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We have a large fireplace and plenty of free or cheap wood and love having fires for warmth and entertainment. An open fireplace is not an ideal source of heat, but I wanted to know if there's a relatively simple way of increasing the amount of usable heat we get from the fire.

We're in a rental property, so a permanent installation such as a wood stove or fireplace insert is not possible.

I've seen a couple commercial solutions, such as this Texas Fireframe or fireplace heat exchangers, but I have no idea if these actually make a difference. I've also heard that just putting a cast iron plate at the back might reflect some heat back. Is there something I can put together myself with some Home Depot supplies?

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  • If you really want to increase the heat and efficiency, then a wood stove insert is going to be the way to go.
    – Glen Yates
    Apr 7, 2022 at 18:30

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I almost passed on this question, but couldn't resist.

I have been involved in a lot of home energy audits lately. Having spent a lot of time with some very qualified experts, i've learned a lot.

The one thing about a conventional fireplace is that they are for looks only. Even if the wood is free, it is costing you heating costs every time you light it. The real story is that for the chimney to draft properly and not fill the house with smoke, it has to pull tons, yes really tons, of air from the house to feed the flue. Only about 40% of the heat generated by the burning wood is actually sent into the house. The majority is sent up the chimney, as flue temps can reach 600 to 700. In order for this hot air to escape, it pulls the warm heated air from your home. So in essence, you are trading 40% efficient heat for the paid for heat at maybe 80% to 90%, depending on your heating system. Not a good trade, huh?

My advice is not waste your money on gimmicky promises of high efficiency gadgets. Just enjoy the fire as a romantic mood setting with a glass of wine, but don't forget to close the damper as soon as the fire is out to save your heating bills!

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    And please, please, dispose of the ashes carefully. There have been several homes burned to the ground in our area due to improper disposal of fireplace ashes.
    – TomG
    Jan 17, 2012 at 23:59
  • Ash disposal: put the fresh ashes in a metal container. Let it sit on a non-combustible surface until completely cooled. It could be days, as ashes insulate coals well. (My mom once put ashes in a plastic bucket on the carpet. Burned a hole to the subfloor, but no fire, whew)
    – Jay Bazuzi
    Jan 18, 2012 at 0:07
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    I'll never forget when my brother sucked up a hot ember off the hearth with a Kirby vacuum cleaner and the bag exploded!!!!! WOW, what a mess.
    – shirlock homes
    Jan 18, 2012 at 10:55
  • I once vacuumed some thought-they-were-cooled ashes. It was a very old-fashioned canister vacuum, i.e. all metal parts except the bag. My mom ended up sewing a new bag for the vacuum, but it still smelled like smoke for many years after that. Needless to say, it was relegated to shop or outdoor use.
    – Martha
    Jan 18, 2012 at 19:15
  • Thanks for weighing in. I know a conventional fireplace is a totally impractical source of heat, and I've heard that it can actually be a net loss, as you say. But the wood is free and I love having a fire, so my question is really this: given that I am going to have a fire 3 times a week, is it worth it to spend a little money to buy a fireback or a grate to recoup some of my heat losses?
    – Hank
    Jan 20, 2012 at 16:39
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The item called a "fireplace heater" is the best option. I have seen them used, and have actually built one myself. I have experience as a welder so it was not a real chore to do. Several steel pipe are bent to conform to the dimensions of your fireplace, with the bottom of the "C" lying flat against the bottom of the FP. The top of the "C" should fit along the top of the fireplace, and should extend out the front of the FP a few inches.

As the heat in the FP increases, air along the floor, cold air, is drawn into the pipes, heated and forced out the top openings, putting heated air into the room. There is not need for electrical, or power of any type.

Adding a "blower" can increase the heat output significantly. Manufacturers of these type units actually measure the output, in ranges of BTU/hr in the 40,000 to 90,000 Btu range. That is a lot of heat and will warm a large area. 'Fireplace heaters" can be seen online and on the appropriate web sites.

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My in-laws picked up something similar to this grate a while back for their fireplace. The theory behind it is that by properly structuring the burning logs and embers, you can help direct the output of the heat more into the house than up the chimney.

I haven't tried it myself (as I have a woodstove), but they've noted an increase in heat in their living room since getting theirs.

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  • I've seen these grates in action (in a person's house) and definately outputs more heat.
    – Jon Raynor
    Jan 17, 2012 at 22:30
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If your fireplace has a chimney that pokes into the room, try to figure out if it gets warm when the fire is lit. If so, you can blow air onto the chimney breastwork with a fan to distribute that heat into the room.

Alternately you can run a ceiling fan to try and move heat down from the ceiling area which is space that people generally aren't occupying. Warmed air moving gently is different to the radiant IR heat from a fire, so you can be warmed twice.

For an enclosed wood burner, a fan can blow across the top to help spread heat around the room.

Separately, consider the quality of your wood. If its manufactured wood, high in glue then don't even bother burning it. You're just releasing glue compounds and asking for a chimney fire. Resinous wood can do similar, albeit slower. "free" wood may not be worth burning at all if it is rubbish.

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If you make one, use 2 inch tubes 4 inches apart, welded to a flat plate across the back and at the bottom for the grate to sit on with the upper part of the tubes angled at 30 to 45 degrees upwards and extending forward towards the front of the fireplace. You can remove it and sell it if you leave the house

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