I noticed in HP152 there is possibly some misinformation. On page 74, there is an image of a gas-fired water heater being wrapped with a fiberglass blanket. This is generally considered unsafe, and I don’t see the safety issue being clarified in the hot water efficiency article. I usually recommend any combustion appliance be 3 feet from any combustible materials.
The problem with the blanket is that they often slide down and sometimes reduce the combustion air. The real danger is if the home’s performance is compromised—for example, in an airtight home with poor chimney draft and a couple running exhaust fans, such as a dryer and oven vent fan. While the situation is unlikely, getting flame rollback onto the fiberglass blanket wouldn’t be desired. This is not to say they shouldn’t be installed on gas water heaters, but caution should always be advised.
Also along the same lines is fitting pipe insulation to pipes in close proximity to the water heater flue. I often see heat-damaged foam pipe insulation there as well. Perhaps some caution is warranted with showing the image on page 73 as well. The article had plenty of useful information, but for someone who has no previous knowledge about these systems, it could be a potential hazard to apply the information as presented. It might be good to further graphically show what a heat trap or loop is also.
James Meehan • via emai