Sunday, January 30, 2011

Heating Thoughts

Today, my small solar setup would run a forced air furnace easily, although my battery bank would probably not be large enough to run it for the night. Thats with the system I am running at the moment. My battery bank at the moment is 6 12 volt deep cycle/marine batteries.
My prosine inverter controller is showing that my 6 12volt batteries are at +7C for a temperature as the outside temp is -18 C according to my thermometer. I hav'nt had the battery warmers on since about 10:00 pm the previous night.

My charge controller is showing some pretty fair power coming in from the solar panels today. The sun is just starting to peak over the trees.
WARNING: The following writeup about heating may be a long drawn out boring piece of literature to some. But someone may be interested. Just wanted to think out loud for a bit. I wrote it last night, and added things here and there and even a little more today. It could be all mixed up, but what ever. Personally, I hate reading real long blogs myself, I don't like writing them much either and I sure don't expect anyone to read it, but it is there anyway.

I have been working off and on lately. I have had a fair bit of time off awhile back, and it was in a real cold snap that we had for awhile there. I did'nt accomplish a whole lot on the house, but as usual, I have been doing ALOT of researching on various different topics pertaining to my project. One subject that has really got my mind going, is heating. As we should all know by now is that I kinda learn things as I go. I initially thought I was going to heat my basement with a propane space heater in the basement. I was even thinking about another high efficient (power vented) heater up in the living area somewhere, along with the wood stove. It would all work, but it really would'nt be very energy efficient, while I were away. I am basing this presumption on my experience with the space heater in my shack. My heat bill in the little shack is probably about twice of what it is in my mobile home that I have rented out in town. And the shack is alot smaller to heat, although it does have it's leaky areas, I guess. There other reasons against it also. What is the solution? I sometimes wonder. I have researched hydronics, which is when you circulate hot water (etc) through pipes to heat floors, or baseboard type radiators etc.) It is supposed to consume little electrical energy to run the pumps to circulate the water, but it does use power. I could use an on demand type water heater to heat the water(uses power when operating also, and I personally think alot of gas energy also, but I don't know that for sure). Or I could use a normal hot water tank(boiler). These would probably be an ok type heat system, but it just is'nt for me. In my opinion, they probably use less electrical energy while running, but probably have to run more. I am looking for a quick heat fix when I want it. When I come home on a cold winter day, I plan on lighting a fire in the wood stove. I just need something to keep the chill off while I'm away, and keep me nice and cozy at night while sleeping.
What I am seriously thinking about kinda goes against anything that I research on the internet. You don't often hear about people using forced air furnace to heat a Renewable Energy home, but I have done alot of research and figuring, and I honestly think it will end up being my solution. They work pretty good in an RV. I realize that for about 3 months in the winter, I will definately not be able to rely on incoming solar energy to power this thing, but I am seriously going to make it work somehow. It is kinda chilly in our parts off and on all year long, but in the summer, we probably get alot more sunlight than most of our southern neighbors. A little further north is known as the land of the midnight sun, after all. I find with my small system I have in my shack right now, that I tend to waste alot of the available sunlight I do have. For most of the year, my batteries are full by noon and the charging system shuts down as the ole sun just keeps on shining.

Sure, everyone thinks I'm nuts. Anyone out there think I'm nuts? lol. The way I have it all figured out is that, if my furnace ran, 1/2 of the time(12 hours per day), and with no incoming charge going to the battery bank, I would bring my battery bank down to about 35% depth of discharge. Which means my batteries would still be at 65% state of charge. This figure based on 24 Trojan T-105 6 volt batteries. Not saying this is what will be used, but this is what the calculation is based upon. They are 225 amp/hr batteries @20 hour rate. I also don't ever expect the furnace to run half the time. It could I guess on the coldest of cold days, but I really don't think so. In my calculation, I allowed for 80% efficency for the batteries, then I also allowed for another 80% efficiency after that, just for the heck of it, for inverter efficiency loss etc. I also added some watt/hrs (150) onto the furnace for a total of 600 watts, just incase I missed something there. The furnace is 66,000 btu 93% efficeincy rate(the one I have my eye on). Somehow I have figured that a Honda eu6500 generator should bring the batteries right back up in about an hour of charging for each day, but that is only if there is no other incoming charge, and in the real cold weather. I think that the furnace would run less than 1/3 the time (8 hours per 24 hour period) if it were -25C/-6F. We get alot of days that are alot warmer than this in the winter, but then we do get some that are alot colder also.
When it was -17 one day awhile ago, I experimented with my 24 foot holiday trailer. I turned the furnace on, and timed things as they happend. I brought it to a pretty nice temp in a relatively short period of time. That trailer is not very well insulated and has alot of single pane windows and thin walls. But it really did'nt seem to take long for that small 12 volt forced air furnace to warm it up nicely in there.

I also experimented at work one day. We recently set up an office shack outside the shop at work for the safety hand, and my foreman. An area of it also became our coffee room, which is pretty handy for me to perform some experiments. It's furnace is about the same btu rating as the one I have my eye on, although I don't know the fan cfm. It was -25C one day when I got in from trucking. I sat in there invading some goodies in the fridge and hot chocolate etc, and I timed the furnace run time and off time. The furnace in there ran pretty close to 1/3 the time on that cold day. I did open the entrance door 2 or 3 times in this period also. This building is roughly 14 feet wide, by 60 feet long (I paced it off). It is on skids, so the floor would cool off quicker that way also. A rough calculation of walls and roof are as follows. Experimental shack :3160 square feet. My House 2928 sqaure feet. My basement walls are 8 inch lumber and the upper parts are 6 inch, which is the same as the experimental shack. Four feet of the total wall area of my house is below grade which should really help. If a 600 watt furnace ran at 1/3 time all winter, it would'nt hurt my feelings, but it won't, I just know it. While I'm there, I will be burning wood. When I am gone, the furnace gets turned right down, as it should'nt take long to bring the temp back up again when I get home. A forced air furnace will be really nice at night while sleeping etc.

The plan at this time is to utilize an automatic starting generator, which is subject to automatically start up when the battery bank voltage gets down to a certain voltage setting. If for some reason the generator fails to start (which is quite a possibility), the inverter would eventually shut down at a preset battery voltage also, so as not to over discharge the batteries. I would think the furnace should run for at least two days before the inverter shutting down though. Then there is going to be a direct vent propane heater that should eventually kick in at an above freezing temp in the basement. All the plumbing and things in danger of freezing in my house are in 1/3 area all in one end of the house. I'm pretty sure it would'nt take much of a heater to keep things from freezing right up. Example:They built an entrance way on the shack at work that goes from the shop to the shack. I walked from the shop to the shack the other night for the first time in this insulated porch, and could'nt believe just how warm it was in there, with just the heat from the shack and shop warming it through the closed doors, and I guess the heat that enters from opening the doors periodically to enter the buildings. The outside temperature was quite bitter, about -20C with a wind. I might even eventually put in some kind of a hydronic system for when I do leave for a week or so maybe, even if it is just a real small system for experimental purposes. The possibilities are endless. All my furnace calculations were assuming cold temps and no other means of incoming charge. When ever the sun shines, that will be a big bonus, when I am at home, wood is burnt, and I also plan on eventually bringing in some wind power. If I ever decide, at some time in my life, to go away for a long time in the winter, such as the Canada goose does, I think I would simply winterize things just like I do my RV, and let it freeze up. Why not? Seems to me alot better than running a furnace for a month in the winter when you're not there anyway.

A little while ago, I was actually having second thoughts about even staying off the grid. I was doing some real serious calculations to see if it were even going to be worth it, as there is power pretty close by that I could always hook into. It would cost anywhere from $8500 to $12,000 or more to hook into the grid, then the monthly bills that follow for ever. But holy cow, how convenient would that be? lol. I could keep my solar setup under that price, but with a furnace it is probably going to end up being more, but then alot of the equipment is resaleable. Generators don't run for free though, and they tend to wear out with use. Sometimes I still do wonder if it will all be worth it, but then I come back to my senses. I know it will benefit me a little financially over time, as long as I can get a few years out of my batteries. But most importantly, is that I plan to live off grid mostly because of my love of learning new things, and I have a real interest in alternative energy. Just coming up with the ultimate solution and proving all the naysayers wrong makes it all worth the while right there. It is my entertainment. If things don't work out with it, or I get tired of the extra maintenance and everything that goes with it, then I can always, in the future hook right into that pole that goes through my yard. But I am going to put up a heck of a fight to avoid it for now. P.S. I know the generator thing sounds kinda harsh, but with or without a forced air furnace, the generator will need to be utilized at times in the winter in these parts. By mid February the sun starts getting higher and higher actually quite rapidly as the days go by, and there is still alot of winter like weather at these times. This is where I really think the forced air furnace will shine and also in the fall. I am still in the process of educating myself though and I am looking a little deeper into hydronic heating before actually making a decision. If I did both, I guess I can’t really go wrong.

I have been trying to stay away from using a B-type vent/chimney system, which was going to be part of the initial plan. A boiler would probably require this type of vent. There are high efficient boilers, but I believe they are pretty expensive and they require electrical energy to run also. High efficient appliances use pvc pipe going out the side of the house as their exhaust and incoming combustion air source. The initial plan was as follows, but it just seems to me, that what could end up being a problem is the permitting process. I seem to always forget that you can’t just do what you think is right. I know I could design a good working system, even if I do have to make some modifications as I go in order to perfect it. My plan was to have about a 50000 btu B vent type propane space heater at one end of the house in the basement. It would be in the end with all the plumbing. Above the heater would be a duct hole leading into the bathroom, and one into the kitchen up above. There could also be a couple in the living area, just so basement heat can rise through them. There could have even been a thermostatically controlled fan to force some heat into those areas when I am home. I could have even plumbed one up to the loft through a bathroom closet for night time comfort. The space heater can come complete with an optional fan mounted right on it. Come home flick a switch up stairs to turn on the fan and whole basement circulates heat which in turn should send some upwards. But then with return air, and heat recovery system issues etc. (I would have to bring in outside air for combustion air) I guess if I go this way, I might as well just do the furnace and be done with it. I was planning on forcing hot air from high above down to the basement while the wood stove was running, so this would help heat the basement with wood heat while I were there, in order to save on heating fuel. When I write or talk about it, I know it probably sounds stupid, but I think I was on to something. If it were not a code approved home, I would get a lot of things done a lot quicker, and I would just do what I want and no one would even know until it was all up and running, and working well. It seems to me though, when I think about, this system would more or less end being an oversized amateur built inefficient furnace, that ended up costing a lot more and taking up a lot more space and burns a lot more propane. So I am really thinking a smaller high efficient furnace, with auto gen start, and back up direct vent space heater as a last resort incase things decide not to run when I am away for 3 days or so. Still thinking though.
Ultimately, my plan was to have absolutely no electrical power usage going on while I were away, but I also would like to keep energy efficiency in mind. With a forced air furnace, I realize there are going to be a lot of days where a generator will have to run for an hour per day or more, but there are also going to be a lot of days where it won’t also. I really believe it would pay off on the yearly average. One other little thing that I keep in mind is that, I am guessing, but I’ll bet on a -30C day, I could walk away from the house when it was warmed up, and if there were no heat source at all while I were away, I don’t think anything in the house would start to freeze up for probably a couple days anyway. I am basing this on my experience with batteries that I keep in the deep freeze outside to power my shack at the moment. I did’nt take note of my battery temperature last night when I went to bed, but it was -30C overnight and my batteries at this moment are at +7C at this moment 12:30 pm the next day. It is -18 outside right now. I have noticed that my batteries have always taken at least two days before dropping below freezing. If that thin deepfreeze is going to hold heat that long, I think my house should hold some heat for awhile also with no one there to open and close doors all day. Any thoughts?


This is a personal blog, mainly for my own use. I am building a house with my own two hands, but I am learning alot of things as I go. I do not claim to know what I am doing, or if anything I do is even close to being done correctly or safely. So please, if you are planning on using any of my ideas or methods for your own use, please get professional advice before actually following through with your actions. I will not be held responsible for any injuries or damages of any kind caused by information or comments from this blog.


  1. Hermit,
    Its so good to see you again. What if you insulated like crazy with the thickest insulation you can find for yer walls, floor, and roof? It seems that that would help keeping the place warm, implementing a heat element with it of course. ~Jen

  2. Hey Jen. Good to see you too. The walls are built and I have to insulate to what they are. They are 2x6 studs up, and 2x8 in the basement. The cieling will be some pretty thick stuff. The house will be insulated real good. Along With an air barrier on the outside(tyvek), and vapour barrier on the inside (6 mm plastic). It really should hold the heat good, especially if no is there to open the doors.

  3. It's not just the container your batteries are in that keep them warm. They generate heat themselves during all charging and discharging.

    Canadian winters sure do add some challenges for offgridders. One thing we are doing is incorporating tons of thermal mass in our design. Works like a storage battery for heat. A big part of this for us is the rocket mass heater. Have you heard of rocket stoves?

  4. Hey Muddome.
    Ya, I often thought the batteries could be making or holding some of they're own heat. They had to be, but a well insulated structure will hold it's temp for quite awhile.
    I agree that Canadian winters are challenging for off gridding, but it does kinda add to the fun of trying to come up with an ultimate system. I have never heard of the rocket stoves till now. I checked it out a few minutes ago. It is pretty interesting and I'll do a bit more research on the topic. I have done a little bit of research on the soapstone stoves awhile back. They're sort of a thermal mass type system themselves. Purty costly though, but pretty easy to look at also. Thanks for the info.

  5. Do you have a "MUD ROOM" where you walk in and have an area to take off boots and jackets. Then another door to enter the home? I think these are a great idea...I don't like windmills as I just do not care for the noise. I don't believe the forced air would work with watt hog fans running. Wood or wood pellet stoves are nice and there are heat activated fans to help spread the heat. I think if you went on grid they will take your extra power then you can get it back when you need it and don't have to buy all the batteries for energy storage. That isn't offered in my area as I am to far from the poles. Lot's to think about.

  6. Hello Frann.
    No mudroom. I agree it would be a good idea and one could always be added on later if need be. My only concern is for when I'm not at home though, and when I'm not home the door stays shut anyway. New houses up here are built so air tight, that it does'nt hurt to let some new fresh air in once inawhile anyway I think. I have been paying attention to some wind turbines around here, but never get close enough to actually hear one yet. I'll have to check that out a little closer sometime. I realize that forced air furnaces like to use some energy, and when I mention that and solar power in one sentence, I seem to get alot of different reactions from people. Everyone assumes that I just fell off the turnip truck or something. Alot of those people still don't realize that I run all my power tools off solar power too. No one seems to realize that there is an actual plan to it all. I do have a plan and I thing a very well thought out one. Alot of the time when I heat water for an instant coffee or tea, I will heat it on the propane stove, but if the sun is shining, I always do it in the microwave. The microwave is free energy when the sun is shining, as would be a forced air furnace fan. If I don't utilize the sun when it is shining, I kinda feel like I am wasting good energy right there. Ya, I know, the sun don't always shine. Alot of the time it don't here in the winter, but yet alot of the time it does. About 3 months out of the year will be a struggle, but the other 9, I think, will be clear sailing because of warmer and longer days. Alot longer days. When I am working in the house, I have tried two different heaters. One is propane, the other propane with forced air. The propane with forced air really seems to make it alot nicer and alot quicker and there is no insulation yet. It is powered by my small solar power system usually unless the snow is flying. My power system is going to grow eventually.
    A forced air furnace would be just one part of the whole heating system. I am going to have a wood stove and it will be complete with an eco fan and and optional electric blower. I also plan on having a propane space heater in the basement, but only want to use it as a last resort. In my opinion, I think it would be more energy efficient to run a gen and high efficient furnace on the not so sunny days than it would be to run an inefficient space heater without a fan. I could be wrong, but I could be right. If I'm not home, the doors are not opening and closing, so a well insulated, smaller, tightly sealed home really should'nt allow a furnace to run all that much anyway. But then, I do realize there are going to be the real cold days. It's something I just have to try though. Initially I wanted to have no power consumption when I were away, but when I think about it, that is not a very energy efficient way either. I like experimenting with things and making it better as I go. I have done alot of research on grid tied systems also. It is something that I would rather try to steer clear from for now, but I do know that it could always be an option for me in the future if need be. I like to be independent and have my own power company. It is all a part of my early retirement plan. It seems that no matter which way I go, it's still going to cost something. I've looked into pellet stoves, but they do require power too, and those little pellets cost also. I hav'nt had any hands on experience with them, but I think they can actually use a fair bit of pellets in a day. I just might have to put in a little more time on this subject though.
    Eventually, I think I will be spending more and more time at home instead of always at work, so usually the wood stove should be doing most of the work, and the forced air furnace can kick in sometime in the middle of the night to finish the job until morning. Thats kinda the way I'm thinking. Thanks for your ideas Frann.

  7. Hey Mark, good to see you posting again. I don't have any ideas for your solar set-up and heating; still working that out for myself. However, I did read where you plan to run an inside vapor barrier in addition to the outside Tyvek. You might want to reconsider this inside vapor barrier. Houses actually need to 'breathe' as they draw air through the walls. It alternates which way the air goes depending on the season but installing a vapor barrier on the inside can actually trap moisture inside the walls, in your insulation, and then you get mold growing in the insulation.
    I don't want to sound like a big know-it-all or whatever but do a little more research on this. Most heat loss in houses is through the ceiling and windows anyway.

  8. Hey Annie, good to see you again. This is a prime example of different rules for different climates, I guess. Up here they seal them tight. It's called your building envelope. They say having even one tiny little unsealed area in your vapour barrier will promote molding. They don't want air seeping in or out of the walls. Instead we incorpate a HRV (Heat Recovery Ventilator), as one option for letting a house breath. It is stuff like this that I learn along the way that kinda slows down my building process. I'm still trying to figure out what I gotta do with my heating situation. The air barrier on the outside (Tyvek)is supposed to keep moisture from entering, and at the same time, is supposed to let moisture out if for some reason it did get in there.
    Here is a sentence from my building permit under the category of insulation. "A continuous 0.15mm (6 mil)vapour barrier, CGSB approved, is to be provided on the warm side of the insulation".
    It is kinda funny how things are done so differently from place to place. Thanks for the heads up Annie.

  9. Mark, you're doing such a great job. Thanks for doing all of the research for the rest of us.
    I learn something new every time I visit your blog. :)

  10. Thanks Jeanie. Ya know, I've been researching this stuff for years and years, and I'm still stumped. lol. Up here it's kinda hard because not very many businesses have much to do with renewable energy. It's hard to find supplies and equipment. When you do they want an arm and a leg.

  11. Aaah, well, since it is in your building code then it's a do it anyway. That's very interesting. Vapor barriers and all are a bit of a voodoo science it seems sometimes and I'm still a bit skeptical of their reasoning, but like you say, it's a completely different climate that you are in than me. Well, I'll quite flapping my gums at you; you are doing a great job on your house and do have those inspectors to guide you also.

  12. Annie. Lol. I'm sure not disagreeing with ya though. Some things don't make alot of sense to me also. We build homes so tight now days, that we then need to install other, electrical powered devices to bring fresh air in. I don't really see where the sense is to it all, but whatever. This is why I'm kinda leaning toward high efficiency heating sources that use outside air as combustion air. If I have a heat source that gets it's combustion air from inside the house, then I need to pump in more air from outside anyway. Seems with every good thing, also comes a bad thing. Anyway, please don't stop bringing me advice, as I do pick up a little here and there from it. I do take it all pretty seriously.


    On this page it shows what this guy uses for heat. Black rocks under plexi-glass with an opening on the bottom at one end and on the high end on the house side.

  14. Hey Frann. I did'nt know your comment was here until just now. I checked that link out. Looks like an intersting way of heating a house and I've never seen that before. I don't think it would have done a very good job of heating a house up here today though. It has been pretty nibbly here lately. I seen the truck thermometer dip to -39 Celcius in places out in the bushes today. Thats pretty close to the same in Farenheit at this temp. Minus -40 Celcius and Farenheit are the same temp.