Fireplace popout cold air

n0c7

I have a newer home(2010) and it has a natural gas direct vent fireplace installed in a pop out/cantilever.

There has always been a cold draft coming through the bottom of the fireplace in the living space. Down in the basement there is a large cut out for the gas line that runs into the fireplace from underneath. There is a obvious cold draft pouring in this hole into the basement(and leaking into the FP) and there the temperature reading is only a few degrees above exterior temperature. If I stick my arm into this cavity I cannot feel any insulation.

Any suggestions how to approach this?

Windows on Wash

How much demo to you want to do?

The reality is that the fireplace was set before the home was insulated and there is usually no insulation and zero attention to the air barrier details in those builder's grade fireplace installs.

If you have vinyl siding on the exterior, remove it all, pull the sheathing off, insulated the cavity with Roxul, seal all the gaps, and put it back together.

That is easier than interior demo and the vinyl siding (if that is what you have) can easily be re-used.

Be sure to remove it when it is relatively warm so it will bend as compared to crack.

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joecaption

Got a picture?
That bump out was suppot to be insulated and covered with plywood on the underside.

n0c7

I'm pretty handy, I've been avoiding this since the house was still under warranty but I cannot convince the builder to do the demo. It is vinyl siding and aluminum fascia on the underside(vented style though, not sure if I should change this). I'm building my garage this summer if everything goes as planned so I'll have some spare materials incase anything breaks.

I believe my fireplace is a 0 tolerance model. Should I just insulate every gap possible with Roxul or should I try to have some warm basement air feed the cavity as well? Any vapor barrier needed?

n0c7

I can take some when I get home to show which cut out I'm talking about.

Windows on Wash

+1

Pulling that down and spray foaming it is a pretty good option but access is usually a PITB because it is so close to the ground.

If you are handy, you can do it.

I would worry about the vapor barrier if you get it zipped up tightly.

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n0c7

The builder did attempt to spray foam from the inside but that actually made things worse as now all the cold air was convecting through the bottom of the fireplace compared to some of the warm basement air countering it.

I'm assuming you mean you wouldn't vs would worry?

joecaption

Some pictures sure would help.

Windows on Wash

Correct....wouldn't.

Good catch.

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n0c7

Better than my 0 tolerance comment above when I meant 0 clearance. Craving that beer after a long day I guess.