Electric heating systems in passive houses

Passive houses

The construction concept of passive housing has been gaining popularity over the years. This is driven by a growing awareness of the need for energy efficiency and sustainability on the one hand but also by building codes and standards that are becoming more stringent in the movement towards a climate neutral world by 2050. Especially in Europe, North-America and Asia passive house construction has gained significant momentum.

Passive houses are designed to be highly energy-efficient and create a minimal ecological footprint. By adhering to a few key principles, these buildings optimise thermal gains and minimise thermal losses, creating a comfortable indoor climate that can be maintained by the ventilation system most of the time and with minimal heating and cooling at peak times. The key characteristics include:

• Superior insulation: the walls, roof and floor of a passive house are exceptionally well insulated in order to minimise heat loss in winter and heat gain in summer. U-values are typically below 0.15 W/(m²K).
• Airtight construction: careful construction techniques and the use of a special membrane ensure that a passive house is as airtight as possible. This helps to prevent unwanted heat losses or gains through leaks in the building envelope.
• Minimal thermal bridging & high-quality windows and doors: heat can easily escape through thermal bridges or weak points in the insulation. In a passive house these are minimised through design, the use of high-performance materials and, for example, multiple-pane windows and doors with insulated frames.
• Mechanical ventilation with heat recovery (MVHR): this type of ventilation ensures a constant supply of fresh, filtered air and extracts stale air. The constant exchange ensures good air quality and reduces pollutants like dust, allergens, and CO₂. The ventilation system also recovers at least 75% of the heat from the exhaust air, which it then uses to preheat the fresh incoming air by means of a heat exchanger. This minimises the amount of additional energy needed to reach a comfortable indoor temperature.
• Passive solar gains: the windows in a passive house are strategically placed, typically on the south-facing side of the house, to maximise the use of solar energy for heating and lighting. Shading elements are also often incorporated to prevent overheating during summer.

Passive house heating

By combining superior insulation, airtight construction and minimal thermal bridging, a passive house design reduces heat loss to a minimum. The heat loss that does occur is addressed by the MVHR system which further reduces the overall heat demand with its heat recovery function and generally suffices to cover the base heat demand. According to the Passive House Institute (PHI), the founder and leading authority on the Passive House Standard, the space heating energy demand in a passive house should not exceed 15 kWh/m² of net living space per year or 10 W/m² peak demand¹.

Since the intelligent passive design allows for the energy demand to be reduced by 90% compared to conventional buildings, a passive house doesn’t need to rely on a traditional heating source such as a furnace or boiler. In fact, a conventional heating system would be oversized an inefficient here. It’s important to choose a heating system that matches the low heat requirements of a passive house.

A zoned heating approach, especially in buildings with a low heat demand at peak times, can easily be put into practice by combining electric radiators with modern or even smart heating controls.

Focused heating in a passive house

In passive houses a zoned heating approach is often adopted. The main benefit is that such a heating system allows for targeted heating in occupied rooms only. The zoned heating approach, especially in buildings with a low heat demand at peak times, can easily be put into practice by combining electric radiators with modern or even smart heating controls.

Electric heating systems allow for great flexibility, in part because electric radiators are very easy to install. You only need a power outlet and circumvent the expense and effort of installing a hydronic system. When using electric heating, you don’t need to wait for the heat to come from a central location and travel through other rooms, you can just heat individual rooms one at a time. Heat is thus only generated where and when it’s needed and there is no energy waste. Moreover, electric radiators convert every watt of electricity into heat. This is partly radiant heat, which provides a lasting warmth that slows down the cooling process and helps to reduce both energy use and running costs.

Controls also play an important role in reducing the energy consumption to a minimum. Our Yali Plus radiators, for example, have an integrated thermostat that offer precision temperature setting and integrate digital protocols which allow for custom heating and optimal connectivity. The Yali Plus radiators can easily be regulated via the user-friendly Unisenza Plus app on your smartphone or tablet. In addition, with the presence detection functionality, every radiator can be controlled separately to heat only those rooms that are occupied and the app allows for a digital visualisation of the radiators’ energy consumption so that it’s easy to monitor and adjust the energy usage whenever and wherever needed.

Customised electric heating systems

The range of electric radiators as well as different practical tools available today allow for further customisation of the heating system. On the one hand, the various designs ensure that there is an aesthetic match for any interior or personal taste. Electric radiators are generally very discrete so they blend in seamlessly. The same goes for our electric towel warmers that can be used to boost the bathroom temperature when needed and preheat or dry towels. However, for those who want to create an eye-catcher, we also offer electric designer radiators as well as the option to order your electric radiators in a colour of your choice.

On the other hand, there are various online tools available that help to ensure the electric heating system is fully tailored to the needs of the building and its occupants. The heat demand can be determined using our heat demand calculator, after which our electric product calculator helps to select the best radiator for your project in just a few clicks.

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Electric heating & net zero-carbon

One last important reason why electric heating systems are such a good match for passive houses, is the fact that they align perfectly with the ambition to reach net zero-carbon. They not only allow for optimal energy efficiency at times when extra heat is needed, but also offer the possibility to create a CO₂-free heating system, provided that the electric usage is offset with renewable energy. When the electric radiators are powered directly by solar panels in conjunction with an electric battery or a heat pump, it’s a 100% sustainable system that furthermore helps to optimise the consumption of self-generated energy that would otherwise go to the public grid at an often less favourable rate.

If you have any questions about electric heating in passive houses or would like advice on how best to integrate an electric heating system in your particular project, don’t hesitate to contact us. Our experts are happy to assist you.

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Sources:
1. https://passiv.de/en/02_informations/02_passive-house-requirements/02_passive-house-requirements.htm