Are There Any Lessons We Can Take Away From Homeowner Feedback?

Survey Responses from Australian High-Performance and Energy-Efficient Homeowners

Heat Recovery Ventilation Systems and Energy Recovery Ventilation Systems are still relatively uncommon in houses in Australia. We are only beginning to get used to them. These systems do make some noise, and this is audible in a very quiet home like a high-performance, energy-efficient home, certified Passivhaus, or even Code Plus home.

A couple of homeowners commented about the background hum that is usually audible in the living areas and bathrooms. This is particularly true when the HRV/ERV is in boost mode for increased extraction during showers and cooking etc. Sound is also emitted at the other end of the system where the heat or energy exchange core and fan are located. The general advice is to install this unit away from living areas in a laundry or storage area. A homeowner commented that they would put it into its own cabinet if they were doing it again.

These systems move air around the home, but it is quite a slow movement. This was an issue for a couple of homeowners. In a home with high ceilings and cathedral ceilings, the owner reported feeling that the airflow was not adequate. Another felt that there was not enough airflow in their childrens' bedrooms in summer, meaning that they needed to sleep with bedroom doors open. A homeowner commented that they thought the HRV would move enough air in and out of the bedrooms to distribute conditioned air for an even temperature in all rooms. Like me, this homeowner had to retrofit ceiling fans to help, which has fixed the problem. I'll say it, a pretty easy trap to fall into!

For more information about MVHR, see this article from Renew Magazine by Joel Seagren, MVHR Engineer at Fantech.

A couple of owners in different parts of the country raised an interesting point about the difference between the temperatures that their homes were generally maintaining with minimal heating and cooling, and what they find is their naturally comfortable temperature.

In a home in metropolitan Melbourne, the winter temperature in the morning is usually around 19 degrees (2-3 deg. outside). The owner reports that they are able to feel air being moved by the HRV while sitting near the vents, or a doorway, and that this air is too cool for them to comfortably study or work. As part of their build, they installed a small hydronic heating system with panels in the bedrooms and living areas. They have found that they need to turn it on to raise the temperature to 22.5 degrees, which is the temperature that they find is right for them. The sun then begins to warm the house and the hydronic system switches itself off. The homeowner said that he wasn't expecting to be needing heating, but that he is happy with the overall performance of his new home. This home achieved 0.59 ACH on blower door test.

There is a small double height stairwell in my home where I can feel cooler air moving upstairs on a cloudy winter's day. This can be a bit uncomfortable if you are lightly dressed and standing at the bottom of the steps when the indoor temperature drops to around 18 degrees. We rely heavily on solar gain to bring our home up to 20-21 degrees during the day, which we find comfortable. When this is not available, we use heated towel rails, or RCAC to bump the temperature up a couple of degrees.

In a home in the subtropical Northern Rivers of NSW, daytime summer temperatures are very stable at around 26 degrees. According to the owner, outdoor temperatures are generally around 30 degrees and rarely drop below 20 degrees overnight. Lower temperatures do occur, but this is usually in the early hours of the morning just before daybreak. The internal temperature of this home slowly cycles between 21.3 degrees in winter and 26 degrees in summer. For the owner, this is a comfortable daytime summer temperature, but it is too warm for sleeping at night. Night purging is not possible because of outdoor humidity and the relatively high outdoor evening temperature. The owner says that the windows stay "firmly shut" between November and March, and they were aware that they would need active cooling and dehumidification during summer.

The original design was for a small split system RCAC system in the main living area. However, the owner found that this was not enough to cool the home to a comfortable overnight temperature and achieve humidity control. In attempting to improve this, they installed ceiling fans, increased external shading, made adjustments to the HRV and added an additional small split system RCAC to one side of the home. They were eventually able to achieve their goal of coolth and dehumidification being distributed evenly throughout the home by replacing the cooling with an 8kW multi head split system and 2kW heads in 4 of the rooms. This enables them to cool 2 rooms at a time and rotate cooling through the rooms, thereby achieving a temperature and humidity level that is comfortable for them.

There was a similar comment about the cooling and dehumidification capacity of a home in the Riverina region of NSW, where the homeowner felt it was undersized for the home and their needs to manage the indoor climate while solar power was available.

And an owner in metropolitan Sydney wrote about realising in hindsight that a ducted air-conditioning system and independent dehumidifier may have better suited their project.

The owner of a home in tropical Far North Queensland tells me that their 7kW ducted A/C system does a great job of cooling the home, and that they only need it for about 60 days a year. The house is pleasant most of the time, and they only turn it on when the temperature outside rises to about 36 degrees. He is considering a second, small system for one end of the home for visitors and particularly hot days. Humidity is extracted by both the ERV and a dehumidifier. The ERV manages occupants' showers and low humidity days. However, once the humidity gets above 55%, the dehumidifier will automatically kick in. On high humidity days when it is raining and above 80%, it can pull as much as 30 litres of water out of the house per day! The region has high humidity for about 80% of the year.

Disclaimer: These are the opinions of homeowners. These homes are high-performance, energy-efficient homes. Some of them are PHI certified and some are not. The uncertified homes were never intended for certification and the performance described above is unrelated to certification of these homes. All homeowners are happy with the overall performance their homes. See the full disclaimer in the footer of this website for further information.