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jeff5may · 12-16-13, 07:41 PM

That's what I've been trying to do here! Together, we are strong.

In particular, Michael and Daox are both in the process of self-installing fabulous hydronic heating floors of different kinds. The debate started when Michael asked questions regarding the effectiveness of a radiant barrier when combined with between-joist fiberglass insulation underneath. Since then, half a dozen of us or more have chimed in, weighing the pros and cons, as well as dispelling some of the hype that has propagated through the industry. I have taken the position that for best performance, this product should not be relied upon as a "do-all" solution.

AC, you know the deal with sealing and insulation. There are many ways to perform the job as well as a large menu of products to choose from. The end product is only as good as its weakest link, so much contemplation must be done throughout the testing and planning phases to ensure proper product choice as well as execution.

I am a believer that anything worth insulating is worth super-insulating. I hope to sway at least some of our audience in that direction. Much like diamonds, insulation is a one-time investment that just keeps on giving more and more as time goes on. It ain't cheap, but it sure feels good once you have it.

Especially with slab-on grade hydronic installs, that 2 or 4 extra inches of foam board on the ground will only save you money later if you put it in now. After the concrete goes in, it's too late. With the underfloor situation, I don't expect that all readers will decide to generously use aluminum heat spreaders and insulate their joist cavities to R-40 value with spray foam below dubble-bubble radiant barrier, even though that's what I might do. I do, however, expect a reader to check his or her plan and at least consider filling that space with something (rather than nothing). Small steps lead to big journeys.

To answer your question more directly, I believe the reflective bubble wrap, when used in an airtight cavity between joists or studs, placed 1" under a radiant floor or 1" away from interior wallboard, has an R-value of 3.2, and an emissivity of 5%. IMHO, this is not enough insulation, and I would recommend adding at least 4" of foam board or spray foam to fill the cavity under the radiant barrier to increase this value to above r-20. As with any insulation project, if you still have space, fill it in with more insulation for best results.

12-16-13, 07:41 PM	#395
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	That's what I've been trying to do here! Together, we are strong. In particular, Michael and Daox are both in the process of self-installing fabulous hydronic heating floors of different kinds. The debate started when Michael asked questions regarding the effectiveness of a radiant barrier when combined with between-joist fiberglass insulation underneath. Since then, half a dozen of us or more have chimed in, weighing the pros and cons, as well as dispelling some of the hype that has propagated through the industry. I have taken the position that for best performance, this product should not be relied upon as a "do-all" solution. AC, you know the deal with sealing and insulation. There are many ways to perform the job as well as a large menu of products to choose from. The end product is only as good as its weakest link, so much contemplation must be done throughout the testing and planning phases to ensure proper product choice as well as execution. I am a believer that anything worth insulating is worth super-insulating. I hope to sway at least some of our audience in that direction. Much like diamonds, insulation is a one-time investment that just keeps on giving more and more as time goes on. It ain't cheap, but it sure feels good once you have it. Especially with slab-on grade hydronic installs, that 2 or 4 extra inches of foam board on the ground will only save you money later if you put it in now. After the concrete goes in, it's too late. With the underfloor situation, I don't expect that all readers will decide to generously use aluminum heat spreaders and insulate their joist cavities to R-40 value with spray foam below dubble-bubble radiant barrier, even though that's what I might do. I do, however, expect a reader to check his or her plan and at least consider filling that space with something (rather than nothing). Small steps lead to big journeys. To answer your question more directly, I believe the reflective bubble wrap, when used in an airtight cavity between joists or studs, placed 1" under a radiant floor or 1" away from interior wallboard, has an R-value of 3.2, and an emissivity of 5%. IMHO, this is not enough insulation, and I would recommend adding at least 4" of foam board or spray foam to fill the cavity under the radiant barrier to increase this value to above r-20. As with any insulation project, if you still have space, fill it in with more insulation for best results.