Below is research carried out by [Johnston et al 2014] D. Johnston, D. Farmer, M. Brooke-Peat & D. Miles-Shenton (2014): “Bridging the domestic building fabric performance gap”, Building Research & Information, DOI: 10.1080/09613218.2014.979093.
The direct link to the article is here http://dx.doi.org/10.1080/09613218.2014.979093
The abstract to the above research says “It is recognized that there is often a discrepancy between the measured fabric thermal performance of dwellings as built and the predicted performance of the same dwellings and that the magnitude of this difference in performance can be quite large.This paper presents the results of a number of in-depth building fabric thermal performance tests undertaken on three case study dwellings located on two separate Passivhaus developments in the UK: one masonry cavity and the other two timber-frame. The results from the tests revealed that all the case study dwellings performed very close to that predicted. This is in contrast with other work that has been undertaken regarding the performance of the building fabric, which indicates that a very wide range of performance exists in new-build dwellings in the UK, and that the difference between the measured and predicted fabric performance can be greater than 100%. Despite the small non-random size of the sample, the results suggest that careful design coupled with the implementation of appropriate quality control systems, such as those required to attain Passivhaus Certification, may be conducive to delivering dwellings that begin to ‘bridge the gap’ between measured and predicted fabric performance.”
Wolfgang Feist (Passive House Institute) comments below sum up the reason for a passive house outperforming other new builds :
“It is not by chance, that the Passive House standard does a good job: It is the merit of the Passive House research to identify those parameters, which are crucial for good energy performance of buildings – in a heating climate these are:
1) Insulation level, 2) airtightness, 3) avoiding thermal bridges, 4) high performance windows and 5) heat recovery ventilation.
It is also crucial to make the methods available, how to do a proper design in order to meet the standards needed for 1) to 5). The most important tool to achieve that is a reliable energy balance tool – that is the #PHPP. PHPP is easy to use, transparent and reliable – a tool, any architect can use to optimise his design.
There is a third crucial part to it: That is, to have reliable performance date of the components. If a HRV-unit is labelled “82%”, it should have at least 82% of heat recovery. This is, what the Passive House Institutes product certification offering is all about.
Having said that, sure, there is also the issue of the construction quality at the building site. Yes, you will have to control, whether the specified components have been used and yes, you will need a pressurization test (“blower door”, n50). Be aware: The better your design was and the more reliable the components, the less the potential mistakes which can (still) happen on the building site.
“There has always been a little bit too much stress of the last topic: I can’t resist to argue, that architects and engineers like it to hide behind the so called “bad workmanship”. From all our experience, it became very clear, that more than 80% of the contribution to good performance is within the design process. If you do not specify the air tight layer and the junctions – the handicrafts will not solve that at the building site (actually, they can’t). If you use poor double pane windows – the extra losses can’t be compensated for. If you do not choose insulating spacers in the glased units – do not complain about “performance gaps” later.
………you will have to design for low thermal bridging, air tightness and insulation. You will have to choose components which have been independently tested. You will have to deliver drawings which show, how the window is installed (well, you could use the drawing delivered together with a Passive House certified product – that is another advantage of the certification). And you’ll have to make use of the #PHPP – using #DesignPH makes that a fun thing to do.”
In a housing comparison in Austria similar results were found. Comments below from Wolfgang Feist .
“Energy Monitoring in Existing Passive HouseHousing Estates in Austria”
The analysis of 24 residential complexes in Vienna (completed between 2003 and 2008) clearly shows that shape factor and construction costs are closely related. More compact residential complexes are far cheaper. A shape factor of 0.2, 0.3, or 0.4 m²/m³ results in costs of around 1,300, 1,400 or 1,500 €/m².
Passive Houses cost roughly the same as low-energy homes.
The measured energy consumptions for heating have been roughly 10 kWh/(m²a) (brute-area) for the passive hosues with only little difference between predicted (grey in the figure) and monitored (green in the figure). The low energy buildings, built at the same time, roughly consume three times of this.”
[Treberspurg 2010] Univ. Prof. Arch. DI Dr. Martin Treberspurg; DI Roman Smutny; Ass. Prof. Dr. Alexander Keul; Grünner, Roman
“Energy monitoring in existing Passive House housing estates in
Austria”, in: proceedings of the 14th international passive house conference (English edition), Passive House Institute, Dresden and
Darmstadt 2010 ISBN 978-3-00-031154