Passive House Design with Smartglass

The Passive House design goals of sustainability, affordability and comfort coincide with the capabilities of smartglass. This facilitates ultra energy-efficient buildings and a faster transition to global Net Zero.

In a Nutshell

Passive House is a building standard that aims for energy-efficient, healthy, comfortable and affordable homes and offices, based on the following principles:-

  • Super-insulated building envelopes for thermal efficiency and airtightness
  • Fresh-air ventilation with heat and moisture recovery
  • High-performance glazing that maximises daylighting and passive solar heating, goals which smartglass can contribute positively towards

Although the title indicates otherwise, passive house design principles are applicable to any property type, including residential homes, commercial offices, schools, churches, factories and skyscrapers.

Passive House certification is available for buildings, building components and professionals and enforces strict quality control in the planning and execution phase, both for new builds and retrofits.

The Passive House movement aims to achieve an 80-90% reduction in space heating and cooling costs, over and above that required by national building codes.

We will see in this article how smartglass technologies can positively impact the philosophy, objectives and key performance metrics of a Passive House.

What is Passive House Design?

The diagram below shows the key elements of a Passive House:-

  • Passive solar shading in warmer months
  • Passive solar gains in cooler months
  • Continuous super-insulated building envelope
  • High-performance windows and doors
  • Heat recovery systems via a heat exchanger
  • Internal gains from people and equipment, such as cookers, stoves, computers
  • Renewable energy on the roof or walls (e.g. photovoltaic building claddings)

passive house diagram

Let’s now break down the key principles of a Passive House:

Super-Insulation

Passive houses aim to ‘super-insulate’ the building envelope. So much so that incident solar energy, cooking stoves and even body heat from occupants is sufficient to maintain a comfortable temperature.

This ‘Super-Insulation’ involves a double layer for the flooring, walls and roof. This is often implemented by high-performance ecological materials such as sheep’s wool and cellulose.

Airtightness

The Passive house design standard requires careful sealing of doors, windows, electrical outlets, sill plates, piping and recessed lights.

This is expensive in cost and time but avoids heat losses and patchy cold spots. 

The end result is a more comfortable and healthy building which suffers less draughts and condensation, avoiding mould growth and respiratory health issues.

No Thermal Bridges

Thermal bridges are basically areas of least resistance to thermal flow. Examples include window frames with aluminium edge spacers, still prevalent in the glazing industry, but gradually getting replaced by warm edge spacers.

Thermal bridges can negate the great work done in insulating and sealing the building envelope.

Ventilation

In a highly-insulated closed space, we must have proper ventilation to ensure a healthy air supply.

The ventilation in Passive Houses serves the dual purpose of bringing in fresh air that also carries warmth. 

This avoids recirculated air, exterior noise and draughts.

For this to work, the building must be insulated and airtight (preferably no more than 0.6 air exchanges per hour) and with a heating/cooling load no greater than 10 W/m² to ensure compliance.

Typically, Heat Recovery Ventilators (HRVs) or Energy Recovery Ventilators (ERVs) are used to transfer heat and moisture, providing an energy-efficient and healthy interior.

All this implies an increase in building costs of between 5-10%, but also gives us lower operational costs in heating or cooling the building, since so little energy is being lost through the building skin.

Ultra-Efficient Glazing

Smartglass technologies, when built into Insulated Glazing Units (IGUs), can contribute notably to Passive House design goals. This is especially true when the IGU comprises low-emissivity coatings, warm edge spacers and argon air fills.

This typically gives exceptionally low U-Values, typically 0.85 to 0.45 W/(m²·K).

The diagram below shows dual-pane and triple-pane IGUs (insulated glass units) with an argon gas fill, indicating how the interior climate is maintained by rejecting exterior heat and cold and reflecting back interior warmth, whilst also maximising daylighting.

insulating double-pane and triple-pane windows

Thermal insulation and daylighting with double-pane and triple-pane windows

Passive House glazing is normally specified as triple-pane, and insulating frame materials can also minimise the thermal conduction losses.

Smartglass technologies have their ‘secret sauce’ in their interior layers, which are capable of tinting on-demand. This minimises glare, reduce solar heat and rejects ultraviolet which can damage interior furnishings. 

Smartglass layers also improve daylighting, visual comfort and privacy for building occupants.

The next stage in development will see low-voltage (and low-power) technologies such as electrochromic or electrophoretic smartglass powered directly by transparent photovoltaic layers inside the smartglass itself.

There are a couple of exciting startups working on this currently, including P-Layer, a spin-off from the CNRS (the French National Centre for Scientific Research), who are researching into a dynamic and autonomous photovoltaic glass technology.

This will be a game changer for Passive House installations, removing the need for an external power source (including the cables), and improving the sustainability of smartglass.

Glazing Orientation

There is a strong sense of responsibility on the part of Passive House architects to design facades which maximise daylight and also maximise shading.

This is a seemingly impossible task, given the variety of climates worldwide.

However, this assumes we are using static glass, which cannot change its optical properties.

Switchable smartglass can overcome this handicap, with a solution that is adaptable to a wider variety of global climates.

Outlook

Whether we are talking about the design of Passive Houses or Net Zero Buildings, the end goal is the same: to minimise the impact of humans on the environment.

There is no more wasteful species on the planet than us.

It is time we used our (supposedly) larger brains to construct dwellings that learn from other species: notably how they inhabit this world so sustainably.

We believe the answer lies in combining ultra-efficient Passive House design techniques with dynamic smartglass technologies.

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