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Should Old Insulation Be Removed Before Installing New Insulation?

old insulation

Insulation helps keep your home comfortable and energy-efficient. But many homes have an inadequate amount of insulation.

If you are considering adding new insulation to your basement, crawl space, or another area of your home, you may be wondering if it's necessary to remove old insulation. In most cases, the answer is “no,” since the existing insulation provides an added layer of protection.

But in certain situations old insulation can do more harm than good. In these few circumstances, it is absolutely essential to remove it.

The guide below will help you determine when it is necessary to remove old insulation and when you can get by without it. This is imperative for keeping costs low while ensuring the integrity of your new insulation.


Proper air circulation is important in your home. Hot air rises. During colder months, heat moves to your attic and, if improperly insulated, it escapes. Attic insulation acts as a heat barrier that keeps this from happening.

A proper sealing means air flows freely through your home. This also means that your HVAC system doesn’t have to work as hard to circulate air to reach the desired room temperature.

Based on this you might assume that more home insulation equals greater heat-trapping ability. That is generally true. But some ventilation is important as well.

An over-insulated home can trap moisture that can cause mould or affect air quality. That is why it is important to have the appropriate amount of insulation in your home. If you are unsure, a trained technician can tell you whether or not leaving existing insulation will impact ventilation.


If moisture has damaged your old insulation, you should remove it. If you had a leak in your roof or a burst water line, this can lead to mould and mildew in the insulated area.

The products used to make insulation––cellulose and fibreglass––can hold moisture for long periods of time. So, even if you don’t have problems right now, you could down the road. Mould spores and mildew can spread to and contaminate new insulation.


Rodents also can damage insulation. Roof rats are a common culprit and they can bring ticks, mites, and mosquitoes with them.

Rats can use insulation material to build nests and they can contaminate it with urine and droppings. This can result in bacteria that can spread throughout existing and new insulation materials.

Note that, if you have had an infestation, the pests need to be eradicated before installing new insulation. You must remove the remnants and properly clean and disinfect the area.

Know When to Remove Old Insulation

Now that you have an idea of when you should remove old insulation before installing a new product, you can be sure your home is operating at optimum efficiency. In some circumstances, only a part of the contaminated insulation needs removal. But a reputable installer will be able to tell you exactly what steps are necessary.

At Durham Insulation, we have been providing quality insulation products and services for more than 30 years throughout the Durham Region. We use environmentally friendly, recycled insulation materials made in Canada. We provide both installation and insulation removal services and can advise you on the best course of action for your home.



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