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cabinnewbie
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# Posted: 24 Aug 2022 08:42pm
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hi all,
i'm in the midst of my cabin build right now. Aiming to get the subfloor done this weekend and then start working on the walls.
I'm in mountainous area in VT. Completely off-grid, 12x16.
I'm planning to do a shed-style roof. But I'm confused about whether it makes more sense to have the higher wall facing north or south?
I figure if the high wall is facing north then the roof will be slanted down south and be better for solar panels.
But if the high wall is facing south then I can get a lot more sunshine in the winter but I assume it's worse for solar panels though?
I know the angle of the sun is more lower in the winter so maybe it's not so much of a problem then?
Am I understanding this correctly or wildly off on some basic principle...?
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toyota_mdt_tech
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# Posted: 24 Aug 2022 08:56pm
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Ideally, a 45 degree S to SW facing. How about a regular rafter roof with a ridge, shorter lumber spans, steeper roof angle for your panel.
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Steve961
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# Posted: 24 Aug 2022 08:56pm
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If the high wall is in the living room, which I assume it is, I would want to orient it towards the best view on the property. You can always put solar panels on a ground mount, and you can always heat the cabin with a wood stove for cheap, but a great view is priceless in my opinion.
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spencerin
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# Posted: 24 Aug 2022 09:48pm - Edited by: spencerin
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Quoting: Steve961 but a great view is priceless in my opinion.
Agreed, Steve961.
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ICC
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# Posted: 24 Aug 2022 10:18pm - Edited by: ICC
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Panels can go on the ground as long as there is space and sun exposure. The ground is my preference 100% unless space/sun dictates roof mounts.
Quoting: cabinnewbie if the high wall is facing south then I can get a lot more sunshine in the winter
More sunshine as in more light, a brighter room or do you mean sun heat gain? I like the idea of more light and possibly more to see. Heat gain can also be heat loss through windows. It is darker longer than it is sunny in VT which may mean that daytime heat gain may become night time heat loss.
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gcrank1
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# Posted: 24 Aug 2022 10:50pm
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Generally for a solar array in the n. hemisphere due 'solar south' (not magnetic; see info on 'declination') and an angle same as your latitude is accepted as the best all round performer. There are variations on that! Iirc +/- 15deg off from true S and/or the lat angle doesnt affect the solar harvest near what you might think.
But (there are always 'buts'), your use patterns throughout the seasons ARE important.
Will you use the place much, if at all, in the winter; ie, will it mostly be a '3-season place' or anytime? Will you even have winter access? If not you maximize the array placement to be best in the 3 seasons.
Some places are cloudy mornings or afternoons much of the year. Play that against your usage of the place and time of year AND the direction the array looks to maximize the best solar charging hours (typically only 4-5hrs/day).
There are online resources to help you with that.
You also need to do your 'energy audit' to balance your perceived wants against your true needs and what you can afford. If you want to switch on anything anytime like on the grid you Will PAY.
Online resources for that too.
And the 'diysolarforum.com' website.
Keep in mind that your own 'solar plant' isnt cheap! But depending upon the availability and cost of getting grid power on site it may be 'cheaper'. Imo, if you can get grid do it. You will have real power NOW. If/when you do solar you can start shifting to that until the grid is your 'backup' power rather than your main source.
Fwiw, our 16x24 recreational, 3-season cabin is totally off-grid. Our light-duty elec is LFP battery (have solar to recharge, down at the moment). For our heavy loads I run the 2000w inv/gen; it is brief runs. Im the power company. If we had grid I sure wouldnt be disconnecting it though I might minimize the use (but maybe not, we are not heavy elec users). Gotta make that monthly connect fee pay off, you know.
If it was my cabin 'home' Id for sure want to incorporate passive solar along with advanced building techniques for energy efficiency. Id like that for our recreational cabin too but for us concessions are made.
Yes, high summer sun, low winter sun. You want to keep the high, hot summer sun from producing solar gain inside and catch that low winter sun to hopefully heat some 'mass' inside to provide some core temp stability. Some high southern exposure structures utilize a shading front roof which could be the solar array? But I would want the most glass at my best view (in fact, Im putting in extra windows now just for that, and they face everywhere but south, lol).
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cabinnewbie
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# Posted: 25 Aug 2022 09:06pm
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Gotcha, I'm sold. I don't have great views but one side is definitely better than the other. And I suspect solar gain will matter a lot more than solar power.
Will be curious to see how high/low I should put the windows though.
I got the deck/subfloor up this week so hopefully will build my first wall next week!
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rockies
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# Posted: 25 Aug 2022 09:48pm
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I would angle the roof from the highest in the north to the lowest in the south so that your roof shades the main floor windows. So many people do the opposite and then they wind up with a double height wall of glass facing south that lets in a ton of heat and glare and turns their small space into a solar oven.
One of the most important considerations for designing the roof is how far out the south overhang will extend. Draw a section of your cabin and then draw in a line for both the highest and lowest sun angles for your location for the summer and winter solstices (June 21st and Dec 21st) which in Vermont are 69 and 22 degrees.
From the front edge of your south eave the 69 degree summer sun angle shouldn't enter into the cabin at all on June 21st. The winter sun angle of 22 degrees on Dec 21st should hit the entire window. Play around with the overhang length until you get the right balance.
A final note of caution - while a window may let in a lot of heat in the winter during the day the same window lets out a ton of heat at night so don't overdo the size or number of windows, even facing south. There's an old saying that says that the very best window makes a lousy wall, which means that every time you remove part of an R20 to R30 wall and replace it with an R2 to R 6 window you're creating an energy drain. In other words, have more warm walls than cold windows.
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cabinnewbie
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# Posted: 26 Aug 2022 08:24pm
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Quoting: rockies I would angle the roof from the highest in the north to the lowest in the south so that your roof shades the main floor windows. So many people do the opposite and then they wind up with a double height wall of glass facing south that lets in a ton of heat and glare and turns their small space into a solar oven.
Hmm, how about if I built an overhang on the south side roof to shade the windows for the summer angle? I"d be a little concerned about snow load on this overhang but maybe i could detach it for the winter.
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gcrank1
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# Posted: 27 Aug 2022 07:50pm
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I suggest you dont build something detachable. There will come a time that it doesnt get done and......
Build for the load even if it means putting posts out front to support it.
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Steve_S
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# Posted: 28 Aug 2022 09:00am
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As an Off Gridder in the Deep North (Algonquin Park, Ontario Canada) my recommendation is to go with an Adjustable Ground Mount. These can handle 4 to 6 panels without much issue and not hard to do. You never mentioned how much solar you want to install but given the little info provided you are not looking for anything huge.
An adjustable Mount will let you get the most out of your solar panels adjusted every season. Leave at least 3' from the bottom of the panels to grade for snow to .. it has to fall off somewhere.
When it comes to the Solar System, Keep It Sweet & Simple ! Currently many people are leaning towards the AIO's (All In One) units which combine Solar Charge Controller, Inverter, and Charger into one single box. These are all mostly High-Frequency devices and handle most things pretty well (not so good with inductive loads like motors such as AC, Well Pumps, and even Fridge/Freezer) due to the surge demand, therefore they have to be upsized to handle that.
Component-Based Solar which has a separate Solar Controller & Inverter/Charger is more suitable for a Part-Time Use home. When you leave the property, you can shut off the inverter & extra's while leaving the Solar Charge Controller to maintain the Batteries. Therefore the house is left without power (and the potential of something going wrong) while the batteries are maintained. Of course, with component-based systems, there are more bit's & pieces to put it all together and that is $$.
TBH, a Respectable "Low Frequency" All In One is the simplest and most economical way to go BUT one which can be expanded by adding another AIO if/when required. They are available in 120VAC or 240VAC Output. Up until recently, there used to be a big cost difference but that has changed somewhat and the 240VAC Models have become reasonable in price. There are MANY Brands and Grades of equipment and the cost all depends on the features, functions you "need" and would like to have.
Building from Scratch like you are, I would go with a Mid to High Tier AIO that outputs 240VAC providing you two legs of 120V as well (Standard in North America). This would allow for an Electric Stove and any other 240V device and even EV Charging if/when you get there at some point... You DO want to Future Proof for later ! The world is changing & faster than many realize. Also by using 240VAC you can just use a standard AC Electrical Panel that takes in 240 like your house does where you like.
Back of the Envelope Math to ponder...
A 3000W Inverter can output 120V/25A OR 240V/7.5A. A full Electric Stove (Conventional coil element type) requires 240V/50A (12,000W) BUT that is everything going at once. There are also new stoves which use Far Less energy and alternatives as well.
My Case as an example:
I use 120VAC only. My Deep Well Pump (280' down) is a 120V Softstart Grundfos Pump that uses 10A Max to push 52PSI to a 50 Gallon Pressure Tank. My cookstove is Propane as are my 2 On-Demand water heaters (1 is for Hot Water, the 2nd is in Radiant Heating as it is an isolated system). My System provides me with 120V/30A and that is enough to run everything I need. The Samlex Inverter/Charger can handle surges up to 12,000W (Low Frequency Unit - very $) so I have never had issues. My Inverter is Tier-1 (Top Quality) but there are good Mid Range models for far less pesos.
The most important thing to remember when going Solar Powered is that Conservation is far cheaper than Generation & Storage.
LOOK UP this info for your location.
Solar Panel Angle Calculator:
http://www.solarelectricityhandbook.com/solar-angle-calculator.html
Solar Irradiance Table: (Sun Hours per mo)
http://www.solarelectricityhandbook.com/solar-irradiance.html
Hope it helps, Good Luck
Steve
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cabinnewbie
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# Posted: 29 Aug 2022 04:24pm
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Quoting: Steve_S my recommendation is to go with an Adjustable Ground Mount.
Thanks Steve!
Yeah, I'm not expecting to use huge loads. Laptop, starlink, lights, maybe a water pump and fans. I'd guess at most 1000 watts solar panel capability and 2000 watt battery. Maybe I'd go fancy later on but not expecting to run any big appliances. Maybe will want a fridge one day.
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cabinnewbie
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# Posted: 29 Aug 2022 04:25pm
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Quoting: gcrank1 Build for the load even if it means putting posts out front to support it.
I'm guessing if I had a steep enough pitch and just need enough to shade the window then I could definitely attach a permanent overhang to the cabin.
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gcrank1
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# Posted: 29 Aug 2022 10:58pm
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As you are figuring 1Kw for array(s) you also need to factor in that seasonal usage. Overall (for example only) annually you might average 4 good solar hours per day, but thats an average....winter may be 2.5 with lots of overcast and summer 4.5-5ish and mostly sunny. Gotta figure how many watts you can generate in an av. week because some days, or even days upon days, can be poor producers.
My system is a grandfathered 12v and our use modest, not unlike what you state as current desires.
*Were I starting fresh Id go 24v IF I intended to stay modest usage* More than moderate use Id want 48v*
Ive heard that the better quality charge controls and inverters start at 24v, and even 48v is still considered 'low voltage'. 24v looks to be a good small scale in-between voltage to me.
Thing is that usage easily exceeds capacity! For instance, that water pump (if not a simple water transfer pump but a well pump) could be an elec hog, though an intermittent one, and a fridge would be a fairly steady one, though it cycles, but has start up surges that can really tax a system.
When you take your best guess at Watt Hours usage you should double it for perhaps long term/expansion purposes. If you dont you will likely find you estimated use too low and expected solar output too high.
Also keep in mind that conserving elec is waayyy cheaper than building more capacity.
So we run light duty on the battery bank, with or without the solar charging and the 2000w inv/gen for heavy short term loads. Works well for us.
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cabinnewbie
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# Posted: 31 Aug 2022 09:12pm
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Yeah I have a portable small 1000W gas generator that would definitely power anything I need.
I'm hoping in the long term that I can get grid electricity wired over but I think it'd cost at least a few grand to dig the trench from the neighbor and pay the electric company.
Without the pump or frig I expect my usual usage wouldn't be more than 100-200W, and I know in the winter that the panels get something like 5-20% of their summer peak according to my neighbors.
I've also been thinking i could probably get a used old RV type propane frig in the future if I ever really need a frig but right now it's mostly a luxury.
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