar roof ventilation = perfect