Passive solar house build

[lencolad]

Passive solar house build.

Step one – build a stud frame house on posts and bearers when young and dumb because it’s cheap and easy to build.

Step two – realise that it is hot in summer and cold in winter because it has little mass and is poorly insulated anyway.

Step three – get older and smarter.

 

Okay, so the trick is to achieve thermal stability (in a temperate climate that has nights that are significantly cooler than days in the summer) by having a lot of mass that is surrounded by a lot of insulation. Should take a long time to cool down in the winter and a long time to heat up in the summer if done correctly.

So how is it done ?

Winter – the sun is low in the sky and should penetrate the house’s interior to heat it, and there needs to be mass to absorb, retain and emit the heat at night.

Summer – the sun is nearly overhead and should not shine in to add heat.

Easy. Only it isn’t because there are some things called solar maximum and solar minimum and thermal maximum and thermal minimum to juggle.

What this means is that the shortest day of the year (June 21 ish) isn’t the coldest day – that comes six or eight weeks later. Similarly the summer solstice (December 21 ish) isn’t the hottest day in summer and that is about eight or ten weeks later.

What this means in practice is that in March (eg at the equinox on March 21) it can still be very hot (where I live anyway at 33.5° south latitude) whereas on September 21st it may still be quite cool. On those days the sun rises and sets at the same places on the horizon (the azimuth) and rises to the same height in the sky at noon (the altitude). In other words it follows the same path across the sky on those days.

So if you gain a lot of solar heat in March that’s a bummer whereas you want to gain that heat in September / October. So there’s a bit of cunning planning to do.

To get the heat in the winter there needs to be glass facing north, and to avoid the heat in the summer there should be a decent amount of shading in the east and west. And shade is needed in the north later in the summer when the sun is lower and trying to shine into the house a bit more than it does in December / January.

Now the eggheads amongst us will ask ‘what is the ideal internal mass for a given internal volume to achieve thermally stability ?’. I dunno the answer to that despite some research so I made it up as I went along as you would if you’re a typical bloke.

 

I went to an auction and bought ($12k but probably $50k new) a heap of 2.6 m high double-glazed windows that were the display stock in a commercial glass-fitting outfit. They have aluminium frames with thermal breaks (ie. plastic segments in the frames to separate the inside and outside aluminium bits) and argon gas in the space between the two glass panes and also have low-E glass (google it).

Then I designed the house around these windows, putting them on the north side and NE and NW corners. The other windows (bought new) are the same but triple-glazed and cost $4.5k – could have paid two or three times as much without a bit of hunting around.

A significant feature is the external insulation on the exterior walls. These are rammed crushed limestone with 10 % white cement sheathed in aircell insulation. Stud frame (75 mm) steel is dynabolted to them and 75 mm earthwool batts (R 1.5) are added then 75 mm freezer panel (R 1.5) is glued onto the outside.

The roof is 200 mm freezer panel (R 4) on aircell on steel trusses. The ceiling is 13 mm plasterboard with 200 mm earthwool batts (R 4).

The slab is 100 mm concrete on heavy strip footings to support the weight of the external and internal walls (about 60 tonnes). The exposed edge of the slab isn’t exposed – it’s covered by freezer panel cladding. I thought of insulating the slab but decided it was better as a heat sink in summer if uninsulated. I also thought of hydronic heating (water pipes) in the slab and/or walls but decided against it as I wanted to finish the house this century.

Some of the internal walls are rammed (300 mm instead of the usual 200 mm to add more delicious mass). Other walls are steel stud frames with plasterboard. The freezer panel came with a heap of polystyrene spacers so these were stuffed into the stud frames.

What is freezer / coolroom panel ? A sandwich of colorbond steel / polystyrene / colorbond that is used to build coolrooms. It has great spanning ability but I wanted a roof space above the ceiling for installing services so they sit on steel trusses, but because they weigh more than twice as much as colorbond then the trusses must be closer together. So more trusses are needed.

I realised later (not so smart …) that I could have just gone the conventional roof route and filled the whole roof space with batts and saved a heap of money, but I get a smooth underside to the (insulated above) verandahs that is easy to de-cobweb. This underside is thermally conductive into the roof space (summer bummer) and I thought of slotting it above the external walls but decided that was insane. Even for me.

 

The result is a one-bedroom one bathroom house with walls that are 450 mm thick.

To get experience with the freezer panel I used it in a mancave to live in whilst building the house. Steel shed frame with 75 mm walls and 100 mm roof that is pretty good thermally but I added an aircon in the second summer. Plenty of glass on the north side so very warm in winter.

Of course there’s solar hot water, solar electricity and a wood stove in each structure. A wood stove heats water, bakes, has a cooktop and provides space heating. The flat panel collector on the mancave is pretty good but the evacuated tubes on the house are superb in terms of efficiency.

Took five years from buying the land to moving in but I had to earn money as well as build. And plant a few trees as well.

Does it work ?  Yes.  Very warm in winter and cool in summer. On a 42° day it got to 28° but that was without shade sails or blockout curtains, so it will be better this summer and I ran cables for aircon just in case.

I did most of the work with the help of mates but obviously didn’t do the slab or rammed walls.

 

the fridge sits in a gap in the wall ^ so that it is easily cooled by the air in the pantry.

note - the domestic squalor isn't usually so squalid but I took this photo ^ when the mad move-in was on.

note the yet-unsealed bottom of the window ^.  Fellow sparkies won't like the light switch next to the cupboard near the sink - it's for 12 volt emergency lights.

Edited July 13, 2016 by lencolad

[proftournesol]

We've gone down a slightly different approach. We live in a sub-alpine environment, cold in winter, often -4 degrees overnight, but very hot in summer, up to 45 degrees. The thing about summer though is that apart from 2 or 3 nights a year the overnight minimum drops below 20 degrees. We decided that because of this we would build a well insulated  house with low thermal mass so that the house wouldn't retain heat in summer. We also decided to build a house without eaves as they are always a compromise between optimal shading in summer and allowing in winter sun. Instead we decided on sliding external shutters that we can close in summer (there's no real northerly view at our place) and fully open in winter. The shutters also help with our other issue - the view is to the west so we were faced with shutters or the alternative of very deep west facing verandah. We even went to the trouble of buying an insulated dog door from the US! The challenge for us will be to keep the heat in the house in winter but we're hoping that double glazing (also low E) as well as internal honeycomb blinds will achieve this. We are confident enough to have not installed a wood heater, just 2 reverse cycle aircon units and ceiling fans (Haikus). We aren't over-confident though - there's space for a wood pellet heater if we need it

 

We decided against solar hot water as even the most efficient systems need supplemental energy in winter and decided on a heat pump system powered by our rooftop PV. Sanden make a heat pump unit that ironically uses CO2 as a refrigerant and this can operate effectively well below zero degrees air temperature. We hope to add a Z-Cell flow battery later this year and hopefully the house will be substantially self sufficient even though it'll stay grid-connected. Ironically we need to stay grid connected to charge the car (Tesla).

 

Luckily for us we have a permanent spring so we'll be pretty self-sufficient. As well as being required to have a 10,000L water tank for the CFA we've installed 2 x 15,00L tanks and roof sprinklers that along with the shutters will increase our fire resistance, hopefully we can avoid AusNet burning down half of north-east Victoria again. We've also reduced our energy requirement by installing a reed bed sewerage treatment system so that nature can do the work with no energy input from us apart from 'number twos'

 

We avoided the issue of deciding between an insulated or uninsulated slab by getting a prefab that sits on screw piles that also create minimal site disturbance and we avoid the high carbon emissions that come from setting concrete. A passivhaus requires no active heating or cooling, summer or winter, we won't achieve that unfortunately but like you we'll need minimal active heating and cooling.

[lencolad]

My place has a lot of embodied energy but it will last for hundreds of years as long as the roof is replaced when necessary.

It is extremely strongly built too - trusses at 900 centres - you'd need explosives to pull it down.

Summer nights will require the windows to be opened to allow the warm internal air to rise up and out and let the cool night air fall in.

I may have to vent the roof space too.

 

edit - an interesting feature is the enveloping warmth in the winter - the walls radiate, the floor radiates, the ceiling radiates so it's like walking into a very pleasant oven. A mate visited the other afternoon and felt the wood stove to see if it was lit.

In summer you walk into coolness.

 

Today -

Edited July 12, 2016 by lencolad

[Soundscape]

This page has a lot of relevant info re solar passive design

 

http://www.yourhome.gov.au/passive-design/passive-solar-heating

 

We built a strawbale home based on these principles in the Blue Mountains. It is normally around 5-10 degrees cooler inside in summer and 5-10 warmer in winter. We have no major heating or cooling appliances.

Edited July 12, 2016 by Dave O)))

[lencolad]

Frosty this morning -

 

 

and cold outside but warm inside -

 

 

then the sun pops up and the heating begins -

 

[Guest]

What a beautiful habitat for Humans.

Have a lot of envy for the intelligence and for site you have as you would probably save enough energy in space heating over say 20 years to cover the council rates.

Green here as my old weatherboard home is a legacy of how not to "build a house" although after a couple of decades double glazing and insulating a room at a time has improved it some what.

Thanks for sharing

 

PS ever thought of installing a battery to pick up the remaining energy usage  ? 

[lencolad]

My pleasure.

 

I've got 2.5 kW of REC panels on an Aurora PVI-2000 2 kVA inverter on the cave and 3 kW of REC panels on a Fronius Galvo 2.5 kVA inverter on the house.

Planning for batteries either grid-tied or stand-alone would have been a good idea but I've had so much to think about and do so it just didn't happen but it could be done I guess.

 

One issue is the 2.2 kW 3 phase submersible bore pump - I'd need a decent inverter and battery set to start that and then there's all the associated depth of discharge and charging requirements to consider. The house only uses about 2 kWh during the day and 1 or 2 kWh at night.

 

There's an 18 kVA diesel genset to run the pump for fires (bigger than I need to start the pump but it was the right price) but to avoid glazing the bores I need to put a 6-10 kW load on it while the pump's running, hence the purchase of a heap of 500 watt halogen work lights before they went LED (imagine loading a genny with LEDs).

Edited July 13, 2016 by lencolad

[Guest]

There are alternative bore pumps that run when the sun is out. 

A small single phase pump (or even a dc water pump) would pump from a water tank at pressure to the home.

 

Let's see, that has eliminated the 3 phase, the enormous generator, 3 phase bore pump.

 

Your current solar systems would "ac couple" to mine (SMA Sunny Island 4.6Kva Inverter) and charge my battery fine.

 

You are closer than you think, to being self sufficient, especially if your consumption is as low as you say. 

[Guest]

Note, have seen portable generators get "snuffed out" in fire situations, electric will always work.

Edited July 13, 2016 by Guest

[lencolad]

Well instead of spending $10+k on a 100 metre deep hole and pump I could've spent that on a 150 kilolitre tank that could easily be filled by the roofs and then added a decent petrol pump for fire-fighting ...    And the bore water is acidic (pH 4.5) and iron-ey. Not much good for fruit and veg.

 

Diesel has a nasty habit of going green from algae and blocking filters too.

 

Still learning at 57.

Edited July 13, 2016 by lencolad

[Guest]

100m bore is easy for a small MPPT bore pump directly coupled to 3 x 250w  solar panels.

In my area (no reticulated water) we all need to install a fire fighting water tank (15 thousand liters I think) the other tank would be rain water.

Have set up a few systems like this, for remote area homes all on modest batteries and Inverter supply. The Generator is reserved for back up power only. Any water pump capable of more than 20 liters a minute will fight a small fire, otherwise roof top sprinklers (which is actually fairly normal in Tassie remote homes), set the electric pump to running and get the heck out of there   

[lencolad]

100m bore is easy for a small MPPT bore pump directly coupled to 3 x 250w  solar panels.

 

What sort of flow and pressure would that provide ?

[andyr]

Passive solar house build.

Step one – build a stud frame house on posts and bearers when young and dumb because it’s cheap and easy to build.

Step two – realise that it is hot in summer and cold in winter because it has little mass and is poorly insulated anyway.

Step three – get older and smarter.

 

Okay, so the trick is to achieve thermal stability (in a temperate climate that has nights that are significantly cooler than days in the summer) by having a lot of mass that is surrounded by a lot of insulation. Should take a long time to cool down in the winter and a long time to heat up in the summer if done correctly.

So how is it done ?

Winter – the sun is low in the sky and should penetrate the house’s interior to heat it, and there needs to be mass to absorb, retain and emit the heat at night.

Summer – the sun is nearly overhead and should not shine in to add heat.

Easy. Only it isn’t because there are some things called solar maximum and solar minimum and thermal maximum and thermal minimum to juggle.

What this means is that the shortest day of the year (June 21 ish) isn’t the coldest day – that comes six or eight weeks later. Similarly the summer solstice (December 21 ish) isn’t the hottest day in summer and that is about the eight or ten weeks later.

What this means in practice is that in March (eg at the equinox on March 21) it can still be very hot (where I live anyway at 33.5° south latitude) whereas on September 21st it may still be quite cool. On those days the sun rises and sets at the same places on the horizon (the azimuth) and rises to the same height in the sky at noon (the altitude). In other words it follows the same path across the sky on those days.

So if you gain a lot of solar heat in March that’s a bummer whereas you want to gain that heat in September / October. So there’s a bit of cunning planning to do.

To get the heat in the winter there needs to be glass facing north, and to avoid the heat in the summer there should be a decent amount of shading in the east and west. And shade is needed in the north later in the summer when the sun is lower and trying to shine into the house a bit more than it does in December / January.

Now the eggheads amongst us will ask ‘what is the ideal internal mass for a given internal volume to achieve thermally stability ?’. I dunno the answer to that despite some research so I made it up as I went along as you would if you’re a typical bloke.

 

I went to an auction and bought ($12k but probably $50k new) a heap of 2.6 m high double-glazed windows that were the display stock in a commercial glass-fitting outfit. They have aluminium frames with thermal breaks (ie. plastic segments in the frames to separate the inside and outside aluminium bits) and argon gas in the space between the two glass panes and also have low-E glass (google it).

Then I designed the house around these windows, putting them on the north side and NE and NW corners. The other windows (bought new) are the same but triple-glazed and cost $4.5k – could have paid two or three times as much without a bit of hunting around.

A significant feature is the external insulation on the exterior walls. These are rammed crushed limestone with 10 % white cement sheathed in aircell insulation. Stud frame (75 mm) steel is dynabolted to them and 75 mm earthwool batts (R 1.5) are added then 75 mm freezer panel (R 1.5) is glued onto the outside.

The roof is 200 mm freezer panel (R 4) on aircell on steel trusses. The ceiling is 13 mm plasterboard with 200 mm earthwool batts (R 4).

The slab is 100 mm concrete on heavy strip footings to support the weight of the external and internal walls. The exposed edge of the slab isn’t exposed – it’s covered by freezer panel cladding. I thought of insulating the slab but decided it was better as a heat sink in summer if uninsulated. I also thought of hydronic heating (water pipes) in the slab and/or walls but decided against it as I wanted to finish the house this century.

Some of the internal walls are rammed (300 mm instead of the usual 200 mm to add more delicious mass). Other walls are steel stud frames with plasterboard. The freezer panel came with a heap of polystyrene spacers so these were stuffed into the stud frames.

What is freezer / coolroom panel ? A sandwich of colorbond steel / polystyrene / colorbond that is used to build coolrooms. It has great spanning ability but I wanted a roof space above the ceiling for installing services so they sit on steel trusses, but because they weigh more than twice as much as colorbond then the trusses must be closer together. So more trusses are needed.

I realised later (not so smart …) that I could have just gone the conventional roof route and filled the whole roof space with batts and saved a heap of money, but I get a smooth underside to the verandahs that is easy to de-cobweb. This underside is thermally conductive into the roof space (summer bummer) and I thought of slotting it above the external walls but decided that was insane. Even for me.

 

The result is a one-bedroom one bathroom house with walls that are 450 mm thick.

To get experience with the freezer panel I used it in a mancave to live in whilst building the house. Steel shed frame with 75 mm walls and 100 mm roof that is pretty good thermally but I added an aircon in the second summer. Plenty of glass on the north side so very warm in winter.

Of course there’s solar hot water, solar electricity and a wood stove in each structure. A wood stove heats water, bakes, has a cooktop and provides space heating. The flat panel collector on the mancave is pretty good but the evacuated tubes on the house are superb in terms of efficiency.

Took five years from buying the land to moving in but I had to earn money as well as build. And plant a few trees as well.

Does it work ?  Yes.  Very warm in winter and cool in summer. On a 42° day it got to 28° but that was without shade sails or blockout curtains, so it will be better this summer and I ran cables for aircon just in case.

I did most of the work with the help of mates but obviously didn’t do the slab or rammed walls.

 

 

Very well done! 

 

 

Andy

[Guest]

What sort of flow and pressure would that provide ?

This type of pump runs when the sun is out, up to 20 liters a minute in full sun from a 100 meter bore.

It is used to fill a tank, not run pressure water into the house, those duties are performed via a "pressure pump"  from the tank

 

Bore pump control "Gee there is water pouring out of the tank overflow, better turn it off for a week or 2". If tank is close to the bore, a relay and float switch can be fitted.

Edited July 13, 2016 by Guest

[Two Flies]

[lencolad]

the horror, the horror -

 

[Guest Peter the Greek]

Very cool.....pardon the pun.

 

Any mechanical ventilation? or is it not that airtight?

 

We're wanting to build a passive house, undecided on the approach yet.....mainly because we've run out of money!

 

I love the "build it around the windows" thing......we had a quote of something like $70k for Windows and that was "cheap"....all manner of ideas running through my head after reading this. Thanks for posting/sharing!

[proftournesol]

The best type of ventilation is energy recovery ventilation. It uses a heat exchanger to maintain internal temperature and also controls internal humidity.

[lencolad]

Hi Peter. It's pretty well sealed (or will be when I silicon between the small window frames and the flashing) but there are three wall extractor fans for kitchen, bathroom and toilet which flow some air 24/7 because they're holes.

The chimney flue is vented in the outer skin so this would flow some air too.
I leave the window in the pantry cracked open to allow cool air to cool the fridge, and going outside and back in during the day gives some air exchange too.
The south door doesn't have foam seal stuff around it yet and there's about a 6 mm gap between the door and the frame.
I could leave more windows cracked open I guess but I'll learn more about that when I've been resident a while longer.

 

I've run the fire for a couple of hours some nights to cook on and to keep the temperature over 20° after eight pm but this puts too much heat into the HWS cylinder so then I fill the bath with hot water to dump some heat into the back of the house (which isn't closed off from the front). Now I've put a shadecloth blanket over the HWS tubes to avoid this again.  In summer most of the tubes can be covered and there'll still be plenty of hot water for one person.

Tonight I won't light the fire and the house should still be 18° in the morning.

 

edit - it's the next morning now and it's still 18° despite winds that could blow the crabs out of the mud. I can feel little draughts around the big windows due to some gaps that occurred because of some slight bending during transport.  Glass is heavy and double-glazed frames and elements are very heavy and moving them from the auction to a storage site and then to the building site was a bit of a saga.  I have a lot more respect for glaziers now.  

Edited July 14, 2016 by lencolad

[Soundscape]

Very cool.....pardon the pun.

Any mechanical ventilation? or is it not that airtight?

We're wanting to build a passive house, undecided on the approach yet.....mainly because we've run out of money!

I love the "build it around the windows" thing......we had a quote of something like $70k for Windows and that was "cheap"....all manner of ideas running through my head after reading this. Thanks for posting/sharing!

We paid ~$50k for a house full of double glazing around 8 years ago and that was cheap. So was the quality of the windows in the end. The other quotes you mentioned before (elsewhere?) re increased solar capacity etc sounded like your builder was taking the piss....

[lencolad]

We paid ~$50k for a house full of double glazing around 8 years ago 

 

Was that PVC or aluminium framed ?   Some of the PVC stuff seems rugged but some has thin wall thicknesses and dodgy-feeling plastic.  It all has AS 2208 stamped on it of course but all you need is a stamp ....

[Guest Peter the Greek]

We paid ~$50k for a house full of double glazing around 8 years ago and that was cheap. So was the quality of the windows in the end. The other quotes you mentioned before (elsewhere?) re increased solar capacity etc sounded like your builder was taking the piss....

 

No builder, we're driving this process and no its all about right...we've just got certain "needs"....high BAL rating being one of them for Windows

[Soundscape]

Was that PVC or aluminium framed ? Some of the PVC stuff seems rugged but some has thin wall thicknesses and dodgy-feeling plastic. It all has AS 2208 stamped on it of course but all you need is a stamp ....

Alu from Trend Windows. They look nice but that's almost the only positive aspect. Never again will I deal with them.

[Soundscape]

No builder, we're driving this process and no its all about right...we've just got certain "needs"....high BAL rating being one of them for Windows

Fair enough. If those windows will give the results you need then I would say that is good value. Of course most folks with average requirements would not spend that sort of coin. We are a privileged few who can take on this kind of project.

[Guest Peter the Greek]

 We are a privileged few who can take on this kind of project.

 

Doesn't need to be, I just think people need to decide on what is more important and what will make them happy/comfortable long term - check out http://superpodhome.com/

 

We're living in a 20ft shipping container at present (its a temporary thing)....its amazing what you dont really need when you're forced to......its not especially easy/comfortable with 2 adults, a 4 year old, and 2 large dogs, but we're questioning the "need" for a place as large as our last home (5 beds etc)