Passive House Standard and What It Asks of a Home

Heating bills keep climbing, and many people planning a new home or a deep renovation hear the same two words from an architect: Passive House. The phrase gets used loosely, often to mean "well insulated," which leaves clients unsure what they are actually paying for.

The passive house standard is something much more specific. It is a set of measured performance targets, developed in Germany in the early 1990s, that a building either meets or does not. This guide explains the numbers, the five design principles behind them, what it costs, and where I think the standard is misunderstood.

Where the passive house standard came from

The idea came out of research by the physicist Wolfgang Feist and the Swedish engineer Bo Adamson. In 1991 the first test project, a row of four terraced homes in Darmstadt-Kranichstein, was completed and monitored. Its residents used roughly 90 percent less heating energy than a typical German home of the time. Feist went on to found the Passive House Institute in Darmstadt in 1996, which still sets and certifies the standard.

The word "passive" is a little misleading. These buildings still have ventilation fans and usually a small heater. The point is that the building fabric does most of the work, so the active systems can be tiny.

The numbers a building must hit

For the Classic certification level, a new building has to meet these core targets, checked by a certifier using the institute's design software, PHPP:

To make that heating figure concrete: a 120 square metre house at 15 kWh per square metre uses about 1,800 kWh a year for space heating. That is roughly what a single 2 kW electric heater would use running about 900 hours, spread over an entire winter.

Existing buildings can be certified to a slightly relaxed retrofit version called EnerPHit, which allows 25 kWh per square metre per year and 1.0 air changes per hour, because old walls and foundations limit what is possible.

The five principles behind the passive house standard

Designers usually describe the approach in five parts. None of them is exotic on its own; the discipline is in doing all five properly together.

1. Continuous insulation

Walls, roof and floor wrap the building in a thick, unbroken layer. In a cool climate like the UK or northern Germany, wall U-values are typically around 0.10 to 0.15 W per square metre Kelvin, which often means 250 to 300 mm of insulation.

2. No thermal bridges

Thermal bridges are spots where heat leaks through a gap in the insulation, such as a concrete balcony slab running straight through a wall or a steel lintel over a window. Passive house detailing designs these out, for example by using thermally broken balcony connectors.

3. Airtightness

The 0.6 target means the whole building leaks less than a typical home by a factor of five or more. Builders achieve it with a carefully taped membrane or a plaster layer, then prove it with a blower door test, often twice: once mid-build when leaks can still be fixed, and once at completion.

4. High-performance windows

Windows are usually triple-glazed with insulated frames, with an installed U-value around 0.8 W per square metre Kelvin. They are also positioned within the insulation layer rather than at the outer face of the wall.

5. Ventilation with heat recovery

Because the building is so airtight, fresh air comes from a mechanical ventilation unit with heat recovery, known as MVHR. Stale air from kitchens and bathrooms passes through a heat exchanger that warms incoming fresh air, with an efficiency of at least 75 percent.

What it costs and what you get back

Cost premiums vary by country and by how experienced the team is. Early projects in the UK often ran 15 to 20 percent above a standard build. Teams that have done several now report premiums in the range of 5 to 10 percent, and some housing associations have built at close to normal cost once they standardised their details.

The return is not only on bills. Residents usually describe the comfort first: no cold walls, no draughts near windows, even temperatures from room to room, and quiet interiors because the same airtight shell blocks street noise.

If you are weighing up a project, it is worth reading our notes on why building orientation decides a home's comfort, because orientation is one of the cheapest decisions that helps you meet the standard.

The counter-take: more south glass is not the answer

A common piece of advice, repeated in many older green building guides, is to face a passive house south and fill that side with glass to capture free solar heat. It sounds logical, and the very first passive houses did lean on it.

In practice, I think it causes more problems than it solves. Large south-facing glazing gains heat on sunny spring and autumn days when you do not need it, and on summer afternoons it can push rooms well over 25 degrees C. Glass is also the weakest part of the envelope even when triple-glazed, so it loses heat on every winter night.

Many recent certified homes use modest window areas, often 15 to 25 percent of the south wall, combined with external shading. As summers warm, overheating has become the more serious design risk in many climates, and moderate glazing with good shading handles it better than big glass.

The other myth worth retiring is that you cannot open the windows. You can. The ventilation system means you do not need to for fresh air, but nothing stops you throwing them open on a mild day.

Is it right for your project?

The standard suits most building types, from single homes to schools and apartment blocks. It is especially rewarding in compact forms, because a simple box has less wall area per square metre of floor than a sprawling plan. A terrace or apartment block is easier to certify than a detached house with lots of corners.

It also pairs well with a low-carbon approach to materials. Insulation and triple glazing carry their own environmental cost, so it helps to think about cutting embodied carbon in buildings early while choosing your wall build-up.

Frequently asked questions

What is the main requirement of the passive house standard?

The headline requirement is a space heating demand of no more than 15 kWh per square metre per year, or a peak heating load of 10 W per square metre. Buildings must also pass an airtightness test of 0.6 air changes per hour at 50 Pascals.

Do passive houses need a heating system?

Most need only a very small one. Some use a heater coil in the ventilation unit, while others have a compact heat pump or a single radiator. Body heat, cooking and appliances cover a large share of the remaining demand.

Can an old house meet the passive house standard?

Older homes are usually certified under EnerPHit, the retrofit version, which allows 25 kWh per square metre per year. Getting there typically means external or internal wall insulation, new windows, airtightness work and ventilation with heat recovery.