|
Home > Archive > Alternative Power sources > September 2006 > US R-values of radiant barriers
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
US R-values of radiant barriers
|
|
| nicksanspam@ece.villanova.edu 2006-07-28, 9:25 am |
| Here's one way to estimate the R-value of a radiant barrier based on the air
gap and the emissivities and surface temps and the direction of heatflow from
http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf
10 SCREEN 9:KEY OFF:DIM HC(18,6)
20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
200 FOR I=1 TO 18'read data table
210 FOR J=1 TO 6
220 READ HC(I,J)
230 NEXT:NEXT
240 T1=105'temperature of surface 1 (F)
250 E1=.03'emissivity of surface 1
260 T2=75'temperature of surface 2 (F)
270 E2=.8'emissivity of surface 2
280 L=2'air gap (valid range: 0.5-3")
290 LI=INT(2*L+.5)'length table index
300 HF=0'heatflow 0-down,1-sideways,2-up
310 E=1/(1/E1+1/E2-1)'effective emittance
320 TM=(T1+T2)/2'mean temp (F)
330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
370 PRINT T1,E1,T2,E2
380 PRINT L,HF,R
T1 (F) E1 T2 (F) E2
105 .03 75 .8
gap heatflow US R-value
2" 0 (down) 7.146456
With more than one space in series (eg double-foil foamboard spaced away
from a basement wall), we can't just add R-values. We only know the overall
temp diff, so we have to iterate to find a solution. It's no surprise that
the FTC prohibits makers from advertising R-values for radiant barriers
to avoid confusing the public.
Nick
| |
|
| nicksanspam@ece.villanova.edu wrote:
> Here's one way to estimate the R-value of a radiant barrier based on the air
> gap and the emissivities and surface temps and the direction of heatflow from
> http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf
Nick,
How does this work out for the double bubble?
<URL: http://www.blueridgecompany.com/rad...nic/189#pricing >
It seems to me there are two ways to go for the underfloor insulation
for staple up radiant.
One is foil backed fiberglass insulation with an airspace. That is hard
to find! The other would be double bubble stapled on the joists. It
seems to me that would minimize heat loss through the joists themselves
as they would be uninsulated elsewise. Any thoughts?
Jeff
>
> 10 SCREEN 9:KEY OFF:DIM HC(18,6)
> 20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
> 30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
> 40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
> 50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
> 60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
> 70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
> 80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
> 90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
> 100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
> 110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
> 120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
> 130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
> 140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
> 150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
> 160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
> 170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
> 180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
> 190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
> 200 FOR I=1 TO 18'read data table
> 210 FOR J=1 TO 6
> 220 READ HC(I,J)
> 230 NEXT:NEXT
> 240 T1=105'temperature of surface 1 (F)
> 250 E1=.03'emissivity of surface 1
> 260 T2=75'temperature of surface 2 (F)
> 270 E2=.8'emissivity of surface 2
> 280 L=2'air gap (valid range: 0.5-3")
> 290 LI=INT(2*L+.5)'length table index
> 300 HF=0'heatflow 0-down,1-sideways,2-up
> 310 E=1/(1/E1+1/E2-1)'effective emittance
> 320 TM=(T1+T2)/2'mean temp (F)
> 330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
> 340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
> 350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
> 360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
> 370 PRINT T1,E1,T2,E2
> 380 PRINT L,HF,R
>
> T1 (F) E1 T2 (F) E2
>
> 105 .03 75 .8
>
> gap heatflow US R-value
>
> 2" 0 (down) 7.146456
>
> With more than one space in series (eg double-foil foamboard spaced away
> from a basement wall), we can't just add R-values. We only know the overall
> temp diff, so we have to iterate to find a solution. It's no surprise that
> the FTC prohibits makers from advertising R-values for radiant barriers
> to avoid confusing the public.
>
> Nick
>
| |
| nicksanspam@ece.villanova.edu 2006-07-28, 1:25 pm |
| Jeff <dont_bug_me@all.uk> wrote:
>
> How does this work out for the double bubble?
Haven't tried that. You might work it out, if you know the gap width, etc.
http://www.blueridgecompany.com/rad...nic/189#pricing >
> It seems to me there are two ways to go for the underfloor insulation
>for staple up radiant.
>
>One is foil backed fiberglass insulation with an airspace. That is hard
>to find! The other would be double bubble stapled on the joists. It
>seems to me that would minimize heat loss through the joists themselves
>as they would be uninsulated elsewise. Any thoughts?
I would staple on foil or thin double-foil foamboard.
Nick
| |
|
|
<nicksanspam@ece.villanova.edu> wrote in message
news:ead104$j4d@acadia.ece.villanova.edu...
> Here's one way to estimate the R-value
> of a radiant barrier based on the air
> gap and the emissivities and surface
> temps and the direction of heatflow from
It is?
The British Advertising Standards Authority got Actis, a French company,
claiming their reflective foil insulation is 'Equivalent to 200mm of
traditional Rockwoool insulation'. A complaint has been upheld after ASA
went to independent technical experts.
The judgement can be seen at:
http://tinyurl.com/s6c2p
Think hard before you buy.
| |
| m Ransley 2006-07-28, 5:25 pm |
| I dont believe Reflextic results, isn`t it amazing no other major
insulation manufacturer can capitalise on this. If there were true
independant tests I would think differently.
| |
|
|
<nicksanspam@ece.villanova.edu> wrote in message
news:ead104$j4d@acadia.ece.villanova.edu...
> Here's one way to estimate the R-value of a radiant barrier based on the
> air
> gap and the emissivities and surface temps and the direction of heatflow
> from
> http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf
>
> 10 SCREEN 9:KEY OFF:DIM HC(18,6)
> 20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
> 30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
> 40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
> 50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
> 60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
> 70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
> 80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
> 90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
> 100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
> 110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
> 120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
> 130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
> 140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
> 150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
> 160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
> 170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
> 180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
> 190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
> 200 FOR I=1 TO 18'read data table
> 210 FOR J=1 TO 6
> 220 READ HC(I,J)
> 230 NEXT:NEXT
> 240 T1=105'temperature of surface 1 (F)
> 250 E1=.03'emissivity of surface 1
> 260 T2=75'temperature of surface 2 (F)
> 270 E2=.8'emissivity of surface 2
> 280 L=2'air gap (valid range: 0.5-3")
> 290 LI=INT(2*L+.5)'length table index
> 300 HF=0'heatflow 0-down,1-sideways,2-up
> 310 E=1/(1/E1+1/E2-1)'effective emittance
> 320 TM=(T1+T2)/2'mean temp (F)
> 330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
> 340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
> 350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
> 360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
> 370 PRINT T1,E1,T2,E2
> 380 PRINT L,HF,R
>
> T1 (F) E1 T2 (F) E2
>
> 105 .03 75 .8
>
> gap heatflow US R-value
>
> 2" 0 (down) 7.146456
>
> With more than one space in series (eg double-foil foamboard spaced away
> from a basement wall), we can't just add R-values. We only know the
> overall
> temp diff, so we have to iterate to find a solution. It's no surprise that
> the FTC prohibits makers from advertising R-values for radiant barriers
> to avoid confusing the public.
>
> Nick
Rockwool has a set value and can be compounded. Makers claim all sorts of
wild claim for radiant barriers. To bottom line, what is it the equivalent
to in rockwool in thickness?
| |
|
| News wrote:
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:ead104$j4d@acadia.ece.villanova.edu...
>
>
>
> Rockwool has a set value and can be compounded. Makers claim all sorts
> of wild claim for radiant barriers. To bottom line, what is it the
> equivalent to in rockwool in thickness?
I think that is exactly what Nick has done. But remember fiberglass
blankets are temperature independant (mostly). Radiant barriers are
dependant on the temperature (emisivity is T^3) and the air space can be
treated as a more conventional "R" value. Note that Nick has commented
the code.
Run that for a higher delta temp and you will get a higher R, just a
lower delta temp gives a lower.
Jeff
>
| |
|
|
"Jeff" <dont_bug_me@all.uk> wrote in message
news:Rzxyg.6687$157.6646@newsread3.news.pas.earthlink.net...
> News wrote:
>
> I think that is exactly what Nick has done. But remember fiberglass
> blankets are temperature independant (mostly). Radiant barriers are
> dependant on the temperature (emisivity is T^3) and the air space can be
> treated as a more conventional "R" value. Note that Nick has commented the
> code.
>
> Run that for a higher delta temp and you will get a higher R, just a lower
> delta temp gives a lower.
I am very sceptical of these barriers. What they need to do is have two
identical houses in the same place, one with the barrier and one with
rockwool. Then do data monitoring for a year or more. The British ASA
ruled against Actis, a French maker, as the tests were not good enough.
There is no testing model to explain. After all this time you would have
thought they could have done tests on an Actis Triso9 house and an identical
house without Actis with 200mm of insulation in the walls. If there was a
clear difference I'm sure they would be crowing from the rooftops with all
data printed and freely given out at every bus stop.
This stuff is not cheap. As far as I can see it is expensive bubble wrap -
until proper meaningful realistic independent tests have been undertaken.
| |
|
|
"News" <Nospam@here.com> wrote in message
news:44ca5155$0$17961$892e7fe2@authen.yellow.readfreenews.net...
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:ead104$j4d@acadia.ece.villanova.edu...
>
>
> It is?
>
> The British Advertising Standards Authority got Actis, a French company,
> claiming their reflective foil insulation is 'Equivalent to 200mm of
> traditional Rockwoool insulation'. A complaint has been upheld after ASA
> went to independent technical experts.
>
> The judgement can be seen at:
> http://tinyurl.com/s6c2p
>
> Think hard before you buy.
The link above does not work. Here is the ruling:
Actis Insulation Ltd
Unit 1
Cornbrash Park
Bumpers Farm Industrial Estate
Chippenham
Wiltshire
SN14 6RA
Date: 31st May 2006
Media: Brochure
Sector: Household
Public Complaint From: Gloucestershire
Complaint:
Objection to a brochure for roof insulation. The brochure stated "TRI-ISO
SUPER 9 Insulation for roofs ... Thermally equivalent to 200 mm of mineral
wool when installed in a roof situation, as certified by the European
certifying body, BM TRADA CERTIFICATION (following real building trials,
certification n°0101) ... THERMAL EFFICIENCY equivalent to 200 mm of mineral
wood RT = 5* ... *in situ measured values." The complainant challenged:
1. the claim "Thermally equivalent to 200 mm of mineral wool" and
2. the quoted thermal resistance "RT = 5".
Codes Section: 3.1, 7.1 (Ed 11)
Adjudication:
Actis Insulation Ltd (Actis) said they had stopped advertising TRI-ISO SUPER
9 because it had been replaced with their new product TRI-ISO SUPER 10. They
said the efficiency of their products was demonstrated by their track record
in the market. Actis said they had commissioned BM TRADA Certification Ltd
(BM TRADA) to test, assess and report on the TRI-ISO Super 9 product. They
provided us with a copy of the BM TRADA Certification and Report dated
August 1997 and said that it substantiated their claims. Actis explained
that TRI-ISO Super 9 was different from traditional bulk insulation because
it was a multi-foil product that used layers of reflective foils spaced with
synthetic wadding and foams. They said the product required less space than
traditional bulk insulation and, therefore, internal insulation cavities
could be made smaller and internal useable spaces could be enlarged without
compromising efficiency of insulation. Actis argued that traditional methods
of testing were not appropriate for their product because traditional
methods measured thermal efficiency mainly by conduction and did not take
into account the influences of convection, radiation and change of phase.
They said their product combined various energy transfers of radiation,
conduction, convection and change of state rather than just conduction.
Actis also argued that traditional methods of testing did not allow
representation of the real behaviour of building materials once used on
site. They pointed out that BM TRADA had used "in situ" testing involving a
real external environment with variations in temperature, humidity, etc.
rather than the traditional methods of laboratory testing. Actis maintained
that the BM TRADA Certification demonstrated the thermal efficiency of their
product and provided proof of their claims.
1. Complaint upheld
The ASA obtained expert advice. We understood that BM TRADA had tested
TRI-ISO SUPER 9 and the mineral wool in two separate roof installations.
However, we noted that BM TRADA had not used the standard industry methods
of testing and that the report provided by Actis did not include sufficient
detail to support their own methods of testing.
We acknowledged that BM TRADA Certification was a leading multi-sector
certification body accredited by the United Kingdom Accreditation Service.
We considered that the BM TRADA report did not provide enough detail to
support their methodology instead of the methodology employed by the
internationally recognised ISO industry standards. We concluded Actis had
not substantiated the claim. We noted the ad was no longer appearing but
told Actis not to repeat the claim in future advertising until they were
able to provide sufficient substantiation.
2. Complaint upheld
We understood that RT was a symbol of total thermal resistance and typically
had the standard unit of measurement of mēK/W. We noted that the claim
"RT=5" was not qualified by any recognised units of measurement e.g. mēK/W
and a small footnote stated only "in situ measured values" without further
explanation. Because the value of 5 was not qualified by any recognised
units of measurement, we considered the claim "RT=5" was ambiguous and
should be qualified in future. However, we noted that the BM TRADA report
did specify an overall resistance (RT) of 5.0mēK/W derived from the in situ
testing. We understood that the in situ measured values did not meet with
ISO recognised international standards for determining declared and design
thermal values for building materials and products.
We considered that the BM TRADA report did not include sufficient detail to
demonstrate the validity or robustness of their testing methodology instead
of the methodology employed by ISO standards. We concluded that the report
did not substantiate the claim " RT=5". We told Actis to remove the claim
until they were able to provide sufficient substantiation.
The brochure breached CAP Code clauses 3.1 (Substantiation) and 7.1
(Truthfulness).
| |
| nicksanspam@ece.villanova.edu 2006-07-29, 9:25 am |
| News <Nospam@here.com> wrote:
> The British Advertising Standards Authority... [objected to] a brochure
>for roof insulation. The brochure stated "TRI-ISO SUPER 9 Insulation for
>roofs was... Thermally equivalent to 200 mm of mineral wool when installed
>in a roof situation, as certified by the European certifying body, BM TRADA
>CERTIFICATION (following real building trials...
>... Actis said they had commissioned BM TRADA Certification Ltd (BM TRADA)
>to test, assess and report on the TRI-ISO Super 9 product. They provided us
>with a copy of the BM TRADA Certification and Report dated August 1997 and
>said that it substantiated their claims... They pointed out that BM TRADA
>had used "in situ" testing involving a real external environment with
>variations in temperature, humidity, etc. rather than the traditional
>methods of laboratory testing...
>... We understood that BM TRADA had tested TRI-ISO SUPER 9 and the mineral
>wool in two separate roof installations. However, we noted that BM TRADA
>had not used the standard industry methods of testing and that the report
>provided by Actis did not include sufficient detail to support their own
>methods of testing.
>
>We acknowledged that BM TRADA Certification was a leading multi-sector
>certification body accredited by the United Kingdom Accreditation Service.
>We considered that the BM TRADA report did not provide enough detail to
>support their methodology...
.... ie they faulted the test documentation, vs the result.
>We understood that RT was a symbol of total thermal resistance and typically
>had the standard unit of measurement of mēK/W. We noted that the claim
>"RT=5" was not qualified by any recognised units of measurement e.g. mēK/W
>and a small footnote stated only "in situ measured values" without further
>explanation. Because the value of 5 was not qualified by any recognised
>units of measurement, we considered the claim "RT=5" was ambiguous and
>should be qualified in future.
.... and they faulted the lack of explicit units in the advertised result.
>However, we noted that the BM TRADA report did specify an overall resistance
>(RT) of 5.0mēK/W derived from the in situ testing...
Picky, picky. Reflectix does advertise some system R-values:
http://www.reflectixinc.com/script/...oduct.asp?ID=64
http://www.reflectixinc.com/script/...oduct.asp?ID=77
www.majorgeothermal.com/PDFs/Reflect/Solutions.pdf
The US R16.8 crawl space number is interesting.
Nick
| |
| daestrom 2006-07-29, 1:25 pm |
|
<nicksanspam@ece.villanova.edu> wrote in message
news:eafk20$euf@acadia.ece.villanova.edu...
> News <Nospam@here.com> wrote:
>
>
>
>
> ... ie they faulted the test documentation, vs the result.
>
>
> ... and they faulted the lack of explicit units in the advertised result.
>
>
> Picky, picky. Reflectix does advertise some system R-values:
>
> http://www.reflectixinc.com/script/...oduct.asp?ID=64
> http://www.reflectixinc.com/script/...oduct.asp?ID=77
> www.majorgeothermal.com/PDFs/Reflect/Solutions.pdf
>
> The US R16.8 crawl space number is interesting.
>
An important question here is how does other insulation perform 'in-situ' if
measured the same way as this product.
If this product can achieve an RT=5 'in situ', that means the overall
measured insulative performance is 5 m^2-K/W. That performance includes the
affects of convection and radiant heat transfer from the living space to the
product, and from the product to the environs on the other side.
But what is deceptive about this, is that if I were to put a simple piece of
conventional building insulation that has an RT=5 value in the same
circumstance, it would undoubtedly have an 'in situ' performance that is
*better* than 5. Because added to the material's own RT=5, would also be
the affects of the convective layers on each side (just like this product),
and the radiant transfer to/from the surfaces.
Unless this products RT value is calculated by taking the 'in-situ'
performance and *subtracting* the insulative performance of those items
common to *all* installations, the RT value is inflated by those other
factors. Thus when compared with other materials tested in the more
traditional manner, it overstates this product's performance.
daestrom
| |
|
|
| nicksanspam@ece.villanova.edu 2006-07-29, 1:25 pm |
| daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
[color=darkred]
>Unless this products RT value is calculated by taking the 'in-situ'
>performance and *subtracting* the insulative performance of those items
>common to *all* installations, the RT value is inflated by those other factors.
In this case, one would hope they derived by subtracting. Nobody seems
to have disputed the result that it worked as well as the rock wool did.
[color=darkred]
That number includes the other stuff, as the FTC-mandated "system R-value,"
with a substantial contribution from the foil surface. A non-radiant maker
could also legally advertise a system R-value in the US.
Nick
| |
|
| daestrom wrote:
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:eafk20$euf@acadia.ece.villanova.edu...
>
>
> An important question here is how does other insulation perform
> 'in-situ' if measured the same way as this product.
>
> If this product can achieve an RT=5 'in situ', that means the overall
> measured insulative performance is 5 m^2-K/W. That performance includes
> the affects of convection and radiant heat transfer from the living
> space to the product, and from the product to the environs on the other
> side.
>
> But what is deceptive about this, is that if I were to put a simple
> piece of conventional building insulation that has an RT=5 value in the
> same circumstance, it would undoubtedly have an 'in situ' performance
> that is *better* than 5.
Conventional insulation would only be between the floor joists. For 2
bys at 16" centers that means that 12.5% of the area is the insulation
value of only the joist. I would think that would be around a US R6 for
a 2 * 6. There will be a point of diminishing returns for conventional
insulation, just because of that. Don't forget that under most floors
you have a maze of plumbing and wiring and that has to be worked around
with conventional insulation.
The more interesting question in my mind, is whether this would be a
good afterfit for an existing structure. It certainly would be easier
(crawl spaces are no fun!) to install and it would be a complete seal.
It seems to me that most energy lost is in existing structures rather
than new construction. The option of tearing down the old house and
building a new does not exist for most people.
I would be delighted to have a US R 16.8 floor in my '20s house. At
this point underfloor radiant with radiant bubble looks attractive, not
sure which way I will go and I'm open to other suggestions (like foil
backed iso).
Jeff
Because added to the material's own RT=5,
> would also be the affects of the convective layers on each side (just
> like this product), and the radiant transfer to/from the surfaces.
>
> Unless this products RT value is calculated by taking the 'in-situ'
> performance and *subtracting* the insulative performance of those items
> common to *all* installations, the RT value is inflated by those other
> factors. Thus when compared with other materials tested in the more
> traditional manner, it overstates this product's performance.
>
> daestrom
>
| |
|
|
....
> I am very sceptical of these barriers. What they need to do is have two
> identical houses in the same place, one with the barrier and one with
> rockwool. Then do data monitoring for a year or more. The British ASA
> ruled against Actis, a French maker, as the tests were not good enough.
> There is no testing model to explain. After all this time you would have
> thought they could have done tests on an Actis Triso9 house and an
> identical house without Actis with 200mm of insulation in the walls. If
> there was a clear difference I'm sure they would be crowing from the
> rooftops with all data printed and freely given out at every bus stop.
>
> This stuff is not cheap. As far as I can see it is expensive bubble
> wrap - until proper meaningful realistic independent tests have been
> undertaken.
>
Hi,
The FSEC has done radiant barrier work -- here is one report:
http://www.fsec.ucf.edu/bldg/pubs/rbs/
If you go to their site and search on Radiant Barrier, a lot of stuff comes up.
I think that www.SouthFace.org has also done work on radiant barrier.
These are good and independant outfits -- I would tend to belive what they
publish. It seems like the bottom line turns out to be about 10% saving on cooling.
Gary
--
Gary
www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects
----== Posted via droptable.com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.droptable.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
| |
|
|
"Gary" <gary@builditsolar.com> wrote in message
news:1154296180_15373@sp6iad.superfeed.net...
>
> ...
>
> Hi,
>
> The FSEC has done radiant barrier work -- here is one report:
> http://www.fsec.ucf.edu/bldg/pubs/rbs/
I am aware of that and have previously read it. It is quite old now, 1999.
At the time the performance in cold climates from other non-comprehensive
tests in the USA was not too encouraging.
> If you go to their site and search on Radiant Barrier, a lot of stuff
> comes up.
>
> I think that www.SouthFace.org has also done work on radiant barrier.
>
> These are good and independant outfits -- I would tend to belive what they
> publish. It seems like the bottom line turns out to be about 10% saving
> on cooling.
>
> Gary
Actis claim the equivalent of 210mm of Rockwool. I believe they do have an
effect on cooling when pinned to the rafters of a roof. What is the overall
claim for rockwool equivalent thickness for heating by tests in the US?
There must be some ballpark. No one is going to type in Nicks program, they
read the makers blurb, or test results to confirm the blurb.
I have the impression much of any heat saving is because this stuff is
air-tight. More the draught prevention is making the difference rather than
the reflective qualities of the material itself. I hope I am wrong and it
does what they say. If so my attic gets done out in it. Until something
more concrete in realistic more real world testing the jury is still out and
it stays out of my attic. 35C here means I may have to act with the attic by
next summer - but using what has to be determined.
| |
| nicksanspam@ece.villanova.edu 2006-07-31, 3:25 am |
| News <Nospam@here.com> wrote:
>Actis claim the equivalent of 210mm of Rockwool. I believe they do have an
>effect on cooling when pinned to the rafters of a roof. What is the overall
>claim for rockwool equivalent thickness for heating by tests in the US?
The second edition (1998) of Pitts & Sissom's Schaum's Outline on Heat
Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2, ie
US R3.62 per inch, at a rock wool density of 10 lb/ft^3.
>No one is going to type in Nicks program, they read the makers blurb,
>or test results to confirm the blurb.
No need to type much. Just save it in a file, remove the headers, and run it.
Or look at the on-line RIMA Handbook and use a calculator, which takes about
5 minutes.
>I have the impression much of any heat saving is because this stuff is
>air-tight.
That's assumed to begin with, but foil helps. For instance, the RIMA Handbook
says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and 2 above
and below the foil with E1 and E4 = 0.8 boundaries and downward heatflow and
110 F above and 80 below has E = 0.0298 for both airspaces and an overall
dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean temp in
airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 = 87.5. From
Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces. Equation 3
on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219 and 1.124.
Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2 = 18.2,
and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We could
iterate if needed, using these new dTs to find new Tms.
>More the draught prevention is making the difference rather than
>the reflective qualities of the material itself.
No. If we replace the foil above with another E2 = E3 = 0.8 opaque surface,
then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 = 1.026 and
the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the foil with
IR-transparent polyethylene film, the difference is even greater, even though
there's still draught prevention. OTOH, if we add more foils or move the foil
up so there's only one airspace, that doesn't help much in this case, given
the same overall airspace dimension.
Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot more stuff.
>Until something more concrete in realistic more real world testing the jury
>is still out...
Au contraire. This has been settled science for over 50 years :-) See
Robinson and F.J. Powell, "The Thermal Insulating Value of Airspaces,"
Housing Research Paper No. 32, National Bureau of Standards Project NE-12,
National Bureau of Standards, Washington DC (1954), and
Yarbrough, "Assessments of Reflective Insulation for Residential and
Commercial Applications," Oak Ridge National Laboratory Report ORNL/TM 8819,
Oak Ridge, TN (1983), and
Yarbrough, "Estimation of the Thermal Resistance of a Series of Reflective
Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings of
the Conference on Fire Safety and Thermal Insulation, S.A. Siddiqui,
Editor (1990) pp 214-231, and
Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack Reflective
Insulation," Journal of Thermal Insulation 15 137-151, (1991).
Nick
| |
| .p.jm@see_my_sig_for_address.com 2006-07-31, 9:25 am |
|
Nick, you make me want a brain-douche.
On 31 Jul 2006 00:37:34 -0400, nicksanspam@ece.villanova.edu wrote:
>News <Nospam@here.com> wrote:
>
>
>The second edition (1998) of Pitts & Sissom's Schaum's Outline on Heat
>Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2, ie
>US R3.62 per inch, at a rock wool density of 10 lb/ft^3.
>
>
>No need to type much. Just save it in a file, remove the headers, and run it.
>Or look at the on-line RIMA Handbook and use a calculator, which takes about
>5 minutes.
>
>
>That's assumed to begin with, but foil helps. For instance, the RIMA Handbook
>says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and 2 above
>and below the foil with E1 and E4 = 0.8 boundaries and downward heatflow and
>110 F above and 80 below has E = 0.0298 for both airspaces and an overall
>dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean temp in
>airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 = 87.5. From
>Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces. Equation 3
>on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219 and 1.124.
>Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2 = 18.2,
>and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We could
>iterate if needed, using these new dTs to find new Tms.
>
>
>No. If we replace the foil above with another E2 = E3 = 0.8 opaque surface,
>then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 = 1.026 and
>the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the foil with
>IR-transparent polyethylene film, the difference is even greater, even though
>there's still draught prevention. OTOH, if we add more foils or move the foil
>up so there's only one airspace, that doesn't help much in this case, given
>the same overall airspace dimension.
>
>Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot more stuff.
>
>
>Au contraire. This has been settled science for over 50 years :-) See
>
>Robinson and F.J. Powell, "The Thermal Insulating Value of Airspaces,"
>Housing Research Paper No. 32, National Bureau of Standards Project NE-12,
>National Bureau of Standards, Washington DC (1954), and
>
>Yarbrough, "Assessments of Reflective Insulation for Residential and
>Commercial Applications," Oak Ridge National Laboratory Report ORNL/TM 8819,
>Oak Ridge, TN (1983), and
>
>Yarbrough, "Estimation of the Thermal Resistance of a Series of Reflective
>Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings of
>the Conference on Fire Safety and Thermal Insulation, S.A. Siddiqui,
>Editor (1990) pp 214-231, and
>
>Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack Reflective
>Insulation," Journal of Thermal Insulation 15 137-151, (1991).
>
>Nick
--
Click here every day to feed an animal that needs you today !!!
http://www.theanimalrescuesite.com/
Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'
'With sufficient thrust, pigs fly just fine.'
HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
| |
|
| nicksanspam@ece.villanova.edu wrote:
> News <Nospam@here.com> wrote:
>
>
>
>
> The second edition (1998) of Pitts & Sissom's Schaum's Outline on Heat
> Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2, ie
> US R3.62 per inch, at a rock wool density of 10 lb/ft^3.
>
>
>
>
> No need to type much. Just save it in a file, remove the headers, and run it.
> Or look at the on-line RIMA Handbook and use a calculator, which takes about
> 5 minutes.
>
>
>
>
> That's assumed to begin with, but foil helps. For instance, the RIMA Handbook
> says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and 2 above
> and below the foil with E1 and E4 = 0.8 boundaries and downward heatflow and
> 110 F above and 80 below has E = 0.0298 for both airspaces and an overall
> dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean temp in
> airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 = 87.5. From
> Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces. Equation 3
> on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219 and 1.124.
> Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2 = 18.2,
> and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We could
> iterate if needed, using these new dTs to find new Tms.
>
>
>
>
> No. If we replace the foil above with another E2 = E3 = 0.8 opaque surface,
> then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 = 1.026 and
> the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the foil with
> IR-transparent polyethylene film, the difference is even greater, even though
> there's still draught prevention. OTOH, if we add more foils or move the foil
> up so there's only one airspace, that doesn't help much in this case, given
> the same overall airspace dimension.
>
> Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot more stuff.
From The Passive Solar Energy Handbook, Edward Mazria 1979 we have this
in Appendix E.6 Resistance values of airspaces
Horizontal, Heatflow Down
NR=Non Reflective
Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03
Obviously that's all from observations.
What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.
Jeff
>
>
>
>
> Au contraire. This has been settled science for over 50 years :-) See
>
> Robinson and F.J. Powell, "The Thermal Insulating Value of Airspaces,"
> Housing Research Paper No. 32, National Bureau of Standards Project NE-12,
> National Bureau of Standards, Washington DC (1954), and
>
> Yarbrough, "Assessments of Reflective Insulation for Residential and
> Commercial Applications," Oak Ridge National Laboratory Report ORNL/TM 8819,
> Oak Ridge, TN (1983), and
>
> Yarbrough, "Estimation of the Thermal Resistance of a Series of Reflective
> Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings of
> the Conference on Fire Safety and Thermal Insulation, S.A. Siddiqui,
> Editor (1990) pp 214-231, and
>
> Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack Reflective
> Insulation," Journal of Thermal Insulation 15 137-151, (1991).
>
> Nick
>
| |
| daestrom 2006-07-31, 5:25 pm |
|
"Jeff" <dont_bug_me@all.uk> wrote in message
news:1anzg.450$xp2.155@newsread1.news.pas.earthlink.net...
> nicksanspam@ece.villanova.edu wrote:
<snip>
>
>
> From The Passive Solar Energy Handbook, Edward Mazria 1979 we have this in
> Appendix E.6 Resistance values of airspaces
>
> Horizontal, Heatflow Down
> NR=Non Reflective
>
> Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
> 3/4 W 1.02 2.39 3.55
> 1 1/2 W 1.14 3.21 5.74
> 4 W 1.23 4.02 8.94
> 3/4 S 0.84 2.08 3.25
> 1 1/2 S 0.93 2.76 5.24
> 4 S 0.99 3.38 8.03
>
>
> Obviously that's all from observations.
>
> What strikes me for my application at hand, insulating under staple up
> radiant, is that 8.94 for a single radiant barrier. It sure makes foil
> double bubble look good.
>
One thing though about radiant barriers. It's well settled that the upper
surface of horizontal installations will not retain its low emissivity.
Unless you fancy wiping and cleaning off the dust every year or so, it will
accumulate and lose its effectiveness.
In attics, it's advised to put the radiant barrier on the rafters overhead
so the radiant surface is on the underside. For underfloor installations,
the same thing. The foil goes on the underside to limit the accumulation of
dust that will ruin its effectiveness.
daestrom
| |
| Solar Flare 2006-07-31, 5:25 pm |
| http://www.naturalspacesdomes.com/l...testresults.htm
"Jeff" <dont_bug_me@all.uk> wrote in message
news:1anzg.450$xp2.155@newsread1.news.pas.earthlink.net...[color=darkred]
> nicksanspam@ece.villanova.edu wrote:
>
>
> From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
> this in Appendix E.6 Resistance values of airspaces
>
> Horizontal, Heatflow Down
> NR=Non Reflective
>
> Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
> 3/4 W 1.02 2.39 3.55
> 1 1/2 W 1.14 3.21 5.74
> 4 W 1.23 4.02 8.94
> 3/4 S 0.84 2.08 3.25
> 1 1/2 S 0.93 2.76 5.24
> 4 S 0.99 3.38 8.03
>
>
> Obviously that's all from observations.
>
> What strikes me for my application at hand, insulating under staple
> up radiant, is that 8.94 for a single radiant barrier. It sure makes
> foil double bubble look good.
>
> Jeff
>
| |
| Solar Flare 2006-07-31, 5:25 pm |
| Isn't the reflective surface only effective if there is an air gap
next to it?
I have read some testing reports that show those 3/8" doubvle radiant
barriers under slabs to have a non-measureable difference to no
insultaion at all. Pissed off my concrete guy but I gave him a print
out of the report and now I can't find it again.
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:6evzg.8991$uH6.5268@twister.nyroc.rr.com...
>
> "Jeff" <dont_bug_me@all.uk> wrote in message
> news:1anzg.450$xp2.155@newsread1.news.pas.earthlink.net...
> <snip>
>
> One thing though about radiant barriers. It's well settled that the
> upper surface of horizontal installations will not retain its low
> emissivity. Unless you fancy wiping and cleaning off the dust every
> year or so, it will accumulate and lose its effectiveness.
>
> In attics, it's advised to put the radiant barrier on the rafters
> overhead so the radiant surface is on the underside. For underfloor
> installations, the same thing. The foil goes on the underside to
> limit the accumulation of dust that will ruin its effectiveness.
>
> daestrom
>
| |
| daestrom 2006-07-31, 8:25 pm |
|
"Solar Flare" <solerfart@hotomali.invalidated> wrote in message
news:gISdnaY-7JiLHFPZnZ2dnUVZ_rOdnZ2d@golden.net...
> Isn't the reflective surface only effective if there is an air gap next to
> it?
>
That's my understanding. It reduces the amount of heat transferred across
the air-gap by radiant heat transfer.
Since convection is the larger heat transfer mechanism for heat flow upward
(such as in an attic in a cold climate), they are not as effective when
trying to stop heat loss. So you usually only see them touted in situations
to stop the heat flow downward. Such as a hot attic to an air-conditioned
space, or from a heated room downward to an unheated crawl-space/cellar.
> I have read some testing reports that show those 3/8" doubvle radiant
> barriers under slabs to have a non-measureable difference to no insultaion
> at all. Pissed off my concrete guy but I gave him a print out of the
> report and now I can't find it again.
>
Yeah, putting some other material in direct contact with the foil, such as a
layer of wallboard, or a concrete floor pretty much nullifies the affects of
the foil. Of course, if the foil is over one inch of foam board, you still
have the one inch of foam and its insulation value. But not worth paying
any extra to get the foil.
daestrom
| |
| Solar Flare 2006-07-31, 8:25 pm |
| Do you know what the defined RSI rating means? I have heard so many
definitions that none of them make sense anymore. Many try to equate
it with the R factor unsuccessfully and I believe it has something to
do with "reflective..."
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:QBvzg.8994$uH6.3775@twister.nyroc.rr.com...
>
> "Solar Flare" <solerfart@hotomali.invalidated> wrote in message
> news:gISdnaY-7JiLHFPZnZ2dnUVZ_rOdnZ2d@golden.net...
>
> That's my understanding. It reduces the amount of heat transferred
> across the air-gap by radiant heat transfer.
>
> Since convection is the larger heat transfer mechanism for heat flow
> upward (such as in an attic in a cold climate), they are not as
> effective when trying to stop heat loss. So you usually only see
> them touted in situations to stop the heat flow downward. Such as a
> hot attic to an air-conditioned space, or from a heated room
> downward to an unheated crawl-space/cellar.
>
>
> Yeah, putting some other material in direct contact with the foil,
> such as a layer of wallboard, or a concrete floor pretty much
> nullifies the affects of the foil. Of course, if the foil is over
> one inch of foam board, you still have the one inch of foam and its
> insulation value. But not worth paying any extra to get the foil.
>
> daestrom
>
| |
|
| daestrom wrote:
>
> "Jeff" <dont_bug_me@all.uk> wrote in message
> news:1anzg.450$xp2.155@newsread1.news.pas.earthlink.net...
>
>
> <snip>
>
>
> One thing though about radiant barriers. It's well settled that the
> upper surface of horizontal installations will not retain its low
> emissivity. Unless you fancy wiping and cleaning off the dust every year
> or so, it will accumulate and lose its effectiveness.
Well that puts an interesting spin on my underfloor, staple up, unheated
basement app.
It looks to me that I have two ways to go:
1) 3 1/2" (R 11 + R 6 or so for the radiant) fiberglass batts with a
radiant barrier wired up with wire hangers or
something similar. An airspace of an 1 1/2" or so.
2) double bubble (triple radiant)
I think the radiant barrier is essential due to the higher temp of the
radiant to ambient.
Originally I had only thought of method 1.
But radiant barrier batts are hard to find. Adding a radiant barrier
to an existing is awkward.
So method two, which is what at least some staple up suppliers
provide, seems plausible. It would be easier to dust seal this and it
certainly would be easier to install.
Have I missed something, or is this really the best app for radiant
bubble? Perhaps the only time it should be used.
Jeff
>
> In attics, it's advised to put the radiant barrier on the rafters
> overhead so the radiant surface is on the underside. For underfloor
> installations, the same thing. The foil goes on the underside to limit
> the accumulation of dust that will ruin its effectiveness.
>
> daestrom
>
| |
| nicksanspam@ece.villanova.edu 2006-08-01, 3:25 am |
| Jeff <dont_bug_me@all.uk> wrote:
>daestrom wrote:
With how many foils and what temp? What's the significance of "W" and "S"
with downward heatflow? A winter floor and a summer ceiling?
[color=darkred]
So up-facing foils may not help much, unless they are well-sealed above.
[color=darkred]
>It looks to me that I have two ways to go:
>
>1) 3 1/2" (R 11 + R 6 or so for the radiant) fiberglass batts with a
>radiant barrier wired up with wire hangers or
>something similar. An airspace of an 1 1/2" or so.
>2) double bubble (triple radiant)
It seems that Reflectix makes a product with no radiant effect for use
under concrete, and another with 2 foils (not "triple radiant") on the
outside. The inner layers have no foil. Other options are double-foil
polyiso board and double-sided "builders foil" in 4' rolls at 10-20
cents/ft^2 from companies like Innovative Insulation, and more costly
adhesive-backed foil, and OSB with one foil face, which might be found
on the underside of a roof.
>... method two, which is what at least some staple up suppliers
>provide, seems plausible. It would be easier to dust seal this and it
>certainly would be easier to install.
Dust sealing the exposed upper foil would be difficult.
> Have I missed something, or is this really the best app for radiant
>bubble? Perhaps the only time it should be used.
Radiant barriers are good for downward heatflow (including a fridge roof),
OK for horizontal heatflow, and poorish for upward heatflow.
Nick
| |
|
|
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:6evzg.8991$uH6.5268@twister.nyroc.rr.com...
>
> "Jeff" <dont_bug_me@all.uk> wrote in message
> news:1anzg.450$xp2.155@newsread1.news.pas.earthlink.net...
> <snip>
>
> One thing though about radiant barriers. It's well settled that the upper
> surface of horizontal installations will not retain its low emissivity.
> Unless you fancy wiping and cleaning off the dust every year or so, it
> will accumulate and lose its effectiveness.
>
> In attics, it's advised to put the radiant barrier on the rafters overhead
> so the radiant surface is on the underside. For underfloor installations,
> the same thing. The foil goes on the underside to limit the accumulation
> of dust that will ruin its effectiveness.
I always thought the shiny side reflects, so needs to be facing where heat
needs to be reflected back and there needs to be a 1" gap between that and
any other surface. Having it under floors facing down should not be
effective. Yet I have read that some makers say it does not matter which way
it goes, I find that hard to believe.
| |
|
|
<nicksanspam@ece.villanova.edu> wrote in message
news:ean0fv$i9l@acadia.ece.villanova.edu...
> Jeff <dont_bug_me@all.uk> wrote:
>
> With how many foils and what temp? What's the significance of "W" and "S"
> with downward heatflow? A winter floor and a summer ceiling?
>
>
> So up-facing foils may not help much, unless they are well-sealed above.
>
>
> It seems that Reflectix makes a product with no radiant effect for use
> under concrete, and another with 2 foils (not "triple radiant") on the
> outside. The inner layers have no foil. Other options are double-foil
> polyiso board and double-sided "builders foil" in 4' rolls at 10-20
> cents/ft^2 from companies like Innovative Insulation, and more costly
> adhesive-backed foil, and OSB with one foil face, which might be found
> on the underside of a roof.
>
>
> Dust sealing the exposed upper foil would be difficult.
>
>
> Radiant barriers are good for downward heatflow (including a fridge roof),
> OK for horizontal heatflow, and poorish for upward heatflow.
In keeping heat ina house, fine for the walls, no good in the attic.
| |
| nicksanspam@ece.villanova.edu 2006-08-01, 5:25 pm |
| News <Nospam@here.com> wrote:
>I always thought the shiny side reflects, so needs to be facing where heat
>needs to be reflected back
When heat radiation strikes a surface, it's either transmitted, absorbed,
or reflected. Kirchoff said "It has to go somewhere," ie T + A + R = 1. If
T = 0 (an opaque surface with no transmission), A + R = 1. If the surface
emits as much power as it absorbs, E = A, integrated over the whole spectrum
(R is an energy conservation wash.) So a foil has reflectivity 1-E, which
is large if E is small, ie it's a good heat mirror. It can stay cool because
it doesn't absorb much heat, and it won't lose much heat because it's at
a low temp and it emits poorly.
>and there needs to be a 1" gap between that and any other surface.
Big gaps with less still-air conductance are good for downwards heatflow.
A 1-1.5" gap is good for sideways heatflow. Smaller gaps have more still-air
conductance and larger gaps have slightly more "convection conductance."
>Having it under floors facing down should not be effective.
It should be, if there's an air gap beneath the foil.
Nick
| |
| Robert Gammon 2006-08-01, 5:25 pm |
| News wrote:
>
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
> news:6evzg.8991$uH6.5268@twister.nyroc.rr.com...
>
> I always thought the shiny side reflects, so needs to be facing where
> heat needs to be reflected back and there needs to be a 1" gap between
> that and any other surface. Having it under floors facing down should
> not be effective. Yet I have read that some makers say it does not
> matter which way it goes, I find that hard to believe.
>
>
We're talking about the FOIL side. Its going to be shiny regardless.
With a crawl space underneath, IT MAKES LOADS of sense. But the
direction it faces is CLIMATE dependent. Cold climates, foil side
faces towards the house to radiate heat back to the floors. Hot
climates, it faces down to reflect back heat from the crawl space.
Foil, insulation, paper, or foil insulation foil are available
In new construction, you can get foam boards for sheathing that have the
radiant barrier foil attached, in some cases to BOTH sides.
www.atlasroofing.com for an example of such. A 2" board will add about
$1.15 sq ft to materials cost of the house and adds R12 to the walls.
Similar boards are available for roofs, in areas that will see water
freeze on the roof.
| |
|
| News wrote:
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:ean0fv$i9l@acadia.ece.villanova.edu...
>
>
>
> In keeping heat ina house, fine for the walls, no good in the attic.
I disagree, but I'm willing to listen to your reasoning if you care to
present it.
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
| |
| nicksanspam@ece.villanova.edu 2006-08-01, 5:25 pm |
| Robert Gammon <rgammon51@yahoo.com> wrote:
>... Cold climates, foil side faces towards the house to radiate heat
>back to the floors.
Wrong again.
Nick
| |
|
| News wrote:
<snip>
> I always thought the shiny side reflects, so needs to be facing where
> heat needs to be reflected back and there needs to be a 1" gap between
> that and any other surface. Having it under floors facing down should
> not be effective. Yet I have read that some makers say it does not
> matter which way it goes, I find that hard to believe.
>
>
Then you need to develop an understanding of emmissivity.
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
| |
|
|
"CJT" <abujlehc@prodigy.net> wrote in message
news:44CFC75D.9000504@prodigy.net...
> News wrote:
>
>
> I disagree, but I'm willing to listen to your reasoning if you care to
> present it.
I was just bottom lining what Nick was saying just above.
| |
|
|
"CJT" <abujlehc@prodigy.net> wrote in message
news:44CFEF05.60409@prodigy.net...
> News wrote:
>
> <snip>
>
> Then you need to develop an understanding of emmissivity.
I'm sure Nick will elaborate on the wheres and whys of which way it faces
for optimum performance - which is now the latest confused point on
barriers.
| |
|
| News wrote:
>
> "CJT" <abujlehc@prodigy.net> wrote in message
> news:44CFEF05.60409@prodigy.net...
>
>
>
> I'm sure Nick will elaborate on the wheres and whys of which way it
> faces for optimum performance - which is now the latest confused point
> on barriers.
>
>
There should be no confusion.
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
| |
|
|
"CJT" <abujlehc@prodigy.net> wrote in message
news:44CFFC0A.9010805@prodigy.net...
> News wrote:
>
[color=darkred]
> There should be no confusion.
"Should" and "is" are two different things ;-)
| |
| daestrom 2006-08-02, 5:25 pm |
|
"CJT" <abujlehc@prodigy.net> wrote in message
news:44CFC75D.9000504@prodigy.net...
> News wrote:
>
<snip>[color=darkred]
<snip>
[color=darkred]
>
> I disagree, but I'm willing to listen to your reasoning if you care to
> present it.
>
As I said before. Government and independent testing has shown that radiant
barriers lose much of their effectiveness if they get a layer of dust over
the foil side of them. The dust raises the emissivity to that of other
non-metallic materials ( > 0.85).
In places like attics, the 'usual' installation of radiant barriers is not
across the floor, but attached to the rafters overhead, facing downward.
This avoids the dust buildup issue. Thus the radiant surface is 'aimed'
downwards to the floor space of the attic. In climates that need a lot of
A/C, this can work quite well. The solar heat gained by the roofing heats
the sheathing and rafters, but the radiant barrier prevents it from
radiating to the attic floor (ceiling of the living space). Testing for
their efficacy in such installations has gone well. Radiant barriers in
this sort of situation can be an inexpensive, easy to install way to reduce
cooling energy needs.
Sadly, for climates needing a lot of heating, the situation doesn't work so
well. Installing the radiant barrier on the rafters does little to reduce
heat loss from the attic floor (living space ceiling). One reason for this
is that attics in cold climates are deliberately ventilated to keep the
attic cool. This prevents ice damage and ice dam formation on the eaves.
Another reason for poor performance in heating climates is that with the
heat flow upwards, natural convection of air from the attic floor to the
radiant barrier far outweighs the radiant heat transfer component, so
reducing the radiant heat transfer does little to reduce the overall heat
transfer (most upward heat flow still happens from convection currents).
So, bottom line. If the direction of heat flow is upward, radiant barriers
don't work well. Either convection outweighs the radiant component, or the
surface gets contaminated with dust and requires cleaning, or both.
For downward heat flow, they can add to the overall insulation if installed
correctly.
daestrom
| |
| daestrom 2006-08-02, 5:25 pm |
|
"News" <Nospam@here.com> wrote in message
news:44cf39c0$0$17985$892e7fe2@authen.yellow.readfreenews.net...
>
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
> news:6evzg.8991$uH6.5268@twister.nyroc.rr.com...
<snip>[color=darkred]
>
> I always thought the shiny side reflects, so needs to be facing where heat
> needs to be reflected back and there needs to be a 1" gap between that and
> any other surface. Having it under floors facing down should not be
> effective. Yet I have read that some makers say it does not matter which
> way it goes, I find that hard to believe.
>
Let me see if I can clarify it a bit for you.
Radiant heat transfer involves two surfaces. The 'hotter' one radiants
infrared energy, the 'cooler' one absorbs it. How well a particular surface
emits infrared energy when heated is measured by its emissivity.
So to reduce radiant heat transfer, we can coat the cold surface with
something that reflects infrared energy so it doesn't absorb as much. -OR-,
we could coat the hot surface with something that doesn't radiate/emit
infrared energy as well. Either one will reduce the amount of infrared
energy that gets from the 'hot' surface to the cold surface.
Now, it just so happens, that with very few exceptions, surfaces that are
poor at absorbing infrared are poor at emitting infrared. And surfaces that
are good at emitting infrared are also good at absorbing infrared. Polished
metal and metal foils are very poor at absorbing and emitting infrared. So
radiant barriers have a metalized/foil surface. There emissivity is quite
low (< 0.2, some as low as 0.05). Non metalic materials (wood, plaster,
glass wool, etc...) are good absorbers/emitters (emissivity > 0.8, often
>0.9).
So, in the case of under-floor radiant barriers, if we cover the 'hot'
surface with a material that is a poor absorber of infrared (and hence is a
poor emitter of infrared), we get about the same overall affect as if we had
covered the 'cold' surface with it. We could cover either one and get about
the same affect, at least in the short term.
But once the poor absorber/emitter is covered with dust, the heat can travel
from the foil to the dust by conduction (a very good transfer mechanism).
And household dust has a very high emissivity, so it absorbs/emitts infrared
quite well. So the dust layer completely circumvents any savings of the
radiant barrier. So we *really* want to keep the radiant barrier clean.
And by putting the poor absorber/emitter on the underside, we have it in a
position (facing downward) where dust and dirt are less likely to settle on
it.
daestrom
| |
| daestrom 2006-08-02, 5:25 pm |
|
"Robert Gammon" <rgammon51@yahoo.com> wrote in message
news:IaPzg.3476$uo6.2759@newssvr13.news.prodigy.com...
> News wrote:
<snip>[color=darkred]
> We're talking about the FOIL side. Its going to be shiny regardless.
>
> With a crawl space underneath, IT MAKES LOADS of sense. But the
> direction it faces is CLIMATE dependent. Cold climates, foil side faces
> towards the house to radiate heat back to the floors. Hot climates, it
> faces down to reflect back heat from the crawl space.
>
> Foil, insulation, paper, or foil insulation foil are available
>
> In new construction, you can get foam boards for sheathing that have the
> radiant barrier foil attached, in some cases to BOTH sides.
> www.atlasroofing.com for an example of such. A 2" board will add about
> $1.15 sq ft to materials cost of the house and adds R12 to the walls.
> Similar boards are available for roofs, in areas that will see water
> freeze on the roof.
I think you're confusing the placement of the "vapor barrier" with the
placement of a "radiant barrier".
In construction, it is best to place the *vapor* barrier on the 'warm side'.
So in heating climates, the vapor barrier is place on the inside and in
cooling climates on the outside. The logic behind this is you want to block
the moisture that seeps through the wall *before* it cools down and has a
chance to condense.
But the foil of a *radiant* barrier can be on either the hot or cold surface
and the difference is not very much. The most important part about radiant
barriers is that a) they be positioned/installed so the foil remains clean,
b) the have an air gap facing the foil (direct contact with the next layer
makes the foil useless), c) they are only effective if air convection
against their surface is not an issue.
A 2" thick foam board with *no* radiant foil will add about R12 to the
walls. If the foamboard has a closed-cell surface coating, it can double as
a vapor/draft barrier as well. Sandwiching a foil layer between other
materials with no air gap is a complete waste of money.
daestrom
| |
|
| daestrom wrote:
>
> "CJT" <abujlehc@prodigy.net> wrote in message
> news:44CFC75D.9000504@prodigy.net...
>
>
> <snip>
>
>
>
> <snip>
>
>
> As I said before. Government and independent testing has shown that
> radiant barriers lose much of their effectiveness if they get a layer of
> dust over the foil side of them. The dust raises the emissivity to that
> of other non-metallic materials ( > 0.85).
>
> In places like attics, the 'usual' installation of radiant barriers is
> not across the floor, but attached to the rafters overhead, facing
> downward. This avoids the dust buildup issue. Thus the radiant surface
> is 'aimed' downwards to the floor space of the attic. In climates that
> need a lot of A/C, this can work quite well. The solar heat gained by
> the roofing heats the sheathing and rafters, but the radiant barrier
> prevents it from radiating to the attic floor (ceiling of the living
> space). Testing for their efficacy in such installations has gone
> well. Radiant barriers in this sort of situation can be an inexpensive,
> easy to install way to reduce cooling energy needs.
I was disagreeing with "no good in the attic," and you seem to agree
with me, at least in climates where AC costs predominate (like where
I am -- Texas).
I thought the focus was on AC, it being summer and all, but you may
have a point in a broader context.
>
> Sadly, for climates needing a lot of heating, the situation doesn't work
> so well. Installing the radiant barrier on the rafters does little to
> reduce heat loss from the attic floor (living space ceiling). One
> reason for this is that attics in cold climates are deliberately
> ventilated to keep the attic cool. This prevents ice damage and ice dam
> formation on the eaves. Another reason for poor performance in heating
> climates is that with the heat flow upwards, natural convection of air
> from the attic floor to the radiant barrier far outweighs the radiant
> heat transfer component, so reducing the radiant heat transfer does
> little to reduce the overall heat transfer (most upward heat flow still
> happens from convection currents).
>
> So, bottom line. If the direction of heat flow is upward, radiant
> barriers don't work well. Either convection outweighs the radiant
> component, or the surface gets contaminated with dust and requires
> cleaning, or both.
>
> For downward heat flow, they can add to the overall insulation if
> installed correctly.
>
> daestrom
>
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
| |
| Robert Gammon 2006-08-03, 9:25 am |
| daestrom wrote:
>
> "Robert Gammon" <rgammon51@yahoo.com> wrote in message
> news:IaPzg.3476$uo6.2759@newssvr13.news.prodigy.com...
> <snip>
>
> I think you're confusing the placement of the "vapor barrier" with the
> placement of a "radiant barrier".
>
> In construction, it is best to place the *vapor* barrier on the 'warm
> side'. So in heating climates, the vapor barrier is place on the
> inside and in cooling climates on the outside. The logic behind this
> is you want to block the moisture that seeps through the wall *before*
> it cools down and has a chance to condense.
>
> But the foil of a *radiant* barrier can be on either the hot or cold
> surface and the difference is not very much. The most important part
> about radiant barriers is that a) they be positioned/installed so the
> foil remains clean, b) the have an air gap facing the foil (direct
> contact with the next layer makes the foil useless), c) they are only
> effective if air convection against their surface is not an issue.
>
> A 2" thick foam board with *no* radiant foil will add about R12 to the
> walls. If the foamboard has a closed-cell surface coating, it can
> double as a vapor/draft barrier as well. Sandwiching a foil layer
> between other materials with no air gap is a complete waste of money.
>
>
A 2" thick foam board with a radiant barrier applied to the board with
the board sitting behind a brick or concrete block wall has the required
airspace in front of the radiant barrier. If HardiPlank or HardiPanel
siding products or stucco are applied over the foam board, then paying
for a radiant barrier is nonsense.
You assume that the cladding is applied directly to the foam board. Not
always true.
| |
|
| daestrom wrote:
>
> "News" <Nospam@here.com> wrote in message
> news:44cf39c0$0$17985$892e7fe2@authen.yellow.readfreenews.net...
>
> <snip>
>
>
> Let me see if I can clarify it a bit for you.
>
> Radiant heat transfer involves two surfaces. The 'hotter' one radiants
> infrared energy, the 'cooler' one absorbs it. How well a particular
> surface emits infrared energy when heated is measured by its emissivity.
>
> So to reduce radiant heat transfer, we can coat the cold surface with
> something that reflects infrared energy so it doesn't absorb as much.
> -OR-, we could coat the hot surface with something that doesn't
> radiate/emit infrared energy as well. Either one will reduce the amount
> of infrared energy that gets from the 'hot' surface to the cold surface.
>
> Now, it just so happens, that with very few exceptions, surfaces that
> are poor at absorbing infrared are poor at emitting infrared. And
> surfaces that are good at emitting infrared are also good at absorbing
> infrared. Polished metal and metal foils are very poor at absorbing and
> emitting infrared. So radiant barriers have a metalized/foil surface.
> There emissivity is quite low (< 0.2, some as low as 0.05). Non metalic
> materials (wood, plaster, glass wool, etc...) are good
> absorbers/emitters (emissivity > 0.8, often >0.9).
>
> So, in the case of under-floor radiant barriers, if we cover the 'hot'
> surface with a material that is a poor absorber of infrared (and hence
> is a poor emitter of infrared), we get about the same overall affect as
> if we had covered the 'cold' surface with it. We could cover either one
> and get about the same affect, at least in the short term.
I've been think about that as far as my staple up radiant goes. It
looks to me that I want to cover most of the area (perhaps all) between
joists with flashing thickness aluminum to spread the heat out. That's a
lower operating temperature for the working surface. I don't think the
emissivity is as low as foil, but probably around .08. It seems to me
that part of the joist should also be covered in a radiant barrier.
It looks like you can gain a good bit of insulation value just from
having a dead air space with an IR opaque boundary.
I see from my "Passive Solar Energy Book" That a horizontal foil
surface with heatflow down has an R value of 4.55. That would seem to
imply face nailing 1" polyiso foil covered, with the foil facing down
onto the joists. Perhaps R17 total. Does that sound about right?
Jeff
>
> But once the poor absorber/emitter is covered with dust, the heat can
> travel from the foil to the dust by conduction (a very good transfer
> mechanism). And household dust has a very high emissivity, so it
> absorbs/emitts infrared quite well. So the dust layer completely
> circumvents any savings of the radiant barrier. So we *really* want to
> keep the radiant barrier clean.
>
> And by putting the poor absorber/emitter on the underside, we have it in
> a position (facing downward) where dust and dirt are less likely to
> settle on it.
>
> daestrom
>
| |
|
|
"News" <Nospam@here.com> wrote in message
news:44cb0d86$0$17949$892e7fe2@authen.yellow.readfreenews.net...
>
> "News" <Nospam@here.com> wrote in message
> news:44ca5155$0$17961$892e7fe2@authen.yellow.readfreenews.net...
>
> The link above does not work. Here is the ruling:
>
> Actis Insulation Ltd
> Unit 1
> Cornbrash Park
> Bumpers Farm Industrial Estate
> Chippenham
> Wiltshire
> SN14 6RA
>
> Date: 31st May 2006
> Media: Brochure
>
> Sector: Household
>
> Public Complaint From: Gloucestershire
>
> Complaint:
>
> Objection to a brochure for roof insulation. The brochure stated "TRI-ISO
> SUPER 9 Insulation for roofs ... Thermally equivalent to 200 mm of mineral
> wool when installed in a roof situation, as certified by the European
> certifying body, BM TRADA CERTIFICATION (following real building trials,
> certification n°0101) ... THERMAL EFFICIENCY equivalent to 200 mm of
> mineral wood RT = 5* ... *in situ measured values." The complainant
> challenged:
>
> 1. the claim "Thermally equivalent to 200 mm of mineral wool" and
>
> 2. the quoted thermal resistance "RT = 5".
>
>
> Codes Section: 3.1, 7.1 (Ed 11)
>
> Adjudication:
>
> Actis Insulation Ltd (Actis) said they had stopped advertising TRI-ISO
> SUPER 9 because it had been replaced with their new product TRI-ISO SUPER
> 10. They said the efficiency of their products was demonstrated by their
> track record in the market. Actis said they had commissioned BM TRADA
> Certification Ltd (BM TRADA) to test, assess and report on the TRI-ISO
> Super 9 product. They provided us with a copy of the BM TRADA
> Certification and Report dated August 1997 and said that it substantiated
> their claims. Actis explained that TRI-ISO Super 9 was different from
> traditional bulk insulation because it was a multi-foil product that used
> layers of reflective foils spaced with synthetic wadding and foams. They
> said the product required less space than traditional bulk insulation and,
> therefore, internal insulation cavities could be made smaller and internal
> useable spaces could be enlarged without compromising efficiency of
> insulation. Actis argued that traditional methods of testing were not
> appropriate for their product because traditional methods measured thermal
> efficiency mainly by conduction and did not take into account the
> influences of convection, radiation and change of phase. They said their
> product combined various energy transfers of radiation, conduction,
> convection and change of state rather than just conduction. Actis also
> argued that traditional methods of testing did not allow representation of
> the real behaviour of building materials once used on site. They pointed
> out that BM TRADA had used "in situ" testing involving a real external
> environment with variations in temperature, humidity, etc. rather than the
> traditional methods of laboratory testing. Actis maintained that the BM
> TRADA Certification demonstrated the thermal efficiency of their product
> and provided proof of their claims.
>
> 1. Complaint upheld
>
> The ASA obtained expert advice. We understood that BM TRADA had tested
> TRI-ISO SUPER 9 and the mineral wool in two separate roof installations.
> However, we noted that BM TRADA had not used the standard industry methods
> of testing and that the report provided by Actis did not include
> sufficient detail to support their own methods of testing.
>
> We acknowledged that BM TRADA Certification was a leading multi-sector
> certification body accredited by the United Kingdom Accreditation Service.
> We considered that the BM TRADA report did not provide enough detail to
> support their methodology instead of the methodology employed by the
> internationally recognised ISO industry standards. We concluded Actis had
> not substantiated the claim. We noted the ad was no longer appearing but
> told Actis not to repeat the claim in future advertising until they were
> able to provide sufficient substantiation.
>
> 2. Complaint upheld
>
> We understood that RT was a symbol of total thermal resistance and
> typically had the standard unit of measurement of mēK/W. We noted that the
> claim "RT=5" was not qualified by any recognised units of measurement e.g.
> mēK/W and a small footnote stated only "in situ measured values" without
> further explanation. Because the value of 5 was not qualified by any
> recognised units of measurement, we considered the claim "RT=5" was
> ambiguous and should be qualified in future. However, we noted that the BM
> TRADA report did specify an overall resistance (RT) of 5.0mēK/W derived
> from the in situ testing. We understood that the in situ measured values
> did not meet with ISO recognised international standards for determining
> declared and design thermal values for building materials and products.
>
> We considered that the BM TRADA report did not include sufficient detail
> to demonstrate the validity or robustness of their testing methodology
> instead of the methodology employed by ISO standards. We concluded that
> the report did not substantiate the claim " RT=5". We told Actis to remove
> the claim until they were able to provide sufficient substantiation.
>
> The brochure breached CAP Code clauses 3.1 (Substantiation) and 7.1
> (Truthfulness).
Further to the above:
The UK authorities have pulled the plug on multifoils, when used on their
own. The Multifoil Council) made pleaded to the Office of the Deputy Prime
Minister when the last round of Part L (energy aspect) of the building regs
was being assessed and had a reprieve to 01/01/2007 to give them time to
show that multifoils worked as claimed. This repreive has been recinded
early because of convincing evidence
that the multifoil claims are exagerated. Multifoils will only be
permissable if they can pass hot box tests, which they have never have. All
the local authorities and the NHBC and such bodies have all been told to no
longer accept multifoils.
Action may be taken against the 3rd party certifiers, principally BM Trada,
who gave their stamp of approval to Actis and others.
|
|
|
|
|