Any talk or rumors on base case u-values for the next revison of Part L? Will there be changes for existing buildings and new? Or will improvements be driven via a more onerous target method - such as CSH levels or Passive House [kWh/m2/a]?

In Ireland the Dept of Environment issued a public tender last December for a revision of the series of Acceptable Construction Details - scroll down here http://www.environ.ie/en/TGD/ .

Condensation risk analysis ( surface and interstitial ) is to be performed on all the series of details with "backstop" wall U Values of 0.21 , 0.15 and 0.12 . ( Currently wall min U Value is 0.27 )

BRE Scotland won the contract . We eagerly await the output .

James - Yes and no!

Thermal wall bypass will be interesting.

As I understand it they are retrospectively bringing in party wall thermal perfromance and applying it to SAP 2005.

SAP 2009 then has to be 25% better than SAP 2005 but with the 'bar dropped' becuase of the party wall thermal bypass issues.

So..... for instance, if you fully fill your party wall cavity on a mid terrace with thermal insulation, you won't have to do anything else (broad statement but pritty true) to achieve the new sap 2009 target.

That is how I understand it.

So it is not quite so straight forward as 'next csh target'

Timber

Mike I take it your figures above are based on 50mm pir with aac internal leaf ?

I've had u-value figures back from springvale showing 0.28 for: 7N Block/100 Plat Ecobead/102 Brick face
for upgrading existing structure of project i'm on.
also have u-values for 120, 150, 170 and 200 cavity thickness for new work - (200mm achieves u of 0.15)
firms claims for suitability in brick face buildings are backed up with bba certs and bco is happy with it.

No sorry mike should have clarified that is blown eps, hence 100 into the existing structure at 0.28
i'll email the docs i have over on the u-values
product info and bba is here
http://www.springvale.com/products.asp?InfoID=525&mySub=517

If you prefer to install yourself they have insulation batts with t'n'g and bell grooves over lateral joints

Don't bet on it just yet Tom

1. Protection against weather [icluding the insulation]
2. Flexible appearance
and yes
3. Familiarity

Not sure it costs any more than alternative methods at the same u-value

Posted By: fostertomJust needless cost, right down to the founds, being thrown away by builder/developers. Not to mention unnecessary embodied energy/eco cost.

I can see the quality control benefits of external wall insulation, but I'm not convinced on cost or embodied energy.

Why is it cheaper to build a 200mm solid wall, pay a specialised company to fit expensive external wall insulation/membrane & pay a plasterer to render than it is to build 2 leaves of 100mm masonry filled with low cost mineral wool insulation? Window openings for wide cavities are handled in much the same way as window openings for external wall insulation. The cavity wall requires an additional lintel to outer leaf, but this can be just a low cost brick angle, as used by Tony.

Assuming the foundations have an equivalent thickness of vertical perimeter insulation, what is the difference in cost between a cavity continued down to the concrete strip with 100mm masonry either side & a 200mm solid wall with insulation & rodent barrier to outside?

What is the difference in embodied energy between a 200mm solid wall covered with extruded polystyrene insulation & 2 leaves of 100mm masonry filled with mineral wool insulation?

David

No 1- I'll believe that when I've seen it survive the same perod as say an Engineering brick wall
No 2 You can have any appearance you like with a cavity wall. Not so with EWI, unless you include things like Brick slips, which destroy any argument relating to cost
No 3 can be argued either way so agree.

Theres an excellent paper by Joseph Lstiburek on water managed wall systems
http://www.buildingscience.com/documents/primers/bsp-063-water-managed-wall-systems/view?searchterm=stucco
and another titled 'the perfect wall'
http://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall
there are some excellent points in these documents
the caveat being that these are based on lightweight construction i.e framed internal leaf.

it seems to me that mike is espousing cavity construction with rigid insulation and a ventilation gap whereas davids angle is cavity with full fill mineral wool.
just think its worth noting that these are cousins within the the family of cavity wall but a benefit of one doesn't necessarily stand up for the other. ie drainage planes, tie clips, continuity of insulation, workmanship.

an aside:
more recent docs from building science.com on framed walls here
http://www.buildingscience.com/new-documents/

If we're talking 300mmm thick walls or even 500mm thick then how about hempcrete.
0.23 for 300mm and 0.14 for 500mm.

built and tested. nice little comment about the hotbox test too, just for tom!
http://constructireland.ie/Articles/Design-Approaches/Ecological-innovation-at-Down-hemp-lime-house.html