Can Expanding Foam Be Used Around Heating Pipes? (Explained)

Like duct tape, expanding foam has been hacked in more ways than you can imagine. Initially, its role was to fill small cavities in the wall, especially those that are hard to reach.

However, these days, expanding foam can be used to silence noisy metal sinks and quiet the thumps from HVAC vents among many other applications.

Another widespread use of expanding foam is to fill gaps left by water pipes. If you hate seeing the space left by pipes inside walls, you are tired of vermin hiding inside, or the occasional rattling, expanding foam can be of significant use.

However, as well all know, there are different types of pipes in our homes. If you have regular pipes, you may have no problem filling the gaps with expanding foam. But if they are heating pipes, you have some doubts.

Will the heat melt the expanding foam? Is it safe for expanding foam to be in close contact with heating pipes? This article will explain in detail what happens when you use expanding foam around heating pipes.

Cooper pipes of gas heating system in the boiler room

Should You Use Expanding Foam Around Heating Pipes?

Most expanding foams are safe to use at temperatures not exceeding 240 degrees F. The recommended maximum temperature setting for home water heating systems is 120 degrees F. This means that the temperature in the pipes can be accommodated by expanding foam.

A safety issue would have risen only if the temperature in the heating pipes was higher than the one expanding foam can handle. In such a situation, it would be inadvisable to use expanding foam since it would have been melted.

From the above, it’s okay to use expanding foam to fill gaps around heating pipes. But there are two things you have to confirm before spraying the expanding foam around heating pipes.

One, you must check the maximum temperature of the expanding foam. This information will be written on the label. Secondly, you must be aware of how hot the heating pipes in your property get.

If the temperature of the heating pipes is less than that which the expanding foam can endure. You can proceed. But if it’s more, look for another alternative because the expanding foam will be melted, and it can release toxic fumes.

Do I Need to Insulate Heating Pipes Before Spraying Expanding Foam?

Spray foams can take the heat from a hot water pipe. Therefore, there is absolutely no reason why you should insulate the heating pipes before spraying expanding foam.

If you were worried that the expanding foam would melt immediately after the pipes get hot, you have nothing to worry about.

Will Expanding Foam Off-gas When Exposed to Constant Heat from the Pipes?

We have already ruled out that expanding foam is safe to use around heating pipes since the heat produced is within expanding foam’s working range.

However, what most people don’t factor in is the heat in these pipes will be constant. Every day, the expanding foam will be exposed to some heat.

As the above happens, you should expect the expanding foam to off-gas. This will be impossible to avoid since expanding foam is made using polyol resin and isocyanate, both of which are susceptible to changes in temperature.

After some time, when you get close to the gap around the heating pipes, which you have sealed with expanding foam. There will be a chemical smell.

If you are worried about the chemical off-gassing, you will be glad to know it doesn’t occur immediately. In some instances, you may never smell the off-gassing. But if you still have doubts, you should consider another alternative such as plaster or mortar.

The problem with mortar is that it will accelerate the corrosion of the heating pipes, especially if they are made of copper. Both options have pros and cons. You have to evaluate which of the two suits your preferences.

Can I Use the Fire-retardant Expanding Foam Around Heating Pipes?

If you can get your hands on fire-retardant expanding foam, that would even be better and safer. Unlike typical expanding foam, this one can endure exposure to much higher temperatures. Therefore, it should be able to withstand the heat from the pipes.

Is Expanding Foam Suitable for Use Around Heating Pipes?

Yes, and here are reasons we think expanding foam is an excellent material to fill gaps around heating pipes.

First, expanding foam can accommodate the expansion and contraction of heating pipes. It is very easy to use. All you have to do is spray it inside the gap, which should be filled.

Secondly, expanding foam can last for years as long as it’s not exposed to UV light once it expands to its maximum size.

Compared to options such as mortar, expanding foam ensures your heating pipes remain rust-free. Should there be some rust, you should look for leaks.

Can Expanding Foam Damage Heating Pipes as It Hardens?

If you have ever seen expanding foam cure, you can testify that it expands to about thirty and sixty times its initial size.

Spraying such material on heating pipes may make you wonder if it will damage them as it expands. One of the benefits of expanding foam is that it expands according to the space available.

If there are copper pipes around, it will not damage them. Instead, it will inflate all around them, ensuring they are fixed and don’t rattle anymore.

How to Fill Gaps Around Heating Pipes Using Expanding Foam?

People may talk about how easy it is to use expanding foam. But if you have never interacted with it, it will be a little intimidating for the first time.

To ensure you know what you are doing, here is a quick guide on filling gaps around heating pipes using expanding foam.

Step 1 – Shop for some quality expanding foam. Most of you are familiar with Great Stuff, but there are other expanding foams such as Big Gap filler and TITE FOAM. Both these options can deliver lasting results.

Step 2 – Prep the working area. Start by covering the surrounding area. Sometimes, expanding foam can be very messy to work with. To ensure the project lasts for a very long, remove any loose materials and ensure there is no grease.

Step 3 – Moisten the surface with some water. This helps the expanding foam in the curing process.

Step 4 – Shake the can vigorously to ensure the contents are mixed. Then attach the spray applicator gun that is sold alongside the expanding foam. Start spraying the foam inside the gap around the heating pipes.

Remember to shake the can from time to time. Do not hesitate to apply more pressure when necessary. Do not be very generous with the expanding foam. You could be left with a huge mess.

Step 5 – Once you are contented that expanding foam sprayed on is enough, give it 24 hours to cure. After it cures, you can cut, sand, and even paint over the foam to ensure the gap is not noticeable. Before painting over it, we recommend applying a filler to ensure the finish is smoother.

Is Expanding Foam Heat Resistant?

When planning to use expanding foam around areas such as heating pipes, it is crucial to consider the heat resistance of this product.

As mentioned earlier, the heat resistance of most expanding foams is higher than that produced by heating pipes. This is why the two can co-exist without any problems.

It’s important to know that expanding foam can only resist heat up to a certain degree. The maximum heat resistance of most expanding foams is around 200 to 300 degrees F.

If the temperatures exceed that range, you shouldn’t use expanding foam. Therefore, the bottom line is that expanding foam is only heat resistant up to a certain point. Expanding foam will melt and produce fumes when exposed to a lot of heat.

Where Should You Not Use Expanding Foam?

Having discovered that expanding foam can be used around heating pipes, it is crucial that we also list other areas where you should avoid spraying this material.

Despite having many applications, it’s essential to know the limitations of expanding foam.

• In or around electrical boxes.

No matter your reasons, never spray expanding foam inside or around electrical boxes. This can destroy electrical components, and don’t forget that expanding foam can ignite in extreme temperatures.

• Avoid using high expansion expanding foam on windows and doors.

There are two main types of expanding foam, low and high expansion. The latter isn’t ideal for tight and fragile areas. When used on doors, it can expand and pop the frames of the windows or doors.

• Never use expanding foam as a long-term solution for leakages in heating pipes.

Suppose your heating pipes are leaking. Fix them right away or call a professional plumber. You can use expanding foam as a short fix but not for long-term solutions.

When you spray expanding foam, it doesn’t stop the leaks. What happens is that it only slows it down. The water will spread to other parts, and that’s when damage inside your wall starts to occur. Mold will also develop.

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