two-way water recirculating system & Pipe insulation in attic

[Whirler]

Hello I have a question about hot water circulation systems.

We recently had to re-pipe our 15-year-old house due to leaky fittings. The new pipes are pex through the attic.

As is common, our master bath is in the opposite end of the house form the water heater, so we’ve always had to wait for the hot water in the bathroom.

We have gotten used to this, but with the pipes in the unheated attic things have gotten worse – in the winter the cold water that initially comes from the hotwater is *really* cold.
So that’s why I was planning on installing a hot water recirculating system.

But then I started thinking… in the summer, the water in both the hot and cold pipes will get very hot! So I was wondering if there is a way to recirculate both the hot and cold water? Now, I understand that it is obviously not possible to circulate both ways at the same time without having to install extra pipes ( was planning on just using the existing piping). But is there any system that would allow me to operate the system in different directions depending on the season? Or could I easily make some custom setup for this?

Or would I be better of installing a dedicated return pipe (or two?) If so, perhaps the valve could go in the attic just above the bathroom? That would still leave a few seconds of cold water in the last bit of pipe, but it would avoid having to run an extra pipe down the wall on that end of the system.

As I side note, when we started using the new pipes in the summer, the water was scalding hot! I added some foam insulation (R4) and that made it just very hot. Still, it is too warm for showering or washing hands. What would be the recommended way to insulate the pipes in the attic even further? The pipes are mounted above the ceiling insulation. I was thinking of just wrapping wads of regular fiberglass insulation around them, but I wasn’t sure how much difference that would make, and also wanted to make sure I don’t get problems with condensation etc.

Thank you!
Donald

 

[frodo]

insulate with rubatex

then. cover it with the fiberglass insulation in your attic

after you do this, then readress the circ line

 

[Whirler]

Thank you for the reply!

I have put the foam insulation around the pipes already, and as I mentioned it had at least some effect.

I think I have another problem though -- when the plumber installed the pipes, he didn't lay them directly on top of the joist as in your illustration, but he actually attached them to the braces that goes to the rafters a couple of feet above the joists.

Now that I am thinking about it, it does seem odd, as the pipes will be more exposed that way. And it wasn't like he was cutting corners, but actually made more work for himself.

Do you think wrapping the fiberglass around the pipes where they are would work? I guess making strips of insulation and tying them on there could work. Or would it be better to detach the pipes from the braces? (I have a feeling that even if I do that, they will still not be laying flat on the joists as they are pulled in between various braces)

Thank you!

 

[KULTULZ]

As I side note, when we started using the new pipes in the summer, the water was scalding hot! I added some foam insulation (R4) and that made it just very hot. Still, it is too warm for showering or washing hands. What would be the recommended way to insulate the pipes in the attic even further? The pipes are mounted above the ceiling insulation. I was thinking of just wrapping wads of regular fiberglass insulation around them, but I wasn’t sure how much difference that would make, and also wanted to make sure I don’t get problems with condensation etc.

...whew...

Is it possible to post photo(s) of the installation? How hot does the attic actually get (thermometer reading)? Is the pipe install directly under a sun heated portion of the roof, i.e. constant southern exposure?

With proper attic ventilation you could bring down the air temp considerably. Also there is thermal insulation available to partially block the radiant heat from entering the attic ($$$)

My concern is the actual temp of the hot water on a hot day. You may have to install a tempering valves(s) to insure no scalding or thermal shock.

Why was the piping run in the attic?

 

[frodo]

Thank you for the reply!

I have put the foam insulation around the pipes already, and as I mentioned it had at least some effect.

I think I have another problem though -- when the plumber installed the pipes, he didn't lay them directly on top of the joist as in your illustration, but he actually attached them to the braces that goes to the rafters a couple of feet above the joists.

Now that I am thinking about it, it does seem odd, as the pipes will be more exposed that way. And it wasn't like he was cutting corners, but actually made more work for himself.

Do you think wrapping the fiberglass around the pipes where they are would work? I guess making strips of insulation and tying them on there could work. Or would it be better to detach the pipes from the braces? (I have a feeling that even if I do that, they will still not be laying flat on the joists as they are pulled in between various braces)

Thank you!

the trick with insulation is no air,,the insulation needs to be installed so that the it is completly covering the pipe.
when you insulate a pipe but not seal or install insulation on the 90 or tee
you are defeating the purpose.

to answer your question. sure, buy a 20 dollar bag of batt insulation and cover up everything.

my attic is 24'' deep with blown in..i covered duct work, everything
built a plywood dam at the stairs

 

[KULTULZ]

the trick with insulation is no air,,the insulation needs to be installed so that the it is completly covering the pipe.
when you insulate a pipe but not seal or install insulation on the 90 or tee
you are defeating the purpose.

to answer your question. sure, buy a 20 dollar bag of batt insulation and cover up everything.

my attic is 24'' deep with blown in..i covered duct work, everything
built a plywood dam at the stairs

The problem (IMO) is that thee install was two feet above the joists (no - do not disturb the original install). To cover the lines he would have to blow in more that 24" of insulation.

He would have to install insulation board(s) on either side of the attic to retain the blow in and not cover the soffit intakes (if so equipped).

 

[Whirler]

Thank you for your suggestions!

I finally got chance to get up in the attic and take some pictures.

Turns out I remembered a few things wrong – the pipes are actually quite a bit higher up than I thought. They are a good three feet above the joists, so covering them with blown in insulation is out of the question. I also noticed that I only put the foam insulation on the cold water pipes. That was in the middle of the summer, so it was very hot up there, so I spent as little time up there as possible. I didn’t mention before but I am in the deep south, and it gets very hot and humid here. I think my attic is properly vented, with unblocked soffit, gable and ridge vents, it’s just the weather is very hot.


So, my plan is to put foam insulation on the hot water pipes as well. The foam I used for the cold water is supposed to have an R value of about 4, and I was planning on using the same on the hot water pipes. Are there any other type of foam that would be a lot better? I have not found the rubatex brand, but I did see something called ‘k-flex’ with R7. It’s way more expensive though, and I am not sure if it worth the price. Then I was planning on getting batts of r19 fiberglass insulation and wrap around the foam-covered pipes. I have a question about that – will it be ok to just let the pipes support the weight of the insulation, or would it be safer to install some sort of support that the fiberglass the rest on? For the bit of pipes that is on the joist I will just cover with fiberglass.

Thanks again!

 

[KULTULZ]

Just wondering...

1) Did you ever take a air temp reading in the attic during summer/winter?

2) Why did he run the lines in the attic (and not under floor joists)?

3) How far south are you?

Read -Study This Website - CLICK HERE-

 

[Whirler]

Just wondering...

1) Did you ever take a air temp reading in the attic during summer/winter?

2) Why did he run the lines in the attic (and not under floor joists)?

3) How far south are you?

Read -Study This Website - CLICK HERE-

1. I have not. I might try that this summer. Our A/C bill is pretty low, so at least it seems pretty well insulated down to the living area. Our roof is dark shingles, so that might contribute to a hotter attic in the summer.

2. Our house is on a concrete slab. The house had to be re-piped because the brass fittings were faulty and corroded.

3. I am on the Alabama Gulf Coast.

 

[KULTULZ]

1. I have not. I might try that this summer. Our A/C bill is pretty low, so at least it seems pretty well insulated down to the living area. Our roof is dark shingles, so that might contribute to a hotter attic in the summer.

2. Our house is on a concrete slab. The house had to be re-piped because the brass fittings were faulty and corroded.

3. I am on the Alabama Gulf Coast.

OK...Got It.

Were you able to peruse the referring URL I offered?

 

[phishfood]

When I repipe a house, I lay the piping down on the bottom cord of the roof trusses. Insulate with 1/2" wall closed cell insulation (which you have already done), and then lay R13 batt on top of that.
I don't guarantee that there will not be some temperature variations, but it will be very minor.

Lower the piping as much as possible, and insulate as you have mentioned. If you can't get the piping down onto to "floor" of the attic, then use batt on both sides of the pipe. Try not to compress the insulation, as that reduces the effectiveness of the insulation.

 

[Whirler]

OK...Got It.
Were you able to peruse the referring URL I offered?

I missed the link before. Thank you! I must admit I was not aware of radiant barriers. I looked into it some more, and that definitely sound like something that would help lower the overall temperature in my attic. So that in combination with the pipe insulation will hopefully make a bigger difference. It also sounds like an investment that would pay off in the long run with slightly lowered power bills. Unfortunately, my house has a hipped roof with valleys and angles and the truss construction in the attic is like a maze. And on top of that there is a cathedral ceiling in our main room, so that make it even harder to get around in the attic. But I am sure it's possible to get the barrier put up with some time and effort.

When I repipe a house, I lay the piping down on the bottom cord of the roof trusses. Insulate with 1/2" wall closed cell insulation (which you have already done), and then lay R13 batt on top of that.
I don't guarantee that there will not be some temperature variations, but it will be very minor.

Lower the piping as much as possible, and insulate as you have mentioned. If you can't get the piping down onto to "floor" of the attic, then use batt on both sides of the pipe. Try not to compress the insulation, as that reduces the effectiveness of the insulation.

Thank you for your suggestions. I hadn't thought of sandwiching the pipes between two batts - that does make sense though! I will see how feasible it is to lower the pipes, hopefully it won't be too hard. That would make the installation easier. How flexible/sturdy are usually the pex pipes? If I lower them it will make them a little longer, so I might need to do some additional curving at the end.

Thanks!

 

[KULTULZ]

I wonder if the plumber ran the lines so high as working space within those trusses gave little working room? Lowering the lines would make them much easier to insulate but just wrapping them with batts sounds logical also (cheaper alternative).

Gulf Coast... I envy you...