Heating, Cooling and Ventilation in a Passive House

We get lots of questions regarding the heating and cooling systems that we are specifying these days. It is a very complex topic, as the whole house needs to be considered for both heating and cooling requirements in our climate.

Before we discuss the pros and cons of the systems on the market, firstly I think it is important to understand the type of building that we are designing and building. First and foremost, our approach is “efficiency first”. By this, I mean that we are designing a building that is highly insulated and airtight and relies very little on heating and cooling to make the house comfortable.

Air quality is one of our highest priorities: it is essential for healthy occupants. To achieve this we create an environment that is separate from external influences by insulating the shell and eliminating gaps and drafts. Then, for air quality control, we introduce a Mechanical Heat Recovery Ventilation system (MHRV) that brings in fresh filtered air, free from pollutants, and extracts stale air. It also contributes to moisture control and balanced temperature throughout the home. Without going into detail, these modern automated systems are intelligent pieces of engineering, running on very little energy. The heat recovery element ensures that minimal energy (temperature) is lost in the exchange of air.

A question that we often come across is around whether the windows and doors be opened up in a Passive House: the answer is a resounding yes! We are blessed to live in a climate, where for much of the year, we don’t really need to rely too heavily on heating and cooling, and we can open up the house, enjoying a great connection to the outdoors. This still applies if you have a Passive House! The only difference is, when winter hits and all the doors and windows stay closed, you can rest assured that your MHRV will kick in and keep your indoor environment healthy, free from mould, and prevent CO2 build up. For most of the year, heating and cooling is simply not required.

Although Passive House originated from Germany, a much colder climate than ours, the formula still works in our backyard. It’s all about maintaining a comfortable indoor temperature. When it’s -15 degrees outside it is far more challenging to maintain a comfortable indoor temperature, which is why it is actually much easier to achieve passive house criteria here! However, at peak periods of winter and summer, we will still need to balance the scales to maintain an ideal indoor temperature between 20-25°C. We don’t need a complete cooling system for summer and a complete heating system for winter; it would be an over investment. Today's air conditioners are extremely efficient and can cater to both heating and cooling needs, hence the term reverse-cycle.

In summary when it comes to heating and cooling; the system itself only has a small role to play, mainly dealing with those peak periods of summer and winter, and possibly some crispy spring and autumn mornings. Don’t waste your money in over engineering your system when the house you build simply doesn’t need it. Put your money into building performance and air quality, and you’ll be repaid with an extremely comfortable and healthy home.