Easy Savings - Run Your Dryer on Free Energy




Modify your electric dryer to use free hot air and save energy.

Dryers only have one hose fitting. - To blow hot air out.
But this Instructable shows how to create a dryer hood with a fitting for a hot air intake hose.

Once the hood is attached, you connect the dryer to your hot air source with a dryer hose, and use free energy - hot air- to dry your clothes.

On hot summerdays , I use it to take hot attic air right into the dryer in my cool basement.
On warm days I use the air dry or the low temperature "Permanent-Press" setting.
In winter I use my dryer normally.

You can use your attic, a warm room, a solar heater, or you can use outdoor air as a source of warm or hot air. (The source of warm or hot air should be drafty, or open to a source of replacement air, like the outdoors.)

This Instructable helps you avoid consuming your indoor air, it makes your dryer more efficient, it saves energy on drying, and It can save on air conditioning cost too.

This Instructable is intended for electric dryers only, and is NOT recommended for gas models.
Modifying a gas model would present special challenges and hazards, which I have not addressed.

Material : Use a 4 foot roll of Aluminized Bubblepack plastic (Astro-foil) or similar material, a scissors, duct tape, plus scrap metal or cardboard and a dryer vent hose. Thats all thats needed. A screwdriver is optional.

Step 1: Unplug and Inspect

Unplug your drier , remove the exhaust vent hose, and inspect your Electric drier.
Look for the slotted vents in the back.

Step 2: Remove the Back Cover - Optional

Step 2: * Optional *
Loosen or remove the back of the dryer to inspect your dryer.
I studied it for a while so I felt comfortable making this modest modification.
I confirmed that the one main source of air was through the slotted vents.

Replace the back panel loosely. Tighten it later.

I suppose this modification could work on a gas model, but I'd worry about a mistake that would interfere with the proper combustion and exhaust. I'd worry about a potential fire hazard too.

I was careful with my electric dryer and happy not to mess with a gas model.

The photo shows the air intake on the bottom right, and the exhaust on the left.

Step 3: Sizing & Shaping the Hood

Begin planning and sizing the shape of the hood. Cut a large piece of material. Trim and shape it as the project processes.
I used aluminized bubble pack from a hardware store.

The photo shows the first rough cut.

Step 4: Begin Taping the Material to the Dryer

Start applying the material to the dryer to surround but not cover the intake air vent slots.
Start to trim the material and tape the edges to the dryer.

Step 5: More Duct Tape !

Apply the material to the back of the dryer up to the vent slots. 'Do not cover the vents!'
Tape both the inside and outside edges to the dryer.

Continue to Shape and trim the Material to fit around the shape of the air intake vents.

Step 6: Create a New Vent Hole

Use cardboard or other stiff material to form a vent hole. Make it big enough to accommodate your duct hose. Fix it to the top of the dryer.

I used a 6 inch diameter scrap sheet metal vent duct, and tucked its thin edge between the dryer and the back panel, and tightened the screws on it.

I was lucky to have a machine made part. If you do not have one, carefully construct one of the right size and shape.

Step 7: Slit the Hood Up the Middle

Create a slit up the middle of the hood, to create an overlap. This tapers the shape of the hood from large at the top to smaller at the bottom.

Use scrap cardboard to create a rigid form to help the bottom of the hood keep its shape. I used a piece of 1/2 inch thick rigid foam insulation instead of card board.

Tape the rigid form to the hood and dryer.

Step 8: Finish Shaping and Taping the Hood

Tape the inside and outside of each edge and seam, and where the hood joins the dryer..

Continue trimming and taping the hood to the Dryer.

When Possible, fold the edges of the hood between the back panel and the dryer, and screw the back panel in place tightly. You may need to reach inside the hood to reach the screws in order to tighten them. I was Glad to have a 6" vent hole to reach into the hood, and the sheer size of the hood made it easier to work in.
And I made it plenty big enough for air to flow in easily.

Finish by wrapping the material around the duct hole.
I made several "Daisy Petal" cuts to help wrap the material around the vent hole.

Make sure the vent hose fits snugly inside the duct hole.
Finish for looks and functionality.

If you are going to use tape on visible parts of the dryer you might want to pick up some White Duct Tape for a nicer look.

I spent time being neat and careful, and I think it paid off.

Step 9: Test It Out

Re-attach the original exhaust hose.

Plug in the dryer and turn it on to test the air flow to make sure its working properly.
Making sure the hood allowed air to easily enter the dryer was a major concern I had.

I used an incense stick to create a visible stream of smoke.
This is looking good.

Step 10: Almost Done - Hook It Up

Run one end of the hose to your attic or other source of hot air.

I strung it up in our drafty attic, near the peak of the roof, where it gets very hot on summer days.
Its not dusty up there so I did not install a filter at the end of the hose.

Insert the other end into the dryer hood.

Put the dryer back in place.

Step 11: Results and Performance

On a hot day I can dry my clothes on the "Air" dry setting. This means the dryer is not consuming electricity to make heat.

On warm days I use the high heat cotton setting or the lower heat permanent press setting. Either way, I know my dryer is getting a boost, because its heating up warm air, not cool air, and its not taking nice cool indoor air and blowing it to the outside.

In winter, I flip a lever on the exhaust valve ( top of the last picture) and it blows the nice warm moist exhaust air inside where it should be.
Remember this is an electric dryer, not a gas model, so I do NOTconcern myself with combustion products, ( CO and CO2)

In winterI also disconnect the new intake duct hose.- No need to use cold attic air!

This project might work with sturdy corregated paper-cardboard, foamboard, or corregated plastic board, instead of aluminized bubblepack plastic.
If you only need a vent hose it might cost only $10. to complete the project

I needed 2 lengths of 6 inch diameter hose, to fit the sheet metal vent I already had, and to reach the attic. A 4 inch diameter hose might have been too narrow considering the long run to my attic. I went with the bigger hose.

I also opted to avoid visibly taping the dryer. This gave it a neat clean look.
I went "High end" and used about $30 worth of materials.

Of course I'm not counting the duct tape. Everyone already has duct tape, right?



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    139 Discussions


    10 years ago on Introduction

    I like the idea of piping (otherwise useless) hot air from your loft / attic. But I can't help wondering whether hanging clothes outside on a line is something you just don't do where you live? L

    7 replies

    Reply 9 years ago on Introduction

    My wife and I have started hanging our clothes on a line again. Works great, uses zero energy.


    Reply 2 years ago

    In some places clothes lines are actually banned believe it or not. I know, it is really stupid but, it's true. This 'ible should help mitigate it for some people who live in places where the clothes lines are banned.


    Reply 10 years ago on Introduction

    To be direct, no, most of us here in this residential urban area, do not use clothes lines. I'd need a bigger yard, a pole and co-operation of - nature- the weather, the squirrels birds and trees. Its raining now, and has been for the last 10 days! Dryers are quicker more reliable and require less manual labor. We'd have to carry wet clothes to a place near the line. On our 2nd floor residence, someone would have to hang out a window. It's not a popular option.


    Reply 10 years ago on Introduction

    I see, it wasn't clear where you lived. I make the best efforts to use the free energy available from the sun, but sometimes things stay out for a day 'cos they got rained-on... Thanks for filling us in on that! L


    Reply 10 years ago on Introduction

    Yep. New York. And we got attitude! ha ha. Press a button get it done. Hmm now if there was a way so I didn't have to press the button ... hmmmm


    10 years ago on Introduction

    Great Idea. I live in Florida, and my atticspace turns into a 140 degree dry heat desert environment in the summer. In the winter, it's probably only 85. Putting the intake high in the attic makes sense to get the warmest air, but also because it'll probably be the cleanest air. My home like many, has loose, blown cellulose insulation. Too low, and I'd be pulling this stuff into my clean laundry. I wonder if building the vent shroud out of corrugated plastic sheet would work well. It's sturdy, easy to work with, and should insulate pretty well because of the air space. I'm eyeing up my laundry room right now, trying to determine if i have a straight run to the attic. :) Oh, and vent hose to intake hose (attempt at perpetual motion machine?) wouldn't work, unless you had an inline condenser of some sort. The vent isn't there to exhaust heat, it's there to exhaust the moisture the warm air is evaporating out of your clothes. IF you vented back into the dryer, all the moisture would go there too, and your clothes would never dry. Neat thought though. Once again, great idea.

    7 replies

    Reply 10 years ago on Introduction

    I love it! I think you're onto something. I had considered using foam board, but this might be better. Let me know how it works for you. ( I used the flexible plastic because its flexible, sturdy easy to cut, thin enough to sandwich between the dryer and back panel, waterproof, and most importantly, I already had some. ) The plastic corrugated sheet is sturdy and waterproof easy to cut. (2 Sheets of plastic with corrugated plastic in between.) I think you may be able to create sharp edges by cutting it up to the opposite sheet, and bending it. I'll bet if you measure, plan, sketch on paper, and maybe make a paper scale model, you can plan to make it all in one piece. BUT Is one piece construction necessary? You can gut 5 pieces, Top bottom left & right & back. Tape the seams - ( Both sides ) With Whit duct tape. Tape or attach to dryer. Check to see if your attic has vents. If so run your dryer in the heat of the day, and you'll remove some of the hot air there. Cooler attic, cooler house... You might want to consider a thermostatically controlled attic fan to vent your attic. 140 is HOT ! And as long as the attic temp in winter is greater than in your house, you'll still benefit.

    Marc JensenDrChill

    Reply 7 years ago on Introduction

    I teach classes in sustainable business, and I always use this example as a creative way to approach alternative energy. I live in Oklahoma, and I'm sure my well vented attic hits 140 in the summer too (the outside temperatures were hitting 110 a lot last summer...). So this spring, I'm doing this conversion to my own dryer and I have a question regarding materials. Would there be any kind of fire risk to build the hood out of cardboard rather than plastic sheeting? The air from the attic isn't hot enough to ignite the cardboard, but I don't know about the body of the dryer. Your thoughts?

    DrChillMarc Jensen

    Reply 7 years ago on Introduction

    Another thought. Do remember to avoid gas dryers.
    On your electric dryer, check the temperature at the exhaust and at the locations where your material may come in contact your dryer.
    Run a load and just locate the dryer's hot spots, then consider that in your design ..
    Good luck.

    Marc JensenDrChill

    Reply 7 years ago on Introduction

    Felt for hot spots last night. The back of the unit gets only slightly warm, but the lower left side gets extremely hot, which comes in contact with the edge of the hood. After this, I think I would recommend people to avoid cardboard for this project. It makes me nervous. I'm going to replace that section of my hood with corrugated plastic sheeting, or possibly sheet metal.

    DrChillMarc Jensen

    Reply 7 years ago on Introduction

    Maybe the hot spot can be used as a source of incoming air.
    Maybe create an off-set/space that allows air to flow over the hot spot.
    That way the cardboard does not touch the hot-spot.

    DrChillMarc Jensen

    Reply 7 years ago on Introduction

    I'm delighted that you're putting it to good use.
    I don't think that 140 degrees, will be a fire hazard. And
    The longer the run from the attic to the dryer, the cooler the air will get.
    My dryer doesn't get hot to the touch.
    I believe the main mechanism of drying is constant renewed supply and movement of -relatively dry air- over the tumbling clothes.

    If heat from your attic gets to the dryer, thats great, but do not overlook the value of having the air supply and exhaust that is entirely outside the interior space.

    If you dont exhause the dryer's waste air and humidity, and get the source air from outside the interior conditioned space, you risk bringing in outdoor air inside, or heating the interior space with humid dryer exhaust.
    ("Enthalpy" aka the latent heat in warm humid air.)

    Cardboard. - Glad you asked.
    I recommend going to a big box store to get it. Costco has great sheets - roughly 3x4 ft with 2 layers of corrigation. Its sturdy and a free building material. Sometimes they have lots of it. (Repurposing material !!! )

    Design: The flexible hood lends itself to a curved manifold. But Cardboard is obviously flat, so you might want to consider a rectangular hood that fits around the back- top,sides, and bottom; a much boxier shape than the instructable I made.
    Good luck and please keep me posted. I'd love to hear about real world experience with my invention.

    Marc JensenDrChill

    Reply 7 years ago on Introduction

    Thanks! I help run the cardboard recycling program at OU, so I have plenty of material to work with!

    Yes, I'm going with a rectangular hood design that tapers from 8 inches deep at the top down to about 2 inches deep at the bottom. The dryer that you used in the instructable had a flat back, but mine is much more contoured, so using a more rigid material lets me cut it to fit more precisely and then tape that down.

    I'm really interested in the problem of measurement with this experiment, and I can't just plug the dryer into my Kill-a-Watt. As a classroom example, I want specific numbers to put to this.

    I'll send a photo when it's up and running.


    9 years ago on Step 11

    Living in Missouri, where the summers are hot, but also very humid, I wonder how much longer the dryer would have to run to compensate for using air high in humidity to dry the clothes. Vs. the dryer (!) air-conditioned air.... Would there still be a net energy savings or would the extended run time be a wash?

    1 reply

    Reply 8 years ago on Introduction

    Lots of energy is used to heat air electrically.
    Less energy is used to tumble the clothes.
    Even less energy is used to blow air through the tumbler.

    Unless the air is quite humid, running the dryer without heat will save energy.
    How humid is that? I can't say.

    Maybe your dryer has a listing for energy consumption.

    Lets say the maximum is 1000 watts, and air only uses 400 watts.
    then I'd say if your air only cycle takes twice as long as with heat, then 2*400 watts per cycle is still less than 1000 watts per cycle.

    In practice, my hot attic air on hot humid NYC days, drys clothes in approximately the same time as cool air from my basement when I don't use the air dry cycle.


    9 years ago on Step 11

    Great Energy saving project!  I want to make one.


    9 years ago on Step 11

    Whats wrong with a good ol' close line?  Maybe it rains a lot?  Winters are too cold?