Wood stove sizing advice

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PA452

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Jan 8, 2023
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PA
We're in the middle of constructing a new home and we're planning on two wood stoves as supplemental/backup heat. For venting, the stoves will share a framed chase so they will each sit on the same side of the house, essentially one right above the other in the basement and living room.

The basement is mostly wide open and it's a fairly large area (roughly 1800 sqft), insulated (Superior Walls precast foundation), and below grade on three sides with the exposed side being the side with the stove. My thought is I'd like to be able to heat the basement with the basement stove, but also hoping some of that heat will permeate up through the floor to the first floor. There's also a stairwell running up to the first floor that will have a door at the top, but naturally could be kept open in the winter.

The first floor is then also roughly 1800 sqft, not open concept. The stove will be in the living room which is about 18x18, cathedral ceiling. There are open doorways into the neighboring kitchen/dining area and a hallway running to some other rooms. Also up high within the living room is a small door/window that can be opened to allow heat into the second floor, which is around 1300 sqft of heating area depending on how you look at it.

For the basement stove, I had a local dealer recommend something rated for 2000-2500 sqft. I'd like a long burn time on that one. I was thinking maybe a Blaze King King 40 or Princess 32?

The living room first floor stove is the bigger question for me, and the more difficult one. The first floor and second floor areas are larger combined to heat, but I also assume with the walls and obstacles there's no way a stove on one side of the house can be used to heat all that space. I would think in order for it to provide any heat to the further reaches of those floors, the living room would end up being unbearably hot. So my question then is, what size stove would make sense in the living room in this situation?

Thanks
 
It doesn't sound like you will need the extra tank size of the BK40 for the basement. The Princess should suffice. In this range, the Regency 3500, and the Woodstock Ideal Steel would also work. In milder weather, if convection is good, the stove may heat the whole house. Pland on an outside air connection for the stove.

We need to know more about the upper floor layout. Will there be 2 stories? What will be the total sq ftg, not including the basement? Can you post a sketch of the 1st floor plan that includes stove and stairwell(s) locations?
 
Thanks for the reply!

It's a 1.5 story plus basement; in other words there is a second floor but it doesn't have the same area as the first floor.

On the first floor, we're at approximately 1750ft². The second floor, we're heating about 840ft² above the first floor, plus there's a very large heated bonus room above the attached garage, about 575ft². So if you include that, 1415ft² on the second floor for a total of 3165ft².

Here's the basic layout of the first and second floors, laid out over an image of the foundation.

First floor:

The chase is on the north side of the living room, you can see the bump-out for it. The openings from the living room to the kitchen and dining area are wide open, no doors, as is the opening to the hallway to the east. The living room has a high, cathedral ceiling. We will have a ceiling fan in that room. The little yellow star indicates where we have an open window in that room to the second floor. To explain, the guy who designed the house for us put what he called a "lounge" on the second floor when you get to the top of the stairs; it had a section that was wide open (with railing) to the first floor overlooking the living room, maybe 5-6' wide. Well it got framed in and then we started debating if we really wanted that. And our builder and HVAC guy were saying it looked nice, but was going to cause problems with heating and cooling. We considered walling it off, but as a compromise, we instead walled it off but left a semi large window in that wall with a wooden door that can be opened and closed for whatever conditions dictate. So, long story short, near the top of that living room cathedral ceiling, we have a wooden door that we can open to allow heat into the second floor.

_First_Floor_2022_07_24.jpg

Second floor:

The little yellow star again indicates where that door to the first floor is located. Dead space just means no floor space. All the dead space to the west of bed #2 and bed #3 is unheated area under roof, some of which is set up for storage, along with the area north of the "lounge" area. The area above the living room is the exception.

_Second_Floor_2022_07_24.jpg

Here's a pic of the chase from the outside:

20221027_182355.jpg

And here's a pic of that small window/door on the second floor that looks down into the living room:

20221210_145459.jpg
 
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Something else, you mentioned an outside air connection for combustion air; I keep asking stove people about this, and they act like it's an option but not necessary. Today I had someone tell me it's a bad idea, that it can lead to over-firing. Interested in hearing more about this, as I just assumed it would be preferred to use outside air for combustion rather than using your heated air from inside. Not to mention new houses get sealed up pretty tight these days, figured that might be another reason to get my combustion air from outside?

Thanks
 
In modern construction with an HRV or ERV (Heat recovery ventilation or Energy recovery ventilation) I think an outside air kit (OAK) is a really good idea as you won't be feeding conditioned interior air to the firebox.

I am confident HRV/ERV systems are easier to balance today than they were even a few years ago, but feeding conditioned interior air to the firebox of the woodstove for the life of the structure is ultimately wasteful. You will need some sort of mitigation plan to deal with likely condensation on the exterior of the cold intake air piping. Once that small problem is solved the wood stove will be on its own air circuit separate from the HRV/ERV managing interior air.

I cannot imagine a situation on an OAK where a woodstove is more likely to overfire than it would be drawing interior living space air for combustion. You do want to be careful the outside connector for the OAK is lower than the firebox floor, and have some awareness of prevailing winds at your location. It is possible for woodstoves to run in reverse on OAK setups, that is drawing combustion air down the chimney and expelling smoke out the OAK, this situation is bad, but fairly easy to predict and mitigate if you are familiar with your site.

If your target for air sealing is pretty tight, say less than 3.0 air exchanges per hour at 50 Pascals, you will want a 'loading' switch near the wood stove so you can shut down the HRV/ERV system (briefly and temporarily) while the loading door to the woodstove is open.
 
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In modern construction with an HRV or ERV (Heat recovery ventilation or Energy recovery ventilation) I think an outside air kit (OAK) is a really good idea as you won't be feeding conditioned interior air to the firebox.

I am confident HRV/ERV systems are easier to balance today than they were even a few years ago, but feeding conditioned interior air to the firebox of the woodstove for the life of the structure is ultimately wasteful. You will need some sort of mitigation plan to deal with likely condensation on the exterior of the cold intake air piping. Once that small problem is solved the wood stove will be on its own air circuit separate from the HRV/ERV managing interior air.

I cannot imagine a situation on an OAK where a woodstove is more likely to overfire than it would be drawing interior living space air for combustion. You do want to be careful the outside connector for the OAK is lower than the firebox floor, and have some awareness of prevailing winds at your location. It is possible for woodstoves to run in reverse on OAK setups, that is drawing combustion air down the chimney and expelling smoke out the OAK, this situation is bad, but fairly easy to predict and mitigate if you are familiar with your site.

If your target for air sealing is pretty tight, say less than 3.0 air exchanges per hour at 50 Pascals, you will want a 'loading' switch near the wood stove so you can shut down the HRV/ERV system (briefly and temporarily) while the loading door to the woodstove is open.
Can you explain why feeding conditioned air to the firebox would be wasteful?
 
Can you explain why feeding conditioned air to the firebox would be wasteful?
Yeah, I woke up in the middle of the night wanting to retract/modify what I had said above.

On the plus side, if you run an OAK you are sucking outside air directly into the firebox without putting any load on the HVAC system. But, you are counting on the HVAC system to manage all of your inevitable smoke rollout into the home .

If you allow the stove to draw conditioned household air into the firebox, you have some investment in heating or humidifying that air before it goes into the stove.

Over a reasonable 20 year service life for the stove, at an average of about 4 cords per year, 80 cords burnt is a lot of conditioned air to send up the chimney, or a fair dinkum of smoke rollout into the home to manage.

80 cords of wood will require, lemme google that for myself,

On this .pdf, slide 11, I see, again, that efficiently burning 1 pound of wood requires 10-12 pounds of air: https://is.muni.cz/el/1423/podzim2013/MEB423/um/Wood_Lesson_02.pdf

So how big is one pound of air (at standard temperature and pressure)? One pound of air at standard temperature and pressure occupies about 13 cubic feet. https://math.answers.com/Q/How_many_cubic_feet_of_air_are_in_one_pound_of_air

So lets be real. My house is two stories, 30x40 feet footprint, 8 foot ceilings. I got 1200sqft upstairs, and 1200 sqft downstairs. x8 foot ceiling height, 1200 sqft x 8 foot ceiling height x2 floors, 19,200 cubic feet, call it 20k cubic feet of interior air.

20,000 cubic feet of air, / 13 cuft feet per pound, my house has about 1538 pounds of air in it.

I need, call it eleven pounds of air per pound of wood, I have enough air in my house to burn (1538/11) 139 pounds of wood.

My stove has a 3.0 cuft fireplace and typically holds 30-50 pounds of fuel per load.

Essentially every three times I fill and I fire the stove I am committed to turning over 'all' the air in the house and replacing it with new (cold, wintertime) outside air that needs to be heated to whatever my target interior temperature is.

The longer you are going to stay in the house, the more important it is to choose your poison wisely.

I do specifically want to retract my statement about 3 airchanges per hour. If you are trying to build a "tight efficient" house, or modify an existing leaky house into a tight efficient home, you should consider an OAK, but site conditions like stove placement in the house , house placement on the topography, and in the local prevailing winds are going to be fundamental considerations.

All better now?
 
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The chase is convenient, but the house layout is not great for wood heating. The master br and bath will get the short end of the stick with little wood heat from either stove. It would be better to have the basement stove underneath that end of the house. One way around this would be to put a wood furnace or a ductable, EPA ZC fireplace in the basement so that heat could be ducted to the opposite end. There are wood furnaces that have a ceramic glass door so that the fireview is still there. Several good EPA fireplaces can be ducted to deliver heat to a distant room or area.
 
The chase is convenient, but the house layout is not great for wood heating. The master br and bath will get the short end of the stick with little wood heat from either stove. It would be better to have the basement stove underneath that end of the house. One way around this would be to put a wood furnace or a ductable, EPA ZC fireplace in the basement so that heat could be ducted to the opposite end. There are wood furnaces that have a ceramic glass door so that the fireview is still there. Several good EPA fireplaces can be ducted to deliver heat to a distant room or area.

Yep, I wish I'd have planned for a wood stove on the opposite side of the house as well, although this house is turning out to be expensive enough as it is. But when the house was being drawn up, I don't think we were even considering two wood stoves at the time. It wasn't until much later that we thought it would be worth putting a wood stove in the basement and we could get two vent pipes up the same chase.

Some interesting ideas there though. Although would a ZC ducted fireplace require the blower be operational to get anything out of it? A big part of our goal is to be able to provide heat to the house when the power is out too.

So assuming we stick with the plan as is, you'd say a Princess would be an appropriate size in the basement? King would be too much?

Any thoughts on how big to go in the living room? I was thinking maybe I'd add up the living room, den, kitchen/dining area, and front hallway, which comes out to about 1000ft². And then maybe add in some for the upstairs; no idea how much to add up there, but let's say the top landing and hallway which is about 260ft². So maybe shoot for a stove rated for around 1500ft²?
 
Yep, I wish I'd have planned for a wood stove on the opposite side of the house as well, although this house is turning out to be expensive enough as it is. But when the house was being drawn up, I don't think we were even considering two wood stoves at the time. It wasn't until much later that we thought it would be worth putting a wood stove in the basement and we could get two vent pipes up the same chase.

Some interesting ideas there though. Although would a ZC ducted fireplace require the blower be operational to get anything out of it? A big part of our goal is to be able to provide heat to the house when the power is out too.

So assuming we stick with the plan as is, you'd say a Princess would be an appropriate size in the basement? King would be too much?

Any thoughts on how big to go in the living room? I was thinking maybe I'd add up the living room, den, kitchen/dining area, and front hallway, which comes out to about 1000ft². And then maybe add in some for the upstairs; no idea how much to add up there, but let's say the top landing and hallway which is about 260ft². So maybe shoot for a stove rated for around 1500ft²?
Some ZC fireplaces heat well with natural convection. It could be ducted so that it fed the LR with one duct by convection alone.

The King would also work. It's mainly a bigger gas tank and an 8" flue instead of 6". It can still go low and slow if a black glass is ok when running that way.

The upstairs stove can be in the medium size range, 2-2.5 cu ft. Heating area ratings are ambiguous. They have to cover a broad range. This is because a stove can be in so many different environments, from a leaky house in a cold climate to a tight house in a mild climate.

Just spitballing here, but it looks like a basement stove could have the chimney go up through the BR1 closet and into the dead space on the 2nd floor.
 
Any thoughts on the Lopi Endeavor or Evergreen for the living room stove?

Saw an Endeavor at a local stove place recently. Liked the look, and liked the feel a lot. Felt very solid. Liked the design of the handle and the door, and the depth of the fire box. Liked the stepped design on top.
 
I assume you have forced air heating and cooling. Why not a wood furnace in the basement hooked into the ductwork, and a nice stove in the living room for ambiance?
 
Yep, forced air.

While the basement is pretty much utilitarian right now and for the foreseeable future, that could change someday. Also I assume for that to be effective you'd need power? I'd like something that can provide some significant heat if need be with no power.
 
Yep, forced air.

While the basement is pretty much utilitarian right now and for the foreseeable future, that could change someday. Also I assume for that to be effective you'd need power? I'd like something that can provide some significant heat if need be with no power.
Yes, 120V for the blower and inducer. But they can run at a low setting on natural draft. Even a UPS could run it for the length of time power is typically out before you get a generator going, and you' have the stove upstairs. Just something to consider.
 
Any thoughts on the Lopi Endeavor or Evergreen for the living room stove?

Saw an Endeavor at a local stove place recently. Liked the look, and liked the feel a lot. Felt very solid. Liked the design of the handle and the door, and the depth of the fire box. Liked the stepped design on top.
The Endeavor is a classic workhorse with a nice square firebox that can load N/S or E/W. The Evergreen is a new, clean-burning design. It has a shallower and slightly smaller firebox. It qualifies for the 30% tax credit.
 
The Endeavor is a classic workhorse with a nice square firebox that can load N/S or E/W. The Evergreen is a new, clean-burning design. It has a shallower and slightly smaller firebox. It qualifies for the 30% tax credit.

Thanks. Searching through some other threads on the Endeavor, sounds like it may get added to the tax credit list for 2023?

I was looking at a Lopi brochure a little earlier here and I think it said something about all stoves in the brochure being EPA-rated stoves, and the Endeavor was in there; does being "EPA-rated" means it qualifies for the tax credit?
 
Any residential woodstove sold must be EPA rated, but not all qualify for the credit. In order to qualify for the tax credit the stove must meet or exceed an arbitrary 75% HHV in EPA testing. There is a sticky thread covering this. Note that the credit changed in 2023, it is now 30% but with a cap of $2000.
 
I have to run two stoves when it’s cold I anwant a warm basement. It’s kinda a pain. If I had a choice I would do anything within reason to choose a single wood burner. That said I probably burn a lot less wood only heating the basement when it’s really cold and we will spend time down there. It will get a load and a half today. Possibly tomorrow too. Hasn’t been lit in over a week.
 
Yeah, I've had the thought that running two stoves simultaneously could be a bit of a pain. That's partly why I'm interested in the Princess for the basement. I want something down there that can heat that area and really give the house a leg-up on heating, but also something with a long burn time to reduce time spent tending to it.
 
Any residential woodstove sold must be EPA rated, but not all qualify for the credit. In order to qualify for the tax credit the stove must meet or exceed an arbitrary 75% HHV in EPA testing. There is a sticky thread covering this. Note that the credit changed in 2023, it is now 30% but with a cap of $2000.

That's good to know, thanks.
 
Ended up ordering a Lopi Endeavor for the living room.

Kind of on the fence about the Princess in the basement now. Still want a basement stove, just debating other options. Perhaps a Lopi Liberty?
 
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Ended up ordering a Lopi Endeavor for the living room.

Kind of on the fence about the Princess in the basement now. Still want a basement stove, just debating other options. Perhaps a Lopi Liberty?
How much will the basement stove burn?
 
How much will the basement stove burn?

When it's cold, probably quite a bit. The basement, at least right now, is a very large wide open area. I figure heating that area with wood should save me a fair bit on heating.

The wife and I work from home, so we'll be there to tend the stoves a lot.

Now like a winter like this, I'm not sure. It's been extremely mild with few really cold snaps.