Came across a fairly negative discussion of this in Building Magazine (under headline 'Retrofit Reality Check'). The original report is here http://www.jrf.org.uk/publications/temple-avenue-project-energy-efficient-homes

Anyway, not sure what the take away message is other than that to get the best performance you need to pay attention to details, which is not rocket science. Oh, and the Green Deal is screwed. But I think that was also a given.

Hi,
Thought I’d update this one as finally got round to reading the retrofit article.

The retro fit was £12k “The standard improvements were typical energy-saving measures likely to be implemented under the Green Deal. These were carried out by the type of approved contractors likely to be used by householders” and the radical retro fit £50k the radical was supposed to quote “radical retrofit was carried out to bring the house up to the same standards of energy efficiency as a new-build, Code for Sustainable Homes level 4 home, with before-and-after energy performance measured once more”

For the benefit of those not accessing the full article the green deal was screwed because (my paraphrasing)

The underperformance of the measures will impact negatively on the payback period for the improvements, which means householders will pay more in interest. The government has realized this and on 12 June published so-called “in-use” factors that build an allowance for underperforming energy efficiency measures.
The measures available under the Green Deal have been assessed for likely in-use performance and these figures will be used to calculate the savings, and whether the measure meets the golden rule which states that savings on bills must exceed the cost of the measures within a 25-year period.
This could mean the savings on bills wouldn’t be as great as predicted, extending the payback period. This house was evaluated by experts using the full version of SAP rather than a simplified version, RDSAP, which will be used by Green Deal assessors in a modified form. These are unlikely to have the same degree of training as low energy specialist xxxxx, which did the calculations so the predicted heat loss could be even less accurate.
There is already a growing body of evidence that points to a yawning chasm between the theoretical and actual energy performance of new homes. This so-called performance gap can be huge - in some cases, up to three times more energy is needed to keep a new house warm than the original design prediction.

So real life doesn’t come up to expectations – no surprise there!

The new build report is at

This is interesting as it does offer typical installation pitfalls so is worth a read

http://www.leedsmet.ac.uk/as/cebe/projects/tap/tap_part1.pdf
Temple Avenue field trial – Evaluation of design & construction process and measurement of fabric performance of new build dwellings

I would recommend a read of this to any builder / specifier / self builder or those with a sub-con / installation team on site, unless the whole team is absolutely on the same wavelength on the need for really tight detailing you will have to be “eyes on” the whole time on everything.

Relevant to a couple of current threads regarding installation and attention to detail wrt air tightness / thermal performance a couple of examples:

The architects appeared to have attempted to minimise penetrations through the air barrier and building fabric; a principle not adhered to so rigorously by the services designers. A number of these penetrations appeared to be ad hoc decisions made by the installers and not through design. The installers regularly appeared to bear little regard for the integrity of the air tightness barrier and thermal performance.

Additionally for example, the expert insulation installers had used black gaffa tape to seal the membranes which proved to be less adhesive than the force exerted by the door blower test so they popped open.

Worth a read if only to reinforce that this level of attention to detailing is very necessary and your own expert might not quite so up on it as they tell you.

Cheers, Mike up North