6 Ways Passive House fills the gaps in our Building Code

I often say that our New Zealand Building Code creates the worst preforming building legally able to be built. To clarify this, when the minimums are used as a design guide and compliance is the goal, not a quality healthy space for its occupants, the result definitely leaves a lot to be desired. There is a perception amongst New Zealanders that a Code Compliant New Build home is a healthy one. But Code Compliant simply means legally it can be built.

Below I cover the 6 ways in which Passive House creates a better home than a Code Compliant one, by addressing the important design issues that affect every day New Zealanders home quality of life.

1. Warm for Winters and Cool for Summer

 Our New Zealand Building Code (NZBC) relies only on insulation values to design comfort and healthy temperatures into any design. The problem with this, is that health and comfort lie far focusing on heat loss of a buildings element. The design has to work well to create health and comfort with ventilation and a quality thermal envelope. The solution to addressing comfort and healthy indoor temperatures is to energy model a design and get data around performance so it can be predicted, rather than rely on prescribed values and just assume it. Passive House requires Energy Modeling and sets strict targets that any design needs to meet, for indoor all year round temperatures and humidity levels.

2. Constant Fresh Air

 We all know we need fresh air with oxygen to breathe and old stale air is not good for our health. We have this mindset that we can just open windows and magically the quality of the inside air of our homes will improve to healthy levels. We need to replace the entire volume of air in our homes every 3 and a half hours, so does our opening windows really make that happen? Our Building Code relies only on natural ventilation to achieve this, that is opening windows and doors. A study monitoring the Carbon Dioxide levels in New Homes in Auckland over a year revealed that our windows only are effective in achieving healthy ventilation rates 12% of the year. That means we have to do something else for the rest of the 88% of the year to have healthy oxygen levels in our indoor air. Our Building Code doesn’t give any requirement for this 88% of the year and just ignores that lack of performance with opening windows. The Passive House Standard requires mechanical ventilation to ensure the Carbon dioxide levels are constantly kept down to healthy levels.

3. Predicted Energy Bills not Assumed performance

1.    Our Building Code only relies on insulation to set performance criteria around energy use in our homes. But our power bills don’t just cover space heating, they are affected by hot water heating, cooking, extract systems and general everyday energy use. Insulation doesn’t make energy; it can just lower the cost of space heating in winter. Passive House requires energy Modeling so that the energy use of the home can be predicted, and it covers energy use beyond just space heating. There is a strict maximum energy use cap, so the design has to provide a warm, healthy comfortable home with power bills lower than the average New Zealand Home currently has.

4. Quieter Spaces

Remember the saying, a “quite place in the country?” Noise is an unwanted consequence of living in cities or more densely populated areas, and excessive noise can affect our mental sanity and physical health by interrupting our sleep. Our New Zealand Building Code only has acoustic requirements around the building envelope in apartments or terrace houses as noise is more easily transferred in those types of homes, but noise is an issue in all homes. One of the silent benefits of Passive House, is the quiet nature of the interior. The reason Passive Houses are quiet, is that the windows seal shut really well, there are no air leaks and therefor sound leaks in the building and a ventilation unit means windows don’t have to be open to get fresh air.

 5. No Condensation

1.  Condensation is a very real issue for many New Zealanders. Our Building Code relies on intermittent kitchen rangehoods, and bathroom extracts to dehumidify our interior environments and reduce condensation. These are reliant on human behaviour and aren’t 100% effective. We impact the humidity of a space because we breathe out about 3-4 litres of water a day, we have other activities in our spaces apart from cooking and showering that affect the interior humidity. Condensation happens in our home in a process that is very like the water cycle we all learnt at school. If we don’t address the surface temperatures, humidity and ventilation rates in our homes, we create rain on the inside of our windows, or even worse, in places we cannot see, like in wall cavities. Passive House requires calculations and design that stops any condensation both on internal surfaces such as windows and prevents any water from developing in the wall, roof and floor cavities.

6. No Overheating in summer.

1.  Here in New Zealand, we are very concerned about heating our homes and talking insulation, but cold homes in winter is not the only problem we are facing. Our homes get really hot in summer. Our Building Code doesn’t have any requirements to address overheating in summer. As we hear about global warming, its fair to say that our summers have become warmer over time. Designing for both winter and summer (and spring and autumn in between) is important to creating a liveable healthy space all year round. Passive House requires the energy Modeling to quantify the free solar gains we want from the sun in the colder months to heat our homes for free, It also requires calculation of excessive solar gains prevented by shading, window design and orientation to stop overheating above 20 degrees Celsius in the warmer months, so you don’t have to install an air conditioning system or use fans.

During my Passive House training I began to see just how poor our building code really is for creating healthy comfortable affordable homes for everyday people. I hope this blog gives you something to think about when considering your new build or renovation project. Most people want to get it right and make their project a good one.

To learn more about the Passive House Standard, download the free guide.

Passive House Designer