Gas and Oil Home Heating Furnaces - heat pouring into basement crawlspace

Please Help!
We have 2 furnaces heating our home. Attached to both at the junction where the furnace is emptying into the ductwork (plenum?), are ducts which just let the warm air pour into our crawlspace. This makes the crawlspace, and the room directly above it, unbearably hot, while other rooms can be quite cool. What I would like to know is what is the reasoning behind these ducts, and can we seal them off. Our furnace system is approx 13 years old.


Thank you!

Hello Bill. Welcome to the Heating and Cooling Appliance forum and the Do-It-Yourself Web Site.

We may have a wording terminology conflict here.....{???}

My assumption here, based upon the information your providing, is your house has two furnaces, two individual thermostats each operating it's own forced warm air heater and each heater is providing heat to two areas of the house independingly.

That being the case thus far, your house is either a multi-level home or is a single story large square footage house.

Regarding the crawl space:

If the area is a true crawl space, the house then has a raised foundation. If the crawl space is more then about 3 feet high and a person can walk around in it and not just crawl in that area, then the area currently being heated may not have been a crawl space in the past.

This may be the reason why some part or all of the ducting from one or both heaters is allowed to heat the area. The area could have been living quarters at some time.

If both heaters do in fact having ductings to rooms and the area beneath the house is a true crawl space area, then the ductings may have become disconnected accidentially or for some unintentional reason.

Depending upon which above applies, the ducting and or ductings that are not connected, should be reconnected and not blocked off.

Regards & Good Luck
Gas Appliances Forum Moderator
Tom_Bart...........Fast, Fair, Friendly & Highly Efficient.....:)
Energy Conservation Consultant & Natural Gas Appliance Problem Diagnostics Technician.

Hi Tom:

Thanks for the quick reply. Yes, you are correct that we have a large, two storied house, with two independant thermostats heating two seperate levels.

The crawl space that I talked about is not a true crawl space. It is approx 5 feet high, but was never developed or used as living quarters, but probably storage. These "ducts" were definately put in for some reason, but appear to have never been connected to anything else. I should also let you know that this area also has two "true" ducts that are properly connected with register grills attached.

The main reason this is a concern to us, other than the hot temperatures is that the house takes 1 - 1 1/2 hours to heat up in the morning. We live in Canada and set the nightime temp to 65, and daytime to 70. It is our experience that this is way too long for the house to heat, and my guess is that if we blocked the ducts in question, we might end up with more heat to the rest of the house.

Any other thoughts?

Thanks again!

Hello: Bill

Based upon this newly provided information, if the area, in your opinion, that does not require any heating and providing the blocking [closing off} of the ducting in question will not be be blocking off the entire ducting for this heater entirely, you can proceed as intended.

However, consider that totally stopping all heating in the space, doing so may have some unthought of negetive effects in the space. Mold and or mildew build up, as an example. Dampness to any item stored in the space, as another example.

The positive effect would be providing more heating air volume to the living space, faster home heating, reduced fuel useage all resulting in lower energy costs.

I suggest you only block off the ducting in this area in a temporary test manner in order to determine the final results over an entire season. If no negetive results become evident, closing the ducting permanently could be done.

Regards,
Gas Appliances Forum Moderator
Tom_Bart.........TCB4U2B2B
Energy Conservation Consultant & Natural Gas Appliance Problem Diagnostics Technician.