Plans showing proposed building in Chester

EnerPHIT Retrofit 3: Why choose Passivhaus EnerPHit standard?

Posted on 22/06/22

In my last article I talked about why we would be undertaking the renovation of the property we purchased and moved into earlier this year as a step-by-step process, rather than doing everything in one hit. I also made reference to the Passivhaus EnerPHit Retrofit Plan. I am a Certified Passvihaus designer so it won’t be surprising then that I can confirm we will be doing the works to the EnerPHit Standard. This article should shed light on why though. Why choose Passivhaus and EnerPHit over another low energy standard or the route of just doing things as we see fit, when we can?

What other options for low energy design are there?

AECB CarbonLite retrofit

Another option for low energy design that is already established in the UK is the AECB CarbonLite retrofit programme/method. The AECB (Association for Environment Conscious Building) is a network of individuals and companies with a common aim of promoting sustainable building.

Running since the 1980’s, the AECB is the largest and oldest network for sustainable building. The AECB CarbonLite™ Retrofit Foundation training course brings together a wealth of knowledge on low energy building retrofit and methodology. On completion of the training, graduates will have a deep understanding of the issues that can arise from the repair, insulation, draught proofing, and ventilation of existing buildings, along with the knowledge enabling them to avoid or manage unintended consequences. The AECB is an excellent organisation and the CarbonLite retrofit programme is an excellent route for many property owners to consider for existing buildings in the UK. However, the performance standards of the programme are not as demanding as those of EnerPHit so, whilst you will still have a far higher achieving and more comfortable house than if you were to do nothing, it won’t be as high-performing and comfortable as it would be if done to EnerPHit standards. There are other performance standards internationally, such as “R-2000” in Canada or “BR77” in Denmark, but these are not established in the UK.

Element by element approach

This approach is a more prescriptive method – each element would be done in isolation and wouldn’t necessarily tie in with each other as a whole. By doing things this way it would be hard to gauge the final effect of the individual works, as a whole building, and therefore hard to quantify and maximise return on investment. Although past experience helps, this method is basically guessing and “hoping for the best”. This could lead to unintended consequences, such as weak-spots in the fabric (particularly at junctions e.g. floor/wall) and potentially inefficient investment.

EnerPHit retrofit: the perfect solution

Carrying out step by step works to EnerPHit standards will achieve what we want in a way that is manageable for us. The EnerPHit Retrofit standard, in my opinion, is the pinnacle of retrofit standards. It is independently certified by an approved assessor on behalf of the Passivhaus Insititut. As well as the Passivhaus Institut in Germany, additional support is provided by the Passivhaus Trust based in the UK. The support and PHPP (Passivhaus Planning Package) software is provided in English, which helps me greatly. As well as these benefits the PHPP software allows the following:



1. accurate calculation of the gain/benefit of each phase of work

2. evaluation of a sensible / financially sound timeframe for refurbishment to be planned for the scheme – up to the next 50 years in principle.

3. the ability to refine each element in terms of cost/performance and payback.

So, having explained the reasoning for opting for the EnerPHit step-by-step retrofit route, what are some of the benefits of utilising the EnerPHit standard and PHPP package?

  • Thermal insulation levels raised means increased internal surface temperature, so condensation and mould growth can be excluded.
  • Temperature distribution on the inside is much more uniform, providing for an optimal level of thermal comfort – I’ve always been sensitive to draughts, which can be caused by convection.
  • It is likely that I will go down the route of external insulation. If so, due to the thermal mass of the heat storing wall, comfort is also improved during hot periods: indoor temperature will be more comfortable and will fluctuate less. The same applies in the case of improved windows. 
  • If the heating or cooling system is renewed later on, then a smaller output will be sufficient (more cost-effective and more efficient). At the point of design and installation of the heating system, even more money can be saved by these measures.
  • Through modernisation using Passivhaus components, the heating demand in climates requiring heating can be reduced by up to 90%. This is substantiated by calculations of the demand using the Passivhaus Planning Package (PHPP), as well as by consumption measurements in the context of monitoring in what is now a whole range of realised projects. CO2 emissions for heating buildings are also reduced, at least to the same extent. In climates requiring cooling, the cooling and dehumidification demand may be reduced by 50-80 %.

I’m thinking of it as forward spending. The saved costs for energy will offset at least some of the costs for investment and capital, so thermal protection measures to the Passivhaus standard could result in financial gains for us in the future.

To find out more about EnerPHit and Passivhaus design, contact our team.

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