Hot Water Tank in Uninsulated Shed?

[Geniescience]

good ideas

....warnings ... Sick House Syndrome ....

Since it's only a shed, not to worry. It won't get sick because there are no people breathing in it.

Houses and barns have this in common: they are occupied, the occupants breathe, and the exhalations are humid air. In air tight houses, heat exchangers are used to exchange air and transfer heat. For a simple residential building you can get one of these for less than a thousand including installation kit. In some places it is now law that all highrise condos must have one. See http://en.wikipedia.org/wiki/Heat_recovery_ventilation

Energy Recovery Ventilators (ERV) handle humidity as well; they are not yet available in the residential market at anywhere near that price range.

.... a radiant barrier on the floor as well?
.... Is it bad to double up on the foam insulation board?
.... connecting the interior corners of this box?

Yes, I did mention a "floor sandwich" with a radiant barrier in it, a couple posts back.

Doubling foam is good. Stagger the seams.

Seal corners inside with the same tape or foam glue as the seams

David

 

[Molo]

Hello David

Only one radiant barrier, as thick as possible, but not two barriers separated by any space, and a fair distance from the heat source, not just a quarter inch away. Only one vapor barrier, wherever you choose to build it, but not two in any exterior walls, separated by any space (moisture would get stuck in between and start an uncontrolled rot in any material). If you do seal the shed also with a vapor barrier, it is not serious that the HW tanks are also vaporsealed, since you have working space between the two and not enclosed wall cavity space.

The floor of the HW enclosure has to have aluminum trapped between foam, and that sandwich is the base, upon which the two HW tanks are placed. Whether to support this foam-aluminum-foam sandwich by legs or to place it flat on the floor, I cannot comment on now. Inside, a layer of strong flat material can cover the top of the sandwich to spread the pressure of the six legs of the two tanks.

David

I have some specific questions on these methods.
1. If I can only use one radiant barrier, but can use two pieces of foam, does the outside piece have to be foam only, without a radiant barrier layer, in order to only have "one radiant barrier"?

2. Should i construct the bottom like the sides, or is there a reason that i need to put the aluminum between the foam for the bottom?

3. I am now leaning toward running the water lines directly into the building, (through the adjacent wall of the insulated water tank space), instead of going up and over through the attic. This would eliminate the need to wrestle with insulating and running the lines in the attic, but would require me to build a chase in the rooms that i would be running the lines through, I could run the lines along the top corner of the walls through 3 rooms and it would be a straight shot to both bathrooms.

4. Do you think PEX would be a good choice of water lines for this project?

Note; I am not going to be able to post pictures on this project sorry.

Thanks for any help!
Molo

 

[Sponsor]

 

[Geniescience]

Why only one good radiant barrier

Foam can be thick, on any side of the radiant barrier, and even on both sides so the radiant barrier is "sandwiched" between foam. Sandwiching the radiant barrier ensures it is only touching foam, which is 90% air. That is why floor insulation works best when the radiant barrier is sandwiched.
- If the radiant barrier is touching air or foam, it works as insulation.
- If the radiant barrier is touching anything else, it works as a conductor, not as an insulator. That is bad. That is not the desired effect.

Your goal is to isolate the radiant barrier instead of letting it come into contact with conductors. In your application, even wood, plastic and rubber should be considered conductors. You don't want the radiant barrier to be touching the support legs of the Hot Water heaters, and you don't want it to be touching the floor of the shed. To get the closest you can to floating in mid-air, you'll have to snadwich it.

If a company sells foam or bubble wrap covered with a radiant barrier on two sides, they probably don't tell you that one of the two radiant barriers is going to be ineffective in most applications.

If you buy foam or bubble wrap with only one radiant barrier on it (on one side only), and if you have too much of it, just double it back over onto itself so that the two radiant barriers are touching.

The thicker the aluminum the better.

david
p.s. Pex has small Inside Diamters. 3/4" Pex is bigger than 1/2" Pex. Both are small. I would use 3/4".
p.p.s. As filler, any foam is good, as insulation against convective and conductive losses in the walls. Any kind, even the cheapest. In a floor sandwich, you'll want compressive strength. Look at Wedi board as one of the top layers, and XPS for floor sandwich filler layers.

 

[Molo]

More ideas

Thanks for all the help David, I'm starting to understand what I need to build. I am going to build a box with the suggested products, and I need to put an access to the water tanks in this insulated box.
Once the water lines get inside the envelope my only concern is building a chase along the upper corner of the rooms to get the lines to the 2 bathrooms. I want this chase to be as inconspicuos as possible and aesthetically acceptable and subtle. Any ideas??

On PEX.... If PEX tends to be smaller in ID, Will one 3/4 line supplying both the tanks be enough?
Can anyone reccomend a good brand to use for a project like this. I've never used PEX before and will have to educate myself on the methods and tools neccesary.

Thanks again,
Molo

 

[Geniescience]

crown mold chase.

Foam glued together. Plaster or drywall compound trowelled on top. Rigid XPS foam for the surface layers, so it stays straight, no waves. Cheap foam inside. Radiant barrier between pipe and wall, pipe and ceiling. Pipe held up with a few threaded rods going into ceiling.

david

 

[Molo]

Getting closer......

Hello

Do I need to use the insulating foam with radiant barrier if this is going to be inside the building envelope? There is going to be a portion of the wall that is uninsulated (old home) and I'm wondering if that is the only section of the chase that needs to be insulated.

Also, David or anyone if you have time please look at the questions from my previous post on this thread.

Any help is greatly appreciated,

Thanks, Molo

 

[Geniescience]

it'll freeze in the attic, won't it?

hi Molo!

Seems i am always on line when you post, or just about to sign in. This telepathy won't always work so well... so maybe I'll have to give you my phone number!

Searched for your other threads, and found twenty or more. Which one did you want me to look at?

The need for a radiant barrier is because you want to optimize or maximize heat retention when the power is out and heat is being lost naturally everywhere. So, yes, I would put a radiant barrier indoors too, following the pipes, as the above diagram shows -- only on the two outside sides, i.e. facing the attic and facing the ouside wall. If the power is out and subzero winds are blowing, the first place to freeze might be the outside wall up where the pipes are near the attic. It'll be below freezing in the attic.

So a radiant barrier is needed, as this might be "weakest" link in the chain.

Same method as the floor sandwich, except you don't need to worry about compressive strength. Under the HW tanks, to effectively create radiant heat reflection you must have an insulated layer first, then a radiant barrier on top, then another insulated layer, and then if you wish a "hard" layer that carries the weight of the HW tanks.

Without this sandwich, the radiant barrier is not working as a heat reflector. ((Remember the boy scout days when you could make a fire with tin foil curved into a half-sphere? That is reflection, and it works for sunlight and for invisible heat too)). Without a reflective-radiative-radiant barrier, a significant portion of heat will flow away, just by radiating through space just like the sun's heat energy does when it travels through a vacuum (empty space) and then hits the ground and keeps on going downward into the ground.

For the average citizen living in an average residential building, the heat loss due to radiative losses may only be 20% of the total -- and the average person doesn't worry about this. Look back at the Quiz questions to see the answers why it is important here in your application. You have a big temperature gradient, and the forces of nature should work on your side when the power goes out for a long time during the coldest weeks of the year.

david

 

[Molo]

chase design

Hello again,

I have some experience with drywall and plaster/joint compound, but I have never applied plaster/joint compound to rigid foam insulation. Do you have experience with this? Do you tape the joints? I have never done this so I am in the dark. It almost seems like it would be easier to run them in an attic chase so that I didn't have to worry about aesthetics.

Thanks again,

Molo

 

[Geniescience]

Recap from the beginning

molo,
-------------
* 1 Methods of insulation in buildings
<...>
o 1.3 Airtight envelope
o 1.4 Isolating to prevent heat bridging
o 1.5 Radiant barriers
* 2 Materials used to insulate buildings
o 2.1 Spray foams (foam-in-place)
o 2.2 Rigid panels

------------
No getting fussy with ... manufactured products.
- 3 a.) the big picture, not missing out on significant concepts, and then
- 3 b.) the little detail, not missing or omitting to seal little air leaks.
------------

Your goal, is to stop conduction and convection by trapping air, and to reflect the radiative form of heat using a reflective radiant barrier.

This explains why it does not matter how much foam, how many types of foam, and whether the foam is bought as a rigid panel, or as a sheet of floppy pink stuff that comes in a roll, or as expanding foam that you spray in place, or even whether you are recycling last year's plastic grocery bags scrunched up and shoved into cavities. They are all good, and a combination of all of these kinds will give you more air blockage and better "shape control" than if you just use one kind of foam. Ten inches of foam is twice as good as five inches of foam, in terms of how much "slowing down the heat transfer process" you achieve. Slowing heat loss down is the goal, and foam works on two out of three heat transfer processes. By the way, fiberglass is also VERY good at slowing down heat transfer, and if you can get some floppy fiberglas mesh, you can use it too, as a layer embedded in the foam, without adding resin to the fiberglass.


The third heat transfer mechanism needs a radiant barrier, and only one. Why only one radiant barrier? Because two radiant layers separated by a space don't work together and don't get "added" together. In fact they cancel each other out a little bit. To "slow the heat loss down", it is better to buy thick aluminum (flat stock or flashing) rather than the thin stuff you usually see associated with thermal insulation made for run-of-the-mill applications, but don't sweat this if you use thin aluminum. Copper and aluminum are the best reflectors, and that explains why I always come back to aluminum. You could use copper too. Other sheet metals too. But only one single layer. It could even be the outer layer that is visible to the world and it could be flashing and weather shield, and if that is the best way to build your thing, so be it, and you won't need to buy a "special" heat reflective layer with your foam panels.

How it looks esthetically when you build something indoors, will depend on a lot of factors, and that may be worth another thread. I might use fiberglass tape made for plaster. How long is this chase going to run?

David

 

[Molo]

chase details

Hello,

The chase will be approximately 50' long by the time i run it down to the 2nd bathroom. Yikes! The fact that I will be insulating this thing inside and then dealing with aesthetics makes me think that I could forget the aesthetics and install in the attic (if it needs to be insulated either way.) This has got me thinking about the location of all water pipes in these cold northern towns, even on new construction. Most kitchen sinks face an outside wall and that's where the water lines are.

PS. Lets stay on this thread so as to treat it as an overview of a complete project.

Molo

 

[Geniescience]

yes, in an outside wall, water pipes can and do freeze if water doesn't run in them. When people go away on a vacation, pipes often freeze in old homes. Running a little water now and then brings not-as-cold water up into the pipes. Ground water is always a few degrees above freezing, or more.

I guess this just goes to show that an airtight insulated sleeve containing the pipes is a really big first step. So far I have not heard of pipes freezing in a well insulated modern building with an airtight vapor barrier between the pipes and the outdoors. Although it still can happen, the forces of nature are working with you and not against you, since cold air is blocked and the warmth of the building reaches the pipes to counteract the cold from the outside coming through the wall.

molo, since the whole assembly is 50' or so, i think it is good to keep it simple and rustic, and just aim to achieve one main objective, that is making sure that it is airtight by filling the rigid foam seams with expanding foam. Then put flashing on top.

david

 

[Molo]

chase detail

Still deciding on the chase location: If I take the water ine chase through the attic the water lines will be running perpindicular to the trusses. Therefore I will be doing some fancy cutting to get the foam to fit tightly over each truss. It will be a challenge.
If I go indoors Im thinking of putting wood nailers on the ceiling and wall, placing foam in front of them and then installing a finish board that will be at a 45 degree angle with the floor to be the face of the chase. That way I can avoid doing plaster work. Just have to paint or caulk and paint.

Any input would be appreciated

Molo

 

[Molo]

r-value discussion

Ok,
As long as it's not a problem I might buy this stuff, He had a pile of 14 sheets that were 2" thick with radiant barrier on both sides. He's asking $200 for the pile. I couldn't find an R-value marked on it though. It's a Georgia Pacific product so maybe i could call them with a serial number and ask.
It's interesting, It seems as if it's hard to get a high R-value on the rigid foam boards. On the other hand you can buy fiberglass bats that are up to R-36. I'm now wondering If I want a box of rigid foam with fradiant barrier, coverd by a high R-value fiberglass. I plan on starting this project next week.
Also, considering CPVC vs. Pex. Do you have an opinion on CPVC?

Thanks for all of your help on this project,
Molo

Quote:
Originally Posted by geniescience
Quote:
Originally Posted by molo
Hello genie,

OK, thanks for your response,
I asked because I seemed to remember you specifying one radiant barrier not 2 for the project. Just wanted to check on that.

Molo


yes, when you have two radiant barriers, it is not twice as good.

Within a few hundred years the manufacturers' engineers will have told the marketing people often enough, and the product will be laughed at, as "look what people used to do in previous generations".


david

 

[Geniescience]

looks like you posted a part of an ongoing discussion, to get it back on a public thread.

The r-value number is misleading in many ways. It is derived from a highly controlled lab test without moisture and or convection currents and air flow. Ask the great outdoors if it has air and moisture in it !! Then, secondly, the R-value test does not control the amount of heat transfer due to conduction / radiation respectively. There is no standard test designed to measure the reflection of radiated heat energy alone. So trying to associate R-values with radiant barriers is difficult and inappropriate. Remember that radiated heat is a significant means of heat transfer; the sun's heat arrives by radiating through space and not by conduction. At night the absence of heat (i.e. cold) is the exact same phenomenon, with the heat radiating described mathematically as the linear opposite. Roofs and exterior walls thus need radiant protection, in a cold climate.

Historically, fiberglass batts became the preferred choice for residential construction in the late 20th century; it is useful to understand how this evolved, as there is no inherent advantage to batts. I'm sure you have noticed that commercial and industrial construction do not use batts. In the 1970's in response to oil price shocks, many US state governments sought to cut home heating oil usage by increasing building code insulation requirements for all new housing. At the same time, O**ns C**ning fiberglass lobbied intensively to convince the building officials who wrote and administered the four separate building codes then used in the USA. They aimed to eliminate other kinds of housing insulation material (such as polyurethane) on safety or hazard grounds which are no longer concerns today. The result was that O**ns C**ning successfully lobbied for mandatory 2" x 6" (50 x 150 mm) wall framing with fibreglass insulation.

Today, rigid foam is safe. No comparison to then. But building practices change gradually unless a shock happens.

Conclusion: it is not about R-values. It's about quality of work, to get airtight-ness. Secondly, batts are not all that good after all. They fit between studs, and that is all.

Remember that is is ALL about quality of work and not about the product itself. No air gaps. You'll still need expanding foam to encase it all and seal the gaps. Don't go wild over any one product or its claim to fame like its apparent R value in a lab.

David

 

[Jadnashua]

The foam may be in the order of R4/inch. R36 fiberglass is likely around 15" thick, or about R2.2/inch.

 

[Molo]

Along The Same Lines As This Project:

I Thought I Could Run Water Lines In Some Of The Insulated Flex Duct Used For Forced Air Systems> It Is Rated A Bit Higher Than R Four> If I Put The $inch Duct Inside A Twleve Inch Duct I Will Get A Bit Higher Than R Eight> Is This High Enough R To Keep The Pipes From Freezing In An Attic? Would R Four Be High Enough? The Pipes Would Be Above The Insulation In An Attic In New York State Where It Gets As Cold As Minus Fifteen>

Tia<
Molo

 

[Jadnashua]

Running water lines in an unheated space like your attic in NYS is just asking for them to burst IMHO. Insulation only slows heat movement, but how much is there after sitting overnight with no flow? You need to get them closer to the building's heated envelope.