DIY Heatmap "Infrared Thermal Image" using the Black and Decker TLD100

For this, you'll need a Black & Decker TLD100 Thermal Leak Detector or equivalent, your digital camera or a picture of the surface in question, a pen, and an Excel Spreadsheet (or equivalent). This is the "low tech" heatmap.
Take a picture of an outer wall in your house (one where the opposite side is the outdoors). Print it out and draw a grid so you have about one foot squares (here's a picture of our family room with the Holiday trimmings and detritus). Here, I used Excel (version 2002).
By selecting "Format -> Sheet -> Background" and selecting the picture, you can have the picture in the background. This comes in handy if you lose paperwork frequently too. Print out the picture and start taking readings for every square. You'll want to be no more than a couple of feet from the place you're taking the readings so you can get accurate results. Unfortunately, I can't currently get the background to print, so I took a "snapshot" of it (press and hold the control button and press "Print Screen", then open a paint program and paste it in there).

Now that you've made your DIY heatmap, take a look at the differences. You'll see that near our Christmas tree, there's a big difference. This is a chimney wall where (eventually) there'll be a wood stove or pellet stove, but right now, it's a big heat sink!

Okay, so now you have a picture with a lot of numbers on it. Looks confusing and messy, yes? Here's a trick in Excel that will help you better visualize what's happening:
Select all the numbers in your spreadsheet by clicking on the upper left hand corner and dragging down and to the right to where the last number is on the lower right-hand corner.
Under the "Format" menu, select "Conditional Formatting".
Condition 1 will be "Cell Value Is" "Between" 1 and 58. You can look over your numbers and see where the low point is, then select a number a couple of degrees above that.
Click the "Format..." button to the right, and use a dark blue color for the font. Click Okay.

Click the "Add..." button in the lower portion of the dialog box. Condition 2 will be "Cell Value Is" Between" 59 and 64 or what ever your middle average temperatures are.
Click the "Format..." button to the right, and use a dark green color for the font. Click Okay.

Do the same with the high end, choosing a dark red color for the font. Click Okay, then Okay again. Your numbers should now come up in color! Too bad there's only three conditions.

You can fiddle with the conditions in Excel to make it look more appealing, even leave ranges alone (skipping the 65-70 degree range so those fonts stay black, and having 71-90 red, etc.). But what we're looking for here is the disparities. There's one other disparity which is around an electrical outlet in the lower right hand side. That will take a little more than Superman powers, but it's good to know there's a draft from there.

Instead of getting fancy like I did above, you can always paste a picture next to the spreadsheet, as illustrated below. Here, all you have to do is go to the menu bar, select "Insert" -> Picture -> From File... and choose the picture. Resize it and set it next to the heatmap, and it prints, too.

You can do more on your own without paying for a professional home energy audit and save yourself hundreds of dollars by following the comprehensive "Home Energy Audit handbook" by Dave Anderson. He gives you a comprehensive guide, several excel spreadsheets (not like the one I described here), and solutions to the "heat thieves" and energy losses that are in your home.

You can rent thermal imaging cameras by the day/week or month. Prices range from $299/day up as of this update, but it's always worth a look if you have the means, or if you're a contractor and want to "wow" the customer with this technology. Do a search on "thermal camera" rental .
Another way to maximize your $ would be to get several neighbors together and split the rental fee. Make a day of it, be sure the one who is taking the pictures is the designated driver as well. Get the pics from all of the houses, then send it back (be sure the d.d. is the one that packs it back up too!).