When adding a fireplace in your old home or building one in your new home, you might want to consider making sure your fireplace is pretty but also efficient. I spent 20 years in an electronic test laboratory and I learned a tremendous amount of information from each of my engineering and maintenance coworkers that were experts in different areas of construction, energy, electrical, plumbing, etc. If you are going to spend good hard-earned money, I hope you consider having it or building it to its maximum usage.
Consider your design carefully. You should border the outside fireplace with brick or stone. If you prefer not to, then discuss your options and possibilities with a contractor or someone with the experience and know how. Whichever you choose is fine.
Now consider what your mantle will look like and design it. I recommend having a step up hearth. The hearth can cover a tunnel that will carry outside air to the inner floor of the fireplace. In addition, you can sit on it in winter and feel the warmth of the fire (See Diagram 1). If you are building one in the center of your home away from an adjacent outside wall, get an opinion from a reputable source or contractor on how to get outside air to your fireplace. In the following steps, I will explain the justification for this outside flow of air.
Buy a HeatilatorÂ® insert for your fireplace or ask your contractor to order one. There are many different designs and you can pick one that suits your needs and design. You can Google www.heatilator.com . The purpose of a Heatilator is to use the fire to draw cool air and pass it through a few tubes/round ducts. It then distributes it back into your room as another heat source.
You also need to purchase a typical glass door enclosure for the front of the fireplace. This will help to isolate the heat without the flue drawing the warm air from your room defeating the purpose of the HeatilatorÂ®. When you shut the glass doors, there is no air to keep the fire going. This is the reason for the hearth and the outside-tunneled airflow. Make sure that the outside air tunnel has an opening (louvered vent) in the bottom of the fireplace floor. You can regulate the vent to properly keep the air flowing and the fire burning nicely.
On both sides of the fireplace, there are two (2) vents. One is located near the bottom above the heath, and the other is located above but not too high above the opening of the fireplace (See Diagram 2.) The bottom two (2) vents have fans powered by a wall switch on the room wall. The fans draw the cool air through the bottom vents and push hot air out the top. Now you have a fully functional extra source of heat.
With the idea of energy saving for additional heat, here are a couple of things you need to check and do. It will actually increase your hot air flow. Remove all four (4) vent covers. Stick your hand in and check if the four (4) vents are open and not blocked with insulation from the HeatilatorÂ®. If they are, push and stuff it aside until the port is flowing properly. Sometimes accidents happen as were in my fireplace vents. It reduced the airflow tremendously until I found the problem.
Now that we have sufficient airflow, you can increase it and make it even better. The mason builds the vents with concrete block. Inside you can feel and see the sharp 90Â° turn. There are two (2) different types of airflow, one that is marginal (turbulent) and one exceptional (laminar). Turbulent airflow is always inconsistent and often restricted while laminar flow is steady and very smooth. With a sharp 90Â° elbow inside the vent (See Diagram 3), you will get turbulent airflow. As you can see from the diagram, this is definitely not very efficient. You have restrictive airflow twice, once below and once above. When the air hits the wall before the turn, some of it collides with the wall and travels backwards, reducing the airflow velocity. The familiar analysis of the restriction is termed as reverse or negative airflow. Just for added information, you measure airflow velocity in cubic feet per minute (CMF.)
You solve the reduction of airflow velocity in this manner. Get some sheets of metal (I used brass.) You can use galvanized or something similar as stove piping for venting. Cut the metal to the exact dimensions of the opening and path of the vent. Make it long enough so it creates a curve at the 90Â° angle bend and make sure the height is tight against the upper and lower part of the vent. If you cut it too low, the curve will not stay in position. You have now made the vent capable of producing laminar airflow without any more restriction (See Diagram 4.) When you are done with all four (4) vents, turn on the fans and you will see an amazing difference in the velocity. Finally, if you are lucky enough to have an anemometer, you can measure the CMF increase from the original installation to the final stage.
If you are building a fireplace, you may consider another option. If your design is a heavy one, a contractor can support the fireplace in the basement by building a block wall. In my case, I had two (2) fireplaces back to back but staggered. The rectangular structure had a large void in the center. I told the contractor to put in an iron door at the bottom for ash removal. Inside both fireplace floors, I told him to put in another small rectangular door that I can open and sweep ashes down into the void below. If you think about it, I am sure you will not fill the void below in your lifetime. This makes it better than sweeping out and trying to dispose of the ashes by walking through the house and creating dust clouds.
You may ask your contractor to put in a second or third (as in my case) flue for a future wood stove when you finish your basement. Besides, it is always better to do it now than do it later resulting in a more costly expense.