diy solar

diy solar

Complete rebuild of a house - how would you power and heat/cool ?

Prefersdirt

Solar Enthusiast
Joined
Sep 28, 2019
Messages
372
I don’t know if this will be fun for you or not. I have a love/hate view of these challenges. Especially since I will be paying for this one!


I am moving to a new house that first must be renovated. Completely renovated. House is well over 100 years old (original part is over 140 years old). House is solid so renovating and updating insulation, etc should hopefully be smooth. Here is my request for the gurus here: How would you power, heat, and cool a house so you can be off-grid and very comfortable? While money is an issue, figuring out a plan has to start somewhere.

Here is some more information: Location is Indiana, so get nice and cold plus nice and hot, with high humidity. 1500 sq feet primary floor. Attic will be finished and used as a second floor. House has a basement. Wells for water (I don’t know current pump requirements) exist.

Power system needs to be able to expand as demands increase. This will be a working farm, and power requirements will increase as a walk-in cooler and freezer are installed in the future. (Currently we have 2 chest freezers) Goal is to use electric golf carts for chores to charge off solar.

Plenty of land for solar. Easy to put panels on a barn that unfortunately has the roof facing East/West but is open to full sun. Ground mounts are an option.

Please don’t tell me to do an energy assessment as figure this is a completely empty building. So hard to do an assessment when nothing exists.

My initial thoughts are to go to radiant solar floor heat. Mini-split units for A/C and backup heat. Or do I figure out geothermal? Ductwork requirements would make this more difficult. Specific units and designs are not yet there.

Grid exists there now. Start with grid and then build solar?

Final glitch - everything must be able to pass inspection for the refinance.

Hope this is ok. Thanks
 
You first have to know the total amount of power you're going to need, at least a good ballpark figure; else, you're spinning your wheels. Here's a suggestion. Do you have neighbors nearby? If so, ask what their monthly kWh usage is, average the results, and that will get something to work with. Remember, the more comfortable, the more expensive. The first question I or anyone will ask you is how many kWh do you require? Follow?
 
Since you can't start with a power assement, can you compare to the current house to get a baseline?

Otherwise, if the barn roof is good and the angle appropriate, I'd load up the roof with a good amount of panels. Maybe 20 east and 20 west.
Put most of those on to solar charge controllers. I'd throw a few (4-5 on each side [edit: more or less depending on your expected base loads]) onto micro inverters, as they can more efficiently power your constant day time loads directly.

If you have excess space (not something I've got, so I'd put them on the barn) a ground mount will be easier to install and maintain if/when needed.

Get a good 48v DC inverter. Definitely something you can parallel as/if you add more.

Also, a transfer switch (automatic?) to go back to grid power when the inverter needs some lovin.

If you can do geothermal for the heat pump that will be more efficient year round. Also the heat pump "should" be more efficient at heating than in floor radiant.
 
As I have thought about a “cool” future house - I would use a heat pump (ground- geothermal) for the main heating and cooling. Because I like backups, I would think about getting a propane tank - backup heat, fuel for backup generator and winter cooking and laundry dryer.

In an “ideal” kitchen , I would have two stoves - an electric induction and also a gas stove. That way for the big family gathering you have both. If there is plenty of sun - use the induction- if not - use the gas.
 
Grid is available. Batteries cost more per kWh than buying power from grid. Therefore, use grid-tie inverters that support "frequency-watts" so they can later play nice with a battery inverter. Or, use a hybrid that can get by with little or now battery for now.

I like SMA, but it is one of the most expensive, unless you get old-stock inventory liquidation.
Determine what features are required for grid-tie. New code may require features to support grid stability, such that old units aren't approved.

SolArk is a hybrid that might work. And there are cheaper brands.

Motors have starting surge, which battery inverter or hybrid must support when running off-grid. (grid tie inverters don't have to because grid takes care of that.) Surge requirement will dictate which inverters are needed.

Split phase or 3-phase?

East-West isn't bad in the summer, in fact near optimum.
What is your anticipated summer vs. winter consumption?

You can do an energy assessment of refrigeration, water, farm equipment power needs.
Given a building drawing, HVAC estimates can be made. I think that's part of "Title 21" energy efficiency for California.

Geothermal? Meaning you have heat available in the ground?
Or did you just mean ground-source heat pump?

I wouldn't want to have to depend on the sun for heating in the winter.
If net metering exists, then you can bank PV generated power in the summer and consume the credits in the winter.
 
I would figure out how to insulate it as much as possible to include new efficent windows and then get a full manual J calculation done to figure out how much you need to heat/cool.

I wouldn't even go down the solar route until you have everything else figured out as you have a grid connection already and can see how much power you would need to be fully off-grid after you get all the updates done to the house.
 
If grid tied capable, I would stay on the grid.

I would heat with gas. Locally, whatever is available cheaper whether heating oil, diesel, etc. For me, that is gas piped in by the gas company. Locally those that heat electrically have a $500 a month heating bill in the winter. With gas,mine is 1/10th that.

For cooling, I’d consider a mini split for each room, but would probably still go with central air with one or two 5 ton units.

Only after I’m sure I am staying where I’m at would I consider solar panels for the roof. Six years in my current house and I think we will be here for a while. So this may be when I add the panels.
 
Honestly if you can heat it with a pellet stove I would go there ...only because I have done it since 2014 when we had this house built ....we have a 1500 sq foot house in the mountains of west PA ...I have an undersized Harmon P43 rated for 2200 sq feet and runs at less then 340 watts. I have a whole house heat pump for AC and Heat installed by the builder but I do not use the heat function ...I have an intake from the air handler plumbed into the pellet stove air input and the output is plumbed back into the the intake below the air filter. So the only thing that I run on the air handler is the fan which distributes the heat thru out the house. The vents are attached to the pellet stove with magnets so no modification has been made to the stove. I usually use 4 and 1/2 ton of pellets per year and get good results down to -16 degrees F. Both my basement and house are very comfortable... At the time they didn't have stoves made for this but now they do and you can go hot air or pellet boiler. My backup solar system can run this and a freezer with no problems in a complete power outage .

As far as Solar ....my best advice would be to put in as many panels as you can afford .....I have 4 panels at 1200 W and on sunny days I can get more then 100 percent of what the panels are rated for but a lot of days up here are cloudy and you dont get crap maybe 10 percent .....and ground mount them so you can remove the snow

Also east west up here for solar sucks, from experience you have to have a clear south facing and you have to be able to sdjust your panel angle down to 26 degrees in the winter and back up to at least 44 degrees in the summer
 
Honestly if you can heat it with a pellet stove I would go there ...only because I have done it since 2014 when we had this house built ....we have a 1500 sq foot house in the mountains of west PA ...I have an undersized Harmon P43 rated for 2200 sq feet and runs at less then 340 watts. I have a whole house heat pump for AC and Heat installed by the builder but I do not use the heat function ...I have an intake from the air handler plumbed into the pellet stove air input and the output is plumbed back into the the intake below the air filter. So the only thing that I run on the air handler is the fan which distributes the heat thru out the house. The vents are attached to the pellet stove with magnets so no modification has been made to the stove. I usually use 4 and 1/2 ton of pellets per year and get good results down to -16 degrees F. Both my basement and house are very comfortable... At the time they didn't have stoves made for this but now they do and you can go hot air or pellet boiler. My backup solar system can run this and a freezer with no problems in a complete power outage .

As far as Solar ....my best advice would be to put in as many panels as you can afford .....I have 4 panels at 1200 W and on sunny days I can get more then 100 percent of what the panels are rated for but a lot of days up here are cloudy and you dont get crap maybe 10 percent .....and ground mount them so you can remove the snow

Also east west up here for solar sucks, from experience you have to have a clear south facing and you have to be able to sdjust your panel angle down to 26 degrees in the winter and back up to at least 44 degrees in the summer

Why pellets vs firewood? I can get firewood with the equity of my sweat and some chainsaw / splitter work. Pellets requires me depend on someone else being able to take my money to give me something.

I plan on overpanneling like crazy. the challenge is to guess how much is too much or not enough. The long-term goal is to be able to recharge the batteries in a limited amount of sun exposure time. My brain is numb from purchasing documents on the new place, but I think we have a planning period of 2 hours for here in the winter. Might be too fast of a charge. I will have to look again (zip is 46123)
 
all depends on how much you want to work and how much dirt and bugs you want to drag into the house. If your young firewood is no problem, I just don't have that much ambition. The pellet stove is automatic ....turns itself on and off and keeps the temperature constant. You have to constantly feed a wood stove and you will have constant heat variation from being to hot to waking up in the morning with little to no heat and having to get the fire stoked again first thing.
As for charge time it really depends on the type of batteries you use and the charge controller. From my experience My MPPT charger is the best and fastest definatly better then the PWM system I have in the barn.
Plus it comes down to Battery type and amp hours
Lead Acid = high internal resestance ...slow charge
VRLA Valve Regulated Lead Acid ....slow charge .....cycle capacity sucks
Litium ION ..................................Fast charge high current capacity .........Fire and explosive Hazard
LiFEPo-4 ...........Fast charge ....high current .....high cycles ......best battery for solar the downfall is its the most expensive battery unless you take into account cycles and longevity
 
I plan on overpanneling like crazy. the challenge is to guess how much is too much or not enough. The long-term goal is to be able to recharge the batteries in a limited amount of sun exposure time.

Too much is Voc too high on a very cold day, or Isc exceeding spec (if inverter/SCC does spec that).
Too much is charging battery at a "C" rate that is too high according to its spec. Or too high for how cold the battery is.

If your charging system can regulate battery charge current you can get away with overpaneling more heavily. For my AGM bank I've set charge rate 0.2C, but have enough PV for about 0.6C; the extra production is only used for loads.

You probably have to consider what environment you keep your battery in, and set low-temperature disconnect depending on how high a charge current might be delivered.
 
Why off grid? Storage is expensive. The biggest bang for your buck will be insulation, and an energy audit and blower door test will be critical to insulating it right and sizing the heating / cooling system. How much do you care about temperature control? Are + - 10 or more degree swings and some cold rooms ok? If so, and you don't mind the work, concentrate on wood heating and save some money. If you want a constant temp with no swings, then go with something modern like a ground source heat pump. That might be overkill if you were to super-insulate the place. Then maybe you could do it with minisplits, and radiant would also be overkill. How open is the floor plan? That could determine how effective minisplits could be and how comfortable wood heating will be. Also, for financing you will need some sort of central heating system, so heating exclusively with wood and no backup is out.

Our previous house was an old farmhouse. We beefed up the insulation and air sealing as much as we could without going to extremes. Heated it for a number of years with wood and oil backup. Put in a ground source heat pump for the last 7 years we were there. Backup was electric. It was very efficient and the house was more comfortable than it ever was. Temp never varied from the set temp on the tstat and it was even room to room. During the depths of winter, though, electric bills will be elevated. This is exactly the time you won't be getting much solar power generated, so back to my question of why off-grid.

Once you get the insulation levels figured out, and a heat loss / heat gain calculated, you can figure out how best to heat and cool the place. Then you can calculate some sort of energy budget so you'll know how much solar to put in. Honestly, that should be the last thing you need to figure out. If you can't do these calculations yourself, get help from a good HVAC person or engineer. This could save you much aggravation (and money) in the future.
 
Last edited:
If you can't do these calculations yourself, get help from a good HVAC person or engineer. This could save you much aggravation (and money) in the future
I am more than open to suggestions on a good HVAC engineer.

I will get some solar to expand my current system to take advantage of the rebates. Can go grid-ties for not too much.

Why off grid? Did you see Texas? Mad rolling blackouts out West? A good ice storm here and the power can be out for a couple of weeks. Not only do I need to keep the family safe, but the animals still require care. Never mind the product in freezers. Just because I CAN does not mean I will at the moment. But having the plan enables setting the foundation for it.
 
Last edited:
@Prefersdirt I'm with you. I live in Texas, Houston to be exact, and yeah, that was a rude awaking, and on Valentines' too. I was in the hood, a poor section, and we were without power for five and a half days; it was below freezing and snowing for two. I could get around in my WJ Jeep if I could get around all of the cars and trucks who couldn't, but nothing was open; it was a nightmarish mess, surreal at times, frighting. What had me so upset was the feeling of being trapped with nowhere to go, surrounded by people who all felt the same way, most were helpless, and some had never seen weather this cold in their lives. I vowed never again to be caught off guard by relying on others to survive. By May, I had the 28-foot Class C RV I have now, it needs some work, nothing serious, and I'm close to having it road-ready with solar, which is one of the final steps. The engine and generator can run on gasoline or propane, and I carry 80 gallons of gas and 60 propane. That, along with a 400ah 24-volt battery bank and 1.5 to 2k plus of solar charging capabilities, I can survive. Screw relying on the grid, supply chains, or bureaucracy!
 
Why pellets vs firewood? I can get firewood with the equity of my sweat and some chainsaw / splitter work. Pellets requires me depend on someone else being able to take my money to give me something.
I couldn't agree more. I do get the convenience of pellets, I wouldn't have to go add wood at 2:00 in the morning when I take a piss; but relying on another person, and their equipment, sort of defeats the purpose for me.

I just bought a house with a wood stove, and I absolutely love it. We have about two acres of forest, so wood is plentiful and free. Burned properly, in an efficient stove, it's also considered one of the more sustainable fuels too.

Look into thermal mass. I've seen some cool building techniques that use heavy insulation materials to reduce the need for heating and cooling, sort of like a cave. I don't know how much you could retrofit on to an existing structure, but it's at least worth looking into.
 
What does it have for existing heat? forced air with ductwork with AC?

Ground loop geothermal heat pump for AC and heat. Water/water exchanger for both domestic hot water and radiant floor heat. You could mini split with in ceiling evaporators.

If you do something like a Matt Risinger style update you'll wrap the entire outside with zip board integrated insulation and sheathing. You'll need an air to air exchanger.

If i was going to ball park what I would need based on my 5500w system living on a homestead in IL that I've been runing for a year now....
Solark 12K with 10K solar. 560ah 48v battery. powering critical loads.
Likely another 10K of solaredge style gridtie only to offset power from non-critical loads that I consume from the grid.

Wattage above TBA based on energy audit.
 
I installed mini-splits in the 50yo house when the central air unit went out - very happy with them - 4th season with them. Quiet and efficient, and a fraction of the cost of a new central system. The old gas furnace still works good, took the cooling coil out and still use it with the heatpumps as backup.

If you're a DIY'r you can do the Mr. Cool ones yourself.

I got a 2-ton for the main part of the house and was so happy with it got a 1-ton for the master bedroom end of the 4-bedroom house. Now I would like to put a 2-head unit in the back bedrooms.

They're very modular without having all the duct work - that and the big units are big-$$. Kind of depends on the size of the place I guess.
 
A pellet stove will not get my vote for primary heat source. Pellet stoves can be efficient and convenient and could be used much of the time. What happens when you can't get pellets or one of the moving parts stops moving? You get to change your name to "I B Screwed".

I know a guy with a cozy warm <1000 square foot home on a farm in central Illinois. He has a monster wood burner (6 foot logs) outside and converted his electric furnace to transfer that heat into the house. Even stoking as infrequently as every 8 hours gets old as one gets old. A wood burning stove or two will certainly help prevent "couch potato" syndrome.

I am curious about the basement. Is it a full 1500 square feet, like the main floor?
What is the ceiling height of the basement, main floor and attic? I'm fishing for cubic feet of living space.
What will be the square footage of the living space in the attic when it is finished?

FREE STUFF⬇️
Perhaps during the rebuild you can consider the typical winds for some FREE climate control. Maybe the afternoon breeze can blow the cooler air from the basement throughout the house and take the heat out at an attic window or two

Clothes lines can seriously reduce energy consumption. We're hanging our skivvies out for the neighbors to see at any temp above freezing.

Functioning window shutters are another one of those freebies folks don't use much anymore.
 
To be off grid the most important thing you need to do first is planning around energy conservation eg Maximum insulation and ultra low consumption applicances

Next is looking at all the sources of energy you have available to you. Some are more efficient than others for different uses and your best not to have all your eggs in one basket

Battery electricity is not efficient for heating or cooking, propane is great for cooking. Geothermal is great for heating/cooling houses. Firewood is great for heating rooms

My friends rebuilt an old stone cottage in north wales (wet cold). They used ground source heating for hot water and underfloor heating. Pump ran off the electrical power of a light bulb. Worked really really well. Supplemented by wood stoves in a couple of rooms

They have a couple of solar light tubes which brought great light into dark areas of the house

They put a lot of energy into planning to make the whole house and energy efficient as possible. And this really paid off both short and long term
 
Last edited:
I would figure out how to insulate it as much as possible to include new efficent windows and then get a full manual J calculation done to figure out how much you need to heat/cool.

I wouldn't even go down the solar route until you have everything else figured out as you have a grid connection already and can see how much power you would need to be fully off-grid after you get all the updates done to the house.

I second this on the importance of R value and sealing the envelope. I would study up somewhat on 'passive home' strategies, and determine how you can renovate in a way that can seal the envelope, improve R value significantly, make use of natural effects (South Sun), capturing sunlight in South facing windows during Winter Sun angle, but awnings located to block Sun in South windows during Summer months. Thermal mass energy storage (dark colored cement floors the Sun will charge during Winter months, or brick walls to store energy from Sun), solarium concept.

There is a house I toured with our co-op group in Fountain Green, UT, David Allen, who built this house in the 90's, and it does not require a furnace or AC (6000 ft elevation), is completely passive (no fans or anything). He outlines 7 different principles involved in designing such a house. His site is here: http://www.allanstime.com/SolarHome/
He has a You Tube video tour as well:
(Many other great videos on passive home strategies as well, I also like many of the Kirsten Dirksen home tour videos, like the Earthship homes in Taos, NM and such)

I have also seen many references that home can be renovated to integrate these passive home strategies as well, in Canada there are even retrofitters that specialize in upgrading homes to passive, or net-zero strategy.

Not as if you would be able to build in all those strategies into an existing 100 year old home or not, but understanding the concepts, so you can decide how far it is practical to go with your home renovation, it is good to research it.

My goal would be to get the home to be as close to not requiring supplemental heating or cooling as possible, so then if you do need some supplemental HVAC system, it is only to fine tune the temperature.
 
Last edited:
Back
Top