Guest blogger Tom Harrison is the CTO of EnergyCircle.com.

Many people think, “My house is cold and inefficient. I need to insulate!” But there's something far more important to do first. If you had a puffy down coat, it wouldn't work unless you zipped it up, right? So zip up your house by sealing leaks and drafts.

I learned the hard way. When we moved into our New England house we couldn't keep warm in winter.

So we thought: insulate!

It seemed obvious. We filled our walls with blown-in cellulose insulation. But next winter it was still cold.

So we thought: windows!

It must be the rattling, single pane windows with cheap aluminum storms. We got out the checkbook and bought fancy “low-e,” double-glazed windows. But next winter: still cold.

So we thought: furnace!

Clearly our massive 1940s gas furnace with gravity-fed hot water heat can't be good. We dipped into the savings account and got an efficient new burner with circulator pumps. Next winter...only a little better.

So we thought: Stop thinking! Start learning!

I found Energy Circle and learned about energy audits. A pro tests your house. The “blower door” measures how much air leaks through your house. Infrared cameras "see" heat to pinpoint leaks and cold spots. The auditor provides a report, with pictures and specific things to fix. Our audit cost $400.

We had a very, very leaky house. Our culprits were a whole house fan, the chimney, basement bulkhead door, the sill around the house, and numerous leaks. Worse: The fancy window installers didn't caulk! Our first insulator missed a bunch of spots. Grumble.

Fixing was quick, painless, and inexpensive (there are many energy efficiency rebates).

The contractor used the auditor's report to see where he should seal the bigger drafts with foam. He also filled in missing insulation. I bought a Chimney Balloon, made a cover for my house fan, and sealed the bulkhead door.

Then: caulk, baby, caulk!

The energy auditor re-tested (even then, he found a few places I missed); now the house is much less drafty.

Now the insulation works. Now the windows keep heat in. Now the boiler heats the house quickly and it stays warm. Now the house is comfortable in winter and summer. My heating bill plummeted.

(And as it happens, it was through the audit that I now work at Energy Circle!)

Zip up your house! It's the first step to keeping heat in or out. All the other stuff matters once the house is tight.

--Tom Harrison

Image: lululemon athletica via Flickr