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The elusive 10 stars

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Started 8 years ago by dlvb19
Latest reply from StephenF

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dlvb19
Member

Having just built a house I am forming an idea of what my annual heating/cooling related electricity consumption might be. Liberally I'm looking at around 1500 kWh annually which will be overwhelmingly heating as I'm based outside Ballarat. The house is ~133m^2 with R5 ceiling,R9 walls and R2.5 floors and all heat is supplied via a heat pump with approx COP=3.

The home was rated at 6 stars using the NATHERS scheme however I have added some extras that weren't on the original plans. Using the NATHERS starband chart (http://www.nathers.gov.au/about/pubs/starbands.20121129.pdf) my consumption would put me at about 7 stars.

My question is, is it actually possible to achieve a 10 star build that ACTUALLY requires the heat energy NATHERS suggests.
For Ballarat a 10 star home uses 2MJ/m^2 which is 2/3.6 = 0.55kWh/m^2 which is 74kWh (for 133m^2) of heat/cool energy per annum. Assuming a similar heat pump thats 25kWh of heat/cool electricity per annum!! Really?

I understand that further north its not that hard to achieve a zero thermal input home due to a friendlier climate, but how do you achieve that kind of efficiency in colder climates? I have some pretty bad ass insulation, vast majority of glazing faces true north, windows are low U with moderate SHGC and have appropriate amount of thermal mass. If you do some basic heat diffusion calcs a conservative heat loss (during winter) is 1.0kW or 24kWh a day which will require at least 7kWh of electricity. And this assumes zero air loss.

Anybody have some success stories? Low energy consumptions in a cold climate?

Thanks

Posted Friday 31 May 2013 @ 5:38:05 am from IP #
TonyT
Member

Expanded polystyrene 300mm thick has R value 7.9 m2K/W

Hence U is 1/R is 0.13W/sqm per degC

Constructing floor, ceiling and walls from 300mm SIP panels and keeping double-glazed windows to a minimum area may achieve 10 stars.
http://wa.australinsulation.com.au/_data/docs/ai%20eps%20econotilt.pdf

If necessary use insulation thicker than 300mm !

Posted Friday 31 May 2013 @ 6:19:58 am from IP #
dlvb19
Member

Thanks Tony T.

Appreciate that your words are usually accompanied with numbers.

Even with walls ceiling and floor having R=8 and windows having R=1.5 (U=0.7, the best on WERS website) you are still looking a diffusive losses of 500W. This will still require 4kWh of dancing electrons every winters day. At this rate you will blow past your annual 10 star budget in 7 days!

Posted Friday 31 May 2013 @ 7:24:04 am from IP #
Kipper
Member

Theres a man (John Morgan) just out of Ballarat who has built a 9 star house (google "9 Star House Lexton" and you will find the articles)

The problem with your calculations is that your only calculating the raw losses, not the gains from the windows. I believe 10 stars should be doable. You have just said in your own post that your using about 4kwh a day for heating, not the 7 you calculated as losses for your house

You say you have the appropriate amount of thermal mass, but for a very high star rating you will probably need an "excessive" amount of thermal mass. You will probably also need insulated window coverings that are open during the day and closed at night when the sun is not out.

You may want the check out other cold climate houses for inspiration, such as the alaska passive houses or the earthship homes in the New Mexico desert

Posted Friday 31 May 2013 @ 9:22:55 pm from IP #
dlvb19
Member

The new mexico house is of little interest as they have a high diurnal range with lots of sun (being an arid area) which is the best location for thermal mass. I'm not sure about alaska's weather except I have an idea its very very cold, so will check this out.

I had calculated theoretical gains using: Insolation x angle coefficient x SHGC x area, and they are quite high and should make up for most of the heat loss as you suggested. On an overcast day however the solar gain is nowhere near the calculated level. I presume this is due to the light rays being highly scattered and less of them hitting the windows at the low angles desired.
So what do you do when you have multiple overcast days in a row (the norm in winter here). Thermal mass will only help you for so long. We have an appropriate amount of thermal mass for our glazing area. If you add an excessive amount of thermal mass it will work against you.

Thermal window covering a brilliant idea! Have been working on a concept with insulation rolls sown within fabric. Much cheaper and more effective than curtains.

Cheers Kipper

Posted Saturday 1 Jun 2013 @ 12:07:58 am from IP #
Eco
Member

It should be possible (and PassivHaus suggest that it is). It would require large thermal mass and insulation and minimal non north facing windows. However another question to ask is - is it worth it. Thermal mass (usually) costs a lot and its benefits would only be required on a few days of the years.

Peter Reefman, who sometimes participated on this site, adopted the approach of building to 8 Stars and then installing a PV system which would generate sufficient energy to more than make up for the small amount of heating / cooling energy required. Effectively a zero energy house. This approach seem reasonable to me (though could buy in green power rather than roof top PV as an option).

Also the energy calculation in star band system make various conservative assumptions about the way the house will be used. It should be possible to beat the starbands energy consumption with some simple life style adjustments, such as not heating the whole house and the use of insulated window curtains overnight in winter and perhaps accepting a wider temperature comfort band.

Posted Saturday 1 Jun 2013 @ 1:32:09 am from IP #
Kipper
Member

dlvb19 said:
I had calculated theoretical gains using: Insolation x angle coefficient x SHGC x area, and they are quite high and should make up for most of the heat loss as you suggested. On an overcast day however the solar gain is nowhere near the calculated level. I presume this is due to the light rays being highly scattered and less of them hitting the windows at the low angles desired.
So what do you do when you have multiple overcast days in a row (the norm in winter here). Thermal mass will only help you for so long. We have an appropriate amount of thermal mass for our glazing area. If you add an excessive amount of thermal mass it will work against you.

Thermal window covering a brilliant idea! Have been working on a concept with insulation rolls sown within fabric. Much cheaper and more effective than curtains.

Cheers Kipper

The alaska house I thought was passive is actually net zero (i went and re-googled it afterwards). He has a 20,000 liter water tank in his house for thermal mass which can keep the house warm for something like 5 days of cloud cover (I didnt re-watch the whole 2 hour video...) The water is heated by conventional solar hot water system. (though bigger of course)

The shutters in the alaska house are made of wood and foam and are external.

Posted Saturday 1 Jun 2013 @ 2:54:54 am from IP #
Eco
Member

dlvb19 said:
The house is ~133m^2 with R5 ceiling,R9 walls and R2.5 floors and all heat is supplied via a heat pump with approx COP=3.

The home was rated at 6 stars using the NATHERS scheme

My house which is about to be built was rated at 7.2 Stars and it will have R6 bulk insulation in the ceiling (along with RFL), approx. R3 walls (Hebel) and R3.5 under the suspended slab section of the house. The windows are double glazed with low e coating. Northern windows have eaves for shading in summer. To get a higher rating I could have cut down the size of the non north facing windows. (I cut the window size a bit from what the designer - who did not have any particular energy efficient house design credentials - said. I should have gone further.)

Your house seems to have more insulation than mine yet achieved a lower rating - perhaps it is to do with the location - Melbourne compared Ballarat (a colder climate). Do you have large windows or single glazed windows?

Posted Saturday 1 Jun 2013 @ 3:27:41 am from IP #
Kipper
Member

Eco said:
Peter Reefman, who sometimes participated on this site, adopted the approach of building to 8 Stars and then installing a PV system which would generate sufficient energy to more than make up for the small amount of heating / cooling energy required. Effectively a zero energy house. This approach seem reasonable to me (though could buy in green power rather than roof top PV as an option).

Yes, I think a net 0 house would be a lot cheaper and more practical these days with the price of PV's dropping significantly in the last 20 years.

If I build I plan to shoot for net zero but still build to a pretty decent (7-9) star rating in the first instance.

I am very used to living out of one room (ie, living in my bedroom) so if I built a house I would insulate the internal walls around this room as well, which would not improve my star rating at all, but would possibly significantly lower my heating bill.

I would also insulate the walls around the toilet and bathroom as these rooms are typically ventilated.

Posted Saturday 1 Jun 2013 @ 8:31:40 am from IP #
dlvb19
Member

Eco:

Our thermal mass is earthen render so was incidental, requiring no extra time/effort.
I agree with Peter's approach however I see PV as cheating in this regard, however lots of PV is always a good idea.
I'm interested at what conservative assumptions are made?
You have higher insulation in the ceiling where a proportionately higher amount of heat escapes compared to the floors/walls (35-35% vs 10-20%). This may be the difference.
The starband is normalised for climate .eg Ballarat homes get larger energy budget to achieve same star rating as Melbourne as the former is much colder.
All windows are low E DG with bare minimum number to south (10% of floorspace), none on east or west and 16m^2 glazing to 75m^2 living space to north (21% floorspace).

Kipper:

Can you post link to Alaska house. I found a review piece on it but hoping there is more info.

Posted Saturday 1 Jun 2013 @ 10:55:33 am from IP #
arttt
Member

I thought PV was cheating but have come around to the idea that if its cost neutral to use the Kwh and replace them with PV generation versus make the efficiency gains then there is nothing wrong with that.

Posted Saturday 1 Jun 2013 @ 11:28:54 am from IP #
TonyT
Member

dlvb19

More digits

For an enclosed space with floor 10 x 10m and height 2.7m,
the area for heat loss is ceiling 10x10 + floor 10x10 + walls 10x2.7x4 is 308sqm.

If R is 8.0 then U is 1/8 is 0.125W/sqm per degC.

For outside average temperature 7degC and inside 20degC deltaT is 13degC

Hence heat loss through walls, ceiling and floor is 308x0.125x13 is 500W as you have said.

For an area of window of 15sqm losing heat at U is 0.7W/sqm per degC (best insulated) the heat loss is 137W.

Total 637W for 24hrs is 1.5kWh/day.

Agreed: this is well below 10 star performance so thicker insulation would be needed !

It seems reasonable that the highest rating (10 stars) is not likely to be achieved without extreme (impractical) measures.

Doubling the insulation thickness would reduce the 500W heat loss by almost half.

The window would need good curtains when it is dark and colder outside.

In Adelaide the energy incoming from the sun (insolation) onto a vertical plane that faces due North is an annual maximum in July of 14.1MegJoules per square metre per day (=3.9kWh/sqm per day).

Of this, glass tables (e.g. for Viridian) show that the glass transmits about 70% into the room:
0.7 x 3.9 equals 2.7kWh/sqm

To offset the daily heat loss of 1.5kWh/day the required area of North facing glass would be 1.5/2.7 is 0.6sqm.

In summer, the minimum solar insolation onto a vertical North facing wall is in December at 9.1MJ/sqm per day (=2.5kWh/sqm/day).

In July solar insolation rises from zero at sunrise and in the middle of the day the maximum insolation is 590 watts/sqm.

Posted Saturday 1 Jun 2013 @ 8:44:16 pm from IP #
Kipper
Member

dlvb19 said:
Kipper:

Can you post link to Alaska house. I found a review piece on it but hoping there is more info.

Certainly:

http://www.youtube.com/watch?v=Xen_VWyDezY
http://www.youtube.com/watch?v=AtHkvpRI6fc

Thats 4 hours of video, should keep you entertained for a bit

Posted Saturday 1 Jun 2013 @ 9:15:16 pm from IP #
Kipper
Member

arttt said:
I thought PV was cheating but have come around to the idea that if its cost neutral to use the Kwh and replace them with PV generation versus make the efficiency gains then there is nothing wrong with that.

I agree, so long as your replacing them in the same month.

ie, if your making up KW for heating, then you have enough PV to generate that power during winter with the higher percentage of cloud cover. I might average 4 peak sun hours per day for the year, but in winter I think its only around 2-2.5 or something, so if I need 5kwh per day of heating in winter then I need 2.5kw solar system to cover it.

If your making up KW for cooling then it will be much easier of course....

Posted Saturday 1 Jun 2013 @ 9:21:54 pm from IP #
gazmo88
Member

Hmmm,

Well this project claims to be 10 star:

http://joshshouse.com.au

nothingtodowithmewhatsoever

Posted Sunday 2 Jun 2013 @ 5:17:30 am from IP #
Kipper
Member

gazmo88 said:
Well this project claims to be 10 star:

http://joshshouse.com.au

Warmer Climate

Posted Sunday 2 Jun 2013 @ 6:44:23 am from IP #
arttt
Member

Kipper said:
I agree, so long as your replacing them in the same month.

just wondering why the same month proviso? My thinking is to aim for net zero CO2 on an annual average basis. happy to have that thinking challenged though.

Posted Sunday 2 Jun 2013 @ 10:06:36 am from IP #
arttt
Member

gazmo88 said:
Hmmm,

Well this project claims to be 10 star:

http://joshshouse.com.au

nothingtodowithmewhatsoever

That makes it look easy (but is well designed and im sure involved a lot of careful planning) to get ten stars and had me scratching my head for a while to find the secret.

the secret......
.... is to live in a very agreeable climate zone.
http://apps.nowwhere.com.au/DCCEE/climatezonemaps/content/zoneinfo/52.pdf

Posted Sunday 2 Jun 2013 @ 10:29:28 am from IP #
Kipper
Member

arttt said:
just wondering why the same month proviso? My thinking is to aim for net zero CO2 on an annual average basis. happy to have that thinking challenged though.

Because that way if:
- Batteries become significantly cheaper
or
- Electricity becomes significantly more expensive
and
-Feed in tariffs are abolished

Your house can do what it sounds like it can do when you say its net zero, sustain itself year round (with the addition of some batteries).

Posted Sunday 2 Jun 2013 @ 7:47:45 pm from IP #
tom
Member

I think it's possible. Our house is being built right now. 253m2 including 41m2 garage. R6.5 walls, R13 ceiling, low-e argon filled DG everywhere, R2.5 internal walls. Timber floors over concrete. Rated 8.3 stars in Melbourne. Raw concrete would have got us 8.5 stars. House is long and narrow ~ 28m x 9.5m. Decent sized windows facing east and west - 2.5m x 1.5m for bedrooms, 3.2m x 1.5m for lounge, 2.2m x 2.4m X2 for living. Only two north facing windows - 3.7m x 2.5m and 2.8m x 1.3m. House currently missing window seals (and coverings) and no front or internal doors. I've had two separate trades tell me the rear room that faces north is cosy warm on a 12 degree day with the sliding door open. These guys aren't even aware of the insulation so I don't think they're trying to make me feel good. This is our big open plan area of kitchen/meals/family. Problem is you leave this room and you can feel a drop of 4-5 degrees. Given this performance in an unsealed house with poor orientation, I wonder what it would be like if the house was rotated 90 degrees with the 28m facing north rather than 9.5m, had curtains, doors, window seals and a concrete floor. I think it could easily make 10 stars.

I agree with the zero net energy approach too. We have 6KW of panels on the roof, and expect to be supplying power to the grid averaged over the entire year. Other than the feel good factor of "I have a 10 star house", it's probably better to aim for zero net energy. Cheaper and more practical. The 10 star house still needs light, cooking and entertainment, so without solar panels can't be zero net.

Posted Sunday 2 Jun 2013 @ 10:15:24 pm from IP #
TonyT
Member

The energy star rating is only a scale.

The target star number depends upon the goal, the costs and the benefits.

A sensible target is likely to be less than ten stars.

As well as depending on the heat losses, the star rating depends upon the captured heat gains.

If a building is well-designed, significant kWh of solar heat can be captured through North facing glass that is un-shaded during winter.

When the sun is shining, its heat can be captured and stored in thermal mass.
The stored heat is then released into the room as the room cools.

In Adelaide the energy incoming from the sun (insolation) onto a vertical plane that faces due North is at an annual maximum in July of 14.1MegJoules per square metre per day (3.9kWh/sqm per day).

Of this, glass tables (e.g. for Viridian) show that typical types of glass transmit about 70% into the room:
0.7 x 3.9 equals 2.7kWh/sqm per day

To offset the daily heat loss of say 1.5kWh/day from a highly insulated building,
http://www.ata.org.au/forums/topic/9259#post-43596
the required area of North facing glass would be 1.5/2.7 is only 0.6sqm of glass.

Solar energy can also be captured as electricity using solar PV panels.
Electricity can be stored in batteries or in the electricity grid.

In winter (June) in the Adelaide Hills a 1.5kW solar PV system typically generates electricity at 3kWh/day from 8 panels facing North, tilted at 25deg and covering 10sqm.

Even under total cloud in winter, this 1.5kW system generates at least 1.5kWh of electricity per day.

Posted Sunday 2 Jun 2013 @ 11:49:38 pm from IP #
StephenF
Member

Dlvb19 and others, where you have quoted high R value walls, what method of construction have you used? I have been looking at SIPs and ICF and something similar from GreenEnergyBricks but I can't pick between overall simplicity, effectiveness and cost.

Where you have very high R value roofs, is that just a regular pitched roof with a truck load of insulation, SIPs, or something else again?

Appreciate your ideas, feedback and experience.

Posted Sunday 14 Jul 2013 @ 5:06:38 am from IP #
dlvb19
Member

Straw Bale walls: R value = 6 - 9 (depending on source)
Cellulose in ceiling: R value = 5 (about 20cm thick)

Please try and avoid concrete and foam insulation!!!

Posted Sunday 14 Jul 2013 @ 6:52:14 am from IP #
tom
Member

Hi Stephen,

Our walls are R4 80mm phenolic foam panels plus R2.5 batts between a standard 90mm stud wall. Ceiling is two layers of R6 batts plus R1.5 blanket sarking. Don't ignore the ease of building standard stud walls over SIPs and ICFs. I think it's irrelevant if these products are the "right" or "best" way of building. The fact remains no builders want to touch them unless forced, and you will pay extra because of it. And if you have issues down the track what are you going to do? Most of these companies will be dead by then, and no-one will know how to make repairs or modifications (e.g. add a power point in 10 years time).

Posted Sunday 14 Jul 2013 @ 9:41:58 pm from IP #
StephenF
Member

Thanks Tom and dlvb19, straw bales is probably a bit too much to ask of my local council, though as part of the Manningham 'green wedge' area maybe they wouldn't think it too out there. As my brother-in-law carpenter is the builder he may think I have gone a little too far!

Tom, what kind of external finish did you use and what roughly do you think the per square metre costs ended up being? I am only thinking of the external walls at the moment, so my brother-in-law should be happy playing with the regular stud walls internally. He says he has worked on a hebel construction home as a subbie in the past but no real experience with other materials, though he is quite happy to give it a go, I think he likes the novelty of a new experience, not the attitude of most builders, I know.

Posted Monday 15 Jul 2013 @ 12:02:32 am from IP #
tezz
Member

StephenF, sent you a PM

Posted Monday 15 Jul 2013 @ 12:54:44 am from IP #
baksteen
Member

"Please try and avoid concrete and foam insulation!!! :)"
Why is that?

" no-one will know how to make repairs or modifications (e.g. add a power point in 10 years time)."
You can melt/cut channels in the foam, so not hard at all.

Posted Monday 15 Jul 2013 @ 10:50:08 am from IP #
dlvb19
Member

Baksteen,

Unsustainable!! The precursors for nearly all foams are fossil fuels. They have a very high embodied energy. Before you start talking about "operational energy saving" justifying the huge carbon capital, remember that strawbale and cellulose insulated light timber construction can achieve the same R values with a massively lower or even negative c02 footprint. And they are almost 100% sustainable.
Also the embodied energy of concrete is very high and all of it is dug up from the ground. Theres that U word again.

Sorry if this came across as preach, just being succinct.

Posted Monday 15 Jul 2013 @ 1:12:48 pm from IP #
tezz
Member

The search for sustainable is not always easy. Just had to dig this out tonight, for another purpose.
The following is part of the Covenant on the land. ( my land )

" 1 The external walls of any dwelling erected on the land shall not be constructed of any materials other than brick, brick veneer, stone, concrete, masonry, timber or Hardie's Fibre Cement products. "

So, one sentence wipes out Rammed Earth, Strawbales, Mud Bricks, Colorbond, Aluminium, PVC and " theoretically " restricts one to the JH FC product.
Not sure how the ACCC would view that.

As an honestly ignorant query, what is the eco comparison then between EPS, PIR, Phenolic, PUR etc and Rockwool ?

Posted Monday 15 Jul 2013 @ 1:30:02 pm from IP #
tom
Member

Not sure how many people would leave their foam panels unfinished on the inside, even if they did, you're suggesting to add a new power point I can just melt a track for some new cable all the way to the meter box or nearest junction box. And then what? Putty over it (or use expanding foam), sand it back and paint just the bit that was melted? So what should be a $100 work for a sparky now requires at least 2 trades, some nice smells of melting foam and how much cost? Or if you choose to cut them instead, you still have to cover the cuts with putty, sand and paint. (2 coats probably). Not sure I'd call this easy. If you chose to cover the inside with plaster, now you to have cut through plaster as well.

Posted Monday 15 Jul 2013 @ 9:44:13 pm from IP #

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