Posted by limehand on February 22, 2011, 12:48 am
corrected address
> > I am just not impressed with a plastic product that is
> > going to be installed at the hottest part of the house.
> > Unless there is a nonprorated guarantee of at least
> > 20 years, for a company that will still be around to
> > honor it.
> > And able to be installed without special instructions,
> > and the payback period...well, you get the idea.
> > I'm simply not impressed.
> > A ridge vent, with suitable soffit venting is IMO the way
> > to go.
> > And a reminder. If you don't have a minimum of one
> > square foot of vent per 300 feet of vented space, you
> > likely have no guarantee on your shingles. And for the
> > sake of comfort, it should be per 150 feet or better.
> > regardless of what else you put in your attic, the paperwork
> > for the shingles calls for VENTING. Any questions, I suggest
> > calling the Owens-Corning folks at 1-800-ROOFING
> > > > On 2/9/2011 1:28 PM, Bob F wrote:
> > > > > W wrote:
> > > > >> There is an outfit in the San Francisco Bay Area named Eagleshield
> > > > >> that pushes the use of a reflective liner on the inside of the roof,
> > > > >> to reflect away solar heat during summer. Is anyone familiar with
> > > > >> this kind of product and how well does it work?
> > > > > If you live in a hot area, this will boost your roofing temp
> > > significantly,
> > > > > decreasing its life, unless there is very good venting above the
> > > reflector.
> > > > Do you have any real evidence of that? I put a radiant barrier under
> > > > half of my roof and then compared temperatures on the two halves with an
> > > > infrared thermometer, being careful to measure at the same time, under
> > > > full sunlight and at the same angle; I found no measurable difference in
> > > > temperature. I do know, however, that my A/C costs dropped considerably
> > > > when I installed the radiant barrier.
> > > How did you do the installation? Did you have any kind of soffit vent, or
> > > did you mount the radiant barrier across the roof supports so as to allow an
> > > air channel between the radiant barrier and the roof?
> > > Did you mount it only on the south facing part of house? Why did you do
> > > just half the roof?
> > > Which vendor and brand of reflective material did you use? Was there any
> > > reason to prefer one brand over another?
> > > Not being familiar with radiant barriers, are they reflective on both sides?
> > > Doesn't dust accumulation lower their effectiveness at some point?
> > > What kind of reduction did you see in AC usage?
> > > --
> > > W
> There seems to be a number of different suppositions at work here.
> The assumption that attic venting is necessary denies the fact that
> cathedral ceilinged rooms or spaces dont have ridge vents or vents for
> obvious reasons, heat loss. The need for asphalt shingles to be cooled
> from below is I believe unable to be substantiated through documented
> side by side testing. Metal roofing far superior to asphalt roofing
> would be a better choice anyway as a shiny silver steel roof will
> reflect infrared eat as silver reflective surfaces do.(If there is any
> doubt about this get a sheet of aluminum foil from the kitchen and
> hold a lighter to the underside (not directly as this would be
> conductance NOT radiation) and check the heat pass through with your
> hand.)
> There is some debate though about the need for heat over the need to
> reflect it. It depends on where you are I expect or if you have a
> ridge water tank you wish to heat up to save money producing hot water
> for your hydronic heating system. If the attic is living space
> accessed by permanent stairs then any heat build up could be vented
> with gable end windows.
> Conversely if a building has a crawl space then stapling reflective
> foil on the underside of the floor joists will save some heat from
> being radiated downward to the cold earth below.This is of course
> usually tricky to do and will in time become less effective due to
> dust etc settling down on it But it does work quite well if the floor
> can be sealed above.
> regards
> Michael Lough
Posted by W on February 22, 2011, 8:55 am
> I am just not impressed with a plastic product that is
> going to be installed at the hottest part of the house.
> Unless there is a nonprorated guarantee of at least
> 20 years, for a company that will still be around to
> honor it.
> And able to be installed without special instructions,
> and the payback period...well, you get the idea.
> I'm simply not impressed.
> A ridge vent, with suitable soffit venting is IMO the way
> to go.
> And a reminder. If you don't have a minimum of one
> square foot of vent per 300 feet of vented space, you
> likely have no guarantee on your shingles. And for the
> sake of comfort, it should be per 150 feet or better.
> regardless of what else you put in your attic, the paperwork
> for the shingles calls for VENTING. Any questions, I suggest
> calling the Owens-Corning folks at 1-800-ROOFING
> > > On 2/9/2011 1:28 PM, Bob F wrote:
> > > > W wrote:
> > > >> There is an outfit in the San Francisco Bay Area named Eagleshield
> > > >> that pushes the use of a reflective liner on the inside of the
> > > >> roof,
> > > >> to reflect away solar heat during summer. Is anyone familiar with
> > > >> this kind of product and how well does it work?
> > > > If you live in a hot area, this will boost your roofing temp
> > significantly,
> > > > decreasing its life, unless there is very good venting above the
> > reflector.
> > > Do you have any real evidence of that? I put a radiant barrier under
> > > half of my roof and then compared temperatures on the two halves with
> > > an
> > > infrared thermometer, being careful to measure at the same time, under
> > > full sunlight and at the same angle; I found no measurable difference
> > > in
> > > temperature. I do know, however, that my A/C costs dropped
> > > considerably
> > > when I installed the radiant barrier.
> > How did you do the installation? Did you have any kind of soffit vent,
> > or
> > did you mount the radiant barrier across the roof supports so as to
> > allow an
> > air channel between the radiant barrier and the roof?
> > Did you mount it only on the south facing part of house? Why did you do
> > just half the roof?
> > Which vendor and brand of reflective material did you use? Was there any
> > reason to prefer one brand over another?
> > Not being familiar with radiant barriers, are they reflective on both
> > sides?
> > Doesn't dust accumulation lower their effectiveness at some point?
> > What kind of reduction did you see in AC usage?
> > --
> > W
>There seems to be a number of different suppositions at work here.
>The assumption that attic venting is necessary denies the fact that
>cathedral ceilinged rooms or spaces dont have ridge vents or vents for
>obvious reasons, heat loss. The need for asphalt shingles to be cooled
>from below is I believe unable to be substantiated through documented
>side by side testing. Metal roofing far superior to asphalt roofing
>would be a better choice anyway as a shiny silver steel roof will
>reflect infrared eat as silver reflective surfaces do.(If there is any
>doubt about this get a sheet of aluminum foil from the kitchen and
>hold a lighter to the underside (not directly as this would be
>conductance NOT radiation) and check the heat pass through with your
>hand.)
>There is some debate though about the need for heat over the need to
>reflect it. It depends on where you are I expect or if you have a
>ridge water tank you wish to heat up to save money producing hot water
>for your hydronic heating system. If the attic is living space
>accessed by permanent stairs then any heat build up could be vented
>with gable end windows.
>Conversely if a building has a crawl space then stapling reflective
>foil on the underside of the floor joists will save some heat from
>being radiated downward to the cold earth below.This is of course
>usually tricky to do and will in time become less effective due to
>dust etc settling down on it But it does work quite well if the floor
>can be sealed above.
The climate in question is California, with 90 to 100 degree days in Summer
and 40 to 55 degree typical Winter days.
During Summer, the attic space gets to be about 140 degrees. In a perfect
world, you would want to build in sufficient insulation between the attic
and the home. For the sake of argument, let's assume that this is either
not possible or isn't an easy solution.
The question is then can anything be done to significantly lower the attic
temperature during hot Summer days?
If you were installing a new roof, then probably there are products that
would reflect heat directly from the shingle, or would absorb less heat to
the shingle. Assume that purchasing a new roof is not an option here.
Assuming you did have a ridge vent, would a reflective liner attached inside
of the roof significantly lower the attic temperature during the Summer?
Regarding ridge vents, does anyone make a model that would allow the vent to
be open during Summer and closed during Winter? The home is also fed by
vents under the roof gutter, which would stay open year round.
--
W
Posted by vaughn on February 22, 2011, 7:19 pm
> Regarding ridge vents, does anyone make a model that would allow the vent to
> be open during Summer and closed during Winter? The home is also fed by
> vents under the roof gutter, which would stay open year round.
Would solar powered vent fans be an option?
Vaughn
Posted by W on February 22, 2011, 11:07 pm
> > Regarding ridge vents, does anyone make a model that would allow the
vent to
> > be open during Summer and closed during Winter? The home is also fed
by
> > vents under the roof gutter, which would stay open year round.
> Would solar powered vent fans be an option?
I tried a 1700 cpm electric fan, and that only lowered temperature about 10
degrees.
Total 2D dimension of attic area at base is about 2100 sq ft.
--
W
Posted by limehand on February 12, 2011, 6:08 pm
> There is an outfit in the San Francisco Bay Area named Eagleshield that
> pushes the use of a reflective liner on the inside of the roof, to reflect
> away solar heat during summer. Is anyone familiar with this kind of
> product and how well does it work?
> Are there strong differences in the quality of the material used for such
> reflective insulation, and what are the scales or criteria used to specify
> the highest efficacy material. I would be tempted to have a third party
> do the install but want to make sure I don't compromise on the material.
> --
> W
Hello I would like to add to this thread but have not posted on this
list before and think I should test it first sorry for any
inconvenience this might cause a reader
MKL
XML site map
> > going to be installed at the hottest part of the house.
> > Unless there is a nonprorated guarantee of at least
> > 20 years, for a company that will still be around to
> > honor it.
> > And able to be installed without special instructions,
> > and the payback period...well, you get the idea.
> > I'm simply not impressed.
> > A ridge vent, with suitable soffit venting is IMO the way
> > to go.
> > And a reminder. If you don't have a minimum of one
> > square foot of vent per 300 feet of vented space, you
> > likely have no guarantee on your shingles. And for the
> > sake of comfort, it should be per 150 feet or better.
> > regardless of what else you put in your attic, the paperwork
> > for the shingles calls for VENTING. Any questions, I suggest
> > calling the Owens-Corning folks at 1-800-ROOFING
> > > > On 2/9/2011 1:28 PM, Bob F wrote:
> > > > > W wrote:
> > > > >> There is an outfit in the San Francisco Bay Area named Eagleshield
> > > > >> that pushes the use of a reflective liner on the inside of the roof,
> > > > >> to reflect away solar heat during summer. Is anyone familiar with
> > > > >> this kind of product and how well does it work?
> > > > > If you live in a hot area, this will boost your roofing temp
> > > significantly,
> > > > > decreasing its life, unless there is very good venting above the
> > > reflector.
> > > > Do you have any real evidence of that? I put a radiant barrier under
> > > > half of my roof and then compared temperatures on the two halves with an
> > > > infrared thermometer, being careful to measure at the same time, under
> > > > full sunlight and at the same angle; I found no measurable difference in
> > > > temperature. I do know, however, that my A/C costs dropped considerably
> > > > when I installed the radiant barrier.
> > > How did you do the installation? Did you have any kind of soffit vent, or
> > > did you mount the radiant barrier across the roof supports so as to allow an
> > > air channel between the radiant barrier and the roof?
> > > Did you mount it only on the south facing part of house? Why did you do
> > > just half the roof?
> > > Which vendor and brand of reflective material did you use? Was there any
> > > reason to prefer one brand over another?
> > > Not being familiar with radiant barriers, are they reflective on both sides?
> > > Doesn't dust accumulation lower their effectiveness at some point?
> > > What kind of reduction did you see in AC usage?
> > > --
> > > W
> There seems to be a number of different suppositions at work here.
> The assumption that attic venting is necessary denies the fact that
> cathedral ceilinged rooms or spaces dont have ridge vents or vents for
> obvious reasons, heat loss. The need for asphalt shingles to be cooled
> from below is I believe unable to be substantiated through documented
> side by side testing. Metal roofing far superior to asphalt roofing
> would be a better choice anyway as a shiny silver steel roof will
> reflect infrared eat as silver reflective surfaces do.(If there is any
> doubt about this get a sheet of aluminum foil from the kitchen and
> hold a lighter to the underside (not directly as this would be
> conductance NOT radiation) and check the heat pass through with your
> hand.)
> There is some debate though about the need for heat over the need to
> reflect it. It depends on where you are I expect or if you have a
> ridge water tank you wish to heat up to save money producing hot water
> for your hydronic heating system. If the attic is living space
> accessed by permanent stairs then any heat build up could be vented
> with gable end windows.
> Conversely if a building has a crawl space then stapling reflective
> foil on the underside of the floor joists will save some heat from
> being radiated downward to the cold earth below.This is of course
> usually tricky to do and will in time become less effective due to
> dust etc settling down on it But it does work quite well if the floor
> can be sealed above.
> regards
> Michael Lough