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Old 12-17-13, 10:57 PM   #401
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When I held the IR-thermometer out to the side, I made sure that it was also perpendicular to the surface.
Ah, it seems I misunderstood the point you were making.

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Do you doubt that heat radiated from the body can be reflected from an aluminum surface and measured with an IR-thermometer?-AC
No, not at all. 150 watts per person is a common figure in heat load calculations. Nearly all of it comes from respiration and the exposed head though.

My experience with IR guns makes me distrust them on reflective surfaces, possibly for the reasons you suggest.

BTW, I grew up near Powell Butte in Portland. In the 60's the slogan was "Keep Oregon Green." Last year I saw bumper stickers that said "Keep Oregon Weird." I miss home.

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Old 12-17-13, 11:04 PM   #402
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...I grew up near Powell Butte in Portland. In the 60's the slogan was "Keep Oregon Green." Last year I saw bumper stickers that said "Keep Oregon Weird." I miss home.
Oregon is still here, and it is still green and wierd.

I live in the St John's area. You don't see many of the "Wierd" bumper stickers in this part of town... it would be redundant.

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Old 12-17-13, 11:57 PM   #403
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@ Mikesolar
I guess my problem with this whole tangential discussion is the idea that there is someone in this discussion that supports reflective bubble wrap. No one here does who is at all informed, least of all me. It just seems like a straw man to get people riled up that signifies nothing.

The thing that irritated me so much was the migration of the bubble wrap issue (or vice versa) to Michael's post that the mylar flat reflective material was inherently defective. No evidence except his own heresay is given as evidence. But his description was not challenged because there is so much prejudicial evidence from the reflective bubble wrap issue. As a person who has covered his entire rafters with the non-bubble wrapped version of the stuff I find that objectionable. But for some reason my issue about that is conflated by you and others as a reflective bubble wrap issue. It isn't.

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Old 12-18-13, 12:43 AM   #404
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Part of my irritation is no doubt my own fault. I should have been more direct at the very beginning in challenging Michael's assumptions about the flat reflective barriers and asking for more evidence from him. My bad.
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Old 12-18-13, 12:47 AM   #405
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You are right that I (and others) am concerned with a heating dominated climate and this is why i criticize bubble wrap. We are not used to any heating equipment at all in any attic space in Canada/northern US but I realize that it is quite common in the south. I do scratch my head about its use. I also talk to a lot of heating technicians in the mid and south who are always trying to take a sub-par system (ducts in the attic) and make it better because they get a huge number of complaints with heat loss and condensation in these types of systems. We sometimes have ducts in the attic for cooling only but there is a big trade off between system efficiency and the ability to have cooling in century old hot water heated homes. To my mind, I cannot even conceive of designing a system with ducts in the attic. That said, if you inherit a system like this, you must live with it and try to find ways to make it work better.

I have no problems with radiant barriers where appropriate but the one big problem is when they are misrepresented as having an R value that they simply don't have. I have seen too many very unhappy people who relied on tarps under slabs.

I agree with the use of radiant barriers in attics but, that too, is not used in our climate much. Having it on top of batt insulation is a good idea partly because it will reduce air movement within the batt which reduces its R value a great deal. Having it below the batt, is, in my opinion useless as that air space is still needed for IR reflection.
In the southern US, usually square footage is more expensive, typically homes don't have basements(which is where we normally put ducts and furnaces in the North), and people down there building houses don't think the public wants an air handler or furnace in a closet near the kitchen(noisy near the bedrooms or living rooms). There's more to it than that but if I had to move to the South for some reason and bought a house with ductwork in the attic, I'd seal up the attic, insulate the attic, and seal all the ductwork(so the air inside the ducts can't touch the air in the house). I'd likely remove it rather than just close it off though because insulating and sealing the attic would be easier. In the southern US I'd want the most cooling efficiency I can get and the winter isn't that cold so both of these coins add up to a mini-split setup. ..just don't forget to deal with solar gains through windows. I'd still do R60 in the attic, even down there, that way I don't have to care how hot the attic is.
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Old 12-18-13, 01:19 AM   #406
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Part of my irritation is no doubt my own fault. I should have been more direct at the very beginning in challenging Michael's assumptions about the flat reflective barriers and asking for more evidence from him. My bad.
Hi Exeric...is this you being more direct and asking? I'm sorry to seem dense, but what were my assumptions about the flat reflective barriers? mm
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Old 12-18-13, 01:48 AM   #407
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Well Michael, you said that in your experience the reflective material tends to just flake off. That certainly isn't my experience. Maybe what you are looking at is based on a different substrate from what I'm using. I don't know. What I'm using is a plastic poly type substrate and the silvery material is stuck on very securely. I don't see much of an issue there with it flaking off.

Also, you said that you didn't think that it would reflect radiation because one side of it is in contact with a surface of some kind, be it the substrate itself or something else. That isn't the way it works. Only one side needs to have an airgap. The other side can be in direct conductive proximity to any material. That is the physics of a reflective material - it does not conduct light or heat from one side to the other, but instead reflects it back.

Sorry to be so late with this.
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Old 12-18-13, 06:19 AM   #408
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@ Mikesolar
I guess my problem with this whole tangential discussion is the idea that there is someone in this discussion that supports reflective bubble wrap. No one here does who is at all informed, least of all me. It just seems like a straw man to get people riled up that signifies nothing.

The thing that irritated me so much was the migration of the bubble wrap issue (or vice versa) to Michael's post that the mylar flat reflective material was inherently defective. No evidence except his own heresay is given as evidence. But his description was not challenged because there is so much prejudicial evidence from the reflective bubble wrap issue. As a person who has covered his entire rafters with the non-bubble wrapped version of the stuff I find that objectionable. But for some reason my issue about that is conflated by you and others as a reflective bubble wrap issue. It isn't.
Exeric,
Please read my posts on this again. I am NOT dissing radiant barriers although I think the insulation aspect of the bubble part has been misrepresented by the industry.

I am, however, stating where, in MY climate, they will work best. Mylar coatings are great and like I said somewhere earlier, I have used them as a radiant barrier first in 1993, and still do. That house did not use bubble wrap just mylar coated building paper (which is still in good shape, BTW.

For most of my history I hated cooling because it was never needed where I grew up. No one had it. Things are different now and cooling is being demanded and I have to work with that.

Your reflective barrier in the attic is a good choice and I have nothing against it.
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Old 12-18-13, 06:20 AM   #409
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Hi Exeric...is this you being more direct and asking? I'm sorry to seem dense, but what were my assumptions about the flat reflective barriers? mm
I think it was me that he referring to.
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Old 12-18-13, 10:55 AM   #410
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That makes me feel a lot better. No hard feelings on my part. Continue as you were, all of you.

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