Building Design, Drafting & Energy Efficiency

Can it be built?

Last week I had a work experience student in the office. On his last day he brought in a  floor plan of a house he designed for a school project when he was in grade 6. With a mix of pride and apprehension he showed me his design and asked, “Can it be built”?

As I looked over the design I considered his question. I thought about the use of the space, the bushfire requirements, the energy efficiency implications, the required head height over stairs, the rise and run of steps, the width of passages, the swimming pool fence requirements, the difficulty of the build, the practicality of curved glass and the expense of the build.

After considering all of these practicalities and rules I stopped…………. I stopped because I was suddenly reminded of a house I designed when I was 10 years old, (it was an underground house with periscope windows). Just like the design I was currently looking over with a critical eye, it was a house that was designed with pure imagination and uninhibited by any form of constraint. It was pure design, pure joy and a refreshing jolt back to the reason why we do this job in the first place.

So, the question was, “Can it be built’? My answer, “YES.!”




Did you know that Services are part of energy efficiency compliance? Most people don’t.

Click here to find out more.

Lighting allowances

A bit of confusion exists in the understanding of the requirement for artificial lighting. As part of the current energy efficiency regulations, artificial lighting needs to be calculated to ensure a reasonable level of power usage. The allowances are measured in Watts per square metre as per the following:

  • Class 1 (house): 5w/m2
  • Class 10 (garage/carport): 3W/m2
  • Verandah/Balcony: 4W/m2

There is also an allowance for exterior perimeter lighting. I won’t confuse things by addressing this right now, (it’s all about efficacy, motion sensors, daylight sensors and switching arrangements).

The main confusion is that many people regard the allowable Watts as an indication of the amount of light produced. This is incorrect.

A ‘Watt’ is a measurement of power. Light is measured in ‘Lumens’.

Still confused? Think of an old car and a new car. The old car uses a lot of fuel to travel from A to B. The new car uses less fuel to travel the same distance.

Now think of an old incandescent light globe and a new LED globe. The old incandescent globe uses 100 Watts to light a small room. The new LED globe uses 22 Watts to light the same room.

  • 100W incandescent = 1600 Lumens
  • 22W LED = 1600 Lumens

So in summary, just as buying more petrol to run an old car requires more money; more Watts to run an old light globe requires more money to be spent on your electricity bill.

When you choose light fittings make sure you choose energy efficient fittings such as LED (Light Emitting Diode) or CFL (Compact Fluorescent). Look for the Lumens to gauge how many you need for the task.

So, how many Lumens do I need?

This depends on your individual requirements, so the below is a general guide, representing the amount of light needed in typical areas. All you need to do is multiply the area of the room by the number of lumens required.

  •  In dining rooms and corridors you will need around 10 – 20 lumens per square metre.
  •  Kitchens and rooms where you read casually will require more lighting, around 20 – 55 lumens per square metre.
  • Rooms for more intensive reading or study need to be better lit, with a lumens requirement of around 55 – 110 per square metre.

As an added extra we can provide a room by room lumen calculation with our energy compliance reports.





How does double glazing work?

Is double glazing worth having?  Won’t it be cheaper to have single glazing?

These are two questions that I am asked quite frequently. The answer to both is yes.

Although both answers are ‘yes,’ the first question is the important one, so let’s deal with that one first.

Is double glazing worth having?

Double glazing works by trapping air between two panes of glass. This trapped air creates an insulating barrier which serves three functions:

  1. First of all it prevents heat loss or gain through the window because the barrier insulates the room from differing air temperatures at either side of the glazing unit.
  2. Secondly, double glazing helps keep noise pollution down.
  3. The third benefit of double glazing is that it helps reduce condensation. Condensation commonly occurs on the inside of single glazed windows due to the warm air inside the house being cooled by the cold outside air. With a double glazed window the insulating barrier prevents the transmission of air temperature and therefore helps prevent condensation occurring.

Although double glazing insulates against differing air temperatures, it does not insulate against radiant heat. This makes a double glazed unit a good choice for permitting winter sun to warm the inside of the house whilst at the same time insulating from the cold outside temperature.

So, back to the second question.

Won’t it be cheaper to have single glazing?

Of course it will be cheaper but it will also have a poor thermal performance and you will end up endlessly wiping condensation off the inside face of the window during the winter months. Also, just remember, if you’re not motivated to wipe the condensation away you will end up with mould growth which in turn will cause health problems for your house and its occupants.

This may seem like a pretty strong point of view on glazing but just consider the following points:

  1. Current thermal requirements for external walls states a minimum insulation value of R2.8. We achieve this with wall insulation. A typical aluminium framed, single glazed window has an R-value of R0.15. That’s over 18 times less than the wall next to it. So, if you’re going to insulate your walls, it makes sense to insulate your windows with double glazing.
  2. A consequence of highly insulating and draft sealing our homes is the increased risk of condensation. condensation will occur on the thermally inefficient windows. Double glazing goes a long way towards mitigating this risk.

If you are trying to cut costs on your building project, be careful when choosing your windows. A budget based decision might be good in the short term but you will certainly pay in the long run.

Build Budget

How much money do you intend to spend on your building project?

This is one of the first questions I ask in my initial consultation with clients. The reason for asking this question is to ensure that the design is buildable within budget. It would be a total waste of time and money to have a design fully documented only to find out that you can’t afford to build it. You would then need to have the design re-done at extra cost and extra time.

In the past I have found that some clients are a bit guarded and reluctant to let me know what their budget is. It might seem a bit personal to ask someone how much money they have, but it is important from the designer’s perspective to be aware of the budget in order to steer the project in the right direction. Just to reassure any prospective clients, my fees ARE NOT based on a percentage of the build cost. My fees are based on how many hours it takes to do the job. I provide a fee estimate after the initial consultation once I am aware of the scope of works, (refer to my step-by-step procedure).

So, in summary, at the start of the project, have a budget figure in mind and let the designer know what it is. If you have no idea about build cost, ask the designer for some guidance. A frank discussion about build cost at the start of the process will avoid ugly problems later.

House star ratings

Question:   How many stars does a new house require?

  1. 5 stars
  2. 6 stars
  3. 10 stars
  4. No stars

Answer:   4. No stars, (although there is a bit more to it).

The actual requirement is that the house needs to be compliant as per the NCC (National Construction Code) in accordance with the Performance Requirements.

There are a few ways to do this:

  1.  Conduct a Thermal Performance Assessment using approved simulation software (where the result must be minimum 6 stars).
  2. Use the NCC Deemed to Satisfy method. This prescriptive method involves specifying thermal requirements as prescribed in the Code.
  3. Proposing an Performance Solution that satisfies the NCC Performance Requirements.
  4. A combination of the afore mentioned methods.

As you can see, the original question is actually a slightly misguided one. Most people relate new houses to ‘star levels’ but this is not the actual requirement.

So, what is the best approach?

The best approach is to choose the method best suited to the individual circumstance. This can vary from job to job.

One important thing to note is that a Thermal Performance Assessment, (star rating) only assesses the thermal fabric of the building in relation to heating and cooling loads. It does not assess:

  • lighting
  • services
  • hot water systems
  • condensation

As part of our energy compliance reports we  make sure to address all components. Our approach is to not look at  thermal performance in isolation but to address it as part of a holistic system of achieving a comfortable,  energy efficient and healthy home.

new website

After 5 years of having a half-built website I finally decided to do something about it.

Having the ability to write HTML code and build websites from scratch, I had always intended to do exactly that and finish off my site. The problem I faced was ‘time’, or lack thereof.

Although WordPress doesn’t give me the ability to endlessly customise & optimise pages, it does provide a simple and quick way to establish a professional and comprehensive web presence. It is also easy to keep up to date, and is viewable on desktop and mobile devices.

The simplicity of WordPress allows me to spend less time on web related input and therefore  frees up my time to do actual work.

I hope you find all the information you require on my new site. I will fine-tune it over time and add extra content via blogs.


Greg O’Beirne

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