Can coating 3 sides of a wood stove with Refractory Cement reduce stove efficiency

ptm01

New Member
Nov 17, 2019
5
NE
Hi All,
I have a friend in Maine who heats his house with wood during the winter. He has to cut a lot of wood to do so. His Vermont Castings Vigilant stove cracked several years ago and he has coated much of the inside with refractory cement . Only the front doors and top lid are not coated.
Questions:

1) Will this reduce the efficiency of the stove because less of the fire heat gets radiated to the cast iron and therefore to the outside room?
(He acknowledges that the sides of the stove are cooler than they used to be )

2)The stove currently uses inside air to burn the wood, through a flap in the back. If you are burning a lot of wood, aren't you using up the oxygen in the house and doesn't that lower the air pressure in the house, leading the house to draw in more cold air from the outside? Shouldn't he pipe in outside air directly to the stove? Is there a kit to do that?

3) How do you grab more heat from a Vermont Castings Vigilant Stove. Do the kits that sit in or around the stove pipe and blow hot air, work?

In advance, thank you for your help.

Regards,

Peter
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,411
central pa
Hi All,
I have a friend in Maine who heats his house with wood during the winter. He has to cut a lot of wood to do so. His Vermont Castings Vigilant stove cracked several years ago and he has coated much of the inside with refractory cement . Only the front doors and top lid are not coated.
Questions:

1) Will this reduce the efficiency of the stove because less of the fire heat gets radiated to the cast iron and therefore to the outside room?
(He acknowledges that the sides of the stove are cooler than they used to be )

2)The stove currently uses inside air to burn the wood, through a flap in the back. If you are burning a lot of wood, aren't you using up the oxygen in the house and doesn't that lower the air pressure in the house, leading the house to draw in more cold air from the outside? Shouldn't he pipe in outside air directly to the stove? Is there a kit to do that?

3) How do you grab more heat from a Vermont Castings Vigilant Stove. Do the kits that sit in or around the stove pipe and blow hot air, work?

In advance, thank you for your help.

Regards,

Peter
If his stove is cracked it is time to get a new one. There are many more efficient and durable stoves available that are easier to use
 

ptm01

New Member
Nov 17, 2019
5
NE
If his stove is cracked it is time to get a new one. There are many more efficient and durable stoves available that are easier to use
Thank you for your advice. Would you be able to list some options that I could present to him ? Do the newer stoves have a payback period because they use less wood?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,411
central pa
Thank you for your advice. Would you be able to list some options that I could present to him ? Do the newer stoves have a payback period because they use less wood?
They may use a bit less wood yes. But the payback is in not having an unsafe cracked cast iron box with a fire in it in your home. As far as recommendations do some research here there are tons of good stoves on the market now.
 

begreen

Mooderator
Staff member
Nov 18, 2005
79,596
South Puget Sound, WA
The Vigilant was a decent stove for its time and a workhorse, but it sounds like it has seen the end of its days. In order to make a recommendation, we would need to know more about the current installation to be sure it is a good fit and safe. At this point we don't know much. He could get a much better heater for under $1200, but in order to work properly he would need to have fully seasoned firewood, a proper hearth and flue system. With those factors satisfied, he probably could heat using 40-50% less wood and he would have a nice fire view with glass that stays clean.
 
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peakbagger

Minister of Fire
Jul 11, 2008
4,780
Northern NH
To answer the first question is yes insulating the interior of the stove will reduce its heat output. Its highly unlikely the secondary bypass system is working so that cuts the efficiency way down. Replacing it with modern EPA stove will reduce his wood usage by about a third.
 

RSole

Member
Jan 13, 2016
11
Kweebecque
Refractory cement and cast iron may have slightly different coefficients of expansion with heat that would be exaserbated as the area is increased, so it is very possible that there are cracks in the cement that may not be easily visible. It is also possible that un-cemented areas (like the top, bottom and front) would get hotter than the cemented areas and create uneven expansion in the stove as it heats up. I may be wrong, but it sounds like it could be dangerous.
 
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moresnow

Minister of Fire
Jan 13, 2015
979
Iowa
3) How do you grab more heat from a Vermont Castings Vigilant Stove. Do the kits that sit in or around the stove pipe and blow hot air, work?
Rather imperative that you do not cool the stove pipe with a fan kit as it will increase the dangerous creosote deposits inside. No good. Chimney fire can result from these deposits. Not what your buddy needs. If you need more reassurance on this topic start a new thread. It will be confirmed quickly.
 
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ptm01

New Member
Nov 17, 2019
5
NE
Yes, I have heard that warning...I thought these devices were temperature controlled to avoid creosote problems. I do some more research on it and start a separate thread. Thanks.
 

ptm01

New Member
Nov 17, 2019
5
NE
The Vigilant was a decent stove for its time and a workhorse, but it sounds like it has seen the end of its days. In order to make a recommendation, we would need to know more about the current installation to be sure it is a good fit and safe. At this point we don't know much. He could get a much better heater for under $1200, but in order to work properly he would need to have fully seasoned firewood, a proper hearth and flue system. With those factors satisfied, he probably could heat using 40-50% less wood and he would have a nice fire view with glass that stays clean.
He uses seasoned firewood. He has an 8 inch insulated flue that travels 16 feet from the stove to the roof. It is a windy spot, so plenty of draw. The stove is centered in middle of the first floor, which is completely open floor plan. It's an old 1920, wood cape style house, with plaster walls and no insulation.
 

ptm01

New Member
Nov 17, 2019
5
NE
To answer the first question is yes insulating the interior of the stove will reduce its heat output. Its highly unlikely the secondary bypass system is working so that cuts the efficiency way down. Replacing it with modern EPA stove will reduce his wood usage by about a third.
I didn't think about the secondary bypass system. Thanks for pointing that out.
 

RSole

Member
Jan 13, 2016
11
Kweebecque
"Rather imperative that you do not cool the stove pipe with a fan kit..."

I just bought a Heat Magic (heat exchanger with thermostaically controlled fan) that installs in the stove pipe, just above the stove. The stove is a Regency F3100 with fire bricks and shields on sides and back so I think 90% of the heat is going up the chimney. Only when the exhaust gas get to a certain temp will the fan come on. I can clean my chimney from inside the house and plan to check on the buildup once a week to see how bad it gets.
 
Last edited:

webby3650

Master of Fire
Sep 2, 2008
10,522
Indiana
"Rather imperative that you do not cool the stove pipe with a fan kit..."

I just bought a Heat Magic (heat exchanger with thermostaically controlled fan) that installs in the stove pipe, just above the stove. The stove is a Regency F3100 with fire bricks and shields on sides and back so I think 90% of the heat is going up the chimney. Only when the exhaust gas get to a certain temp will the fan come on. I can clean my chimney from inside the house and plan to check on the buildup once a week to see how bad it gets.
If 90% of the heat is going up the flue, it’s due to trying boil water out of your firewood is my guess. The 3100 is a heater, with dry wood and a good flue it’s hard to beat. I don’t suppose it’s in an uninsulated basement?
 

RSole

Member
Jan 13, 2016
11
Kweebecque
If 90% of the heat is going up the flue, it’s due to trying boil water out of your firewood is my guess. The 3100 is a heater, with dry wood and a good flue it’s hard to beat. I don’t suppose it’s in an uninsulated basement?
The walls are insulated but the floor is bare concrete. Unheated, it's a constant 14 degrees Celsius (57F) down there lately with temps outside at night -12C (10F) to -4C (25F) so I think the concrete floor is sucking up all the heat. This stove was made for tight, mobile home installation with its welded shields on the sides and back, removing them would help (I've got lots of clearance) but may void the stove's certification. Why did they not allow for shield removal with additional clearance??
I'm also looking for cheap SPC flooring with an underpad attached as a thermal break to see if that makes a big difference.
p.s. I use very dry, seasoned wood.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,411
central pa
"Rather imperative that you do not cool the stove pipe with a fan kit..."

I just bought a Heat Magic (heat exchanger with thermostaically controlled fan) that installs in the stove pipe, just above the stove. The stove is a Regency F3100 with fire bricks and shields on sides and back so I think 90% of the heat is going up the chimney. Only when the exhaust gas get to a certain temp will the fan come on. I can clean my chimney from inside the house and plan to check on the buildup once a week to see how bad it gets.
Take that thing off of the stove. If you run that 3100 correctly there should not be excess heat going up the flue for that thing to scavenge
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,411
central pa
The walls are insulated but the floor is bare concrete. Unheated, it's a constant 14 degrees Celsius (57F) down there lately with temps outside at night -12C (10F) to -4C (25F) so I think the concrete floor is sucking up all the heat. This stove was made for tight, mobile home installation with its welded shields on the sides and back, removing them would help (I've got lots of clearance) but may void the stove's certification. Why did they not allow for shield removal with additional clearance??
I'm also looking for cheap SPC flooring with an underpad attached as a thermal break to see if that makes a big difference.
p.s. I use very dry, seasoned wood.
How are you running the stove and what moisture content is your wood at?
 

RSole

Member
Jan 13, 2016
11
Kweebecque
How are you running the stove and what moisture content is your wood at?
Not running yet, but the last few years with dry, seasoned wood (don't have a moisture meter, but should make one with my ohmmeter).
I've always had a 20" steel bladed fan blowing from two feet behind the stove, blowing over the top of the stove and around the vertical stovepipe. I can see the pipe temp drop as soon as the fan starts. It went through the foundation wall into a crumbling masonry chimney with an 8 inch flue. This years it's a 6 inch SS insulated flue straight up to the roof. I cleaned the masonry chimney once a year and it always had minimal buildup, due to dry wood, hot fires, I guess, The new SS chimney has not been attached to yet.
 

begreen

Mooderator
Staff member
Nov 18, 2005
79,596
South Puget Sound, WA
I just bought a Heat Magic (heat exchanger with thermostaically controlled fan) that installs in the stove pipe, just above the stove. The stove is a Regency F3100 with fire bricks and shields on sides and back so I think 90% of the heat is going up the chimney. Only when the exhaust gas get to a certain temp will the fan come on. I can clean my chimney from inside the house and plan to check on the buildup once a week to see how bad it gets.
Bad idea. A better name for that should be creosote machine. Your stove is fairly efficient. The stove should be doing the heating, not the flue. A certain amount of heat going up the flue is desirable. For your stove it will be 25% or less, not 90%. Once the flue gases drop below 250º creosote will start condensing.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,411
central pa
Not running yet, but the last few years with dry, seasoned wood (don't have a moisture meter, but should make one with my ohmmeter).
I've always had a 20" steel bladed fan blowing from two feet behind the stove, blowing over the top of the stove and around the vertical stovepipe. I can see the pipe temp drop as soon as the fan starts. It went through the foundation wall into a crumbling masonry chimney with an 8 inch flue. This years it's a 6 inch SS insulated flue straight up to the roof. I cleaned the masonry chimney once a year and it always had minimal buildup, due to dry wood, hot fires, I guess, The new SS chimney has not been attached to yet.
That doesn't tell us how you are running the stove. What temp do you start shutting the stove back at? What temp does the pipe cruise at?