Insulating (around) plumbing in cantilever & garage - in Alaska!

Users who are viewing this thread

KEBAK

New Member
Messages
2
Reaction score
0
Points
0
Location
Anchorage, AK
Hi there,

First post here - I've been perusing other threads for ideas, but would like to ask a few questions specific to our project.

Background: We're embarking on an insulation project for our heated, currently uninsulated attached garage (1969 home in Anchorage, w/ concrete block foundation/garage walls). This has opened up a new issue, with cantilever space that extends ~ 3' out from one of the garage side walls, in that there is insufficient insulation and air sealing in that cantilever space. We have hot water baseboard heat. The garage is part of the downstairs loop (also runs through living space), and the cantilever contains some piping from the upstairs living room loop (in one of the cavities between floor joists). So, we've got pipe insulation to address both in the garage -- they run along baseboard on the two side walls (one below and one above grade), and then vertically in 3 places up to the ceiling/floor space above -- and also in the cantilever. Obviously we're sensitive to freeze-ups (in Anchorage, AK), so want to find a way to insulate (and air seal, in the cantilever) in a way that won't create freeze-up problems. We have owned the home 3+ years and haven't had recurrent freezing problems (knock on wood) -- only one freeze up along the baseboard in the garage (above grade wall), but that was due to the circulator pump's failure, which of course happened during an extended below-zero cold stretch in town.

I've seen in other posts here that suggest that you want to leave the pipes exposed in the 'warm' direction, and then insulate between the pipes and the cold. In our case, I would interpret that to mean 1) in the cantilever, keeping the space above the pipes free of insulation (towards the LR floor above) and insulating below toward the bottom of the cantilever, and on the side toward the exterior wall... and 2) along the garage walls, insulating behind the pipes between them and the foundation walls and leaving them uninsulated toward the sheetrock/heated garage space.

Now, here are my questions:
- Currently the pipe in the cantilever has gray spongy foam sleeve insulation (maybe 1/2" wall) over it, at least in the stretch of it I can see through the opening of the garage ceiling sheetrock. Then, there is fiberglass insulation under the pipe (toward the cold outside), but also insulation above the pipe, at least as it nears the outside of the cantilever. There's only ~3" of space to insulate under the horizontal stretch of pipe in that cavity, between the pipe and the cantilever bottom (and about 5-6" above the pipe, before reaching the LR subfloor). Also, the cantilever bottom is not air sealed -- there's only metal soffit... I can feel the cold air coming up. There's no blocking either above the foundation/garage wall, to air seal the cantilever from the rest of that ceiling/subfloor space. So, how do I best insulate around these cantilever pipes, to try to avoid freeze-ups? I'd love to be able to not have to pull off the soffit and access that way (it's currently snowing here), but I'm thinking that's what will be needed. If I did remove the soffit, then I'd either have someone come and spray-in foam insulation (it'd be soy-based, w/ R4/in., as it's too cold to do polyurethane now), or, if that's too expensive, then I'm considering a combo of fiberglass batt above w/ rigid foam on the bottom (as a combo thermal and air shield, caulked/foamed just above the metal soffit). In either case, any suggestions on how to 'block off' the pipe there, getting the blocking as close to the pipe as possible in order to maximize space for insulation below/beside it? Would metal flashing be good? Could it be in direct contact w/ the copper pipe? If using polyiso board insulation (R-max Thermasheath), how close can it come to the hot water pipe, w/out being fire hazard? I know that it's not been recommended on these forums to use foam tube insulation in this application, but would that maybe be our only option to keep the pipe out of contact w/ the spray foam/polyiso? The problem is that we don't have a lot of room to insulate between the pipes and cold, so we have to maximize by using the highest R-value product we can that will work in this space. Suggestions? Advice? I wasn't sure how much heat would be traveling DOWN from the LR floor upstairs anyway (heat rises, no?), so wasn't sure if in this situation it would be as important to keep the tube insulation off, and/or the space above the pipe toward the heated space above or not. Feedback?

For the garage walls, which we plan to insulate w/ polyiso foam board (again, R-Max Thermasheath) and then sheetrock over for code, we were going to fit as much foam board behind the pipes as possible w/ space given, then wrap pipes w/ foam tube insulation before sheetrocking (in part to act as barrier between pipe and polyiso board) -- should we skip the tube insulation then, to expose the pipe in the direction of the sheetrock/inside heated garage space?

One more question -- is there an 'industry standard' minimum of insulation that we should have between these pipes and the exterior/cold? This will help inform our choice of products, as well as how far to move the piping out from the walls in the garage.

Sorry for the long post -- just want to describe as much as possible, in hopes it helps clarify what's going on/what we're considering as options.

Any suggestions/advice would be appreciated! Thanks in advance.
 
Last edited:

loafer

Mechanical Engineer
Messages
50
Reaction score
0
Points
6
Location
Maine
A practice that is commonly used here in Maine for camps that routinely are left with the heat off for long periods of time is to set up a closed hot water system and use 50/50 antifreeze/water mix. We used to have a camp set up like this with a forced hot water system. Up stairs in the loft we had a large expansion tank/water make-up tank that was plumbed into the boiler instead of the building water supply (for make up water). My father would top off the tank every fall and that was it. The boiler was on the first floor, so the expansion tank on second floor was the highest point in the heating system and permitted gravity filling of the entire system and for boiler make-up water.

I had the opportunity to spend a week in Anchorage and Seward a few years ago. Beautiful area you live in.
 
Last edited:

hj

Master Plumber
Messages
33,562
Reaction score
1,010
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
pipes

The only difference between insulation methods is HOW LONG it will take the pipe to freeze. Insulation does not PREVENT freezing, it just slows it down. The only way to prevent freezing is to keep the pipe above freezing temperature, either by rotating the water inside it so it remains above ambient temperature, or introducing warmth around the outside of the pipe. If the joist space where the pipes are located is blocked off from the rest of the area, either by bridging or beams, then the warm air will NOT circulate into the area of the overhand, preventing the air around the pipe from staying above freezing. AND if you do not use the faucets above the overhang often enough, the water will eventually reach ambient temperature whatever that is at the time.
 

Geniescience

Homeowner
Messages
2,137
Reaction score
4
Points
0
Location
humid summers hot, humid winters cold
... insulation... slows it down. .... if you do not use the faucets above the overhang often enough, the water will eventually ....
Ditto.

Continuous insulation, no breaks, no gaps. Think of how it feels on your skin when you have a bare patch of skin exposed, in a place that is not used to cold air. You Really Feel it. In other areas that have gotten used to the cold, you disregard it (psychologically) but the heat loss is still happening.

Your questions are not good ones. See http://en.wikipedia.org/wiki/Thermal_insulation and come back to post a gain when you understand that heat transfer happens downwards, and 2. that the one place where your continuous insulation coverage is broken is where a freeze will happen first, and 3. that radiative / radiant heat loss is a one big means of heat transfer (like the sun), and 4. that continuously-applied metal foil is a great radiant barrier, when not in contact with the pipe, so foil-faced foam is a great product (when the foil side is not the side touching the pipe).
 

hj

Master Plumber
Messages
33,562
Reaction score
1,010
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
freezing

Heat loss from a pipe is caused by radiation, and it occurs in all directions. Convection can speed up the process, IF cooler air can flow down over the pipe and absorb the heat as it passes by. But heat does no just "jump" out of the pipe in a downward direction. If anything it would be upward since warm air, and heat, rises.
 

Doherty Plumbing

Journeyman & Gas Fitter
Messages
810
Reaction score
4
Points
0
Location
Penticton, BC
Website
www.facebook.com
Your questions are not good ones. See http://en.wikipedia.org/wiki/Thermal_insulation and come back to post a gain when you understand that heat transfer happens downwards, and 2. that the one place where your continuous insulation coverage is broken is where a freeze will happen first, and 3. that radiative / radiant heat loss is a one big means of heat transfer (like the sun), and 4. that continuously-applied metal foil is a great radiant barrier, when not in contact with the pipe, so foil-faced foam is a great product (when the foil side is not the side touching the pipe).

You should come back and post when you know what you're talking about. Like HJ said heat radiates out @ 360 degrees. What in the world makes you think the heat knows which way is up and down? This post actually made me chuckle a bit.
 

Geniescience

Homeowner
Messages
2,137
Reaction score
4
Points
0
Location
humid summers hot, humid winters cold
Heat loss ... radiation ... occurs in all directions. .... heat does not ... in a downward direction.
Absolutely right. Heat moves in ALL directions, and unless there is heated air (which does move upwards), heat will be lost equally in all directions.

hj, later right after this quote you wrote,
... If anything it would be upward since warm air, and heat, rises.
The last part of this sentence is wrong. ("Heat rises") But it's OK, perhaps you wrote too fast.

-d
 

Salesdog

New Member
Messages
18
Reaction score
0
Points
1
Location
British Columbia
You seem to have the right ideas, if you are this concerned about it, why dont you also add some heat trace to the pipes. You can get the self regulating heat trace at most electrical suppliers.
 

KEBAK

New Member
Messages
2
Reaction score
0
Points
0
Location
Anchorage, AK
Hello again - OP here,

Thanks for the responses so far.

Sorry for the delayed response; I was waiting for an email-notice that there were resonses on the post, but none had come -- I hadn't realize there had been new postings until I came back to the post just now... still learning the system, I guess!

OK, so I concede that I didn't word my original post description/questions well, to show that yes, heat radiates in all directions from the pipe. Apologies. What I meant to ask/describe was how much heated AIR might be expected to be traveling down into the floor joist bays from the heated living space above the cantilever (b/c I know that hot AIR tends to rise, not drop - but I guess the better consideration is how much heat will be tranferred from the floor/space above through other means). This was asked in the context of my original idea/question, which was how to best keep the air space above the cantilever pipe free of insulation (by using blocking of some kind, to create a 'U' around the pipe?), so that it could be exposed to whatever heat/heated air would be making its way down from the floor/space above... while still insulating the space to the sides and below the pipe (cold air is below).

My leading insulation option right now (due to cost - quote on professional spray foam was pretty expensive) is to use fiberglass batt in the upper portion of the floor joist bays, with R-Max Thermasheath (foil-faced polyiso board) to air-seal at the bottom of each bay. Therefore, I'll be dealing with fiberglass around that pipe in the cantilever. My remaining questions along these lines are:
- Is there agreement that it is a good idea to leave that cantilever pipe w/out tube pipe insulation, so that the pipe gets full exposure to any warmth that will reach it from above?
- Can fiberglass come in direct contact with hot water pipes, without concern, or should I put a barrier/block between the pipe and the fiberglass? (Copper pipe, part of upstairs loop in boiler system, set at about 120F right now, I believe.)
- Any suggestions on how to 'block' around the pipe in a 'U' shape fashion so that I can fully insulate below and around the sides of the pipe, and leave the space above it (towards the warmth) open? I had thought of metal flashing, but that was just a first thought (I've never worked w/ flashing) -- is there something better to consider...? Or, seeing that I've been told that those pipes don't get over ~180F, do I need even need to leave a barrier between the pipe and the fiberglass and/or polyiso board?

Also, to follow up on HJ's first post:
The only difference between insulation methods is HOW LONG it will take the pipe to freeze. Insulation does not PREVENT freezing, it just slows it down. The only way to prevent freezing is to keep the pipe above freezing temperature, either by rotating the water inside it so it remains above ambient temperature, or introducing warmth around the outside of the pipe. If the joist space where the pipes are located is blocked off from the rest of the area, either by bridging or beams, then the warm air will NOT circulate into the area of the overhand, preventing the air around the pipe from staying above freezing. AND if you do not use the faucets above the overhang often enough, the water will eventually reach ambient temperature whatever that is at the time.
- Are you suggesting that adding vertical air-seal blocking at the foundation wall to separate the cantilever joist space from the rest of the home's is a bad idea? I'm for sure going to add blocking in the other bays, but I was thinking along your lines for the one bay with the pipe running through it. If I get a 'professional opinion' to support leaving the vertical blocking off in that one bay with pipe, then I'll for sure do so -- let me know if that's what you meant.

I'm a newbie with this stuff -- any suggestions/tips would be appreciated.

Again, thanks much for taking the time to weigh in/explain,
Katie
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks