Heating your home and choosing options while renovation/building
So it's getting a tad cooler heading into the next few months so I thought it would be good to talk about heating options in a home when renovating or building….there are so many options and it can all get a bit confusing.
So the basic heating for dummies low down seems to be – Insulate the roof, walls and floor, seal off draughts, let in winter sun and draw curtains at night.
If you can zone your existing or new home and only heat the rooms you are using and use doors to prevent heat escaping into unused rooms.
The two main types of heating are radiant and convective.
Radiant heaters predominantly heat people and objects by direct radiation of heat. Convective heaters warm and circulate the air in a room.
Other forms of heating, such as heated floors, also heat by conduction through direct contact.
Different forms of heating are best in different circumstances:
- In larger rooms with high ceilings, a combination of radiant and convective heating is best.
- In small rooms, space convective heating is effective.
- In larger draughty rooms or bathrooms, radiant heating works best.
So basically heaters produce air movement as hot air rises and then falls as it cools.
All heaters produce air movement as the hot air rises from the heater to the ceiling. Air is cooled when in it gets in contact with windows and poorly insulated walls and ceilings. The cooled air then falls and is drawn back along the floor to the heater.
Sitting in draughts created by air movement can make you feel much colder. Minimise draughts from windows with the use of heavy curtains with snug pelmets or other ways of preventing air flow through gaps at the top and sides of window coverings to stop heat loss. And you can position your furniture to deflect or avoid draughts.
Gas heaters and efficient reverse cycle air conditioners (or heat pumps) produce only one-third the greenhouse gas emissions of standard electric heaters. The most efficient 5–6 star reverse cycle units actually produce less than one-fifth of the emissions of conventional electric heaters.
You will find Gas heaters and heat pumps have Energy Rating Labels to help you choose the most efficient model.
Wood can be an excellent fuel because it is a renewable resource if sustainably harvested. (you may want to consider that wood fired heaters in urban areas can cause air pollution and they have associated emissions with transporting firewood to urban areas.
About 10% of homes use wood for heating - but the wood is often obtained from unsustainable sources so to be a good kiwi try and use only sustainably harvested wood to avoid the environmental impact.
And of course don’t use treated timbers, which give off toxic pollutants when burned.
Burn wood only in airtight, slow combustion heaters. They have the highest energy efficiency of wood heaters, and use the least wood and cost the least to run.
Central vs space heating
Choosing whether to heat your whole house or only the required rooms or spaces has a major influence on the greenhouse impact of your home. In a house with central heating, the greenhouse emissions and costs of running it are usually higher than running efficient space heating.
Central heating can often heat a whole house whether individual rooms are occupied or not. Space heaters usually only heat the room or area where the heater is installed.
For an energy efficient house, use space heating only in rooms that require heating or use a zoned central heater to reduce running costs.
Heat only the rooms that are being used.
Central heating usually uses more energy than space heating as more of the house tends to be heated. This, of course, is relevant to the size of your home.
However, an energy efficient house with central heating may use less energy than an inefficient house with space heating.
Several types of central heating are available.
In ducted systems, hot air is circulated through the roof or underfloor ducts, supplying convective heat. Gas or a reverse cycle air conditioner can be the heat source.
Design the system so that the extent of the area heated can be controlled and include zoning to allow for shutting off heating to unoccupied areas.
Insulate ducts and make sure all joints are well sealed.
Floor outlets are often better than ceiling outlets for heating, as warm air naturally rises and they deliver heat to where it is most needed.
Hydronic systems circulate hot water or coolant through radiator panels in rooms, supplying a mix of convective and radiant heat.
Hydronic systems are usually gas-fired but can be heated by a wood fired heater, solar system or heat pump. Solar systems can use gas or wood heating as a back-up.
Each panel or room should have its own control.
Low water content systems are best as they reduce energy use. Ensure water circulation pipes are well insulated, and smart controls manage pump usage. Higher running costs are usually caused by unnecessary water circulation or poor pipe insulation.
Exterior walls behind panels must also be insulated to prevent heat loss to the outside. Use wall cavity insulation or a layer of installed reflective foil on the internal wall behind the panel. Ideally, all exterior walls should be insulated to maximise comfort from the heating system, especially in a new home or major renovation.
In-slab floor heating
Insulate slab edges, and ideally the entire slab, from the ground to minimise heat loss. Insulate walls from the slab to reduce heat loss.
Electric in-slab heating generally has the highest greenhouse gas emissions of any heating system. As electricity prices have increased, in-slab heating costs have also increased.
The best in-floor system for minimising greenhouse gas emissions is a hydronic system using one of the following:
solar with gas back-up
efficient slow combustion wood heater that heats water (wetback)
geothermal or water-sourced heat pumps.
These devices heat a smaller area — one or perhaps two rooms — and come in a wide range of types.
Electric portable heaters
Electric portable heaters can be cheap to buy but are expensive to run and sometimes ineffective.
Radiant heaters, such as bar heaters, are good for bathrooms as they give almost instant heat direct to your body and do not directly heat air. Less warm air is lost than with other heater types and they heat your body even when an exhaust fan is used. No thermostat is fitted so use a timer or switch. Turn off radiant heaters when leaving the room for any length of time.
Fan heaters heat the air and provide convective heat. Larger upright models are more effective. They can warm smaller rooms quickly and some have thermostats to help reduce energy use.
Convector heaters heat the air, which then rises naturally. They are not recommended for rooms with high ceilings or poor insulation levels or where there is a high ventilation rate.
Oil-filled column heaters supply a mix of convective and radiant heat but are slow to respond. Some have thermostats, timers and fans.
Electric systems may produce high greenhouse gas emissions — up to six times as much as an efficient gas heater. However, using a small electric heater for local heating may be cheaper and have lower emissions than heating a much larger area with gas.
Electric fixed heaters
Reverse cycle air conditioning (or heat pumps) provides convective heat and is the most energy efficient electric heater. The most efficient 5–6-star units may be cheaper to run and generate lower greenhouse gas emissions than gas heaters.
Wall panel convectors use peak electricity and are expensive to run, like portable electric heaters.
Gas portable heaters
Unflued portable heaters can provide either convective or radiant heat and run on natural gas or LPG.
Adequate ventilation is needed to maintain good air quality, which can significantly reduce efficiency.
Unflued gas heaters often create condensation problems — usually at the opposite (coolest) end of the house. Take care to ensure they don’t lead to mould growth.
Gas fixed heaters
Wall units and floor consoles can provide convective and/or radiant heat, and usually have fans to circulate hot air. Most are flued, requiring less ventilation and producing fewer condensation problems.
Gas fixed heaters usually have fans to circulate hot air.
Some fixed gas heaters use fan-powered flues or ‘balanced’ flues: they draw in outdoor air, heat it, then return it outdoors. Other gas heaters use indoor air for combustion and rely on flues to remove the waste gases from the house. In well-sealed houses, there is a risk that exhaust gases can be drawn back into the house through exhaust fans, such as kitchen range hoods or bathroom exhaust fans, creating health and safety risks.
Gas decorative appliances
Some log or flame effect fires are actually decorative appliances and are not designed to provide space heating.
If you have a decorative appliance, use it only occasionally.
Gas decorative appliances use more gas than a space heater but don’t heat areas effectively.
Wood and other solid fuels
Open fireplaces give radiant heat but are highly inefficient. Up to 90% of the heat energy goes up the chimney and large volumes of cold air are drawn into the room to replace it, creating cold draughts or removing heated air from nearby spaces where other heating is running. They are the least efficient wood heating method and produce the highest levels of air pollution. Open fires are better at producing ambience than heat.
Heat shifters consist of a fan and ducting and cost little to run and install. They move air from warm areas to cooler areas.
Heat shifters redistribute warm air downwards.
Heat shifters redistribute warm air that collects upstairs back downstairs, or warm air from the ceiling back down to floor level.
They can also supply heat for rooms that only require low levels of heating, such as bedrooms.
So lots of information to take in really….
So many things to consider and it is really personal to what you feel is the priority for heating your home and of course what you can afford.
A lot of the time it comes down to forking out money initially to save money on running costs down the track but if you can’t afford this then do some research into what will suit your needs best.
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