Category Archives: General Knowledge

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How does Home Heat Loss and Heat Gains work?

Understand Home Heat Loss and Heat Gains

It’s that time of year again when everyone starts running down to the shops to buy a new heater. Very few people truly understand the fundamentals of home heat loss and heat gain and understanding this might save you in the long run.

The laws of Thermodynamics

No matter what you, if it’s 5 degrees outside and 30 degrees inside, the cold will always try and suck the heat out of the home. We go over the basics of thermal insulation in our recent article here, but in this scenario, cold air is always trying to sneak inside through every little gap, nook, and cranny in your home. This is a process known as infiltration.

The reverse is true where the hot air is also trying to escape through every crack in your home. This process is known as exhalation. If you think about it, it’s kind of like your home is trying to breathe both air and temperature in and out.

The total of all this air leakage is called home heat loss and is measured by a heat loss rate in Btu (British thermal units) per hour. The point of insulating your home is to provide a thermal barrier to slow or prevent this rate of home heat loss.

Understanding Home Heat Loss

If your home is poorly insulated or there is damage to your home, the rate of heat loss might be quite high. This means cold air is easily getting into your home and warm air is fast to escape out of it.

Dampness, mould growth, and difficulty heating up the home are several symptoms that reveal a lack of insulation.

On the other hand, a well-insulated generally has a low rate of heat loss. Insulation provides a barrier that means your home will better retain its heat while being more energy-efficient.

Understanding Home Heat Gains

Your home’s inside temperature is affected by the actual outdoor temperature and humidity levels. Home heat gains come from the outside weather, all your electronics, heating sources, and even the people who live inside. Unfortunately, on a very warm day, it can become very uncomfortable to live in and you want to try and remove all this excess heat.

Cooling systems work to remove unwanted heat from a space and relocate it. This is essentially what a heat pump is designed to do. By using an air conditioning process that takes advantage of the relationships between pressure, temperature, and volume, we can extract heat inside the home and redistribute it outside while replacing it will cooler and dryer air.

Uninsulated homes are very difficult to heat. Heat gain’s in these homes typically far exceed the rate at which you can efficiently cool it down. Insulating your home provides a thermal barrier that is just as effective in the summer as it is in the winter. Insulation will help work slow the rate of home heat gains making it far easier to cool down your home and control your inside temperatures.

Your home heat loss and gain weak points

Now that you understand a little more about home heat loss and home heat gains, it’s important to understand where the weak points in your home are.

For a typical kiwi house, your roof accounts for 40-50% of your home’s heat loss in the winter. The roof also adds between 50-60% of your home’s heat gains in the summer. Installing decent insulation in your roof cavity is one of the most important things you can do for your home. Luckily, most homes have a fairly good level of roof insulation although sometimes it’s worth looking at topping this up, especially in older homes.

Uninsulated walls are the next large issue area accounting for 30-35% of your home’s heat loss. They also contribute between 15-25% of your home’s heat gains. Building standards have traditionally not been very good in New Zealand. Many older New Zealand homes won’t have any wall insulation. A lack of insulation is the primary cause of damp walls and wet windows. We highly recommend you resolve this issue as soon as possible.

Next up are your windows, as much as 20% of your home heat loss and gain happens through your windows. Upgrading single pane glass windows and joinery to double glazing is a great way to solve this issue and fix this part of the home’s thermal barrier.

Finally, underfloor insulation can prevent as much as 10% of your home heat loss and gain. It’s not always possible to add underfloor insulation to your home. Homes built on piles provide a gap to install polyester blankets under the floorboards. This can help complete the home’s thermal envelope.

Talk to an insulation expert about your home heat loss and gain.

If in doubt, it’s always best to discuss your home insulation needs with an expert. Talk to the team at CosyWall Insulation today to find out more about how to fix your home heat loss and gain issues.

Safe Home in Winters - Wall Insulation

The Basics of Thermal Insulation

Thermal Insulation is an important part of every house and helps keep your house warm in the winter and cool in the summer. To understand how thermal insulation actually works however we need to take a few steps back and take a look at some of the science around heat transfer.

What is heat transfer and how does it work?

The first thing to know about heat transfer is that heat will always try and move from the warmest areas to the coolest ones, seeking a balance. In the home, the greater the temperature difference, the faster heat will try and flow into the coldest area. Research tells us that the three methods of heat transfer are conduction, convection, and radiation. Let’s have a quick look at these.

Heat transfer through conduction

Conduction refers to heat transfer at the molecular level within a certain material. The material might be a solid, gas or liquid but heat transfer happens when there is a temperature difference between two materials, and they come into contact with one another.

Molecules are agitated when heat is conducted from one particle to another. The rate of heat transfer will increase or decrease depending on the difference in temperatures between the two materials, and the thermal conductivity of these materials.

Heat transfer through convection

When a fluid, such as air or a liquid is heated and travels away from its source, it carries the thermal energy with it. This type of heat transfer is called convection. The fluid above a hot surface expands, becoming less dense and it rises.

A good example of convection heat transfer is a hot air balloon. A hot air balloon rises because warmer air is less dense than cool air. Since the balloon is less dense than the air around it, it becomes positively buoyant and rises.

Heat transfer through radiation

The final heat transfer method is through radiation. In this example heat actually travels through light, either as infrared light or other types of electromagnetic waves. The energy is freely transferred through a direct line of sight or through translucent materials.

A great example of radiation heat transfer is simply looking at sunlight. As sunlight impacts a surface it starts to heat up. If you’ve ever stood barefoot on a sandy beach in the middle of a hot summer’s day you’ll know what I mean here.

Different materials act differently to radiation heat transfer which is why some surfaces get hotter than others in direct sunlight.

So I understand heat transfer, how does this impact my home’s thermal insulation?

Really only convection and radiation heat transfer directly impact the home. That’s why thermal insulation is mainly designed to combat these types of heat transfer.

Thermal insulation is a material with a high thermal resistance value. Thermal resistance levels are measured by an R-Value. The material creates a barrier to avoid heat transfer between the inside and outside of the home.

So to better understand how thermal insulation works, let’s look at two different scenarios.

Thermal insulation for radiation heat transfer

Let’s say you’re in the middle of summer and your home has no thermal insulation in the roof. Radiant heat from direct sunlight at the hottest time of the year will cause the home to heat up.

This radiant heat will quickly pass straight through the roof and walls heating the inside air of your home and creating an oven-like environment inside.

Adding thermal insulation to your roof and walls means would stop the radiant heat passing through these surfaces, preventing the house from heating up as quickly.

Thermal Insulation for convection heat transfer

Let’s say you’re in the middle of winter and again there’s no thermal insulation barrier in your roof or walls. Naturally, you’ll put a heater on to try and warm the room. Unfortunately, because of the large temperature difference, the heat will quickly escape from the house however it can make it incredibly difficult and costly to keep the house warm.

After adding a thermal insulation barrier, heat will no longer be able to escape the house. This means that the heater will be far more efficient at warming up the home. It also means the heat will remain inside for longer, resulting in a far more energy-efficient home.

Talk to an insulation expert about completing your home’s thermal barrier

If you’re interested in adding thermal insulation to your home it’s best to talk to an expert. Our team will be happy to provide a free assessment of your property and provide advice and direction on the best way to fully insulate your home. Once your thermal barrier is in place you’ll notice the difference instantly.

What is a carbon footprint and why is it important?

You may have heard the term carbon footprint before but you may not be entirely sure what it means or how it applies to you. Simply, a carbon footprint is a measurement of how much extra carbon dioxide you are responsible for releasing into the atmosphere.

If you think back to a time before cars, planes and fast food, humans lived a much simpler life. A typical family lived in a house built of wood, cooked using firewood and farmed their food. These people contributed little to no carbon dioxide in the atmosphere and therefore did not have a carbon footprint. Everything that family would use and grow would be a part of the natural carbon cycle. This is the process where carbon is captured through photosynthesis and released again when living things respire or when wood burns.

Today, the typical human being releases about 4 tonnes of carbon dioxide each year. Different countries have different averages. The average American releases about 20 tonnes a year as opposed to the average Indian who releases only 1 tonne. All this extra carbon dioxide goes into the atmosphere and contributes to global warming. Cars, aeroplanes, how we heat and use electricity in our homes, the clothes and food we buy, our leisure activities and how we build and manufacture all produce emissions.

What changes can you make to lower your carbon footprint?

Individually we all need to be focused on reducing our carbon footprint by making smart lifestyle decisions and purchases. Here are some smart choices you can make to help lower your carbon footprint.

Insulate your home

Insulating your home is a great investment you can make in reducing your carbon footprint. Insulating your home makes it easier to heat in the winter and cool in the summer. Fully insulating your home by ensuring it has ceiling, underfloor and wall insulation helps complete your thermal envelope. This helps to separate the inside and outside air and is effective at stopping heat transfer in your home. Whatever energy you spend into heating or cooling your home will be retained longer and require less energy. Not only will this save you money, but because you are using less energy, you are having a positive impact on your carbon footprint.

Reduce the amount of time you spend in your car

Using your car every day burns through a lot of energy. Using a car powered by fossil fuel is particularly bad for the environment. Here are a few ways you can reduce your dependency on your car.

  • Try doing one weekly shop rather than heading to the supermarket every day.
  • Use public transport or try to carpool where possible.
  • If the option exists, try cycling or walking to work now and then.
  • Think about upgrading your car to an electric or hybrid vehicle.
  • See if you could work from home now and then.

Making a few smart changes to how you get around will help lower your carbon footprint even further

Make smart food choices

We all need to eat but making a few small changes to how, what and where we buy can also make a difference.

Most of us will buy the bulk of our food from the supermarket but how does it get there? Usually via big diesel trucks. Buying local produce means the food has to travel less to get to the supermarket in the first place.

Eating less meat is another great choice as it takes a lot of energy and grain for an animal to mature. That energy and grain could be used instead for human consumption. If everyone had a meat-free day even once a week it would have a significant impact on our global carbon footprint!

Washing and drying clothes

Your appliances use a lot of energy. Using your washing machine on a cold wash will significantly reduce the amount of energy it takes to clean your clothes. Hanging them outside to dry rather than using the dryer is another smart decision to lower your footprint. Buying the right appliances also makes a difference. Look out for energy labels when purchasing your appliances and make sure they have a high energy efficiency rating.

Change to LED Lights

You may not realise it but filament light bulbs are very inefficient. Only about 3 percent of the energy used is converted into usable light. Changing to LED bulbs will save on your power consumption as they are almost 100% efficient.


Recycling unwanted materials is also great as, while it uses energy to recycle and reprocess them, it takes less energy to reuse them than producing fresh raw materials.

Lets work together to make a difference

Living in New Zealand we can be a little bit removed from the effects global warming is having on our planet but even in recent years, we have experienced many severe weather events that can be attributed to global warming. The bottom line is that if we don’t make the right changes now, it will be too late.

Get an idea of your current carbon footprint by taking a short 5-minute quiz here.

The importance of closing your home’s thermal envelope

We’ve all experienced days when it’s ridiculously cold outside and it’s horrendously difficult to heat your home. Likewise, I’m sure you recall stupidly humid days in summer when it’s incredibly tough to cool the home down! This happens because the inside of your home is like a little atmospheric bubble, with air inside always trying to equalise itself with the outside temperature.

Your home’s insulation helps to provide a barrier that makes it difficult for air to escape from your home. It helps keep the inside temperature warmer or cooler for longer and helps to reduce the effort it takes to control the air temperature. In New Zealand homes, however, homes are generally only insulated to the minimum standards, which usually means a difficult and costly process for heating and cooling your home.

When you think about insulation, you usually think about the stuff they put in the roof and sometimes under the floor. What you may not realise, however, is that for most New Zealand homes there is little to no insulation in the walls and this creates a gap in your home’s thermal envelope.

So, what is a thermal envelope anyway?

The thermal envelope is a barrier created from all the different products and materials used in the construction of your house. This barrier helps protect the inside environment from the outside climate. Everything from your roof and concrete slab to your windows and insulation help to make up this barrier. Unfortunately, even the best-built houses often leave gaps or weak points that allow air to escape in and out of the home, with your walls being responsible for up to 30% of your home’s heating and energy loss.

If you think about it there are a lot of ways the air can escape through your walls. If your windows are thin, there are gaps in and around your doors, or if your walls are not well-insulated air can easily escape. The break in your home’s thermal envelope means that any effort you put into heating or cooling your house is quickly lost. However, there are things you can do to plug the gaps!

To remedy areas that could be a big part of the problem start with your windows. Replacing old thin window glass with new double-glazed windows helps to trap air inside, preventing it from escaping. Changing old wooden doors with better joinery can also help. The main issue for most houses however is the lack of wall insulation so, the best way to fix your thermal envelope is to ensure your walls are well insulated!

CosyWall Insulation is specifically designed to be blown into the walls of your home without having to remove the internal linings! The process is incredibly simple and an experienced installation team can usually have the job done in a single day. CosyWall Insulation is made up of loose cellulose fibreglass which is completely safe and poses no health risks to the family. It’s blown into your walls from either the inside or the outside through small holes which are then patched up and repainted so you’ll never know the process was done.

The insulation is blown at such a high density that it will never shrink or slump over time and with an expected 50-year durability, CosyWall Insulation will last the lifetime of your house! CosyWall has been installed in New Zealand homes for over 20 years and we have had countless customer testimonies advocating what an amazing difference it has made to their homes. If you would like to learn more about CosyWall Insulation just send us a quick message and one of our team will be right back in touch.

4 signs you should replace your home’s insulation.

Insulating your home is one of the best things you can do for your health, wallet, and investment. Just like anything though, it’s vital to ensure that it is up to date and installed correctly, so that you can reap the best benefits of home insulation. There can be serious health and financial consequences if your insulation isn’t performing optimally – if your insulation is old or ineffective, it will literally pay to find out.

Here are 4 signs that it may be time to look into replacing your insulation.

Changing Indoor Temperatures.

If the indoor temperatures of your home are constantly changing, that’s a sign that your insulation should be replaced. Well-insulated homes take a while to respond to outside temperature changes, as good insulation impedes the transmission of heat. If your home responds rapidly to temperature shifts, however, that likely means your insulation has thinned down. You might either need to replace it or add more.

Indoor Drafts

 When parts of your insulation wear down, the winds can exploit your homes new found weakness, and then you get a suction effect where wind pushes its way through the gap and sucks warm air out of the house so the cold can replace it. The draft you feel is this cold air muscling its way in and shoving your warm air out.

Out of control energy bills

 If your energy bills are fluctuating rapidly as the seasons change, that’s a sure fire signal that your insulation is becoming ineffective. If in winter, your heater is working around the clock and in summer your air conditioner is cranking 24/7, then usually your insulation is to blame. Cooling and heating systems are necessary to maintain a consistent level of comfort in your home and add an extra level of control over your house temperature, but they shouldn’t be working overtime.

Wet Insulation

 If the insulation become moist, damp, or sopping wet, there is no salvaging the material. It must be replaced immediately. Blocked vents, a leaky roof, a basement flood, or the absence of vapor barriers can cause crawl space or attic insulation to get wet. Not only can wet insulation grow mould that releases dangerous mycotoxins in to the air, but the moisture causes the insulation to become ineffective. The tiny air pockets that are instrumental in trapping the air and maintaining the temperature are plugged with water, rendering the insulation useless.

Insulation is essential in living comfortably. Having quality, up-to-date insulation will ensure your house feels like a home year round.

If you’re worried about any potential heating or cooling problems, get in touch today. Our technicians are happy to help make sure you have everything you need to stay warm this winter.


Can you have too much insulation?

As hidden as insulation is behind the walls, up in the attic and under the floorboards, its benefits are not so obscure! You probably know by now (especially if you’ve read our blog before) that the right amount of insulation can help reduce energy bills and improve comfort all year round.

The key words there are “right amount.” If your home is not properly insulated or installed, then you’ll have a much harder time reaping the benefits of saving money and staying comfortable. The question of whether “too much of a good thing” crops up when there are concerns of going overboard with sealing a house and potential problems with doing so, such as moisture build-up and mold to polluted indoor air.

A house can definitely be under-insulated but today, let’s dive into the question of whether your home can be over-insulated.

First, let’s start with the basics: how does Insulation work?

During the winter, the air inside the home is warmer than the air outside. The insulation slows down the movement of energy from the warm area to the cold area, creating a thermal barrier that means your heaters or fireplace don’t have to work as hard to keep the home warm. The thicker the insulation, and the lower the U-value, the better this thermal barrier is and so the slower the heat will escape the home.

During a summers day when the temperature may hit 30 degrees, the air outside is generally warmer than the air in the home. With the heating off, the house warms up gradually through the day as the walls and roof absorb the heat of the day. But because the air outside is warmer the thermal barrier created by the insulation will again slow the movement of heat, but in the opposite direction. Warm air in the roof will not be able to penetrate into the home as easily, whilst insulation in the walls will prevent them from warming the home as quickly as well.

What about air quality if the house is too tight?

It is important for your home to have good air quality – poor air quality can be hazardous to health. Not all insulation is created the same. Insulating your walls with vapour resistant insulation, like we do, reduces condensation that is caused when the moisture from daily activities, such as cooking, washing, and bathing gathers on the surface of your walls. It’s an effective way to avoid the harmful effects of moisture in your home.

Insulation is vital for your home

Wherever you live and whatever the type of property, insulation is absolutely vital – especially with spiralling energy costs! And while there are potential risks of over insulating your home if you choose the wrong installer, there’s a much better chance you don’t have enough insulation, particularly if you’ve noticed:

• Higher than normal energy bills (without an increase in usage)
• Drafts or uneven temperatures from room to room
• Unusually warm second floor in your home

Installing Cavity Wall Insulation

It’s vital when upgrading your insulation to get just the right amount and to ensure that it’s properly installed. The team at CosyWall Insulation has you covered in this area. We install the highest quality materials and always ensure you feel confident and comfortable in your newly insulated home.

Get in touch today for a free assessment!

Is all insulation the same?

We’ve mentioned before how insulation helps to reduce energy costs and keeps your home more comfortable. However, insulation comes in many different types, applications and efficiencies. It can be tempting to think that putting in some insulation will be a magic bullet, but it’s actually more complicated than that. Is all insulation the same?

Today, we’re going to look at the different types of insulation and whether they are all created equal.


There are 5 main types:

1. Batting (Fibreglass, Rockwool, Polyester): Batting comes in sheets and rolls to be cut and placed into roof cavities and under floors. It’s difficult to install in walls, except during construction. It can also release inhalant microfibres that cause respiratory issues. Also compresses fairly easily, reducing its effectiveness. It can be installed DIY, but as we’ve said before, there are complications there.

2. Loose-fill (fibreglass and cellulose): Loose-fill is blown into cavities to create a layer that settles. It’s lightweight, so great for unreinforced ceilings and walls, adding insulation but not too much weight. It’s easier to install in tight spaces, especially cavity walls which are notoriously under-insulated. For example, CosyWall insulation is water repellent and made from glasswool making it extremely useful in our New Zealand climate.

3. Structural insulated panels (polystyrene and polyisocyanurate): Best installed during building, as the panels cannot be squeezed into tight spaces. Offers great insulation, but can work too well, encouraging damp. Panels emit toxic smoke when burned. Polyisocyanurate is a foil-type insulation, which works extremely well, but because it’s a foil barrier, it tends to encourage damp by not allowing any movement of air or moisture at all.

4. Polyurethane spray foam (open-cell and closed-cell): Sprayed into cavities (requiring minimal access) and expands to fit all available space. Great for cavity walls and tight spaces, and can be installed in new builds or already finished houses. Open-cell stops the movement of air and closed-cell stops the movement of both air and moisture.

Each material has different costs, benefits, disadvantages, and R-value. The R-value is the thermal resistance it offers or its efficiency at regulating the temperature.


Basically, everywhere. Here’s how it works: air travels from one extreme to another, until all temperatures are the same. Insulation creates a thermal barrier that helps to slow the movement of air in both directions. So if you want to keep your indoor temperature stable, you need to have a well-insulated home. Warm air can escape through all of your home’s barriers. It’s important to complete the thermal envelope by insulating your ceiling, floor and — most importantly and most forgotten — your walls.


As you can see, all insulation is not created equal. It has different costs, benefits, disadvantages, health and installation concerns, efficiencies and effectiveness. Installed well and properly, insulation can reduce heating costs, prevent the growth of mildew and mould, and keep your home a comfortable and stable temperature and ensuring a healthy home.

If installed incorrectly, it can affect your health, be less effective at thermal control and encourage the growth of damp issues. Insulation also ages, compressing and creating holes in the thermal envelope. It’s important to update your home’s insulation especially if your home is old.

Not sure when your home was last assessed for insulation? Give us a call or email us call on 0800 267 992 or to chat, obligation free, about your home. And if you’d like to find out more about heat loss, energy savings, renovation and insulation, check out our other articles.