AO Smith "new" Water Heater - what is the "R" value?
R value refers to the insulation between the tank and the outer shell. Yes, a higher R-value will mean a more expensive heater, all other things being equal since the layer of insulation is thin, like one inch, and high R-value materials (foam) for that thickness cost more.
I don't have any figures on how long it takes the tankful of water to cool down (and then require re-heating) for a given R-value.
There are usually metal fins in the central flue that capture additional heat from the exhaust gases to heat the water from inside. But when the burner shuts off, air continues to flow up the middle and cool down the water. The most modern gas water heaters also have a flue damper to stop air from rising through the middle. This is also an added cost component.
If your heater has a low R-value, you you may be able to add a blanket of insulation yourself. Some restrictions apply for non-electric heaters as the blanket must be non-combustible and not block the flow of oxygen.
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Last edited by AllanJ; 07-23-2009 at 08:52 AM.