The Five Core Principles of Passive House

1. Superinsulation: Protecting the Biggest Heat-Loss Areas

Think of a house as a container of warm air. The walls, roof, and floor are the largest surfaces through which heat can escape. Passive House begins by heavily insulating these large building elements so that heat loss through them is dramatically reduced.

Building regulations already require insulation, but Passive House typically requires thicker and more carefully detailed insulation layers. The difference is not simply about adding more material. It is about ensuring the insulation forms a continuous thermal envelope around the entire building, with no gaps, no weak points, and no shortcuts.

The Passive House standard has effectively calculated the optimum insulation point. Too little insulation and heat loss remains high. Too much and the additional cost begins to outweigh the energy savings. The standard sits precisely at the point where maximum benefit is achieved for minimum additional investment.

At Daniel Mihoc Construction, we understand that insulation is only as good as its installation. Continuity, detailing, and quality of workmanship are what separate a well-insulated home from a truly high-performance one.

2. High-Performance Windows and Doors

After the walls, roof, and floor, the next major source of heat loss is the openings in the building envelope, specifically windows and doors. Here the Passive House standard requires high-performance triple-glazed windows and doors with insulated frames and warm-edge spacers.

While double glazing is still common in some builds, triple glazing has become the standard for high-performance homes and is increasingly being adopted as best practice across the industry.

But Passive House goes further than simply specifying better glass. Windows are not just weak spots in the insulation. When designed correctly, they can also be assets. South-facing windows can capture solar heat during winter months while appropriate shading and design limits overheating in summer.

For this reason, Passive House considers window quality, orientation, and solar gain as part of the overall energy strategy, rather than simply meeting a minimum U-value.

Choosing cheaper glazing to save on upfront costs almost always turns out to be a false economy. The performance difference between standard and high-performance glazing lasts for the entire lifetime of the building, which could be 50, 60, or even 100 years.

3. Thermal Bridge Free Design: Eliminating Hidden Heat Leaks

Once the main building elements are well insulated, smaller weaknesses in the building envelope become much more noticeable. These are known as thermal bridges.

Thermal bridges are areas where heat can escape more easily through junctions in the structure, such as where walls meet floors, where roofs connect to walls, at balcony connections, or around window and door frames.

In a typical home built to standard regulations, these cold spots might not be immediately obvious. But when a building becomes highly insulated, thermal bridges become proportionally much more significant. They can account for a large percentage of total heat loss.

Passive House therefore requires designers to carefully model, calculate, and detail every junction so that thermal bridges are minimised or eliminated entirely.

This is also where Passive House begins to diverge most strongly from standard construction practice. In conventional building, a detail might be specified correctly in the design drawings but not always executed perfectly on site. The difference between what is designed and what is actually built is known as the performance gap.

Research comparing measured heat loss in new buildings has found that many conventionally built homes lose 30 to 50 percent more heat than predicted, with some performing up to 250 percent worse than their design calculations suggested.

In contrast, certified Passive House buildings show only a very small difference between predicted and measured performance, typically within 7 to 10 percent. This is because Passive House places strong emphasis on accurate detailing, verification, and documentation throughout the construction process.

At Daniel Mihoc Construction, we understand that precision on site matters just as much as precision on paper. Our teams are trained to deliver the level of detailing and workmanship that high-performance buildings demand.

4. Airtightness: Controlling Uncontrolled Air Leakage

One of the most significant sources of heat loss in any building is uncontrolled air leakage. Warm air escapes through small gaps, cracks, and imperfections in the building fabric while cold air enters to replace it. This happens continuously, 24 hours a day, whether you notice it or not.

Passive House requires extremely airtight construction. The airtightness target is 0.6 air changes per hour at 50 Pascals of pressure (n50). This is tested using a blower door test.

For comparison, building regulations in Ireland typically require homes to achieve airtightness levels of around 5 air changes per hour or below to meet energy targets. In Northern Ireland, new homes can legally be up to 10 air changes per hour.

In simple terms, a Passive House home is roughly 10 times more airtight than the basic regulatory limit in Northern Ireland and several times tighter than typical compliant homes in the Republic.

It is important to note that airtightness is not the same as breathability. Airtightness relates to uncontrolled air leakage through gaps and cracks. Breathability relates to how building materials manage moisture vapour. A well-designed building can be extremely airtight while still allowing moisture to move safely through the structure. The two are not in conflict.

Achieving Passive House levels of airtightness requires careful planning, quality materials, and skilled workmanship. It is not something that can be added as an afterthought. It must be designed in from day one and maintained throughout the construction process.