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Old 09-26-14, 08:25 PM   #41
AC_Hacker
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Quote:
Originally Posted by Snail View Post
The info in this thread is really good. However, there is another factor that nobody has mentioned. Maybe we are unlucky, or just klutzes, but over the decades we have had several “indoor floods”. There was the burst washing machine hose, the unattended filling sink, the dishwasher bearing seal failure and, the latest, a spectacular DIY disaster by yours truly.
Wow! Your indoor flooding is an atrocity, but your writing is amazing.

A lot of good cautionary tales, all together, in one saga of serial disasters. Are you sure that you are not Icelandic?

Thank for all the good information.

So, would perforated aluminized reflective material have made a difference for you?

-AC

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Old 09-27-14, 06:31 PM   #42
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Default Perforated foil

Not Icelandic, although some of my ancestors do figure in the Orkneyinga Saga. Whatís unlucky about being Icelandic anyway? The fact that their ancestors made it across the far North Atlantic in open boats seems astonishingly lucky to me!

Over 4 decades of house ownership, a few minor disasters like those I mention donít seem too unusual surely? And the flooding atrocity as you put it was actually a bit of undeserved good luck, as it made me aware of the fact that the insulating film was risky and in fact had already exacerbated a poor exterior deck detail that was directing water into the perimeter joist at one point. (If Iím a klutz, you should see the DIY workmanship of some of the previous owners of houses Iíve bought Ė shudder!)

From the early 1970ís until at least the early 90ís, underfloor insulating using perforated film was a common new construction detail. It was laid over the floor joists with a 75 to 100mm drape between each joist, just before the floor was placed over it. The theoretical R-value is about 2.2 but real values were a little over 1.3. However it was extremely vulnerable to wind, even though it was only used for houses with continuous perimeter walls (with ventilation ports). Even if it wasnít ripped out, measured values deteriorate to about R-0.8 over time. (R-values in SI units, multiply by 5.7 for US units).

As a general but related observation, it seems to me that virtually every technique for insulating houses appears to have major downside risks of encouraging condensation and trapping moisture. I'm hoping that a conditioned crawl-space may be less risky?

We seem to be avoiding colds at the risk of being poisoned by some deadly mould spore or having our houses, or at least our finances, collapsing as a result of structural failure! I exaggerate Ė but maybe not much? Perhaps we should just harden up. Now those guys in the sagas wouldnít be having with this insulation for softies. If you are cold, just get some vigorous exercise hacking off a few heads!
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Old 09-27-14, 11:18 PM   #43
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Default Air Gap over foil

Originally Posted by AC_Hacker


I'm pretty sure that you need an air gap between the radiating surface and the reflective material. I've seen recommendations of 1/2 inch to 1 inch. But the wavelength of IR is very short (< 1 mm), so I think that the gap can be small.

-AC

You certainly do need an air gap. However, although my physics is very rusty, I canít for the life of me think what the IR wavelength has to do with anything! (Around 10microns at these temperatures). Iím sure that I would have remembered something if it did.

For double glazing Ĺ to 1 inch is recommended as an air gap. This is an optimal compromise between the benefit of minimising conduction through the air, for which thicker is better, and damping down convention currents, which requires a thin air gap. However, under the floor is a completely different situation. Since the air will be hottest at the top of the air gap, convection will be supressed. Furthermore, the top of the joists and the underside of the floor will be fairly uniform in temperature, whilst the foil and the joist where the foil meets it will also be at a uniform temperature. Where then is the driving temperature difference for convection cells to develop?

My guess is that the bigger the air gap the more ďfreeĒ insulation you will get.

PS How do you quote properly on this blog? Is there a page anywhere with this type of info?
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Old 09-28-14, 05:42 AM   #44
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More than 3/4" air gap (in a window) promotes air movement by convection and therefore heat loss. Most double glazing is limited to that. Triple is usually 2 x 3/8 or 2 x 1/2'
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Old 09-28-14, 06:52 AM   #45
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Default Reflective foil insulation

This web page may be of interest.

Radiant Barriers :: Bubble Foil Insulation :: Reflective Insulation

Seem as if the NZ values for foil are even a bit optimistic.
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Old 09-28-14, 10:23 AM   #46
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Quote:
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...PS How do you quote properly on this blog? Is there a page anywhere with this type of info?
If you want to quote a previous post, you use the little "QUOTE" button thingy at the bottom right of every post.

However, if you want to quote something that isn't a previous post, you must be forced to be creative...

You need to make a 'tag' that preceeds and then follows the text that you want to quote.

A tag is identified by the robot software as some 'tag text' delimited by square brackets. I can't show you an example because the robot will think that my tag example is a real tag, so for this example I will use curly braces instead of the square bracket, so that you can get the idea.

Lets say that you want to quote the text: THIS IS A QUOTE EXAMPLE

You would put the quote tag {QUOTE} at the beginning of your text, and at the end of your text, you would put the 'end quote' tag {/QUOTE} ...

So it would look like this:

{QUOTE}THIS IS A QUOTE EXAMPLE{/QUOTE}

But after the robot does its work, it will look like this:

Quote:
THIS IS A QUOTE EXAMPLE
There you go, simple as that.

-AC
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Old 10-17-14, 01:22 PM   #47
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Any updates on the floor insulation work?
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Old 10-17-14, 05:34 PM   #48
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Quote:
Originally Posted by Daox View Post
Any updates on the floor insulation work?
Yes, updates for sure...

Phase 1 is complete, which is installing the 2" EPS layers under the floor, as per this diagram:



Overall, this involved:
  • Installing vapor barrier on ground and part way up the foundation stem walls.
  • Installing 1/2" spacer strips next to floor joists.
  • Fitting 2" EPS rigid insulation board.
  • Sealing all cracks between EPS & wood and EPS & EPS with 1-part foam sealer.
  • Sealing all potential air leak areas above the sill plate and below the floor structure with EPS & 1-part foam.









Before, I had only sub-floor & floor which gave me an abysmal
  • Floor & subfloor = R-1.5
  • Inside air film = R-0.68
  • outside air film = R-0.17
TOTAL = R-2.35


Now, I calculate:
  • Inside air film above floor = R-0.68
  • Floor & subfloor = R-1.5
  • Inside air film below flooring = R-0.68
  • R value of 1/2" air space = R-1
  • Inside air film above EPS (one surface reflective) = R-2.23
  • Two inches EPS = R-4/in or R-8 total
  • Outside air film below EPS = R-0.17
TOTAL = 14.26 - 18% = R-12

[NOTE: the final value has been reduced by 18% due to thermal bridging.]

At this point I should be OK for the winter... at least it's way better than it was for the past 122 years.

I gotta say, it doesn't feel like a dank nasty crawl space any more, more like a room... not that I am tempted to spend any leisure time in there!

Best,

-AC
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Old 10-17-14, 08:26 PM   #49
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Congrats as doing all that work above your head is not easy on the arms, or neck, or back!
I've been spraying 2 component spray foam on my crawl space walls and its tough work.

as far as this, IIRC
Quote:
Inside air film below flooring = R-0.68
R value of 1/2" air space = R-1
Inside air film above EPS (one surface reflective) = R-2.23
IIRC, You only calculate an air film r value when its against an open space, not in an enclosed area - you get one on each side of the total assembly. I believe you need at least a solid 3/4" to 1" to get R1 for air. You reflective surface going up looks about right, although I've always read 3/4" was required for an airspace.

As another comparison I've read a radiant barriers R value going up is about the same as standard eps insulation with 3/4" air space, so R4, so you should have a little under R3 for that radiant space.

Really the air seal is where your making your money.
I'm planning on trying to spray foam my underside for about an inch, and then apply a roll radiant barrier against it and around the joists, for roughly R20 in the winter. Problem is it has to be clean otherwise the spray catches on everything like spider webs or specs of dirt or sticking out nails.

thanks for the details and pics
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Old 10-18-14, 01:26 AM   #50
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Congrats as doing all that work above your head is not easy on the arms, or neck, or back! ...thanks for the details and pics
All the random glops of foam look quite a fright.

Before I start phase 2 (install mineral wool) I'm going to get in there and trim off the glops and at the same time, inspect closely for, and fix any voids in the 1-part foam.

Mineral wool is really great stuff to work with, as you can cut it to shape and push it in tight, without leaving unintended air spaces.

Maybe this will happen before winter really sets in, maybe not.

Already I can feel the difference in the kitchen.

Fortunately, I have had a data-logger monitoring and recording ambient temperature and also each room in the house, including the kitchen, for about a year now. So I'll be able to measure the difference, not just feel it.

-AC

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