# Choice of insulation behind electric fireplace



## misuszatek (Aug 22, 2018)

I'm about to finish framing for electric fireplace bump out. 
It is OptiMyst 1000 fireplace with heat vent at the front. It works by illumination myst that forms fake "flame"
The plan is to insulate the wall behind it with Rockwool bats and cover with vapour barrier. Is this correct course or should I do it differently?


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## Nealtw (Jun 22, 2017)

That looks to be another cantilever that should be blocked between joists.
The outside wall is treated like the rest with insulation, VB and drywall and then the ceiling in the box should have drywall as a fire stop.
That is code here.

Did that fireplace come with some sheet metal parts sticking up on top?


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## misuszatek (Aug 22, 2018)

Nealtw said:


> That looks to be another cantilever that should be blocked between joists.
> The outside wall is treated like the rest with insulation, VB and drywall and then the ceiling in the box should have drywall as a fire stop.
> That is code here.


Yes it is blocked but doesnt sticks out that much as this is side of the house.










So pretty much I should close the wall behind it like any other wall?
The fireplace itself will be covered with HardieBacker and maybe some wall panelling (I need to check if 5000 BTU heater will not damage paneling first)




Nealtw said:


> Did that fireplace come with some sheet metal parts sticking up on top?


No sticking our parts. It is 2 piece setup:
1. metal box
2. insert with myst/led machine, water container etc etc


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## Nealtw (Jun 22, 2017)

Yes treat it like any wall
Even a 6" cantilever is blocked
A regular gas fireplaces have a distance above to any wood, is why I asked.


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## misuszatek (Aug 22, 2018)

Nealtw said:


> That looks to be another cantilever that should be blocked between joists.


So should I add block between joists right over double top plate?
Or just insulate?



Nealtw said:


> A regular gas fireplaces have a distance above to any wood, is why I asked.


Oh ok.. there is a vent/exhaust for 5000 BTU heater at the top of the front opening that might be optionally turned on, but I doubt it will generate any significant amonunt of heat to worry in comparison to gas fireplaces that generate 40,000-50,000 BTU. To be completely safe I will double check the exhaust temp once fireplace is connected.


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## Nealtw (Jun 22, 2017)

misuszatek said:


> So should I add block between joists right over double top plate?
> Or just insulate?


Yes the solid blocking is code to stop the floor joist from falling over on their side when they are overloaded.
For a short unit like a 6 ft window or something, I doubt it is all that important but sometimes it is the whole front or back of the house it is important and I would want at least some of them blocked.
When we block them the people insulating caulk them on both sides in and out. They don't want any air exchange from the warm floor system to that area out there where it can cause mold.
So if you are not blocking them I would insulate and then block it over the wall with foam board and caulk it so it doesn't leak air.


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## misuszatek (Aug 22, 2018)

Ok I will insulate and block between each joist. 
Thank you, you help me a lot


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