Insert room remodel w/ pics & HVAC return question

[michaelreinard]

Hi all.

My insert is on the first floor/basement which is about 30-40% underground. The walls are studded and insulated and I am in the process of replacing the paneling with drywall (among other things). This 700-800 sq ft area has an open staircase leading into the main living area. In another post (https://www.hearth.com/talk/threads/77024/) I contemplated using a fan and duct work to pull cold air downstairs and let more hot air rise up the stairwell, but as you work you can’t help getting new ideas.

Check out the pics.

See the soffit directly above and to the right of the stove? Right above the PBR can that the light is magically drawn to. That leads right into the return of the upstairs HVAC system (which is right behind that wall and inside the insulated envelope of the house).

What do you all think about putting a couple of registers into that soffit so the heat can penetrate into the soffit, fill the empty space between the floor and ceiling, and be recycled by the HVAC?

There are code issues with having returns within 10 ft of a stove. Assuming I install a $50 fire damper like this one ((broken link removed)), do you think I am still up to code.

BTW, my chimney is 25ft w/ a 6†SS liner, so I have a great draft and I’m not worried about CO, but I would probably get another CO meter or 2 w/ this configuration just to be safe.

Thanks for your feedback!

Mike.R

 

[fdegree]

What do you all think about putting a couple of registers into that soffit so the heat can penetrate into the soffit, fill the empty space between the floor and ceiling, and be recycled by the HVAC?

There are folks here that have more experience and knowledge about the abilities of recirculating warm air that gathers at the ceiling. But, here is my opinion...I doubt you will experience the results you're hoping for.

That warm air at the basement ceiling will mix with the cooler air from the other return registers when the HVAC fan is running. This mixture will result in an actual air temperature less than the basement ceiling air, and greater than the other return registers.

For example...lets say the air at the basement ceiling is 85°F, and the air from all other return registers in the house averages 70°F. Now, lets assume the HVAC fan will be getting 40% of its air from the basement bulkhead registers that you are proposing, and 60% of its air from the other return registers throughout the house. This mixture will result in an actual mixed air temperature of 76°F { this is determined by -- (85°F * 40%) + (70°F * 60%) = 76°F }. Hardly warm enough to be worth the energy of running the fan. In fact, it will probably feel drafty.

I hope I explained this so it makes sense. I'm sure others will chime in soon.

 

[michaelreinard]

Thanks fdegree. I never thought about it that way, but your analysis makes a lot of sense. I read a lot about recirculating air with the HVAC on the forum and it I recognize it's a mixed bag. I've read that those that have had success are the ones that have the HVAC unit within the envelope of the house, and that's my case.

I wasn't clear in my first post, but actually I never intended to just run the HVAC fan without the heater on. I am hoping that opening the soffit to the hearth room will:
1. Allow some heat to rise up through the HVAC returns;
2. Allow some heat to fill the dead space between the basement ceiling and living room floor; and,
3. Allow some heat into the HVAC room and chase and give the HVAC warmer return air to begin with which I think would improve efficiency when it is running.

My motivation comes from a friend that has a stove in his basement. His basement is unfinished with no insulation but his floor joists are open and the heat makes its way upstairs very nicely. You can see on the new photo below where I would like to put the registers w/ fire dampers. So my questions are:
- do you think this will help move more heat upstairs at all?
- do you think the location of the registers here are sufficient/best?
- do you think including the fire dampers in the registers takes care of that pesky code issue?

I should note that I am not trying to use the insert as our primary heat source. The basement will be a primary living space (when I get done with it!), but the Osburn 2400 has big a 3.2 cu ft firebox so I would like to share a bit more of that heat with the upstairs and cut back on the natural gas bill.

Thanks!

Mike.R

 

[fdegree]

I think I understand what you are trying to accomplish. It may help. Without knowing more about the rest of the HVAC system, it's hard to say for certain. Although, there are more knowledgeable people on this forum, than I...was hoping to hear from them by now.

So my questions are:
- do you think this will help move more heat upstairs at all?

When the HVAC fan is off, there may be a little migration from the basement ceiling, through the return duct, into the upper floor space. Some of that action may depend on how frequently the HVAC fan cycles on and off. Every time the fan comes on, it will remove that warmer air from the duct, and cool the duct back down a little. Just because it will be pulling the cooler air, from upstairs, through this duct.

- do you think the location of the registers here are sufficient/best?

I would say the locations are as good as any

- do you think including the fire dampers in the registers takes care of that pesky code issue?

I honestly don't know. I'm not too familiar with those codes.

----------

Another thing to consider is how this will change the air flow characteristics within your entire home...especially if this duct work is used for cooling during the summer months. A certain percentage of your overall return air will be drawn from the basement, and the air that is being pulled in through those basement return registers has to come from somewhere...most likely it will be drawn down the stairs from the upper level. During the winter, this may not be a terrible thing. It may pull the air down the stairs in a similar fashion as a fan placed at the top of the stairs, blowing down. But, during the summer, you may be pulling the cooler air, at the floor level of upstairs, down into the basement...that may not be a desirable thing.

Again, without knowing more about the entire system, some of my observation may be way off base.

 

[michaelreinard]

Thanks again fdegree. I was planning on using wall registers with louvers so I can shut them when I'm not running the stove, so hopefully that will mitigate side effects. However, if there does seem to be an issue in the summer time I think it will be easy enough to screw off the register and stick a piece of insulation in there for that time period.

If anyone else in the forum has any suggestions I'd be interested in hearing them, especially if related to whether or not putting a fire damper in all three vents will mitigate the safety/code issue of having one of the three returns within 10ft of the stove insert.

DISCLAIMER - I'm not trying to use the forum as a substitute for professional legal, insurance, safety advice - assume that I will contact the appropriate authorities when it comes to these things. I'm just hoping to get some opinions on what might be helpful/feasible, or perhaps hear some alternative ideas.

Thanks,

Mike.R

 

[KB007]

The thing about using yor HVAC system with wood stove heat is the heated air is not really that hot (compared to what your furnace is creating). Thing is, when you start to move hot air it starts to cool. The faster you move it, the more it cools. I tried this approach with a basement stove and I honestly believe I spent more money running the furnace fan than getting any heat value out of trying to distribute the stove's hot air. I'd suggest you look more at moving the cold air into the room with the stove and allowing to hot air to move naturally, thus not cooling as much as it travels.

Just my 2 cents...

 

[michaelreinard]

All of those 2 cents add up to something eventually! How many posts have there been on Hearth.com? At 2 cents each that is probably a respectable sum.

Yes, I have read enough posts about folks having no success in moving heat with the hvac fan, so I'm not counting on it. I plan on putting a floor fan underneath the open stairwell to blow the cooler air that falls town toward the stove. I think it will work well and with my configuration the fan will be out of the way.

I had a more complicated scheme for bringing cold air down from the upstairs by way of a fan and duct in this post (https://www.hearth.com/talk/threads/77024/). However, after reading more and more hearth.com threads and thinking about it more I don't think it will be worth the effort (as cool as it would be to build). What convinced me was an argument about fans where someone explained how big fans moving slowly move more air more quietly than those inline fans where you have the little jet turbine inside a 4" pipe.

 

[snowleopard]

While we're waiting for the more knowledgeable people to turn up, I'll chime in [throws tuppence in the pot].

Last winter I became, what seems in retrospect, a little obsessional about this subject. My expectations for the stove were as a space heater, chill-chaser, supplement-to-oil-burnerer, just-in-caser. My little parlor stove ended up stepping up and heating the whole place when said oil burner failed spectacularly. It was surprisingly uniform heat throughout the two-story house, and I just chewed that bone until their was nothing left on it. I chased air currents, walked around with burning incense and a flashlight, pondered and theorized and finally decided that what was making this work was a multitude of factors.

I asked a lot of people a lot of questions, especially of newbies considering installing stoves. Many fled and were not heard from again. Sorry about that. I pestered people who were bragging about their BKs by asking them about prior fuel consumption vs. cords burned, and annoyed several of them as well. Over time, I developed a way of looking at wood heating as a system that worked together, and all of the parts had to be favorable, but when they were, the whole was greater than the sum of its part, so to speak, and that's when the exceptional heating performances were obtained. Obviously, the stove is a big part of it, as is the chimney. Location inside, siting outside, orientation to the sun, insolation, insulation, and so forth. Circulation of air within the house fascinated me because it was a) so clearly central, and b) so difficult to see (until one of the mods suggested walking around with the incense, and someone else chimed in w/a suggestion about burning 'erbal concoctions and the conversation generally devolved from there).

My favorite ocean current is the Great Conveyor, or Thermohaline (temp-salt) Current. It moves so slowly that it is considered to take about 400-1600 years to complete its circuit, and it travels from the Arctic Ocean through the Pacific around the Hawaiian Islands and through the Atlantic to the North Sea. It is driven by temperature differential, which is driven in part by salinity of the ocean at different temperatures and depths, which creates gradiants of density, and so weight, and so this current drops like a rock where it is heavier (saltier/colder). It brings up nutrient rich waters from depths, moderates temperatures globallly, and depends upon gradations of a few degrees to stay in motion, and life upon this planet as we know it depends utterly upon it. Like the circulation within the house, its invisible, but detectable.

 

[snowleopard]

Part two

I realized that `hot air rising' is a great oversimplification of what it taking place in our houses. Just as the Great Current has upwellings and downwellings, our houses circulate heat best when there are circles in which to circulate. The three biggest factors for keeping my house so deligxthtfully warm inside with my mid-sized stove even in extreme cold, as I have determined so far, and in no particular order are as follows:

1) upstairs, the air is free to travel in a horizontal circuit through the centrally-located bathrooms, back-to-back with doors between them, through a NE bedroom and a south-facing living room with large windows (thus warmer) and a hallway. There is a temperature gradient of a few degrees from these rooms, but what works for the Great Current works here as well--as long as we don't have energy equalized throughout a system, we have flux. Gotta love entropy, yes? The hallway is adjacent to
2) a hot-air reservoir formed in the top of the open staircase that runs along the north wall. At the bottom, it opens into the hearth room, and at the top is a landing where you can turn right and go outside, or turn left and go down the hallway I mentioned. It would be kind of a dead-air space up there, with plenty of space to collect very warm air, except that is has its own vertical circulation system going, whose engine is the cold air coming in under the door to the outside (I am also in a hillside house with doors to the outside at both levels) and dropping down the stairs. The cold air coming in is tempered by this pocket of warm air, so it feels like a mild breeze instead of a cold draft when it gets to the foot of the stairs. It also creates sufficient vortices to drive the heat into the upstairs hallway, where it becomes part of the circulation upstairs. This still didn't seem sufficient to me to quite account for the uniformity of heat distribution I enjoyed, until one day in early spring I was sitting in my bedroom idly looking at
3) the ducting vent for an HRV system that was plumbed in but never installed. This house was built back when HRV was still a theory only discussed by the frothingly passionate at whatever portion of the indifferent world it could buttonhole. The ducting would be considered laughingly inadequate beside todays mongo-chases, as it is six-inch flexible ducting that runs through the chords of the floor joists, but at its time was revolutionary. I was looking at that ducting vent and the light went on, bell dinged, and all the little cherries lined up in my mental processes. I grabbed my incense (because really, does it sound like I need 'erbals to keep myself amused? No, it decidedly does not) and lit it and went from duct outlet to outlet chuckling happily as the curls of smoke bent obligingly and briskly in the air currents and upwellings were identified in the duct that was oh-so-conveniently located in the ceiling of the hearth room, about ten feet from the stove, and downwellings were to be seen in the upstairs bedrooms in the SE and NE corners of the house, and I was ecstatic out of all proportion considering the circumstances. I *knew* there had to be something else working, and I had just found it.

So here was another dimension of the Great Current circulating in my house--a vertical/horizontal one that carried air between the floors of my house and between the cool zones and the warmer ones.

My son is awake in the night, and hungry, and even though 17 years have passed, he still thinks that if he's up and hungry in the night, I should feel obliged to do something about it. I'm going to go rustle something up, and if said knowledgeable persons have not ridden over the ridge in the meantime, I'll return and speculate about what this all might mean in your situation. If anything.

 

[snowleopard]

Son is souped and sandwiched and headed back to bed, and it's time for Part Three.

I thought about putting in-line ducting fans in place to increase the circulation, and may still do that, but I want to make sure that in so doing, I am complementing the existing circulation system rather than trying to reverse an existing air flow. I have a few gentle fans that are designed to move air between walls of rooms, and may try to adapt those to work in the ducting. I think if I get this right, it will turbocharge the existing system, but I also bear in mind the `if it ain't broke' maxim. My consistent policy with the wood heat has been to make haste slowly, to tweak something, evaluate results, and then tweak a little more. I found that this approach has served me well.

As 007 pointed out, if you try to move hot air, it cools. Naturally. But left to its own devices, and given sufficient motivation for doing so, it tends to equilize throughout a system, right? Have you thought about ways to do this that take advantage of the passive air flow you have going already, to just enhance what is already happening naturally? This involves putting in the incence time, sitting and staring at your ceiling (which can be hard to pass off as work), thinking, jumping up abruptly muttering to yourself, etc. Or that was how it worked for me.

One thing that I would try to avoid is putting much effort into warming the air space between your floors. These are going to look different for different houses, but going off mine, I have TJIs between floors. I'm guessing that they're 12", but may be 16" instead. If I tried to heat all that airspace, it would come to over 1K cf--another room! I would consider flexible ducting from downstairs vent to upstairs vent instead.

Hopefully, you are not too time-driven with this project so that you can take the time to think your way through it. It sounds like a great opportunity to get maximum results for minimum intervention if you can incorporate it into your projects.

Hope these musings are of some use to you.

 

[jimbom]

Mike.R, I am in the camp of trying the new installation with the open stairwell. Then after a season or two of experience, evaluating enhancements, and collecting data, you can make an informed decision for your house, in your climate, using your stove. I think if you have a warm basement ceiling, you will have a warm floor above.

 

[michaelreinard]

Thanks very much for your thoughtful posts snowleopard. Yes, the more i read the more I think I might be better off letting things flow naturally and not trying to force it. If anything, I want to us a large, quiet, slow moving fan rather than a little, noisy fast one, so that's why I think I am abandoning the idea of forcing cool air through skinny ducts. I was hoping to get everything done in the next month, but maybe I should hold off and experiment a little more. Sounds like the HRV system is helping you out quite a bit. Right now my only place where heat can flow is up the open stairwell so I think that I will ultimately need to put another channel somewhere else to get a convection current, but I guess I should experiment with the incense and what I have here first.

Your point is taken as well JimboM. I have only burned for one season now and still have a ways to go.

I am still curious if anyone knows whether the fire damper trumps the "return within 10ft of a stove" code issue.

Thanks,
Mike.R

 

[snowleopard]

Thanks very much for your thoughtful posts snowleopard. Yes, the more i read the more I think I might be better off letting things flow naturally and not trying to force it. If anything, I want to us a large, quiet, slow moving fan rather than a little, noisy fast one, so that's why I think I am abandoning the idea of forcing cool air through skinny ducts. I was hoping to get everything done in the next month, but maybe I should hold off and experiment a little more. Sounds like the HRV system is helping you out quite a bit. Right now my only place where heat can flow is up the open stairwell so I think that I will ultimately need to put another channel somewhere else to get a convection current, but I guess I should experiment with the incense and what I have here first.

You're welcome. I should have clarified this, and realize I did not.

While my house was ducted for an HRV system, the actual unit was never installed. I just had these ducts around the place that mystified me until I finally figured out what they were about. So there isn't any mechanical support for circulation, just a passive system that happens to work very well. Even during the extended stretch of -30F and colder we had last winter (weeks), I pretty consistently maintained a temp differential of about two degrees between upstairs and downstairs (warmer down by the stove). Enjoy the discovery process. You'll get to know your home in a whole new way with this--it's a lot of fun. And fortunately, when you do that, you'll have a place where you can talk about it and people will actually be interested. Try THAT trick somewhere else, I tell ya . . .

 

[NCredneck]

As I read through the posts, I can't help but wonder why ducting would not help. Moving hot air via the heating system fan through duct work I realize would make the air cool but I also believe the heat has to transfer from hot air moving to the cold air which in turn transfers to other parts of the house. Now if the duct is in a crawl space or attic then you would be losing some to a space that really would suck up too much to make it a viable option but if the ductwork is in a basement maybe not. I think the bigger issue is if the stove is small and keep in mind that it is really a space heater then trying to heat every room of the house is probably going to result in feeling like cold air is all you get out of the registers from hot air that is going in but its still gotta be displacing some heat into the house. The result would probably be supplementing the house heating system and not replacing it, and more than likely over firing the stove while trying to keep it warmer throughout every room. But if you have a large stove I would think that it might just replace the main system by using the system fan to move air. Just my two cents.

 

[Todd]

I've heated a few different houses from basement installs and tried everything to even out the heat. You will never get it perfect but it's possible to get some success and get about a 5-10 degree deferential which is fine for most. I'm to the point now where I finally gave in and treated a wood stove like it's designed a "space heater" and it feels really good to have a space heater on each floor.