In our Newsletter back on March 6th entitled ‘Beware of Standard Practices’, I described some of the challenges we were having getting the builder to properly insulate and air-seal a house that I designed for a friend of mine near Mittagong. The house is finished now and it has turned out really well. It is basically two open-plan versions of the Greeny Flat that my friend will use, one for their house and one for their yoga studio. Here’s a recent picture of the finished project (there’s still more landscaping to do).
In order to allay any concerns that my friend might have about the quality of the insulation (as described in the Newsletter mentioned above) I offered to examine the house with an infrared (IR) camera to make sure it was at least as good as the Greeny Flat. For three years when I lived in Montana I had the job of performing energy audits on houses including IR testing so I know my way around an Infrared Camera. The trouble is that the one I used in the states cost about US$5,000. Luckily, another good friend of mine recently bought a $400 FLIR Infrared Camera attachment that simply plugs into his iphone and he offered to lend it to me. I was pretty keen to give it a try so I borrowed it, along with Cintia’s iphone, on a nice cold morning at the beginning of this week.
Infrared Camera Testing Basics
IR testing works best when there is maximum difference between the indoor and outdoor temperatures. This is when you can most readily see where heat is being lost so a cold morning is a good time for IR work. In the following images, warmer surfaces appears lighter and cooler surfaces appear darker. So, for images taken inside the buildings, lighter is good anddarker is bad (in terms of heat loss) because it shows cold areas where heat is being lost to the outside. For images taken from the outside the opposite is true… lighter areas generally show where heat is being lost to the outside. However there are some traps to watch out for… for one thing, reflective surfaces like glass or metal can be tricky because they sometimes reflect the heat signature of something other than their own surface. Also, as you’ll see below, some of the warm surfaces on the outside of the buildings had nothing to do with heat loss from the inside. This is where some experience with an IR camera can be useful, otherwise the results can be very confusing. So what did we find?
One of our main areas of concern was the quality of insulation in the SIPS roof panels of the new house (see this Newsletter for more information on SIPS panels and this Newsletter for the reasons why we were concerned with the new ones). To summarise, there were gaps between the new panels that looked like they might allow heat to escape. So I started by taking the image above of the Greeny Flat roof which didn’t have gaps between the panels and compared it to the following image of the new roof.
To start with it is important to disregard the difference in colour between the two images above. This is due to the fact that I was using a certain setting on the camera that adjusts the colour according to the warmest and coldest surfaces in the image. The important things to note are that, a) the temperature of the two ceilings is almost exactly the same and b) there are no dark lines in the middle of the new house’s roof. If there was heat loss at the joins between panels we would be seeing dark lines running up the ceiling at each of the panel joints and we are not. This is great news. So what are the dark lines around the edges? These appear in both the Greeny Flat roof and the new roof and they are due to the nature of SIPS panels.
SIPS Panel Basics
As you can see in this previous Newsletter about them, SIPS panels are structural panels consisting (in our case) of an interior skin of flat metal glued to 150mm of polystyrene foam glued to a corrugated metal exterior skin. So the underside is made of a sheet of flat metal that crosses over the exterior walls from inside to outside. This allows heat to conduct through the metal from inside to outside and there’s really nothing you can do about it if you use SIPS panels. I have heard of people cutting a groove in the lower skin of the panels where it sits on the exterior walls but to my mind this would completely compromise the structural integrity of the panels and is a VERY bad idea. So, if you use SIPS panels (and I still think they are almost the only way to go for Cathedral ceilings for reasons outlined here) you just have to accept that there will be a small amount of heat loss around the edges of the roof. When you compare it to how much heat is being lost through the double-glazed windows in the IR image of the Greeny Flat above, I think you’ll agree that it is not a major concern.
In the Greeny Flat we used double-glazed windows with aluminium frames (not thermally broken because those were too expensive). In the new house we used mostly wood-framed, double glazed windows except in the wet areas where we used aluminium frames for durability. It is interesting to note how much more heat can be seen escaping via the aluminium frames than the wood frames in the two images below.
It’s also very interesting to notice how much more heat is being lost through the single glazed panels of the front door of the new house compared to the double glazed windows on either side of it (see below).
The other thing that amazed me when I first saw the image above was that I could see exactly the height of water in the downpipes. But I’ll come back to that. First I want to complete the discussion of windows by showing you what the single-glazed windows on the neighbour’s house looked like that morning.
Back to the downpipes… the new house has what’s called a ‘charged’ downpipe system. This means that the downpipes are partially full of water all the time. It was really surprising to me to see how much warmer the water in the pipes was than the rest of the exterior of the building. This is due to fact that water has a lot of thermal mass. It is a good conductor and holder of heat. Check out the following image that shows the water in the rainwater tank too. For this reason, an IR camera can be a very useful tool for finding water leaks and moisture problems in buildings.
Thermal Mass Basics
Now we come to my favourite images, the ones that show the Thermal Mass at work. Readers familiar with this website will know that, in a Passive Solar Designed house, the Thermal Mass (in this case the concrete floor slab) acts like a heat store, absorbing heat from the sun during the day and radiating it into the house through the night to keep the place cosy and warm. Keep in mind that these images were taken on a morning when it was about 4degC outside and before the sun came out for the day. So the warmth you are seeing was absorbed the previous day and stored right through a fairly cold night.
In the image of the Greeny Flat floor above you can see that the warmest part of the floor, where the sun was shining on it the previous day is still radiating 21degC the following morning. You can also see how the slab gets colder towards the outside edge because we did not insulate the edge of the slab nor did we put any insulation under the slab. Compare this to the floor of the new studio in the following image.
In the image of the studio floor above you can see that the edge of the slab is not significantly colder than the rest of the floor. This is because we insulated the edge of the slabs in both the new house and studio. However, if you look very closely you can also see a pattern of large, cooler squares showing through the slab. This is due to the insulated ‘waffle pods’ that were placed under the floor when the slab was poured. There is a lot of debate as to whether or not it is better to insulate under floor slabs (as discussed in this previous Newsletter) in this climate. If I were building in Montana or putting any form of heat pipes or wires into a floor slab then I would definitely insulate underneath it. However in most of Australia’s mild climate regions I don’t think it’s necessary, in fact I think it might be better to have the thermal mass of the slab connected to the thermal mass of the earth beneath it but I have no scientific evidence to back that up. I find it interesting that you can see the waffle pods in the IR image above.
In the image of the new house above you can’t see the waffle pods underneath because the stored heat from the wood stove is making the floor glow like a bed of coals. I generally don’t recommend wood stoves unless, as in this case, it has its own air intake. This stove in the new house has a pipe the brings fresh air from outside directly into the combustion chamber. Without this pipe the fire would suck all the warm air out of the house. With the pipe in place the fire does a great job of radiating heat to warm the house, including the floor slab which stores some of the heat overnight as you can see above.
The image above shows the insulated slab edge of the new studio. Notice the line of heat escaping below the bottom of the insulation? This is due to the fact that the landscaping and paving hasn’t been completed yet. Once completed the paving will be quite a bit higher than the existing ground level and most of that heat loss will be buried underground. Compare this to the edge of the floor slab in the Greeny Flat below.
In the Greeny Flat we did not insulate the slab edges (for termite barrier reasons) and you can clearly see how much more heat is escaping through the edge of the floor slab. You can also see how much more heat is escaping via our aluminium window frames compared to the wood windows in the studio above.
Also for comparison sake, the following is an image I took at the same time of the old house next to the Greeny Flat on which we are preparing to perform a major energy retrofit as described in this Newsletter from a few weeks ago. Notice the heat loss through the single-glazed windows, the eave vents and the effect of the thermal mass of the fireplace down the left hand side of the image.
Finally, and just for fun… when I got home from my visit to the new house and studio I happened to glance at our electric car with the Infrared Camera. You can image my surprise and delight when I saw this…
Because it was a short trip I had driven the whole way there and back on purely electric power so the engine hadn’t heated up at all. In fact the only things glowing were the tyres from the heat generated by friction on the road. Great image isn’t it?
Thanks for reading… more next week.