Some builders are concerned about making home too airtight Some arguments they give are:

1. “Humans need to breathe, and so does a building.”
2. “We don’t want occupants suffocating—fresh air has to come from somewhere.”
3. “If the building is too tight, we’ll need to install an HRV or ERV system.”
4. “If we’re relying on natural ventilation, why worry about air leakage?”
5. “We don’t want mould growing in our buildings.”

To begin with, these concerns stem from of lack of ventilation, not airtightness.  Air leakage is NOT ventilation. So lets get back to basics:

What is Ventilation?

Ventilation is the intentional introduction of outdoor air into a building, either through natural or mechanical means. In apartments or enclosed buildings, it’s also crucial to consult with a fire engineer and implement a pressure relief strategy for fire safety.

• Natural ventilation relies on open windows, vents, and other planned openings, driven by wind and temperature differences.

• Mechanical ventilation uses fans to deliberately supply or exhaust air.

For ventilation to be effective we need to consider the quantity, the quality, and the distribution of air into an occupied space. Can air leakage satisfy these three factors? Here’s why it falls short:

• Air from leaks is not filtered. It may come from a mouldy, dusty, or vermin-infested building cavity.
• There is no way to easily temper the air coming in, so it brings the temperature, humidity or dryness of the outside with it.
• Air leakage leaves you at the mercy of the weather. On windy, hot, or cold days, there is lots of air exchange. But on calm days there is almost none.
• Because you can’t locate or control all air leaks, it’s very hard to make sure each room gets the right amount of fresh air.

There is no way to compare air leakage with ventilation! Not only does infiltration fail to meet ventilation needs, but it also has additional harmful effects to your building and the health of its occupants.

Condensation and Mould Risk

When infiltration brings air from outside, it can create localised cold spots in walls, floors, and ceilings. These have the potential to create condensation, which can lead to mould growth or stains on finishes. Unchecked, condensation can lead to rotting or corrosion of materials, causing structural damage. It also makes a more inviting habitat for a termite infestation. Mould hidden inside walls can spread spores throughout the home and is nearly impossible to clean.

For buildings that are designed for natural ventilation, the openings should be fitted with condensate drains and be constructed using water-resistant materials. The location of these openings should be accessible for cleaning and maintenance. The most common example is mould that forms on leaky windows, which can be cleaned easily.

Reduced Insulation Performance

When insulation materials are rated in the laboratory, they are under controlled conditions with no air moving through the test sample. In the real world, air leaks can pass air through insulation, which substantially reduces insulation performance in two ways:

• Direct bypass – air leakage can pass right around both rigid and fibrous insulation
• Wind washing – air can pass through bulk insulation material itself, disturbing air pockets trapped by the fibres and stealing the heat it is meant to retain

Unwanted distribution of pollutants throughout the building

In leaky buildings, pollutants can distribute through a building via unintentional gaps and cracks. This can create problems ranging from minor nuisances such as odours to more serious issues such as carbon monoxide from a garage or car park. Most dangerously, they are a potential path of smoke in the case of a fire.

Other issues from air leakage

Air leakage in larger buildings can also contribute to noise infiltration and noise production from whistling under windy conditions. Lastly, any hole to the outside, garage, underground car parks or other unconditioned spaces serve as easy paths pollutants or unwanted pests. Sealing up these paths is the cheapest and first method of pest control.

To address concerns for airtightness in homes:

When someone says a house “needs to breathe,” ask them to breathe through their eyes. Sounds ridiculous, right? Humans breathe through their mouth or nose—designed for that purpose. Homes should do the same: breathe through designed ventilation systems.

Key points:

• You can’t make a home too airtight if you provide proper ventilation.

• For typical homes, mechanical ventilation can be simple and low-cost. A continuously running, remote-mounted exhaust fan is quiet and energy-efficient.

• Air should never come through walls—true fresh air should be filtered, controlled, and delivered where needed.

• To prevent mould and condensation, combine mechanical ventilation with thermal bridge control. Even uninsulated outdoor areas like carport soffits can grow mould, showing that moisture control is more complex than ventilation alone.

Not all wall wraps are created equal. Different users have different requirements and expectations for what they want their wrap to do.
In most cases we should, and can expect modern nonwoven textile wraps to control:

1. Water – Prevent rainwater from entering the building during construction before cladding is installed. This protects insulation, internal services, and finishes that aren’t designed for exposure, reducing risks to both occupant health and structural integrity.
2. Air – After construction, uncontrolled air movement can worsen moisture problems, enable water ingress, introduce unwanted noise, increase heat loss/gain, and allow the spread of fire and smoke.
3. Water Vapour – Condensation and high humidity can cause mould, rot, and long-term damage to structural elements.
4. Fire Safety – Wraps should not contribute significantly to combustibility in the building envelope. Some glass/aluminium laminates are classified as non-combustible under the NCC, while vapour-permeable and foil laminate wraps are generally of low flammability, not non-combustible.

Sometimes we may be forced to compromise on some of these control layers, but we also need to pay attention to the minimum requirements in the National Construction Code (NCC).

NCC 2019: Improved Clarity for Combustibility Compliance

The 2019 update to the NCC clarified which materials can be used in areas requiring non-combustible construction. Key excerpts from Clause C1.9 include:

• (a) In Type A or B buildings, external walls (including all components like facade, framing, and insulation), lift pit floors, and certain internal fire-rated walls must be non-combustible.

• (b) Non-loadbearing shafts must be non-combustible if they span more than two storeys in relevant building classes.

• (c) A loadbearing internal wall and a loadbearing fire wall, including those that are part of a loadbearing shaft, must
  comply with Specification C1.1.

• (d) Exemptions include gaskets, caulking, sealants, termite barriers, laminated glass, glazing thermal breaks, and damp-proof courses.

• (e) Permitted materials where non-combustibility is required include plasterboard, fibre-cement sheeting, bonded laminated materials (if each layer is non-combustible and adhesives are thin), and sarking-type materials ≤1mm thick with a Flammability Index ≤5.

The NCC 2019 update resolved long-standing conflicts where non-combustibility requirements clashed with the need for air, water, and vapour control—especially in external wall assemblies.

The Challenge of Wrap Performance: Vapour vs Airtightness

There never has been a wrap product available that meets the NCC requirement for non-combustibility, while at the same time as being an effective air and water barrier, combined with sufficient vapour permeability for use in cool and temperate climates.

Current products on the market today that are deemed non-combustible are made from pure aluminium foil laminated, an adhesive layer and a woven glass cloth.  Aluminium Foil when reinforced can be very airtight, but these products are also extremely vapor tight (Incapable of allowing moisture vapour to escape/permeate to the outside).

To improve vapour permeability, some manufacturers perforate the foil—creating a trade-off. These perforations compromise water and air barrier performance. After all, nobody sells umbrellas with holes in them.

On the other side of the equation, with aluminium foil type wraps, if the holes are so small and infrequent, these types of products still struggle as a vapour permeable underlay. Like single glazed glass windows, aluminium foil is a non-porous material, and it is prone to condensation forming on its surface. Over the past year, some manufacturers have published questionable vapour permeance values, with figures shifting from plausible to implausible and back again.

Polyolefin Textiles: A Better Option

Well established polyolefin textile air and watertight vapour permeable wraps can provide a far superior vapour permeability performance without compromising other important features.

If following a deemed to satisfy path using NCC 2016, it will require some compromise of water tightness, air tightness or vapour permeability.  The only realistic option to date has been to insulate externally the non-combustible sarking, use a non-combustible vapour permeable sheathing board, or follow a performance solution / fire engineered pathway.

Water Barrier Classification: AS 4200.1

Looking at the requirements of a water barrier under the AS4200.1: 1994 code for sarking you can see that almost all perforated aluminium-based materials are unhelpfully classified as:

“Water Barrier – Unclassified”

6.4 Water barrier – The water barrier classification shall be neither high nor unclassified. The resistance to water penetration shall be determined, as required, by the method described in AS/NZS 4201.4. as follows:

(a) High The material shall only be classified as high if it passes the test,

(b) Unclassified When the material is not classified as high, it shall be unclassified.

In terms of AS4200.1 : 1994 classification, if a datasheet is reporting a product to be “unclassified”, it means it has not passed the water barrier test which is a simple 10cm standing head of water test.

The current version of AS4200.1: 2018 is more helpful to the user and the product will now be defined as:

“Water Barrier – Non-water barrier”

5.3.5 Water control classification

The water control classifications shall be determined as follows;

(a) Water barrier – if the membrane passes the test specified as AS/NZS4201.4.

(b) Non-water barrier – if the membrane fails the test specified in or has not been tested to AS/NZS 4201.4.

How then have things changed for classification of vapor permeance?

Vapour Control Requirements

In the 1994 version of the code there was no classification of vapour permeance. Products were either a low, medium or high classification as a vapour barrier.  Just because a material wasn’t a particularly fantastic vapour barrier does not imply that it is sufficiently vapour permeable.

The 2019 NCC Condensation Management DTS requirements for climate zones 6,7 & 8 now requires a vapour permeable membrane, In the updated 2017 version of A4200.1 vapour barrier and vapour permeable membranes using table 4.  See below.  (Southern Australia and Alpine areas)

We should only be seriously using class 4 products with a vapour permeance of >1.14µg/N.s  Class 3 seems like a bit of a holdover from the old building code to cover the old “perforated” foil wraps Perforated sarking).

When considering that a typical paper faced plasterboard has a permeance of around 2.0µg/N.s  then it is a good rule of thumb to ensure the external wrap is at least as permeable (>2.0µg/N.s) as the interior plasterboard lining. In order to control moisture successfully inside a wall system the vapour permeability of materials is increasingly vapour permeable toward the outside of the wall system.

TABLE 4

VAPOUR CONTROL MEMBRANE (VCM) CLASSIFICATION

Vapour permeance (see Note)

Class	VCM Category	Min. (μg/N.s)	Max. (μg/N.s)
Class 1	Vapour Barrier	0.0000	0.0022
Class 2		0.0022	0.1429
Class 3	Vapour Permeable	0.1429	1.1403
Class 4		1.1403	No max.
	ASTM-E96 Method B Wet Cup - 28 C 50%RH

NOTE: Vapour permeance is the inverse of vapour resistance. It shall be calculated as follows:

Vapour permeance μg/N.s = 1/(Vapour resistance MN.s/g)

Almost all building wraps are technically combustible, but the caloric value (the heat produced by the complete combustion) of wraps is quite small compared to the volume of materials that are non-combustible in a wall system.

According to NCC2019 building wraps/membranes that are less than 1mm thickness with a flammability index of no greater than 5 can be used wherever a non-combustible material is required.  This means you can now have your cake and eat it.  For applications using NCC 2016, in most cases, your only solution is to discuss with your fire engineer about a performance solution.

Using Vapour Permeable Wraps at the Bottom of wall detailed with air tightness.

Getting an airtight barrier at the bottom of a brick veneer wall system using damp-course as your air barrier, with an overlap from a vapour permeable wrap. If you have any questions, please contact us.

Fireplaces are completely incompatible with energy efficiency.  Wood Fired fireplaces can provide a really comforting radiant heat source but, in today’s day and age, we just don’t have time to use them.  They can be a bit of an effort…

• to organise the wood,
• keep the area clean,
• and in some cases, starting the fire can be a hassle

Chimneys introduce the following issues into your home when they are not in use;

1. Allows bugs and creepy crawlies to come inside
2. Dust and debris can come in through the flue
3. In some cases of birds have been found coming inside via chimneys
4. Warm air in your home freely passes out of your home, at a very significant rate.
5. They may leak water into the home when it is raining

There are a few solutions available out there to seal them up temporarily or permanently. Chimney balloons can help but are often not fully effective. A combination of Proctor tape and membrane or rigid foam board can provide a more reliable solution.

Warning! You must be careful not to try to use the fireplace if you’ve sealed it.

When a fireplace is in use, it requires a source of air leakage to operate safely.  Air needs to be drawn from wall vents or gaps in the building envelope. This provides convection to get all the nasty gases and particulate produced by the combustion process out of your living space. Without adequate airflow, combustion gases can build up indoors, posing serious health risks.

Most of the time people do not use their fireplaces, and we rely on gas ducted heating systems, split systems or other types of heating to do the job.

Ducted heating running, with an open chimney, with or without the fireplace in use, will lose a lot of air from your building envelope. You are warming up the neighbourhood

A Similar Chimney Effect (Evaporative Cooling)

Does evaporative cooling work?

Upside Down Retrofitting Energy Efficiency, driving down your heating and cooling energy costs systematically.

You don’t have to turn your house upside down to bring energy cost down! This upside-down pyramid provides a structured approach to increase energy efficiency. The most important thing to remember is that each step should be carried out in the correct order (1-9) to gain the maximum benefit. The first step is relatively easy, but very cost effective. As you go down the steps, the cost and difficulty of the retrofit increase.

Step 1:

Begin by sealing gaps around window and door architraves. Caulk the skirting boards to the floor and block any old wall vents with plaster or closed cell foam backing rod. Inside cupboards in the kitchen, laundry, and bathroom, seal around plumbing penetrations. Don’t forget to check behind appliances like the fridge, dishwasher, and oven for hidden gaps. If you have ducted heating, find the return grill, take it off the wall and inspect and seal the cavity behind it. In areas, you can reach, inspect the insulation for gaps and compression (under the floor, in the ceiling space.)  Insulation works best with continuous coverage.

Step 2:

Draught-proof your bathroom, toilet, and kitchen exhaust fans by adding flaps or dampers and ensuring they are ducted outside. At the same time, add supply air vents to help fans work efficiently. Upgrade all door and window seals, and make sure external doors are fitted with appropriate draught stoppers. Quality sealing products can be sourced from Tighthouse.

Step 3:

In winter, cover evaporative cooling vents, as they act like chimneys and allow warm air to escape your home. For better long-term performance, consider removing the evaporative cooler altogether and installing inverter split systems to provide efficient, targeted cooling.

Step 4:

Replace old box (wall) air conditioners with split systems, which are far more efficient. When these new systems are installed, ensure all wall and ceiling penetrations are properly sealed to maintain airtightness.

Step 5:

From the attic space, use expandable foam to seal off internal wall cavities, paying particular attention to cavity sliding door pockets. These internal walls can leak significant amounts of air if not properly sealed.

Step 6:

Have a professional installer apply spray polyurethane foam under timber floors. This helps both insulate and seal the area effectively. Make sure the installer also covers the lower portions of external walls to stop insulation from sagging or falling over time.

Step 7:

Engage a specialist to insulate existing external walls with loose-fill insulation. This method is effective and minimally invasive.

Step 8:

Once your home becomes more airtight, you’ll need to maintain healthy indoor air quality. Install a whole-house mechanical ventilation system such as an Energy Recovery Ventilator (ERV). These systems help filter dust and pollen, regulate indoor CO₂ levels, and recover heat or coolness from outgoing air to pre-condition the incoming fresh air.

Step 9:

Finish by installing double or triple-glazed windows with key performance features. Aim for a gap of 10 to 14 millimetres between panes, use non-metallic spacers to avoid thermal bridging, and choose window frames made from timber or thermally broken aluminium. Low-E glass is a worthwhile upgrade if budget allows. After installation, seal around the architraves to maintain airtightness.

Undertaking all 9 steps will result in the ultimate energy efficient house, but rest assure that each step will bring with it some tangible benefits including lower energy bills!

Although critical, these features don’t give a complete picture of the efficiency of a house. Even with these expensive building elements, envelope air leakage into the building must be tackled. 

The air inside your home, with its heating or cooling energy contained in it, always moves through a building envelope and escapes to the outside. This air movement is caused by holes and gaps in air conditioning duct work, walls, ceiling and floor systems, exacerbated by air pressure difference between inside and outside. The holes and gaps are often small, but there are 100’s of them throughout your home: power points and switches on external walls, gaps under skirting and around window architraves, attic access, ceiling exhaust fans, down lights, to name but a few.

A pressure difference can be created through several factors, most often the wind blowing against your house, an exhaust fan in the bathroom, or a leaky ducted system throughout the house.

The result of all this air movement is expressed as an air leakage rate or in air changes per hour (ACH). For example, if your home has one (1) ACH at ambient pressure, it means that total volume of air in your house has been replaced by outside air once every hour, even with little or no wind blowing outside. If the wind picks up, the ACH of a house multiplies many times.

The following graph explains the relationship between wind speed and the pressures it creates on the building envelope. To test the air leakage of a building, a pressure difference of 50 Pascal (Pa) is applied. This test is performed through the use of a ‘blower door’, a mechanical device designed to determine the air tightness of a building envelope.

Air leakage testing at a pressure difference of 50Pa is an internationally accepted standard. If for example, the building leaks at a rate of 10 ACH at this pressure, it is expressed as 10ACH at 50 Pa. As seen in the graph, a 50Pa pressure difference is comparable to a wind speed of 32 km/h blowing against the building, while a 1.5Pa pressure difference is equivalent to a 5km/h wind.

Once you have made the decision to address the air leakage of the home, the question then becomes how (air) tight the building should be. If it’s too tight without proper mechanical ventilation, it will impact the indoor air quality. But if it’s too leaky, it will affect the energy efficiency. Here is where an air leakage test can provide the answer. Not only will this test give you an ACH at 50Pa of your home, but it will also pinpoint all of the invisible holes and gaps.

Another useful diagnostic tool in this testing process is the thermal imaging camera. This camera can pick up temperature differences in a building envelope, as well as show where insulation in the wall or ceiling is missing.  If 5% of the building is not insulated correctly, the overall efficiency of the insulation drops by roughly 35%! Therefore, it is important to have a continuous insulation barrier for the whole house.

If after sealing, the ACH of your house drops below 10ACH at 50Pa, a well thought out ventilation strategy should be implemented. One such strategy is the installation of a mechanical whole house ventilation system, which introduces tempered fresh air to the living and bedroom areas, and removes stale, moist air. It is important to make sure that exhaust fans in kitchen, bathroom, and toilets can do their job, by allowing sufficient make-up air to be introduced back into those areas of the house. Poorly running exhaust fans are more than often the cause of mould and mildew.

In most cases, however, a building envelope can be sealed to the right level and thus provide a balance between energy efficiency and healthy indoor air quality.

There are many benefits of having a well-sealed building envelope: It makes the house substantially more energy efficient and comfortable, reduces moisture issues (mould!), and keeps dust, insects, and noise out. Compared to double glazing and extra insulation, sealing your home is extremely cost efficient and relatively simple to do. It is an investment with a substantial payback and can represent in many cases a 25% reduction in the overall energy cost.

Now for the most important question: How energy efficient is you home?

Contact us Efficiency Matrix, for an appraisal of your home…

By Jan Brandjes

The Pyramid for Building & Renovating Smarter

Eco living is not a fad, in fact, it’s here to stay, and people are getting more serious about it. In fact, all house plans submitted to councils must now meet a minimum energy star rating. Builders, architects, and designers are becoming more conscious of the effects of eco-smart designs, and homeowners realise the benefits to their wallets and the environment. 

The 10 points in the house/pyramid highlight the foundation elements and cost/priority actions when building or renovating a home. These aspects ultimately make the home comfortable, less high maintenance, environmentally friendly, and energy efficient.

First of all, it’s important to understand, sustainability.  A wonderful foundation of information for this is Passive House.  It’s a very hard standard to satisfy, but if you get halfway there, you will be in the right place.

1. House plan

For a new house, sketch the house plan. Position living spaces, such as the kitchen, dining and lounge rooms on the north side, and utility areas and bedrooms in the south. By doing this, you ensure that living spaces benefit from the winter sun and the bedrooms stay cooler in summer. Remember that good design or bad design will cost the same amount of money!  In a retrofit, implement shading on north facing brick walls, extend eaves, put in place window shutters, to allow winter sun in, and disallow summer sun.  Install deciduous trees and creepers which may help you to protect thermal mass in summer and expose thermal mass in winter.

2. Summer and winter

Always consider the impact that the seasons have, particularly summer and winter, on the house. How will your design deal with the hot summer sun? And how will it handle cold winter winds?

Make sure you have external shading on the north side to protect interior living areas from the harsh summer sun. This approach will still allow the winter sun into your house when it starts to become a bit dark and dreary indoors as well as outside. This will also reduce the amount of artificial light needed indoors during winter.

3 & 4. Ventilation and Indoor Air Quality

Here we consider the importance of ventilation when building a well-sealed building envelope.  If you’re building an airtight home (especially below 0.5 ACH@5Pa), you must consider mechanical ventilation with energy recovery. These systems: provide 24/7 fresh air in living areas and bedrooms while exhausting stale air from the bathrooms, kitchen, and utility areas. They can recover up to 80% of the energy from the outgoing air. They are often ducted throughout the entire house. When combined with a high-performance building envelope, these systems maintain comfort and air quality with minimal loss.

5. Airtightness: Sealing Gaps and Cracks

The building envelope, your home’s external walls, ceiling, and floor, must be as airtight as possible. Before plastering, seal all gaps and cracks to minimise unwanted air infiltration and prevent energy loss from your home.

Every home, airtight or not, still needs controlled ventilation. Without it, you rely on uncontrolled air entering through cracks, which also lets your heating or cooling escape. The key is finding a balance: seal the building to prevent energy loss, then introduce the right amount of fresh air and exhaust the stale air, ideally via mechanical ventilation. Sealing the building envelope tight enough and at the same time providing the right amount of natural infiltration, requires implementing some smart strategies. The good news in all of this is that it can be done very cost effectively in both new construction and existing buildings. This ensures a healthy and energy-efficient home.

A blower door test measures air changes per hour (ACH) at various pressures. A good target for Australian homes is just above 0.5 ACH at ambient pressure. If you aim to go tighter, a mechanical ventilation system is essential.

6. Insulation consistency

There are several types of insulation available on the market

• Batts and blow-in insulation (trap air to resist heat flow)

• Reflective foils (reflect radiant heat in summer)

• Sheet insulation (for structural and high-performance needs)

Whatever insulation you choose, make sure it is installed correctly. Any gaps or holes in the insulation barrier could result in air leakage and energy loss. If you opt for downlights in the ceiling, remember that each creates a hole in your insulation, reducing its performance unless appropriately sealed and managed. This is a building regulation to prevent overheating of light fixtures.

7. Double glazing

Double-glazed windows are a good investment for energy efficiency as well as acoustic comfort. They reduce heat loss in winter and heat gain in summer, lower noise transmission, and can be enhanced with low-e coatings or films.

While more expensive upfront, they offer long-term savings and comfort. Do your homework to find the best solution for your climate and budget.

8,9 & 10. Heating, Cooling, Solar, Lighting, and Appliances

Having done everything to seal and insulate the building structure, it is time to decide how to heat or cool your house.

If you have followed the preceding steps in the upside down the pyramid to plan, then you will need very little heat in winter and almost no cooling in summer.

Perhaps a small, energy-efficient, split system heat pump in winter and a couple of ceiling fans in summer may be all you need.

And because the bedrooms are on the south side of the house, they’ll be cool in summer.

Then, with the money saved from heating and cooling, think of installing a heat pump hot water system.

If your budget allows for it, consider a mechanical ventilation system for the entire house. Especially in a well-sealed house, this system will provide fresh, filtered air all year round with minimal loss of energy.

It is also effective in reducing high levels of humidity, which in turn controls dust mites and mold growth.

Get these things right and then you can move onto the other things in the upside down pyramid, to help you cost effectively move to a more energy efficient home.

All these things are great and a complete no brainer when there are subsidies available, or if these things break and need replacing, Solar Panels and heat pump hot water systems, with subsidies can move further down the pyramid, from a cost perspective and they can also turn your home into a net contributor to the grid when you have your building envelope right.

Having done everything to seal and insulate the building envelope, you must now decide the systems to implement. If you have followed all previous steps your home should need minimal heating and cooling. You may only require: a small, efficient split system heat pump for winter and a few ceiling fans for summer. With bedrooms located on the cooler south side, and effective thermal design throughout, you can stay comfortable with less energy.

Additional considerations:

• Heat pump hot water systems are energy-efficient and eligible for rebates

• Mechanical ventilation systems maintain healthy air quality in airtight homes

• Solar panels, when paired with a well-designed envelope, can turn your home into a net energy contributor

With rebates available, some of these options move lower down the cost pyramid and become even more attractive.

By (Mr) Jan Brandjes

The answer is…  more than likely is a bit of everything.  You aren’t alone, many homes all over the world can suffer from overheating.

During summer, the upper floor of a two-storey building often experiences severe overheating and stratification because of the following:

1. Windows and skylights are primary entry points for heat energy, with bottom-floor windows also significantly contributing to overheating.
2. Insulation gaps of just 5% can account for 30-50% of heat loss/gain.
3. Downstairs heat sources like cooking, appliances, and halogen lighting heat transfer 20-25% upstairs, exacerbated by downstairs window-induced warmth.
4. Air Leakage: Throughout the building envelope, both upstairs and downstairs
   • Lack of draught stoppers in exhaust fans.
   • Open holes around ducted heating returns or outlets.
   • Internal cavity sliders connected to the roof.

A typical reaction of occupants, when faced with an overheating upstairs in a double storey home…

Abandon the second floor, and only cool downstairs. – The net effect: A greater temperature differential, exacerbated air leakage at the top and bottom of the building.  A large difference in temperature inside a leaky building creates greater pressures and air moving faster through gaps.

In winter, if you have an overheated upstairs, some people might try to close off ducted heating outlets upstairs.  This can aggravate air leakage via the ducted heating system and again, this will “NOT” help.  Click here for more information on this.

Heat will always find its way to the highest part of the house, no matter where the heat outlets are. A principle demonstrated perfectly by hot air balloons.

Solutions to reduce over heating

• Fix up gaps in your insulation.
• Make the building more airtight.
• Install a split system on the second floor to reduce temperature stratification.
• Add some shading to your windows in the west and east.
• Add tinting onto your windows.
• Install some ducts to transfer air from upstairs to downstairs with an inline fan.  (Avoid depressurisation induced air leakage in the ducts)
• Shade windows, upstairs and downstairs, stop heat absorption via glazing throughout the home.

Extreme solutions to reduce over heating

Separate the first and second floor entirely with the installation of a doorway at the top or bottom of a staircase.  After doing this it’s good practice to ensure insulation is placed in between floors, to contain thermal bridging. It could also be a good idea for each floor to have its own dedicated ducted heating system or at least zoned off area. When the ducted heating is used upstairs, the door must be opened to connect upstairs to the return inlet, otherwise air leakage is induced.

Extreme solutions for new builds

Installing a centralized ERV/HRV ventilation system, reduces stratification considerably, especially when combined with air tightness in the building envelope.

For an ERV/HRV system, ensure the building has:

1. Consistent insulation
2. An airtight envelope
3. Well shaded glazing
4. Alignment with passive house principles.

Overheating is a very common issue in Australian homes, especially in double storey builds, contact us for any queries on your home.

• 5% gaps in your insulation, can reduce the overall R-value performance of your insulation by 30%
• 10% would induce a significant 50% reduction.

So, R 3.5 in Melbourne could perform like an R 2.45 insulation installation.  Click here to understand what R-value, different materials have.

Table of minimum, required to satisfy R-values for construction assemblies. Ceiling and walls from the NCC 2016

Corner of ceiling insulation is missing under the ridge. These types of issues should be able to be felt with your hand. They can be fixed by putting a small hole in the corner and filling the area up with Expandafoam.

The first thing you can do, is put a respiratory mask on, some protective glasses and gloves, and have a quick look through your manhole using a torch to see any potential obvious breaks/gaps in your ceiling insulation.  Do not do this on a hot summer’s day.

The great thing about insulation issues is that it can be cheap to fix, and you may be able to fix it yourself.  There are some tools you can get to make troubleshooting easier and thorough.

• Temperature Laser pointer (Good)
• Thermal imaging camera (Best) Contact us for a consultation

If you can’t get a hold of one of these tools, you could use the back of your palm to feel for temperature differences.  Comparing a known well-insulated part of your ceiling or wall to an unknown or suspect area inside the building.

To find insulation holes, it will help to have a 10-degree temperature difference between inside and outside especially if you are using a low-resolution camera.  If it’s summer, it comes in handy to have a cooling source and in winter a heating source to achieve that 10 degrees temperature difference.  When it is hot outside, you will be feeling for hot surfaces and vice versa.

Recessed lighting hole around recessed lighting on a hot summers day.

Key areas to feel with the back of your hand to check insulation is in contact with the plaster:

1. Under roof ridges at the corners of the building
2. Around LED recessed lighting
3. Incandescent recessed lighting (Not much can be done to fix these unless the fitting is changed)
4. Around skylights Click here for information on this.
5. Around ceiling registers for evaporative cooling or ducted heating
6. Man-hole hatches
7. Above doors and under windows
8. Behind the cornice, where the wall plaster meets the ceiling plaster around the whole perimeter of the building.  This narrow area is typically exposed and uninsulated.

It’s important that the insulation is actually in contact with plaster because if air can move under the insulation, it will not work as efficiently.

Hole in insulation around recessed lighting.

Fixing insulation

1. Under roof ridges, where access is limited, foam-a-fill or expand-a-foam can be applied.  Drill a small hole into the plaster in the corner and pump a whole can into the area.  It’s beneficial to have a thermal imaging camera, handy while doing this.
2. With LED lighting, use a combination of IC rated LED luminaires and our downlight covers.  Be careful of Halogen lighting!  These ‘CANNOT’ be covered with insulation, under any circumstances.
3. For replacing old incandescent/halogen recessed lighting so that the luminaire can be covered, click here.
4. Install insulating foam board around skylight walls, using an adhesive.
5. Buy a bag of insulation to fill in areas that do not have insulation, cut out a square piece of insulation that will cover the utility hole hatch.  Use Foam-a-fill, only in small spots.  For example, don’t try and insulate a whole wall.  The pressure from the foam can push out plaster, and it would be impossible to run any services up through that wall again.
6. Push back tiles to fix perimeter insulation problems.  Place insulation or apply gun-grade spray foam, where the wall plaster meets the ceiling plaster.

Always work safely, and call a professional in to assist, if you are unsure about anything.  Perfection is key…

1. Can leak water, causing damage to your building.
2. Build up with dead insects.

Skylights transfer heat energy very efficiently. On a hot day,

• Solar heat from the sun is transmitted straight through a glass/old plastic skylight,
• A hot roof area also radiates straight through the un-insulated walls of the skylight,

The interior of the building is consequently heated and the cooling load that is required to keep the building temperature at a comfortable level. During colder weather, the heat inside the house rises and radiates/leaks through the design into the outdoors. Your ducted heating or split system runs longer and harder to compensate for this, increasing energy use.  The heat loss in skylights is more significant with a skylight than a facade window in a building because the heat in a room naturally rises and accumulates at the ceiling.  As an example, to understand this, in Australia, double story homes always get hotter upstairs in summer than the downstairs area.

Here are some quick and not so quick tips to get around the issues above so that skylights can still benefit your building.

• 

  SunTuf 8mm core flute Skylight replacement.

  When installing from scratch – Think about direction and exposure. A skylight installed in the south of a pitched roof gets more light than heat during most of the day. An east pitched skylight receives morning light and heat, while West pitched skylights get more heat and light in the afternoon. Heat gain issues can be reduced by shading the roof with deciduous trees that shed their leaves in winter or by utilising window roller shutters that can be manually closed or opened at peak hours of solar exposure depending on the climate.

• When buying new – Think very seriously about energy-efficient glass options. Similar to windows, skylights today offer glazing that reduces heat transfer in and out of the house while still providing acceptable levels of visible light and a clear view of the great outdoors. Some skylights have glass composed of “sandwiched” layers of glass incorporating argon gas between the layers to reduce heat transfer.  Low-emissivity glass is also available to diminish heat gain and loss.  Take size into consideration too, the smaller the gap, the less heat is transmitted.
• When Retrofitting. Insulate the skylight walls and install some Suntuf see through 8mm cor-flute plastic in line with your plaster building envelope.  This will give you a better R-value in between your living area and your outside skylight temperature.
• Remove your skylight altogether.

Send us an email if you need more information regarding the retrofit.

Thermal imaging: Energy loss through an old skylight in winter.  The cold breaching the insulated barrier.