Green Building Bible, Fourth Edition |
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These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.
Posted By: WatchItyou would need more than, equiv 80mm diam holeI think I'd sooner be on the lee side of a curtain of glassfibre roll, than a brick wall with 80 diam holes @ 1m c/cs. Anyway, neither could be called significantly airtight.
Posted By: WatchitBut Mike, I see that as the point in using a steady state test method. Yes granted the induced air flow may or may not be similar to typical conditions in situ, but at least it is giving a level playing field on which ther performances are based. Otherwise you would have a different air flow for each product tested.
Posted By: fostertomand you in particular Biff have consistently stonewalled alternative interpretations of physics that have been offered. 'Stonewalled' means not disputed - just ignored.
Posted By: biffvernonthe size of air gap next to the mulitfoil has no bearing on the performance of the multifoil itself. The foil only 'knows' about the first half light wavelength.That is true as far as I'm concerned - no dispute - in fact my boffin colleague is currently exploring the theoretical possibility (not in a MF context) that even that gap is unnecessary.
Posted By: biffvernonwhile the outer foils can contribute a significant insulation effect the internal foils suffer rapidly from diminishing returnsThat is the point on which you've 'stonewalled' - actually I now recall, it's nothing to do with interpretations of laws of physics!
Posted By: djhhis dynamical inadequacy obsessionI'm proud of my obsession - keeping it alive because something tells me there is something there.
Posted By: Mike Georgeothers [Biff and Tom?] discount the thermal value of an air gapNot at all - I just don't want to rely on it in 'why multifoils work'.
Posted By: Mike GeorgeYes, agree, in theory [still] air has a very good thermal conductivity, allthough once convective currents come into play the resistance diminishes. For some reason others [Biff and Tom?] discount the thermal value of an air gap in this context, though, I assume, accept it say a double glazed unit scenario
Posted By: biffvernonAnd, as I've said many times and nobody has demonstrated me wrong, yet the point still gets repeated, the size of air gap next to the mulitfoil has no bearing on the performance of the multifoil itself. The foil only 'knows' about the first half light wavelength.
Posted By: biffvernonOf course air is a good insulator. The point is it doesn't become a better insulator because it's next to a bit of foil. And you can't say multifoil is great when it's the air outside the multifoil that is providing the benefit.
Posted By: CWatters25mm. That's the size of the battens they recommend either side. The foil is nominally 30mm thick where uncompressed so the air gap could be 25-15=10mmNo - the air gap will unavoidably be 25-30 = -5mm - the MF will be compressed 5mm and in intimate contact with both adjoining surfaces. In other words the usual batten recommendations are rubbish.
Posted By: fostertomPosted By: djhhis dynamical inadequacy obsessionI'm proud of my obsession - keeping it alive because something tells me there is something there.
Posted By: fostertomWhat was under developoment, until industry conspiracy destroyed the MF market, was stand-off brackets (a bit like cav wall ties that restrain partial cav fill) that wd keep the MF taut and centred in the cavity, compressed/in contact only at the clips - and the clips wd be avail with a variety of endings to accept various board facings, and at their other end a variety of endings to mount to various backings. This wd make MF's claimed insulative value avail for fitting within a trad 50mm masonry wall cavity.
Posted By: Paul in MontrealSurely the cavity wall is not suitable for passivhaus-level insulationTrue, it's not, but with MF's claimed values, and no doubt further improved ditto under development, then trad 50 cavity or perhaps 100 might make a comeback, which wd delight a lot of people.
Posted By: Paul in Montrealfor a retrofit, I can't see how you'd get the MF in there in the 1st placeQuite - I wasn't suggesting that.
Posted By: Mike GeorgePosted By: biffvernonOf course air is a good insulator. The point is it doesn't become a better insulator because it's next to a bit of foil. And you can't say multifoil is great when it's the air outside the multifoil that is providing the benefit.
So to clarify then, you accept that the airgap next to the foil is reducing the heat lost from the conditioned space, but you think the size of the airgap makes no difference?
Posted By: Paul in MontrealSurely the cavity wall is not suitable for passivhaus-level insulation.
Posted By: Mike GeorgeOr perhaps you are stonewalling as Tom suggests?To me, stonewalling means no response/no acknowledgement at all - not mere diversionary/slipperiness.
Posted By: Mike GeorgeI don't understand your response to the very simple question I asked, and which you have highlighted. A simple yes or no will suffice. Or perhaps you are stonewalling as Tom suggests?
Posted By: biffvernonAnd, as I've said many times and nobody has demonstrated me wrong, yet the point still gets repeated, the size of air gap next to the mulitfoil has no bearing on the performance of the multifoil itself. The foil only 'knows' about the first half light wavelength.
Posted By: Mike GeorgeWhether this is purely down to the stillness of the air, [and lets face it its not the same as a sealed double glazed unit]or some other factors I know notHow is it any different from a sealed double glazing unit (except for the lack of argon). Even the low-E coating on the glass is essentially the same as the out foil layer on the multifoil?
Posted By: Mike GeorgePerhaps you can tell me if the studies you mention encapsulated the air adjacent to the foil in the same way that a factory sealed double glazed unit does?In a similar way - they treated the cavities formed between the drywall and adjacent insulation as entirely surrounded by wood strapping and essentially sealed to moisture transport. They did model convection in the cavities (and, of course, found a difference between cavities that had horizontal straps versus vertical, for the same overall cavity volume. The vertical spaces were worse, of course, because the convection had more vertical space to circulate. They also modelled the radiant barrier effect of any foil facings on the insulation and did models for both faced and unfaced insulation, finding that the foil facing does improve performance by around 10% on average.
Posted By: Mike GeorgePaul, my point was in response to Biff's insinuation that the size of the air gap makes no difference.Biff's insinuation, if he'll pardon me, is that the airgap makes no difference to the radiant barrier effect of the foil, so long as there is a gap. Of course, for convection, it does make a difference, as is the case with double/triple glazing, though the thickness of the gas gap does depend somewhat on the gas used.