How to get the Chimney Height just right - Need advice

[bobanne]

Hi there. I really appreciate all the great advice I've been given here. We have a successful install of a BK Ashford 30.2 stove and are really enjoying it.

Here is the question: Because we were having a new roof installed just after we set up our chimney, we left it short enough that it didn't need a brace.

• It is safely 3 feet above any surrounding roof and 2 feet above the ridge. It has been working wonderfully for a couple of weeks with temperatures ranging from 13F to 50F.
• We live at an elevation just under 6,000 ft. BK recommends a minimum chimney height of 17.5 feet at this elevation.
• The chimney is straight up through the roof and is currently only about 13 feet total.

I have the other 5 feet of chimney ready to install with the brace.
Because of how well the stove has been working, I am worried that going to 18 feet may create too strong a draft.

What can you tell me?

Thank you.

@begreen @stoveliker @BKVP @Highbeam

 

[Trevor Tahclep]

IMHO you should follow the manufacturers recommendations, they test and know how their products react under specific conditions.

 

[BKVP]

More draft can allow for higher Btu output but more importantly, allow the combustor to stay active at lowest achievable burn rates. Love the slab wood.

I'd make a barrier to keep wood from falling into your new stove.

BKVP

 

[stoveliker]

Yes, it may work fine now - because of the level of heat you are asking for falls within the parameters that the stove+chimney system can handle with this weather.
But if this spring you'll be wanting to burn at a lower rate (which the BK should be able to when installed to spec), you may run into trouble with a chimney that's shorter than suggested.

I've hesitated a bit (though who am I, given that bkvp provided input...) - why change a working system. But it's working now, and when it's warmer it may not.
Also, I think I see no insulation yet at the roof? That means you'll be needing more heat now and you'll be running at a lower output later. So a taller chimney would likely better allow for that.

The one thing in the back of my mind is that you're in WY, and at elevation. It gets Cold there. I hope you don't get too much draft when it's cold with a captial C..
On the other hand "too much draft" would disallow running very low (because with the Tstat fully closed it would still suck in a lot of air through the hole) - but you might not want to run very low then as you may be wanting more heat.

So, overall, you have two choices.
1. Run as is *the full season*, so you can see what you need in spring and when you're properly insulated (in spring), and then determine whether you need more draft when it's warmer.
2. Add length now and be done.

I would do the latter as I think your running at 50 was at a higher output than you will eventually be running when the home is better insulated.

 

[bobanne]

More draft can allow for higher Btu output but more importantly, allow the combustor to stay active at lowest achievable burn rates. Love the slab wood.

I'd make a barrier to keep wood from falling into your new stove.

BKVP

Thanks for the response and explanation BKVP, I really appreciate it.

 

[bobanne]

Yes, it may work fine now - because of the level of heat you are asking for falls within the parameters that the stove+chimney system can handle with this weather.
But if this spring you'll be wanting to burn at a lower rate (which the BK should be able to when installed to spec), you may run into trouble with a chimney that's shorter than suggested.

I've hesitated a bit (though who am I, given that bkvp provided input...) - why change a working system. But it's working now, and when it's warmer it may not.
Also, I think I see no insulation yet at the roof? That means you'll be needing more heat now and you'll be running at a lower output later. So a taller chimney would likely better allow for that.

The one thing in the back of my mind is that you're in WY, and at elevation. It gets Cold there. I hope you don't get too much draft when it's cold with a captial C..
On the other hand "too much draft" would disallow running very low (because with the Tstat fully closed it would still suck in a lot of air through the hole) - but you might not want to run very low then as you may be wanting more heat.

So, overall, you have two choices.
1. Run as is *the full season*, so you can see what you need in spring and when you're properly insulated (in spring), and then determine whether you need more draft when it's warmer.
2. Add length now and be done.

I would do the latter as I think your running at 50 was at a higher output than you will eventually be running when the home is better insulated.

Thanks, good thoughts and I agree.

 

[Highbeam]

So you're already at 3 feet above the roof deck. Another 5 and you'll be super tall at 8' above the deck and you can't reach the cap for cleaning. Of course, you would need at least one roof brace but also it might look silly having such a tall stack above the roof. Do aesthetics matter?

You can be 5' above the roof with no brace as I recall. That's a couple more feet and you will meet the 15' minimum for sea level.

I hate roof penetrations so resist the roof braces. If anybody can get the roof braces sealed well where they screw into the roof it's the roofers. Otherwise they will blame your leaks on you and deny any future claims. So if you're going to do it I think I'd do it with the roofing job.

If I were you I would add the 2 to get 15'.

Look, I only have 12' on my princess and I'm at 700 feet ASL. That's all the book specified in 2012. It would look pretty dumb to add an extra 3' and a brace. Maybe this means I can't quite run as low as others but I still am very happy with the low end output.

The 15 or 17 or whatever is a "recommendation" only.

 

[stoveliker]

Yeah, but I think his burning will be different once the place is insulated. 13 ft at 6000 ft elevation seems low.

Roof penetrations matter indeed, and the looks would be somewhat odd as well, I agree.

 

[moresnow]

I'd be inclined to add a 2' section at minimum. The BK recommendation has been researched to optimize performance. May as well get the most out of your investment! Good luck.

 

[bobanne]

More draft can allow for higher Btu output but more importantly, allow the combustor to stay active at lowest achievable burn rates. Love the slab wood.

I'd make a barrier to keep wood from falling into your new stove.

BKVP

@BKVP question about your signature, ("Get the most from your stove! Burn dry wood, keep your chimney clean and in the event it is a catalytic model, keep your door-gasket seal adjusted nice and tight. Don't burn trash in any stove, there is a proper way to deal with refuse.") What paper is ok to use? Can I burn mail that isn't on shiny paper?

 

[Highbeam]

Get a propane soldering torch. They’re perfect for fire starting.

 

[BKVP]

@BKVP question about your signature, ("Get the most from your stove! Burn dry wood, keep your chimney clean and in the event it is a catalytic model, keep your door-gasket seal adjusted nice and tight. Don't burn trash in any stove, there is a proper way to deal with refuse.") What paper is ok to use? Can I burn mail that isn't on shiny paper?

Use black newsprint newspaper or obtain fire starters.

BKVP