This is certainly do-able. With a quality job, and proper pipe connections (plastic (cpvc) pipe conducts less heat then copper (cpvc insulates better)); you would not have to worry about water leaks for some time.

As far as HEAT in the attic, and having cold water available... well - the heat in the attic will help your hot water situation. You probably want to do a lot of reading up about insulation for the cold line, and perhaps take a look at this recent posting...

Here is a link that might be useful: Cold line heats up in Attic

The previous post and its link shows no understanding of plumbing as it applies to Maine.

While plumbing in an attic in Southern California needs to be concerned about excess heating, plumbing run in an attic in Maine requires attention to cold and freezing.

The original poster can do what she proposes provide that her water lines run in the attic are placed near the drywall under the insulation...and are heated with supplemental 'heat tape' as required.

manhattan42,
thank you! How would we ascertain whether we need to add the heat tape or not? We'd of course plan to drill through the joists and install the PEX as close to the drywall as possible, and insulate between each joist with foam tube insulation, as well as cover the whole thing with fiberglass batt that is normally in the attic. You don't foresee condensation being an issue in summer with this installation?

"We'd of course plan to drill through the joists and install the PEX as close to the drywall as possible ..."

Every time thet PEX passes through a joist it wil have to rise up off the ceiling.

Drilling or notching in the bottom edge of joists is not a good idea.
Try to confine your holes to the middle third (height) of solid wood joists.
Small holes for wiring and plumbing can be anywhere in the span of a solid wood joist, with manufacturer's restrictions on engineered joists (like I-joists).

Yup, in the middle third. Sorry for the confusion... I meant we'd keep the holes as low as we could within the bounds of good practice.

staceyneil-
I'm of the opinion that you do not want to put foam insulation around the pipes as this would interfere with the warming effects from the interior space. I had a run of copper pipe in my attic, and I solved my freezing pipes problem by placing the insulation blankets on top of the piping. In a couple of places, I had loose, blown-in insulation, so I just got a piece of roll insulation that I laid on top of the pipe and then piled back the loose stuff. If you do this, you just want to make sure that the pipe is as low as you can get it, and the somewhat raised insulation is arranged so that there are not any air gaps where cold attic air can get to this space where the pipes are.

"I'm of the opinion that you do not want to put foam insulation around the pipes as this would interfere with the warming effects from the interior space."

This is correct.

You want NO insulation between the pipe and the heated space below.

You need to make sure that enough heat leaks to the pipe.

Put all the insulation you want on top of the pipe.

You also need to make sure that the area with the pipes is draft free.
It does not take a very large opening to allow cold air to flow into the volume of space with the pipe and cause freezing.

I would see if you can 'box in' the area on top of the pipe with 2 inch rigid foam, with expanding foam used to seal the rigid foam tightly at the edges.

Some foil duct tape would ensure a tight enclosure.

Thanks for all your advice, folks!

Architect recommended this:
Run both PEX pipes as close to the bottom of the middle third of the joist as possible, and about 4" apart. Insulate COLD water line only with foam tubing. Top both with a 1" thick piece of rigid foam insulation about 14" wide, friction fit into each joist bay, and re-cover with fiberglass batt insulation.

He feels this will address both the winter/freezing and summer/condensation issues.

Thoughts?

Following Architect (educated) advice is probably an excellent idea and choice.

As far as my eariler post - I believe the original poster (StacyNiel) knew it got cold in Maine, and had experienced winter problems. The question they posed was about the attic, AND:
"Would the heat in summer be a problem? Are there other problems you can see with this arrangement?"

And my post, and the post link I referenced - dealt with heat in the summer. Which is what they asked. I do believe it gets hot in the summer in Maine.

Wow I just asked this question too! I didnÂt even look on the forum to see this question.If anyone has any opinions for my post, please give!
Thanks!!