wow, glad to hear.
Thank you !
I enjoy your thoughts on the state of current insulating practices, Molo. The world is better off now than we were 30 or 40 years ago, in terms of insulating buildings, but we have not yet got it right, in my opinion, which seems to concur with yours too.
Today I don't have time to spell out much about the pipe "heat containment system" that I think will work well.
Here's an overview.
First, about the cold water going in.
1.) It is going to be heated.
Second, about the hot water coming out.
2.) It is very hot, and moving fast to its destination.
Here is how I might insulate all four pipes together:
x x
x x
1. All four pipes crammed together. No loss since the cold is going to get heated anyway, and the hot water is not going to lose much heat on its way to the tap. Besides, it is plenty hot when it is fresh out of the tank.
2. put only 1/8th inch insulation between the two pairs of hot/cold, just to help identify which pairs belong together in the same tank.
3. include the corresponding electrical wires in each separate cluster, with minimal insulation again.
4. put 1/2 to 1 inch of insulation around the entire bunch. If foam from a can, there are no air spaces left. If any other system, some air spaces left over, good to fill in with foam too.
5. This oval-shaped riser is now about 3 to 4 inches in diameter. It then gets "glued" to the outside wall bricks with more airtight foam (3 more inches), and a radiant barriar (e.g. foil faced bubble wrap, or just a house wrap with radiant barrier in it) goes on top, on the three exposed sides but not underneath where the bricks are, but it does follow the pipes right up and over into the attic and until the pipes penetrate the building envelope. You need just as much insulation and care in execution in the attic as ouside ni the shed. See
http://en.wikipedia.org/wiki/Building_envelope
Since pipe cost is low, I would use a large diameter pipe (3/4" or more), so that when the power goes out and the temperature goes down, you have more thermal mass working with you in the pipes; it takes more energy loss to freeze it at any one weak spot.
The first pipe to freeze is the cold water pipe. What is the coldest temperature water you get in winter? Is it Lake Ontario water or ground water? Do you pay for water consumption? When power goes out, does water still run?
If power is out for many days, the residual heat energy stored in the tanks will be lost and the tanks' water will get so cold you will wonder if (or when) it will freeze. But did you know that moving water doesn't freeze as "easily"? And did you know that your water source temperature is many degrees above 32 Fahrenheit? Of course! You can pull water through the tanks and keep the pipes flowing and keep the temperature of the entire system well above 32 degrees Fahrenheit! Pipes and tanks. The flow could be much less than full throttle. When to start running water? When you are really really sure that the residual heat coming through the building is not enough to keep the pipes' temperature above freezing. By this time the minimal heat left in the tanks will have long since disappeared.
If you want to wrap something with a heat tape, I think I would recommend you wrap only the cold water line, in which case it needs a little more insulation all by itself just to isolate it from the electrical wire. If power comes on for an hour or two from time to time during a month-long power outage, you will have warmed up the pipe most vulnerable to freezing.
If you don't pay for water consumption, consider using only one cold water supply pipe, extra big.
Quiz Q answer: radiant barriers are most necessary when the temperature difference you want to maintain is highest. And your case is a big one. Since the outside temperature will penetrate into your shed, the (tank and pipe) insulation will have to reduce heat loss
across a higher gradient than is ever seen indoors. So you need a radiant barrier more than anyone else.
Second answer: when every last degree counts, you need a radiant barrier too. And that is the situation when you want to ensure the pipes don't freeze.
David