Heat transfer

[coldironkilz]

My house is essentially a four story house. From bottom to top; daylight basement, main floor, second floor, attic (7 1/2 ceiling). A bedroom on the second floor extends out over a deck which causes that room to be very chilly in the winter months. The wood stove is located in the daylight basement. The woodstove uses ambient air (inside) for combustion. I want to move more warm air into the chilly bedroom by way of a vent pipe (the chilly room and the stove are on opposite sides of the house). I want to install the vent pipe from the chilly room at floor level, exit the room via an outside wall, travel down the outside wall through the deck, then travel under the deck the length of the house, make a 90 degree turn, travel the length of the west wall re-enter the house in the basement at ceiling level traveling down the inside wall to approximately one foot above the floor next to the base of the wood stove. Do I have a problem? Is there an aspect of natural heat transfer that I am missing? Will the exposed pipe (outside) be too cold to allow for the air in the bedroom to effectively transfer to the basement?

[Steve Sells]

the outside will get very cold, have you taken that problem into you plans? Also why take of near the floor, the ceiling  will have mroe heat available.   Be aware many places require a HVAC permit for it. and code may not allow it,  please look into it your local building dept,

[DSW]

You loose heat based on surface area. With a run that long my guess is you will loose any heat gain due to the surface area of the duct work outside unless you super insulate it. It's been way too many years since my HVAC and insulation classes, but there are formulas that figure heat loss based on surface area, interior and exterior temps and R value.

 

I think you would be better off insulating the underside of the bedroom vs trying to insulate the duct work to retain any heat. Spray foam comes to mind as the easiest and most efficient way to solve this issue. 1" of spray foam is equal to an R 6 to R8 depending on the foam company. 2" of spray foam gives you as much or more insulation than 3 1/2" of good fiberglass. Filling an 10 to 12" floor bay would be equal to almost 24" to 30" of fiberglass. I'd look at opening up the sofit under the room outside and pulling out any insulation and foaming it myself. I just priced out a kit from Tiger foam. R value is R7 per inch IIRC and kits were $330 for 200 sf 1" thick or the bigger  kit 600 sf 1" thick for $600 just to give you an idea on cost.

[vapremac]

I am by no means an HVAC tech but IMHO I do not think this would be a very effective/efficient
method of transferring warm air.
Maybe if the pipe had some sort of insulation wrap? What about ceiling/floor vents to let the heat rise?

[Glenn]

A bedroom on the second floor extends out over a deck which causes that room to be very chilly in the winter months.
 
The woodstove uses ambient air (inside) for combustion.
the chilly room and the stove are on opposite sides of the house

There are 3 issues here. The bedroom is exposed on at least one side and the bottom. Insulation is the way to go in my opinion. Start with under the floor and put in as high a R value insulation as possible and a cover to keep the wind out. As to the outside wall(s), you are limited to adding insulation and or a wind break. 

 

If you pipe in outside air you will save heating all the air you send up the chimney, which is considerable. Look at the smoke coming from the chimney and that is how much heated air you are sending OUT of the house. The outside air (at outside air temperatures) then comes in via cracks etc to replace the exhausted air. The outside air is at outside temperatures and must be heated to room temps lowering the efficiency of the stove.

 

Once insulated the bedroom will be warmer.  

[coldironkilz]

Hey everyone thank you for your responses. I am afraid I am a little embarrassed ok a lot, seems I didn't explain my plan as well as I thought I did, let me try again. The vent pipe is intended to be a cold air return which is why I thought it should exit the bedroom from floor level (the coldest level of the room). If the stove uses ambient air for combustion and it draws much of that air from the cold air return then in theory, I should be establishing a circulation of air, the cold air from the bedroom delivered to the stove in the basement via the cold air return (pipe), hot air radiating from the stove making its way to the bedroom via the stair well and floor vents then back to the stove through the vent/pipe. Also that room is insulated to an R-30 (ceiling, walls and floor including Tiyvek vapor barrier). 

[DSW]

. Also that room is insulated to an R-30 (ceiling, walls and floor including Tiyvek vapor barrier). 

 

 

I'm impressed. You need to have quite a thick wall to have an R 30 rating on a wall. Walls and windows are usually the biggest heat loss areas if you insulated the ceiling and floor well. Yes I'm poking fun at you just a bit... :P

 

 

The idea of using room air to feed the furnace might work to drive circulation, but don't count on gaining any "heat" from that air. My guess again unless it's super insulated, that the "room" air temp won't be significantly warmer than outside air temp by the time it reaches the furnace traveling all that way outside. Problem is going to be that the "room" air will go up the chimney after it's used in the furnace. That means you need to replace that air with something else. Now in theory you have a partial vacuum  in the house, so the system will want to suck in cold air around any gap or crack. Gaps and air leaks around windows and doors usually account for the vast majority of heal loss in most semi well insulated homes.

 

If you really want to warm up the room, 1st thing I'd do is get someone out to do an energy audit on your home. Get an independent guy to come do it. They work for you and don't have an agenda to push like new windows etc. Most of these guys have thermal imagery. They can quickly show you where your house is loosing heat. It could be from leaky windows or if you windows are top notch, maybe the air leak is from around the window. ( One of the reasons I'm not a big fan of "replacement" windows. The window may be well sealed, but you are still relying on the old frame and the leaky connection to the house.)  With the increased interest in "green" living and 5 star energy homes, there are plenty of companies out there that will help you pinpoint where you need to work on your home to cut heat loss.

[arkie]

Would a wall-mounted, vent-free propane heater be feasible?  That would of course require installation of a small propane tank and piping for that purpose and may not be cost effective for your needs.

 

Lots of houses and cabins in my neck of the woods have wood-fired heaters for the main rooms, but in REALLY cold weather, the wall-mount units get the bedrooms warm when needed.

[BIGGUNDOCTOR]

You may want to look into a radiant heater such as Austraheat(sp?), or Redwell. My German buddy represents these companies. They are 110v, and very energy efficient. They hang on the wall like a picture.

Heat naturally rises, so a basement wood stove may only need some fans strategicly placed to accomplish what you want.

[coldironkilz]

Nobody mentioned the cold air return which is the single aspect of greatest concern. Might it be so cold (outside)that I inadvertently create a reverse draw?