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What are some DIY ways to increase the efficiency of a forced air heating system?

Please answer in Community wiki fashion: 1 tip per answer.

As @Jay Bazuzi pointed out, tips can also include ways to increase heat retention or other ways to save money on heating bills.


locked by Tester101 Dec 19 '13 at 15:22

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I think you'll need to tell us more about your house & climate. – Jay Bazuzi Nov 1 '10 at 17:26
@Jay Bazuzi: I'm just looking for general tips and trick, not ones specific to my situation. – Tester101 Nov 1 '10 at 17:54
Wanted to make this community wiki, but the checkbox is not available. – Tester101 Nov 1 '10 at 20:16
It's not obvious ... you have to Flag for moderator attention & ask for Community Wiki. I did it for you. – Jay Bazuzi Nov 1 '10 at 21:19
I still would like to see more detail and scoping in the question. Size of house, style of construction, fuel type. Do you just want to make the heat system more efficient? What about improving heat retention in the house, so you don't have to run the system as much? What about "put on a sweater"? – Jay Bazuzi Nov 1 '10 at 21:20

11 Answers 11

up vote 9 down vote accepted

Look for cold spots in your home. A room that tends to stay cold, despite your attempts to keep it warm is a signal of trouble. A nice tool for all such problems is the hand-held thermal sensor you can now buy, like this Black and Decker Thermal leak detector. Just aim it at a spot on a wall, ceiling, etc., and click the button. It gives you the temperature. Now move the sensing spot around, and look for cold spots. This can tell you if you have missing insulation in a wall cavity, or a spot of cold air entry into your home. Use this to decide to add weather stripping to a window or door for example, or to inject foam insulation into a deficient wall cavity, or simply to help you balance warm air flow through your heating system.

Note that the "Thermal leak detector" is just an infrared thermometer. Harbor freight version: harborfreight.com/infrared-thermometer-93984.html – James Van Huis Nov 3 '10 at 19:42

Not directly related to efficiency of the furnace, but...

  • Inspect around doors and windows for dry / cracked caulk. Remove and replace if necessary.
  • Inspect weatherstripping around doors and windows for signs of wear. Replace if necessary.
  • For older or poorly insulated windows, install plastic film insulation kits.
  • Inspect insulation in your attic/crawlspace (where possible). See here for a ballpark R value to shoot for. Add more insulation where applicable / possible.

Get a programmable thermostat if you don't already have one.

They are cheap, easy to install, and setting it up to turn down the heat a few degrees when you aren't home can make them easily pay for themselves in just a few months.

Do these really save money? In an empty room I have no doubt these really help save money, but in a room with couches and other items that retain heat/cold wouldn't the furnace have to work harder to compensate for the heat/cold released by these items? I'm no thermal dynamics expert, but it seems to me this is more complex then it seems. – Tester101 Nov 3 '10 at 19:18
@Tester101 - If you have the heat turned down for a while, yes, the furnace does have to work harder to heat the room when it is turned back on. However, that is more than made up for by the fact that the furnace wasn't running at all before that. – Eric Petroelje Nov 3 '10 at 21:01

Ensure all your ducts are properly sealed - you can use aluminium foil tape to wrap the joints and transitions. Don't use "duct tape" - it will get brittle and become worthless pretty quickly, and despite the name is not actually designed for duct work.

Insulate all exposed supply ducting - there are many DIY products for insulating your ductwork.

Ensure your return registers are clean so your furnace gets the proper amount of airflow, and make sure there is nothing blocking the combustion air to the furnace. And of course, make sure you have a clean furnace filter.

Funny how duct tape is good for so many things, except for wrapping ducts of course :) – Eric Petroelje Nov 1 '10 at 20:18
Quite an ironic name for such an otherwise handy product. – kkeilman Nov 1 '10 at 20:50
It was originally duck tape, because it sheds water. At least that's what my grandpa taught me. Wikipedia isn't so sure: en.wikipedia.org/wiki/Duct_tape – Steve Jackson Nov 2 '10 at 2:04
I was under the impression that it was called Duck tape originally because it was made out of cotton "duck" fabric. – Chris Cudmore Nov 2 '10 at 13:16
Mastic is a better choice to seal the ducts than tape. – Eric Gunnerson Nov 21 '12 at 21:32

The #1 easiest way - remember to change your filter.

+1, and keep your cold air returns unblocked, no rugs on top of them! – SqlACID Nov 1 '10 at 17:39
just did it last night ! thanks for the reminder !! – user45 Nov 2 '10 at 11:43
This, especially if you use something fancier than the usual fibreglass. Those super-duper electrostatic anti-allergen filters can get clogged unbelievably fast and should be checked weekly, especially if the system is running lots. – Compro01 Jan 3 '13 at 16:39

Keep your cold air returns unblocked, no rugs or furniture on top of them.


Install dampers to direct air flow to the rooms that need it most. This will help if you find yourself raising the thermostat to heat a bedroom, addition, basement, etc.


Neither DIY nor guaranteed to increase efficiency, but worth repeating:

Get your furnace cleaned and inspected by a professional.

They can tune your system and make sure you are burning at peak efficiency.

Does this hold true for electric furnaces? – Greg Nov 2 '10 at 18:37
@Greg: I don't know. My experience is with natural gas and heating oil. I'd guess it would depend on the model and the type of heating coil. Hopefully someone with experience will edit info into the answer. (which is why it's CW!) – yhw42 Nov 2 '10 at 19:08

Seal electrical boxes (usually light fixtures) in the attic, and use spray-foam on electrical conduit entrance holes.


Next time you repaint, pull off the baseboards on outer walls and use spray foam to seal the wall-floor gap.


If you are willing to spend a little money, get an energy audit. It will tell you where you home's biggest losses are, and point out many other places that could use a little work.

Good answer, but not really DIY. – Tester101 Jan 7 '11 at 19:51
If you really want to DIY, you could probably rent a thermal camera, but when I looked it was nearly as expensive. – Justin Love Jan 8 '11 at 20:37

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