Heating Options – Design Tips

Note: This article appeared originally in Green Magazine as in the image above. The text below may differ slightly from the original.

As we move into the colder months, now is the time to consider your heating options and their pros and cons.

Tip 1 – Consider the climate you live in

If you live in the southern states of Australia, you typically need space heating for six months in the year and cooling say for the three months of Summer. There is usually a blessed month and a half on either side where neither heating nor cooling are required. You live in a so-called “heating climate”. If you reside in the northern states however, the situation is very much reversed, with space heating required only in the Winter months, if needed at all, and many more months where cooling is most welcome. You live in a “cooling climate”. In this context, I’m always struck by my Victorian clients expressing more concern for Summer comfort that for Winter cosiness. I came to realise that precisely because the Victorian climate is a heating one, the vast majority of homes have been equipped with some form of heating which makes the house comfortable enough in Winter, even if it is a thermal sieve! Fewer homes have air conditioning however, which creates the general impression that Summer is more of an issue in Victoria than Winter. If there was no heating in homes however, residents would fast realise that the real focus of thermal comfort in Victoria, and in southern states generally, is insulation, insulation, and more of it!

Tip 2 – Reduce your heat load

Hydronic heating is a form of heating where warm water circulates through radiator panels fixed to walls or through pipes in the slab if the home has a concrete floor. This form of heating is the most common in Europe where the winter is much harsher than in Australia, yet a Swiss hydronic specialist once told me that boilers in his native country are about half the size of the ones installed here for hydronic heating. This is because the “heat load” of the average Australian home, or amount of heating energy that a home requires to be comfortable in a particular climate, is about twice that of Swiss homes for two reasons: homes here are typically bigger and they are not as well insulated. So before you settle on any type of heating, make sure you prepare your house to reduce heat loss, by reinforcing roof insulation, installing secondary glazing or both.   

Tip 3 – Improve your gas ducted heating

Gas ducted heating is a central form of heating and is well-suited if you want all rooms of the house to be heated quickly and equally. It is however a convective type of heating where the warm air is fan-forced, blowing dust and other allergens around, not an ideal situation health wise and certainly not one to be recommended for asthmatics. If your unit dies down and you call a heating company to replace it, don’t just trust they will sell you a high efficiency unit. All units are energy-rated, with ratings going to 1 to 6 stars so it’s easy to compare different brands and models. You might pay a bit more for the better unit but it is well worth the difference. More often than not, most rooms don’t need heating all day long and it could pay off to ask if your system can be zoned as a way to reduce heating costs. Of course, you can also close vents in room where heating is not required. 

Tip 4 – Consider hydronic heating

Hydronic heating dates back from the Romans and is the healthiest form of central heating as its radiant heat does not move the air around but allows instead a heavy material, such as a slab or a radiator panel, to radiate heat towards its environment – in much the same way that the Sun heats the Earth. Weekenders and spaces that are only used during the day are better equipped with convective heating than hydronic, as it takes a bit longer for hydronic heating to do its job. Once it’s on a regular course however, it’s a most gentle and comfortable form of heating. If you are building from scratch on a concrete slab, consider in-slab heating as the heat rises uniformly from the floor. Hydronic wall panels are a bit more costly per square metre and do not heat as uniformly but they are your only option if you have a timber floor. Hydronic heating is about 15% more efficient than ducted heating (85% versus 70% in average), reaching a record 95% efficiency with the new condensing boilers, which are now becoming the norm in Europe – the heat from waste gases is used along with new gas to heat the cool water. The fuel for boilers is typically gas although any fuel that can be used to heat water is suitable: the Romans were burning wood to do the job! Solar energy has been experimented with but such systems prove costly and not very effective – the demand for heating being the greatest when the sun is the weakest. In any case with hydronic heating, it is essential to engage professionals who specialize in the area as the installation is very different from other types of heating.

Tip 5 – What if you are remodelling or extending?

Whatever form of heating you have might be adequate if you are just remodelling the floor plan or building a small extension, say a bedroom or two and a bathroom. With larger extensions however, it is not uncommon to leave the existing heating system in place in the older section of the house and to install a new space heater in the extension – in this case, make sure you put a thermal lock, i.e. a door in between the two zones. It is mandatory for all gas wall heaters to be energy-rated so it is easy to buy an efficient one. A good option can be to get a gas log heater, as it doubles up as a pleasant focal point in an open plan living area. Energy-rating is done on a manufacturers’ voluntary basis for these at this point but you can be sure that the ones that disclose their efficiency are the better ones. Both gas wall heaters and gas log heaters use a mixture of convective and radiant heat, you will find that the fan when in use helps to project the heat deeper into the space. Do not ever consider an unflued unit, however small it is. All flues expel toxic gases to the outside indeed but the best ones are the so-called “balanced flues” where the air that makes its way inside the unit is sourced from the outside rather than from the room itself. The unbalanced flues create a negative air pressure inside which results in cool outside air entering the room, usually through door and window frames. Bad news for energy efficiency.

Tip 6 – How about wood fires?

Open fireplaces are notoriously inefficient with only 15% of the energy in the wood making its way inside the room, the rest going up the chimney – you might as well set up your favourite armchair at the top! Any enclosed insert will do a better job, the best ones being equipped with a double combustion chamber and reaching up to 70% efficiency. The largest models can heat a whole house when centrally located and fitted with heat transfer kits in the ceiling. The issue then is the large quantity of wood they use (Australians typically use slow-growing hardwoods) and the amount of greenhouse gases produced. For these reasons, I would only recommend that small wood heaters be used for smaller homes (10 squares and under) or otherwise used occasionally for ambiance but not as a main heat source.    

Tip 7 – Are there other types of heating worth considering?

Reverse-cycle air conditioning is not ideal thermally as vents are often located at ceiling level which does a good job in Summer when the cooled air drops on the floor, but not so much in Winter where the lighter warm air remains at the top of the room. Were you to locate the vents at floor level, you have the opposite problem, you just can’t win!

Electric panel heating can be useful in areas with no supply of natural gas, provided the electricity use is either generated on site or supplied by a green energy provider, using wind, hydro, solar or bio-mass. Some of the panels are made of cast iron or oil-filled and produce a radiant-like heat which is more pleasant than that panels using wires. Avoid electric slab heating altogether, it is a source of unhealthy electro-magnetic radiation.

Tip 8 – Not so common heating systems

Some companies often roof-mounted solar air panels which heat the air inside the panels and pump it inside the house. Such systems are still experimental and need to prove that their performance justifies the financial outlay. Other systems use the heat present in the roof space and pump it in the house. If your roof space is warm, your first course of action is to install substantial insulation between your ceiling joists as most of it is due to heat loss. Homes that are humid can benefit from such systems however as it allows for air flow inside the house and makes the house easier to heat in return.   

A very promising heat source is geothermal. Many hot water systems already use heat pumps which capture any heat in the outside air and pumps it into the water. A large proportion of European homes now use the heat from the ground to fuel their hydronic systems, which is a real win as it uses no fossil fuel and makes for a very comfortable living environment. Such systems will become more commonplace in Australia in the future.