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I have several problems with fireplace heating and science of circulating its heated air.
We hail from Edmonton Alberta and have built a new home. Basic floor plan for main floor is 60 x 40 foot rectangle with 9-foot ceilings broken in the middle with a cathedral ceiling and loft over bedrooms. (See diagram)
House has R2000 standards plus what I could add to beef up the specifications.
– 2” Styrofoam under slab enveloping whole of exterior foundation up to attics and cathedral walls.
– 3” of bead board for exterior acrylic stucco application on top of the 2” Styrofoam.
– R90 in cathedral (blown) and attics, Wall cavities of 6” blown insulation.
– All OSB and studs sealed with several cases of foam in a can prior to insulating., all window openings and vents sealed with foam.
– Very few openings in vapor barrier on exterior walls, etc, etc.
One of my concerns was the 1/3-2/3 rule for dew point in wall cavity but so far seems to be okay. I’m committed now; so unless there is an easy fix don’t tell me. Oh okay, tell me any way and put me out of my misery.
I admit to a propensity of windows in the walls but hopefully the future will allow me to design some sort of automated heat shield curtain to keep cold air out in the minus 30 degree nights. (Who am I kidding?!!!)
Heat supplied by natural gas boiler (Burnham-200, 000 BTU) with a fan coil and basement hydronic zoned heating. I want to do water coils on the main floor but ran out of time before we had to get in the house. Maybe when I retire I’ll do “Gypcrete” or alternative. (In my dreams)
There is also a cold air return in the living room.
The GOOD(hopefully the firebox unit);
The BAD (the amount of time spent finding the unit),
The UGLY (me even before the install issues).
After exhaustive research I finally settled on a fireplace that was rated for 80,000 BTU, (actually it comes in February 15/02 so if there’s a better model out there I’m all ears).
– Has two 7” top warm air vents (Both for gravity feed or a combination gravity and hookup to main plenum).
– Fresh air intake with a heat activated spring vent.
– Fan options include one for room the fireplace sits in AND/OR a main plenum feed.
– One optional fan is a 3 HP squirrel cage that mounts with a rubber hose assembly to main plenum.
– The other optional fan is a smaller kit designed to turn on to heat main room.
Now I figure to put the air intake in the gray-water (water from roof) cistern room that is built in the basement hoping the air won’t be so dry after heating. Air in the lofted room is circulated with a slow speed (56”)fan on a manual rheostat
We live on an acreage; at last count 25 cords were stacked out under tarps. Does any one wish to come over and help me chop it up?? I’ll supply the axe. (Okay and maybe dinner with a couple of cold ones too)
Okay on to my questions.
WHAT SAY YOU???? (Objecting Informed Opinions Welcome,)
Do they make fans with a reverse and a remote control that can hook up on a single 14/2-power configuration?
Will I have enough heat left in the 7” insulated duct going to main plenum to justify turning on the fan to circulate air. (20 foot run)
I understand that using both fireplace fans at same time unlikely, but would like main floor warmed with wood in the evenings.
The fresh air vent is controlled by a spring that reacts to warm air in firebox. I have heard that they breakdown over time. I hope to alleviate that problem by installing in basement so it can be changed out without ripping out an exterior wall.
Unit to be installed in an insulated chase flush with interior wall surface. Maybe I’ll bump it out 6” to create some depth on the inside.
Is the electricity draw just to push the heat out costing me more than the heat itself? (See also running the roof fan)
WHAT AM I MISSING???
My wife bet me that I wouldn’t get this unit in before the warm weather arrives, help me pleeeeeeeeeeeeease.
Signed; Kayne (Always looking for a better way, to the detriment of my fast-track projects) Kempton
[email protected]
Sorry diagram doesn’t seem so fit in this format.
Replies
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Kayne: Wow! Someone with more insulation than I have! Sounds like your air-infiltration might be as low as mine as well. You do not need a lot of heat to this house warm. Therein lie my concerns and comments:
I'd estimate you need a max of 30,000 net BTU/hour to keep this place at 70F when it is -40F outside. If you've had a authoritive heat demand calc done, tell me about it and we can discuss.
So the NG boiler will turn on and off a lot. Does it also generate domestic hot water? Not that that adds much heat load.
And the wood stove will have be throttled down to avoid baking you out of the house. Mass inside the insulation (mostly drywall) will help moderate the temps somewhat, but you have such low heat losses, that adding lots of heat brings the inside temperature up quickly.
I kicked around a wood stove (nice focal point to living room, cozy, free wood on our 13 acres) but the cost savings was piddly ($1-2/day) for going to all the hassle of burning wood and the difficulty of running the wood stove at a low enough output.
You and I have the same problem as my dog mushing friends who live in Kyzinski cabins - where are the 10,000 to 20,000 BTU/hour stoves (that's 2 to 3 pounds of wood per hour). At least those little POS shacks eventually cool off due to the poor insulation and sealing. Our tight house take 12 hours to cool off again.
At least for me, running a 3hp electric motor would cost me more per day than all the NG needed to heat the house. Does it double as a whole-house vac system :-)
Seriously, revisit your heat loss calcs and consider if you want to throwing that much heat into a very energy efficient house. One reason for going to such great lengths to achieve your low heat losses was that you would not need such big heaters (wood or NG). -David