What Are Passive House Windows

What Are Passive House Windows
Passive House windows in a sustainable building mock up

You may have heard the term “PassivHaus” when searching for your new windows, but do you know what it really means? Trying to figure out the science behind it can be quite daunting, so we’ve broken it down here for you in our simple guide. 

“Passivhaus buildings provide a high level of occupant comfort while using very little energy for heating and cooling.” Passive House Trust

PassivHaus is a term applied to the design of buildings with specific occupant comfort and energy standards. Originating from the PassivHaus Institute in Germany, it aims to provide a high level of comfort whilst using very little energy for heating and cooling.

These buildings are ecological, comfortable, energy efficient and affordable, all wrapped into one. The purpose of this housing is to remain affordable whilst bringing the future of ecological efficiency into your home. This is achieved through use of proven technologies and build standards and quality. 

How does the Passive House System work? 

If you’ve ever lived in (or visited) an older house, you’ll have experienced the draughts that inevitably blow through the building. Due to older construction techniques, ageing materials and general wear and tear, older houses tend not to be the most energy efficient buildings. This isn’t news. 

Buildings designed to PassivHaus standards are required to be as air tight as possible with the necessary flow of air controlled and with appropriate heating and cooling to maintain the comfortable indoor air quality. 

Of course, a feature then had to be developed to allow proper ventilation. Passive ventilation occurs through assigned vents via a ground heat exchanger. This mechanism allows for fresh air to be heated and pumped into the building, as well as extracting out the waste heat from the exhaust system. Ventilating the building in this controlled manner equates in very little energy wastage. 

New advances also allow the system in passive houses to factor in heat created by the inhabitants and appliances within. More ambient heat is retained as a result of no draughts and better insulation, further reducing energy used to generate heat.

Diagram of how a passive house works

The Passive House System is environmentally friendly

As the world moves forward with new ways of being environmentally friendly, so does our housing. Science is progressing, and that means our homes are progressing too. Passive housing aims to have as little impact on the environment as possible, whilst also providing exceptional comfort levels within the homes. Environmentally friendly and sustainable energy sources are  used in passive houses to limit their impact on global warming to as little as feasible.

These sources include:

  • Ambient
  • Solar
  • Heat exchange

Passive Houses offer 90% energy saving

Passive houses are designed to maintain a constant temperature – unlike those older houses that regularly need the heat replacing. Due to this design, they are super easy to keep warm/cool depending on where you reside, which allows for outstanding energy saving. Passive houses actually use 90% less energy than the majority of typical buildings. Whilst passive houses have a comparable 75% energy saving on new builds, factoring in the costs still makes this an excellent saving. Being a passive house homeowner means less stress over rising energy costs as they only use 10% of the energy needed to run a typical house.

Passive house windows savings diagram

Is a Passive House expensive to build?

A passive house is an investment, as extensive energy savings means that money is redeemed within a few years. Although the initial cost is higher than that of a typical house, this is to be expected due to the high quality of materials used, as well as the extra components and elaborate construction methods. 

With the purchase of a passive house, there should really be no need for a heating system. The concept for the houses is structured around the belief that little heat should be needed in order to make the homes comfortable. That being said, in some climates this would not be possible, but even in central Europe houses would be able to thrive without a conventional heating system. Therefore, whilst the house would cost more to purchase with the required ventilation system, the energy savings from the more advanced system would be well worth the price. Not to mention the benefits of passive house construction on the environment and reduced effects on global warming.

Can Passive House be retro fitted?

Absolutely! A PassivHaus does not have to be built from the ground up – it can be applied to an established building. As PassivHaus is a concept and not a brand, the particular construction components can be adapted to any building in order for it to be classed as a “passive house”.

EnerPHit is a slightly relaxed standard for retrofit projects that shares the same principles, but where the existing structure and Conservation needs mean that full PassivHaus cannot be met.

Passive House Window Glazing

The U Value is a measurement of heat transfer [expressed in W/m2K], where the lower the U value the better, so windows used in the design and construction must have a Low U Value. Typical standard double glazed units achieve a value of around 2.5, reducing to 1.9 for Gas Filled units. This can be further reduced by the use of triple glazing to 0.7. However, the extra glass (+50%) and edge seals (+100%) needed for a triple glazed unit should be factored into to its’ environmental credentials.

The latest technology Vacuum Insulated Glass under the brand name of LandVac provides an exceptional U value of better than 0.5W/m2K., in a double glazed unit. Whilst Triple Glazing has a typical thickness of 38mm, Vacuum Insulated Glazing is only 8.3mm thick. Making it suitable for both new build and retro-fit applications