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Discussion Starter · #1 ·
I have a hot water recirculation system that is currently insulated with regular 1/2 inch thick foam pipe insulation. Both the hot and the return lines are insulated. Altogether there is probably about 180 ft of pipe in the crawl space under the house and it is fairly accessible. I live in the foothills of California and the crawl space ranges from around 55F in the winter to 70F in the summer. I think it is a significant part of my heat loss resulting in a few hundred dollars of propane burned each year to keep it warm. Without recirculation it takes a full two minutes to get hot water in the master bathroom. I see about a 25F temperature loss through the circuit starting at 125F but have no way to measure the flow but it's quite low (gravity feed in the summer with the water heater in the basement). Every form of regular pipe insulation is pretty expensive to put over the existing insulation so I was thinking of using regular 2X4 wall fiberglass insulation with kraft paper on one side, cut into short pieces, wrapped around the pipes and secured in place with tie wraps. That appears to be very cost effective with a decent R value since a 25ft roll of insulation will do about 32ft of pipe for less than $14. Has anyone tried this?
 

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retired framer
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It is the system that is costing so much.Most people after doing everything like you are add a timer or a motion senor switch to run it only for a few minutes when needed.
 

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Being a gravity system it is at least not costing you the electricity to circulate it. BUT, if it were insulated perfectly there would be no natural circulation :(.

I will eventually go with something similar to what Neal mentioned, a circulator and motion sensor, along with the basic insulation. When someone enters it would cycle for a set time interval.

Bud
 

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Discussion Starter · #5 · (Edited)
I've played around with it quite a bit during the summer to limit the amount of water going around the recirculation loop by partially closing a ball valve where the return line comes back to the water heater. We get acceptably warm water in the master bathroom in a few seconds, the farthest point away from the heater (about 90ft), and warmer water in the kitchen in about three seconds. I think using a motion sensor to a recirculation pump would produce an unacceptable delay.

During the winter I plug in a small recirculation pump that stops when the return line reaches a certain temperature since we use an air handler for house heating and that upsets the normal gravity feed of the recirculation line. The pump is on a timer to just come on in the morning when we're getting up and at night around bedtime. That seems to work fine. We heat most of the living area with a high efficiency fireplace.

I'm guessing at how much propane the recirculation system uses but I know we burn about 1 gallon of propane per day during the summer but that includes water for the washing machine, gas range, dishwasher and the BBQ in addition to regular hot water for kitchen and bathroom use.
 

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Discussion Starter · #6 ·
Bud, if the insulation was nearly perfect I would love it. I'd just turn on the circulation pump for a minute or two every hour. I would like to get closer to that by adding more insulation if it can be done economically.
 

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The fiberglass insulation you suggested will work but the r-13 when installed into a 3.5" stud wall is based upon about r-3.7 per inch. As you wrap and tape the insulation your will compress it which doesn't kill it, just reduces the thickness. Neatness counts in terms of effectiveness of the final project.

Just thinking out loud, but Roxul is very dense and cuts and shapes easily. It is more expensive but still less than the design specific pipe insulators I've seen. One could also fit the Roxul over the pipe and wrap it with a plastic packaging material, king of like plastic wrap from the kitchen.

Bud
 
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