insulating attic relative to hydronic and water lines in attic

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adiner

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Hello all of the plumbing world,

I currently live in a ranch house in SE PA, outside Philadelphia, that has hydronic lines for a Burnham boiler as well as the hot and cold water lines that run to the master bedroom, washing machine, etc. running through the attic. To make things even more fun, the air conditioner is stationed in the attic.

I have been inspecting the attic and trying to remove seriously aged insulation (torn and worn), while leaving the original, intact fiberglass batts between the joists (24" joists). Aside from replacing the damaged insulation, I was going to roll unfaced fiberglass insulation over the joists. In discovering all these constraints, I have delayed so as not to waste time and money on this method.

To complicate this situation further, this roof is prone to ice dams and, since this is a fixer-upper, there was ceiling damage when we moved in from an ice dam. A couple of years ago, I was trying to keep the attic as cold as possible to prevent an ice dam (it has gable vents, no ridge vents, and visible gaps where rafters meet the walls), not realizing that all the plumbing runs through the attic, which led to a pipe bursting. Now, I keep it at a minimum 60 degrees F in the winter, which seemed to be okay last year.

I have been trying to do as much research in the past month or so since I embarked on improving the attic insulation situation. On the one hand, I have read a bit about how a conditioned attic is ideal to prevent conditioning loss from attic positioned HVAC equipment. Air conditioning isn't my biggest concern since that is used at most 3 months out of the year, but I wasn't sure how much heat is lost through the hydronic piping in the attic, which might also affect the ice dam situation (hydronic pipes are positioned on top of flooring on top of joists). Insulating the rafters with spray foam would obviously also reduce the likelihood of burst pipes in the attic in the future, though I am sure if other residents move in, they would have a higher indoor temp which would lose heat to pipes if insulation is put on top of plumbing lines, which I have done. I am not sure how effective a conditioned attic is vs. an unconditioned attic with regard to preventing ice dams. It didn't snow the past two years and there are arguments for both on the interweb.

So, my ultimate question is, given the cost and timing of insulating with spray foam insulation, is this a worthwhile investment given my present constraints or should I continue to replace worn insulation between joists, add supplemental insulation over joists, with any exposed piping underneath if possible, and for any piping still exposed or even underneath insulation, wrap with foam insulation sleeves? I have also been using spray foam to plug up any holes from wires and piping running into attic. There are a lot of holes in a ceiling, apparently.

Any insights, information or recommendations would be greatly appreciated. Thanks for your consideration of my insulation quandary.
 
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wwhitney

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My initial thoughts:

- Air sealing is critical; poor air sealing is the number one reason for ice dams.
- Given your time horizon, insulating the roof deck is probably not worth it.
- Hydronic heating pipes won't freeze during operation, but for efficiency need significant insulation from your cold attic. 1/2" thick foam pipe insulation is inadequate.
- Domestic hot and cold water pipes should have little or no insulation between them and the conditioned space below; almost all the insulation should be on the attic side.

Cheers, Wayne
 

Fitter30

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Can't believe the water lines haven't froze or the boiler piping during a extended power outage. Should get a energy assessment+ from PECO for $99 that includes a blower door test. They offer this for electric heat if they won't come offer u the $99 they have one for $49 that doesn't include a blower door test. Insulate water pipes with 1" fiberglass pipe insulation. Heating pipes 1"
 

Jeff H Young

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I only ran 1 inch fiberglas insulation on heating hot water never less than 1 inch
 

adiner

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My initial thoughts:

- Air sealing is critical; poor air sealing is the number one reason for ice dams.
- Given your time horizon, insulating the roof deck is probably not worth it.
- Hydronic heating pipes won't freeze during operation, but for efficiency need significant insulation from your cold attic. 1/2" thick foam pipe insulation is inadequate.
- Domestic hot and cold water pipes should have little or no insulation between them and the conditioned space below; almost all the insulation should be on the attic side.

Cheers, Wayne
Thank you for the feedback. Just to clarify, do you mean sealing the holes from the ceiling due to plumbing and electrical lines or do you mean sealing where rafters and walls meet? I only ask because there are two vents at either end, so it would seem those need to be sealed too if the attic is going to be sealed
 

wwhitney

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Thank you for the feedback. Just to clarify, do you mean sealing the holes from the ceiling due to plumbing and electrical lines or do you mean sealing where rafters and walls meet? I only ask because there are two vents at either end, so it would seem those need to be sealed too if the attic is going to be sealed
By air sealing I mean creating an air barrier (air control layer) between the conditioned space and the unconditioned space. As your attic is unconditioned, this would mean the ceiling plane of the floor below (assuming a single attic covers the entire building footprint).

This is fairly hard to do in an existing house. The best practice would be to pull up all the insulation, seal all penetrations through the wall board/plaster (including encasing any electrical box in the ceiling), seal all penetrations through the exposed wall plates, and seal the wall board/plaster to exposed wall plates.

You might consider spraying 2" of closed cell spray foam in the bottom of each attic floor joist bay as an attempt to do all the above at once, but I'm not clear on whether this is considered an effective practice or not. And given your concerns about domestic water pipes freezing, you'd want the water pipes to be within the joist bays, and perhaps covered with a baffle so the spray foam is all on the attic side of the pipes.

Cheers, Wayne
 

adiner

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thank you for all the responses. I am looking into adding cellulose insulation since some of the bays between joists have no insulation, for some reason, and there's a lot of wiring. I would prefer not to use blown fiberglass only because I don't feel like stirring it up and getting itchy when transiting to access wiring and the air conditioning unit. I was also thinking of using the unfaced fiberglass rolls on top of the joists. Which method is better and would this help to reduce ice dams? does the whole attic need to be sealed, such as with closed cell foam at the gap where the roof rafters meet the joists, or just where wiring goes through ceiling drywall and joists? Thanks again
 

Fitter30

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thank you for all the responses. I am looking into adding cellulose insulation since some of the bays between joists have no insulation, for some reason, and there's a lot of wiring. I would prefer not to use blown fiberglass only because I don't feel like stirring it up and getting itchy when transiting to access wiring and the air conditioning unit. I was also thinking of using the unfaced fiberglass rolls on top of the joists. Which method is better and would this help to reduce ice dams? does the whole attic need to be sealed, such as with closed cell foam at the gap where the roof rafters meet the joists, or just where wiring goes through ceiling drywall and joists? Thanks again
Check with your electric company for a energy audit they usually have some incentives like rebate. Blower door test would be a plus.
 
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