Some houses feel different the moment you walk in. The air, the y acoustics, something you register before you can name it. That is part of what draws people to build differently.
Step into a Passive House during a summer heatwave, and the temperature holds steady and comfortable, without air conditioning working flat out to get there. In the depth of winter, the building does the same thing in reverse: warm in every room, no draughts, no cold spots, no radiator roaring to keep up. It also saves money, because the cheapest energy is the energy you never need; the building itself is doing the hard work. That's the whole point of the standard.
So how does a building get there? Let's start with what Passive House really means, then walk through how EcoCocon's wall system measures up to it.
What Is the Passive House Standard?
Passive House (Passivhaus in the original German) isn't just a certification you slap on afterwards - it's a performance standard developed by physicist Dr Wolfgang Feist, whose first demonstration building went up in Darmstadt, Germany, in 1991. Instead of adding renewable energy systems to offset a leaky, poorly insulated building, Passive House asks a simpler question: what if the building itself barely needed heating or cooling in the first place?
Five key principles get a building there, and they work together rather than in isolation. Most of them are passive in the truest sense: they do not need power to do their job, which is where the name comes from.
1) Optimised solar orientation with high-performance windows for winter solar gains and summer shading. Passive solar design lets the low winter sun stream in through the windows for useful heat, then keeps those same windows from overheating the space once summer's high sun comes around.
2) A superinsulated envelope: high-performance insulation with windows and doors, usually triple-glazed, works both ways: it holds heat in through winter and keeps it out through summer.
3) No thermal bridges: Thermal-bridge-free design takes care of the junctions, like foundations, balconies and floor slabs, where heat usually sneaks through.
4) Airtightness: seals the gaps and joints that would otherwise cause more heat loss than most people realise, and protects the building fabric in the long run – though airtight doesn't mean sealed shut – it can be vapour-permeable.
5) Heat recovery ventilation (HRV): Mechanical ventilation with heat recovery brings in fresh air while keeping most of the heat that would otherwise be lost through simple window ventilation - and no, despite the myth, you're not sealed in: you can still open a window whenever you need or want to.
Because these principles are interconnected planning happens up front, in a PHPP (passive house planning package) model that simulates the building's performance and comfort before a design is finished. The key target numbers are 15kWh/m2a for heating or cooling demand (or 10W/m2 for heating load). Those numbers aren't just theoretical - they have been proven, project after project, to match real-world energy use. The only unpredictable factor is human behaviour.
The result is a building that stays within a comfortable temperature all year-round, using much less energy than a conventional building built to basic building regulations requirements.
Climate Change Resilience
Passive House most probably wasn't designed with climate change in mind – but it turns out to be well suited for it. As heatwaves and cold snaps get more extreme, the same solar design and superinsulated, airtight envelope has quietly picked up a second job: resilience. A Passive House holds a liveable temperature far longer through a heatwave or power cut than a conventional building does.
The Passive House standard's key targets
The Passive House Institute sets clear, testable targets: space heating or cooling demand under 15 kWh/m² of treated floor area a year (or a peak load of 10 W/m²); airtightness of n50 ≤ 0.6 air changes per hour at 50 Pa, verified by a blower-door test; and total primary energy capped at 120 kWh/m²a under the classic criteria. Combined with heat-recovery ventilation, the remaining energy demand drops so low that a mini-heat pump paired with photovoltaic panels can comfortably cover it. A compact all-in-one unit can also cover heating, cooling, hot water and ventilation.
It pays to plan with the PHPP tool from scratch. Not because the concept is complicated, but because it helps to optimise and brings high-quality, detailed projects.
Where EcoCocon fits in
The EcoCocon straw wall system is listed as a certified construction system in the Passive House Institute's own component database, and it directly answers most of the standard's core requirements.
Superinsulation
Straw insulation is built into the panel itself, and flexible enough to scale to the project: panels come in thicknesses of between 300mm and 400mm, with an extra layer of wood-fibre board added wherever a design needs to push performance further. A typical 400 mm build-up, finished with interior clay plaster and 60mm exterior wood-fibre board, achieves a U-value of around 0.13 W/m²K — within the Passive House range, and better than most building codes require. It is not just the U-value that matters though. High specific heat capacity of dense straw means that it takes much longer time for the heat to move through the wall compared with more lightweight types of insulation, further improving winter and summer performance.
Airtightness
Airtightness is where most Passive House projects run into trouble on site. The EcoCocon system handles it with a membrane fixed to the outside of the panel, easy to apply and out of the way of other trades. It is vapour-permeable, like a breathable jacket: draughts stay out, moisture gets out, and the wall stays dry.
For larger buildings, whole wall elements can be pre-assembled off-site with the airtight layer already built in, then sealed up on site once in place.
Thermal Bridging
Easy to eliminate, thanks to a wide range of pre-solved EcoCocon construction details and the flexibility to install windows and doors in almost any position within the panel.
Passive House at scale
Hundreds of single-family homes have been built with EcoCocon to near-Passive-House performance. The one formally certified example is Old Holloway in Herefordshire, winner of the small projects category at the UK Passivhaus Awards. The same principles hold at larger scales. The standard gets easier to hit as buildings grow, not harder. A larger building has less exterior wall for every square metre of floor inside it, so there is simply less surface to lose heat through. EcoCocon has already delivered a wide range of larger projects across very different sectors, most of them applying Passive House principles at least in part. Blower-door results have been excellent throughout. Full certification is the investor's call, not a limit of the wall system. EcoCocon's own production hall is built to Passive House performance levels
Why it all adds up
Put together, a Passive House delivers a high-quality indoor environment, protection against winter cold and summer overheating, and construction quality that gets measured rather than assumed. EcoCocon brings two things the standard cannot. A wall that stores carbon instead of releasing it. And a route to the standard that is already worked out. Passive House projects go smoothest when the wall system is decided early. Talk to us while the drawings are still open.