Blowing in the cellulose over a living room is just about okay. All water contents in layers decrease after close-in though the 1mm of cellulose just inside the OSB does bounce up to 23% mass percent water content but the isopleths indicate all is well and inner OSB is dry.

Cellulose blown-in with shower room below is all bad. Water content in all layers heads up and up, taking about 7 years to level out. Water content in the inner 1mm of OSB is averages about 21% but often much higher so presumably that is rotting. Cellulose just inside OSB is wet. Isopleths indicate mould occurring at inside of OSB.

Is this about right or have I got some inputs wrong?

I will report back with findings.

Cheers!

The lack of a damp-proof membrane is very interesting. I’m wondering, in situations where you need to use a radon barrier, would the radon barrier cancel out the benefits you are gaining from not using a damp-proof membrane?

I’m looking forward to seeing more photos. I am especially interested to see how the roof will be constructed!

They can’t say it won’t stand up if the hemplite wall is actually there at ~3.5m high, 300mm thick and timber studs at ~1.2m centres!

The level of engineering support at this stage depends on whether the manufacturer Marcus McCabe of Hempire Building Materials can get funding to involve an IT.

With regard to timber in the hempcrete we are measuring vapour and temperature in the walls (and in two of the studs themselves) so are aware of these limits and looking at the issue closely (over the next few years). What I would say is that almost all hempcrete buildings have timber studs (generally far more, at closer centres): I’ve heard of few failures and the history of this form of construction now stretches back over two decades at least.

I would say that because the material around the timber is hygroscopic and monolithic that the timber won’t take in an excess of moisture, as it might in other wall buildups where moisture is present but the surroundig materials don’t share the moisture burden (being for instance, closed-cell fossil-based insulants etc.

In terms of lime: it is a high carbon material, but has around 60% of the emissions associated with OPC cement (it can be burnt out lower temeperatures, re-calcifies for years afterwards etc). It’s great advantage is that it can bind very well with biocomposites that are carbon-sequestering. Clay is receiviung more interst becuase it should pretty wel be carbon neutral though (as I understand it) it has a physical not chmical bond.

I look forward to meeting you at the WUFI course!

By the way, thanks for the articles in Construct Ireland which helped me think through thermal and moisture detailing in designing our building. Breaking the Mould III was especially good in showing that continuous insulation up and over the eaves really does remove a big thermal break.

I wish I had known about LECA for filling our paving grid foundation, it would have been ideal for the capillary break and yet more insulation.

A hemp-lime building hits the sustainability aim very well as it really can be completely locally produced. Plenty of compromises in my shed, especially the road miles in the wood fibre insulation from Germany – we should be making this stuff here.

In terms of carbon, I have heard that lime is as costly in production carbon-wise as cement. Is this incorrect? Is the amount of lime in hemp-lime relatively low compared to cement in concrete?

Having a good deal of experience of historic building conservation work I do like the earth-lime-hemp material idea, especially its long term performance as a good solid wall (until some new owner covers it with cement render!).  As a carpenter though, I like to keep things dry especially during construction when I’m building it!  A dry build is one point in the timber version’s favour.  

You have timber buried in the Hemplite.  Is this really ok?  I would have doubts having seen a lot of timber decay in working on historic buildings. Is the equilibrium moisture content of the hemp-lime less than the 20% decay EMC limit of the timber? Are you going to be measuring moisture content of the Hemplite through the wall? Presumably the hemp-lime walls moisture content will affect the thermal performance.

I look forward to reading more about the project, excellent to see building R&D happening.