By Greg Stark

Before I stepped into the niche industry of rooftop grease containment, you couldn’t have convinced me that fats, oils, greases, and/or other chemicals were getting onto the rooftops of commercial and industrial buildings. I remember that first day on the job learning about exhaust systems, why we need them, and how they work. Only then did it begin to make sense. For someone who may not have had the training I had in rooftop grease containment, much like myself 10 years ago, I understand that this whole “grease on my roof needs to be contained” thing can seem like snake oil (snake oil should be contained on a rooftop as well).  It is very easy to say “I don’t have problems with cooking oil on my roof, and if there is oil up there, who cares!?”.

Well, that is the purpose of this post. I would like to put 10 years of experience right into your thoughts in a single convenient read. This is some of the same knowledge we pass on to our employees over multiple weeks of training. I will try to keep it informative, read-worthy, and the one-stop spot for what you need to know. Let’s get started with “The Everything Guide to Rooftop Grease.” Feel free to scroll down to a particular section that may have answers to your questions.



Introduction to Cooking Systems and Fats, Oils, and Greases








There are many ways that food is prepared and cooked inside of a restaurant. It is important you understand different cooking equipment and how much grease each one produces and why. Knowing this information will allow you to install and troubleshoot specific situations on site. Of course, this is not all cooking equipment, and individual research will always be needed.

Broilers –

Also known as charbroilers this type of cooking equipment is designed to give foods cooked upon it a light char look and flavor. This is done by placing the food on a cooktop that heats the food from the bottom up. Broilers, due to their high cooking temperatures, produce high volumes of grease.

Char Grills –

Much like a broiler, this equipment is also designed to give foods a light charred look and flavor. However, the chargrill cooks through a series of grates much like your grill at home along with a fuel or heating element below. This cooks from the bottom up. Due to high temperatures and open flame, chargrills also produce high volumes of grease.

Flat Grills –

Also known as griddles, flat grills are defined by a solid, usually cast iron, plate above a heating element. Flat grills allow for a consistent temperature over the whole surface area of the food being cooked upon it. Due to this fact along with high cooking temperatures, this equipment also produces high volumes of grease.

Woks –

A wok is a traditional Chinese cooking pot typical used for stir-frying food although its uses go far beyond just that. A wok can be identified by its large round bottom shaped pot sitting atop a pit stove (basically a high heat element accessed through a circular opening in the cooktop the wok fits into).  A wok produces a medium level of grease, but more than one wok is usually being used for one exhaust fan creating the potential for higher levels of grease production. The type of grease produced by a wok is usually less viscous due to the type of food prepared at high temperatures.

Fryers –

A fryer is a type of cooking equipment that uses a metal basket to submerging foods in hot oil in order for them to be cooked quickly. Fryers can be identified by their baskets, but also the deep vats of oil on the cooking surface. Fryers produce medium levels of grease as the cooking process is done mostly at lower temperatures while the food is submerged in the oil.

Rotisseries –

A rotisserie is used by putting food onto a skewer that rotates around a heating element cooking food slowly thus preserving the tenderness of the food. A rotisserie is easily identified by the large skewers holding food around the heating element. A rotisserie, due to low temperatures, produces low volumes of grease.

An Introduction to Hood Systems

Once smoke, airborne grease and the smell it brings leave the cooktop, it is the job of the hood system to make sure it is properly exhausted from the restaurant. The hood is properly named as it is a literal hood overall cooking system in the restaurant. The hood has many features such as hood filters, which help filter out some grease as well as sparks from flames on the cooktop. The hood also contains what is known as an ANSUL system which is a fire protection system to help stop any fire that spreads into the ductwork. This hood system connects through a series of ductwork up to the rooftop where a fan is sucking the smoke and grease-filled air outside of the restaurant. We will discuss these fans later on.

The grease that is pulled into the hood system and the ductwork attached begins to cool as it moves away from the heat of the cooktop. As this happens it begins to solidify and stick the ductwork on its way to the rooftop. For this reason, they need to be cleaned frequently not only to maintain the life of the system but also to help prevent fire hazards. This work is completed by a kitchen exhaust cleaner, also known as a KEC (Kitchen Exhaust Cleaning) provider or “hood cleaner”. It is recommended hood systems are cleaned monthly from both inside the restaurant and from the rooftop level. Next, we will discuss the kitchen exhaust cleaner in more depth as their cleaning process is vital to the life of the Grease Guard containment system on the rooftop.


An Introduction to Kitchen Exhaust Cleaning

Kitchen Exhaust Cleaning (KEC) is a vital and legally required function of restaurant operations. The fire and performance standards inflicted by improperly maintained hood systems can destroy a restaurant. For this reason, kitchen exhaust cleaning, also called hood cleaning, is performed anywhere from every month to every six months depending on the volume of cooking done at that particular location. As exhaust cleaning requires access to the cooking equipment it is always performed after the restaurant closes or before it opens.

Most KEC providers use a degreasing agent in addition to pressure washers that spray at high pressures into the ductwork to free up dried particles in the system. As they perform the service, water is collected, usually through a system of plastic sheet magnets held to the system itself. This water is then properly disposed of.

There are two main types of processes that a kitchen exhaust cleaner will engage in to complete the job effectively. We will look at both.


The main part of exhaust cleaning involves cleaning the hood system inside of the restaurant. After water reclamation has been set up the cleaner will proceed with spraying down the hood system and the reachable ductwork as far up as possible. For longer sections of ductwork, access panels on the ductwork may have to be opened for more complete cleaning.


In addition to cleaning upward toward the roof, a cleaner will have to clean the exhaust fan on the rooftop and the ductwork heading downward toward the cooktop. In this process, the cleaner will open the fan via a hinge that should be installed on the fan and fan curb. This allows the fan to be opened much like a door providing access to not only the fan but the ductwork below.

Once the fan is open it is thoroughly sprayed with the water and chemical to ensure it is clean. Water should be reclaimed using much of the same system used in the bottom-up cleaning. If not, grease will spatter all over the roof deck and surrounding equipment. In addition to water reclamation, the grease containment system installed should be properly covered and due care given to ensure the chemical being used in the exhaust cleaning does not touch the containment. This is largely in part because containment systems often use oil-based absorbents and a degreasing chemical will nullify the containment system’s ability to properly collect and process grease through the filter media. It is important you are able to recognize these issues as they will likely mandate conversations with the exhaust cleaner.

An Introduction to Exhaust Fans

Side Mount rooftop grease containment to keep drips of grease off of your roof.

Upblast Exhaust Fan –

The upblast exhaust fan is the most common type of fan you will encounter in the field. The term upblast is defined by the way the equipment moves air upward from the kitchen to the rooftop. The shroud or bowl of the fan not only protects the internal mechanics of the fan but also directs the air upward with velocity where it can be properly exhausted away from the building. These fans typically have a grease spout or drain that allows grease to be drained mainly on a single side of the fan.

Supreme Exhaust Fan –

A supreme exhaust fan is designed not only to properly exhaust the kitchen but also to add special features such as higher performance for larger quantities of particulated air, built-in grease containment, added durability, and product life, as well as a host of other technical advantages over other fan types. A supreme fan will typically leak or blow grease from the exhaust ductwork located on the main side of the fan or the area known as the drum (the large cylinder in the middle of the fan) which collects the grease for later cleaning.

Makeup Air/Combo Exhaust Fan –

A combo curb, which is a single roof opening for two pieces of equipment allows for both an upblast exhaust fan and typically a makeup air unit to occupy the same area. This is done predominantly to save space on the rooftop. The makeup air unit can regulate the amount of air inside the restaurant by replacing the air exhausted by the exhaust fans. This is known as air balancing which assists in decreasing negative pressure issues inside the restaurant. Grease should not be produced by a makeup air system, but the exhaust fan on the same curb (most likely upblast) will produce grease in the same areas as if it was a standalone exhaust fan.

Utility Set Exhaust Fan –

The utility set exhaust fan is named because of its ability to be used for almost any application. The levels of customization available for these fan types include size, shape, indoor and outdoor applications, control settings, supply and return air management and many other options that allow for this fan type to be utilized in any situation. Even though there are many variations of this fan type, grease is predominantly produced under the main drum of the unit located directly below the exhaust ductwork or from the exhaust ductwork itself.


An Introduction to Basic Roofing Systems

In addition to cooking equipment, exhaust systems, and exhaust fans, it is equally important you have a basic understanding of roofing systems. This knowledge will help you properly install a Grease Guard on certain roofing types, be able to properly assess rooftop issues, and help you understand the importance of quality of work to avoid affecting the roofing system as they are worth thousands of dollars.

Built-Up Roof (BUR) –

Also known as “tar and gravel” or “rock roofs” this roofing type is usually made of coal tar and covered by rocks or pea gravel. This roofing system is instantly recognized by the gravel laid on the roof deck. The most important thing you must know about this roof type is that you should try to avoid walking on the rock when possible. Most rock roofs have roof pads to step on. The other important note here is that you do not install grease containment systems on top of the gravel. The rock MUST be cleared so the containment system is lying flat on the roof deck.

Metal Panel Roofing –

Metal panel roofing is popular in rainy or water prone geographies due to its water management capabilities. A metal panel roof is recognizable because of the ribs or ridges in the metal stretching across the roof. There is no rubber on the roof deck as the ridges allow water to run properly off the roof. The most important thing to know on metal panel roofs is that the containment system must be properly placed so it is level and not positioned so an edge of the containment system is hanging between ribs. BE CAREFUL! METAL ROOFS CAN BE SLIPPERY!

Polymer-Modified Bitumen –

Polymer – modified bitumen is a roofing type that allows for extra flexibility in a roofing system for geographies that have varying weather throughout the year. This roof type is recognizable by the grayish long sheets with a smaller width and many seams. The surface is usually textured for grip by the type of asphalt material used in its construction.

Thermoplastic Membrane –

The most popular types of roofing systems in this category are PVC (polyvinyl chloride) and TPO (thermoplastic olefin). This is commonly large white sheets of material placed by heating the material and pressing at seams. This roofing type is sold to be animal fat resistant as well as “cooler” and is very fragile to sharp objects. Knowing that you are on a white TPO or PVC roof you should be very careful when cleaning and using tools.

Thermoset Membrane –

Most commonly known as an EPDM (Ethylene propylene diene terpolymer) or “a rubber roof” this roof type is very common in all parts of the United States. The main reason is the durability and flexibility of the material, which is comprised of a mix of both rubbers and plastics. When working on a thermoset membrane you will notice the large black sheets and the heat radiating from them. EPDM roofs can also have gravel tops so be careful not to confuse this with BUR roof systems. You must be careful when walking on hot rubber roofs as just walking on them can cause damage. Also, grease is especially dangerous on these roof types as rubber is easily broken down by acidic grease.

Spray polyurethane foam

Also known as the SPF or “spray roof” this roof type is used for both aesthetics as well as thermal protection and durability from elements and rooftop equipment. The material used for an SPF is usually a plastic foam that be sprayed in varying layers to increase thickness. It is easy to notice an SPF roofing system as there are no seams or sheets. The whole roofing system is usually one solid color. This roofing type is as susceptible to grease damage as any other and should be treated carefully especially around tools.

What is Grease?!

“Grease – thick, oily lubricant consisting of inedible lard, the rendered fat of waste animal parts, or petroleum-derived or synthetic oil containing a thickening agent.

White grease is made from inedible hog fat and has a low content of free fatty acids. Yellow grease is made from darker parts of the hog and may include parts used to make white grease. Brown grease contains beef and mutton fats as well as hog fats. Fleshing grease is the fatty material trimmed from hides and pelts. Bone grease, hide grease, and garbage grease are named according to their origin. In some factories, food offal is used along with animal carcasses, butcher-shop scraps, and garbage from restaurants for recovery of fats.

Greases of mineral or synthetic origin consist of a thickening agent dispersed in a liquid lubricant such as petroleum oil or a synthetic fluid. The thickening agent may be soap, an inorganic gel, or an organic substance. Other additives inhibit oxidation and corrosion, prevent wear, and change viscosity. The fluid component is the more important lubricant for clearances between parts that are relatively large, but for small clearances, the molecular soap layers provide the lubrication.

Synthetic grease may consist of synthetic oils containing standard soaps or maybe a mixture of synthetic thickeners, or bases, in petroleum oils. Silicones are greases in which both the base and the oil are synthetic. Synthetic greases are made in water-soluble and water-resistant forms and may be used over a wide temperature range. The synthetics can be used in contact with natural or other rubbers because they do not soften these materials.

Special-purpose greases may contain two or more soap bases or special additives to gain a special characteristic. “

Grease is found in cooking oils, fat of animals, clothes, fuel, makeup and a ton of other things you may not expect that we make today. Now some of the oils listed are naturally forming, i.e. crude oil we pull from the earth or fat in animals. Others, in today’s scientific world, are synthetic. Whether it be in industrial or commercial manufacturing of goods, natural or synthetic, it is all over the place these days. In most cases, this is a good thing. Very beneficial things like fuel, plastics, lubricants, and even butter are made from F.O.G.s (Fats, Oils, Greases).

Let’s zoom on a prime cut steak in a fancy restaurant.

The New York Strip is mostly meat, however, about 9% is made up of fats, oils, and greases. Thrown on the grill after marination and oiling the grill, that could be even more. As the meat is heated, it vaporizes, and some of the animal fat is infused with oxygen and carried away by the heats updraft. If you want to feel the effect of this, work in a restaurant kitchen for a full day then look at the layer of grease on your skin, not to mention the smell. This airborne grease has another downside. Due to the infusing of oxygen, it has oxidized.

Acidic Oxidation and You!

Acidic Oxidation is the process of an element being infused with oxygen making it more acidic than the beginning elements’ natural state.

As we follow the floating grease molecules up the kitchens exhaust system, we see it sticking to the side of the ductwork designed to carry smoke and smells out of the restaurant. The longer you go without cleaning, the thicker the layer of grease gets. Even worse, as the grease cools back down, it re-solidifies and hardens. This is where kitchen exhaust cleaners need to come in (on a monthly basis according to the NFPA 96 guidelines) and clean that ductwork. If they didn’t clean it, the fire hazard would only grow for as you may already know, grease is fuel to a fire, which no one wants.

Some of that same grease gets all the way up to the rooftop exhaust fan that is sucking the air from below. As the grease gets into the fan, it will either drop out of a special spout on the fan or find another way out of the ductwork and onto your roof. Rubber is the most used roofing material in the world. It is used for its strength, durability and importantly, flexibility. As the roof heats due to the sun, rubber has the ability to expand, and as it cools, contract. This allows for the roof membranes to endure the elements without fear of cracking, breaking, and damaging the roof system. Unfortunately, it is prone to grease damage. The acids in the grease break down the flexible rubber molecules and then bake into those cracks with prolonged sun exposure. Grease can damage a roofing system in as little as two weeks. Repairs for this damage can reach thousands of dollars. Certain roofing systems are F.O.G. resistant, but the keyword is resistant, not proof.

The Goal of Rooftop Grease Containment

How Grease Guard protects you from the harmful effects of grease on rooftops.


Prevent Roof Damage / Protect Roofing Warranties

Containment must prevent grease from reaching the membranes of the roofing system and causing roofing system failures which can cause thousands of dollars in damage and a voided roof warranty.

Protect Storm Drain –

Containment must prevent grease from getting into the storm drains, which can cause blockages in the sewage system. Blockages in the sewage system can lead to floods, sewer fires and contamination of water supplies.

Help the Environment (Eco-Friendly)

Containment must prevent grease from gaining access to plants, animals, soil and the air to keep them from the harmful effects of grease.

Help Prevent Fire Hazards (Fire Retardant)

Containment must be fire retardant. This is to ensure that grease collected into the system does not make it a fuel tank. It is also to make sure that if a fire does break out that it does not spread across the roof system. This ensures the safety of the staff inside as well as the neighbors.


Rooftop containment systems must take water management into consideration. If you have a bucket collecting grease, what happens when it rains and that bucket overflows? Grease on your roof.

How Much Keeping Grease Off of Your Roof Should Cost

Containment costs are going to vary from application to application and scope of work. In retrofit applications, where containment needs to be installed after a location’s construction is complete, there may need to be uninstallation of alternate containment, roof clean up, and roof repair performed. This process may need to be repeated on multiple fans with varying sizes and levels of grease production. In fact, there are at least eight different variables that should be considered for a rooftop grease containment scope of work:

Curb Size

Without this information, there is no way to confirm the size of the Grease Guard. Improperly sized Grease Guards can result in overpaying for coverage or even worse, not having enough coverage.

Type of Equipment

Upblast, Downblast, Utility, Make up Air, Stack, Sidewall, Supreme, Etc. Having the proper equipment will clue you into what containment needs may have to be met.

Discharge Type & Volume

What oil or chemical is coming out of the fan? What is the temperature? Do you have any idea of quantity? Having this information will help to resolve not only the Grease Guard type but also how often the filters should be replaced.

Cooking Equipment

Knowing you are dealing with deep fryer which produces little to no grease versus a wood-burning grill produces large amounts of grease can be the difference between effective containment and failing containment.


Varying factors such as seasonal temperature changes, types of wildlife, weather patterns, etc. should be considered. Places without winter will require more frequent filter replacement. In certain states, birds can pick apart a unit.

Install Location

Where is the Grease Guard being installed? This helps understand the production level. An industrial facility may need XHD filter media. A pizza place may only require a Drip Guard. Knowing the location will help.

Retrofit or New Build 

In a new construction project, there has to be a roof and exhaust fans already installed to complete the work. For retrofits, the containment area must be free of grease. Knowing what type of project this is, will help in determining needs.


Who is going to maintain the system(s) after installation? See below.

Who Should Install/Maintain My Containment System?

Installation of your grease containment system, as long as it is not a pickle bucket, should be done by an authorized manufacturer-approved company. In many cases, like ours, the manufacturer offers installation and maintenance services with their products. However, your kitchen exhaust cleaner, mechanical company, roofing company, or HVAC company should also be able to help with this process. There are a few factors to consider when choosing the right company.

Experience Level

How much experience does the contractor have with installing grease containment systems? Never done before = NO.

Quality of Solution

If someone offers to install buckets, pans, or a complicated piping system, avoid at all costs. The solution should meet all of the goals mentioned above.

Maintenance Capabilities

Some contractors will offer to install the product, but not maintain it. ALL containment systems require maintenance, usually quarterly. So the contractor should be able to come out to your location at least that often

The Scale of Work

If you have locations in every mainland U.S. State you either need a national company or a few companies region to region. Make sure you know what the geographical capabilities are for the contractor.

Scope of Work Fit

You want to make sure the program makes sense for the contractor being asked to perform the work. Having a roofer maintain containment during annual inspections may not fit in their scope of work as well as the kitchen exhaust cleaning company.


Should probably not pay a mechanical company charging $75.00 per hour to maintain containment. Figuring out a flat rate is recommended where possible.


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