Energy Efficiency of Gas

Dirty Secrets – Gas in the home

Gas is connected to a considerable amount of Australian homes, used for cooking, heating and hot water. Gas has become a huge problem as building standards around the world aim to achieve draught proofed, ever tighter, and more heavily insulated building envelopes for better building performance. We’ve been slow to catch on in Australia, but there has been some small movement with the adoption of 5 and then 6 star ratings for new houses. With better quality building standards leading to tighter homes we are left with dealing with the legacy of gas, a heat-source that’s been hanging on since access to electricity became universal in the 20^th century. Unfortunately gas compromises efficiency efforts.

Firstly Energy Efficiency of Gas

Gas bills are in MJ units (megajoules) gas consumption, here is a diagram where we have converted MJ into KWh (kilowatt) so that you can see the lost energy of the combustion and distribution processes of gas appliances.

Gas involves combustion and to turn an often-used saying on its head where there’s fire there’s smoke. The smoke or combustion products of burning gas inside your house include dangerous carbon monoxide (CO), which poisons building occupants, affecting their nervous system, which more seriously in extreme cases can lead to death. The other product is carbon dioxide, which at high concentrations can lead to drowsiness and impaired cognitive function. And to get the chemical reaction (which is what burning or oxidization of fossil gas methane fundamentally is), you need oxygen. And that oxygen is being drawn from available supplies within the building envelope, competing for the air you and your family breath.

Dealing with the gas problem (without getting rid of the gas altogether) is costly, because, in order to do it, you need to compromise your building envelope seriously.

If it’s an internal gas heater then whether it is externally flued or not it can be leaking dangerous CO and CO2 into your living space, that’s due to the lack of maintenance and degradation (aging) over time of such appliances. Carbon Monoxide alarms have been mandated, but most houses are yet to install them.

To avoid problems, government regulators say that a window can be left open (which is the standard operating procedure for unflued units or units that do not have an outside air intake). But heating your house in the middle of the winter with windows open is, to say the least expensive.

Many ducted heaters are directly under or within the living space meaning they have the same dangers of CO and CO2 as wall mounted units. If your heater is outside the living space then you may think that you may not have to contend with CO or CO2. However, monitoring at ducts in older unserviced units has found CO and CO2 entering the living space via the floor outlets (ducting registers) located in each room.

Even if your heater isn’t creating CO or CO2 problems, you’ve probably still got gas cooking. It’s recommended in this case to have significant exhaust air capability, but these exhaust fan units often break down or just aren’t used by homeowners.

Then there’s the fire risk. You’re using naked flames in your kitchen, clothes made of polyester are flammable, as are wooden and plastic cooking implements and tea towels used for drying our dishes. Not to mention the risk of young, children, toddlers and baby’s getting access to stove tops. Unfortunately, countless hospital admissions are as a result of burns associated with gas cooking.

Then there’s the cost; gas appliances may seem like they cost a similar amount to air conditioner heat pumps (reverse cycle air conditioners) but in the long run, they cost significantly more.

There’s a price for service. Appliance manufacturers recommend that gas units be inspected every year or every two years while no such maintenance program is required for air conditioner heat pumps.
The daily service fee owed to the gas company starts to add up. It’s bad enough paying high daily fees for electricity but adding gas into the mix makes getting on top of household bills all the more difficult.Gas appliances are dangerous and compromise air quality, whether it’s from direct CO and CO2 due to naked flames in the space from unflued heaters or cooking or old unmaintained units that are faulty allowing infiltration from their leaky combustion chamber, with gas you are risking it. Therefore you can’t properly seal up the building to give an airtight building fabric without creating potentially lethal outcomes.
Gas appliances are dangerous and compromise air quality, whether it’s from direct CO and CO2 due to naked flames in the space from unflued heaters or cooking or old unmaintained units that are faulty allowing infiltration from their leaky combustion chamber, with gas you are risking it. Therefore you can’t properly seal up the building to give an airtight building fabric without creating potentially lethal outcomes.

The alternative is to:

Decommission your gas furnace, gas cooktop, and gas hot water service.
Engage a plastering contractor to seal up the vents around your home including corner wall vents and air conditioning and heating vents. Put insulation in place at the same time.
Choose an induction cooktop such as a unit from Ikea, Bosch, Neff or Miele.
Choose a heat-pump hot water unit such as a Sanden CO2 heat pump.
Choose an air conditioner heat pump (reverse cycle air conditioner) from Daikin, Fujitsu, Mitsubishi Heavy Industries, Mitsubishi Electric Toshiba or Samsung. A COP 5.0 or COP 6.0 reverse cycle air conditioner will cost between 1c/kWh and 6c/kWh to run, while a gas central heating system will cost about 16c/kWh to run and that’s before you take into account all the costs associated with the Swiss cheese effect from ducting vents in the floor and ceiling.

In summary, if you are considering installing or upgrading a gas appliance with another modern more efficient gas appliance, consider the following:

An air tight Building envelope is limited, which cripples the effectiveness of a well-insulated building envelope.
Servicing appliances are of utmost importance for safety.
The efficiency of Gas appliances is not what its all hyped up to be, and then throw on top of that a well-ventilated building envelope.
Electrical alternative appliances have high efficiency. If you own solar panels, you are powering them without using energy from a fossil fuel powered grid.

By Matthew Wright & John Konstantakopoulos