Who knew air conditioning could be so complicated? We have learned a lot during this project and that includes an appreciation of HVAC – heating, ventilation, and air conditioning.
It was 2018 when our architect Brett Lowe prepared the preliminary design for Stellulata Cohousing. At that time, we had not experienced the smoke of the Black Summer bushfires. We were not aware of the ventilation issues around Covid.
Although very conscious of the future impact of climate change, we were all confident that a great passive solar design and natural cross-ventilation relying on cooler night-time temperatures would be enough to keep our homes comfortable in coming years.
With the global changes over the last six years, we decided to learn more about HVAC.
Choosing the right equipment requires an understanding of the volume and movement of air through each indoor space. The design of windows and concrete slabs and all the other aspects of a passive solar design can also influence the type and size of air conditioning equipment.
In the end, we sought professional help from Rob Withers, a mechanical engineer with MN8 Consulting.
Together with advice from Les Kulcsar and Jack Brown from Premier Air Conditioning, and Rick Stanley from Sanctuary Air, we felt confident making our choices for HVAC equipment in each unit and the common house.
Premier Air Conditioning and Heating is supplying and installing our ducted heat pump cooling and heating plus heat exchange (HEX) units and also installing ducted air filtration (including HEPA filters) supplied by Sanctuary Air. Detailed specifications are below.
Some of us had never heard of heat exchangers before. They are the core component of Heat Recovery Ventilation (HRV) systems.
Modern, well-sealed homes are great for staying warm when it is cold outside, but when it gets stuffy inside, opening a window lets cold air in. A HEX unit can use the warmth from inside air to increase the temperature of fresh air coming from outside, thereby reducing energy usage during colder months.
Conversely, when it is warm outside, the system does the reverse – cooling the air coming from outside using the lower temperature of the inside air being expelled.
In our cohousing community we work together when choosing common features. In this case though, we had different priorities. Some of us were concerned about the risk of future bushfire smoke entering our homes. Some wanted to reduce the spread of disease when people met in enclosed spaces. Some were more concerned with the efficiency of heating and cooling in a changing climate.
As a result, we have each installed a different configuration in our respective units – and yet another configuration in the common house. Depending on the relative quality and temperature of the air outside and inside, we can choose to activate one or more of the HVAC systems - air conditioning, heat exchanger and air filtration.
Guided by the Stellulata Vision and Values, we consider the ethical aspects of our choices. Did you know that nearly all air conditioning companies have some level of relationship with the arms industry?
Here are the details of our HVAC components:
Our heating and cooling are provided by ducted reverse-cycle (heat pump) systems from Mitsubishi Electric – model numbers PEFY-P125VMA / PUZ-M125VKA-A.
The energy recovery system (heat exchanger) is from Ideal Air Group – model number ESP-350AM.
Air filtration is provided by Sanctuary Air SA-1224S Air Purifier – positive and neutral pressure including VOC and HEPA filters.
We will let you know how our HVAC equipment performs during the coming months and years.