Hemp insulation

[pandamonk]

I finally bought some rigid fiberglass today (£40+vat for 20 4'x2'x2" 45kg/m knauf rocksilk), and I'm quite happy and excited that I'm in the final stages of construction(just doors to hang, and panels to make).

Anyway, my mum was in B&Q earlier, and brought me a leaflet of energy efficient products, including insulation. I had a flick through and came across Breathe Natural hemp insulation. It's 1200mm x 375mm x 75mm, and 35kg/m. 8 for £27, so dearer than the rocksilk and less material, but it's better for you and the environment.

How do you think this stuff will compete with the rocksilk? It's less dense, but so is bonded logic ultratouch. I've emailed asking for absorption coefficients.

Also, I have Alesis M1 active MkIIs, and am wondering if i will suffer the same sbir effects as monitors with rear ports? What thickness is best to treat sbir? And is it just directly behind the monitors that need treatment?

Would this be ok(hope you can understand it)?

[pandamonk]

This is the response to my email:

"Thanks for your enquiry. I have some acoustic data for another hemp insulation product called Isonat (see http://www.naturalinsulation.co.uk/d...93C&lc=English and follow the links to the downloads. I also have Random Incidence Sound Absorption to BS EN ISO 354:2003. The aw is 1.00 and is described as class A.Breathe would have the same or better acoustic performance as the density is a little higher (40kg/m3). I hope that this helps."

He linkewd me to info on sound isolation, but he mentions Random Incidence Sound Absorption. What does he mean by "The aw is 1.00"? I am googling it, but haven't come across it yet.

I've come across aw being used for rockwool(100mm 60kg/m) which was 1.00. It had absorption above 1.00 down to 160Hz, then tailed off to 0.33 at 100Hz. Is aw similar to NRC?

[gullfo]

aw is the "weighted sound absorption value" (the "a" is normally the Greek letter alpha). its generally related to speech intelligibility and is a coefficient, not the same as NRC. I believe its related to "SPEECH-INTERFERENCE LEVEL (SIL)" or "ARTICULATION INDEX (AI)".

http://www.sfu.ca/sonic-studio/handb...ion_Index.html

[pandamonk]

Thanks gullfo. I'm readying, but still confused

Why would they rate it insulation in speech intelligibility?

EDIT: Do they mean, when it is used in wall construction?

[gullfo]

Originally Posted by pandamonk

EDIT: Do they mean, when it is used in wall construction?

i think the aw value was in the "acoustic performance" report... obviously they intend to have it used for acoustic absorption as well as insulation... just like 703 and other rigid insulation products have acoustic, insulation, fire rating, VOC, etc... type data

[pandamonk]

Originally Posted by gullfo

i think the aw value was in the "acoustic performance" report... obviously they intend to have it used for acoustic absorption as well as insulation... just like 703 and other rigid insulation products have acoustic, insulation, fire rating, VOC, etc... type data

Ok, so should i just look at products with similar densities etc for absorption coefficients? 'cause that's all the info they have, i believe. Will hemp have the same absorption characteristics as fiberglass?

[gullfo]

http://www.bobgolds.com/AbsorptionCoefficients.htm has a massive collection of absorption data on a bunch of materials. assuming the materials are tested in a standard fashion, the coefficients should be comparable whether its hemp, rigid fiberglass, recycled jeans, etc...

[pandamonk]

Originally Posted by gullfo

http://www.bobgolds.com/AbsorptionCoefficients.htm has a massive collection of absorption data on a bunch of materials. assuming the materials are tested in a standard fashion, the coefficients should be comparable whether its hemp, rigid fiberglass, recycled jeans, etc...

Ok, thanks. Yeah i know about the bob golds collection.

[MessianicDreams]

Originally Posted by pandamonk

Will hemp have the same absorption characteristics as fiberglass?

hey look on the bright side: if it doesn't do what you want it to do, you can still roll it up and smoke it :P

[pandamonk]

Originally Posted by MessianicDreams

hey look on the bright side: if it doesn't do what you want it to do, you can still roll it up and smoke it :P

Haha. nice one!