Attic moisture and carpenter ants!

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Attic moisture and carpenter ants!

Post by Iwilson » Sun Jan 06, 2019 6:06 pm

Hi, here is some history:

We have a 1944 house in Canada. The upstairs contains some living space (bedrooms) under the roof and some small attic areas: one large attic area on the south side and two smaller corner attic areas on the north.

The attic areas have little ventilation. The roof was re-shingled about 8 years ago. There are only a few passive vents. I tried to improve the ventilation on the large south attic area by cutting some venting at either end of the house and installing a screened cover at each end. The two small corner attic areas only have one vent each

About 10 years ago we installed fiberglass insulation in the attic. There is insulation against the inside walls and on the floor of the attic. No insulation on the outside roof surface

Last spring when the weather started to warm up, we started to see some carpenter ants Inside one corner of the house (one floor beneath one of the small attics). I tried to figure out how they were getting into the house and thought they were eliminated, but this winter we are seeing a few ants again

I inspected the small attic near the ants and there is lots of moisture condensation on the inside of the roof surface. It appears that warm moist air from inside the house is condensing against the inside of the roof. I saw very little evidence of mould or decay (and no ants) but didn’t do a very thorough inspection

Any suggestions appreciated! Do I need to improve the ventilation of the attic areas? (More vents?). Any suggestions on the ant problem?


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Re: Attic moisture and carpenter ants!

Post by A. Spruce » Sun Jan 06, 2019 7:15 pm

I don't think that your ventilation issues have anything to do with the ant issues. If you want to improve ventilation due to excessive heat build up, go for it.

As for the ants, I can't say what attracts carpenter ants, I'm used to dealing with what are essentially sugar ants, which are attracted to sugar/food sources. For this type of ant, borax works well to abate them. With carpenter ants that are going after wood sources, borax will certainly help, but unless they are drawn to a food source (sugar or protein depending on season), it's going to be hard to bait them. You can treat affected areas with borax, which will kill and drive them out of that area, but without baiting their food source, you're not going to kill the colony or eradicate them from the house.
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Re: Attic moisture and carpenter ants!

Post by Shannon » Mon Jan 07, 2019 9:57 am

It is common for these areas to be ventilated using gable style vents ,which may be what you have used? Maybe increasing the size will help? Also stopping the warm are from transferring into that cold space will help. Is the floor space in those areas insulated , and if so with what type of insulation? Because that area will have no air/vapour barrier (unless it has a recent remodel) even with most types of insulation in the floor you will still get the transfer or warm moist air. So unless the area has a air/vapour barrier on the ceiling below or is insulated with closed cell sprayfoam you will get that warm air movement into there. Adding some turtle vents lower down the roof above these areas will help also.

As for the ants , it is hard to say exactly where they are coming from. Ants will leave behind a scented trail once they have a place they what to go. This trail helps them get back and forth to those areas again and again. Eliminating he ants and keeping them gone maybe harder then ventilating this roof area i'm afraid?
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