Whether it is a Passivhaus/ Passive House, a Nearly Zero Energy Building (NZEB) or a low energy building, based on passive principles, air tightness is critical; it is as important as good insulation. As such close attention should be paid to the ventilation strategy. In almost all cases MVHR is the right choice, as in air tight dwellings, natural ventilation without frequent/ all night window opening is not delivering the necessary air quality.
It is also important to choose a high performance MVHR system that not just has a good performance on paper, but also in real life and will retain its efficiency over its life-time. It also should not drop its the heat recovery rate in the coldest time of the year.
that you shouldn’t feel restricted to open windows in a Passivhaus or any other dwelling with MVHR. When you want to open them, feel free to do so. However if you don’t want to, you will still have good air quality within.
that about half of Europe’s Passivhaus dwellings have a central heating system. It is a myth that Passivhaus means a dwelling without central heating, let alone a dwelling without any space heating.
If you intend to design a house without central heating, please contact us in the early design stages. For such projects typically a warm water based or electrical post heater is installed into the supply leg of the MVHR system. We are happy to assist you in the process, as we have accompanied a large number of similar projects right from the start of Passivhaus in the Scotland.
Certain building types lend themselves more to space heating via air, e.g. double storey dwellings with a rectangular and smallish footprint. Sometimes it is better to have a central heating system at least for part of the dwelling.
We find the biggest danger with Passive dwellings in the UK is over-confidence and assumptions on part of the design and specification team, as well a lack of understanding and training on part of the installation force. Proper, concluded thermal calculations with the PHPP design tool before any work on site, experience, accuracy and a quality minded installation team, that is ‘on board’ of the methodology, make all the difference and ensure a successful project.