Thermal Control Points

Control points of thermal design in building Fabric

The Four Control Points

Thermal

Possibly the most common thought when thinking of how a buildings fabric can make it more energy efficient is insulation. This is for good reason, insulation is the main barrier of reducing thermal gains or losses. However it not only solves issues, but creates others, and if it’s not installed with complimenting products, the performance can greatly be reduced.

Moisture

Moisture is one of the biggest causes for concern in a building. When it is not managed properly, it can lead to bad smells, poor or harmful air quality, structural damage, or conditions to harbour unwanted pests. Given the potential for harm, you would think there would be strict regulations around it, but you might be surprised to learn, the National Construction Code barely gives it a mention.

Air

Air management is critical for other products such as insulation working as they should. Many typical types of insulation are very susceptible to having their nominated performance levels reduced due to poor air control. This is another element that is barely covered by the Building Code let alone regulated against.

HVAC

The ability to correctly manage ventilation systems within a building becomes more paramount as the control points are tightened. Controlled ventilation is extremely important to occupants heath and well being and helps regulate comfortable temperatures of a building.

frame houses placed in countryside

Thermal Control

For years the benefits of thermal control have been well understood and indeed implemented as a mandatory requirement in our National Construction Code (NCC). However with new requirements introduced into NCC 2019 Vol 1 with respect to thermal bridging, not all insulations are created equal. Or perhaps more aptly, when to use one insulation over another becomes more apparent.

Thermal Control of a building refers to a material, or a conjunction of materials’ ability to slow the transfer of heat through some kind of barrier, such as a wall. Typically this is measured in either R-Value or U-Value. Until recently, the effects of thermal bridging we’re considered by the NCC, and still aren’t in residential design.

what is thermal Bridging?

Heat takes the path of least resistance. A thermal bridge is a discontinuity of the thermal barrier which is usually a result of a required structural element such as studs in a wall. Even with the highest performing insulation, its ability to reduce thermal transfer of heat is limited by any thermal bridge within a construction.

Thermal bridge in a metal stud wall

However deliberate design practices and products can counter these issues. To find out more about these strategies and products click here.

Types of heat transfer

Heat is transferred by three means. Its important to remember that heat is just a measurement of internal energy of something.

  • Conduction
    • The direct transfer of energy through a material. Like when you touch a hot surface.
  • Convention
    • The transfer of energy through a fluid medium such as air. Like when you feel the hot air come out of an oven.
  • Radiation
    • The electromagnetic transfer of energy. This is why you can feel the heat of the sun.

This is important because different types of insulation may only work to reduce one or two of these. Sometimes combining two types of insulation to ensure all thee methods of heat transfer are limited is a great option. Some products will even be a hybrid of two type of insulation put together for this exact reason.

abstract background with raindrops on misted glass

moisture Control

We all know more insulation in a building is a good thing, right? Well it might surprise you to know as you increase the levels of insulation, the risk of condensation can often increase. Moisture can be a huge issue and cause a multitude of problems. It needs to be managed carefully within a building, but it is a problem that is poorly understood in Australia.

where does problematic moisture occur?

The easiest type of problematic moisture to understand is the one that enters a building in liquid form. This is typically from either poor workmanship, poor design or a building that is falling into disrepair. Example of this would be a leaky roof, or water running down an external wall and tracking across a floor into a building. This type of issue is usually easy to track to the point of entry.

The next type of issue is know as interstitial condensation. Moisture, like heat, travel from hot to cold. You will also know that condensation forms when hot air cools and can no longer support the moisture content. The moisture then precipitates from the air and attaches to any nearby surfaces. This can be an issue because in winter, as hot air travels from inside your building to outside, it cools and condenses within the framing of your building. To learn more about strategies to prevent this click here.

photo of clouds during dawn

Air Control

To control an environment properly, we need to be able to control what air moves where and when. the movement of air not only impacts the health and wellbeing of the occupants, but also impacts the real performance of some types of insulation.

Does the building code consider air infiltration?

While most first world economies have moved to introduce maximum air infiltration rates, Australia only has vague non-quantitative limits. Instead it includes some motherhood statements around how to limit air-infiltration.

If the building code doesn’t consider it, should you? Absolutely! Studies have demonstrated many negative effects of not being able to control air infiltration properly. Often the strategies and products to control air infiltration on a building add little additional cost to the overall build, however have significant benefits. Unlike many other items you might add to a building for a benefit, these benefit are for life. They are only likely to increase your return on investment over time as power prices continue to increase.

white concrete building

HVAC

To control an environment properly, we need to be able to control what air moves where and when. the movement of air not only impacts the health and wellbeing of the occupants, but also impacts the real performance of some types of insulation.

Does the building code consider air infiltration?

While most first world economies have moved to introduce maximum air infiltration rates, Australia only has vague non-quantitative limits. Instead it includes some motherhood statements around how to limit air-infiltration.

If the building code doesn’t consider it, should you? Absolutely! Studies have demonstrated many negative effects of not being able to control air infiltration properly. Often the strategies and products to control air infiltration on a building add little additional cost to the overall build, however have significant benefits. Unlike many other items you might add to a building for a benefit, these benefit are for life. They are only likely to increase your return on investment over time as power prices continue to increase.

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