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Opinions regarding European hollow insulating clay bricks

I just stumbled upon a type of clay brick that is apparently gaining popularity in Europe but seems totally unknown here in the USA. Example: http://www.juwoporoton.com/products/

The bricks are hollow, full of tiny vertical cavities that trap air and, apparently in conjunction with the air-entrained brick itself, claim to render the masonry material capable of being an insulator. Some types of brick have mineral wool stuffed in the cavities. R-values appear to be roughly 1.7-2.2/inch. The exterior structural bricks are very thick; 12-18 inches. The whole-wall R-values aren't amazing, but top out at 40 for the really thick bricks. Whole-wall R-40 certainly isn't bad by any stretch of the imagination. And the large and interlocking characteristics of the bricks seem to lend themselves to rapid construction. They look to be fairly lightweight for their size, but have been tested to withstand small arms fire.

Does anybody stateside have any experience with these types of bricks? Any opinions? Any clue what they cost over in Europe? I haven't been able to find any pricing online.

Asked by Nate G
Posted Aug 16, 2014 11:55 PM ET
Edited Aug 17, 2014 11:53 AM ET


5 Answers

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I've seen clay bricks like this used in my part of N. Carolina in structures dating from the 1930's or 1940's. I imagine thermal bridging rather than overall R-value would be the main thermal performance concern in contemporary use.

I've also seen them used extensively as curtain wall infill in contemporary concrete frame construction in Greece: the thermal bridging of the concrete frames alone must be horrendous but nobody seems to worry about it. Climate or culture, who knows.

Answered by James Morgan
Posted Aug 17, 2014 1:16 PM ET


In any case if you are interested in masonry alternatives to wood frame construction you'll probably find AAC block (Hebel etc.) a better supported and more available option, also that's somewhat more familiar to US contractors and code officials.

Answered by James Morgan
Posted Aug 17, 2014 1:21 PM ET


Yeah, AAC seems to be the local equivalent, although it seems to be popular in Europe too. The R-value per inch is much lower, though; around 1.25. You would need an almost two-foot-thick thick wall to even get a moderately reasonable whole-wall R-value of 30 (ignoring any potential climate-specific mass benefits). A wall built out of these bricks would only need to be 14 inches thick to reach that level of performance (again, ignoring potential mass benefits).

As for the thermal bridging, to a certain extent, the entire brick looks like a big thermal bridge due to being all masonry, but there's definitely more solid brick than trapped air at the edge. There are versions that address this: http://www.info-haus.com/ua/966/porotherm-44-eko-jak-pobuduvaty-cegljany...

I admit it's hard to wrap my mind around it. I understand air entrainment and trapped air in cavities, but a structural masonry unit with an R-value per inch of more than 2 seems pretty cool to me. I wonder why we don't use these things stateside.

Answered by Nate G
Posted Aug 17, 2014 1:31 PM ET


If the thermal values live up to the manufacturer's claims there could be a future for this in the US market among those seeking alternatives to the standard constructional systems. Juwo would almost certainly need a manufacturing base here though to make it cost-effective as well as a trained sales/support presence.

Answered by James Morgan
Posted Aug 17, 2014 1:59 PM ET


There can be surface spalling /flaking issues with some of these blocks in cold/very cold climate (colder winters than central Europe), but different firing temps & glazes can probably adapt them for use in colder climates too.

Making them truly air-tight over the long term is still an issue, as it is with CMU or other masonry builds, but more important here.

Insulating terra-cotta blocks were in fairly common use in the southwestern US prior to about 1925 or so, and terra-cotta decorative siding was in use in many parts of the US in the late 1800s. The higher structural strength and low cost of site-made cinder block (and later factory manufactured CMU) is what probably what ended the clay-block biz in the US. Similar products have been in use in Latin America forever. Terra-cotta roofing tiles seem to have hung on in the southwestern US, even as the structural terra cotta market faded.

Answered by Dana Dorsett
Posted Aug 18, 2014 6:31 PM ET

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