Key Features of Passive House Design

Large modern house, made with a lot of wooden slats and large windows. Next to it is a tree

With the ever-increasing energy tariff prices, keeping your home warm and comfortable can become very costly, particularly in the colder months of the year. Because of this, the demand for affordable and eco-friendly solutions is rising. The purpose of Passive House Designs is to reduce the impact on the environment whilst lowering energy bills in the process.

Passive Houses were invented in the 1990s in southwest Germany, by Bo Adamson and Wolfgang Feist. And then in 1996 the Passivhaus Institute was established, to further the development and research of Passive Houses.

What is Passive House Design?

Passive House Design is an innovative design for homes that makes use of “passive” elements like sunlight, shade and ventilation to maintain internal conditions such as temperature and air quality. Passive building designs are made to be so efficient that central heating and air conditioning are barely used, if at all.

A Passive House will use significantly less energy than even a modern new build, while still keeping the home warm in the winter and cool in the summer. Passive house construction has to follow strict guidelines and parameters to meet the requirements of being a “Passive House”. Because of this, Passive Houses have to be designed from the start to ensure maximum efficiency, it is unlikely that an existing house can meet the Passive House requirements.

The 5 Key Features of Passive House Design

Passive House design is based around 5 core principles that make sure the building will be optimised for energy efficiency, whilst still keeping the living space comfortable.

High-Quality Insulation

High-quality insulation must be used at the beginning stages of construction. In a Passive House, every surface must be insulated, this includes the walls, roof and even the floors. This is to create an “envelope” of unbroken insulation, sometimes called “Super Insulation”. The desired effect from this is as much separation between the interior and exterior, therefore retaining heat in the winter and keeping rooms cool in the summer. The only gaps that are allowed in the unbroken insulation are the doors and windows – and even they’re chosen to be as energy efficient as possible.

For more information, be sure to read our article on how to improve a home’s insulation.

High-Quality Windows

Passive building design makes use of triple pane windows, also known as triple glazing. In between the panes of glass, krypton or argon gas is used, as they are poor conductors of heat. These are more energy efficient than double glazing, due to the extra pain and gas layer, and therefore retain more heat. A benefit of triple glazing is the extra noise reduction properties they have as well.

No Thermal Bridging

An important concept of Passive House Designs is to eliminate as much thermal bridging as possible. Thermal bridging is the term used for areas of a house that are less insulated, compared to the rest of the exterior – essentially these are “cold spots”. These areas ruin the integrity of the “envelope” that unbroken insulation tries to achieve, leaking out hot or cool air.

The common places that thermal bridging can occur are windows, window frames, doors and door frames. As mentioned above, this is why only the highest quality windows and doors are used, as to reduce as much heat loss as possible.

Airtight Construction

In addition to the insulation and quality doors/windows, passive building design also includes trying to make the construction as airtight as possible, to eliminate as many external drafts as possible. This helps to keep the insulation bubble intact, whilst reducing heat loss.

Can You Open Windows In A Passive House?

The simple answer is yes. The goal is to make the house as airtight as possible, so that the in-built ventilation system can provide most of the fresh air needed to the house. However, that doesn’t mean you can’t open windows. Manually opening windows is fine as long as they aren’t left open all the time.

Remember, the goal of a Passive House is to increase energy efficiency and reduce your bills, not to restrict you. Across the whole day, opening a window for 15 minutes won’t impact your energy efficiency significantly.

Mechanical Ventilation

Just because a Passive House’s design is made to be as airtight as possible, it doesn’t mean you’ll be breathing in stale air. A Passive House makes use of “mechanical ventilation” which supplies the house with fresh air. A Heat Recovery Ventilator (HRV) is installed, which will continuously extract old and moist air from the house, while also supplying fresh air back in.

To make this system even more energy efficient, a HRV will use any heat from the air it extracts out of the house, and use it to pre-warm the air being supplied to the house from outside. This system allows for a steady supply of fresh and warm air in the colder months, while supplying cooler air in the warmer months.

An easy way to think about this is that the system will use the current temperature of the house’s interior, to condition the new fresh air being introduced. An additional benefit of this system is that all air brought into the house is also filtered, which helps for people with allergies like hay fever.

What Are The Benefits of Passive House Design?

A Lower Environmental Impact

Passive Houses are designed to use as little energy as possible, while still achieving a comfortable living environment. As such, they have much lower carbon emissions than standard houses, due to less energy being used to heat the house.

Save Money on Bills

One of the biggest benefits to a Passive House Design is the impact it has on your energy bills. Passive Houses can save you upwards of 75% on your energy usage, even when compared to new builds.

Better Air Quality

The use of mechanical ventilation means that any stale, moist air is extracted from the house, and filtered fresh air is brought in. Because of this, mould is less likely to grow and there will be less particulate matter from outside, in your home. For more tips on improving air quality, read our improving air quality in the home guide.

Comfortable Room Temperature All Year Round

Due to the Passive House’s design and construction, your rooms will be at comfortable temperatures no matter the time of year. That means warm and cosy rooms in the winter, and cooler rooms in the summer.

PLANNING PASSIVE HOUSE CONSTRUCTION

The one downside to Passive Houses is that they have to be made from the ground up, starting at the design phase. This is because they have to consider the 5 core principles mentioned above, but also elements like the positioning of the house in relation to the sun.

Easy to Implement Passive House Elements

By far the easiest design features of a Passive House to implement, which will create a noticeable improvement, is installing better quality windows.

For many homes, especially older buildings, swapping out your windows for more energy-efficient ones will drastically reduce heat loss and cold spots. This will keep your rooms warmer for longer, and therefore cost less in energy bills to keep warm.

Here at Dakea, we supply high-quality triple pane roof windows, with options for both PVC and wooden frames. So, no matter your preference, you can install high-quality windows and start saving money, while reducing your impact on the environment.

Frequently Asked Questions

Are Passive Houses Expensive to Build?

Passive House designs typically cost between 5 – 15% more than a conventional new build. However, the long-term benefits and money you save per year can result in the whole-life cost of the house being 2 – 5% lower than a standard house. And as energy prices rise, this difference will only get bigger.

Do Passive Houses Overheat?

Excessive solar heat gain is the most common cause of overheat risks in a Passive House. However, the design of the house is made to combat this, and should be easily managed. In the case of extremely abnormal heat for your area, opening windows at night can help to speed up the purging of excess heat.

Do Passive Houses Require Maintenance?

Like with any home, a Passive House will require maintenance. This will mostly be in the form of filter replacements for the mechanical ventilation system, which will need changing 1 to 2 times per year. Because many Passive Houses don’t use central heating systems, they aren’t susceptible to expensive plumbing repairs

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The Key Features of Passive House Design