If you have an active fireplace, you need a chimney cap. This has to do primarily with fire safety.
Chimney caps keep the sparks in your fireplace from escaping and catching your roof on fire. And it also keeps pests like snakes, bats, rats, raccoons, and chimney swifts from seeking refuge in your warm house.
In today’s post, I’m going to tell you everything you need to know about chimney caps.
From the pros and cons to common accessories, to even how to hire a chimney company to come out and install one for you. We’ve got you covered!
Keep out Pests
Have you ever heard of a chimney swift?
They are tiny birds, often referred to as “flying cigars” that like to burrow into chimneys when it gets warm outside. They burrow in your chimney to raise their babies.
Depending on the size of your chimney, you could have more than a THOUSAND swifts at a time. Unfortunately, chimney swifts are federally protected by the Migratory Bird Conservation Act. So no one can bother the birds or the nests until they decide to leave.
Birds are only part of the problem. Think about the diseases from raccoons, rats, possums, etc.
Luckily a cap is really all you need to help make it nearly impossible for them to move in.
Keep out Rain
One of the best reasons to have a chimney cap is to keep moisture out of your house.
It rains a lot. Without a chimney cap, you can easily have rainwater coming into your chimney every time it rains.
Water in your chimney is public enemy #1.
I’ve mentioned this in several other posts, but chimney issues follow the domino effect. When one problem happens, it leads to a lot of other issues.
And a lot of times it all points back to water inside the chimney.
Keeping a cap is something you can do that will help keep your chimney from succumbing to even larger problems caused by water.
Keep out Debris
If water can come in, you can imagine that it’d be easy for other debris to make its way in.
If you have a lot of trees around your house, you probably get a lot of debris around your house when it rains or when the wind blows. Or even when fall comes and the leaves fall.
If you clean your gutters every year, then you surely know how much debris can come across your roof. Leaves, twigs, branches, and any other debris can build up and cause all sorts of problems.
Without a chimney cap in place, you risk your flue getting blocked up, leading to smoke and carbon monoxide back drafting into your home.
Or when you light your fire, the sparks could go up to catch the debris on fire too.
Your chimney isn’t just a one-way street. It’s not just moving air out of your house. It’s also a way for air to come back into your house.
If you live in a windy area, or you use your fireplace during a windstorm, you can have air blowing back down your chimney and into your home.
In the winter, when you don’t have a fire lit, downdrafts can make your home much colder. But if you have a fire going, you may end up with smoke in your house.
A chimney cap will get in the way of downdrafts, keeping your home warm and smoke-free!
Stop Sparks from Flying Out
Think about the last campfire you sat by. It’s mesmerizing to sit and watch the flames dance and the sparks and embers float away into the night.
Those sparks and embers floating up also happen in your fireplace. If nothing’s at the top of your chimney, then you risk one of those embers drifting out of your chimney and landing on your roof.
Just one spark could light your roof on fire. And it doesn’t take much at all. A chimney cap with a spark arrestor will catch the embers before they make it out onto your roof.
If your chimney is made from brick or stone, then you should know that you have a masonry chimney.
The easy part.
Here are the different types of masonry chimney flues:
Single Flue Chimneys with Extended Flues
These chimneys have single flues that extend above their crowns.
Most of the time, they are square, rectangular, round, or oval. The chimney cap you use with these flues is primarily dictated by their shape.
Here are your capping options:
#1. Square, rectangular, and oval flues – If your flue is extended and is in one of these shapes, then you have to attach your cap with clamps or screws.
#2. Round Flues – You can also use clamps and screws to attach a cap to a round flue. However, they can use slip-in caps that slide directly into the flue’s opening.
Single Flue Chimneys without Extended Flues
This kind of chimney flue is flush with the crown of the chimney. The chimney cap you choose relies heavily on the shape of your flue.
Here are your capping options:
#1. Square, rectangular, and oval flues – when your flue is recessed inside the walls of a chimney, you can’t attach a cap directly to it (like you could with the extended flues).
If you want to use a cap with one of these shapes, you’ll have to get a model that can use legs or brackets.
Legs will allow you to convert an externally-mounted cap into one that can be easily slipped into your chimney.
Brackets will make it possible for you to mount your cap to your chimneys crown.
I usually recommend legs for most situations. But if you live in a particularly windy area, I’d recommend brackets since they attach directly to your chimney.
#2. Round Flues – You don’t need to attach legs to a bolt-on cap to protect your non-extended round flues. Just buy a model that’s designed to slip right into your flue’s opening!
Single Flue Chimneys with Flexible Metal Liners
If you have a masonry chimney that is unsafe or damaged, you’ll likely have a metal liner. You’ll know that you have a metal liner because liners are softer and more flexible than other metal ventings.
Because of their design, you can only use a slip-in chimney cap.
The chimney industry isn’t creative when it comes to naming conventions.
The multi-flue chimney is exactly as it sounds. A chimney with multiple flues. These chimneys require a top-mounted chimney cap regardless of whether the flues are extended or not.
Factory Builty Round Metal Chimney
Factory-built chimneys are exactly how they sound. They are kits made in a factory that is assembled at your home.
The flues are usually made of at least two metal flue pipes made of aluminum or stainless steel, one inside the other and separated by an insulating material.
Single-Wall Metal Chimneys
These chimneys literally just consist of a rigid metal tube and nothing else. They’re popular for venting wood-burning stoves.
And when it comes to capping you really need to make sure you’re picking a cap that is designed to work with a single-wall metal pipe.
Here are your options:
#1 Chimney Caps that Fasten to the Flue Exterior – These are just as they sound. They attach to the outside of your flue with either clamps or screws.
#2 Chimney Caps that Slip Into the Flue – These are designed to literally slide right into your flue. You should apply adhesive to create a more secure fit.
Double-Wall Air-Insulated Metal Chimneys
This kind of chimney has two metal walls separated by open space and uses the air in between the metals to cool the flue.
These require chimney caps specifically designed for use with a double-wall air-insulated pipe.
Ideally, you would use a cap that was manufactured by the same company as the chimney.
Double-Wall Solid Pack Insulated Metal Chimneys
These chimneys have an inner and outer wall. But uses insulation to separate the two.
Sometimes you’ll see that the insulation is left exposed. While in others it is covered with a metal cap.
Each type will require its own specific type of cap.
Triple-Wall Air-Insulated Metal Chimneys
Remember the double-wall air-insulated metal chimneys that you read about 30 seconds ago?
This is basically the same.
Except now there are three walls instead of only two.
Triple-Wall Solid Pack Insulated Metal Chimneys
Once again, just like the double-wall solid-pack insulated metal chimneys, these are just the same, except with three walls instead of two.
And once again, you’ll find models that leave the insulation exposed and models that cover it with a metal cap. You need to be sure that you buy a cap that is specifically designed to fit this kind of pipe.
Specialty Chimney Caps
Sometimes you’ll have caps that don’t really fit the stereotypes of the other chimneys.
Standard caps are economical and will protect you from weather, sparks, animals, etc. But sometimes you need a little extra to cover your flue.
Here are the five special kinds:
Draft-Increasing Chimney Caps
All chimney caps will improve your draft. But sometimes you may need a little extra help to prevent downdrafts. Especially if you live in a windy area.
Draft-increasing caps are pretty cool because they are designed to force wind around the top rather than allowing wind through the openings.
The physics behind these caps increases the air velocity to decrease the static pressure above the chimney. This will result in a partial vacuum, forcing the smoke inside the chimney to move upwards.
The harder the wind blows on this cap, the better your updraft will be!
Most draft-increasing chimney caps are designed to be used with a masonry chimney. So if you need one for your masonry chimney, make sure that you are using one that can use an adaptor.
Electric Draft-Increasing Chimney Caps
Sometimes you may have a draft problem that can’t be solved by any other means. So an electric draft-increasing chimney cap might be your best option.
These act as both a chimney cap and a draft inducer. They feature adjustable electric fans that will allow you to directly control your draft.
These are pretty neat, but it does come with an extra cost.
Chimney Cap & Damper Combinations
When you have an older masonry chimney with a loose-fitting, broken, or missing damper, air can escape through your chimney (both hot and cold air) when you aren’t using your fireplace.
With more air escaping, you’ll have wasted energy and that usually correlates with wasted money on your energy bill!
Getting a cap and damper combination may be the easiest way to fix this issue.
These dampers work just like any other top-sealing damper. It sits on top of your flue and is controlled by a cable that runs down your chimney and connects to the lever mounted to your fireplace wall.
They are really convenient, but you should be aware that they are only available for square and rectangular chimneys. If you have an oval or round flue, unfortunately, you’ll need to buy your damper and cap separately.
Outside-Mount Chimney Caps
As you can imagine, most caps are mounted directly onto your chimney’s flue or crown. Outside-mount chimney caps fit over the crown and attach to the body of the chimney.
These are a great choice especially if you have multiple flues, odd-shaped flues, or a poorly constructed crown.
Outside-mount caps will also give you some of the best weather protection since they cover the entire top of your chimney.
But, due to the wide variation in chimney dimensions, they are usually made-to-order.
Flue Stretcher Chimney Caps
Flue stretcher chimney caps allow you to raise the height of your masonry chimney’s flue by a couple of feet while protecting your home.
You might also think that the taller style is more aesthetically pleasing than traditional caps.
The most common problem that these will solve is when you have smoky fireplace problems.
If smoke is coming back into your room when you have a fire burning, a common cause is that your chimney isn’t tall enough. Downdrafts happen for all kinds of reasons. But if your chimney is lower than your roofline then it could be blocking the flow of air to your flue.
A flue stretcher can help in this situation if raising the height of your flue a few feet will make it taller than the surrounding structures.
Common Chimney Sizes
Even the most common chimney caps have differing instructions for measuring for your cap. The easiest way to show you what we need is with a table.
I’ve split them up between masonry and factory-built chimneys. Each of these caps will cover single flues.
Flue Type Flue Shape Cap Type Measurements Needed What to Look For Extended Square or Rectangular Clamp on or screw on 1. Length and width of the outside of your flue A cap designed to fit those dimensions Extended Oval Clamp on or screw on 1. Length and width of the outside of your flue A cap designed to fit an oval opening of those dimensions Extended Round Clamp on or screw on 1. Outside flue diameter A round cap with the same diameter Extended Round Slip In 1. Inside flue diameter A round cap with the same diameter Not Extended Square or Rectangular Bolt-on with legs or brackets 1. Length and depth of the outside of your flue A cap designed to fit those dimensions that is compatible with legs or brackets Not Extended Oval Bolt-on with legs or brackets 1. Length and depth of the outside of your flue A cap designed to fit those dimensions that is compatible with legs or brackets Not Extended Round Slip In Inside flue diameter A round cap with the same diameter Not Extended Any Top Mounted 1. Length & width of the area that will encompass all of your flues
2. Height of your tallest flue
A cap that will cover all of your flues and is 5 in. taller than your tallest flue Metal Liner Round Slip In 1. Inside pipe diameter A round cap with the same diameter Single Wall Round Clamp on or screw on 1. Outside Pipe Diameter A single wall compatible cap of the same diameter
Flue Type Flue Shape Cap Type Measurements Needed What to Look For Single Wall Round Slip-in 1. Inside Pipe Diameter A single wall compatible cap of the same diameter Double-Wall Air Insulated Round Double-Wall Air Insulated 1. Inside Pipe Diameter
2. Outside Pipe Diameter
A cap with an inner opening that is the same size as your pipe's inside diameter and an outer opening that is at least as large as your pipe's ourside diameter. Double-wall Solid Pack Insulated Round Double-wall Solid Pack Insulated 1. Inside Pipe Diameter
2. Outside Pipe Diameter
A cap with an inner opening that is the same size as your pipe's inside diameter and an outer opening that is at least as large as your pipe's ourside diameter. Triple-Wall Air Insulated Round Triple-Wall Air Insulated 1. Innermost Pipe Diameter
2. Outermost Pipe Diameter
A cap with an inner opening that is the same size as your pipe's inside diameter and an outer opening that is at least as large as your pipe's ourside diameter. Triple-wall Solid Pack Insulated Round Triple-wall Solid Pack Insulated 1. Innermost Pipe Diameter
2. Outermost Pipe Diameter
Specialty Chimney Caps
Sometimes you’ll have a special chimney cap. Luckily, that doesn’t necessarily mean you’ll need any special measurements.
It’s just as easy to measure for specialty caps than for more common caps.
Chimney Caps Designed to Increase Draft
Draft-increasing chimney caps are different from standard caps due to the way their tops (or caps) are constructed. Not how they are attached to your chimney.
So, you can just measure for these the same exact way you would for a standard cap.
Chimney Cap & Damper Combinations
All you need to do for these caps is to measure the inside length and inside width of your rectangular (or square) flue. Once you’ve done that, search for a model that fits those dimensions.
Flue Stretcher Chimney Caps
For flue stretcher caps, all you need to measure is your flue’s outside length and width. Then find the cap that is designed to fit those dimensions.
Nice and easy!
No Flue? Read This.
Most masonry chimneys have some kind of flue.
But if you’ve discovered that you are one of the few folks out there without a flue, no need to be worried.
You can still get a cap.
However, your options are going to be limited to those caps that can be mounted directly on your chimney’s crown.
So, basically, you’ll have two choices:
- You can use a standard flue cap with brackets, or
- You can get a model for multiple flues.
Whatever you choose, you’ll need to measure the length and width of our chimney’s opening. This will give you the minimum area that your new cap will need to cover.
Another option that you have is to get a cap that just covers everything, from edge to edge. Just measure the length and width of your entire chimney and find the largest chimney cap you can use.
This last option is probably the best one if you’re looking to minimize costs but maximize protection.
Galvanized steel caps are some of the least expensive around. But they aren’t that strong.
They aren’t so flimsy that they’ll break within the year. You’ll get at least five years out of some high-quality ones.
But they’re more likely to corrode than caps made from the other materials. Once a galvanized cap’s zinc coating is compromised, you can kiss it goodbye.
It’s only a matter of time before the rust comes and you’ll need to buy a new one.
In terms of style, galvanized steel caps are the base model work trucks in the cap world. They are designed for efficiency and that’s it. No style.
They are designed for cost-efficiency and the price savings reflect.
Just like galvanized steel, aluminum chimney caps are cheap and not very durable.
They do, however, hold up to corrosion a lot better than galvanized steel, but aren’t as sturdy. That’s because aluminum weighs less and is a softer metal.
This makes it much easier for wind and strong weather to damage the mountings and they are prone to bending.
In terms of style, aluminum is still a work truck – no flash – but they are at a level above the base model.
The bright, shiny finish helps to look more sophisticated, but the designs are actually pretty similar to galvanized steel.
We recommend stainless steel caps most of the time. They are the best balance between performance and cost.
They are more expensive than galvanized steel and aluminum caps, but they are much tougher. Stainless steel is also almost rust-proof, so you can say that it’s pretty corrosion-resistant.
And since they’re so tough, they are strong enough to withstand harsh weather.
And besides that, most of the time, those caps will come with an extended or lifetime warranty.
AND they require little maintenance. All you typically need to do is clean it every year!
Stainless steel caps are the actual Chevy Silverado 1500. They are a tough, durable, and stylish cap. They are naturally shiny and since they don’t tarnish, you’ll have a good chance that they will remain that way over time.
If you want a chimney cap with a crisp, clean look, then stainless steel is definitely the way to go!
If the style of your cap is a priority for you, then your best choice is a copper chimney cap. You can have a natural copper color or you can let them develop a natural green patina.
Either way, they will enhance your brickwork and provide an elegance that the other caps can’t provide.
Luckily, copper caps are also very durable. They have the same corrosion-resistance properties as stainless steel making copper just as unlikely to rust.
And copper is heavier and generally stronger than stainless steel, so copper caps are usually considered the sturdiest option you can choose.
Most of the options that we see are protected with a lifetime warranty.
All this strength, beauty, and protection definitely comes at a cost, though.
Copper chimney caps are usually about four times more than galvanized steel caps and twice as much as comparable stainless steel caps.
And the maintenance is pretty demanding if you want to keep the natural copper look. You’ll need to clean it regularly and continuously reapply protectant.
We use adaptors more than the other accessories. The four kinds are factory-built to masonry adaptors, flue shape adaptors, legs, and brackets.
Factory-Built to Masonry Adaptors
These are cool because they allow you to use specialty chimney caps that are normally designed for factory-built chimneys with your masonry chimneys.
Flue Shape Adaptors
This adaptor will allow us to use a chimney cap with a flue shape that the cap wasn’t originally built to fit. It’s pretty neat, but will only work with masonry chimneys.
They will allow you to use a standard single flue cap with a square, rectangular, or even an oval masonry flue that isn’t extended.
All you need to do is attach the legs to the cap and slide it into your flue like you would with a regular slip in model.
We like to use these for most instances, except in places where there’s a lot of wind. In that case, you are better off just getting brackets.
Brackets are similar to legs in that they allow you to fit a single-flue cap with a square, rectangular, or oval masonry flue that isn’t extended.
They’re more secure than legs in windy conditions because they’re mounted directly on your chimney’s crown.
Adhesives, Sealants, and Screws
We secure chimney caps with an adhesive, sealant, and/or screws.
If you’re more for DIY projects, then you should know that the screws are usually included with the cap when you buy it.
But sealants or adhesives are something you’ll need to buy on your own. Luckily, your cap’s installation manual will tell you the best kind of sealant or adhesive you need.
Most chimney caps don’t require any sort of additional treatments to keep them in good shape.
But in the cases of copper or aluminum caps, you may want to apply a protectant to keep the shine on it.
Most of the time, you’ll find these in spray containers and they’ll guard your chimney cap against fungus, oil, and even water.
How to Hire, What to Look For
When you’re hiring a chimney company, you should always ask the following questions before allowing them to come into your home:
- Can the company provide references?
- Does the company carry a valid business liability insurance policy?
- Does the company ensure that a certified chimney technician will be on the job?
If they guarantee all three of those, then you are in a good spot. The technicians don’t necessarily need to be certified by the CSIA, but I do recommend putting in a bit more due diligence before accepting a certification that’s not by the CSIA.
This is because certifications are a tricky thing, especially in an unlicensed industry like ours. Any company can craft a list of job-related questions and sell them as an exam and certify those who pass.
I recommend you take a few extra minutes in your research before making your hiring decision to learn more about the certification the company has. Here are a few tips to make sure the certification is reputable:
- Is the word “certified” just part of the business name or is it an earned designation?
- Is the certifying body a for-profit business or non-profit?
- Does the certification need to be maintained and renewed through continuing education as the industry evolves, or is it well enough to be certified through a one-time exam?
- Is the certifying body well-established or are they relatively new to the scene? New doesn’t mean “bad” but you should make sure the requirements for certification are more or at least equally stringent as those of more established certifications
- Is the mission statement of the certifying body focused on educating and protecting homeowners or is it more focused on making it easier to earn a certification?
- Does holding the certification require following a code of ethics?
If you can answer all of these questions, then I think it will be safe to allow the company in your home to work on your chimney.
Please note that If you are hiring a chimney company to install a cap for you, most of the time, they will need to buy the cap themselves. This is primarily for liability and insurance purposes.
Besides, it’s probably cheaper for them to buy a cap at the dealer discount than for you to buy one at retail cost.
It doesn’t matter if you are in Roanoke, Lynchburg, Blacksburg, or some other city anywhere in the USA — if you have any questions about the safety of hiring a chimney company, please don’t hesitate to email me at firstname.lastname@example.org or call me at 540-225-2626. I’m happy to help!