Split System Heating and Cooling

As I mentioned in my previous post, we have now created a heating and cooling zone in our main room by rebuilding a wall and fitting a door. If we’re inside during the day we spend most of our time either in this room or in our study, so converting our heating in this space to zero emissions sources will put a significant dent in the emissions generated in our home.

The heating unit that we decided to go with is a heat pump, alternatively known as a split system or a reverse cycle air conditioner. Switching to this technology is ranked #42 on Project Drawdown. In traditional heating, you can convert one unit of energy into one unit of heat. With a heat pump you aren’t creating heat so much as moving it from one place to another, which means the heat output can be significantly higher than the energy input. This is the same concept used in refrigeration.

Heat pump heating and coolingEfficiency varied considerably across the units that we looked at. We decided to go with the most efficient unit that we could afford, and were quite surprised by how many units cost more with lower efficiency. We went with a 5-star Mitsubishi unit that we bought at Bunnings. Heating is rated at 3.2kW output for 0.65kW input, and cooling is rated at 2.5kW for 0.51kW input. Our unit is considered too small for the space, but we wanted to size it against our solar panels instead of our room size.

Our hope is that installing this unit will mean that we no longer run the gas ducted heating at all in a best case scenario, or only on the coldest days in a worst case scenario. In either case, we expect our heating bills to be slashed. By switching to electricity we generate ourselves instead of using natural gas, the unit will potentially pay for itself in fuel savings before it is out of warranty.

If you’re playing along at home…

…how much could you increase the energy efficiency of your home by switching to a heat pump for heating and cooling? If you already have a system for cooling, how much gas could you save by also using it to heat? Please share your experience in the comments below.

Create Heating and Cooling Zones

At some point in the past, our house has undergone a series of renovations to combine three small rooms into open plan living. While we really enjoy the bright spaciousness of our main room, having it open to the hallway meant that we couldn’t shut off this part of the house to separate out heating and cooling zones.

The benefit of separate heating and cooling zones is that you only have to heat or cool part of your house instead of the entire building. By only adjusting the temperature in the part of the house that you are using, you can save a significant amount of money on heating and cooling costs, and the energy use that goes with it.

Door with glass panelsWe were able to separate our main living area from the hallway by rebuilding the wall that had originally separated the two spaces. This was the wall where the cornice had fallen down, leaving a gaping hole in the ceiling. It was an opportunity to create something better than what had been there before, so we widened the doorway and chose a door with glass panels to retain the natural light in our hallway.

The whole project cost us approximately $600 to complete, and it has made such a difference to the temperature in the house. On colder nights we shut the door, and the heat generated in the kitchen is enough to keep the room warm. During a recent hot spell we kept the door shut, and it stopped heat from flowing through our large, north facing windows into the cooler bedrooms. This passive difference isn’t huge, at only one or two degrees, but already it has been the difference between running the gas ducted heating system and not running it.

If you’re playing along at home…

…are you able to create zones in your home to reduce the amount of energy required to heat and cool the space? Please share in the comments below the approach you took and the results you achieved.

Roof Vents

As I write this today, it is currently 40.3°C outside, with a projected top of 42°C. For those unfamiliar with Australian slang, this is what we like to refer to as a scorcher. A hot wind is pounding the house, and I’m praying that the ice blocks I put in the chickens’ water this morning keeps them alive until the promised cool change sweeps in.

Welcome to summer in Melbourne, global warming style.

Despite the heat outside, inside the house is still relatively cool, and it is after 1pm. We have a new air conditioner, and I haven’t felt the need to turn it on. While I have no scientific data to back this up, I think the change is due to the roof vents we installed a few weeks ago.

Roof ventThe vents are a simple piece of technology, and because we bought a cheap version ($69 each) they are entirely wind powered. The basic idea is that the heat from the sun is warming the cavity between our tiled roof and the internal ceiling. As the space up there warms, heat starts penetrating our ceiling insulation and warms up the rooms below. By installing these roof vents, the heat trapped in the roof space is able to rise out of the roof and escape, rather than being forced into the area below.

A house the size of ours requires three of these vents, but we only installed two because we don’t want to block any roof space that might be needed for our future photovoltaic system. They work better on a house like ours because we have a pale green roof instead of the more popular black roofs that are sweeping the city, which means some of the heat is reflected instead of being absorbed.

In winter we might end up with the problem that we’re extracting heat that we would prefer to keep in the house. The nice thing about this installation is that it only took about an hour to set everything up, and we still have the missing roof tiles stacked out of the way. If they aren’t working for us during the cooler part of the year, we can simply take them down again and store them until next summer.

If you’re playing along at home…

… are you able to install roof vents in your home to keep it cool during the summer months? If you have already done this, please share in the comments below how well they worked for you.