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View Full Version : Heat rises, right?



Charles Wiggins
01-23-2013, 12:58 PM
We added fireplace insert in the finished portion of our basement about a year ago with the hope of reducing our use of natural gas to heat and to have backup heat during a power outage. Right now, the only direct path for the heat to travel is up the stair well which is about 8' away and exits into the hallway on the main floor where the thermostat is located. If we get a roaring fire going and get the room up to around 93-95 degrees F the hallway gets up to about 73-74 and most of the rest of the house stays around 66-68.

Since heat rises, I am tempted to cut through the ceiling in front of the fireplace and put a register in the floor above to allow the heat to rise directly into the room above which is the main living area. I got the idea from my grandfather who did that when he built his house in the '80s.

I have found "mixed reviews" online regarding the success of such endeavors.

There is another fireplace and hearth directly above, where we intend to eventually install a freestanding gas stove for additional heat and to cook on if the power is out for an extended period, but this would just be for "emergencies." If we do the vent, I would cut the hole 8"-12" in front of the hearth and locate it between the joists - no joist cutting! I was thinking of a 12"x12" or 14"x14" register. I would add blocking between the joists and eventually finish the inside of the vent tunnel in the basement ceiling.

Anyone have experience with this? Any sage advice? Any advice on locating the hole from the top side? (The main floor is carpeted.)

Dan Hintz
01-23-2013, 1:13 PM
Make sure your HVAC system has an intake vent both upstairs and downstairs... that can make a huge difference in temp leveling between floors.

Rod Sheridan
01-23-2013, 2:24 PM
I installed a blower and ductwork at my FIL's house to take hot air from the stove room in the basement and deliver it to 2 bedrooms at the opposite end of the main floor.

They're balanced at just under 200 CFM each, and it does a great job of keeping the house temperature more uniform.

They don't have a forced air furnace, they have baseboard electric to supplement their wood stove.........Rod.

Jim Creech
01-23-2013, 2:47 PM
I agree with Dan's response. If you do not have central heat then then do as Rod has done. I had a similar problem except I do have a heat pump and during the winter my fireplace insert would only really heat the one room. This was primarily due to the lay-out of the house. I have two registers in the fireplace room and was able to convert one of them to a return air which, with the addition of an inline blower, was enough to pull heated air out of the room and inject it into the system there-by more uniformly heating the entire house and reducing the "Auxiliary Heat" time.

ray hampton
01-23-2013, 3:11 PM
We added fireplace insert in the finished portion of our basement about a year ago with the hope of reducing our use of natural gas to heat and to have backup heat during a power outage. Right now, the only direct path for the heat to travel is up the stair well which is about 8' away and exits into the hallway on the main floor where the thermostat is located. If we get a roaring fire going and get the room up to around 93-95 degrees F the hallway gets up to about 73-74 and most of the rest of the house stays around 66-68.

Since heat rises, I am tempted to cut through the ceiling in front of the fireplace and put a register in the floor above to allow the heat to rise directly into the room above which is the main living area. I got the idea from my grandfather who did that when he built his house in the '80s.

I have found "mixed reviews" online regarding the success of such endeavors.

There is another fireplace and hearth directly above, where we intend to eventually install a freestanding gas stove for additional heat and to cook on if the power is out for an extended period, but this would just be for "emergencies." If we do the vent, I would cut the hole 8"-12" in front of the hearth and locate it between the joists - no joist cutting! I was thinking of a 12"x12" or 14"x14" register. I would add blocking between the joists and eventually finish the inside of the vent tunnel in the basement ceiling.

Anyone have experience with this? Any sage advice? Any advice on locating the hole from the top side? (The main floor is carpeted.)

a hole saw would work best space same distance from both joists, the hole will enable you to cut the carpet from the basement

Jerome Stanek
01-23-2013, 6:02 PM
You could run the furnace fan to move the air or put a fan at the top of the stairs to blow the warm air to other portions of the house. Also what you had in mind would work that is how the old farm houses did it

Jim Matthews
01-23-2013, 6:13 PM
I try to remember that wood is only free, if I got get it my own self.

Two things to make the heat transfer easier, a pressure gradient and isolation.
If you can draw air out of the space you intend to heat, the convection forces will overcome the stack effect (http://chuck-wright.com/calculators/stack_effect.html).

Otherwise, cold air will "fall" to the lower reaches of the house and the hot air will rise to the highest point.

I installed a series of honeycomb curtains that slide across doorways (a door would also do) like a shutter to keep this effect at bay.

When I'm running my stove, I want the heat to spread through the floor we occupy during the day.
That means keeping the stairwell "shuttered" with an electric fan running to blow air out of the heated space.

John McClanahan
01-23-2013, 6:28 PM
Your local fire codes may not allow for a simple vent thru the floor. A fire could travel up thru the vent, spreading much faster.

John

Mel Fulks
01-23-2013, 7:30 PM
We only had one return. Added one upstairs it it made a big difference.Ive been told that requirements on number of returns varies among the states from one, to one for every room,have not researched it.

Rich Engelhardt
01-23-2013, 7:57 PM
Our fireplace is in the half sunken family room.
Back when I used it to heat most of the house, I just set a fan at the top of the stairs going down into the family room to pull the warm air into the reat of the house.
It worked ok for the downstairs - the kitchen and living room.
Didn't do a thing for the upstairs bedrooms.

Charles Wiggins
01-23-2013, 10:58 PM
Thanks John. Good to know. I'll check on that.

Charles Wiggins
01-23-2013, 11:05 PM
Dan,

If I get all this going properly our HVAC system won't be running, at least not very much. We have a duel fuel system - a heat pump with a natural gas furnace backup. I try to keep things warm enough so the system doesn't kick on, or it does so less frequently, particularly when the outdoor temp goes into the low 30s because that's when the furnace kicks in. Plus, the system is in the attic so there in only one register downstairs in the ceiling of the stairwell, and not return.

Charles Wiggins
01-23-2013, 11:08 PM
Rod,

I'm not sure that would work here without major renovations, but I'll keep it in mind.

Charles Wiggins
01-23-2013, 11:13 PM
I forgot to mention that I did already hang a small fan at the top of the stair well to draw the warm air up into the hall, but I think we'd get more heat in the main living area with the open stack I am proposing.

Jim Matthews
01-24-2013, 6:36 AM
This brings up a secondary concern - what does your insurance company require of you to certify the heating system as safe?

I attempted a similar retrofit in my existing fireplace (drop a liner, extend the hearth, beef up the joist) and the total cost to reach the code exceeded
possible savings from burning wood over fifteen Winters. The last thing you want to find out after a house fire is that your going to court to get the Insurance payment...

Dan Hintz
01-24-2013, 6:38 AM
Dan,

If I get all this going properly our HVAC system won't be running, at least not very much.

Don't you have a fan in the system that can be run without the heater itself being on? You just want to move air, not necessarily heat/condition it.

Charles Wiggins
01-24-2013, 8:40 AM
Dan,

As I said, the HVAC system in housed in the attic, so all of the ductwork is in the ceiling of the main level. There is one output register in the basement stair well and no return, so I don't see how the HVAC system would be very helpful in getting the warm air up from the basement. It might be somewhat helpful if my proposed vent above the wood stove works because there IS a return in the room above.

Charles Wiggins
01-24-2013, 8:43 AM
Again, VERY good to know. I'll check with my agent.

Dan Hintz
01-24-2013, 9:05 AM
As I said, the HVAC system in housed in the attic, so all of the ductwork is in the ceiling of the main level.

Ah, didn't catch that first time around. Hmmmm, is there a wall that you can turn into a return duct? Construction and fire code will vary for your area, but often you can use the stud wall and drywall itself as a return duct... may get you from basement to attic with only some minor rework.

Brian Elfert
01-24-2013, 9:13 AM
Insurance companies can be a pain when it comes to wood heat. I know folks who live in rural areas who have removed wood stoves from their homes as their insurance was going to go way up, or their insurance was going to be dropped. My parents installed a wood stove insert into a masonry fireplace around 1986 and no issues with their insurer to date. They use it all the time to keep the basement warmer. They usually get their wood for free with renting a splitter every few years the only expense.

My parents run their furnace fan 24x7 in the heating months to try to keep the temperature even between basement and 1st floor. It also helps a little bit to distribute heat a little bit when they use the wood stove insert. They close all their basement registers in the summer as the basement gets too cold from the A/C.

Mel Fulks
01-24-2013, 10:53 AM
A good contractor can find a way to run the new return .Ours uses part of a closet ,nothing else is going to work as well as an added return and the fan on.

Charles Wiggins
01-24-2013, 12:05 PM
Well, I checked with my agent and he says it should be no problem. He was aware that some insurers are wonky about wood heat but not Farm Bureau. He is aware of several houses in the area who have floor vents for heat exchange and insurance has never been an issue. I also have a email off to our Building & Construction instructor about the code, so we'll see what he has to say about that.

Myk Rian
01-24-2013, 1:40 PM
Your local fire codes may not allow for a simple vent thru the floor. A fire could travel up thru the vent, spreading much faster.

John
In which case a fire damper would be installed.