In this new article we are going to talk about the Passivhaus standard and the considerations that we must take into account to comply with it when building, for example, our passive house. 

That is why if you are interested in everything related to energy efficiency and the use of the environment for the construction of homes and buildings, you should not miss this content.

What is the Passivhaus standard?

Passivhaus is an energy-efficient building standard that was developed in Germany in the early 1990s by professors Bo Adamson and Wolfgang Feist.

In addition to energy efficiency, buildings constructed according to the Passivhaus standard must have an added value in terms of indoor comfort conditions.

This comfort is provided by aspects such as air quality (due to the absence of unwanted infiltrations and controlled ventilation), sound insulation and constant temperature throughout the year and independent of inclement weather.

Today we have fully monitored Passivhaus buildings with proven results, which confirm the effectiveness of this construction model both in terms of efficiency and energy savings and in terms of improving health and quality of life.

What is Passivhaus based on and how does it work?

Passivhaus is a building standard primarily aimed at reducing energy consumption in residential buildings.

Typical calculations show energy savings of up to 90% compared to older buildings and more than 75% for the latest standard constructions.

And to arrive at these numbers, a number of requirements and energy consumption calculations have been included, which are listed below:

Thermal insulation

Good insulation of the building envelope ensures good performance in both winter and summer. 

The thickness of the insulation will vary depending on the climatic zone where the house is located, until an optimum value is reached that meets the requirements demanded.

Eliminating thermal bridges

One of the causes of not achieving good insulation is the creation of thermal bridges at the contact points of the external wall materials, which are a direct source of energy losses and water vapour condensation points.

An example of thermal bridges are windows, the weakest element of external walls. 

To avoid these losses, thermal bridging is achieved by avoiding contact between the exterior and interior surfaces by adding materials such as polyamide profiles, which have very low conductivity and help to reduce energy losses.

High-performance windows and doors

Doors and windows are the weakest elements of the envelope of the house and that is why we must have high performance elements that allow a high level of airtightness and thermal insulation.

Heating demand

It is the most important indicator as it is directly influenced by the thermal losses and gains of the dwelling.

Losses are caused by thermal bridges, cracks, air infiltration, poor quality insulation, etc.., 

On the other hand, gains are given by sunlight, orientation, heat exchangers or HRV and internal heat sources such as appliances, light bulbs or people themselves.

In this way the energy demand is limited to 15 kWh/m2 and the house can be heated with great savings thanks to a simple ventilation and heat adjustment system.

For hot climates, the cooling demand is taken into account and excessive overheating is avoided, which would reduce the comfort of the house for people.

Tightness and Blower Door test

The Blower Door test was first used in Sweden in 1977 to measure the density of the exterior walls of a building.

The test can be performed on all types of buildings, both old and new, and basically the test measures the amount of air escaping from the building. 

The better the quality of the building envelope, the lower the air density. This makes the Blower Door test an excellent tool for measuring the quality of a building.

The result for the Passivhaus standard must be less than 0.6 air changes per hour measured at a pressure of 50 Pascals and with the natural air inlets sealed.

What is Passivhaus certification?

First of all, it should be pointed out that the Passivhaus standard does not require any specific building material or building system and does not “prescribe” anyone, but sets limits that all buildings must comply with.

The criteria to be met are summarised as follows:

• Heat demand <15 kWh/m² per year.
• Cooling demand <15 kWh/m² per year.
• Primary energy demand <120 kWh/m² year.
• Blower door pressure test at 50 Pa shall be <0.6 air changes per hour.

These criteria may vary slightly depending on the region, for example in the Mediterranean, the maximum primary energy consumption for heating, cooling, domestic hot water (DHW) and electricity is 60 kWh/m² per year.

How much does it cost to build a Passivhaus house?

Nowadays the construction of a Passivhaus house involves an extra cost of 5% on average (up to 15% in premium houses) which is mainly due to the materials used and the more detailed work by the architect when choosing the orientation, design and materials.

But despite this initial cost overrun, there are three important factors that make a Passivhaus house worthwhile and more profitable in the long run: savings, maintenance and appreciation in value.

Costs amortisation and savings

The cost overrun that we can count on is amortised in the medium term thanks to the fact that, for example, a 120 m2 house spends around 1,500 euros a year on heating and a Passivhaus only 150 euros, which is a saving of 90%.

Example:

Cost of a normal house = 200.000€ Average annual expenditure = 1.500€.
Cost of a Passivhaus house = 210.000€ Average annual expenditure = 150€.

Amortisation time = 10.000 / (1.500 – 150) = 7.4 years

Maintenance

The maintenance costs are almost zero because on the one hand the owner is protected against market fluctuations and on the other hand the wear and tear of the cooling and heating elements is lower because they are used much less.

Revaluation

Finally, it should be noted that a Passivhaus-certified house has an estimated revaluation of 20% over time, which means a significant benefit over the cost in the event of selling it.

Value in a possible sale = 210.000€ x 20% = 252.000 (Gain of 42.000€)

Final conclusion

The Passivhaus standard is a way of constructing buildings and homes that is expected to grow in the coming years, because as we can see, despite the supposed initial cost overrun, it allows energy savings in the long term.

And we are not just talking about savings for our own pockets, but also energy savings that will have a positive impact on our planet, slowing down climate change and CO2 emissions.