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radiant barrier revised

Posted by sierraeast (My Page) on
Mon, Nov 28, 11 at 17:44

In a discussion that was so eloquently pulled concerning radiant barrier, an article was posted that gives anyone out there a pretty good lesson on the pros and cons of radiant barrier especially if you scroll down and go through the discussions of the sites forum/comments section. Radiant barrier is as misunderstood as most any insulation type or materials types for that matter when you rely on mfgr's/distributors claims. Research of what works in your area coupled with the correct install is what makes efficiency happen. Radiant barrier as I have learned has little to do with r-value and shouldn't even be considered an insulation but rather it coincides with insulations concerning heat gain/loss. At the advise of an ex NASA engineer who worked extensively with radiant barrier at NASA layed out an install for our build for it's intended use and we are happy with the results. It might not make sense in other regions and our application is for heat loss control which isn't radiant barriers most popular consideration according to the hype. It's geared more for heat gain control, but despite beliefs that heat gain control is it's only advantage in attic areas, it is accomplishing what we were looking for on our build coupled with our insulation/venting type. It works for us but wont for others that's why it's so important to research your zone and area and stay away from mfgr's claims. An r-38 batts insulation might be close to r-38 in some applications where in others it is far less,(or greater if coupled with a companion that compliments it). It's like saying you are going to get 50 years out of a claimed 50 year shingle which could happen in some areas where you will only get half that in other areas. I just brought this back up in the event others are curious about radiant barrier where the previous thread was wisked away in cyber space! Here's the article:

Here is a link that might be useful: radiant barrier


Follow-Up Postings:

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RE: radiant barrier revised

the previous thread was wisked away in cyber space!

The result of an advertiser's complaint? (Certainly a change from detergent and support lingerie for full figured women.)

The effective and economic use of radiant barriers is limited.


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RE: radiant barrier revised

Agreed worthy. Why in the world does Sierra make a rambling case for them and then reference a great article on why they are a waste of time and money? Weird.


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RE: radiant barrier revised

If you took the time to actually read the article and the comments below it, you'd see there are cases pro and con along with some other useful information for unbiased folks unlike yourself who throw it out that Im representing a product which I'm not. Your comment shows that you are as one sided in your thoughts as you think I am on this topic. Just thought it might be useful for those looking into radiant and thought it was a decent article. There are many more out there including the epa's/gov website, building science, green building.com, etc.


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RE: radiant barrier revised

Iam sorry if I was rude but I just thought it was strange you would post that particular article after what you said.

To sum it up it says the only place RBs might make sense is when you substitute a comparably priced RB backed roof sheathing with regular roof sheathing in a vented attic that contains HVAC ducts or equipment.

As any good energy efficient designer knows, HVAC components inside of a vented attic is not a good idea. Where exactly do RBs fit in now? As the author points out, there is one other good situation: an un-insulated barn.

That leaves most of us to conclude that "The effective and economic use of radiant barriers is limited."


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RE: radiant barrier revised

While I respect Mr. Martin's findings, there are many effective ways for r.b. to work in conjunction with many insulation types, venting applications, heat gain as well as heat loss control if you would broaden your resaerch and not base it solely on one's opinion. I can give you the number for the person who layed out the install on our build and you can get his take on it's effectiveness as well as economic use. He will tell you as you aleady know the dont's and lack of effectiveness on certain install aplications and as with most sciences, it's all about geographic location concerning effective energy saving steps that work in that particular area. Here in the mojave desert,(where we currently reside), where ducting is run in blistering hot attics, I have succesfully cooled down attics with radiant barrier by using a procedure that involves continous run ridge venting, continous run soffit venting coupled with the r.b. being place on the underside of the rafters, (trusses in all cases here), where each rafter space is an independent air channel trapping the heated air and pushing it up and out the ridgeventing by way of flow from the soffits. I disagree with Mr. Martin that tech sheild osb foil faced sheathing is at all effetive as there is no where for the heat to go due to lack of air spacing. Real world application/installs here in the mojave and if interested you can contact me by e-mail and I will give you those clients numbers along with Mr. Sumpolec who retired as a NASA engineer and worked extensively with radiant barrier who was instrumental in laying out for heat loss control on our build in the sierra nevadas. If you scroll down further on your article, you'll find positives experienced by commenters who are using r.b succesfully. You need to read up entirely.


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RE: radiant barrier revised

I'm sure Mr. Sumpolec knows what he is doing and I'm sure Sierraeast's house is better designed because of it.

However, for those of us who are expected to design these systems without the assistance of a consultant, advice doesn't get any better than that offered by Martin Holladay. Searching for his comments at the JLC.com can be quite an education.

Thanks Sierraeast; great article and discussion although I lost my concentration after 40 of them and missed the ones you are talking about.


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RE: radiant barrier revised

good article sierraeast.
I always love the comments of both greenbuilding advisor
and energy vanguard's blogs.
don't know how I missed the thread that was
pulled. I usually participte in RB threads.

I've advocated the use of radiant barriers for
a long time in my hot humid climate.
I installed my RB quite some time ago.
(R-30 attic no ductwork in attic, RB on undersides
of rafters with single sided foil facing into attic space)
no recessed lights all penetrations between attic
and living space are well sealed.

in my area, in new construction products like
techshield were popluar for a while..but as we
continue to stupidly put ducts in attics..
more folks are opting to create an unvented
attic with open cell foam.

this is happening in both new and existing homes.

the competition for RB in my area is open
cell foam which covers the problems of
openings in ceilings from attic to living space,
and equipment & ducts in attic.

if we would DESIGN for ducts in living spaces
then we wouldn't have to spend 3x the insulation
cost for foam to overcome holes in air barrier
and ducts/equipment in hot attics.

one cost effective way to combine both foam
& RB (again with ducts in conditioned space)
is to put RB at roofline, and use foam at the
attic floor. even a minimal amount of 2" would
seal most holes. then insulate with conventional
insulation to required value.

RB's have been around a LONG time.
we use a form of RB on exterior walls.
exp polystyrene sheathing boards with foil
facing out on exterior of walls. the
foil isn't as beneficial as in the attic
where the sun shines all day, as walls usually
only get sun for certian hours of the day.

it always makes me mad to see the RB folks that
come around spring & fall to sell RB laid on
top of exisitng attic insulation on the attic floor.
that too was part of the comments in the link.

thanks again for the link.


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