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#41 | |
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![]() Quote:
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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#42 |
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![]() Not Icelandic, although some of my ancestors do figure in the Orkneyinga Saga. What’s 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 don’t 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 I’m a klutz, you should see the DIY workmanship of some of the previous owners of houses I’ve bought – shudder!) From the early 1970’s until at least the early 90’s, 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 wasn’t 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 – but maybe not much? Perhaps we should just harden up. Now those guys in the sagas wouldn’t 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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#43 |
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![]() 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 can’t for the life of me think what the IR wavelength has to do with anything! (Around 10microns at these temperatures). I’m sure that I would have remembered something if it did. For double glazing ½ 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 “free” 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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#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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#45 |
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![]() 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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#46 | ||
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![]() Quote:
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:
-AC
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#47 |
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![]() Any updates on the floor insulation work?
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#48 |
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![]() 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:
Before, I had only sub-floor & floor which gave me an abysmal
Now, I calculate:
[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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#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:
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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#50 | |
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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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I'm not an HVAC technician. In fact, I'm barely even a hacker... Last edited by AC_Hacker; 10-18-14 at 02:29 AM.. |
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