Seal your fireplace from draft

Your fireplace acts like a big chimney...OK so that may seem obvious but do you really know how much your leaking up there? According to the Department of Energy, a lit fireplace sucks about 24,000 cubic feet of furnace heated air up the chimney every hour. This sounds dramatic but, the real problem is how much is sucked up 24/7 right through the damper. And if that wasn't bad enough in most fireplaces there is a vent in the back that allows fresh air in to help feed the fire which is usually left open.

There are many solutions to fix this problem and they all depend on what your willing to do and or live with. Probably the easiest is to shove some insulation up the flue and close the vent in the back. This works fine if you never use the fireplace. If it is a gas fireplace then simple framed glass door unit will probably do the trick. But if you plan to burn wood, you probably want something a little more accessible when you do have a fire going.

Here is a good do it yourself project that is fully functional for burning wood or duraflame logs. The last project I simply used a lock-top chimney cap which worked great. This project I had fireplace and chimney that was outside the house and a small vent in the back of the firebox. This lead me to finding a solution to seal the front of the fireplace just like a window to the outside. This way I could simply leave the vent open.

1. I first removed the faux brass glass door unit that was in place exposing the bare open fire box. Shut off the gas at the farthest place possible to the unit and then remove the gas logs. I found a local metal shop and had some u-channel and had 4 pieces cut to fit the opening perfectly. We purchased a tri-fold fireplace screen unit from Pottery Barn Outlet. Measured the doors to fit the opening exactly and then pop riveted to the back of the u-channel. This completed the fire screen part of the project. Now we had a safe screen with doors for easy access.

2. Next I purchased some lexan from Home Depot along with some hardware to complete the energy saving part of the project. I cut the lexan with a rotary speed saw to fit the opening exactly. Measured where the handle would go, drilled carefully through the lexan. (Helps if you drill on top of a piece of wood.) Once the handle was in place checked to make certain the fitting was exact to the other side of the u-channel and then applied the velcro both to the lexan and the u-channel. After everything was completely installed I sealed the u-channel with mortar on the backside to ensure no draft was getting through.

After getting it installed I grabbed my smoke pen to see just what kind of draft was pulling up the chimney. I wonder how much money was climbing the chimney every day. Now the images below show the proof in the pudding so to speak. The 2 thermal images side by side show with and without the lexan cover in place. The darker color represents colder air inside the empty fireplace.

To improve energy efficiency for an existing home, thermal images from an energy house inspection or home energy audit will reveal many of the leaks in the thermal envelop. After the review you will have a roadmap to proper weatherization. Whether you are the do it yourself, "DYI" person or want to hand off to a contractor or handyman, the roadmap will help you make the best decision first. Fixing whats found will greatly improve your comfort, savings and reduce your carbon footprint.

important tip - Do not put the lexan in place while firebox is hot!

Questions about this project, contact Brent at This e-mail address is being protected from spambots, you need JavaScript enabled to view it

For a great link on everything you need to know about fireplaces, click here.