1" air gap ventilation guestion

[Mikeyvon]

I am building my hearth pad and wall protection for my Hearthstone Phoenix in my newly constructed (owner/builder) house. I have a few questions in regards to the 1" air gap. I am planning on using durarock 1" furring strips (2x 1/2") and then 1/2" durarock and then soapstone tiles.

I have read that I need a gap for air to travel top and bottom. Is this true? How large of a gap?

I have heard/read contradicting information on leaving the sides open. Do I need to leave the sides open? How is this accomplished using furring strips (I assume the furring strips run the complete vertical lenght)?

much appreciated,

michael

 

[LLigetfa]

I would not use continous furring strips. That leaves too large a contact surface and limits air flow. Either use small squares or 1 inch long copper pipe.

You need 1 inch gaps top and bottom to allow air to enter/exit.

 

[Mikeyvon]

hey thanks for the quick answer. Is this the consensus? I have have heard so many different things.

 

[djarseneault]

one inch air space top and bottom, sides don't really matter because heated air rises. The proper way to space it of the wall is with ceramic spacers. Copper pipe conducts heat and should not be used. And no mounting screws directly behind the stove because they conduct heat too.

 

[Mikeyvon]

ok, so use copper, dont use copper. I have also heard that screws will not transfer enough heat to matter and than I hear do not use screws behind the stove. When people use metal studs, they are continuous correct? I do plan on using furring strips of durarock. How large of strips can I use?

 

[Mikeyvon]

so the durock submittal sheet shows using continuous furring strips.

(broken link removed to http://www.usg.com/USG_Marketing_Content/usg.com/web_files/Documents/Prod_Data_and_Submittal_Sheets/CB198_Durock_Cement_Bd.pdf)

so you can see how a man can be confused on the proper way to do things.

 

[fossil]

Cut the strips a couple of inches wide, double them up to make 1", run them continuously behind the Durock sheet vertically, keep the bottom of the shield 1" off the floor, the vertical sides don't matter, you can have vertical furring right at the edges of the sheet if you want. What's important is that air can freely enter all along the bottom, travel up between the shield and the wall, and exit all along the top of the shield. Rick

 

[Mikeyvon]

rick, thank you! That is what I am planning on doing. I just want to be sure I am doing it safely and there are so many varying opinions.

 

[begreen]

Rick has it right, though I'd make the strips 3-4" wide. If you make them too narrow, they will be fragile and hard to work with.

 

[LLigetfa]

A metal stud has a very thin cross-section and as such will not thermally bridge. A thick mass of cement board is much more of a thermal bridge. Metal studs wick away heat from the board and provide a large surface to transfer to the air. There is less restriction of the air passage with metal studs since they have such a thin cross-section. Also, metal studs often have cutouts allowing some cross-ventilation.

The copper pipes behave similar to metal studs, transferring heat to the surrounding air.

 

[fossil]

Lots of ways to do it that'll work. Another thought is 4" x 4" Durock squares, doubled up, and used as the standoffs...lots of ventilation in both directions. You really dont need all that many attachment points, especially if you firgure a way to support the bulk of the weight from the floor instead of simply hanging it from the wall. The only really critical characteristics are that the entire thing be non-combustible, and that a 1" air gap with free communication exist between the wall and the shield. Rick