Are you planning on building a new home in the near future? Chances are you’ve probably heard of the passive house NZ movement, or maybe even the German certification that originated the concept; Passivhaus.
But what is a passive home, and how does it compare to a green home, i.e. a house built following sustainable guidelines? Do you have to pick one or the other if you want to build ethically? We break down the details below.
What is a Passive House?
To start with, let’s talk about what a passive house is, and the general aims of passive home projects.
By and large, a passive house is one that meets a certain set of strict energy efficiency criteria. The confusion around the term is at least partially down to the wide variety in standards around the world. For example, average temperatures in the UK are lower than they are here, so the local authoritative organisations there have different requirements.
It’s generally very unlikely that any older homes are going to meet these standards, so passive homes tend to be new and built within the last few years, typically.
The passive home’s basic concept involves cutting emissions by reducing a home’s reliance on heating and cooling systems. Via high-quality insulation, cutting-edge membrane seals, and some clever techniques, the ambient temperature of the home can be comfortably maintained with minimal power usage. Some power is needed to operate heat-recovery ventilation, but this is a fraction of the energy required to heat or cool the average NZ home.
The ingenuity behind a passive home is fairly fascinating. That is, by capturing the heat generated by appliances, e.g. fridges, lighting, ovens, as well as the heat generated by occupants, the air-tight design of a passive home can almost entirely avoid heat loss. What’s more, the heated air inside the home is used to heat cold air ventilating into the home, maintaining a constant ambient temperature.
What is a Green Home?
While a green home is different from a passive home, they are related. Passive homes need to meet strict benchmarks to qualify for certification, with the main focus being on the thermal envelope and performance. A green home in NZ can be looked at as a more holistic approach. This includes a focus on the thermal envelope, while bringing in to account a further a range of criteria not included in Passive House certification. The Homestar certification is a NZ based tool that can be used to certify green homes.
There are many additional features that a green home, built to achieve a Homestar rating, may have that a passive home does not require. A green home is any house that’s (1) built sustainably and (2) constructed to help occupants live sustainably.
Sustainable building involves using sustainably sourced construction materials that can be traced (such as Forest Stewardship Council- FSC- certified timber), and recycled materials where possible. Additional measures on-site include Site Waste Minimisation plans to reduce waste in the first place (such as prevention of over-ordering of materials) and recycling targets for waste. Environmental Management Plans, ensures measures are put in place to minimise air pollution (such as using low VOC paints), noise pollution and contamination of the surrounding environment during the building process.
Homestar certified Green homes will also require a high level of insulation, efficient water usage, sustainable waste water management and access to key amenities, such as access to public transport. Some green homes use renewable power sources, such as solar power, but they aren’t required to do so.
To summarise, a green home can achieve passive house certification, if the home adheres to the strict thermal efficiency criteria. Conversely, a passive home can achieve a green home certification (such as Homestar) if further steps are put in place to achieve the range of factors above.
Passive or Green: Which one is right for you?
In essence, building with both of these concepts in mind can help you create a design that’s able to leave as small a carbon footprint as possible. Green homes source reliable resources, and passive homes work to cut emissions through usage, leading to long term energy savings.
The team here at Craft Homes has a sustainable building philosophy, which takes both of these ideas into account. To find out more, reach out and get in contact with us today, and one of our friendly team will be able to help answer your questions.
Looking to build, and don’t want it to cost the earth? Give us a call today!
Toby and Cat Tilsley