6 Star+ dwelling, heating/cooling Watts/m^2 required ?

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6 Star+ dwelling, heating/cooling Watts/m^2 required ?

Postby franks » Sat Jan 11, 2014 2:36 pm

I have planned at least 6+ star dwelling, heating cooling/heating typically 80 to 100 watts per square metre required for average dwelling.
Can I assume typical pre star rating home is around 2-3 stars ?
Each star inprovement is aprox 10% less energy required. (3 to 6 star 30% less)
Would I need around 60 watts per square meter for 55 metre dwelling (granny flat shed conversion).
Wolud a 3.6kW aircon/heatpump be enough ??

Please comment with suggestions and Ideas.
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Re: 6 Star+ dwelling, heating/cooling Watts/m^2 required ?

Postby Tracker » Sun Jan 12, 2014 7:55 am

.
FWIW... I know nothing of star ratings, and measurement... just practical and obvious ways of achieving such..

now you ask about a RAC and appropriate size..

I chose to adhoc add RAC systems in answer to evolving domestic needs.. I think that it is pretty efficient..
eg the family room is about 56m2. and has a 1.5kW split which easily keeps that comfortable.
The other room most commonly used, is the office at the front of the house.. a similar unit works well there.. The two running, easily keeps the bulk of the lower floor comfortable.. probably more like 150m2..
and so moving from one area to the other (via the kitchen etc.) is very acceptable..

we do have the second floor, and that is another story.. but we believe that using small units, distributed, gives us efficient climate control..
I must admit that I would like to start again with small units with better COPs... I used cheap Chinese units and have NO IDEA on their COP values..

the standout in my mind, is the use of a small cooler in the master bedroom (GE Skinny) which is more like. o.5kW , and it keeps us very happy on stinking summer nights (25m2...)

So, with something like a granny flat, I think I would be looking for two units.. a very small unit in the main BR (even cool only) , and a 2kW reverser in the main living area..
..
.
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Re: 6 Star+ dwelling, heating/cooling Watts/m^2 required ?

Postby Graeme.Ambrose » Wed Jan 15, 2014 8:44 am

You can get reverse cycle with COPS and EER exceding 5 now. and they use around 500W which gives an effective heating and cooling of 2.5 kW. This should be more than adequate for a six star flat.
Try to get one without a sump heater or if it has one get it disabled. They consume between 30W and 60W 24/7 even when the unit is switched off.
One thing to take into account is window coverings. Ideally heavy curtains and pelmets and try to avoid aluminium frames.
There is no point in heating a space if the heat is going straight out of the window.
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Re: 6 Star+ dwelling, heating/cooling Watts/m^2 required ?

Postby Cherokee Solar » Wed Jan 15, 2014 1:48 pm

The star system makes it easier for the building industry to comply with the standard, rather than being an effective system in itself. That is not to dismiss it outright, but it is worthwhile considering methodologies outside of the star system.

The old timers used to say "weatherise before you solarise".

This basically means to make the house as passive as possible so that it reduces the flow of energy inside and outside of the house.

A good example is veranda's versus a small overhang of the roof which most buildings have. The small overhanging is cheap to install as it simply requires a slightly larger roof truss. The veranda on the other hand requires far more materials and posts, but is far more effective at keeping the sun off the external walls of the building.

Tile roofs are another example. They're much cheaper than steel roofs but are virtually unsealed. Stand inside a roof cavity on a windy day and you'll feel the air moving in that cavity. Add a few downlights in and the air moves into the dwelling.

The list goes on and on. Most people want a big house, not an efficient house. I have no a/c here and it is pretty reasonable inside given the heatwave going on right now.

Tracker wrote:we do have the second floor, and that is another story..


Tracker,

Man, I feel sorry for you. People love two story buildings because you get more floor space for less cost. But, the second story suffers from the chimney effect and can be unbearable in summer. The old timers used to put a cooling tower in the old two story houses which drew out some of the hot air over summer. Good luck.
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Re: 6 Star+ dwelling, heating/cooling Watts/m^2 required ?

Postby Warpspeed » Wed Jan 15, 2014 3:31 pm

Cherokee Solar wrote:Man, I feel sorry for you. People love two story buildings because you get more floor space for less cost. But, the second story suffers from the chimney effect and can be unbearable in summer. The old timers used to put a cooling tower in the old two story houses which drew out some of the hot air over summer. Good luck.

Yup, two story is an energy disaster.
Two story brick is an energy disaster plus an energy catastrophe, in either summer or winter.
If you need the extra space on a really tiny block, go down not up, with an underground garage, workshop, laundry, junk room, and maybe a spare bedroom or two.

Its not rocket science.
Single story, very wide eaves (or a verandah) at least to the north, and very efficient roof ventillation and massive insulation.
Even insulate the interior walls between rooms. Your builder will laugh at you, but you will be the one laughing last, when you only wish to heat or cool particular rooms at peak winter or peak summer.
And there is zero chance of doing it once the house is built !!

Desiduous trees give summer shade and winter sun.
Falling leaves in autumn are a damned nuisance, but its well worth it.
If bright direct sunlight onto windows cannot be avoided, fit high tech reflective window glass.
And if its really brass monkey freezing (very rare in oZ) or for horrendous traffic noise, maybe even double glazing.
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Re: 6 Star+ dwelling, heating/cooling Watts/m^2 required ?

Postby Graeme.Ambrose » Wed Jan 15, 2014 4:21 pm

A simple solution for two storey (or higher) houses is to put a vent in the ceiling that can be opened in summer and closed in winter. This vents the hot air into the roof space. If you are built on stumps or have a cellar or something you can put some vents in the floor. The negative pressure created by the hot air escaping will drag cool air from below into the house.
It is called stack ventilation.
In my office downstairs ( under the house) it is 23.9 degrees. It is 45 degrees outside and I don't even have a fan in here.
I can vent this cool air upwards at nighttime and cool the rest of the house.
Works for me.
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