Tag Archives: Thermal Comfort

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

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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

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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

Air Leakage + Thermal Bridges explained

Capture3Imagine it is winter. You wake up in the morning, put on your favourite hand-knitted wool socks and walk to the kitchen to have breakfast. But something is different today, your left toes are cold, you start to shiver and feel uncomfortable. What happened? The fabric on the toes has worn-out, there is even a little gap. The socks that used to keep your feet warm and cosy have a leakage and they are not able to keep you warm any more.

The same principle applies to a house. The building envelope’s task is to protect its occupants from the environment and to keep them warm. The building envelope needs to be a continuous shell, each little breach will negatively influence the overall performance and reduce the insulation’s potential benefits.

The following will explain where air-leakages in a building usually occur and how to prevent them.

Air-Leakage And Thermal Bridges

Thermal bridges and air leakages will increase the need of supplementary mechanical cooling and heating, but they will also increase the Relative Air Velocity and the Mean Radiant Temperature which will negatively influence the well-being and the comfort of the residents. By applying the right design features, natural ventilation and cross ventilation can be used to control indoor temperature and therefore reduce energy bills significantly. For these reasons, controlling the air movement is essential.

Read our next article if you want to know more about where air-leakage and thermal bridges typically can occur.

 

Thermal Mass and Heating Choices

thermal massIn most European countries, thermal mass is used as a matter of course. Although it takes  longer to heat up a house which contains a lot of thermal mass, it also takes a long time to cool down again. The thermal mass releases constant heat to the rooms and therefore heaters only need to be on a low setting or turned off completely.

Unlike in Australia, split systems and ducted heating are rarely used overseas as they use only convective heat. The main focus lies on radiant heaters as they heat thermal mass. The main form of heating in Europe is hydronic heating, mostly in form of hydronic heating panels, but also as in slab heating. Other sources of radiant heat are wood or gas fire places. Hydronic heating is also way more allergy friendly than ducted heating or split systems. But this is more the subject for a separate blog post.

If thermal mass is combined with effective insulation and has good solar access, the interior is perceived to be comfortable, without the need for additional heating, even if the external temperature is well below 20°C. The combination of thermal mass and well performing insulation is a condition of passive solar design, as well as low and zero-energy housing.

Conclusion
Thermal mass is an effective way to reduce the need for mechanical heating and cooling and to increase the comfort and well-being of the occupants. In order to perform at its best, it needs to be located appropriately and sized adequately, with a careful eye on insulation and thermal bridges.

Thermal Mass: material and colour selection

Material and colour selection

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Generally speaking, the more thermal mass the better and the heavier a material, the better its ability to store heat. The optimum would be a masonry home with a reverse brick veneer construction and concrete floors. Or using something like concrete block walls and insulate at the outside, with isolation boards.

If this option is too expensive use as much thermal mass as possible, concrete slab is preferable. In warmer climates the ground is colder and can help to cool the concrete. Therefore the indoor air temperature will be reduced. In colder climates, however, the concrete slab needs to be insulated from the ground in order to minimise heat loss in winter.  When looking a the energy start rating,  insulating the slab on ground can add up to 1 star to your star rating.

If a timber subfloor is requested or required, the focus should be at least on internal brick walls to the north which need to be exposed to the winter sun and are therefore able to absorb and release heat. Other materials that have a good thermal conductivity are water, sandstone, rammed earth and earth blocks, mud brick etc.

Moreover, colours and coverings can influence the performance of thermal mass. For example carpets and timber floors will minimise the ability of thermal mass to absorb and release heat as they work as additional insulation. This can lower the required heating in winter, but it will increase the need of additional cooling in summer, as the thermal mass can absorb less heat. On the other hand, hard floor finishes such as tiles, stone or slate on concrete slab can increase the ability to store heat. Dark colours or dark materials also tend to absorb more heat, however, light-coloured walls are more desirable as they maximise natural daylight. Dark walls will increase the need of artificial lighting, as they absorb light and can make rooms appear smaller. In short, material and colour selection can promote or adversely affect the performance of thermal mass.

One alternative to adding thermal mass as a actual building material is to add something that acts as thermal mass, but is light weight. There is one product on the Australian market, calle BioPCM. This phase change material acts as thermal mass, without the weight actual thermal mass has, and hence standard light weight construction and footings are sufficient, which are usually significantly cheaper than if you are building with brick and or block work.

“BioPCM™ is a lightweight smart thermal mass, providing design flexibility and easy installation for a cost effective and simple approach to integrating sustainable technology into buildings.
BioPCM™ absorbs excess heat during the day and releases this energy back in the evening as buildings cool.”

 

We have used the BioPCM to line the walls of a pantry, to keep it cooler and create some sort of cool – room. And the result was really great. The room always stays much colder then the rest of the well insulated weatherboard home.

 

 

Optimal Use Of Thermal Mass

How to locate thermal mass

optimal thermal mass
Thermal mass needs to be situated correctly and needs to work in combination with passive solar design and good performing insulation, otherwise it can have negative effects and even increase the need for heating and cooling. Thermal mass should be situated on the interior face of the building envelope and must be thermally separated from the outside via insulative materials.

Thermal mass should be located throughout the building to maintain comfort in summer, but the main focus should be on north-facing rooms. Good solar access is obligatory as the low winter sun needs to be able to enter the building and to strike the thermal mass. The more glass area, the more thermal mass is required.
Thermal mass is extremely important for multi-storey buildings, as warm air rises and therefore the rooms tend to overheat easily. Unfortunately most upper storeys are usually built in lightweight construction, as this is cheaper and easier to build. It is important, however, to incorporate as much thermal mass as possible, for example concrete floors or internal brick walls.

When using thermal mass in upper storey buildings careful attention has to be paid on the details. For instance that there are no structural thermal bridges, which can lead to unwanted heat transfer between the outside and the upper level concrete floors. But also the floors itself need to be insulated, to avoid heat rising up and heating up the upper levels. Insulating concrete floors isn’t a legal requirements, but highly recommended, if you do want to enjoy the thermal benefits and not the negative side effects of thermal mass.

In our next article we will speak about material and colour selections.

How can thermal mass help in Winter or Summer to regulate room temperature?

summer and winter

 

When deciding on what materials to use for your house many only think about factors such as cost and aesthetics. But when it comes to creating an energy efficient home the performance of a material and its ability to store heat needs to be taken into consideration. Thermal mass will help regulate the indoor temperature in summer as well as in winter and will reduce the need of mechanical heating and cooling.

 

Winter benefits

In winter, thermal mass works like a heater: it absorbs radiant heat from the sun through north, east and west-facing windows, and also stores heat from mechanical heating. The thermal mass will slowly release the heat which reduces the need for heating. Even when the heaters are turned off, the house will stay warmer for longer. Furthermore, the air and the exposed surfaces have the same temperature (Mean Radiant Temperature), which means there are no unwanted draughts, and the Relative Air Velocity is low; these will increase the thermal comfort of the occupants.

 

Summer benefits


Materials such as concrete and brick are cooler in summer than the surrounding air temperature, so they are able to absorb heat, which consequently lowers the room temperature and the need for additional cooling. At night the thermal mass will slowly release stored heat. Natural ventilation, via open windows, ceiling or exhaust fans, are an effective way to let cool air in and to let heat – collected during the day – out. In extreme hot periods, when it doesn’t cool down at night, air conditioning may be required to regulate the room temperature. The greater the difference between day and night temperature, the more beneficial the thermal.

 

Please be aware, that a standard brick veneer home will not give you any benefits for your indoor temperature, as the thermal mass is located externally, and separated from the indoor climate via insulation

What is Thermal Mass and why should we use it in construction?

thermal mass

Although the term ‘thermal mass’ is not commonly used, there are many examples where we experience it and appreciate its benefits. The most impressive is the ocean: in winter, when there is less sunshine and the average air temperature is low, the water is chilly and only the tough ones might enjoy a swim! In spring, the sun will slowly heat up the water so that finally in summer it will have a comfortable warm temperature. Water has a great capacity of storing heat – it will stay constantly warm during day and night, and even in winter, it can be significantly warmer than its surrounding air temperature due to its ability to absorb solar energy. Water demonstrates the principle of thermal mass. How does it apply to construction?

 

Thermal Mass, Why Is It So Important for Construction?
Thermal mass is the ability of storing and releasing heat to help retain a constant indoor temperature. It is an effective way to improve thermal comfort in a building and plays an essential role in saving energy. Thermal mass inside a building will absorb heat when the surroundings are warmer than the mass, will store the heat and radiate it slowly when the surroundings are cooler. It can actively be used to regulate temperature, therefore, reducing the need for mechanical heating and cooling. Heavy materials, such as concrete and brick have great thermal storage capacity, whereas lightweight construction materials, such as timber and insulation cannot store heat. Generally speaking, the heavier a material the better its ability to store heat.

If you want to know more about thermal mass please also read our further articles about this subject.