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Climate 4A flash and fill (BIB) vs open cell

Hi, We are building a house in MD in climate zone 4A. I am trying to decide between two different insulation methods for our walls. Our house is all brick, with tyvek, OSB and 2x6 with 16in OC. I have to decide very soon on whether to do 1inch closed cell and the BIB (blown in blanket fiberglass) or whole wall fill with open cell. The open cell is about 30% more cost than the flash and fill so I am trying to decide if it is worth the extra money. Of course my main concern is the dew point and moisture issues. Since I live in climate 4A should I be worried about the moisture issues and just go with the open cell, or will I be OK with the flash and fill?

Asked by sunil patel
Posted Jan 4, 2013 3:35 PM ET


5 Answers

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Flash'n'fill does a better job of ensuring that sun-driven moisture coming off the brick doesn't saturate the gypsum during the air conditioning season, and provides sufficient R value to prevent wintertime condensation on the foam in your climate even without an interior side vapor retarder. With open cell foam you would need an interior vapor retarder, but with the flash'n'fill you don't need and SHOULD NOT INSTALL any thing highly vapor retardent on the interior side. (Latex paint is fine, vinyl or foil wallpaper is not.)

As long as the BIB is blown at 1.8lbs per cubic foot density it won't settle over time, and it will impede any convection or infiltration leaks in the cavity by quite a bit.

The flash'n'fill would also provide a somewhat higher whole-wall value, since open cell foam is R3.5/inch, whereas closed cell foam is R6/inch, and 1.8lb fiberglass is about R4/inch.

What would be better is if the closed cell foam were on the exterior of the OSB, since that would provide a thermal break over the studs and put a ~1perm vapor retarder between the brick & OSB. But as long as there are top vents and bottom weep-holes on the brick to ventilate the cavity, the OSB should be fine with only Tyvek and the moisture-reservoir brick.

Answered by Dana Dorsett
Posted Jan 4, 2013 4:06 PM ET


Keep in mind that an aplication of shredded mineral/glaswool is a health risk.
All mineral wool/glas wool running through a pneumatic pump is being shredded.
If it has to be done for whatever reason a 100% airtight sealing should be included, at all sides of the treated structure.



(part III, 8.2 " man made vitreous fibres").

In Germany (for example) it is cheaper to landfill asbestos than mineral wool, here a price list for various materials of a landfill :


Mineral-/glaswool ( "Daemmstoffe gefaehrlich") a tonne costs € 172 and asbestos containing material ( "asbesthaltige Baustoffe") only €148 per tonne.

Is there a particular reason why you want to live in a haz-waste dump?

Answered by Hein Bloed
Posted Jan 4, 2013 9:30 PM ET
Edited Jan 4, 2013 9:40 PM ET.


Hein Bloed,
Your comment is exaggerated and unscientific. To refer to a house insulated with blown-in fiberglass as a "hazardous waste dump" is an absurd exaggeration.

Among the building materials that have been identified as hazardous are materials with a high concentration of lead, formaldehyde, and (as you imply) asbestos. But it is absurd to put fiberglass insulation in the same category.

Answered by Martin Holladay
Posted Jan 5, 2013 7:07 AM ET
Edited Jan 5, 2013 8:02 AM ET.


Dana, Thank you very much for the information. Based on the info you have provided I think I will go with the 1in closed cell and the BIB.

Answered by sunil patel
Posted Jan 5, 2013 11:16 AM ET


Not the mineralwool itself is carcinogenic but the small fibres resulting from shredding it.

I think you should post a link refering to the WHO or a similar independant health organisation to proof that " it is absurd to put fiberglass insulation in the same category " as asbestos.

The small fibres are created when producing mineral wool, the manufacturers usualy wrap the finished product in sealed 'blankets.. Either with a foil or fabric around the sheets or bonded with a resin.
To run this mineral wool through a shredder/pneumatic pump and blowing it over corrugated surfaces(the flexible tubing) before the actual filling happens does create an untolerable quantity of small fibres.
These small fibres are internationally considered as carcinogenic.
A haz-waste acording to international trade agreements.

The loose mineral wool is therefore not allowed to be sold to amateurs - in Europe that is.

Contact a pneumonologist for further advice, or a licensed waste handler specialised in legal waste handling. Or use google.

Don't blame the messangers, the WHO. Who put mineral fibres and asbestos fibres into the same category more than 10 years ago.

Ask yourself why you don't know about the fact that mineral wool fibres can cause cancer of the lungs, the heart muscle and the diaphragm.

Answered by Hein Bloed
Posted Jan 5, 2013 11:21 AM ET

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