Why the caulking gun (and the thermal imager) are the best weapons in the war against energy waste

window
CC BY 2.0 Lloyd Alter

We have said it many times: sealing your house gives you the best bang for your buck. Take a tour of my house with a thermal camera for a real demonstration of what I mean. We're planning a renovation, downsizing and subdividing our hundred year old Toronto house and don't want to rip out the plaster and the lovely old windows, but do want to tighten it up a bit. Our contractor, Greening Homes, brought in a Flir thermal camera and the results were shocking. In the photos above, you can see that the single-glazed bathroom window isn't too dark, 11.9 degrees (all in celsius). But look around the window casing: air is pouring out around it, with some parts of it below freezing. No wonder we get out of that bathroom fast.

Greening homes/CC BY 2.0

It's often cool in the bay window with the piano; sometimes too cool for my wife to even practice.

Greening Homes/CC BY 2.0

You would think it is coming from the bay windows themselves, and it is true that there is quite a bit of hat loss there,

Greening Homes/CC BY 2.0

But the real killer is at the baseboards, where cold air behind the brick wall falls down the space between the lath and plaster and the floor and spills out there. It's zero celsius, the freezing point. Inside the house.

greening homes/CC BY 2.0

The insulated steel door is doing a fairly good job of insulating, but look at what is leaking on top of the frame, it is actually blowing upward. That's why replacing windows and doors is pointless or even counter-productive if the trades don't do a good job of installing the frame and sealing it properly.

Greening Homes/CC BY 2.0

If this was the ceiling of the top floor, you might expect this kind of leakage around an electrical box. In fact, there is another occupied floor above this. The cold air is travelling from the brick wall at the end, between the joists, and falling through the electrical boxes.

Greening Homes/CC BY 2.0

The electric and cable outlets here might as well just be holes in the wall.

Greening Homes/CC BY 2.0

This is a great shot, you can see the cold air pouring out and oozing down between the floorboards.

Lloyd Alter/CC BY 2.0

Now the wind isn't normally blowing through our house as if we were in a canvas tent; there is a giant blower putting the whole house under negative pressure. They are trying to figure out how many air changes there are per hour at 50 pascals of pressure differential. They never got there; the house was so leaky that the fan didn't have enough punch, and it only got to 45 pascals, at which point there were18 air changes per hour.

What's the point?

A lot of people have been convinced that there is nothing they can do to reduce their energy costs other than gut the joint and insulate everywhere, or change their windows. The fact of the matter is that most of the heat loss is through leakage, and if you can cut that down with effective use of caulk and minor repairs, you can save a bundle with an investment with a payback period that you can measure in months. This exercise with the thermal camera showed that the windows were performing almost as well as the eight inch thick brick walls!

But the biggest shocker for me was the fact that I have been ritually caulking my windows every fall for a decade, but because I didn't have the camera, I didn't know that the leaky window trim was a far bigger source of heat loss. If you don't know where the heat is going, you don't know what to fix.

Lloyd Alter/CC BY 2.0

That's why I thought the Flir One, introduced at CES, was so exciting. I don't know how renovators and architects lived without these things.

Tags: A Picture Is Worth | Green Building | Insulation | renovation

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