Heating questions - Small Cabin Forum

- Forums - Register/Sign Up - Reply - Search - Statistics -

Small Cabin Forum / Cabin Construction / Heating questions


Author	Message
Rossman Member	# Posted: 21 Jan 2014 09:24am Reply Had some questions I hoped some of you might have some insight to. This year we are going to build our place, which is going to be a bit bigger than what generally gets built on this forum, but it will be about 1000 sq. ft. main floor and will have a full basement below that. We are trying to figure out how we want to do the heating, as we will be off-grid (no hydro at our site). Was originally considering a forced-air furnace run off propane but am now thinking, perhaps a gas fireplace/wood stove on each level would be enough? How do you know how many BTU's you need to heat a place? Are there some rule of thumb calculations? We will have double-stud walls and be well insulated so I think we probably don't need a whole ton of heating, but, just was not sure. If we can get away from the forced air furnace, thats one less electric device to power... Any advice/thoughts appreciated!

ShabinNo5 Member	# Posted: 21 Jan 2014 09:52am Reply Rossman, As you mentioned the insulation factors in, that includes how many windows. Any skylights? We have a skylight and insert 2" foam in the winter. My cousin has a 900 sqft home on slab (no basement). He justs has a propane fireplace. However, he also has a ceiling fan and has confirmed that if the fan is not running the lower half of the building gets cold. Another thought is to install floor vents to the basement and have a wood stove or pellet stove in the basement and let the natural rising of the heat move though the floor vents. Steve

bldginsp Member	# Posted: 21 Jan 2014 09:54am Reply Woodstove manufacturers generally will tell you how many square feet their stove should handle along with the BTU rating of the unit. For instance the Morso 1410 stove I have is rated at 30,000 BTUs and they say it will heat 1000 square feet. There are numerous other similarly sized woodstoves. I think a major issue for you is how to heat both floors adequately. A woodstove on both floors would do the job of course, if you want to do that, but be aware that you will spend a lot of money on the stovepipe and chimney components for such a setup, probably significantly more than for the stoves themselves. Two stoves, $1000 each, $2500 for chimney etc, it adds up fast. Avoid the cheap stoves that are not sealed well enough to regulate the heat output. Good luck!

Scott_T Member	# Posted: 21 Jan 2014 10:21am Reply You might consider a soapstone stove (Hearthstone) as they are supposedly good at providing even heat dissipation because of their high thermal mass. They are beautiful looking too.

Rossman Member	# Posted: 21 Jan 2014 11:43am - Edited by: Rossman Reply Quoting: ShabinNo5 As you mentioned the insulation factors in, that includes how many windows. Any skylights? We have a skylight and insert 2" foam in the winter. We will not have any skylights. Our windows are going to be all new, energy efficient dealies...U value of 0.24 I believe...we will have I guess what is an average amount of windows - no crazy all glass walls or anything like that! We will definitely have a direct vent gas fireplace (this model specifically, 24,000BTU which is not too much) on the main floor at one end of the house. The question then becomes, for the rest of the house should we put in a forced air furnace in, or just a Kimberly or Katydid (if it gets CSA approval sometime soon) wood stove in the basement at the other end of the house. EDIT: We also plan to have ceiling fans for better air circulation! Thanks very much for the feedback thus far!

TheCabinCalls Member	# Posted: 21 Jan 2014 12:17pm Reply Couple of questions to consider: - are you going to live there full time? - are you going to leave it heated all the time in the winter? If you are not and you expect it to get up to temp in a hurry when you arrive you need something that can rapidly heat the place. We used radiant floor heating, which is amazing, but takes time to respond. - are you going overkill or bare minimum on insulated and eliminating thermal bridging? this makes huge difference on the BTU rating...and could drastically reduce energy consumption, which is key to off grid. We super-insulated and use radiant heat and our gas usage is very small. We heat the 980 sqft place with an on-demand water heater. - will you have any high ceiling? If you heat the air it will rise. If you use radiant heat it will stay near the heat source.

Rossman Member	# Posted: 21 Jan 2014 12:40pm Reply Quoting: TheCabinCalls - are you going to live there full time? Yessir! Quoting: TheCabinCalls - are you going to leave it heated all the time in the winter? If you are not and you expect it to get up to temp in a hurry when you arrive you need something that can rapidly heat the place. We used radiant floor heating, which is amazing, but takes time to respond. Yes, full time living! Quoting: TheCabinCalls - are you going overkill or bare minimum on insulated and eliminating thermal bridging? this makes huge difference on the BTU rating...and could drastically reduce energy consumption, which is key to off grid. We super-insulated and use radiant heat and our gas usage is very small. We heat the 980 sqft place with an on-demand water heater. Our exterior walls will be 2x4" framed wall, 1" gap to reduce thermal bridging, and another 2x4" framed wall. So, all in about 8.5" of insulation with no thermal bridging. We will use Roxul rockwool insulation. We plan to overdo it on the insulation, it really is not that expensive... Quoting: TheCabinCalls - will you have any high ceiling? If you heat the air it will rise. If you use radiant heat it will stay near the heat source. No, no cathedral ceiling, just your standard attic space which we will put a ton of insulation in! Thanks!

bldginsp Member	# Posted: 21 Jan 2014 06:29pm Reply I spoke to an energy analyst guy who told me that overdoing the insulation, without calculating for window loss, can be very wasteful. Seems to me the better your walls are insulated, so much the better in any event, but his point was that if you have a large proportion of window area the cold comes in by buckets while the extra insulation saves teaspoons. Maybe you are far ahead of me on this one, but just to make the point that superinsulating walls may not put you ahead that much, depending on window area and other factors In Europe some people have taken to building super insulated houses with R50 walls etc, and they use a bare minimum of windows. I wouldn't want to do that, but the end result is that the house stays heated by body heat, electric lights, cooking etc with no other heat source. But to do that the windows have to be small and few.

hueyjazz Member	# Posted: 21 Jan 2014 07:06pm Reply The super insulated houses have always suffered from poor ventilation. Trapped water vapor can lead to condensation and mold problems. Cook a fresh on Friday and enjoy the aroma next Thursday. In the Jimmy Carter days several of these Low-E homes were built with disastrous results. In fact many office buildings fell to the peril too prompting the EPA to react to sick building syndrome. I'm sure there must be a correct way to do it but it must include bringing in outdoor fresh air. This would defeat some of the benefit. The better balance is to adequately insulate to the climate. ASHRAE is the best source of calculations and standards but there are many wildcards. Exposure, climate, degree days, humidity etc.

PatrickH Member	# Posted: 21 Jan 2014 07:11pm Reply At our place we have baseboard heaters which where ok but they dont circulate the heat I found out that it is very important otherwise its very uneven then I added a 50,000 btu pellet stove but that needs electricity to power the auger and the exhaust/room fans but works awesome only uses a 3" vent and can just go up and out the side of the house and there is a guy here in MN that makes boiler add on kits to heat water with one heat sorce I may do something like that with ours I have lived in homes that 100% only use wood stoves to heat dont under estimate the amount of time and effort required to soley heat with log wood. I personally like water heat you can regulate each room can heat the water with gas,propane,wood but you need electricity and some knowledge we are going to live in our place full time also and I will do some electric floor heat some baseboards and the pellet stove of course and have some grid tied solar to help with the electric cost. And my uncle has one of those soapstone heaters they call it a cockleoven something like that its massive and cool to look at uses a tiny bit of wood but doesnt put out tons of heat it heats a good size room but its just a big radiator and big$$$.

silverwaterlady Member	# Posted: 21 Jan 2014 07:13pm Reply Hi Rossman,If the Kimberly gets CSA approval can you let me know? I would really love a review on the stove as well if you get one. Thanks!

rockies Member	# Posted: 21 Jan 2014 09:37pm Reply I don't like wood stoves. There, I said it and I'm glad! lol. A wood stove takes up a lot of space in a room (clearances, etc) and for half the year (late spring, summer and early fall) it's just sitting there unused. In addition, all the mess of bringing in wood, carrying out ash, cleaning out the chimney soot, etc, PLUS few people consider how the amount of excess moisture put into the home from the wood itself will affect the structure (and the possible bugs/mold that comes inside with wet wood as well). You are already putting in a direct vent gas fireplace presumably for the look of a fire on cold winter nights (which can add a lot of moisture to the air as well) but you don't mention anything about how you're going to heat your water for showering, dishes, laundry, etc. Therefore, I would suggest you use an "Indoor Furnace" located in a small outbuilding for heat and hot water. I am going to use the Empyre Elite 100 from Profab. All the mess of a wood burning appliance is kept out of the main cabin, you can heat several buildings with just one furnace using radiant floor tubing, and you get free hot water from the same furnace. Plus even in hot summer months you can still run the furnace and get all the hot water you want and any excess heat not needed for the radiant floor tubing is kept out in the outbuilding.

Rossman Member	# Posted: 22 Jan 2014 08:05am Reply Quoting: silverwaterlady Hi Rossman,If the Kimberly gets CSA approval can you let me know? I would really love a review on the stove as well if you get one. Thanks! Seems the Kimberly is already CSA approved. The Katydid is not, I had an exchange with the inventor and he said he has to sell more Kimberlys and Katydids where approvals are not required, to fund the approval for the Katydid (approval costs ~$25k). I wouldn't hold my breath on the Katydid...prob be a few years by the looks.

beachman Member	# Posted: 22 Jan 2014 08:38am Reply Rockies - I know what you mean but I happen to love them. I love splitting the wood, starting the fire (probably some pyro in my ancestry) and the smell of the nice wood smoke. I find it very relaxing. Yes, the mess and other things you mention all come with it but I feel it is worth it. AND, there is nothing like the heat from a wood stove. We have Pacific Vista with legs and an ash drawer, which makes cleaning easier. The firebox has a secondary burner for the exhaust fumes and the fire keeps the front glass fairly clean. It heats our 600sf cabin perfectly and on rainy days with the windows open, a small fire keeps the place nice and dry.

Rossman Member	# Posted: 22 Jan 2014 10:43am Reply Quoting: bldginsp I spoke to an energy analyst guy who told me that overdoing the insulation, without calculating for window loss, can be very wasteful. Seems to me the better your walls are insulated, so much the better in any event, but his point was that if you have a large proportion of window area the cold comes in by buckets while the extra insulation saves teaspoons. Maybe you are far ahead of me on this one, but just to make the point that superinsulating walls may not put you ahead that much, depending on window area and other factors This is a great point! We have tried to use smaller windows on the north facing sides and larger on the south facing to optimize the passive solar footprint of the house.

bldginsp Member	# Posted: 22 Jan 2014 11:16am - Edited by: bldginsp Reply Rossman- the energy analyst I spoke to is a California Title 24 consultant. In this state you are required to get a certified analyst to run an analysis of your building and meet certain regulations regarding energy use. I did that for my cabin. You are probably not required to do that where you are, but if you are going to the extra effort and expense of double wall and double insulation, it might be a good idea to have an analyst run the numbers on your project and tell you what they think. They take into account which direction windows face etc. Might spur you to make a few changes, maybe it would just confirm your intuitive design. They have computer programs that run the numbers and show how energy efficient the building design is. Only cost me $100 to have it done. hueyjazz- you are absolutely right that the superinsulated houses have had serious ventilation problems. So they come up with solutions, such as introducing outside air through heat exchangers so that you get fresh air but don't lose the internal heat. In California now there is a requirement in houses for a 'whole house fan' that continually throws air, in small amounts, out of the house to remove moisture, because all the other requirements for energy cause some houses to build moisture. I'm not advocating for either way, I just see it as a sign of the times. The older tract homes here in CA from the 60s and 70s were very 'loose' houses in terms of energy efficiency, but they certainly didn't have moisture problems.

Rossman Member	# Posted: 22 Jan 2014 12:24pm Reply Quoting: bldginsp Rossman- the energy analyst I spoke to is a California Title 24 consultant. In this state you are required to get a certified analyst to run an analysis of your building and meet certain regulations regarding energy use. I did that for my cabin. You are probably not required to do that where you are, but if you are going to the extra effort and expense of double wall and double insulation, it might be a good idea to have an analyst run the numbers on your project and tell you what they think. They take into account which direction windows face etc. Might spur you to make a few changes, maybe it would just confirm your intuitive design. They have computer programs that run the numbers and show how energy efficient the building design is. Only cost me $100 to have it done. It's a good idea, and I think I have to have something like that done if I want a forced-air gas/propane furnace. I will have to track someone down for this I suppose.

Rossman Member	# Posted: 22 Jan 2014 12:57pm Reply Quoting: bldginsp Only cost me $100 to have it done. Just got a quote back from one guy, wants $600+tax to do this stuff! That seems a fair amount for really what should be a small amount of work. I can't help but wonder if there is a way to just do the math oneself...

MtnDon Member	# Posted: 22 Jan 2014 02:39pm Reply Reschek lets you enter wall, window, etc info. It's a free download. My state requires its use when submitting plans for approval; others may too. It permits adjusting the window sizes and insulation levels, etc to come up with a pass. We print a copy of the report and submit with the plans.

rockies Member	# Posted: 22 Jan 2014 04:44pm Reply Beachman, I can certainly understand the appeal of a fire on a cold night with the blizzard outside, etc, and dealing with the mess of ash and soot, etc is just a natural part of heating with wood. What I don't like is the amount of space taken up by the wood stove itself (plus the necessary clearances to combustible materials) while it sits there unused for half the year because you don't need the heat in the warmer months (especially in a small cabin where every inch counts). A wood stove can take up 36 square feet or more of floorspace, and if you're going to have a fire anyways, why not get free hot water using an indoor furnace? In the summer you can even get hot water from the furnace and not worry about over-heating the cabin since the furnace is kept in an outbuilding. You could use solar in the summer for hot water instead, but in winter time is when you need hot water the most and it is unfortunately the most difficult time to heat water with solar, so the furnace is ideal. Since Rossman is already going to put in a gas fire, why waste space on more wood stoves? Plus if he ever adds a workshop, garage or a bunkie in the future he could heat all those building with the one indoor furnace as well.

Rossman Member	# Posted: 22 Jan 2014 04:59pm Reply Quoting: MtnDon Reschek lets you enter wall, window, etc info. It's a free download. My state requires its use when submitting plans for approval; others may too. It permits adjusting the window sizes and insulation levels, etc to come up with a pass. We print a copy of the report and submit with the plans. Thanks MtnDon! We don't seem to require this for our building permit, but when I talked to a local propane supplier, I think that you have to have this done if you are heating with forced air gas furnaces. Anyway hopefully the tool you linked to will provide some insight!

silverwaterlady Member	# Posted: 22 Jan 2014 05:13pm - Edited by: silverwaterlady Reply Thanks for the info Rossman!

Rossman Member	# Posted: 22 Jan 2014 05:28pm Reply MtnDon - what is the "continuous R-value" all about? I can figure out my cavity R-value from the insulation I will use but I don't know how to figure out what R-value the sheathing has? So far with the ceiling, walls, doors, and most of the windows added I am "13% better than code" (if I've done this right).

MtnDon Member	# Posted: 22 Jan 2014 06:17pm - Edited by: MtnDon Reply Quoting: Rossman "continuous R-value" If the wall is sheathed with something like foam board that is continuous insulation. Or in your case if you have inner and outer stud walls with a continuous layer of rock wool between them, that R-value goes in there. I find it an interesting tool as it lets you see the advantage gained by using a continuous layer of insulation as well as seeing how you can make trades of more wall or ceiling insulation to offset a larger window, for example. It shows how difficult that can be. It is a USA tool so just pick a similar climate zone and choose the latest code versions to make a best case study. When we did our cabin we went overboard so to speak; something like 20% better than code. It shows in the low amount of winter heating fuel used. Yeah we burn wood, but it means I have to cut, haul, split less, remove less ashes, etc.

Rossman Member	# Posted: 22 Jan 2014 09:00pm Reply Quoting: MtnDon It is a USA tool so just pick a similar climate zone and choose the latest code versions to make a best case study. It seems to have Canadian location data in it...I was able to find a town very close to mine! Anyway thanks again for the info I appreciate it!