What material can I have behind a vented Heat Shield in an alcove?

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

plieberg

New Member
Sep 21, 2022
4
Minnesota
I have an older (1990s) Patriot stove. The previous owners of the cabin moved it so they could put a stairway where it used to be. They slid it into this alcove and left it. I am looking to reconnect it and use it in the alcove. Looking at the clearance requirements, I should be ok using a vented heat shield on all sides. My question is, would I need to remove the wood tongue and groove and install something more fireproof (i.e. cement board) behind the heat shield? Or, is the existence of the heat-shield enough?

Thanks

PS - I did search the forums for this question and couldn't find anything that answered this question close enough that I felt ok moving forward. :)

Stove-Alcove.png Stove-Back.png
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,492
South Puget Sound, WA
The Patriot has fairly conservative and stiff alcove requirements. It doesn't look like there is enough room to satisfy them in this space. How wide is it?

Screen Shot 2022-09-21 at 8.40.08 PM.png
 

plieberg

New Member
Sep 21, 2022
4
Minnesota
The Patriot has fairly conservative and stiff alcove requirements. It doesn't look like there is enough room to satisfy them in this space. How wide is it?

View attachment 299253
I assume those minimum clearances are without a vented heat shield. My research indicates that a vented heat shield should reduce clearance requirements by 2/3. Am I incorrect in that assumption? If that works, there is enough room for it with the vented heat shield (18" reduced to 6").
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,492
South Puget Sound, WA
The 2/3ds case is for an unlisted stove. That reduces 36" unshielded to 12". However, in this case, Lopi has defined what they require for reduced alcove clearances based on their testing. It is less than 2/3ds. This requires a ventilated brick wall on each side and back. If a brick is 3.5" across, that together with the airspace on each side = at least 9" from the width of the alcove space to make what Lopi calls a non-combustible alcove. The Patriot is 23 5/8" wide, add 16" clearance + 9" = about a 49" wide alcove. Is the space that wide?
 

plieberg

New Member
Sep 21, 2022
4
Minnesota
The 2/3ds case is for an unlisted stove. That reduces 36" unshielded to 12". However, in this case, Lopi has defined what they require for reduced alcove clearances based on their testing. It is less than 2/3ds. This requires a ventilated brick wall on each side and back. If a brick is 3.5" across, that together with the airspace on each side = at least 9" from the width of the alcove space to make what Lopi calls a non-combustible alcove. The Patriot is 23 5/8" wide, add 16" clearance + 9" = about a 49" wide alcove. Is the space that wide?
Not 49” wide. More like 44 without the tongue and groove.

If only they’d installed the stairs 6” to the north. lol

Looks like I need a different stove or move the stove somewhere else. Was hoping to use the existing chimney, which is problematic if the stove is anywhere else.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,492
South Puget Sound, WA
In one sense, Lopi deserves credit for clearly documenting an alcove build, but unfortunately, they don't publish other NFPA 211 options that can be effective heat shielding for achieving the 2/3ds reduction. They only site the brick option.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,524
NE Ohio
Not 49” wide. More like 44 without the tongue and groove.

If only they’d installed the stairs 6” to the north. lol

Looks like I need a different stove or move the stove somewhere else. Was hoping to use the existing chimney, which is problematic if the stove is anywhere else.
That wall is pretty thick...can you take it out around the stairs there? Maybe put in a metal railing? That would gain you the extra 5-6" you need...
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,492
South Puget Sound, WA
That wall is pretty thick...can you take it out around the stairs there? Maybe put in a metal railing? That would gain you the extra 5-6" you need...
Might get it close, but what supports the single brick wall?

Will this installation be inspected? If yes, it might be worth asking the inspecting authority if substituting an NFPA wall shield made of metal, or cement board with tile (and the 1" air gap behind) would be ok. Maybe a metal wall could be designed so that it became the stairwell guard?
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,524
NE Ohio
but what supports the single brick wall?
Mortar and rebar? ::-)
If you put a metal railing there the need for a brick wall on that side goes away, no?