# Is a wood stove much less effecient installed in an alcove?



## johnstra (Nov 21, 2010)

I did some searches, but couldn't find anything that addresses this.  If a radiant stove is installed into an alcove, how much less effective is it than if installe in a central area where it can radiate in all directions?  I know each application will be different, depending on how well the alcove is insulated, how big the space being heated is, etc.  I'm asking in general, does an alcove installation hamstring a free standing stove.


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## Dune (Nov 21, 2010)

Yes, though it could still be effective.


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## Renovation (Nov 21, 2010)

Hi Johnstra,

Uh oh, now you've asked for it, literally! 

I'm actually designing an alcove for my future stove, and have some tweaky, geeky thoughts, for others to sanity check for me.

My quick answer is I think an alcove need not be a problem and, if it is designed well can actually offer some advantages.

"Absurd!" you say?  Let me explain.

As I see it, as long as one maintains minimum clearances, etc, there are two main issues, and an option:

*1.  Not losing heat in the alcove.*
*
2.   Getting heat out of the alcove.*

*3.  Optionally, smoothing temperature swings.*

*1.  Not losing the heat:*   A radiant stove in particular, will heat up the alcove itself, so it seems important that the alcove be well-insulated if it is on an outside wall.  Temperature loss through a barrier is directly proportional to the temperature *difference* across that barrier, so a hot wall/alcove of a given R-value will lose a lot more heat to the outside than cooler walls around it with the same R-value.  

In particular, backing a stove or insert into an uninsulated masonry fireplace on an external wall will lose more heat to the outside than the same fireplace moved out into the room.  So the upshot is, if the alcove is on an outside wall, it should be well-insulated--better than the surrounding walls if their insulation is only fair.

*2.  Getting the heat out.*  It seems to me that the trick is simply moving air over the hot surfaces of the alcove to heat the air and get the heat out. This seems fairly simple, and could be a ceiling fan that moves air through the alcove, or a box fan blowing cool air towards the alcove, or a fan behind the stove.

Geometry helps too--an alcove with an angled ceiling would tend to pour air out into the room through natural convection, with less trapped than under a flat ceiling.

Of course convection stoves lessen both of these problems, by heating the air more and the surrounding surfaces less--but usually, if using a blower, at the expense of some noise from the relatively small fans in the blowers.  In general, the smaller a fan, the more noise it makes to move a given amount of air.
*
3. Do you want to smooth out temperature swings? * Soapstone, cast iron, and thermostats smooth these swings, but if you have a manual steel stove, you might want thermal mass to suck up bursts of heat, and re-radiate them gradually.  An alcove with thick stone walls could do that, though, from #1, outside walls should be well insulated.

In my case, I'm planning on a stove with fairly constant heat, so I'm not concerned about smoothing out temperatures, but just moving heat out into the room.  So I'm planning on a well-insulated alcove, with side walls angled to reflect heat out into the rooms, with a 1" airspace under a covering of corrugated sheet metal (on ceramic spacers).  Such a covering of spaced sheet metal is usually used as a heat shield to keep the walls from burning, but I'm planning to use the covering mainly to *intercept* the heat, reflecting it out into the room and changing radiant into convection heating by heating the air flowing over it.  That air flow will come from natural convection, and will be augmented with a ceiling fan, which will be quieter than most stove blowers.  

This setup would have the added advantage of working well in power outages.  The reflectivity of the sheet metal, and natural convection over it should transport heat out into the room even without a fan.

That's my plan anyway.

Of course a radiant stove placed centrally in a room avoids all these issues, but that would be too easy.  (And in my case, I want the extra space.)

There are my thoughts--I hope they are useful, and that other folks check my reasoning.  Happy heating!


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## SolarAndWood (Nov 21, 2010)

RenovationGeorge said:
			
		

> There are my thoughts--I hope they are useful, and that other folks check my reasoning.



Sounds right to me George.  The stove at our family's camp is in a alcove, the old exterior wall brick fireplace.  It is a good thing there is a lot of firewood available there.  Some day I will tear the brick down and build an alcove like you describe complete with an exterior door to pass wood through.


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## begreen (Nov 21, 2010)

Most of these issues are mitigated with a more convective stove. In the least put a rear heatshield on the radiant stove. Also, the ceiling of the alcove doesn't need to be flat. Consider angling the ceiling upward, into the room so that it doesn't trap heat.


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## soupy1957 (Nov 21, 2010)

I just got done reading THIS other Thread start, and think it to be an example of what "I" WOULDN'T do, for the very reason you raise the question:

https://www.hearth.com/econtent/index.php/forums/viewthread/63564/

As is typical in any Forum on any subject, I'm sure there will be as many who will say "it's fine" as there are those who will say they DON'T think it to be practical or wise.

I, (admittedly) fall under the category of those who DON'T support that type of installation.

-Soupy1957


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## begreen (Nov 21, 2010)

That's a pellet stove and not really relevant. It's a totally different animal with very different clearance requirements and totally convective heating.


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## soupy1957 (Nov 21, 2010)

BeGreen, if you read my response in that Thread that I linked, you'd see that I agree that BECAUSE it's a Pellet Stove, I can't speak to the issues related to its location.

Your point is well taken.

-Soupy1957


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## begreen (Nov 21, 2010)

I agree with the concern there and don't condone that installation either. Cutting clearances is definitely not cool. Normally wood stove alcove clearances are much more generous, especially for the ceiling.


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## Renovation (Nov 21, 2010)

BeGreen said:
			
		

> Cutting clearances is definitely not cool.



Har!  I think you might have a safety slogan there!  

I must say, that tight pellet stove install got a gasp out of me.  Put a wood stove in there, and you wouldn't have to load it more than once.

Thanks for your comments, Solar, Soupy, and BG.  Even a politely dissenting response is better than none.

As I see it, the only significant advantages of an alcove installation are space, traffic flow, and personal aesthetic preference.  I think most would agree that otherwise, putting a stove in the center of a room would usually be the most efficient.

Of course life is about making our personal best out of the constraints we face, and my goal here is making the most of an alcove installation.   I suppose there will always be some heat loss from the wall, and less natural circulation and direct radiant heating of the room.   But I'm thinking that if one provides adequate clearance, insulation and airflow, it's as safe as an open installation, comfortable, and nearly as efficient.

And the alcove's partial conversion of radiant heat into convection (hot air) can be a benefit.  As an example of leveraging another constraint, my design requires a laminate support beam across the top-front of my alcove to keep the house from falling down.  Now, unless I lower the alcove ceiling (angled, as BG suggests) so its front edge is level with the bottom of the beam, the beam will inhibit airflow and trap air.  My design leaves the alcove ceiling a little higher than the front edge of the beam, creating a small plenum that would trap some hot air.  I'm planning an independent intake (separate from my furnace) at the top of this plenum, with a powered duct run into my bedroom.  Then at night I can turn down the stove, turn off the ceiling fan, and turn on the duct to pump heat into my bedroom. 

Anyone see any safety issues with that?  I'm planning on exceeding minimum clearances *and* having all the surfaces of the alcove shielded, ceiling included.  The duct will be long and horizontal enough to not be a fire path, with its intake behind the sheet metal ceiling shield.  I haven't researched any threads into carbon monoxide detectors, but is it a good idea to put one in the bedroom for safety, regardless of ducting? (I'll look--it's probably been discussed already.)

Thanks again, and have a great one!


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## johnstra (Nov 22, 2010)

I think I have my answer as to the issues associated with an alcove install.  Loss of heat and airflow are the big ones, which is what I thought.

George - Cool plan!  I'm anxious to see how it turns out.  I do think you need to research CO and ducting from over the stove.  I did see cautions against that somewhere - don't recall where.  I wouldn't do it and if you do, you absolutely better get a reliable CO detector.


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## LLigetfa (Nov 22, 2010)

In the old days with the radiant heat of fireplaces, wing chairs were all the rage as they trapped some of that radiant heat so that the back of your ears wouldn't get cold.  Converting radiant heat into convection heat is a good thing and as long as the alcove promotes convection currents, there would be no real loss.


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## begreen (Nov 22, 2010)

I'm a little leary of the plan, probably because I am kind of a KISS guy. My preference is to work with nature as much as possible to assist natural air convection.


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