Wood Stove Heat Shield: Everything You Need to Know

Wood stove installation involves more than just wrestling it into place and hooking it up to the chimney.

Being sure you know the installation requirements follow the required clearances is critical to keep your family and your home safe from a potential fire hazard.

A wood burning stove heat shield is a fantastic way to protect your home and family from the intense and drying heat that can come off of a wood stove. They work by reflecting the majority of the heat away from the house, preventing it from seeping through cracks and burning your floor, walls, and furniture. They take up very little space and installation is relatively easy.

What is a Wood Stove Heat Shield?

Wood stove heat shields, by utilizing air space around them, reduce the amount of space that you need in between your wood stove and the combustible materials (like walls!) of your house.

Heat shields, when installed correctly, reduce the space you need from the stove to the wall by 2/3, and from the stove to the ceiling by 1/2.

With reduced clearances around your wood stove, you have more room to put stuff!

Why Are Heat Shields and Clearances Necessary?

The obvious answer is to keep from setting your house on fire!

The less obvious answer is that even though it may SEEM like you have enough clearance between your stove and combustible material...it's not always that obvious.

A heat shield minimizes the risk of damage from the intense and drying heat generated by a fireplace stove. Heat shields can protect your home from this intense heat by reflecting it away from your house, preventing cracks that could let in extreme highs or lows.

It's recommended that you never allow your walls, floor, and ceiling (any combustible surface, actually!) to get above 115 degrees Fahrenheit of the ambient temperature. (So, if your room is 65 degrees, your walls should not be hotter than 180!) Doing so risks what is called pyrolysis.

Pyrolysis happens when repeated exposure to heat begins to break down the molecular structure of a material..which, in turn, lowers its autoignition temperature.

In other words, the temperature necessary to set it on fire!

So, without proper safeguards, a wood stove configuration may SEEM fine, but over time the degradation of material slowly lowers its ignition threshold, then suddenly you have a house fire on your hands!

You can sometimes see pyrolysis damage from discoloration, but not always...which makes it more dangerous.

Note in the picture below that the trim on the left is too close to the wood stove!

What are wood stove clearances?

Wood stove clearances are the required distance between any combustible materials and a wood-burning stove or chimney. The purpose is to provide adequate space for free air flow, thus cooling, for the area around wood stoves.

National Fire Protection Association (NFPA) generally calls for a 36" clearance between your stove and the walls and ceiling.

However...and this is where it gets tricky...different stoves have different designs, so require different clearances. Many wood stoves have been tested, and are "listed." If your stove is "listed," you can "Install According to Manufacturer's instructions" and follow those clearances as a guideline.

What do I put behind a wood-burning stove?

One solution to reducing clearances is to use non-combustible surfaces surrounding your wood stove. For example, Maine code (base on NFPA code) states that a 3 1/2" masonry wall without an insulated air space can reduce clearance, at the most, by 33%. (33% of 36 inches is 11 7/8 inches. 36-11 7/8= 24 1/8" total clearance.)

Masonry here refers to stone or brick. (Tile does not count because it's too thin.)

This code also allows for 1/2" "non-combustible insulation board over 1 in. (25.4 mm) glass fiber or mineral wool batts without ventilated air space."

However, if any of these options are impossible or undesirable, you could opt for a heat shield instead!

How does a heat shield work?

A wood Stove heat shield works by absorbing radiant heat from a wood-burning stove, then dissipating it through the air space all around it.

Thus, the combustible materials are insulated both by the air space and the heat shield, and don't get too hot.

What Should Heat Shields be Made of?

A heat shield can be made of metal or non-combustible insulation.

According to NFPA code, metal heat shields should be made of 24 gauge steel and have a 1" air space behind them where air can move freely to dissipate heat.

The spacers used to create the air space need to be non-combustible as well and should be placed off to the side and not directly behind the wood stoves.

You could also build a heat shield from masonry materials, provided that you include means for air flow to dissipate the heat radiating from your stove.

For example, still using spacers, secure sheets of cement board to the wall. Then, using a "non-combustible adhesive" as dictated by the safety code, adhere ceramic tiles to the cement board.

Where Can I Buy a Heat Shield?

You can purchase a ready-made shield like this one

Or this one.

Or you can build one.

How Do You Build a Heat Shield?

Building a Metal Heat Shield

First, measure.

Your wood stove heat shield should be installed anyplace within 36" from a combustible wall to the heat source.

The best way to do this is to cut a piece of scrap wood 36" long, place one end against all the edges of the wood burning stove, then place the other end up against the walls. Make a pencil mark on the wall at the far reaches of the stick. Your wall shield should extend an inch or so beyond this mark.

Now here's where you need to make a few decisions on how to attach the wall protector. The sturdiest way is to screw it directly to the wall studs. However, your studs might not line up perfectly...and probably won't completely since many steel sheets are 2 feet wide and most wall studs are 16" apart.

What I would do is pre-drill the sheet metal in the lowest point of the curve (if corrugated) an inch from the edge and every 16".

Next, use a stud finder to locate the wall framing. (Make a pencil mark so you don't have to keep going back to locate it after you go look for that cordless drill that you just put down SOMEWHERE!)

Hold the sheet metal against the wall, and using a sharpie marker, mark each hole through the sheet metal and onto the combustible wall.

Then remove the sheet metal and pre-drill holes into the walls. Where the studs are, drill holes 1/32" smaller than the shaft of the screws. (The shaft itself..not the threads).

Once the holes are drilled, hold the sheet metal back up to the combustible wall, hold the spacer behind the metal, and insert the screws. (It's really beneficial to have a helper here!)

I would get a couple of screws into the top edge...but not tighten them down at this point to give myself a little "wiggle-room" to get the other holes lined up.

Once the first couple of screws are in, line up the second piece of metal, and, through the predrilled holes, screw them together with sheet metal screws. (You shouldn't put mounting hardware spacers directly behind the stove because they would conduct heat to the combustible walls.)

On the outside edge of the second metal piece, secure it to the wall with the spacers like you did the first piece.

Once everything lines up, continue the installation by screwing in the spacers around the top, bottom, and sides of the heat shield.

Conclusion

Any wood stove installation must adequately protect combustible material from the heat that is generated by the stove.

A heat shield with good air circulation protects combustible material from pyrolisis and fire and the clearance reduction gives you more room!

Ultimately, follow the manufacturer's instructions and ask your local code enforcement officer if you have questions about the required clearance.

People Also Ask

Q. Does a wood stove need a heat shield?

A. Not necessarily. However, using a heat shield helps protect combustible materials from pyrolisis and the risk of fire.

Q. What is a good heat shield for a wood stove?

A. Metal or masonry with a 1" air space

Q. How close can a wood stove be to a heat shield?

A. It depends on the stove's rating. In some cases, when using heat shield specifications, a heat shield will reduce clearances by 66%.

A. What is the best metal for a heat shield?

NFPA code calls for 24 gauge steel

Q. Is sheet metal fireproof?

A. You could argue that not much is fireproof if you get it hot enough. 24 Gauge steel has a melting point of around 2500 degrees, though, so for wood stove applications it's fireproof enough.

Q. Can I use aluminum foil as a heat shield?

I think that would be a really bad idea. It's nowhere close 24 gauge.

Q. Can cement board be used as a heat shield?

Yes, but since it is less than 3 1/2 inches, you need an air gap of at least an inch behind it for it to count as a "properly constructed heat shield."