A nuanced question about Square Footage ratings

[joefrompa]

Hi all,

I'm about to purchase a Lopi Republic 1750 insert for my ~2300 square foot colonial home. It's rated to 1900 square feet in my Zone, and after closing a few rooms I expect to be right around 1900-2000 square feet.

Now I realize that this is so dependant upon exposure, insulation, air-loss, and how much hot air I expel myself. All well and good.

My question is really: when you put a stove in a home that's bigger than the stove can heat, which of the following happens (assuming ALOT of good airflow away from the stove and about 20 degree ambient temp with little wind):

1. The stove heats the immediate room to 80 degrees, the "nearby" rooms to 75 degrees, and everywhere else is 60 degrees

2. The stove heats the immediate room to ~75 degrees and the rest of the house to 60-65 degrees, with cold spots at the far corners.

3. The stove heats the closest 1000 square feet very well and then keeps the other 1000 around 50-55 degrees


I'm ASSUMING it's #1, where you get a zoned heating effect where the immediate living space is toasty, nearby feels fine, and the rest of the house is cold. Is it more of a distinct zone than that?

What I'm trying to ascertain is this: I'm probably going to expect too much out of this stove in terms of heating the entire house, so I'm prepared to accept some cold zones. But: will I simlpy need to run my central oil furnace to heat up the house another 3 degrees, or will I need some sort of zoned heat (i.e. an electric-oil radiator) because most of the house will be fine but there will be 2-3 rooms that just won't get warm.

Hope that made sense.

Thanks all,

Joe

 

[billb3]

I'd assume #1 and be happy with #2 or #3.

I've seen a room with a stove in it cool another 10 degrees by opening a door to the next room by putting a double door in and opening them both when it was cold.

Really tough to make any assumptions even with an identical house sometimes.

 

[Slow1]

The answer to this is entirely dependent on airflow in the house and other rooms. If the colder rooms pool air then they will remain colder. If you can get the cold air back to the stove then it can be warmed up and warmer air can move in to warm that room/area.

The problem situation is #4 that you did not list and seems to be common - the user of the stove tries hard to get more heat from the stove and ends up over firing it trying to push it beyond its capabilities. This or the user simply decides the stove isn't any good because it "can't heat things" even though the stove is doing a good job as it was designed to do but just can't keep up.

We have a very open floor plan home with a loft and are heating it with a stove rated for up to 1600 sq ft (heating about 24-2600 sqft). It works for us for the most part. We do have two rooms at the end of the house (first floor/stove level) that stay about 5-10 degrees colder than rest of the house (especially when it is very cold outside). These happen to sit on top of the garage so I think that is contributing quite a bit to the lowered temp. As a whole the house temps stay fairly close to the same throughout - about 5* differential (other than those colder rooms) which surprised me to be honest - I expected the second floor to be much warmer. We rely almost completely on natural convection currents to move the heat around. I think we just happened to be very lucky that our home and stove placement worked out so well - I certainly didn't design it this way. Our "stove room" as it is doesn't have any doors and really is more of an open hall area (if you can call 10' wide space a hall) that is open on both ends with a missing corner where the kitchen is.

 

[firefighterjake]

As Slow mentions the air flow in the home and the lay out really play a key factor here . . . and as Bill said it is tough to make a call.

I can tell you that in general the answer to your question is #1 . . . at least in my case . . . providing I am using a fan to blow the cool air towards the stove to set up an artificial wind current. As you have guesed it is almost always -- if not always -- warmest in the room where the stove and fire are located . . . and as you get further away the rest of the house is a bit cooler . . . but using the fan there isn't much of a difference (in my case) -- less than 5 degrees . . . and I would say that most all of the rooms are comfortable . . . comfortable in terms of 64 degrees or higher when the stove is running.

My main surprise was finding that the entire upstairs was not over-heated . . . and in fact it is rather comfortable . . . not too hot and not too cool. My downstairs bedroom is perhaps the coolest room in the house -- but it isn't frigidly cool and my wife and I tend to like the bedroom a bit on the cool side for sleeping.

I do have one room with an electric space heater -- ironically enough it's my boiler room/bathroom . . . I may not even need the space heater there, but I have it there to make sure my oil lines and water pipes don't get anywhere near freezing . . . this is also set up on a thermostat.

As for the whole house . . . three zones and I leave the thermostat at 60 degrees F . . . usually the oil boiler will not kick on unless we've had some sub zero weather and it's at the tail end of an overnight fire.

 

[galega]

It's rated to 1900 square feet in my Zone

Hi Joe - just curious, where did you find a zone-based rating for the stove? Is that info from the manufacturer?

I'm curious to hear what the more experienced guys on the board have to say, but as others have already commented I think it's going to really depend on the layout of your house. Growing up we had a wood/coal stove in the living room. The stairs to the upper floor were in the living room, and if we left our bedrooms doors open at night the stove did a good job of heating the upstairs rooms too (although our hallway was relatively compact).

The dining room, which was adjacent to the living room (and just past the stairs) was much cooler, and the kitchen (next room) was downright cold. That was just the way the air/heat flowed in our house.

If you drew up a rough sketch of the layout of your house it would probably help others answer your question with more accuracy.

 

[joefrompa]

Thanks Slow.

I have an open floor plan on the first floor (roughly 1000 square feet), 8 foot ceilings, and great air-sealing through the entire first floor. I have a ceiling fan directly above where the fireplace is, I'll have a powerful floor fan pushing it out of the ~400 square foot room it's in, and then I have an open foyer with a ceiling fan in it pushing the air upstairs.

I have no lofts, and 8 foot ceilings throughout except for that open foyer (which should help heat the bedrooms).

If your 1600 square foot rated stove is working for 2200-2400 square feet to keep it liveable, and you are using convection....well, that makes me feel better.

Are you using 5-year aged oak?

Joe

 

[Slow1]

Oh - and another tidbit in case you didn't already know this. The "square footage" heat rating on most stoves is likely only really of use for comparing models from the same line/manufacturer. I would take that with a major grain of salt so to speak. There are far too many variables to consider to be able to say a given stove will 'heat' a home of any given size. The subjectivity of what does "heat" mean is a good starting point - I am happy with 63-65 while others would go crazy if their home fell below 70.

Then of course not all 2300 sqft homes require the same amount of heat to maintain x*f inside when it is y*f outside - the "heat load" will be different depending on the design of the home and how well insulated and airsealed it is. How much solar gain do you get? How shaded from sun by trees, protected from wind etc etc etc...

The point I'm trying to make here is that even if manufactures wanted to give you a perfect answer it would be next to impossible to come up with even a close estimate (+/- 10%) of how much space a stove can heat that would fit all homes - even in a given climate. Then add into this the fact that each manufacture seems to use a different calculation you can't even necessarily compare stoves using this number to see which one is going to work better for you.

So - this contributes to the recommendation by many here to get a larger stove than you think you need. If you end up getting a stove rated smaller than you home is you will know ahead of time that you shouldn't expect to heat exclusively with it. That is ok - but then again you just might be surprised too. The problem may be if you are so close to being able to do it all with wood but not quite that it is frustrating. Whether that is a problem for you or not depends on your personality I suppose...

 

[vvvv]

prevailing wind in winter comes from N which effects a N-S flow of air thru the house= something to consider

 

[Slow1]

I have an open floor plan on the first floor (roughly 1000 square feet), 8 foot ceilings, and great air-sealing through the entire first floor. I have a ceiling fan directly above where the fireplace is, I'll have a powerful floor fan pushing it out of the ~400 square foot room it's in, and then I have an open foyer with a ceiling fan in it pushing the air upstairs.
Joe

That sounds quite good for mixing/spreading the hot air around. If I'm understanding your plan correctly you may want to consider reversing things - push the cold air to the stove instead of trying to move hot air away. Others have said this works much better.

If your 1600 square foot rated stove is working for 2200-2400 square feet to keep it liveable, and you are using convection....well, that makes me feel better.
Joe

See my comment above - every mfgr has a different way of estimating sqft rating. I think that Woodstock has one of the more conservative estimates (perhaps to help reduce the returns on their 6 month money back guarantee?).

Are you using 5-year aged oak?

Joe

Ha! I wish I was. I'm struggling to get two years ahead. However I've managed to keep it to two year old wood for the most part although this year I'll have some 18month old poplar, pine, and black birch mixed in there as well as some 2+ year old oak and apple.

 

[joefrompa]

It's rated to 1900 square feet in my Zone

Hi Joe - just curious, where did you find a zone-based rating for the stove? Is that info from the manufacturer?

I'm curious to hear what the more experienced guys on the board have to say, but as others have already commented I think it's going to really depend on the layout of your house. Growing up we had a wood/coal stove in the living room. The stairs to the upper floor were in the living room, and if we left our bedrooms doors open at night the stove did a good job of heating the upstairs rooms too (although our hallway was relatively compact).

The dining room, which was adjacent to the living room (and just past the stairs) was much cooler, and the kitchen (next room) was downright cold. That was just the way the air/heat flowed in our house.

If you drew up a rough sketch of the layout of your house it would probably help others answer your question with more accuracy.

The 1900 square feet is from the manufacturer. It's based upon the stove itself and the location in the country. For my zone (SE PA), it says ~1900 square feet.

I'll try to draw something up.

 

[branchburner]

Sorry for this non-nuanced answer, but sq ft ratings are mostly bunk.

All the other variables, many mentioned above, make such ratings deceptive. The number to look for is firebox size, the cu ft rating of the stove. My not-so-nuanced scale of EPA stoves, probably also bunk:

1.0 - are you kidding?
1.5 - it's a start (= small stove)
2.0 - you could heat a tight/small house (= small side of medium stove)
2.5 - you could heat a house (= big side of medium stove)
3.0 - you could heat more house (big stove)
3.5 - you will heat the house (very big stove)
4.0 - hope it has a cat (or you have lots of windows)
4.5 - are you kidding?

 

[begreen]

I suspect that in the fall, early winter and spring it will do a fine job of heating the entire house. In the dead of winter, you mayy be feeding the fire a lot more fuel, giving it more air and running it 50-100 degrees warmer than during the shoulder seasons. Unless you can close off parts of the house, the heat is going to try and diffuse throughout the place. The stove area will still be the warmest, but the heat may migrate quickly to other areas. At least that is the way our house works with a similar floorplan. At some outside temperature point you will probably need to supplement with the oil heat. But that isn't a bad thing, especially if it's not until temps get in the single digits.

 

[joefrompa]

I'll toss in this:

In SE PA, a cold winter day is 20 degrees. 20-25 degrees we usually have for ~2 months a year. We usually only have a few weeks of down in the teens, and maybe 5 or less days when it's single digits. Aside from that, we get an additional 1.5 months of 25-40 degree days

I'm looking to keep the house warm with the stove only during the 20-45 degree days that blanket PA from mid-November through the end of March, assuming it's not too windy. I accept I'll need additional heating sources during those 15 degree days with 20mph winds.

I don't mind supplementing with oil heat, though my goal is to spend only $200 worth of oil this winter. Also, just curious: My fireplace is on the first floor. How cold should I expect the basement to get if there are no heat sources down there? Should I plan on getting something to give it a bit of heat???

Joe

 

[joefrompa]

1.5 - it's a start (= small stove)
2.0 - you could heat a tight/small house (= small side of medium stove)
2.5 - you could heat a house (= big side of medium stove)
3.0 - you could heat more house (big stove)
3.5 - you will heat the house (very big stove)

Lopi's largest insert is 2.9 cubic feet. The one I'm looking at is 2.2 cubic feet and supposedly very efficient and all that good stuff.

One interesting note: I ran a oil-furnace sizing calculator for my home and it said ~75,000 BTUs based upon 2-story colonial of 2300 square feet in my zip code. I'm sure there's alot of weird assumptions in there too.

Anywho, the Lopi unit I'm looking at is 72,400 BTUs (per Lopi, so who knows what they used there). Anyway, I thought that was interesting.

 

[begreen]

I'll toss in this:

In SE PA, a cold winter day is 20 degrees. 20-25 degrees we usually have for ~2 months a year. We usually only have a few weeks of down in the teens, and maybe 5 or less days when it's single digits. Aside from that, we get an additional 1.5 months of 25-40 degree days

I'm looking to keep the house warm with the stove only during the 20-45 degree days that blanket PA from mid-November through the end of March, assuming it's not too windy. I accept I'll need additional heating sources during those 15 degree days with 20mph winds.

I don't mind supplementing with oil heat, though my goal is to spend only $200 worth of oil this winter. Also, just curious: My fireplace is on the first floor. How cold should I expect the basement to get if there are no heat sources down there? Should I plan on getting something to give it a bit of heat???

Joe

Sounds like your expectations are realistic. Just be sure to burn only dry wood to get as much heat as possible from the stove.

The basement temps will vary with the design and how leak free it is. If it has a leaky sill or windows and exposed foundation, it may get close to freezing down there. If it is sealed tight and mostly underground, it may not get below 45 down there. Best thing to get is a remote thermometer. If you can get one with a temp alarm, that is even better. But based on the planned burning habits it sounds like the oil burner will be kicking in occasionally on really cold days. That may be all you need to keep things ok. If the HW heater doesn't have an insulation blanket on it, that might be a good thing to add too.

 

[joefrompa]

Sounds like your expectations are realistic. Just be sure to burn only dry wood to get as much heat as possible from the stove.

The basement temps will vary with the design and how leak free it is. If it has a leaky sill or windows and exposed foundation, it may get close to freezing down there. If it is sealed tight and mostly underground, it may not get below 45 down there. Best thing to get is a remote thermometer. If you can get one with a temp alarm, that is even better. But based on the planned burning habits it sounds like the oil burner will be kicking in occasionally on really cold days. That may be all you need to keep things ok. If the HW heater doesn't have an insulation blanket on it, that might be a good thing to add too.

Basement is 100% below ground with 2 small vent windows. Basement is 30 year old poured concrete, so it's very solid. A recent air-loss audit shows the windows to be air-tight; the only leak was from where the electrical wiring comes into the house. I'll be sealing that up.

I also have a turtle's tank down there and a little heating unit keeping the water at 75 degrees

The water heater is fully exposed....might not be a bad thing if I want to keep the basement a bit warmer though, right?