Our Guide to Passivhaus
9th Jun, 2022
There’s a lot of buzz around how the construction industry can act on climate change – and rightly so. Installing electric vehicle charging points and adopting renewable energy technologies come to mind. Another strategy which is gaining traction is building to the Passivhaus standard.
Passivhaus is an energy performance-based standard, using a whole-building approach. A passive home creates comfortable indoor temperatures by optimising heat gains and minimising losses.
There are five elements which make a passive home –
- No thermal bridging
- Superior windows
- Mechanical ventilation with heat recovery
- Quality insulation
- Airtight construction
Let’s look at these in more detail.
No thermal bridging
Heat inside a building will escape where it’s colder; when it’s colder outside, areas of the house with the lowest insulation values act as pathways for the transition. These are known as thermal bridges. Thermal bridges can lead to moisture and condensation. A Passivhaus building is designed to be thermal bridge-free.
You can reduce energy demand by 90% compared to other buildings by making the most of thermal gains.
Passive solar heating takes place via high-performance windows and doors. Triple glazed elements, filled with gasses like argon, allow for poor heat transfer. Solar gains can be minimised in the warmer months if designed with overhangs externally, concrete floors to absorb heat, and careful placement of deciduous trees (which offer shade in the summer).
Optimising their position on the building allows for heat to be harvested from natural light in the winter. Think southern-facing elements which face the sun.
Mechanical ventilation with heat recovery
With the airtight nature of passive homes, ventilation systems are installed to remove pollutants and clean the air. A heat recovery ventilation system continually pushes stale air out, and fresh air in.
Paired with energy recovery ventilators, air being circulated out of the building can pass over coils to balance the temperature of fresh air entering the building. Especially beneficial in winter, they can draw also on moisture to improve humidity.
The walls of a passive home are between six and twelve inches thick, where extra insulation can be accommodated to minimise heat transfer. Multiple layers of insulation cover every surface including roof, walls, slabs and footing. So many materials, like plywood sheathing and sheep’s wool, are procured sustainably too.
Given the impact insulation can have on internal space, it’s not uncommon to see passive homes with basement floors.
In harmony with the other elements, constructing an airtight envelope minimises heat loss and thermal bridging. That means no holes or spaces for leaks.
Because of its desirable certification mark, Passivhaus is often regarded as a brand – and having a hefty price-tag to deliver. However, the initial upfront cost promises long-term cuts to operational costs. Even if not every element of the standard is met, net-zero is still achievable – if combined with other strategies, like solar panels.
With the advent of Part L and its carbon emission requirements, the likelihood of including Passivhaus standards in upcoming designs is very realistic.
We are experienced in working closely with Passivhaus designers and consultants to ensure the requirements are incorporated into the building services design. Our recent schemes include:
- University of Exeter Multi-Faith Centre
- Vaughan Road – a Passivhaus, modern apartment scheme
- Clifton Hill – a £12m mixed housing development
- Bodmin Road – an award-winning, £10.4m development
- Newcastle Central Mosque – A new £8m mosque and community building, achieving predicted energy usage of 20%
If you would like a chat about meeting Passivhaus standards, drop Tim Young a line at: firstname.lastname@example.org