Carpenter Ants and a new nesting source: Rigid Foamboard Insulation

July 9th, 2010 by Cathy Rust Leave a reply »

A friend of mine was in her kitchen one night about a month ago enjoying a bit of peace and quiet, debating about whether to have dessert or a glass of wine after a particularly hectic day.  The kids were upstairs studying, the dogs were outside playing and her husband was away. Because the house was so unusually quiet, she was able to hear a small sound, like the crinkling of cellophane. Then, she saw it: at her feet was a very fine pile of sawdust. Her blood went cold as she looked up to the ceiling where she spied the smallest of holes and from it, a small trickle of sawdust. As she suddenly put the crinkling sound and sawdust together, the debate over wine or dessert came to an abrupt end. She poured herself a large glass of wine before she called the exterminators.Her house had carpenter ants.

The next day Rentokil came around and took a look at her roof over the kitchen. The roof is a low-lying flat roof with a green roof for cover. There is a waterproof membrane that separates the insulation layer from the green roof. Unfortunately, to locate the nest the contractor had to pull off the green roof and membrane to access the interior of the roof. Below are pictures of what they found:

I contacted Cris at Rentokil and talked to her about carpenter ants. The homeowner had told me that when they took off the barrier, the interior was bone dry and the waterproof membrane separating the green roof from the insulation was in excellent shape. Carpenter ants like a nesting material that is neither too hard nor too soft which is why rotting wood suits them perfectly. It turns out that rigid foamboard insulation is also the right consistency for the little devils. According to Cris, the ants don’t like batt insulation, or cellulose because they’re too soft and if the insulation is less than 2 inches they won’t go near it either because it’s too thin.

Carpenter ants like old, rotting trees to nest in but once the colony gets too large for the primary nest they will go out in search of new potential nests. Cris told me that nests can go undetected for years because the ants lie dormant in the winter and in the summer they prefer the outdoors so they may never even come inside your home. Often they’re only discovered when it’s time to change windows and doors and old wooden frames are ripped out to uncover a nest. However, unlike termites, which can destroy and entire house in two to three years, carpenter ants only use the wood for nesting, not as a food source.

How to help protect your home from a carpenter ant invasion:
Cris gave me a few tips for helping to prevent as much as possible, a carpenter ant infestion. Taking the steps below can help, but it’s no guarantee that they won’t find a way inside.

  • Don’t store wood piles right next to your house. Weathered wood is a prime nesting spot for carpenter ants.
  • Identify and monitor any old trees that might be on or near your property for signs of wood rot.
  • Trim old tree branches that are close to your house so they don’t provide a path for ants to infiltrate your home.
  • If you have an old deck with rotting wood attached to your house, replace it. If it’s not in the budget to replace it, treat it with an insecticide to prevent an infestation.

After my friend’s experience, I would also add, that if you live in a neighbourhood susceptible to carpenter ants be careful when using rigid foamboard insulation to insulate your home. Carpenter ants need a thick material in which to work, and 4-6 inches of wet, soft wood or rigid foamboard insulation provides exactly the environment.

If you think you might have a carpenter ant problem the way to find out is to go outdoors at dusk and use a flashlight to trace the carpenter ants’ trails in the area you’ve seen them in. They are nocturnal insects and, therefore, are active at night.

Susceptible neighbourhoods are those with plenty of old growth trees such as Forest Hill, Rosedale, Leaside, and Etobicoke. New subdivisions are unlikely to provide a viable nesting area for carpenter ants as the trees are too small and the wood is too hard for them to penetrate.

I also asked Cris if there was any insurance for carpenter ants. Unfortunately, there isn’t.

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4 comments

  1. Randy Campbell says:

    good post i really found it interesting and useful. i myself am now in the middle of a project for the living room. looking forward to your next post.

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