Bottled Gas – Cooking

Photo from wickipedia

Many people building a new house like cooking on gas, but may find that their area doesn’t have a mains supply.

The question then becomes “Should you go for bottled gas, or go all electric?”

Energy Cost

To compare energy costs you first need to understand how much energy there is in bottled gas.

  • 45kg bottle of gas holds the equivalent of 611 kw hours
  • 9kg bottle of gas holds the equivalent of 115 kw hours

Price

Current prices Victoria July 2015 are:

  • 45kg is $114.00 – Equivalent to $0.18 per kw hour
  • 9kg (Swap and Go)  is $23.00 – Equivalent to $0.20 per kw hour

For the 45 kg bottles you would need to add rental for 2 bottles at around $40 each/year

With the 9kg bottles you need to consider the purchase price for  the initial bottle, plus a couple of dollars for fuel every couple of months to  swap bottles.

Efficiency

There is no star rating for cooktops, but I did find the following, typical, comparison figures on the Consumer Energy Center Website:

  • Standard Gas Burner – 55%
  • Standard Electric Hotplate – 65%
  • Induction Element – 90%

The reason for the difference is that the standard cook tops radiate a sizable amount of heat into the air; while the induction element makes the bottom of the pan the heating element, putting more heat into the food.

Convenience

I much prefer cooking on gas to using a standard electric hotplate. (In case you are wondering I probably cook 75% of family meals and we rarely get takeaway food) . . .However people do tell me that induction element are pretty close to the  ease of gas.

One issue with induction elements is they don’t work with aluminium or copper pans, just Stainless Steel and Cast Iron, so it might be time for some new pans!

Overall

If I was building in an area without mains gas I think I would go for an Induction Cooktop for the following reasons:

  • Cost – When the  additional costs are added to the base cost and with the lower efficiency the final cost is around around $0.35-$0.40.  Electricity is going to be cheaper especially if you have got solar power.
  • Simplicity – One bill for all fuel use and no need to bother about changing bottles.

 

Strange Wood Heater Location

This photograph shows an attractive antique looking wood heater which I found on hearth.com. . . . but its location looks very odd to me:

  • As it has been placed in front of varnished timber it has had to be placed well away from the corner meaning it’s taking a lot of space away from the room.
  • A large proportion of the radiant heat from the stove, and the stove pipe, will be lost through those windows behind it.
  • Any attempt to reduce the heat loss through those windows by curtains will increase the fire risk.

You need to remember that wood heater efficiency isn’t just about the stove. . . . it’s also about the location.

 

 

Air Conditioning – Ducted, or Separate Units?

Guest post by Hubert Dwight

Choosing between split systems and ducted air conditioning systems is no easy task.

We understand that nagging voice in the back of your head that keeps asking “Will we go for a split systems or go for it and purchase a ducted air con system?”

Weighing up the advantages and disadvantages of both air conditioning systems is not easy and often ends up in people going for the builders standard option.

Here is some information on the pros and their cons of the alternatives.

Ducted System

Characteristics of  ducted systems are:

  • Neater with small vents, typically set in ceiling like the one on the right;
  • Centrally controllable;
  • Can have multiple zones;
  • Only one unit to maintain;
  • Air flows are less obvious in larger rooms due to several outlets;
  • You can direct the system capacity to a restricted number of zones;
  • Adjusting ceiling vents is difficult: you will need a step ladder;
  • To be effective need open doors between outlet vents, and return air inlet.
  • For larger homes you may need to Upgrade to 3 phase power;

It can be worthwhile getting a unit with variable fan speeds. . . . . . instead of ‘Low-Med-High’ other wise you may find the fan being too noisy when you are only using a a single zone.

Separate Units

System characteristics are:

  • If you only cool key rooms it can be cheaper to install and run (have units in every room running constantly and it will be more expensive);
  • Individual temperature control for each unit;
  • Ceiling space isn’t filled with ducting;
  • Individual temperature control for each unit;
  • Failure less off an issue as doors can be left open to get some cooling effect from ajacent cooled rooms;
  • Can close doors between ‘zones’ without affecting performance;
  • More intrusive appearance, and air flow is more obvious.

Combination

Can’t decide perhaps a combination system might suit you?

For instance  have ducted heating and cooling in Kitchen, Meals, Family and Theatre rooms; Split systems in the bedrooms.

Running a split system to heat or cool the bedroom is more energy efficient than running a big ducted unit.

Being able to individually control the temperatures in each bedroom is handy as children won’t want their rooms heated or cooled when you do.

Its useful you can set a split system heater in the bedroom to run for an hour or so at bedroom before shutting off.

 

Passiv Haus

What is a Passiv Haus  (Passive House)?

Well as you might have guessed the term originates in Germany, and relates to a method of achieving more sustainable performance (and lower Energy Bills)

It’s a technique which doesn’t rely on good orientation, high thermal mass and natural cross flow ventilation to provide comfortable conditions with low energy use.

The house on the right, built in Castlemaine by Carbon-Lite, is said to be the first Passiv Haus built in Australia

Some of the key Passiv Haus characteristics are:

High Levels of Thermal Insulation

All  the exterior envelope (walls and roof) of the house are very well-insulated with a maximum Heat Transfer Coefficient, U-value of 0.15 W/m²K (R=6.6)

This is much better than:

    • A typical Brick Veneer Wall – U value 0.51   (R = 1.92)
    • A typical Roof – U value 0.26   (R = 3.91)

Elimination of Thermal Bridges

All Wall openings, corners, connections and penetrations are designed, and constructed, with great care, so that thermal bridges can be minimised.

Highly Insulated Windows:

Typically triple glazed windows will be required to achieve appropriate insulation

Air Tightness of the Building:

Uncontrolled air changes from gaps must be smaller than 0.6 of the total house volume per hour which is much better than 1.0 of the total house volume per hour that would be more typical of a new house.

To achieve Passiv Haus certification involves a test where the house is pressurised using a temporary ‘Blower Door’.

Energy Recovery Ventilation:

Because the house will be quite airtight a mechanical ventilation is required to keep the air fresh and prevent condensation.

Passiv Haus systems have highly efficient  energy recovery ventilation systems

In Winter around 75% of the energy from the exhaust air is used to warm the fresh air again by means of a heat exchanger.

In summer the exhaust air is used to cool the incoming air

The ventilation systems also incorporate pollen and dust filters.

For more information go to the The Australian Passive House Association.

 

Electric Underfloor Heating

Watching ‘The Block‘ it seems Electric Underfloor Heating is very trendy these days . . . . so here are some of my thoughts:

Advantages

  • Provide a stable heat.
  • Safe, with no very hot temperatures.
  • Each room can be run separately.
  • Quickly evaporates damp areas.
  • Less air movement than other systems

 Disadvantages

  • Slow to heat up, and slow to cool down when heating no longer needed.
  • Expensive to install and run.
  • Less suitable for intermittent heating
  • Less effective if under materials that have insulating properties such as carpet, or timber.
  • Can damage timber floors.

Types

In Slab

The heating cables are fixed to the top layer of slab reinforcement, before the slab concrete is placed. The system heat up the whole slab, which then heats up the room above.

This system has a long warm up time making it suitable for ‘Off Peak’ tariff electricity, with the concrete slab heating up during the night and releasing the heat steadily during the day.

In Screed

With this system the heating cable is fixed on top of the slab using a light steel mesh, or fixing strips. The cables are covered with 15-25mm of screed.

In screed system which tend to heat less of the slab have faster warm up times than ‘In Slab’ systems and can be considered as ‘direct’ acting system with some storage characteristics.

Under Tile

Under Tile heating consists of a thin heating cable pre-laid on a self adhesive fibreglass mesh which is then covered with the tile adhesive.

This system has the fastest heating up time but the least amount of heat storage.

Finally

I can’t say I am keen on underfloor heating as I used to work in an office that had it many years ago. . .  It caused my feet to sweat excessively with predictable effects when I went home and took my shoes off!

If I was going to use it at all I would probably favour just a ‘Under Tile’ system for bathrooms.

 

See Heating for more posts

 

 

 

Heating – Which Is Cheapest?

Thinking about how you are going to heat your new Home and get Hot Water?

Heating costs do vary depending on state and depending on whether you live in the bush or city.

Historically the cost of heating a home has been, from cheapest to most expensive:

    • Solar. (check out Passive Solar)
    • Wood , Collected. (Will take around 10 days to gather enough for winter)
    • Heat Pumps.
    • Natural Gas. (The way gas prices are going up, $300-$400/year announced today! this may no longer be the case soon!)
    • Off-Peak Electricity. 
    • Peak Rate Electricity. (peak rate electricity is relatively cheap in Tasmania)
    • Wood, Purchased. (Better to buy at least 1 cubic m rather than buying at the servo)
    • Liquified Petroleum Gas. (It’s not just the cost of the gas you also have to pay for cylinder rental)

Whichever method you choose its going to be cheaper if you get the House Size and the Insulation right!

 

See Comparing Gas and Electricity for more information

See Heating for more posts

 

 

 

Comparing Gas and Electricity

Traditionally gas has been cheaper than electricity but with the price of gas rising this has changed.

Actually comparing value for money is quite complicated so I though I would explain how to do the various calculations.

Cubic Metres to Megajoules

Gas is measured at the meter in cubic metres but you pay by the megajoule (MJ) To convert cubic metres of gas to megajoules you have to multiply by

  • The Heating value (*Typically around 38.7)

and

  • A Pressure Factor (*Typically around 1.01)

*check a recent gas bill for the actual values

The value you have calculated is the Megajoules input into your heating system. The actual output can be quite a lot less.

Gas Efficiency

To find the heat output from your heating unit you need to find the actual efficiency of the unit, which can very considerably.

No gas heater has 100% efficiency as some heat is always lost up the flue.

A basic gas heater (3 Star) may have an efficiency of around 60% while some of the 6 star units have an efficiency closer to 95%.

Once you know the efficiency you can just multiply the Megajoule input by the efficiency to get the Megajoule output/Cubic Metre

Megajoules to Kilowatt Hours

1 MJ = 0.278 kilowatt-hours (kw-hr)

Electrical Efficiency

There are two different ways of using electricity to heat your new home.

Direct, or conventional, heating or using the power to run a Heat Pump, or Reverse cycle air conditioner.

The method you choose can make a dramatic difference to the heating efficiency.

Conventional Electrical Heating

With conventional Electric heating, such as panel heaters or fan heaters things are much more straightforward.

Every kw into your house means one kw output (100% efficiency)

That doesn’t mean that overall electricity is 100% efficient, just the inefficiencies occur before the power goes through the meter.

Heat Pumps and Reverse Cycle Air Conditioning

An advantage of Heat Pumps/Reverse Cycle Air conditioning is they have a positive efficiency, they can put out more kw of Heat than the electricity that goes in.

They do this by extracting the heat out of the outside air.

Pick a good unit and you might find them 200% or even 300% efficient for heating!

 

 

 

Thermal Mass for Heating

If you read up about energy efficiency you will come across the expression ‘Thermal Mass’ . . . . . . but what is it? . . . . . and how does it work?

Materials with Thermal Mass

The most common materials with Thermal Mass in new houses are; Concrete, Stone, Slate, Tiles and Brick. In some cases water tanks can also be used to provide Thermal Mass. (But not easy to use as evaporation can  reduce the effectiveness, and the resultant humidity can cause damp)

A key characteristic of these materials are they are dense(heavy) and have the ability to absorb excess heat and then release it in cooler periods.

Thermal Mass need to be exposed. Covering with carpets or timber floors insulates them and prevent it from being as effective.

Heating

The trick is to put either ‘Free  or Low Cost Heat’ or ‘Spare Heat’ directly into the thermal mass which is released to keep your house warm longer.

Free or Low Cost Heat

Direct winter sunlight on a floor or a wall is a great source of free heat.  Just make sure you have Properly Designed Shade to keep the summer sun out.

Sources of low cost heat are things like using off-peak power, or excess solar power.  This can provide either direct heating, or run heat pumps circulating hot water into a slab.

Spare Heat

Each time a wood heater is filled with wood  it should initially be run with the vents fully open to minimise build up of creosote and soot in the flue . Without a thermally massive surround to help absorb the excess heat you can quickly over heat your room.

Any exposed thermal mass that is not heated may feel cool to the touch as it will be no warmer than the room temperature. However as the room cools this thermal mass will still release its heat back into the air to slow down the rate the room cools down. (This is known as ‘Thermal Lag’).

See Passive Solar for more posts

Ducted Heating

Most builder’s standard heating system to homes where mains gas is available is Ducted Gas Central Heating.

This has the following advantages:

  • Low running costs.
  • Relatively cheap to install.
  • Feels warm fairly quickly.
  • Leaves the walls free for furniture, if you have ceiling vents.
  • If you upgrade the duct size refrigerated cooling can be added using the same ducts.

Disadvantage include:

  • Can be noisy.
  • Any allergies can be made worse due to the high levels of air movement disturbing dust.
  • When doors are shut (for example bedrooms), it stops circulation of air back to the central intake point. The heating then becomes less effective in those rooms.

If you decide to choose ducted heating I would reccomend you go for at least three zones. This will allow you to save money by only heating the rooms you are using.

At our last house our zones were:

  1. Kitchen/Family Room, Lounge and Hall (The thermostat was mounted in the family room. If you want it in different  location you need to tell the builder)
  2. Master Bedroom.
  3. Other Bedrooms and Study.

You should check how many of the zones can be served by the unit at the same time.

 

This post is based on a section of the E-Book ‘Guide to Selection / Pre Start’ available at the following link:  anewhouse Guides

 

Condensation

Condensation,  a minor inconvenience,  or a major problem?

A little condensation on windows is easily dealt with, . . . . . .  but heavy condensation in poorly ventilated corners can lead to mould damaging your walls, ceilings, or even your clothes.

Why does Condensation Occur

Condensation in a building occurs when warm air, containing water vapour, comes into contact with a cold surface.

As the air cools it can’t hold as much water vapour so the excess changes into liquid water which is deposited on the cold surface.

The  water usually appears as surface condensation as water droplets or water film on cold surfaces, typically windows.

Condensation occurring on cold walls and ceilings is a major issue as it is when mold problems start. Of particular risk are wardrobes on  an external wall as there is a cold surface and a lack of ventilation.

Sources of Water

Here are five main sources of water vapour in the home

  • People A typical adult will lose around 0.8L/day of water, half from skin evaporation, and half from breathing.
  • Bathrooms Not just the obvious showers and baths, its also those drying towels and bathrobes 
  • Kitchen – Kettles, Pans, dishwasher, and the microwave will add water vapour
  • Un-Flued Combustion – Portable Gas Heaters, Gas Hobs, Bio Ethanol Heaters, even Candles, all emit water vapour into the room as they burn.
  • Laundry – Unvented Tumble driers, Airing Clothes.
  • Evaporative Cooling – Because it is mainly used in summer less of a problem, but can be an issue on cold nights.

Preventing Condensation Damage

Action to prevent condensation damage involves looking at both insulation and ventilation.

Insulation. Additional insulation in walls or ceiling will keep those surfaces warmer which will reduce the risk of condensation damage in most rooms .

Ventilation In bathrooms and kitchens the more moisture laden air means that insulation by itself will not be enough. The moist air needs to be effectively extracted to prevent condensation being an issue. (Although I have previously posted about Heat Loss due to Ventilation some  ventilation is  needed throughout the house)

Role of Double Glazing

Double glazing is often suggested as an answer to condensation however this is not really the case. As the windows are now less cold there is less surface condensation on the windows, so it looks like the issue has gone away. The problem is that without removing the moisture laden air the risk of condensation on walls and ceilings is increased.

See this link to find out why I prefer a separate Extraction fan in the Bathroom: 3 in 1 Bathroom Heaters

To keep moisture out of the insulation materials see this link: Vapour Barriers

 

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