Realistic savings and fuel value?

[Poindexter]

Thank you for the response, I'll look into leaving a gap. The house was built in 2010. I came to the need for outside air by the fact that the house is spray foamed in the walls with plastic under the blow in insulation in the ceiling, and despite the HRV and bathroom exhaust fans we struggle to get humidity out in the winter (tough to get humidity below 60%). I don't want to run into draft issues while running a dryer and bathroom exhaust fan for a shower. More than any, I shy away from the idea of pulling cold air into the home through a gap elsewhere, and thus cooling it, to facilitate a draft. Pulling outside air directly into the stove for combustion and out the chimney without entering the home seems ideal, but again I'm new to wood heat.

I can only answer part of this. Spray foam insulation is pretty good stuff. It is expensive, but the install is fairly flexible. Do you know the R value of your walls and ceiling? Somebody somewhere -hopefully- ran an "air door" test or similar as part of getting the HRV set up correctly.

I don't actually own an HRV, but my next house more than likely will have one, I have been reading up. For an air door test the operator should block all the architectural openings, windows, bathroom fan vents, HRV intakes and outlets etc, and then set up a vacuum pump - usually on the front door - and try to pull a vacuum on the house. Somewhere on the report should be a line more or less "Your house is leaky. If it had been built perfectly air tight you could make a hole in the wall ____ square inches to approximate how leaky this piece of junk you put a mortgage on is."

Or words to that effect. I hope the numbers have gotten better. Last time I read up on it, a 100 sqin equivalent leak was considered excellent, once a home got up into the 400-500 sqin equivalent range the homeowner had some work to do. I just can't imagine a hole in the wall of the living room 10x 40 inches, it is an astounding amount of heat loss.

I do struggle to keep my indoor humidity at 10% RH in the winter, and the wife wants hardwood flooring. I frequently see 70%RH in the summer. Is 60% RH in the winter really a problem for you, and why?

Ideally, with an HRV system you would set the wood stove up with an OAK so the combustion air for the stove isn't coming through the HRV filters. If the drywall isn't up yet, you can run an output leg over to near the stove, but you are signing up for more frequent filter maintenance on the HRV filters if you do that.

One option. if you are running the HRV for pollen abatement would be to put a valved air inlet near the stove (above grade), heat with electricity until you have snow cover, then open the valve and run the wood stove. There is a pretty good option for that, available in 80 and 120cfm ratings, but i am striking out. Jiffy 80, Jumbo 120, dunno, my google-fu is off this week.

Could you maybe put the stove somewhere else in the house where an OAK is better suited?

At my current home, I have the upstairs sealed up pretty tight and I heat it with supplemental wood. I do have some air leaks downstairs, I let the combustion air come in through those holes and just go with it.

 

[Poindexter]

Up in post 28 above I spun the wheel on my US Forest Service Fuel Value calculator to 13 cents / kwh and posted a picture.

Here is another one, the top of the scale, $75/ one million BTU. It's just an equivalency chart. Here is another one I can talk about. Like @bholler, I calculate my personal cost for electricty by looking at how many kwh came in and how many dollars went out. The most recent bill I have filed was $106.42 for 390 kwh. I paid $0.27 per kwh that month and I don't give a flip how they justified it on the statement with regulatory this and fee that.

So here is the wheel spun to the top end, $75/ one million BTU:



Notice I am paying even more than that for electricity. The wheel, the calculator has some assumptions in it and I am not saying it is perfect, but it is a handy place to start.

What I see is _if_ my price for one ton, essentially one cord, of dry spruce was $922.40, which it isn't, but if it was, it might be economical for me to rip out my oil burning furnace and put in electric baseboard heat. If I get down to brass tacks I look for 18 MBTU in a cord of spruce, at $75/ million BTU, I come up with a cord of spruce worth $1350 if my other option is to heat with electric at 27 cents/ kwh or propane at 5.39/ gallon.

I know some of you guys were paying > $5/ gallon for propane a couple or three years ago, and that had to hurt a lot.

@begreen , once your keyboard is fixed if you want to pull some posts out of this thread and collect them in a new thread called "fuel value comparison" or whatever I will be glad to participate. It is a fascinating subject to me, mostly because I am a math dork.

 

[Poindexter]

So here is another one while I am warmed up. Last year I was getting green spruce splits delivered for $250/ cord, 2 cord minimum. The guy loads his staked sided dump bed dually pickup with a skidsteer, but his two cords delivered stack out honest. 18 MBTU for $250 works out to $13.88 for one million BTU. All I have to do is stack in time for it to be dry before I need it.



So part of the rub is I was paying $250/cord and drying it myself. Whatever their air dried cord of firewood is, they are only valuing it at $214.90. Not perfect, but pretty close.

If I could get propane at a buck a gallon, or electricity for under a nickel per kwh, it might be time to hang up my wood carrier. I have never got a gallon of #2 fuel for 1.60. 06-28-2018 I paid $3.02/gallon.

For me buying green wood, seasoning it myself and taking the time and effort to run the wood stove basically cuts my #2 oil bill in half. Total dollar savings for me in a "typical" winter is probably only $1000 to $1500, but it is year after year and I would go bonkers just sitting on the couch watching television. I would much rather be outdoors, and $4500 bucks after three years of not buying new chainsaws will pay for a lovely trip to Paris with the wife.

 

[SD Golden]

I usually leave at least the diameter of the pipe gap. The problem and the reson you cant hook it directly is that the air at the outlet near the stove is going to be much warmer than the air at the inlet outside. This means air is going to want to go out of the pipe and not in because of the stack effect. Do you have any door in the basement going to outside?

I do not have a door in the basement, I do have a window about 6 feet away.

Poindexter, we struggle with moisture and mold around windows in the winter with the humidity in the house. Unfortunately I can't speak to the HRV set up as it was installed by the last owner before we moved in. We are stuck with the stove going on the 1st floor in the living room opposite end of the house the HRV is on due to the layout of the home, unfortunately. If we had more room in the furnace room I'd love the idea of a wood add-on furnace, but it just won't work.

 

[maple1]

I do not have a door in the basement, I do have a window about 6 feet away.

Poindexter, we struggle with moisture and mold around windows in the winter with the humidity in the house. Unfortunately I can't speak to the HRV set up as it was installed by the last owner before we moved in. We are stuck with the stove going on the 1st floor in the living room opposite end of the house the HRV is on due to the layout of the home, unfortunately. If we had more room in the furnace room I'd love the idea of a wood add-on furnace, but it just won't work.

It sounds like you have a really really tight house, or there is excess moisture coming in somehow (e.g. open sump pit), or the HRV isn't doing it's job or wasn't designed right. Usually, wintertime finds people doing the opposite & having to add moisture, due to the drier outside air & air infiltration from stack effect.Also moisture condensing on cold windows isn't always a red light - sometimes it is a sign of a really tight house & windows that doesn't promote air movement across windows that would prevent the condensation. That air movement can also come from rads or air ducts/registers being located below windows. Or HRV inlets/outlets close by. Is your HRV ducted to each room? Or does it only have one central inlet & outlet?

 

[bholler]

I do not have a door in the basement, I do have a window about 6 feet away.

Poindexter, we struggle with moisture and mold around windows in the winter with the humidity in the house. Unfortunately I can't speak to the HRV set up as it was installed by the last owner before we moved in. We are stuck with the stove going on the 1st floor in the living room opposite end of the house the HRV is on due to the layout of the home, unfortunately. If we had more room in the furnace room I'd love the idea of a wood add-on furnace, but it just won't work.

But i assume the window is still way above the level of the stove. If you had a door even if it was in a well that area is a good spot to pull air from.

Another consideration is how are you going to get wood to the stove without a door to the basement. I personally would not heat with a stove from the basement without direct access to the basement from outside.

 

[Highbeam]

Humidity. You want under 50% to prevent all kinds of nasty bugs and molds. You measure the humidity with a gauge. Condensation on windows is not necessarily a sign of a humidity problem, just a sign of a cold window.

We run about 60% in the summer indoors and I would like to drop that to 40%. The gauge bottoms out at 16% for most of the winter and I can still get condensation on a beer bottle.

 

[Poindexter]

Was the HRV put it in during new construction or retrofitted?

My hunch is retrofitted...