I would go with a 30k BTU vent less blue flame type with a thermostat and oxygen depletion sensor. Most GHs are not sealed enough to require a separate fresh air supply. If you take extra steps to seal and insulate the GH, all you need for fresh air is to leave the vent cracked a little. I would also install a carbon monoxide detector, just in case. John

11,000 BTUs of heat
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Propane Radiant Heater with Electronic Ignition 45,000 BTU's
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Coleman Propane Forced Air Heater w/Electronic Ignition (50,000-80,000 BTU)
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I have used this type heater in a GH for seceral years. It has never let me down. John

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According to the law of physics, convection type will work better than radiant type.

dcarch

rjinga, they all will probably work, although I can't imagine you'd need 45K BTU in zone 8.

All of the pics showing up in this thread look like "unvented" heaters. I would urge you to read here and here so that you are fully informed about "unvented" heaters.

SB