The one aim of anyone who builds a home to the PassivHaus standard is to reduce energy consumption. The standard was developed by Dr Wolfgang Feist over the last 20 years in Germany and its purpose is to reduce the amount of energy which a house uses.
The standard does not focus on:
- C02 emissions,
- Sustainable materials,
- Embodied energy,
- Embodied C02.
The standard sets two energy benchmarks, at:
- 15kWh/m2/yr for space heating,
- 120kWh/m2/yr to include space heating, lighting, fans, pumps, main appliances, and domestic hot water.
However, it is worth considering whether energy efficiency is really all that matters.
It’s Not Mandatory
Subscribing to the PassivHaus standard is entirely optional, and nobody is under any obligation to sign up. What is mandatory across most of the UK is compliance with the Code for Sustainable Homes (CSH), so anybody choosing to build according to the PassivHaus standard will have to meet the criteria of the Code too, as the optional does not take the place of the compulsory.
Code for Sustainable Homes:
The Code for Sustainable Homes is in the process of increasing from Level 3 (it is already at Level 4 in parts of the UK) to Level 6 in 2016. PassivHaus, as far as C02 emissions are concerned, will do better than CSH Level 3 and could just make Level 4, but it does not reach the standards of Levels 5 or 6.
It is still the case that we must develop the methods of meeting the CSH standards, and it is important to remember that PassivHaus does not take us that far.
What about Sustainability?
Sustainable building means considering the materials you use, the longevity of the building itself, and the C02 emissions it creates. It also means creating a house which will be suited to old and young alike, which can be adapted to suit the changing needs of its occupants over a number of years and generations, and that uses replaceable materials.
For a sustainable builder, energy efficiency is simply one of many factors within the whole design of the house. Energy can be sourced from a zero-carbon supply and it is not necessary to sacrifice so many other sustainability measures simply to accommodate for total energy efficiency as the PassivHaus standard does.
Your Lifestyle must Change
The energy split of a home built to the Building Regulations 2010 standards is roughly 53% space heating, 28% power, and 19% hot water. PassivHaus standards mean that it is roughly 56% power, 32% hot water, and 12% space heating.
Electricity is the main source of energy under the PassivHaus standard, bringing with it its huge C02 emissions. It is said that an energy-efficient way of living is down to 20% technology and 80% lifestyle.
PassivHaus address the issues of space heating, but hot water and power demands are ultimately ignored. Only your lifestyle will be able to affect these.
It’s More Expensive
The general agreement is that PassivHaus standards will end up increasing the costs of your build between 15-20%. The additional costs will come largely from the extra design work which will need to be carried out, but the expensiveness can be seen in every element of the build.
For example, the required triple-glazed, PassivHaus-grade window will set you back by around £350/m2, whilst a double-glazed window with a U-value of 1.4 will usually cost around £220/m2. The doors used for a PassivHaus will also cost you around 60% more than the doors you might otherwise use, and the standard also requires extreme measures to be taken to keep the house airtight.
This requirement means that special attention has to be paid to the glues, mastic, tape, and grommets you use, which would otherwise be things that we would not have to consider.
Certification also adds cost. It is a process of having the house assessed to make sure that it properly meets the standards, similar to the Code for Sustainable Homes compliance process.
PassivHaus standard certification will cost around £2,000, and testing and evidence collecting could add another £4,000 to the build costs. That is also on top of any of the mandatory CSH requirements.
Across Europe there are around 8,000 certified PassivHauses, but there are around four times as many non-certified homes built to the same standards. This is because the fuel bills have a much greater impact upon the sale value than the certificate could have.
Code Level 5 is Stricter than PassivHaus
A 200m2 house built to CSH Level 3 will need airtightness between 7m3/hr and 5m3/hr, must use low-energy lighting, solar thermal, and a gas boiler with underfloor heating. The energy consumption of the house will be around 83kWh/m2, with C02 emissions of 5.6 tonnes per year.
The same house built to the PassivHaus standard will have real energy consumption of around 140kWh/m2 (the 120kWh/m2 and the additional power usages not included in the standard).
However, the complication of the calculation is that the 120kWh/m2 refers to primary energy (meaning energy going into a power station, and not to the house). Assuming that the PassivHaus is entirely electric, the energy entering the home is just 27% of that figure, with the remaining 73% being power station and Grid losses.
What this translates to is C02 emissions of 3.9 tonnes per year – a reduction of 30%, but still not to the standards of CSH Level 5 or Zero Carbon.
What this means is that the Code for Sustainable Homes (CSH) provides stricter targets than the PassivHaus standard, and it also addresses a lot more issues regarding sustainability. PassivHaus, in relation to CSH, has quite a narrow way of looking at sustainability.
Image: Flickrtagspassivhausself buildzero carbon