PEX in an attic with a skylight

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Houston70sRanch

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Hi Kind and Knowledgeable Folks,

We are in the process of getting bids on a whole house re-pipe with PEX. We have 40 year old galvinized pipe in 2 bathrooms and 20 year old copper in another. We are keeping the copper pipes.

Prior to our purchase, our house was raided by the FBI/DEA for being a marijuana grow house. The only thing they left behind is a great skylight in the perfect place to catch a lot of sun that goes into the attic. We think this is where they started their plants.

PEX will be run directly beneath it. In all 3 quotes we received, no one mentioned the skylight and potential UV problems with PEX until we brought it up. 2 people said "The PEX is insulated so it won't be a problem." One said, "Yeah, you'll probably need to cover the skylight."

I'm wanting to know what you guys think.
 

CountryBumkin

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When I ran PEX through the attic, the PEX supplier said one should always run "insulated" PEX in the attic (even though my attic doesn't freeze). It only costs a little more than regular PEX. http://www.supplyhouse.com/Pre-Insulated-AquaPEX-Tubing-11448000

If I understand your situation, there is a skylight in the attic (that former owners installed just for their plants) which is bring in sunlight and heat to the attic space. I assume this is unfinished attic space. Does it have fiberglass or blown-in insulation? In your case I would be more concerned about the skylight adding all that additional heat load to the attic. If you can't remove the skylight, perhaps you can install a sheet of rigid foam board across the opening.
 

Zl700

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Cover the PEX
Quality 6' closed cell foam insulation for 3/4" pipe is about $7 each at Home Depot
 

Jadnashua

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Is the location of the skylight such that you might make a light tunnel into actual living space? If so, you could then wall it off. I put a skylight at the top of my stairwell, and built a light tunnel from the roof to channel that light where it was needed. The PEX MUST be protected from the UV that will come in through the skylight. Glass does stop some of it, but over time, it WILL degrade the PEX.
 

Houston70sRanch

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Thank you for the responses I've gotten so far. The skylight could be tunneled into a bedroom, but I don't want a skylight in the bedroom. The problem may be becoming moot as we've decided to go ahead and get a new roof since we are about to update the plumbing and bathrooms. I am still curious about whether regular foam insulation would protect the PEX or not. Currently we have regular pink insulation. If we get a new roof, we'll probably go with the other stuff.

Also, I did not know that PEX suffered from being in a hot attic.

Thank you again, everyone.
 

CountryBumkin

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PEX won't suffer from a hot attic. It's just the water in the PEX will get hot from sitting in the pipe in the attic, so when you go to use the sink or shower the water won't be cool/cold. If you live a cold climate, the hot water will get cooler in the pipe without insulation. However, you could cover the PEX with the fiberglass insulation to protect it. And Terry said in another post that the insulted PEX piping doesn't do as good a job as just getting the PEX under the attic insulation. I would do both.
 
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