hpr-knowledge-base/hpr_transcripts/hpr1729.txt

Episode: 1729
Title: HPR1729: Shield's Up - Wood Stove Heat Shield Project
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1729/hpr1729.mp3
Transcribed: 2025-10-18 08:19:29

---

This is HPR episode 1,729 entitled Shields Up Wood Stove Heat Shield Project.
It is hosted by David Whitman and is about 16 minutes long.
The summary is, David Whitman builds a safety heat shield for a Wood Stove in his shop.
This episode of HPR is brought to you by An Honesthost.com.
Get 15% discount on all shared hosting with the offer code HPR15.
That's HPR15.
Better web hosting that's honest and fair at An Honesthost.com.
Hello David Whitman here from St. Helen's Oregon.
I wanted to share today a little bit about the project that I took on to make my Wood Stove
heater a little bit safer in my shop.
Now I don't use wood heat in my house necessarily.
I do have a pellet stove in there that has a control system on it.
I don't use it very much because we have cheap electricity rates in a heat pump.
But in my shop, when I bought my place, the shop was already built.
It was fairly modern, only a couple of years old.
It already had a Wood Stove that had been installed with a permit that had been properly installed.
I felt pretty good about this, but as I was using it, it did what all wood stoves do.
It got over hot sometimes.
So you'd have to keep adjusting or I'd have to keep adjusting the airflow when I loaded
wood in and that amount of fuel that it has in it and the airflow really controlled the
temperature of it and the type of fuel.
So it got pretty hot at times.
You're burning some small dry wood.
The air is a little too wide open.
The top of the wood stove with the flame hits.
I observed with an infrared non-contact thermometer, one of those IR guns that I have.
I observed the temperature at 900 degrees on the top of the metal.
Now the stove is lined with some brick to keep it from degrading the metal on the bottom.
It does have kind of an internal flame shield up there, but it was 900 degrees on the
top.
The sides rated out around 535, 500 Fahrenheit, so that was also pretty hot.
When I read the side plate on the stove, it declared that it needed to be 18 inches from
the back wall, which in my shop has a two foot cement stem wall that goes to a six inch
footing and the floor is poured on top of the footing.
So I have about 18 inches of concrete before the sheet rock starts on the wall.
Then it's covered with wall board and it's an insulated shop.
It's quite nice, really, nicely done with a finish on it and painted.
So the walls of the stove were 500 degrees, the top 900, the tags that it started to
install, the stove of 18 inches, which it was away from the wall, and at least 30 inches
on the side, the back 18 inches, the sides 30 inches.
There's a lot of space there.
Things get put in that area around the stove because no matter how big a shop is, it's
never large enough.
You'll always get a piece of equipment or some project in it that takes up some space.
I thought I would build something to protect the wall surface behind the stove pipe from
heat, extra heat in case of a chimney fire, and the sides just give them some sort of
passive protection.
So if things were closer, combustible things were closer than the 30 inches for some reason
that I wouldn't have a problem with that and I have a little more piece of mind.
The first thing I thought of was using concrete blocks.
They cost a dollar or two each.
They're easy to stack up.
They're 8 inches by 16 inches by 6 inches, so they're modular or you can get an 8 inch wide
block, 8x8x16.
You can get 12 if you desire also.
Other stone materials like bricks are available.
You can get a 4 inch block and I started looking at how many I would need and they're ugly.
They didn't really lap out correctly so that I could make a nice looking wall around
my stove or a place to hold the heat in to keep the floor space and areas from being
hot and I certainly couldn't do anything with the stove pipe with the blocks.
They were a viable solution but not the one I really wanted to go with.
Looking good is that important to me, not all that much, which works as really most important.
But as I thought about some things that I had observed in my lifetime, I had noticed
that people use insulation and metal a lot of times to contain heat.
A metal heat shield, a piece of metal between something hot and another object will keep
the object from getting not so hot.
Think of the 454 engine, had the starter which was real close to the exhaust manifold.
Chevy put a metal heat shield in to protect that, to keep it from getting hot and getting
graded.
You'll notice in your cars a lot of times there will be a piece of metal just to shield
a little barrier in a way that keeps things from degrading or getting too hot, wiring.
It doesn't matter what it is around the hot surfaces.
If it's extremely hot there will be a piece of metal there.
So I decided to use metal for my project and I like to save a little money on my projects.
I like them to be useful but also to save money.
I won't go to the extent of going out and getting a piece of total scrap that doesn't look
somewhat good but I don't want to just get a resty old piece of junk.
So I went down and bought some corrugated metal roofing that's about 20 gauge from the
building supply store.
And I took some new EMT conduit, electrical metallic tubing that's used to pull wires through
about the half inch stuff from the home supply in Portland.
And the stuff is really inexpensive.
I like to have a few pieces of it around.
It's really nice just to cut.
You can cut it easily with a hacksaw or a tubing cutter.
It's really nice to take around the field and drive in the field for posts to put a flag
on for something to...
You can put it in the garden for stakes and that in...
I've used it driven it in the ground around a newly planted tree and used a sisal twine
to then hold the tree up so the wind wouldn't blow it over while I was getting its root
system.
So I took some of that and bent myself a hoop out of that and attached a piece of this
sheet metal which was 24 inches wide.
I attached it to either side of this hoop that I built so I made a little stand with
a wall with an air gap in between it for each side of the wood stove.
Dropped a couple of pieces of tubing across the top and screwed them in.
One of the requirements that I have when I work on something that has some value where
I'm making a modification that maybe I appreciate is not to damage the original piece.
So I did this by making this thing basically freestanding.
So about two inches from the stove is a double wall of sheet metal with an air gap on either
side and then I wanted to protect the wall from overheating behind the wood stove chimney
pipe and the wood stove chimney pipe as six inches diameter goes up to a thimble that
holds in the attic a piece of insulated pipe that is required through the attic and
to go out the roof.
So that's really safe up there and in order to make the heat shield there I have a six
inch black pipe going up.
I took a piece of eight inch pipe and went around that thimble which leaves a inch and a
half air gap around that pipe and I attached it at the top with a great big hose clamp.
I got at the hardware store an ideal clamp.
That kind you would see on a radiator hose and older cars and sometimes they'll use
them for drier hoses and they have a advancing screw on them with slots in the clamp metal
so it tightens down and you can get quite a good grip with them.
So I put it, I will push the pipe up there, put it around the stove pipe which is about
ten feet from the floor and I attached it up there, squeeze it on there so that it
holds and the thimble not being exactly smooth it has some ribs built into it held really
really good so it just dangles a piece of stove pipe that for the most part circles the
other stove pipe that has an air gap in the middle and then I attached another piece
of pipe.
I screwed the my part of the thing together with some sheet metal screws to hold.
So I have stove pipe heat shield around the bottom going clear to the ceiling.
It doesn't look all that great to you but I really like it and it works really really
good so my temperature reductions are pretty nice.
The stove pipe runs around 200 degrees it gets a little cooler as it goes up to the 300
at the bottom and it gets a little cooler as it goes up but on the outside of the stove
pipe you know I have maybe I only have one piece of metal between that stove pipe it
gets to around 90 to 100 degrees now.
So I got a pretty fair temperature reduction out of that.
Sheet rock will not burn at 100 degrees and will want to start on fire get hot enough
to light at 100 degrees and I can prove that because there's a lot of places that have
over a hundred degree temperatures in them and the houses don't just catch on fire.
Now down at the on the sides of the wood stove I did nothing for the top of the wood stove
I don't really care about that the heat the temperature the heat is taken away quickly
by the convection there but on the sides of the stove where I have the 500 degrees about
two inches from the stove is the first wall of this heat shield it ends up being 300 degrees
Fahrenheit there so I have a temperature reduction from say 500 to 300 at that point.
Now there's a gap of a half inch nominal in between the two pieces of metal and on the
outside piece of metal that's on the atmosphere side away for this away from the stove the
temperature of that surface is at what the ambient temperature of the air is around.
If I look at a thermometer and measure that with the non-contact thermometer I'm getting
a temperature that's right about the same so the reduction is really really great the
thermal dynamics of the air passing through just carries that heat away and so if I put
something a chair with a coat on it or something that has combustibility that's easy to start
on fire or something I can get it fairly close to the stove and feel pretty safe about it so
I really like the outcome of my project and nobody told me to do it this way I kind of looked
at the back shield each shield on the stove but it's just something I've kind of observed
and always have known and I remember seeing a movie one time with John Wayne in it where
they fought OOL fires and that's what they made a piece of metal in front of them and they
would kind of make a cocoon around themselves but they would keep water on it if they could get
right up to the well head and put the fire out but the purpose of my project was to make it a
little safer around the exterior of the wood stove I certainly achieved that very easily and so
I'm really proud of it at least for myself my wife says it's ugly you know she married me what
does that say anyhow glad for the outcome of my project and I'm glad to be able to share this
with you and I have a PDF picture in the show notes so take time to look at that if you want to
you can see my handiwork and see what's not worth going to St. Helens to steal so thank you very
much and this is David signing out for HPR you've been listening to Hacker Public Radio at Hacker
Public Radio dot org we are a community podcast network that release the shows every weekday
Monday through Friday today's show like all our shows was contributed by an HPR listener like
yourself if you ever thought of recording a podcast and click on our contributing to find out
how easy it really is Hacker Public Radio was founded by the digital dog pound and the
infonominant computer club and it's part of the binary revolution at binrev.com if you have
comments on today's show please email the host directly leave a comment on the website or record
a follow-up episode yourself unless otherwise status today's show is released on the creative
commons attribution share a light 3.0 license