The Log Rack
Chimney Drafting Problems Article
No two fireplaces are alike when it comes to smoking chimneys. There are many factors as to why a
chimney doesn't draft properly and your home gets filled with smoke. This article on chimney drafting
problems offers suggestions as to the possible solutions. Any one of these suggestions could work or
it might take a couple of them to find the solution. The first question I always ask is your firewood
seasoned? Moisture content of firewood should be less than 20%. If the wood you are burning is not
properly seasoned this can cause excess smoke and poor heat output. Always check your firewood
first.
the 10ft - 2ft rule for chimney heights
Chimney height. Every chimney should abide by the 10ft - 2ft
rule. Under normal conditions your
chimney should work fine if this rule is met but there are always
exceptions. Measure out 10ft
horizontally from your chimney to the nearest object (roof line,
peak, room addition etc), once you
have the 10ft mark go vertically 2ft up and that should be the
height of your chimney. See diagram.
Your chimney should be at the proper height with the stack high
enough to catch the wind. Your
chimney doesn't have to rise above the peak unless the peak is
within the 10ft clearance. As the wind
blows across your homes roof line it should create an updraft
bringing the smoke with it. Sometimes a
negative pressure situation might occur where the wind causes a
downdraft and you may have to look
at raising the height of your chimney. Recently some new
products have arrived on the market to help
ease the cost of raising a chimney.
Flue extenders are a chimney
cap that is raised up to 3ft with long
sheet metal sides. They come in stainless steel or copper and
have proven to solve many drafting problems.
They a relatively  inexpensive compared to having a brick mason
come out and raise the flue tiles. Flue Extenders are also
available in copper. Copper ages to a beautiful verdigris green
after it is exposed to the outdoor elements and will give your
home  great "Curb Appeal".If you have a metal zero clearance
fireplace you will have to get the manufacturers name and the
model number off a plate inside the firebox  to determine which
size and brand pipe you will need to purchase to raise the
chimney another 1 - 3ft.  Some cities require that the pipe be
enclosed in a chase and you might have to rebuild the chase up
to the new height. While raising the height of your chimney will
solve most of the problems some chimneys may need more help.
raise the height of your chimney with a flue strecher chimney cap
Flue Stretcher
Other great products on the market for solving drafting problems are the
Vacu-Stack and the Windbeater chimney caps.
These chimney caps are designed to create an updraft as the wind blows.
The cap itself stays stationary and this causes
the wind to circulate creating the updraft. This solution works well with
masonry, metal chimneys and even the solid pack
chimney pipe for wood burning stoves. They come in several sizes and
adaptors are available for masonry chimneys. The picture at the right shows a
Vacu-Stack with the adaptor installed on a masonry chimney. With a metal
chimney no adaptor is needed. If you have a air cooled chimney pipe one
where there are 2 or 3 pipes inside each other just measure the inner one for
the cap.  The Vacu-Stack for the air cooled, double or triple wall pipe comes
with a collar to cover the outer pipes. The Vacu-Stack and the Windbeater
caps also come in smaller sizes to fit furnace and hot water tanks to solve
their drafting problems.
vaccu-stack chimney cap installed on masonry chimney
Another possible solution to chimney drafting problems could be the opening size of your firebox in
comparison to the flue size.  If the opening is to large for the flue it might  not draft properly. The
formula to use is W X H ÷10. Example: if your opening is 36W X 28H you would have 1008 inches ÷10
gives you 100.8 inches of drafting space required. A 10"X10" flue would give you 100 sq inches and
that would be the minimum size you need. It's OK to go a little larger flue size but not to much as a
larger flue can also cause drafting problems. If you are using a round flue or pipe you would use the
same formula but ÷ it by 12.  A temporary solution might be to place firebricks under your fireplace
grate. This will raise the fire up higher into the smoke chamber allowing it to draft better. Another
solution would be to install
fireplace glass doors, using a wider frame style can reduce the size of
your opening and increase the draft.
Multiple flues in the same chimney can also cause problems. If you have two fireplaces or a fireplace
and a furnace using the same chimney but separate flues a negative pressure can exist. You might
be enjoying an evening in front of the fire only to realize that smoke is entering your basement
through the furnace. Negative pressure is causing the smoke to be drawn back down the other flue to
replace the air that is drawn up through the fireplace. To test if this is what's happening you can
crack open a window. If this seems to solve the problem you have several steps you can do. The first
step would be to raise the flue of the fireplace 1 to 2ft higher. This would get the smoke up higher so
it isn't drawn back down the other flue.  If the other flue is used for a fireplace you can put a
Lyemance or Lock Top damper on the flue. Both the Lyemance and the Lock Top seal air tight and
will stop the smoke from being drawn back down the flue. If the other flue is used for a furnace or hot
water tank we would recommend the first step in raising the fireplace flue because when the fireplace
is not in use and the furnace is running your could be drawing CO fumes from your furnace down the
fireplace flue and this could be disastrous.
CO detectors  are recommended to be used in every
home. Another solution would be to install a Fresh Air Ventilator which brings filtered air into your
home and you control the air flow. This can be installed in any wall in your home and it easier to
install than a dryer vent.. The Fresh Air Ventilator can equalize the negative air pressure in your
home.
Example of 10ft 2ft rule
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