Tag Archives: Thermal Comfort

Why is Insulation so Important?

insulation 1

Thermal insulation is a fundamental factor to achieve thermal comfort for occupants. Insulation reduces undesirable heat loss or gain and can lower the energy demand on heating and cooling systems.

Insulation is the most effective way to improve the energy efficiency of a building, as it acts as a barrier to heat transfer.

It will keep the house warm in winter and will help to stay cool in summer, improves thermal comfort and well-being, and minimises condensation on walls and ceilings. Furthermore, insulation needs to be combined with appropriate shading devices to windows and adequate ventilation possibilities, otherwise heat entering a building through windows will be trapped inside by the insulation and lead to overheating.

Older houses in particular pose a problem: inadequate insulation, poor solar access and air leakages amongst other things lead to unwanted heat gain and loss, and consequently higher energy bills.

Adding insulation to a home can save 45-55% of mechanical heating and cooling needs and as a result, save non-renewable resources and reduce greenhouse gas emissions. With the current energy prices, additional insulation usually pays for itself in around five to six years. With the prospect of rising energy prices it’s more than likely that insulation retrofitting will pay off even quicker.

Thermal Comfort and Star Ratings

Thermal Comfort and Star Ratings

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As explained in our previous article: the perception of temperature is more important than the temperature itself, when it comes to comfort.

In Australia, energy rating assessments are done pre-construction, assuming competent application of all insulation and building materials as well as draught sealing all wall penetrations.

However, common construction practices often demonstrate misapplications and air leakages. Sadly, although there are regulations in place on how to install insulation and how to seal of wall penetrations, there is no one really responsible for checking all those details, neither the builder, nor the architect, nor the building surveyor. In fact, some tradies even take out insulation, so that they can work easier around cables, fixtures and fittings and don’t bother to put the insulation back in. For sure, as soon as the plasterboard sheets are one no one can even see the problem.

This means that although in theory the house should be energy efficient, the reality will be far from that. It will be draughty inside. Cold air can come in. The energy bills will be way higher than the energy rating did predict. And, as explained in our article about thermal comfort, it will be hard to feel comfortable inside your ‘well insulated’ home.

In Europe, energy efficiency is most often assessed or checked post construction, with special attention to the prevention of thermal bridges. Some countries require airtight buildings, and amongst other things, double glazing, solar energy for hot water and heating systems, the usage of storm water, greywater recycling, recycled materials and product life cycle considerations to minimise energy demand and carbon footprint.

Conclusion

A good star rating, well performing insulation and building materials are not a guarantee for well performing homes and for feeling comfortable inside the house. The building envelope needs to be treated as a delicate continuous shell. Each small gap and leakage will impair the energy efficiency and the well being of the occupants. It is essential to consider the end product in order to determine how energy efficient a building really is.

What Factors are Influencing Thermal Comfort ?

What Factors are Influencing  Thermal Comfort ?

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Carlos Gali Photography
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If insulation applied is faulty or insufficient, the exposed surfaces in a room will stay significantly colder in winter or hotter in summer than the room temperature. Although the heater pumps hot air into a room, or the air-conditioning blows cool air, the thermal radiation will affect the equilibrium. The Mean Radiant Temperature is affected negatively and the occupants won’t feel comfortable.

  • The ceiling isn’t insulated or the insulation is penetrated for example because of the installation of down light. As warm air is always moving upwards, heat is lost to the cooler air in the roof space.
  • Air leakage around doors, windows, down lights, pipes, and other wall penetrations are exceeding the acceptable Relative Air Velocity.
  • Wrong application of thermal mass can influence the Mean Radiant Temperature and can therefore increase the need of mechanic heating and cooling.
  • Under- performing windows and doors (when air is able to leak in/out of poor fitting doors and windows) are also influencing the Mean Radiant Temperature and the Relative Air Velocity.

When it comes to comfort, the perception of temperature is more important than the temperature itself.
For a person to feel comfortable, the difference of temperature between the head and the feet should not exceed 2.5 degrees. This demonstrates the importance of floor insulation and this explains why we usually feel more comfortable standing barefoot on carpet than on tiles.

Do you want to know more about the basics of Thermal Comfort, please have a read through our article What is Thermal Comfort?

What is Thermal Comfort?

What is Thermal Comfort?

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Human thermal comfort describes the state of mind that expresses satisfaction with the surrounding environment and refers to several conditions in which the majority of people feel comfortable.

The human body produces heat depending on the level of activity, and expels heat according to the surrounding environmental conditions.

The body loses heat in three main ways:  radiation, convection and evaporation. An unpleasant sensation of being too hot or too cold (thermal discomfort) can distract people from their activities and disturb their well being. This may reduce the ability to concentrate and decrease motivation to work. Thermal comfort is affected by six variable factors which are needed to maintain a healthy balance in order to sustain satisfaction with the surrounding environment.

1) Air Temperature is the most common measure of thermal comfort and can easily be influenced with passive and mechanical heating and cooling.

2) Mean Radiant Temperature is the weighted average temperature of all exposed surfaces in a room. The greater the difference between air temperature and exposed surfaces, the greater the Relative Air Velocity.

3) Relative Air Velocity (‘wind chill factor’) is the apparent temperature felt on exposed skin due to wind.  For example, if cold air is leaking in from a window, the air temperature feels lower than the actual air temperature, hence the increased likelihood of feeling cold, even when the heater is on.

4) Humidity or relative humidity is the moisture content of the air. If the humidity is above 70% or below 30% it may cause discomfort.

5) Activity Levels can reduce the heating needs, as lower air temperature is acceptable when occupants have higher activity levels.

6) Thermal Resistance of clothing or warm blankets in a bedroom can reduce the need of heating.

Building design is affected by the first four of these thermal comfort variables. The last two depend on the action and behaviour of the occupants.

Do you want to know more about thermal comfort? Then have a read through our article what factors are influencing thermal comfort.

How Much Insulation Is Needed?

climate zones

In short: the more the better:

The Building Code of Australia (BCA) identifies eight different climate zones for Australia, but within a zone, there are some locations with slightly different temperature ranges. There can be significant differences between maximum and minimum temperatures in summer and winter and in length and intensity of heating and cooling periods. The house design, the insulation and construction must respond to these variations in order to be able to perform energy efficient.
For simplicity, Victoria is divided in five climate zones, with winter heating as the predominant concern especially in the Temperate Coastal and Cool Inland Zones. Summer cooling is variable but generally less significant. House design in these zones requires attention to better performing insulation, draught proofing, window protection in winter and shading in summer. Likewise, in warmer cities and areas like Mildura supplementary heating is obligatory for thermal comfort. In these regions, it’s advisable to include extra thermal mass, cross ventilation and summer shading, whereas alpine areas may require constant heating for most of the year and cooling requirements are negligible. Consequently, a 6-star home in Mildura wouldn’t comply with the minimum requirements for a 6-star home in Ballarat.

The higher the R-value the better the performance. Consider what insulation is needed in order to build an energy efficient home in a certain climate zone early in the design process. In particular, it’s important to think about the roof insulation. For example, it would be cheaper to use larger rafters in order to fit in sufficient glasswool to fulfil the desired R-value, instead of using thinner expensive extruded polystyrene. Larger rafters would mean that the overall height of the building rises slightly. This is no problem, if the amendments are done early in the design. However, if a town planning permit has already been granted, it’s not that easy any more. It’s necessary to go back to the council with the changes, which can cost a lot of time and money, therefore in most cases, people choose to use the thinner, more expensive insulation instead.

Adding R1.0 insulation can significantly improve the energy efficiency. For example in Melbourne, adding insulation with a R-value of R3.0 to the ceilings and R1.5 insulation to walls can save 12% on energy bills each year and can ensure a higher level of comfort.

One important thing to consider is that the energy requirements as listed in the BCA are minimum requirements only, not best practice. So if someone is telling you to not put any more insulation in as the regulations call for: don’t listen to them. They don’t have a clue.

If you put in anything less, your building would not comply, so if you are after an energy efficient home, why would you be happy to only have the legally required minimum? Rather put in as much insulation as fits into the wall/roof/ or wall and as much as your budget allows.

Keep in mind, while it is quite easy and common to upgrade bathrooms and kitchens every 10-20 years, you will typically not touch the insulation again. So make sure you make your home future proof!

Infrared Thermal Imaging to detect Air-Leakage and Thermal Bridges

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Whereas a blower door test can test how air tight a building is, infrared cameras are not able to give you an actual performance or score of your house, but they can show you where thermal bridges occur.

In Europe, infrared cameras are often used to locate the misapplication of materials and resulting thermal bridges. The lighter the colour the warmer the materials, the darker the colour the colder the materials. Great differentiation between colours means great temperature difference.

The first picture below shows a typical German home. Although double glazing and thermally improved window frames are used, the windows have a lower U-value than the walls, as the required U-value for the external walls is 0.24 W/(m²K) and the U-value for the windows 1.10 W/(m²K). Expectedly, the windows present in a darker colour as they let more heat escape through them than the walls. Determining if a thermal bridge is within the allowed limits requires meticulous measurements and comparison of internal and external material and air temperatures, humidity levels and following calculations of heat transfer. In this particular case, the thermal bridges occurring due to different U-values are within the allowed limits.

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Stack-Effect and Clerestory Windows

stack effect

Stack-Effect

The term “stack-effect” goes back to the chimney. The heat source – in this scenario, the fire – heats up the air. Hot air rises and is discharged through the chimney, as it has a lower density than cold air. This effect can be used to replace air inside a house. For instance, when it’s colder outside the windows can be opened to let in cooler air. Warmer air inside the room will rise towards the ceiling, exiting via high openable windows, clerestory windows and skylights. Warm air inside is replaced by fresh and cooler outdoor air.

Clerestory Window

clerestory is a usually a high wall with a band of narrow windows along the very top. The clerestory wall usually rises above adjoining roofs.

Originally, the word clerestory referred to the upper level of a church or cathedral. The Middle English word clerestorie means “clear story,” which describes how an entire story of height was cleared to illuminate large interiors.

If you want to maintain wall space AND keep a room well-lighted, or if normal solar access is either not possible or restricted consider this type of window arrangement for your home. Clerestory windows are most often used to naturally illuminate large spaces such as sports arenas, transportation terminals, and gymnasiums. But can be a great addition to any home.

 

The Role of Ceiling Fans & Exhaust Fans

 

ceiling fans

Ventilation is the active process of “changing” or replacing air to regulate temperature and moisture. It should always occur under controlled conditions, by opening windows or with ceiling or exhaust fans, NOT through gaps and air-leakage.

Exhaust fans

Exhaust fans should always be self-closing, so that the replacement of air is controlled and not accidental. With out a self closing mechanism they are one of the main contributor of air leakage.

However, if they are self-closing they are an effective way to replace air, especially in rooms where no natural ventilation is available, or where natural ventilation might not be sufficient, such as kitchens or bathrooms.

Ceiling fans
Ceiling fans are an easy and cost effective way to improve the indoor air quality in summer and also to gain points towards the desired energy rating stars.

Ceiling fans provide additional air movement/wind, increasing the Relative Air Velocity (‘wind chill factor’) resulting in the apparent temperature felt on exposed skin to be 3 °C colder than the actual air temperature, thereby reducing the need for additional cooling.

Nowadays there are so many efficient fans available on the market.
If choosing a ceiling fan make sure you get one with at least 3 speeds, with the lowest speed being slow enough to still move air, but not to create a cool feeling draught, so that you can use them in winter mode)

 

How to locate air-leakage and thermal bridges

hp photosmart 720
hp photosmart 720

Draughts + air-leakage
Older style buildings commonly have draughts and air-leakages due to unsealed windows and doors, and unsealed vents and exhausted fans, therefore, heat and air can escape. It is difficult to control the air movement. Other sources for draughts are gaps within or around insulation, vented skylights, gaps between floorboards, open fire places, around air conditioners and heaters, gaps around other wall penetrations, such as down lights, pipes, cables etc. .

Thermal bridges
A thermal bridge is an element or part of a building, which allows heat to travel through it more quickly than through other parts and is therefore responsible for unwanted heat loss or gain. A thermal bridge arises for instance when poor insulative materials touch each other, when gaps occur between insulative materials and structural surfaces, and when materials with different R-values/U-values come in contact with each other. These thermal bridges allow heat transfer from a warmer to a cooler material. The main thermal bridges in a building are located at the junctions of floor to the wall, wall to the roof, balconies and window and door frames.

How to locate draughts?

– Are there any visible gaps? For example is light coming through gaps around windows and doors?
– Are blinds or curtains moving when the windows are closed?
A lit candle can be used to check air movement, such as around windows and doors, vents, floorboards, junctions of floor to wall and wall to roof connections