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The importance of insulation and some common issues is best shown using a case study. The example below illustrates how heat transfer occurs in a house. Actually heat transfer occurs anywhere and everywhere where there is a temperature difference between two objects and it flows from objects with higher temperature to lower, until both temperatures are equal. We say that warm air rises up or cold air flows down. In winter we say that cold enters the room or heat escapes or leaks. In summer heat enters room/house or warms up cool air. No matter how we call it, it is the same process and the same principle of heat transfer. Sometimes we like it, like direct sun in winter warming up rooms. But most of time it works against us and it is unwanted which is why we are doing what we are doing to slow it down - insulating, sealing gaps improving air circulation. It is important to understand that we cannot completely stop this process, even the best insulated and sealed house will continue to transfer heat in our out until it becomes as cold or as hot outside. Some houses will reach the temperature outside almost instantly, others might take long time. Making our houses keep the comfortable temperature as long as possible is what energy efficiency of our houses is about.    

The picture on the left shows thermal image of a room taken on a cool winter day. There is an air conditioner in the room which has been working for a while and a fan (not turned on).  The lowest temperature in the room is 14.7 degrees which is the temperature of the aluminium frame of the sliding door in the centre. The highest temperature in the room is 36.6 degrees which is the temperature of the air as it comes out of the air conditioner. The path is shown by white dotted arrows. The air is blown to approximately centre of the room and as it loses the momentum it raises to warm up the ceiling. Grey dotted lines show the "wake" of the warm air and the wide angle means that the heater is operating in swing mode   

Temperature gradient.

The temperature difference between the highest and lowest point in this room is is quite high, 20 degrees and the comfortable temperature (around 21 degrees is at 1.8m height). Because we spend most of our time in the lower regions under 1.5m, ie sitting or lying, this room will feel rather cold despite the heater working. We can see is as the entire bottom half room is in blue colour. To improve the comfort we need to force better circulation so the warm and cold air can mix better. We can do it by running the heater at higher fan speed or using the fan. Ceiling fans are most effective in winter because they push the warm air down to lower regions. 

It is also important to be aware of temperature gradient when setting up the desired room temperature. The thermostat is usually inside the heater. Sometimes, with ducted heaters, it is in the control pad mounted on the wall. So we are setting the temperature not at the height we want it but at the height it is monitored/detected by the thermostat and to get it right we need to adjust the setting accordingly.     

Windows and blinds

We can see 3 single glazed windows with vertical blinds. 1 & 3 is a sliding door with one half exposed and only partially closed blinds. Window 2 has open blinds and window 4 completely closed. Looking at window 1 and 2 we can see that they remain cold even though the temperature inside is much warmer at this height. This means the cold enters the room as single glazed windows are not much of a barrier to prevent it. Windows 3 and 4 show the importance of window covering, the blinds are pretty much room temperature (and from 1 and 2 we know what it looks like behind them). Vertical blinds are not the best there is, there are still leaks around the edges (see yellow arrows and green streaks on the surface) but they are much better than nothing. A more efficient option is heavy drapes, tight fitting around the sides and to the floor with pelmets on top. And with double glazing the windows 1 and 2 would look exactly like 3 and 4 even without closed blinds. This is because the sheet of glass on the inside would be insulated from the outside sheet by the gap between them. For more information on double glazing click here

Lintel insulation 

Lintels are timber or steel beams inside the wall immediately above all openings. They redirect the weight of the roof or wall above door or window to each side. Because of additional beams and timber holding it in place these areas are often not as easy to fill with insulation as the rest of the walls and so they leak the heat in or out. Once the plaster and external cladding is on they are not easy to fix so best if lintel insulation is checked at building stage (see areas circled in yellow).   

There are 3 different issues with insulation in this room. 

Ceiling insulation

The picture on the left shows some missing ceiling insulation, around the fan (1), in the corner (2). The ceiling in those areas is quite cold despite the high temerature of the air at ceiling height. The air is hot enough to show the fan in red but without the insulation, the heat just leaks into the roof cavity. We are not sure what happened in the corner, but the insulation around the fan was most likely displaced during fan installation as tradesman removed it to gain access but "forgot" to put it back in. Another issue, though less obvious, is that part of the heater's wake is yellow rather than orange-red (3) so the ceiling in this area is cooling down faster than in the rest of the wake. This could mean that there is less insulation there or the insulation is not working for some reason ie compressed or wet which should be investigated further. Correcting ceiling insulation issues is a relatively easy task as there is usually sufficient access to those areas.  

Edge/corner insulation. 

Corners, wall to floor and wall to ceiling joints are usually poorly insulated, as indicated by yellow arrows. Because they run through entire perimeter of the walls, floors and ceilings, these leaks can add up to substantial amount of wasted energy. With access to those areas they are relatively easy to fix by extending ceiling/floor insulation over/under the walls. But because the way the walls are made, the leaks in wall corners can only be fixed from the outside by removing external cladding to gain access - which is a major job when not done during building stage (before the house is wrapped and clad outside).  

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