New Stove owner advice needed-air flow

woodwarm · Sep 24, 2014

I want to say in advance that this site has been invaluable. My quick story; i finally realized my dream of installing a wood burning stove in the former fireplace in the center of my house.(main floor) I knocked out rear, opened up sides/top to allow proper clearance and installed a two sided wood burning stove. Yes TWO sided with identical glass doors etc on each side. I am happy to share brand and experience as it entailed purchasing and shipping from across the pond etc. Installed late last year and got to know stove and its heat output(huge) as well as temperatures across main floor and above floor(bedrooms). I learned a lot from this site on proper techniques for burning etc. The purchase of an infrared thermo gun helped me get a good picture of the heat output and its effects on different areas of home. Now in addition to stacking four cords of wood personally(mind altering experience), I would like to fine tune my home to get most out of heat output. My issue is the same as many others; how to get heat up into above bedrooms. My home is a colonial with a staircase near stove area that services above floor and bedrooms.

My observations; when sitting on second step on main floor one feels a rush of cool air at your back. Clearly cold air from above bedroom floor is rushing down to main floor level stove area. This seems to be overtaking any strong heat from moving upstairs into bedrooms. The colder the temperature outside the stronger the wall of cold air coming down stairs. I would like to install vents in ceiling to allow hot air from stove to move up into each bedroom and keep stairway as large return. Perhaps one vent install in main floor ceiling directly below each bedroom. I would use thermo style so as to conform to fire codes.

My question is how to properly size vents and second where to install vents. Should they be close to stove area or further away so as to induce more horizontal flow across the bedrooms(further from location of stove) since stairway is outside of bedrooms and pulling air out and completing cycle.

Secondly,my kitchen is not getting adequate heat because my main floor rooms have decorative headers above openings. Amazing but thermo gun shows 8-10 degree difference on either side of headers.(heat gets stuck against stove side headers. I was thinking of putting in vents on upper wall separating kitchen from living room.

Thank you in advance for feedback and I am enclosing picture of my floor plan for easier understanding of issue. Three bedrooms upstairs..1,2, and 3 shown in dotted lines.

begreen · Sep 24, 2014

What you are describing sounds like natural convection flow. Hot air is already heading upstairs, at a higher height. If you measured the air temp at the bottom step and compared it to the air temp 6 ft above the top step I think you would find a substantial difference. Are the bedrooms uncomfortably cold? If not, I would not cut vents in their floors. A transom vent above the kitchen/main floor room passageways may help. But you could also try moving the cooler kitchen air toward the stove room. That is often more effective.

Do you have a table fan? Here is a trick for distributing the heat. It works quite well assuming that there is a line of sight path between the cooler area and the stove room. The idea is to blow the cooler air down at floor level, toward the stove. For more even heat in the house put a table or box fan in a cooler room within sight of the stove room, placed on the floor, pointing toward the woodstove room. Run it on low speed. It will blow the cooler air down low, toward the woodstove. The denser cool air will be replaced with lighter warm air from the stove room. Running this way you should notice at least a 5F increase in the room temp after about 30 minutes running. And the stove room temp should drop by a corresponding 5+ degrees.

woodwarm · Sep 24, 2014

yes at top of stairway air is warmer(i did observe that), it is just that is it not getting into bedrooms adequately. i.e. If stove is cranking and downstairs 75 then bedrooms can be 62 ish on coldish days..just a bit too cold to keep stove cranking all night for 62. normal days maybe 65. Thinking vents would help close the gap and get me to 68-70 which would be perfect. Transom vents is exactly what i had in mind for wall between kitchen and living room.

DAKSY · Sep 24, 2014

You have the right idea - sort of - but to get the convection flowing will be the trick.
When you cut through & install vents in your bedrooms, they need to be near the outside walls.
HOT air will not rise through them, though.
Those wall are the coldest walls in your home.
If you place the vents near them, the COLD air will
DROP down through when the HOT air comes up your staircase
& the COLD air flow DOWN your staircase will be decreased...
The main problem with cutting through the floors is that it is against most firecodes,
as it gives a direct path to the upstairs, should a fire occur.

madison · Sep 24, 2014

You may wish to contact your twon's building inspector prior to cutting - CO and fire codes may need to be adhered to in your area.

woodwarm · Sep 24, 2014

madison said:
You may wish to contact your twon's building inspector prior to cutting - CO and fire codes may need to be adhered to in your area.

Yes i will check the fire code in town but i am sure its national code that is why i will use thermo swith vents that close upon a high temperature in case of fire below. So would you recommend putting vents near outside walls and further from door openings. This should induce more cycle of flows. Also what do you think is good back of envelop to determine vent sizing. Similiar to soffit vent sizing ratio for attic squ feet? Thank you

DAKSY · Sep 24, 2014

Well, standard cold air returns for hot air furnaces fit into the stud
cavities in 2x4 walls, so I would probably not go any smaller than that.
3.5 x 14.5 = 50.75 sq. in.

Andy S. · Sep 24, 2014

A theory I'm planning to try this season may apply here. The floor fan plan definitely works, but it has not been a whole-house solution for me. There are many posts on the site about using the HVAC fan but most of what I've read (and my own experience last season) shows it to be ineffective.

My plan is to strategically block vents and returns so that the system stays in balance but leaves only the vents in the first floor stove room and the returns upstairs open. The theory is that the upstairs returns will draw air up and the vents in the stove room will force air out. If it works it will create a gentle loop throughout the house, warming the other rooms as it goes.

If it doesn't work I will have kept myself (and my family) entertained running around with my IR and sheets of toilet paper.

Grisu · Sep 24, 2014

Since the warm air seems to be going up and cold air down, heat movement may not be your biggest problem. You may have quite some leaks in the upper floor through which cold air comes inside and keeps the bedrooms from warming up. Did you ever take your IR thermometer and checked the walls and ceilings for cold spots especially around things like outlets, lights etc.? Some caulking, new weatherstripping, and spray foam may just be enough to get the temps upstairs to a comfortable level without cutting anymore holes in the walls. Also: How good is your attic insulation?

woodwarm · Sep 24, 2014

Grisu said:
Since the warm air seems to be going up and cold air down, heat movement may not be your biggest problem. You may have quite some leaks in the upper floor through which cold air comes inside and keeps the bedrooms from warming up. Did you ever take your IR thermometer and checked the walls and ceilings for cold spots especially around things like outlets, lights etc.? Some caulking, new weatherstripping, and spray foam may just be enough to get the temps upstairs to a comfortable level without cutting anymore holes in the walls. Also: How good is your attic insulation?

Its a very good point and one that i am going to address. My main attic insulation is not up to standard. I did the smaller attic a few years ago myself. Removed old, air sealed and installed to R50. I just could not find the time to do the main attic. I will be doing it now before cold weather. In addition, my main floor windows have been updated as they were original wood double hung. Upstairs are "newer" but still 30 years old and single pane A....... Narrow line..They now make a kit to convert it with new sashes to 400 updated standard. I may do or start doing that if its in my budget..11 windows at 330 per. So to answer your question, some percentage of this cold air rushing down is probably due to inadequate attic insulation(attic stair hatch right above stairway) and to a lesser extent the windows. I did do a lot of searching with IR gun and yes around hatch was very bad and some ceilings levels not consistent most likely to due to thin insulation.
So I will push attic insulation project into action and hold off on cutting holes in ceiling etc until that is completed. I will probably go ahead and put transom vents in as they should increase circulation.

Thank you for everyones help and input...

PS I already had researched my insulation plan previously. I will be installing 4 inch double reflection board on walls and and roof joists and making attic conditioned space. I like this strategy vs the spray conditioned space strategy where one sprays under roof decking. The former maintains air flow from soffit vents up and out ridge vent keeping temperature and air flow under decking to avoid and problems with heat or rot.

Poindexter · Sep 25, 2014

+1 on going after air leaks before cutting vents. Two years ago I was losing five degrees per hour when my house was heated to +65dF and the outside temperature was +20dF.

Without adding insulation, just plugging air leaks with caulking and weather stripping and a can or two of spray foam I now lose five degrees per hour with the house heated to +65dF and outside temps are -20dF.

So now my furnace makes as much heat at -20dF to maintain the temp inside the house at +65dF as it used to have to burn to keep the inside of the house to +65dF when exterior temps were +20dF.

In all fairness I started with a house built in Alaska in 1985 using what was state of the art at the time.

Some very good tips about moving cold air along the floors toward the wood stove with garden variety box fans, I haven't had to cut transom vents yet.

Just throwing it out there, I for a while considered building a house with bedroom upstairs, a stairwell at each end of the house and a wood stove at one end of the house very close to one of the stairwells. If anyone has one, does wood ehat flow pretty good in there?

woodwarm · Sep 25, 2014

Poindexter said:
+1 on going after air leaks before cutting vents. Two years ago I was losing five degrees per hour when my house was heated to +65dF and the outside temperature was +20dF.

Without adding insulation, just plugging air leaks with caulking and weather stripping and a can or two of spray foam I now lose five degrees per hour with the house heated to +65dF and outside temps are -20dF.

So now my furnace makes as much heat at -20dF to maintain the temp inside the house at +65dF as it used to have to burn to keep the inside of the house to +65dF when exterior temps were +20dF.

In all fairness I started with a house built in Alaska in 1985 using what was state of the art at the time.

Some very good tips about moving cold air along the floors toward the wood stove with garden variety box fans, I haven't had to cut transom vents yet.

Just throwing it out there, I for a while considered building a house with bedroom upstairs, a stairwell at each end of the house and a wood stove at one end of the house very close to one of the stairwells. If anyone has one, does wood ehat flow pretty good in there?

woodwarm · Sep 25, 2014

Thank you very much for comments. Yes it's time to head to attic....

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