Stove Size and Flue Size 5K Sq Ft Multi-Story

[ShenKen]

Hi! I'm pretty new to the forum, although I have been reading some discussions for awhile. We are building a new house in central Virginia and would like to provide for a free standing wood stove in the basement. I grew up in a house that had a large wood-burning furnace and have wished for years to have a wood stove again.

My main question at the moment is what size chimney to put in, but of course the size of the stove plays into that.

The total square footage of the house is approximately 5,000 (basement 2,000 + main 2,000 + upstairs 1,000). Ceilings are 9 ft in the basement, and 8 ft main and upstairs.

We plan for the stove to sit in the basement family room, near an exterior wall. The chimney will be a straight run of Class A pipe up through the interior of the main floor and upstairs, then on up inside an insulated chase. Total chimney length: 25 ft +/-.

I was planning on an 8" ID chimney to make sure I'd have enough draft, and I have room for an 8"; but in talking with various people I have been cautioned that too LARGE a chimney can lead to reduced draft and creosote build-up.

But IF we would go with a 6" chimney and be wanting whole-house heat from the stove, could we expect to get it from a stove with a 6" collar?

Also, considering that the chimney pipe is mostly inside the insulated building envelope (meaning the chimney will stay warmer), will that help with creosote issues?

Any advice will be appreciated. I'm essentially a newbie since I haven't ever owned my own place with a wood stove.

 

[ShenKen]

I will add this but of info yet: the house will be pretty well insulated, with spray foam in the walls and rafters.

 

[begreen]

The main concern will be negative pressure in the basement. It would help to get outside air to the stove. Is this a daylight basement? Will the basement be insulated? Will there be an HRV or ERV system installed?

Most modern stoves with a few exceptions work on a 6" flue. Do you know what stove will go in? It sounds like the total flue system height will be closer to at least 30'. Draft strength may be an issue, but too strong, not too weak.

There is no reason to insulate the chase that encloses the chimney pipe as it passes through the floors. Some people add a grille, top and bottom of the chase to permit warm air from the chase to convect into the room. There will need to be a firestop at each floor.

 

[EbS-P]

how much wood do you want to burn a year? ie weekend, holidays, polar vortex or 24/7?

What is the layout of the basement? How will heat get upstairs?

As an owner of a house with 1200sq ft walk out basement and 2000 sq ft upstairs with a stove in each. The basement would be very hot if we wanted to heat the whole house from there.

Put the stove where YOU the person wanting and running the stove will spend most of your time. I’d compromise and get two value brand stoves (one for each level) over one big expensive basement stove.

 

[ShenKen]

Thanks for your response, begreen. In answer to your questions:

One end of the basement is daylight/walkout. I don't see a way to hide an outside air duct by going out the end at floor level. But if I went up, it could run behind a brick accent wall that we plan to have behind the stove. I believe going up with outside air supply can have its challenges though.

Basement is insulated. Precast concrete walls with foam insulation rated at R-22.

Probably no HRV or ERV. A dampered fresh air duct will connect to the central ductwork to provide passive makeup air for the kitchen exhaust. Under consideration is a small blower that would provide a constant low flow of air coming into the house.

I currently own an Englander 30-NC (bought new in 2016 and never used). It is rated for 2400 sq ft, but might it exceed that in a well-insulated home? It has a 6" flue collar. We plan to try this stove but I worry about potentially needing a larger stove with a larger flue size. On the other hand, we might be content to have it as supplemental heat along with the heat pump.

We do not plan to insulate the chase against inside walls, just outside.

 

[begreen]

Yes, I was thinking furnace when reading this.

 

[ShenKen]

how much wood do you want to burn a year? ie weekend, holidays, polar vortex or 24/7?

What is the layout of the basement? How will heat get upstairs?
...

I like to think we would heat entirely with wood but in reality I don't know if my time or energy will actually hold up to that.

I'll attach a floor plan of the basement. Warm air can radiate up through the floors (uninsulated) and also possibly up the U-shaped stairway(s).

Having two stoves is a new thought - I like it! But then we'd be looking at two chimneys, and I'd have to think over whether we have a good spot on the main floor for a stove...

 

[bholler]

Thanks for your response, begreen. In answer to your questions:

One end of the basement is daylight/walkout. I don't see a way to hide an outside air duct by going out the end at floor level. But if I went up, it could run behind a brick accent wall that we plan to have behind the stove. I believe going up with outside air supply can have its challenges though.

Basement is insulated. Precast concrete walls with foam insulation rated at R-22.

Probably no HRV or ERV. A dampered fresh air duct will connect to the central ductwork to provide passive makeup air for the kitchen exhaust. Under consideration is a small blower that would provide a constant low flow of air coming into the house.

I currently own an Englander 30-NC (bought new in 2016 and never used). It is rated for 2400 sq ft, but might it exceed that in a well-insulated home? It has a 6" flue collar. We plan to try this stove but I worry about potentially needing a larger stove with a larger flue size. On the other hand, we might be content to have it as supplemental heat along with the heat pump.

We do not plan to insulate the chase against inside walls, just outside.

You cannot run a fresh air intake above the stove

 

[EbS-P]

Having two stoves is a new thought - I like it! But then we'd be looking at two chimneys, and I'd have to think over whether we have a good spot on the main floor for a stove...

It’s nice till it’s not. Like trying to light/reload both with 15 minutes of each other.

Consider a whole home dehumidifier with fresh air intake. I may depend on what part of VA you are in. We are coastal NC love the whole house dehumidifier.

 

[ShenKen]

Say I'd go ahead and install a 8" chimney and later desire a smaller one. Would there be any feasible way to reduce it without completely replacing it? Theoretically it seems it would be safe to just slide a 6" stovepipe down inside the 8" but I'm not sure how it would be supported.

I feel like you'll be thinking I'm crazy for asking such a question, but you don't get answers if you don't ask!

Thanks for all the replies so far!

 

[kborndale]

The vast majority of modern stoves run on 6" flue so your probably best off running that. With a 25 ft chimney your problem will be the draft is too strong, not too weak.

 

[EbS-P]

Say I'd go ahead and install a 8" chimney and later desire a smaller one. Would there be any feasible way to reduce it without completely replacing it? Theoretically it seems it would be safe to just slide a 6" stovepipe down inside the 8" but I'm not sure how it would be supported.

I feel like you'll be thinking I'm crazy for asking such a question, but you don't get answers if you don't ask!

Thanks for all the replies so far!

Have you looked at the price difference between 6” and 8” double wall and class A?

 

[brenndatomu]

Sounds to me like a whole house wood furnace would be a good solution here...

 

[ShenKen]

Have you looked at the price difference between 6” and 8” double wall and class A?

I haven't really studied the price differences, being more concerned that we install the right thing so we not to have problems down the road (which I sadly know from experience can be quite expensive!). Would you care to elaborate a bit more on what you have in mind?

 

[kborndale]

Choose your stove first, then get the appropriate sized chimney for it.

 

[ShenKen]

Sounds to me like a whole house wood furnace would be a good solution here...

I appreciate this feedback. It helps me understand the options and evaluate what we really want out of the wood stove.

When you say furnace, I assume you are talking about something that would be connected to the central ductwork or hot water piping or whatever additional heat distribution system... And I don't think that is what we are looking for, even though that's what I grew up with. Rather, I think what we're really looking for is something cozy and warm to gather around or to dry wet winter wear, etc.

So I think what I'm hearing is that we can't have whole house heat AND cozy ambience all in one unit, so we'll have to choose. Is that correct?

 

[ShenKen]

Choose your stove first, then get the appropriate sized chimney for it.

Thanks for your advice. Also, on your previous comment about draft being too strong, would you mind explaining a bit more on what problems we might see with excessive draft, and how to address or avoid these problems?

 

[Turbo89]

You’ll could have a tough time damping the stove down, and the stove would burn hotter then desired / use wood faster. You would install a damper on top of the stove if this was an issue.

 

[EbS-P]

So I think what I'm hearing is that we can't have whole house heat AND cozy ambience all in one unit, so we'll have to choose

Not with 5000sq ft and a single stove. You have a heatpump. With new construction insulation and air sealing you will never save money by installing a wood stove unless you have really high electric rates or keep it really warm in the winter. So this is not a money decision. Heating 5000 sq ft across 3 levels (how many hvac zones do you have and do you have multiple compressors) with a wood furnace would nearly impossible If you had multiple zones.

You are going to supplement with the stove and burn for enjoyment. How much dry wood do have stacked now. Get enough store for a 3 year supply/rotation.

I could make an argument for a Blaze king King 40 that takes an 8”. But low and slow stoves while they can burn with flames can also run low and slow with a blackened window. Any other stove Drolet, Pacific Energy, Woodstock ect would all be 6 inch stoves.

You can’t go wrong with a PE T5 or T6. Drolet makes a good value oriented product.

I just looked at you basement layout. Does the half way landing on the stairs go all the way up to the ceiling of the first floor?

It’s not a perfect layout but it could work. My guess is you will easily get it to 85 with the stove while upstairs is 70-75 and the top for even cooler. Think of a way to move cold air down to the basement. Air handlers rarely work well.

 

[ShenKen]

I just looked at you basement layout. Does the half way landing on the stairs go all the way up to the ceiling of the first floor?

It’s not a perfect layout but it could work. My guess is you will easily get it to 85 with the stove while upstairs is 70-75 and the top for even cooler. Think of a way to move cold air down to the basement. Air handlers rarely work well.

No. The ceiling height is fixed by the landings of the next flight of stairs directly above.

Regarding airflow, the main floor living room is above and in the same corner as that basement family room. Maybe we could cut a hole in the floor in the far corner. Air blown down in that corner would travel past the stove on its way to the stairway. It would be a fairly large loop with 40-45 ft from the back corner over to the stairs. Is there such a thing as a fan that would sit down inside the joist bay, with a register top (for the floor) and bottom (basement ceiling)?

And thanks for your stove references.

 

[kborndale]

Thanks for your advice. Also, on your previous comment about draft being too strong, would you mind explaining a bit more on what problems we might see with excessive draft, and how to address or avoid these problems?

Excessive draft can cause the stove to overfire. It sucks too much air into the stove which causes the fire to burn too fast and create too much heat. In extreme cases this could leave you with a glowing red stove which obviously is never good . A key damper or two is normally necessary on stoves with chimneys of 20+ feet to slow the draft down to levels the stove can handle.

 

[kborndale]

No. The ceiling height is fixed by the landings of the next flight of stairs directly above.

Regarding airflow, the main floor living room is above and in the same corner as that basement family room. Maybe we could cut a hole in the floor in the far corner. Air blown down in that corner would travel past the stove on its way to the stairway. It would be a fairly large loop with 40-45 ft from the back corner over to the stairs. Is there such a thing as a fan that would sit down inside the joist bay, with a register top (for the floor) and bottom (basement ceiling)?

And thanks for your stove references.

You would want to blow cold air down the stairs so that it forms a convection loop which send hot air up the stairs. Cold air is more dense and easier to move is why you want to force it down instead of trying to push hot air.

 

[brenndatomu]

When you say furnace, I assume you are talking about something that would be connected to the central ductwork or hot water piping or whatever additional heat distribution system... And I don't think that is what we are looking for, even though that's what I grew up with. Rather, I think what we're really looking for is something cozy and warm to gather around or to dry wet winter wear, etc.

Yes, forced air/ductwork.
The Drolet Heat Commander will do both, send heat through the ducts, and be a cozy spot to sit in front of...it has a window in the door for "fire TV", and the front of the firebox still throws a good amount of radiant heat, for that cozy sitting area.
They have a sister model sold and installed through PSG dealers too, but largely the same unit.

Heating 5000 sq ft across 3 levels (how many hvac zones do you have and do you have multiple compressors) with a wood furnace would nearly impossible If you had multiple zones.

Why's that?
Forced air wood furnaces can still use zones/dampers...the main difference is that the dampers need to be power close/spring open, so hot air can still flow if the power goes out in the middle of a rippin fire.
Also, there needs to be a damper or two that is always open, or set to be open when there is no call for heat from the rest of the house...this is your "dump zone", usually the basement, especially an unfinished part, as that can usually make some btus "disappear" easily and not over heat the living areas.

And yes, get your 3 year wood supply cut/split/stacked now! Trying to burn wood that is not truly dry is miserable!

 

[EbS-P]

Why's that?

i was hopeful by the OP had two zones with two different compressors and air handlers. Then a wood furnace would be more challenging to integrate.

5000 sq ft on a single 5 ton system with 2 (or three) zone on a single compressor will be difficult to balance. I wouldn’t want that system.

 

[ShenKen]

i was hopeful by the OP had two zones with two different compressors and air handlers. Then a wood furnace would be more challenging to integrate.

5000 sq ft on a single 5 ton system with 2 (or three) zone on a single compressor will be difficult to balance. I wouldn’t want that system.

I see I never answered your question...

There will be one compressor and air handler for the basement and main floor. This air handler is in the basement. Then a smaller compressor for the upstairs, with an air handler in the attic. As far as multiple zones supplied by the larger compressor, I don't know how my HVAC man is setting that up.