The principles of constructing a Passive House – or a Passivehaus, as originally named – were first developed in Germany by the Passivehaus Insitutute and work hand-in-hand with achieving environmentally friendly buildings.
Passive houses must reach a strict criteria of standards which largely cover ventilation, insulation and energy use.
What classes as a passive house?
Not just any ‘green’ building can achieve the certification of a passive house. All applicants are rigorously assessed and the checking procedure runs through the whole process, from initial designs to the finished article. This ensures every construction stage is up to scratch and meets the criteria.
Achieving the Passivhaus Standard in the UK typically involves:
- Accurate design modelling using the Passive House Planning Package
- Very high levels of insulation
- Extremely high performance, energy efficient windows – often triple glazed
- Airtight building fabric
- A mechanical ventilation system with highly efficient heat recovery
The UK Passive House Organisation is in charge of certifying UK builds as a passive house. Because of such high standards, it is often best to apply principles from the very start of the design process, before a single brick has been laid. Though the Passivehaus Institute does have a certification recognising retrofitting work.
How does a passive house work?
The original aim of Passivehaus was, and is, to deliver net-zero-ready buildings that provide a constant stream of fresh air and a steady temperature inside without the need for active heating or cooling. This offers an energy-efficient property that is optimised for the comfort and wellbeing of its inhabitants.
Following the standards outlined above, this is done through insulating the house to incredibly high standards. The property is enveloped in specifically chosen, insulating materials and constructed to ensure there are no interruptions or thermal bridges. Thermal bridges occur when a material conducts heat better than its neighbour, creating a weak spot where heat can leak in and out of the house. Windows, doors and their frames are the most common, which is why the passive house standards stipulate exact specifications.
Creating a highly insulated home might sound airless, but this is where ventilation comes in. A ventilation system is used to keep inside air fresh whilst constantly removing excess heat and moisture. Heat recovered from air expelled is used to heat-up the air coming into the building, thus maintaining a constant temperature.
A small backup heater is often present for actively heating hot water or for colder months. But on the whole, boilers and heating systems are not required for passive houses.
The advantages of passive houses
Thanks to their lack of central heating, a more conscious approach to materials and specific standards of energy consumption, passive houses present several advantages.
- Lower energy bills thanks to elimination of gas boiler and stipulations of internal energy usage e.g. from appliances
- Less carbon emissions
- Ambient temperatures all year round
- Clean air without excess moisture (preventing damp and mould)
- Great overall air quality
- Low maintenance costs overall (no broken boilers!)
- Lower noise levels thanks to insulation
- More wall space, as you don’t need any radiators
- Higher-worth homes
The disadvantages of passive houses
Whilst the paybacks are obvious, the main disadvantage is that a passive home incurs a higher initial investment to build. An extensive design process, higher quality construction fabrics, higher specifications of doors and windows, triple glazing, and skilled engineers and laborers are required to achieve the standards set.
Not so much a disadvantage as a note: there is also a maximum amount of energy that occupants are allowed to use for additional heating and domestic appliances. This is calculated relative to the size of the building. Whilst you are unlikely to go over the amount set, this rule shows that the passive house is a lifestyle as much as it is a building concept.
Let’s talk about passive housing
The difference between passive houses and ‘normal’ builds is approximately 70% reduction in energy use, a fantastic opportunity to reduce energy bills and our carbon footprint. But the construction phase is more intensive than usual, meaning you need skilled engineers that know exactly how to streamline the process.
At GLD Consulting, we have a team of building services engineers who specialise in building your property to your exacting standards.
Talk to us about passive housing here.
