How to Insulate Your Home – A Simple Guide on Home Insulation

Garage Doors , House   Brett Rowley  | 28 July 2020

Have you ever opened a power bill and it sent your reeling? Was there a mistake with the meter reading, or did I use this much electricity?

If your annual power bill falls within the national average of $1,509, you’re consuming too much, especially if there are sharp spikes during summer and winter.

A huge electricity bill reflects your home’s inadequate insulative capacity and is unlikely to be a billing mistake.

Use the hefty energy bills as an incentive to audit your home’s energy efficiency and improve its ability to regulate heat.  

From the walls and windows, to the ceiling and garage door insulation, you’re spoilt for choice when it comes to improving your homes insulative capacity.

What Does Insulation Do?

Insulation eliminates the unwelcome heat exchange between your home and the surrounding environment at your expense.

Insulating your home keeps the frigid winter air from getting into the home and forcing the hot air outside. During summer, a properly insulated house prevents the unwanted hot air from forcing its way into the cooler interior.

Simply put, insulating your home eliminates unwanted heat loss and heat gains that drive up your energy bills. It also helps to maintain a constant internal temperature without overworking your air conditioning unit.

What Does Insulation Actually Mean?

Insulation means erecting a barrier to reduce heat transfer between a hot and cold object. It works by decreasing heat transfer through conduction and convection or reflecting solar radiation.

In this context, insulation entails using insulative materials to reduce heat exchange between your house and the environment. The heat exchange occurs through the walls, windows, ceilings, doors, and gaps in the walls.

Proper insulation creates a thermal envelope, i.e. an energy-efficient house whose indoor environment is independent of the prevailing weather conditions. 

The thermal envelope of a building comprises the internal and external walls, windows, ceiling, roof, floors, and the layout of the home.   

By limiting unwanted heat exchange, a thermal envelope lets you create a warm and toasty home environment without spiking your power bill.

What Is Heat Loss?

Heat loss occurs when heat escapes from the warm interior of a house to the frigid outside environment. It takes place through three mechanisms – convection, conduction, and radiation, both individually and in combination.

Conduction is the process by which heat flows from the hotter area of a solid object to the cooler parts of the object. In a home setting, this type of heat loss occurs through walls, roofs, ceiling, and floors.

Convection refers to the transfer of heat through the cyclic movement of air in your home. Hot air rises to the top, pushing the colder air to the bottom of the room.

Radiation is the flow of heat through space. That’s how heat energy from the sun warms your house during the day. The heat flow reverses during the night, causing your home to lose radiant heat to the colder outdoor environment.  

Why is Heat Loss Important?

You must understand how heat loss affects the ability and efficiency of an AC unit to meet the heating needs of your home. It also helps to determine your home’s energy requirements, a key indicator of its insulative capacity.

What’s Heat Gain?

Heat gain refers to the increase in internal temperature after your home absorbs radiant heat from the sun and other heat sources.

The sunlight striking the walls and the roof of the house is converted into heat, which then transfers into the house, raising its temperature.

As the sun gets hotter, the heat builds up raising the temperatures inside the house to an intolerable level. That forces you to keep your AC running to eliminate the excess heat, racking huge power bills in the process.

Heat gain uses several heat transfer mechanisms. When the sun heats the exterior walls and the roof, conduction transfers the heat to the cooler part of the house.

Infiltration occurs when the warm moist air creeps into the home and forces the cold conditioned air to escape through cracks and gaps in your walls.

Your home also gains thermal energy through solar radiation when the sun rays get inside your home through the windows.

Why is Heat Gain Important?

To lower your energy bills, you need insights into how your home gains energy from the sun. With this information, you can pick the most efficient ways to regulate solar radiation and protect your home from overexposure to the sun.

It can also help you harness most of the winter sun and shore your efforts to keep your home warm during the cold season.

How to Tell If Your House Is Properly Insulated?

Carrying out an energy audit is the best way to test your home’s insulative capacity, but that often calls for technical skills. Luckily, there are other simpler yet effective ways to determine if your home is energy efficient.

1. The Size of Your Energy Bills

Annual electricity bills in Australia range from $1,490 in Victoria to $1,759 in South Australia. Unfortunately, if your bill falls within or above this range, you’re consuming too much.  

With proper insulation, a household in Victoria can shave $400 off the top and lower their annual power bill $1,089.

Check your monthly statement for units consumed, cost per unit, usage trend, and how the bill compares to the region’s average.

If you notice spikes during winter and summer, you may have a problem with your home’s insulation.

2. Temperature Fluctuates Between Rooms

If some of the rooms feel significantly colder or cooler than the rest of the house, despite using a central heating unit, it could indicate an insulation problem.

It could be as simple as door or window letting in a draft, or as complex as heating duct passing through an uninsulated part of your home.

When the warm air from the AC encounters a cold spot in the air ducts, it loses some of the heat resulting in significantly cooler rooms.

3. You Can Feel Chilly Drafts

When the cold winter air enters the home through cracks, crevices or doorways and window frames, it creates noticeable chilly drafts.

If you feel a cool breeze despite having turned on the AC, cold air is infiltrating your house and forcing the warm air out. You may have significant gaps in your wall structure, which points to poor insulation.

4. Your Pipes Freeze During Winter

Water passing through pipes exposed to sub-zero temperature will freeze. Frozen pipes not only subject you to cold showers but also pose a grave danger.  

Since water expands on freezing, frozen pipes can burst and flood the house. You could incur thousands of dollars’ worth of water damage, not to mention the risk of mould infestation.

5. It Fails the Touch Test

The floors, ceilings, and walls of a well-insulated home should feel warm to the touch, even in winter. If the panelling and drywall in the house feel cold or damp, the home’s insulation is lacking.

The exterior walls should feel cold to the touch since insulation traps the warm air inside the home.

6. Ice Dams on Your Roof

Poorly insulated homes lack a snow build-up on the roof after a snowstorm. Insufficient attic insulation allows heat to rise and escape through the roof and melt away the bottom layer of the falling snow.

The melting water flows down only to re-freeze after hitting the sub-zero temperatures along the edges of the roof and gutters. This forms ice dams, large, oversized icicles along the perimeter of the house.

The formation of ice dams signifies that your roof, attic, and ceiling have poor insulation. 

Where Does Heat Loss Happen in Your Home?

An under-insulated home pushes your air conditioner to work harder because the house is continually leaking hot air.  Some of the heat loss avenues include:

Where Does Heat Loss Happen in Your Home?

1. The Ceiling

Under insulating a ceiling wastes 25 to 35% of your home’s heat energy during the cold winter months.

Heating air creates convectional waves where hot air rises and forces the colder air towards the floor. That means you must heat all the air inside the home to maintain a steady warm temperature.

Under-insulated ceilings make it impossible to raise all the air within the home above a specific temperature. The hot air leaks into the attic where it loses its heat through the roof instead of circling in the room and keeping you warm.

Exposed ceilings create an additional and unwanted convectional cycle on the roof. The frigid air above your home rapidly cools the hot air creating a steady stream of cold air for your AC unit to heat once more.

2. The Walls

Depending on their composition, walls lose 15 to 25% of the heat in your home. Ideally, walls should form a physical barrier between the warm air inside the house and the frigid air on the outside.

Uninsulated walls allow cold outside air to suck the heat from the house by conduction because of the temperature difference between the two sides.

Under-insulated walls create an endless loop of heating and cooling cycles that overwork your heating unit.

3. The Windows

Windows cause you to lose 10 to 20% of the home’s heat energy during winter. The standard 1/8th inch thick window pane has R-value of a mere 0.03, which gives it a poor heat retention ability.

Like walls, windows form a physical barrier between the warm interior and the frigid air outside the home. When the warm inside air encounters uninsulated glass, it loses the heat and sinks to the bottom subjecting you to cooler temperatures.

The frigid air outside the glass picks up the heat energy, rises as more cold air moves to the window. The cycle repeats every time you switch on the AC system.

4. Floors

Typical wooden and concrete floors lose 10 to 20% of your home’s heat energy thanks to their inadequate insulation capacity. The R-value of natural wooden floors falls between 0.638 to 0.975 but plummets to 0.25 in engineered wood.

Concrete slabs have an R-value of between 0.1 and 0.2 per inch. A typical uninsulated 8-inch thick floor slab boasts an R-value of 1.35, which means it allows copious amounts of heat to escape.   

Uninsulated suspended floors are susceptible to cold drafts while solid floors resting on the ground can have a dampness issue.

5. Air Leakage

Air leakage or infiltration refers to cold air sneaking into your home through gaps and cracks in the walls. The cold draft pushes out the expensive conditioned air, making it challenging to maintain constant room temperature.  

Infiltration causes your home to lose 15-20% of its heat energy during winter and saddles you with a huge heating bill.  

Cold air passes through wall cracks, gaps below the windows and doors, wall-floor and wall-ceiling junctions, and any other available space.

Spaces around lighting fixtures, utility pipes, improperly fitted floorboards, skylights, door and window frames also contribute to thermal loss. 

The endless supply of cold air forces the warm air to the higher levels of the room and out of reach. That leaves you cold and shivering despite turning up the AC unit.

How to Insulate Your Home Against Heat Loss and Gain

The Building Code of Australia (BCA) dictates the type of building and insulating materials to use when putting up or retrofitting a building in the country.

The Code also sets the required R-values, which is the insulative capacity of building materials, for various climatic zones. You must comply with these requirements to create an energy-efficient home. Compliance avoids legal troubles and expensive repairs later.

Proper insulation turns your home into an energy-efficient thermal envelope that eliminates unwanted heat loss during winter and heat gains in summer.

Insulating the heat loss/gain pathways highlighted here guarantees excellent results.

1. The Roof and the Ceiling

You must install insulation material in the ceiling and under the roofing to block this pathway. The bi-pronged approach safeguards against radiant heat gain and heat loss from inside the house.

While you can insulate all the roof types and designs used in Australia, the installation process can be complicated, mainly if it entails lifting off the roof.

Insulating tiled roofs entails attaching foil batts or double-sided foil to the tile battens in the spaces between the trusses and rafters. You can also insulate the house when retiling the roof.

Reflective membranes make the best choice for metallic roofs because they reflect away solar heat and prevent radiant heat loss. You must remove the entire roof to retrofit the insulation. Luckily, you can do a swell job without damaging the metal sheets.

Ceiling insulation entails layering insulative material in the space between the roof and the ceiling, but you need an accessible roof space.

Alternatively, you can install plasterboards with a reflective foil when replacing your ceiling, although it’s not entirely efficient.   

2. Walls

You can retrofit the walls of any building with either reflective or bulk insulation to improve energy efficiency.

With cavity brick walls, you need a professional insulation installer to fill the cavity with small polystyrene balls or mineral fibre. Insulating the cavities improves the wall’s heat regulation thanks to cavity brick’s high thermal mass.   

With brick veneers and timber-framed walls, you have two insulation options. You can either pump pellets and thermal inside the wall cavity. Alternatively, you could line the walls with concertina foils batts, bulk bats, or plasterboards with a reflective foil.   

3. Windows

Glass has a weak heat retention capacity, which causes hot air to cool rapidly after striking its cold surface. Erecting a barrier between the window and the warm air in the room eliminates unwelcome heat loss.

Insulating windows can be as simple as installing a curtain or as complex as installing double glazed glass. The goal here is to create a pocket of still air inside the glass where no heat transfer takes place.

Coupling thick, close-fitting curtains with a pelmet is a cost-effective way to insulate your home. A pelmet above the curtain rail and a curtain that covers the entire window keep the circulating warm air from the cold glass panes.

You must also seal any gaps around the window frames that could allow hot air to escape while letting in the cold drafts.

4. Floors

Raised wooden floors are easy to insulate because they come with an ample crawl space below. Foil or bulk insulation guarantee excellent results, but you need a professional to handle the installation.

In the absence of subfloor access, installing insulative boards beneath the floor finish delivers excellent results.  

For suspended concrete floors, you can insulate from below or install an in-slab cooling/heating system. Remember to cover all vertical edges of the concrete slab with an insulative material with an R-value greater than 1.

You can also install in-slab cooling systems on concrete slabs lying on the ground. You need to cover all vertical edges of the concrete slabs with a continuous waterproof insulation material with an R-value higher than 1.

You can opt for slab-on-ground edge insulation. It entails installing a cement cover board and a 40 mm closed cell polystyrene board around the perimeter of the floor slab.

5. Draft Sealing

Detecting the air leaks is the first step when looking to air seal a house. You can opt for visual inspection or hire an expert to conduct an energy audit to identify the leaks.

Cracks often result from structural damage, but the gaps occur around electrical outlets, cables, fans, vents, or below windows and doors.

Caulking is the most effective way to repair gaps, cracks, and crevices. Weatherstripping seals can be placed beneath windows and doors, including garage doors.

Due to their sheer size, the uninsulated garage doors contribute to huge heat loss and thermal gain pathways in your home.

Luckily, insulating garage doors not only improves the home’s energy efficiency but also helps soundproof your garage as well. Foam boards, batt insulation, and reflective insulation are some of the popular ways to insulate garage doors.

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Besides drowning the street noise, a well-sealed, adequately insulated garage door keeps away the rodents, water, snow, and insects. If your garage doubles as your workshop, you get to work comfortably through summers and winters.

What Should Be My Insulation Level?

In Australia we are faced with a range of climate conditions. The Australian Building Codes Board (ABCB) has set minimum insulation levels requirements per location.

In Perth, the climate changes with the season and residents will have to face a range of warm temperatures and warm humid days. As a result, reducing heat loss as well as reducing heat gain should be equally important.

In Melbourne, where the climate is generally colder and more humid, reducing heat loss is the main priority.


Never Endure Another Cold Night

Proper insulation keeps your home warm and toasty without saddling you with huge bills from the power company. It turns your house into an energy-efficient unit that conserves the conditioned air at your preferred temperature without burdening your AC unit.

Never again will you endure cold nights in the dead of winter or sleep in sweltering heat in a feeble attempt to lower your power consumption.

Insulating your home improves the quality of life for you and your loved ones and provides a lasting solution to your spiking power bills. 

Brett Rowley

Brett is a garage door expert who also runs Gryphon Garage Doors. He strives for great customer service, excellent product knowledge and constant innovation.