Heat Your Home with Less Wood
Another year, another blink of an eye, and summer has already evaporated. As the wildflowers begin to thin and the days start to shorten, autumn will be marching breathlessly to our doors in the coming month, with winter hot on her heels.
I know you’ve enjoyed your summer – your tan lines are still fresh, your garden is lush and fruiting – I know you don’t want to let go, but my friend, colder days are coming anyway. How are you going to stay warm this year?
Energy usage for home climate control makes up a massive chunk of the monthly electric and propane bills, and takes a toll on the environment. For those of us with wood burning stoves, the summer is a frantic flurry of activity as we haul and split load after load of wood, stacking as much of an overabundance as our backs can carry in anticipation of a cold season yet to come.
The whole process is cyclical, and regardless of how you heat your home, incredibly demanding of energy. Maybe you see it in a bill you pay every month, maybe it’s written in the creosote in your chimney and the callouses on your hands, but one way or another, we all seem to pay a steep price to last the winter in comfort.
So how do we find the balance between a cleaner way to heat our homes, and also saving on costs?
Wood burning stoves are undeniably cheaper in terms of cost to heat your home, but they release a large amount of pollution, and their design isn’t very energy efficient to boot. A large portion of the heat generated by your fire is going into the chimney – and where does that chimney go?
Straight up and out of your house, taking the majority of the fruits of your very hard labors with it. That hot smoke is producing valuable BTUs – don’t let them go to waste.
Rocket mass heaters take advantage of all of that heat being released from the exhaust, and instead of sending it out into the cold, wind and meander the piping throughout your home, typically in a big beautiful thermal mass.
By the time that smoke is released outside, it’s incredibly cool, and is much cleaner, resembling steam more than it does smoke. Your home stays warm longer, and doesn’t heat up like a sauna all at once when you get the fire roaring.
The coolest part about a rocket mass heater though is likely the fact that it uses up to 90% less wood. This type of wood stove also is a bit unique in that the wood box isn’t your standard vertical affair – rather, the fire actually burns sideways in a rocket mass heater.
It’s a thing of beauty, but the draft produced by the core that keep the smoke from backing up into your house is also pulling at those flames, so that you have what looks like a rocket thruster blasting off in your living room.
From the wood box, the fire is pulled up and into a super insulated heat riser, housed within your standard steel drum, many of which can be salvaged and cleaned up for use for next to nothing. The barrel remains exposed, and acts as a source of radiant heat, while the exhaust goes undercover within a thick thermal mass.
To understand why rocket mass heaters work as well as they do, you need to understand what a thermal mass is and how it works.
Basically, a thermal mass is just a dense material that, when heated, holds onto heat energy and very gradually radiates it back out. The benefit of this is that your fire will continue to heat your room long after the flames die, because your thermal mass is going to be holding onto that heat for hours and very slowly releasing it.
Think of it like a battery, only instead of a crazy concoction of chemicals as your energy source, you have the smoke from the fire you’re burning a few feet away, which is also producing heat.
The whole system is so beautifully efficient, it’s a wonder this design concept hasn’t caught on in a widespread, very commercial sort of way. While trailblazers like Ernie and Erica Wisner continue to publish fantastic resources, like their latest book The Rocket Mass Heater Builder’s Guide, others continue to conduct experiments and call for more innovators to make rocket mass heaters accessible for all.
If you’d like to learn more about rocket mass heaters and get a glimpse of them firsthand, check out Paul Wheaton’s latest project, Better Wood Heat: DIY Rocket Mass Heaters, the 4 DVD set. You’ll actually get an up close and personal look at two different types of rocket mass heaters – pebble and cob-style.
The most important thing to take away from this is that, yes, you are playing with fire quite literally when you build your own wood stove, but it absolutely can be done. With plenty of research, planning, and even some hands on work (if you can get in on a workshop), you can build your own rocket mass heater, and heat your home for one tenth of the wood you would normally use, with no electrical or propane input whatsoever.