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Insulating Ceiling in Crawlspace

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Posted by: from Blezard Valley
11/29/2021 at 9:23:49 PM

My house is a bungalow style. There is a side entrance with a bathroom on the same level.

The room below is my crawl space which we use as storage, there is also a sump pump in that room. The room below is insulated on the 3 outer wall however the ceiling is not. The floor in there is concrete.

I live in Northern Ontario, Canada. The floor in the entrance and the bathroom are always cold and the bathroom is usually 2-3 degrees colder than the rest of the house.

I want to insulate the ceiling in the crawl space, which should help out with the cold floor above. Should I also put a vapour barrier?

Hope someone can help me out.

Thanks in advance!

REPLIES (4)
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Dennis from Custom Touches in Winnipeg
Date/Time11/29/2021 at 11:47:55 PM

Your real issue is heating. I would never recommend insulating the floor.

Firstly it is normal for the floor to be cooler than the room temp cause cool air falls. Hot air rises. I would recommend running a heat duct into that space below. The warm crawl space will automatically warm your floor above. You may need to shut down other ducts partially to force more air into the crawl space.Return air is important in the crawl space as well.

Also yuo need to be sure you have enough cold air return from your washroom which means undercutting your washroom door if it is too close to the floor.

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Ian in Edmonton
Date/Time11/30/2021 at 4:31:40 AM

Crawl spaces can be unheated & vented to the outdoors (1:150 ratio) or heated allowing the venting to be eliminated, providing your furnace has the proper fresh air intake.

Problem is there may be soil gases, sump or other moisture in the crawl space that you may not want circulating. Older homes may not have the sealed 6 mil poly beneath the concrete or a sealed sump installed like newer homes. Radon (an odorless gas) attaches to moisture moving from the ground to the air; depending on where you're located this may or may not be of concern.

To answer your question a vapor barrier is supposed to go on the warm side of the insulation, idea being to avoid possibility of condensation on the vapor barrier or within the insulation; homes with unheated attached garages will typically have this detail, usually without any problem. However when i worked for Alberta New Home Warranty I once witnessed a home with bedrooms over the garage where condensation occurred towards the front of the garage resulting in drips and water damage to the truss.

Unless the temps in the crawl space are approaching freezing there shouldn't be problem with it being on the warm side; might want to start with a small area to measure the effectiveness of the idea. Another thought is to use a small electric heater in the crawl space during the most inclement weather to improve comfort and keep the crawl space dry.

If installing insulation and vapor barrier in a confined space like this suggest you use a good quality dust mask.

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Dennis from Custom Touches in Winnipeg
Date/Time11/30/2021 at 2:14:26 PM

Just adding to my previous comments. You already have insulated exterior walls (with vapour barrier I would hope). You have a concrete floor. Treat it just like another room in your house. With proper ventilation (hot and cold air supply and returns) there is no reason for fowl doors. Odours may occur only if the space is isolated without ventilation. There is no reason to treat this area differently than any other room in the house.

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Date/Time12/3/2021 at 5:51:38 PM

I have a crawl space with insulated walls and dirt floor. I do not have yuor issue as I have my heat ducts in crawl space, odors are usually only a little mustiness but I have summer vents so that fixes that. You space is likely not ventilated due to the pump in area or has vents that can be opened or closed as it would freeze the sump?

Here are some ideas & Solutions:

-1st determine if it is vented or not?..if yes then close them up in winter, end of problem.

-if there is a "heat run" in the crawl space? install a "t" in it with a vent door on it and end of problem, adjust the little door to let how much heat you want in space. If no run see if one can easily be extended from a existing one nearby

-insulating a crawl that is part of a house will not get much effect insulating the floor if exterior walls are properly insulated, however it will not hurt.(I did this in a small addition oi built attached to a house and also ran a heat vent into it from the house). Since you have a enclosed crawl space including a concrete floor you only need a vapor barrier on warm side "more to hold the insulation up", good strapping can be done and no plastic too.

Smells: ok you should have "No" smells with such a space as described...they are coming either from a dried out sump, a sump that has long standing water in it (you should run/test your sump twice a year)...or you have a plumbing line in area that maybe is starting to rust through if its the old cast lines. If not any of these then you have a smell coming from a source other than the house? construction.

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