9 min 1 sec

Engineer Turns Home Energy Problem Into 15-Year, Million-Dollar Side Hustle

A construction engineer discovers how much energy is wasted by attics, creates a simple product that saves homeowners money, and builds a side hustle that earns more than two million dollars a year.
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What It's About

When the attic gets drafty, this engineer gets to building and creates a million-dollar side hustle in the process!

Business Model
Skills Required
Engineering & Design
Profit Potential

Words of Wisdom

Using feedback he’d received from customers, Mark created a handful of other energy-saving products. To this day, products that come from direct feedback are Battic Door’s best sellers.

Not sure how to expand your product line? Ask your customers—they'll be sure to tell you what they want!

Fun Fact

Believe it or not, the Battic Door website starting generating sales from Day 1. Mark had no idea how people were hearing about it without him doing any marketing, but he went with it anyway.

Notes from Chris

Episode 474
Let’s take a trip back in time: The year is 2002. The internet is nothing like it is today. E-commerce is really just starting to get off the ground. And Mark Tyrol is a construction engineer. He tests and certifies building materials—and he loves it. But there’s something he doesn’t love, a problem he sees all the time.


They’re never sealed properly, they always let in air from the outside, and they tend to cost homeowners hundreds of dollars per year in lost energy from heat or air conditioning... even if they don’t realize it.

Mark’s own attic wasn’t any different—and it really bothered him. So, one weekend, he created a foam cover for his attic stairs that would provide at least some level of insulation. Almost overnight, his electricity bill went down. It was so simple, yet so effective, and he knew he had landed on something that others would want.

So Mark started working on a website during nights and weekends. He wasn’t sure it would work—he was far more of a technical guy than a marketing one—but he figured it was worth a shot.

Being a construction engineer who dealt with materials on a daily basis, Mark had a pretty good idea of where to look to find a manufacturer for his product. He talked to a few in his area and signed an agreement with one: $5,000 for the first batch of product.

In late 2002, Mark launched his website (yep, 15 years ago) and new side hustle: Battic Door. The only product was his Attic Stair Cover, priced at just over $100. Mark called his friends, emailed the link to his coworkers, but really didn’t really do much else to market—largely because he didn’t know how.

And yet, somehow, Battic Door received its first sale that same day. Mark doesn’t really know how, but for the next several weeks he actually had a fairly steady stream of roughly 3-4 sales per week.

By the end of his second year, Mark was generating roughly $50,000 in sales annually. Using feedback he’d received from customers and fellow engineers, he’d created a handful of other energy-saving products. These products included a draft stopper for your chimney, shutter seals and covers, and even some energy efficient pet doors!

By the end of "Year 4," Battic Door was generating over $200,000 annually. In 2012, after ten years in business, Battic Door had its first $1,000,000 year. In 2016, the business had its first $2,000,000 year—and sales have hovered around there ever since. But despite the growth, Mark never left his engineer day job. He loves it.

The year is now 2018. The internet is used around the world. E-commerce has spread far beyond what most people could have imagined. And Mark Tyrol is still an engineer—still, but probably not for long. He’s beginning to crave more time with his wife and kids—and, thanks to Battic Door, early retirement from his day job is now on the horizon.


  • Battic Door: Leave drafty attics and windows in the past where they belong—get your upgrade over on Mark's website!

Inspiration is good; inspiration combined with action is better. Now get back to work!

Yours in the revolution,


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Quote of the Day
"You don't have to start a side hustle with the intention of making it your full-time gig—don't let the side hustle goals of others dictate your own. There's nothing wrong with enjoying your day job and saving up for an early retirement!"
—Mark Tyrol #SideHustleSchool

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Chris Guillebeau