How do I improve heat flow to my upstairs?

Lara Hickerson
by Lara Hickerson

We have a charming old farmhouse (built in 1900 and remodeled in 1950 and again in 2016). We have a natural gas furnace, but no ducts, so it just spews hot air into the great room. It works well for heating the downstairs because it’s all one room. To get the heat upstairs, all we have is a single gravity vent in the downstairs ceiling/upstairs floor. Between the floor is an 18-in crawlspace that eats up all the hot air so it never makes it upstairs. We’re looking for a cheap and quick solution we can do ourselves that doesn’t require replacing the furnace or adding an HVAC system. So any information on how to keep a house warm without central heat and improving the flow of the heat throughout the house would be appreciated.

Furnace and downstairs gravity vent
Downstairs gravity vent
Upstairs gravity vent
  9 answers
  • Rymea Rymea on Nov 27, 2019

    There are several different kinds of electric fans for heating vents. You need install an enclosed vent that goes through that 18" space between the ceiling and the upstairs floor with an electric vent fan inside.

  • Laura Cooper Laura Cooper on Nov 27, 2019
    Lara, I work in HVAC. Unfortunately, this problem really doesn't have a cheap solution. There are a few things you can do to improve your comfort, though. #1 You could try putting a duct fan in the one gravity opening to draw heat up. I'm not sure it will fit as I can't really see details. #2 use a space heater upstairs. The oil filled space heaters are reasonably safe as well as small ceramic ones. Avoid using any that have exposed elements
    • See 1 previous
    • Laura Cooper Laura Cooper on Nov 28, 2019

      From your description, I'd say yes. As some others have suggested, I would use duct board for this project. Also, you can buy a substance called mastic. It's a water based duct sealant that is kind of a cross between a paint and a putty. Use it very liberally to seal any gaps and cracks in your duct areas. I usually use foil tape first and then mastic over the foil tape. You're just trying to direct air and prevent loss into unnecessary areas.

  • Oliva Oliva on Nov 27, 2019

    Have you used your ceiling fan on a higher speed, to divert the heat to adjacent areas? The blades should spin clockwise, during winter months, to preclude heat rising to the ceiling.

  • Allison Allison on Nov 27, 2019

    If I'm understanding correctly, most of the heat passing through the ceiling vent is going into the space between floor? If so, I would fashion a duct from insulating foam board. This can be done through the floor vent, so not ladders. All you need is a tape measure and razor knife. If there is nothing to attach it to, you can duct tape on the corners to make the rectangle. The rim of the ceiling vent will hold it up.

    As Olivia stated, use that ceiling fan. It will move the air enough on low speed to get it through the vent. If you have another ceiling fan on the second story, turn that on low, as well. If you don't, a small box fan over the vent will pull the warm air up but won't circulate it as much as a ceiling fan will. May be worth the investment. Second hand shops always have them.

  • William William on Nov 27, 2019

    You have the right idea with a small section of duct between the two vents. But sheet metal would still absorb some of the heat and radiate into the crawl space. A wood chase or foam board chase would work better. Insulate the warm air from the crawl. Another thing to consider is see if there is another location to add another vent to the the upstairs. As soon as you can afford a new ducted system do it. You do have a hazard there. If there was a fire on the first floor the vents would act like a chimney and pull smoke and flames up. If there was a fire on the second floor air would be pulled from downstairs and feed it. Just FIY and not wanting to frighten you. My daughters rental home had the same situation and she lived there for over 8 years.

  • Lifestyles Homes Lifestyles Homes on Nov 28, 2019

    Here is an example of an in-line fan that comes in different sizes. This is an 8” diameter one.

    The challenge is to supply a to-Code electrical outlet.

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  • Toni @ Girl, Just DIY! Toni @ Girl, Just DIY! on Nov 29, 2019

    I agree with creating a duct within and between the two vents. They sell fans that can go inside ductwork to push heat or cooling into different sections of the house. I would try that option. Make sure whatever you build is well insulated and that you use the metallic tape to seal all edges so none of the heat escapes into that crawl space. Good luck!

  • B B on Nov 30, 2019

    I would put a between floors especially if you have two stair landings an old fashioned floor vent with a hood on the second landing. My stair vent comes from my pantry . I leave this vent open all night the heat feels very central when I come down stairs.