HTI News

Permanent (Hard Coat) vs. Blanket-Style Insulation

The benefits of insulating your engine are numerous: improved performance, increased safety, and prolonged engine life are just some of the most obvious reasons. But once you’ve decided to insulate your engine there are a number of other decisions to make. Should you use a hard permanent engine insulation, or go with a wrap or blanket instead? Both options have their strengths and weaknesses, so in order to make a decision we’re going to have to go a little deeper.

Before we start looking at the two types of insulation let’s just define what we’re talking about. Permanent or ‘hard’ engine insulation is a soft blanket insulation that is then covered with fiberglass and oven cured onto the part that becomes part of the component that is water, fuel and oil resistant. . On the other end of the spectrum we have insulation wraps or blankets. These are a fabric like material with insulating properties that are removable around parts of the engine and attached with fasteners.

Focus Areas


The number one priority for anyone on a job site is safety. Accidents on the job site are expensive and can have a devastating impact on employee morale. Also, watching out for the well-being of your employees is the right thing to do. Removable insulation starts with major disadvantages here. Gaps can form between the wrapping and the hot engine parts, which can quickly become a repository for oil, gas, or other flammable chemicals. This means that you can have a pool of flammable chemicals in a very hot and tightly enclosed space. Obviously this is a huge risk for fires and explosions.

Another obvious disadvantage of removable insulation is it’s temporary. Employees on the job might be tempted to take it off in order to access other engine parts. While this might seem innocent enough, it’s important to understand that consistency is the key to safety. Even if the employee has a good reason for removing the insulation, they are still risking their own safety and the safety of the rest of the crew. Once the blanket is removed it is often not put back on correctly or if at all. How many accidents have happened because something “seemed like a good idea at the time?”.

Hard insulation on the other hand has a tight seal around the parts it’s attached to. It can’t be taken off by an employee in a hurry. This means that you have fewer things to worry about while on the job and can focus on the task at hand.


Because removable insulation has to be flexible, it has to be made out of less dense materials than hard insulation. This means that it takes more removable insulation to do the same job as a hard insulation. Large engines often make for cramped quarters, every inch used for insulation comes at a high cost.

Hard insulation on the other hand takes up significantly less space. This is because the heat capacity of hard insulation is much higher; the hard insulation just “soaks up” heat at a much better rate than removable insulation. Also, because hard insulation installations are custom jobs the parts parts are going to be insulated are carefully as possible. This means that you get the exact amount of insulation you need and don’t have to worry about wasted space.


A blanket is going to absorb more heat from the engine thus causing a higher surface temperature on the blanket which creates an increase in engine room temperatures. Hard insulation keeps the heat in the exhaust component not only creating engine room temperatures to be cooler but causing the engine to perform more efficiently. Keeping the heat in the exhaust components increases fuel efficiency and increases horse power something a blanket cannot do.

The benefits are clear: hard insulation does a better job of insulating your engine. If the main goal of engine insulation is to improve performance then hard insulation is clearly the right choice.


No matter what your removable insulation is made out of it’s only as durable as the fasteners that you use to apply it to your engine. This means that removable engine insulation can tear, fall off, get lost, etc. Also a blanket insulation get brittle over time.

Hard insulation on the other hand is a truly permanent solution. Because it’s permanently bonded to the engine parts it will last much longer while continuing to perform better than removable insulation.

Summing it Up

Engine wraps can be a good “quick fix” for engine insulation problems, but when compared to hard insulation it’s clear who the winner is. Hard insulation might be more expensive, but it’s a smart investment for anyone who is concerned with safety, space, performance and durability.