How To Build A Passive House

Warm, dry houses and long term savings are just some of the benefits to building a passive house in New Zealand, add in the numerous health and environmental benefits and it’s easy to understand why more and more people are choosing to build with passive housing concepts in mind.

What is a passive house and what are the requirements for passive housing in New Zealand? Read on to find out more.

What Is A Passive House?

The term “Passive House” refers to the process of building a comfortable healthy home with low energy needs particularly when it comes to heating and cooling.

Passive houses rely on sun and innovative design alongside careful sealing, insulation and ventilation to create a house that maintains its own temperature levels without the need for a great deal of intervention.

The first recorded passive building was erected in Darmstadt-Kranichstein, Germany. This building sported a grass roof, wooden beams, wood-chip wallpaper and wool insulation; though simple it was more energy efficient than a regular building.

In 2018 we have come far from grass roofs and primitive ventilation, perfecting the art of an energy efficient home to evolve into a warm, dry, efficient “ecosystem” that will stand the test of time.

How Do Passive Homes Work?

A passive building is a perfectly sealed, airtight system that maintains a consistently comfortable, dry environment. There are many aspects that make an optimal passive building, including the following top 5 features of a passive home.

1. Insulation

Passive houses require solid, consistent internal insulation to prevent overheating and maintain a stable temperature throughout sweltering summers and snowy winters.

Effective insulation features three distinct layers:

  • First a plastic membrane to protect against the elements;

  • Next an insulation layer;

  • And finally the airtightness layer.

Fitted in the floor, ceiling and walls with carefully sealed joins, this insulation contributes to your building becoming airtight, waterproof, and warm.

2. Triple Glazed Windows

Triple glazing might seem expensive upfront but it will save you money in the long run. Triple or double glazed windows do not conduct heat from one panel to another, so the climate on the inside is not influenced by the climate on the outside – and more panels of glass means even less heat transference.

When installing triple or double glazing on existing buildings, it is important to ensure windows and panes are properly sealed with insulation tape to stop air from seeping in through cracks.

3. Airtightness

To maintain its internal temperature passively a building must be airtight and moisture tight. Any leaks means air and/or moisture can enter from the outside and reduce the effectiveness of the climate on the inside.

An airtight home is a warm bubble, where sound and temperature is lessened from the outside, leaving the inside consistent and comfortable.

Making a building airtight is achieved by using air barriers, carefully sealing every construction joint and all service penetrations (holes for plumbing or electrical for example).

4. Heating And Cooling

Solar energy is a popular choice for passive home builders, as a renewable resource and a constant source of warmth and light the sun offers an abundance of free energy.

Buildings facing the equator will absorb the most sun during the day, and if windows face towards and away from the equator it will get full sun, all day. When there is no sun? If you’ve fitted solar panels, its battery bank will store energy that has not been used, to keep you warm on rainy days.

Because your house is losing minimal to no heat the heat produced from a fire or heater is even more effective, especially in the winter. Say goodbye to the days of being frozen solid, huddling around a heater; with a passive home your house will be dry and warm all year round.

What about during the summer months? Early models of passive houses would often get too hot during the summer, todays passive homes address this problem using external shutters, trees, vines, vertical gardens and green roofs to shade windows and keep the heat at bay.

Colour choice is important too; darker colours will absorb more light that white does, and glossy finishes refract light better than matte.

5. Ventilation

A key feature of passive housing is their sophisticated ventilation systems. Called MVHR (Mechanical Ventilation with Heat Recovery), these systems supply fresh filtered air into the building after pushing it through a central heat exchanger so the air is the same temperature as the house.

This system works both ways, simultaneously expelling air from all rooms of the house and replacing it with clean, filtered air.

7 Passive Housing Steps For Existing Homes

If your house already stands and you are interested in a refit or renovation there are steps you can take gradually to improve the climate in your house, even if your house isn’t positioned to get full sun. We have compiled a handy list of things you can do to retro-fit your home passive style, in slightly more affordable chunks.

  1. Upgrade Glazing. Upgrading to double or triple glazed windows in optimal areas is a great starting point.

  2. Install New Insulation. Upgrading and installing new insulation is one of the easiest and cost effective things to do to improve your homes comfort and warmth.

  3. Improve Airtightness. You can do some of this yourself by using expanding foam and insulation tape in places you can get to, like in your roof cavities, around windows or under the house.

  4. Think About Strategic Plantings. Consider removing branches or trees that may shade prominent north facing windows or the opposite choose to plant trees or shrubs to create shade where it is needed.

  5. Install Mechanical Ventilation. An MVHR ventilation unit with heat recovery can easily be installed in an existing home, it is best to see the experts for this one.

  6. Think About Solar Panels. Solar power units have been gaining in popularity in New Zealand over the years and are definitely worth looking in to. Retro-fit solutions are readily available so shop around for the best deals.

  7. Replace Doors And Frames. Older style door and door frames can be a big culprit in the heat loss game. All external doors including glass sliding doors need to be considered.

Thinking about building a passive home and need to know more? The friendly team at Build7 are happy to answer any questions you may have regarding the design and build of passive housing in Christchurch, and New Zealand.