Scared of getting too many BTU’s

[MN Mike]

Hello All,

Mike here and I’m a newbie to this forum, but I’ve been searching a bunch on here today. I live in the Twin Cities of Minnesota, but was born in Wisconsin and am an avid Packer fan, but that’s beside the point. I’m a mechanical engineer and I love the idea of wood as an secondary heat source. I am starting to get quotes for a wood insert for a masonry fireplace which currently only has a screen and no glass. It has large river rock in the facade, and should work to soak up heat well. My family has land in Wisconsin that I can utilize for wood supply, and I just bought a Stihl MS 271 with 18” bar. I think I’ve finally got blessing from my wife to use some “found money” from childhood savings bonds. I currently am burning oak in an open fireplace from last year that is stacked and split under a roof with vented sides.

My home (see photo) : 2 story with flat roof, vaulted living room, 2700 square ft above ground with another 1300 in the basement, which is half finished and has a few heating ducts. There’s a second fireplace down there, but I am not looking to change the heating down there right now. The main floor fireplace is nearly in the center of the house, which I believe will help with trying to heat as much of the house as possible from the main floor insert. We have an awesome 2 stage gas furnace, with duct work that was set up for zoning when the house was built in 1971. It doesn’t have automatic zoning anymore, but there are still manual dampers where the ducts exit the plenum, so I can control where the air goes.

On to the real question. I’m trying to determine the appropriate BTU output that should be my upper limit. I don’t want to have the situation where I always have to choke the fire off and produce undesirable emissions and burn efficiency. I have found another user heating 3,000 sq ft with the Kozy Heat Z42 CD, which has a quoted rating of 60,000 BTU. That’s the only similar post I’ve found so far, but would be happy to read further if others know of posts that would help. I did read the “welcome” info with considerations for wood heat.

See the attached pano photo showing my main floor. Excuse the mess, I’ve got 3 little kids, and barely found time to write this post. You can see the location of the existing masonry fireplace, as well as the vaulted family room and stair to 2nd level where there are 4 bedrooms. 3 of the bedrooms are above the kitchen and fireplace, the master is beside the vaulted space. I doubt that the fireplace will heat the master, but I’d be glad if it did. The kids beds though should get heat rising through the floors right? Or would the heat go up the vaulted space and down the hall instead? I’m also wondering if the heat will wrap around to the kitchen, adjacent to the fireplace?

Bottom line: how do I make sure I don’t overheat the living space with the insert, but still maximize the heat to get as much of my 3,000 sq ft heated as possible? My fireplace box opening today is 22” high which is already a limiting factor. You can see large windows in the photo, but they don’t open, are double panes, and actually don’t lose much heat. I had an energy consultant estimate that the flat roof attic has an insulation of about R40-45. I follow my house temps during the daytime via a smart thermostat and with outdoor temps in the single digits, the house only drops to about the mid to low 60’s by the afternoon, from 68 when we wake up for work.

I’m sure I’ve missed some valuable info, so let me know.

Mike

 

[Woody Stover]

I don't think you have to worry about roasting yourself out, especially with an insert..that's a big space with plenty of places for heat to go. It does sound well-insulated though..

 

[xman23]

How well you heat the house has all to do on insulation, windows etc. The stove location is a factor to how even the heat will be, or how much you will overheat the stove room. As temps drop it get harder to keep rooms further from the stove warm.

Your stove location is your existing chimney and the insulation is what it is. Both may not be ideal.

 

[blacktail]

With a big house in Minnesota, having too much heat shouldn't be a concern.

 

[bholler]

I would just like to add hauling firewood over state lines is probably not legal for very good reasons.

 

[venator260]

I can't think that too much heat will be a problem, even with the largest of inserts on the market. You'll get to learn your house as I am currently. If your house gets too hot, let the fire go out.

For myself, I think that some would consider my insert to be slightly over sized (one dealer did) but I wanted something that will heat the house full time. When I don't need so much heat, I space out reloads or simply let the fire go out. As you're learning the stove, I would let the house cool off a bit before you light a fire, and don't be afraid to open windows.

 

[begreen]

Bottom line: how do I make sure I don’t overheat the living space with the insert, but still maximize the heat to get as much of my 3,000 sq ft heated as possible? My fireplace box opening today is 22” high which is already a limiting factor. You can see large windows in the photo, but they don’t open, are double panes, and actually don’t lose much heat. I had an energy consultant estimate that the flat roof attic has an insulation of about R40-45. I follow my house temps during the daytime via a smart thermostat and with outdoor temps in the single digits, the house only drops to about the mid to low 60’s by the afternoon, from 68 when we wake up for work.

Go as large as will fit. You won't overheat this area. The open floorplan will help a lot. Don't pay too much attention to peak btu output. You are not going to run the stove in that range. The EPA output is more conservative. Also, you control the amount of heat by the size of the fuel charge and air supplied to the fire. The upstairs may get warmer due to the high ceilings, but a ceiling fan or two can help circulate some of that hot air better.

 

[ACDKali]

I would just like to add hauling firewood over state lines is probably not legal for very good reasons.

Yes check your local regulations. In Wisconsin your not suppose to move wood from county to county. It’s to stop the spread of all the bugs.

 

[KindredSpiritzz]

In Wisconsin your not suppose to move wood from county to county. It’s to stop the spread of all the bugs.

last i read, wood could be moved from infected county to infected county and pretty much the whole state is infected now anyways. Gypsy moth and emerald ash borer are the concerns. I truck mine 200 miles, never had an issue or been stopped.

 

[MN Mike]

Thanks for the feedback everyone. Was waiting to respond. I’m enjoying the thought of maximizing insert size, which at this point in my research looks like it means a bay style. Thanks for suggestion to compare based on EPA BTU’s. Not all mfgers list the EPA numbers in their specs, but I did find the EPA numbers spreadsheet on the EPA site.

Are the bay style ones, which extend onto the hearth ~10 inches, able to throw more of the heat into the room, compared to flush mount styles? Seems intuitive to me, but not sure.

 

[jetsam]

Thanks for the feedback everyone. Was waiting to respond. I’m enjoying the thought of maximizing insert size, which at this point in my research looks like it means a bay style. Thanks for suggestion to compare based on EPA BTU’s. Not all mfgers list the EPA numbers in their specs, but I did find the EPA numbers spreadsheet on the EPA site.

Are the bay style ones, which extend onto the hearth ~10 inches, able to throw more of the heat into the room, compared to flush mount styles? Seems intuitive to me, but not sure.

The more it sticks out, the better. Consider a freestanding stove if modifying the hearth is possible.

 

[ACDKali]

Thanks for the feedback everyone. Was waiting to respond. I’m enjoying the thought of maximizing insert size, which at this point in my research looks like it means a bay style. Thanks for suggestion to compare based on EPA BTU’s. Not all mfgers list the EPA numbers in their specs, but I did find the EPA numbers spreadsheet on the EPA site.

Are the bay style ones, which extend onto the hearth ~10 inches, able to throw more of the heat into the room, compared to flush mount styles? Seems intuitive to me, but not sure.

Think as a Bay in a positive note. I prefer bays strictly because you get them to stick into the room and gain that extra radiant heat, along with log size. A lot of the older units are bays, Regency, Pacific Energy, Iron Strike etc. All the hearth changes per unit, refer to the spec sheet or manual. If you have to extend the hearth there are many short term fixes for that.

I personally like the Pacific Energy, mostly because they have a lifetime warranty on their baffle, plus its easy to pop and and sweep. The 2 units e have in our showroom, the glass stays extremely clean, please note its a showroom so we pay close detail to moisture content of the wood, so we have awesome burns. Also their blowers have a 2 year warranty for is pretty slick. Regency makes a good product, I just don't like tubes as much, but that's me getting picky. No matter what, there is some great products out there. But like i said, the bay's have a better pay off on the long term scale of coming into the room.

J.

 

[bfitz3]

Please don’t move firewood. The beech in my avatar had beech bark disease and my woods are on the fast track to being beech free. Woodland pests/blight are a real issue that we all need to fight, even if passively not contributing to their spreading. Really... just don’t.

 

[bholler]

last i read, wood could be moved from infected county to infected county and pretty much the whole state is infected now anyways. Gypsy moth and emerald ash borer are the concerns. I truck mine 200 miles, never had an issue or been stopped.

Those are the main concerns now but there are many other bugs that have not spread far yet. And you have no clue what is on that wood

 

[bfitz3]

last i read, wood could be moved from infected county to infected county and pretty much the whole state is infected now anyways. Gypsy moth and emerald ash borer are the concerns. I truck mine 200 miles, never had an issue or been stopped.

...there’s never an issue until there’s an issue. Don’t be the guy that causes it.

 

[allan5oh]

Yup we now have EAB in Winnipeg as of a few months ago. My entire neighborhood is ash!

I don’t want to have the situation where I always have to choke the fire off and produce undesirable emissions and burn efficiency.

With a modern stove the opposite is true. They're generally a bit more efficient and cleaner as you choke off primary air. These aren't your grandpas stoves any more! But they are more sensitive to draft (flue length) and outside air kits are always recommended.

Bottom line: how do I make sure I don’t overheat the living space with the insert, but still maximize the heat to get as much of my 3,000 sq ft heated as possible?

Again modern stoves with fans are better at this. More primary air means a bright fire that heats more of the local room. As you choke it off you get slower darker red/blue/purple flames that don't throw off as much infrared. This is the difference between convective and radiant heat. What you want is convective heat and modern stoves are very good at it. Catalytic stoves can be turned down even further than non-cat stoves. At this point you might even see NO flames in the firebox but a good amount of convective heat.

Properly placed ceiling fans around the house will help as well.

Take a look at Blaze King inserts:

http://blazeking.com/EN/wood-inserts.html

Well known company. But beware their inserts do not perform as well as their freestanding stoves. But they're the best designed catalytic stoves on the market and feature a mechanical thermostat. Have a look at their freestanding stove brochures too, bit more info in them. Judging by your picture and location I doubt you will ever throw too much heat. The blaze kings can be turned down to about 13k btus.

 

[jetsam]

But beware their inserts do not perform as well as their freestanding stoves. But they're the best designed catalytic stoves on the market

To be fair, nobody else's inserts perform as well as their their freestanders either. Freestanding stoves have the large advantage of having their entire outer surface inside of the room- that is pretty tough for a similarly designed fireplace insert to compete with.

BK's Princess insert does stick out into the room a little, which is better than being a flush insert.

Absolutely go for the BK if you want maximum output controllability. There are a bunch of good inserts out there, though.

 

[firefighterjake]

Yup we now have EAB in Winnipeg as of a few months ago. My entire neighborhood is ash!



With a modern stove the opposite is true. They're generally a bit more efficient and cleaner as you choke off primary air. These aren't your grandpas stoves any more! But they are more sensitive to draft (flue length) and outside air kits are always recommended. I'm not sure if outside air kits are always recommended . . . I mean they certainly cannot hurt, especially in a well insulated and sealed home, but to say they are always recommended?



Again modern stoves with fans are better at this. More primary air means a bright fire that heats more of the local room. As you choke it off you get slower darker red/blue/purple flames that don't throw off as much infrared. This is the difference between convective and radiant heat. What you want is convective heat and modern stoves are very good at it. Catalytic stoves can be turned down even further than non-cat stoves. At this point you might even see NO flames in the firebox but a good amount of convective heat. Some dubious statements here . . . more primary air does not necessarily equate to a brighter fire (I can get a pretty bright fire when the secondaries Portal to Hell has opened up in my stove). Furthermore I'm not really sure what is stated about the color and infrared light waves and convective heat is accurate. I mean to say I can also get the blue flames with my stove -- a modern stove -- and it is without a doubt a radiant type of stove.

Properly placed ceiling fans around the house will help as well.

Take a look at Blaze King inserts:

http://blazeking.com/EN/wood-inserts.html

Well known company. But beware their inserts do not perform as well as their freestanding stoves. But they're the best designed catalytic stoves on the market and feature a mechanical thermostat. Have a look at their freestanding stove brochures too, bit more info in them. Judging by your picture and location I doubt you will ever throw too much heat. The blaze kings can be turned down to about 13k btus. While Blaze Kings get a lot of love here for good reason, I am not sure if one could say they are the best designed cat stoves on the market . . . fans of Woodstock might disagree . . . and that I suspect would be the basis of a rather long post on the pros and cons of BK vs. Woodstock.

 

[jetsam]

While Blaze Kings get a lot of love here for good reason, I am not sure if one could say they are the best designed cat stoves on the market . . . fans of Woodstock might disagree . . . and that I suspect would be the basis of a rather long post on the pros and cons of BK vs. Woodstock.

The good news is that you can just search the forum for that topic if you want to see it, it's been gone over pretty thoroughly already.

 

[DuaeGuttae]

There are some good BTU loss calculators out there that you might want to consider. Use one that considers volume and shape of your space. Also look at your utility bills to see how much gas you’re currently using.

I’ve been considering wood stoves, but I live in a land of little winter. The house is about 3, 000 sq. ft. with high ceilings. The layout is such that heat wouldn’t move everywhere. I definitely worry about too many BTU’s. Your description and climate would not give me that same concern. Granted your insulation is much better than ours, but I really don’t think you’re in too much danger of overheating your space. Use one of those BTU calculators and find out a bit more.

 

[jotul8e2]

Some things to consider;

In your climate a house your size will require something in the four to five cord range per year. This is a significant amount of work.

Moving that much firewood that far will be a significant expense, even if legal. See https://www.mda.state.mn.us/plants/pestmanagement/~/media/Files/plants/eab/firewoodalert.ashx .

The heat loss through those windows is considerable. You have r-40 in the ceiling for a reason. The glass is maybe r-3 at best. Cellular shades will dramatically reduce the heat loss and provide a tremendous gain in living comfort.

The heat from a wood burning stove does not move easily through floors. It can move well up a stairway if it is large enough.

A cat stove in the 3.5 cu. ft. range would provide the btus you need while allowing you to dial it back on warmer days.

 

[MN Mike]

Jotul8e2 - when you say cat stoves, are you saying these produce more heat than those with secondary burn tubes, such as on the QuadraFire 5100i? Most, maybe all, of the inserts I've been looking at do not have the cats but rather the secondary burn. My understanding is that the secondary tubes are a more efficient way of burning the unburned gas from the primary burn, as compared to a cat. Or are you saying their are products with secondary burn PLUS cats to get additional burn from the cat AFTER the secondary.

I've reviewed the info from Quadra Fire, and they claim to have 4 zones of burning.

 

[jotul8e2]

Cat stoves generally are a bit more efficient than non-cat stoves, true. But non-cats (such as both of my stoves) produce most of their heat early in the burn cycle and then drop off dramatically for the last 2/3 of the cycle. A cat stove will provide more nearly even heat over a much longer time. This makes a big difference when you are trying to heat remote rooms or upstairs spaces.

 

[MN Mike]

"Early in the burn cycle", meaning at a hotter temp?

 

[MN Mike]

I'm comparing two units that extend into the room, 1) the Blaze King Ashford 25 (the Princess is a tad too tall for my firebox) and it is a catalytic unit and 2) the Quadra Burn 5100i which is non-catalytic. I'm checking the EPA database for Heat Output, and it appears that the non-cat has far greater heat output.

QB 5100i (3.0 cu ft capacity) -49,900 BTU, Ashford 25 (2.3 cu ft capacity) - 26,290 BTU.

Am I missing something?

Here's the list
https://www.epa.gov/sites/production/files/2017-08/usepa-certified-wood-heater-list.xlsx