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06-30-16, 10:25 PM | #1 |
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Design and Build Spiv's Solar and Geothermal House
This thread is started with the intent to help Spiv design his solar and geothermal house in South Western Australia.
(This thread is re-directed from THIS_POST.) Here is some information that could be useful in this project: A Google map of the area where this house is to be built: LOCATION_MAP SITE_MAP (house is to be built on empty lot above arrow) DESIGN_DRAWING_A DESIGN_DRAWING_B CURRENT_HEATING_DEGREE_DAYS (for each of the last 365 days) Let's show Spiv what EcoRenovating is all about! Sincerely, -AC_Hacker
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I'm not an HVAC technician. In fact, I'm barely even a hacker... Last edited by AC_Hacker; 07-01-16 at 10:52 AM.. |
07-02-16, 07:28 AM | #2 | |
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Quote:
My interest is in a new home I will be building in 4~5 months, hopefully the last home I have to build:
I am exploring the ideas of:
Any help to get on the right track deeply appreciated!
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07-02-16, 09:46 AM | #3 | |
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Quote:
Do you expect to need any dehumidification?
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07-02-16, 05:36 PM | #4 | |
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Quote:
I remember reading a survey from Singapore Airlines on which was considered the city with the best climate in the world and Perth came first, pari with San Diego (where, I see, you live). We are at 32 degree South and the lot is on a small hill close to the Ocean, the microclimate here is different from even 2km further inland. The sea breeze and land breeze blow nearly every day mitigating the temperature. You can see here some statistics. Not sure how accurate they are, but the long term minimum average is 6.7° which seem correct. I lived here 36y and rarely suffered from high humidity. People used to have fireplaces or slow combustion stoves to warm the house in winter, but nowadays most use reverse cycle air conditioners, is that what you call a conventional heat pump? The reason I am researching this system is my desire to use less grid-supplied electricity. In the last 20y I built 6 two storey houses here, so I know how most things get done. However, I am not stubborn and can change my mind easily if I am shown a better way.
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07-03-16, 07:35 AM | #5 |
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Spiv,
It sounds to me like you have a fairly low heating load. In that case for choosing equipment I would go for a heat pump over geothermal. I would also forgo hydronic in floor heat, simply because you seem to be in a mild climate. If you are indeed in a mild climate, I encourage you to look closely at the Passivhaus concept. If I remember correctly you already have plans drawn up? If so I doubt you can really go whole hog on a passivhaus but it's concepts are hugely helpful in reducing your energy bills. The biggest concepts are air sealing with testing, and mechanical ventilation. All the other sexy stuff like tiny mechanical equipment, Earth tubes, HRV/ERVs, massive insulation levels, etc... only become effective when air sealing with testing and mechanical ventilation are taken care of first. What I would do: Insist your architect shows how the air sealing is to be done, especially around windows, doors, and any place the air barrier changes material, direction or planes. These drawings need to be included in the plans. Insist your contractor follows those drawings. Insist on having the house tested for air tightness with a blower door test (pressurizing and depressurizing the house). Typically this should be done three times during construction, once upon initial completion of the air barrier, again when all known holes through the air barrier are done (windows, doors, electrical, HVAC, water, etc...) and once again at completion. At completion a house done very well will have passivhaus levels of air tightness which is 0.6 Air Changes per Hour at 50 Pascals of pressure (ACH50), Well built houses will be about 1 ACH50. I would highly prefer all HVAC equipment to be inside of the air barrier (conditioned envelope really). Insist that a Manual J calculation be performed by a competent engineer. I would also insist that the HVAC equipment be tested with a duct blaster (unless you go with ductless minisplits). I would also insist that the system be commissioned so that the air flows from the registers match what is called for on the manual J calculations. |
The Following User Says Thank You to DEnd For This Useful Post: | jeff5may (07-03-16) |
07-03-16, 09:52 AM | #6 |
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Thank you DEnd,
I will look into Passivhaus. Still, we do need to heat our houses for 3~4 months and I cannot think of a nicer feeling than to walk barefoot on warm floors..... Natural gas is very cheap in WA, perhaps hydronics and gas heating is the cheapest answer.
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07-03-16, 07:03 PM | #7 | |
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Quote:
The least cost option is likely using a point source of heat/cooling. This becomes possible with high insulation levels, and high levels of air sealing. Point source options (like ductless mini-split heads) can however have distribution issues. There is a Net Zero builder up in Maine that uses a single ductless mini-split head on each floor of his houses. (http://transformations-inc.com/press...ards-Issue.pdf) One issue is that to keep interior temperatures consistent across rooms doors need to remain open. Another issue with a point source is that you don't tend to have very good air mixing, which can lead to pollutant build up in one area. Energy use wise a heat pump has to get a Coefficient Of Performance above 3 to use less energy than natural gas. Even mini-splits typically only get this COP in mild temperatures. Of course if you get a really tight house insulated well then you may not even be able to find a Furnace with a low enough output. Also quite a large percent of a mini-splits energy can easily be offset with photovoltaic panels. With on site production and storage a mini-split only needs to get its COP slightly below 1 to use less energy than natural gas. Grid Tied PV offsetting mini-split energy useage raises the needed COP to about 1.5 - 2 or so. If you take a look at environmental sustainability a heat pump wins in most cases. A furnace will never see CO2 and other emissions reductions, a heat pump, for most parts of the world, will always see a reduction in its emissions over its lifetime. This is because the electric grid is being pushed by market forces to be more efficient. Also you can easily add emissions reductions by adding PV to the system. |
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07-03-16, 11:18 AM | #8 |
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Don't forget to check the service charge for natural gas. In some cases, it can be significant enough to more than offset any savings. The latest (conventional) heat pumps are getting so efficient that they're competitive with natural gas in many areas.
How much does it cost to install the ground loop (just the loop itself, no equipment) from the start? It's probably worth installing just in case you decide to get geothermal later on.
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07-03-16, 02:22 PM | #9 | |
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This is from one of our providers: Standard Gas PricesDon;t ask me what a "Unit" is as I could not figure it out , however, Here is a cost comparison. When you guys on this forum refer to "Conventional Heat Pumps" what do you refer to? Something like this?
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07-08-16, 10:32 PM | #10 |
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Had to look up what a WA AUS unit was for gas, elec unit is the kw-hr.
Gas unit is 3.6 megajoules = 1 kw-hr (0.034 therms) 1$ US = 1.3 $ AUS 3.6 megajoule number comes from, .278*3.6 MJ = 1kw-hr Rates are gargantuan compared to USA WA state: About 3X higher! Elec power runs about 30 cents kw-hr including supply charge (AUS$) < 10 cents in WA state USA Gas is $3.50 a therm ($1.50 or less in USA depending on area) SPIV: IT IS TIME FOR GSHP! with your high rates. Really surprised you nat gas rates are so high - of course, prior to fracking, many USA gas prices were over $2 a therm (7 cents a 'unit') My DIY GSHP (60,000 BTU, 5 ton) cost under $600 and has a COP of 5.7 with 52 deg ground temp below water table. With the WA high rates, solar is a definite option to consider! Last edited by mejunkhound; 07-09-16 at 04:23 AM.. |
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